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Sample records for contact problems current

  1. INSTRUMENTS AND METHODS OF INVESTIGATION: Solid-solid thermal contact problems: current understanding

    NASA Astrophysics Data System (ADS)

    Mesnyankin, Sergei Yu; Vikulov, Aleksei G.; Vikulov, Dmitrii G.

    2009-09-01

    The past 40 years of theoretical and experimental research on contact heat transfer are reviewed. Thermophysical and mechanical processes involved in heat flow propagation through various kinds of solid-solid joints are considered. Analytical and semiempirical expressions are presented, which simulate these processes both under vacuum conditions and in the presence of a heat-conducting medium in gaps. Reasons for the experimentally examined heat flux rectification are explained. Studies on thermal contact under a nonstationary regime are covered, as is the possibility of applying classical heat conduction theory to describing the contact thermal properties. A thermodynamic interpretation of the thermal contact resistance is suggested and basic approaches to the study of contact phenomena are described. The heat conduction in nanosystems is briefly reviewed. Theoretical problems yet to be solved are pointed out and possible solution methods suggested.

  2. [Current contact allergens].

    PubMed

    Geier, J; Uter, W; Lessmann, H; Schnuch, A

    2011-10-01

    Ever-changing exposure to contact allergens, partly due to statutory directives (e.g. nickel, chromate, methyldibromo glutaronitrile) or recommendations from industrial associations (e.g. hydroxyisohexyl 3-cyclohexene carboxaldehyde), requires on-going epidemiologic surveillance of contact allergy. In this paper, the current state with special focus in fragrances and preservatives is described on the basis of data of the Information Network of Departments of Dermatology (IVDK) of the year 2010. In 2010, 12,574 patients were patch tested in the dermatology departments belonging to the IVDK. Nickel is still the most frequent contact allergen. However the continuously improved EU nickel directive already has some beneficial effect; sensitization frequency in young women is dropping. In Germany, chromate-reduced cement has been in use now for several years, leading to a decline in chromate sensitization in brick-layers. Two fragrance mixes are part of the German baseline series; they are still relevant. The most important fragrances in these mixes still are oak moss absolute and hydroxyisohexyl 3-cyclohexene carboxaldehyde. However, in relation to these leading allergens, sensitization frequency to other fragrances contained in the mixes seems to be increasing. Among the preservatives, MCI/MI has not lost its importance as contact allergen, in contrast to MDBGN. Sources of MCI/MI sensitization obviously are increasingly found in occupational context. Methylisothiazolinone is a significant allergen in occupational settings, and less frequently in body care products. PMID:21901563

  3. Mixed formulation for frictionless contact problems

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K.; Kim, Kyun O.

    1989-01-01

    Simple mixed finite element models and a computational precedure are presented for the solution of frictionless contact problems. The analytical formulation is based on a form of Reissner's large rotation theory of the structure with the effects of transverse shear deformation included. The contact conditions are incorporated into the formulation by using a perturbed Lagrangian approach with the fundamental unknowns consisting of the internal forces (stress resultants), the generalized displacements, and the Lagrange multipliers associated with the contact conditions. The element characteristic array are obtained by using a modified form of the two-field Hellinger-Reissner mixed variational principle. The internal forces and the Lagrange multipliers are allowed to be discontinuous at interelement boundaries. The Newton-Raphson iterative scheme is used for the solution of the nonlinear algebraic equations, and the determination of the contact area and the contact pressures.

  4. On contact problems of elasticity theory

    NASA Technical Reports Server (NTRS)

    Kalandiya, A. I.

    1986-01-01

    Certain contact problems are reviewed in the two-dimensional theory of elasticity when round bodies touch without friction along most of the boundary and, therefore, Herz' hypothesis on the smallness of the contact area cannot be used. Fundamental equations were derived coinciding externally with the equation in the theory of a finite-span wing with unkown parameter. These equations are solved using Multhopp's well-known technique, and numerical calculations are performed in specific examples.

  5. Current Social Problem Novels.

    ERIC Educational Resources Information Center

    Kenney, Donald J.

    This review of social problem novels for young adults opens with a brief background of the genre, then lists the dominant themes of social problem fiction and nonfiction novels that have been published in the last two years, such as alcoholism, alienation, death, growing up and self-awarness, drugs, and divorce. Other themes mentioned are…

  6. Current indications for scleral contact lenses.

    PubMed

    Foss, A J; Trodd, T C; Dart, J K

    1994-04-01

    Scleral contact lenses have been largely superseded by corneal contact lenses, but they still retain a role as a treatment of choice for a small group of patients who have tried other types of contact lens wear without success and who are not good candidates for surgery. We performed a cross sectional survey of 44 patients attending clinics at Moorfields Eye Hospital who were successful long-term scleral contact lens wearers and reviewed their indications. Twenty-one patients had been fit to improve visual acuity, 20 for therapeutic indications, and three for cosmetic reasons. Scleral lenses were most useful were with patients with ocular surface disorders, such as Stevens-Johnson syndrome, and for visual rehabilitation of patients with grossly irregular corneal topography. All patients were benefiting from scleral contact lens wear, and none had serious complications as a result of the scleral lens wear. We conclude that all ophthalmic departments should have access to these lenses. PMID:8044976

  7. Reduction technique for tire contact problems

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K.; Peters, Jeanne M.

    1995-01-01

    A reduction technique and a computational procedure are presented for predicting the tire contact response and evaluating the sensitivity coefficients of the different response quantities. The sensitivity coefficients measure the sensitivity of the contact response to variations in the geometric and material parameters of the tire. The tire is modeled using a two-dimensional laminated anisotropic shell theory with the effects of variation in geometric and material parameters, transverse shear deformation, and geometric nonlinearities included. The contact conditions are incorporated into the formulation by using a perturbed Lagrangian approach with the fundamental unknowns consisting of the stress resultants, the generalized displacements, and the Lagrange multipliers associated with the contact conditions. The elemental arrays are obtained by using a modified two-field, mixed variational principle. For the application of the reduction technique, the tire finite element model is partitioned into two regions. The first region consists of the nodes that are likely to come in contact with the pavement, and the second region includes all the remaining nodes. The reduction technique is used to significantly reduce the degrees of freedom in the second region. The effectiveness of the computational procedure is demonstrated by a numerical example of the frictionless contact response of the space shuttle nose-gear tire, inflated and pressed against a rigid flat surface.

  8. Electric current induced modification of germanium nanowire NEM switch contact

    NASA Astrophysics Data System (ADS)

    Meija, R.; Kosmaca, J.; Jasulaneca, L.; Petersons, K.; Biswas, S.; Holmes, J. D.; Erts, D.

    2015-05-01

    We present an investigation of contact properties of a germanium (Ge) nanowire based nanoelectromechanical (NEM) switch in its ON state. The contact stiffness in the ON state was evaluated by detecting the nanowire’s resonance frequency. It was found that the resonance frequency increases when electric current flows through the nanowire/counter electrode contact area. The reason for modification in the contact area is referred to as electric-current-induced processes in the native oxide layer covering the nanowires. The presented resonance shift method is a simple way to indicate strengthening of the nanowire/counter electrode contact area without disassembling the contact.

  9. Electric current induced modification of germanium nanowire NEM switch contact.

    PubMed

    Meija, R; Kosmaca, J; Jasulaneca, L; Petersons, K; Biswas, S; Holmes, J D; Erts, D

    2015-05-15

    We present an investigation of contact properties of a germanium (Ge) nanowire based nanoelectromechanical (NEM) switch in its ON state. The contact stiffness in the ON state was evaluated by detecting the nanowire's resonance frequency. It was found that the resonance frequency increases when electric current flows through the nanowire/counter electrode contact area. The reason for modification in the contact area is referred to as electric-current-induced processes in the native oxide layer covering the nanowires. The presented resonance shift method is a simple way to indicate strengthening of the nanowire/counter electrode contact area without disassembling the contact. PMID:25902759

  10. Non-contact current and voltage sensor

    DOEpatents

    Carpenter, Gary D; El-Essawy, Wael; Ferreira, Alexandre Peixoto; Keller, Thomas Walter; Rubio, Juan C; Schappert, Michael A

    2014-03-25

    A detachable current and voltage sensor provides an isolated and convenient device to measure current passing through a conductor such as an AC branch circuit wire, as well as providing an indication of an electrostatic potential on the wire, which can be used to indicate the phase of the voltage on the wire, and optionally a magnitude of the voltage. The device includes a housing that contains the current and voltage sensors, which may be a ferrite cylinder with a hall effect sensor disposed in a gap along the circumference to measure current, or alternative a winding provided through the cylinder along its axis and a capacitive plate or wire disposed adjacent to, or within, the ferrite cylinder to provide the indication of the voltage.

  11. Current contacts and the breakdown of the quantum Hall effect

    NASA Astrophysics Data System (ADS)

    van Son, P. C.; Kruithof, G. H.; Klapwijk, T. M.

    1990-12-01

    The nonlinearities in the I-V characteristics have been studied of high-mobility Si metal oxide semiconductor field-effect transistors in the quantum Hall regime. The breakdown curves were measured with different sets of voltage contacts and for different directions of magnetic field and current. Comparison of these curves shows that the breakdown of the quantum Hall effect (QHE) in these samples is an intrinsic effect that starts at the current contact where the electrons are injected into the two-dimensional electron gas (2DEG). This fundamental asymmetry and the crucial role of the current contact are explained using the Büttiker-Landauer approach to the QHE and its recent extension to the nonlinear regime. The electron-injection process contains two mechanisms that lead to breakdown voltages in the 2DEG. We have identified both experimentally by comparing the critical currents of different configurations of current and voltage contacts. In one of the mechanisms, the nonequilibrium distribution of electrons that is injected into the 2DEG extends to the voltage contacts. This means that the equilibration length of the 2D electrons is at least of the order of 100 μm. For currents far beyond breakdown and for voltage contacts that are further from the electron-injection contact, the breakdown characteristics are harder to understand. The variation of the electron density of the 2DEG due to the large Hall voltage has to be taken into account as well as the equilibration induced by additional voltage contacts.

  12. Thimerosal: current sources of contact in Brazil.

    PubMed

    Rocha, Vanessa Barreto; Scherrer, Maria Antonieta Rios

    2014-01-01

    Thimerosal is an organic mercury derivative found in ophthalmic solutions and certain vaccines in Brazil. Although most studies suggest the prevalence of thimerosal sensitivity to be quite high, this condition does not currently have any clinical relevance. The present article surveyed 184 Brazilian products (151 topical medications and 33 vaccines) and found that thimerosal was only present in 3 ophthalmic solutions and 5 vaccines. PMID:24770530

  13. Solutions of contact problems by the assumed stress hybrid model

    NASA Technical Reports Server (NTRS)

    Kubomura, K.; Pian, T. H. H.

    1980-01-01

    A method was developed for contact problems which may be either frictional or frictionless and may involve extensive sliding between deformable bodies. It was based on an assumed stress hybrid approach and on an incremental variational principle for which the Euler's equations of the functional include the equilibrium and compatibility conditions at the contact surface. The tractions at an assumed contact surface were introduced as Lagrangian multipliers in the formulation. It was concluded from the results of several example solutions that the extensive sliding contact between deformable bodies can be solved by the present method.

  14. Mechanisms of current flow in metal-semiconductor ohmic contacts

    SciTech Connect

    Blank, T. V. Gol'dberg, Yu. A.

    2007-11-15

    Published data on the properties of metal-semiconductor ohmic contacts and mechanisms of current flow in these contacts (thermionic emission, field emission, thermal-field emission, and also current flow through metal shunts) are reviewed. Theoretical dependences of the resistance of an ohmic contact on temperature and the charge-carrier concentration in a semiconductor were compared with experimental data on ohmic contacts to II-VI semiconductors (ZnSe, ZnO), III-V semiconductors (GaN, AlN, InN, GaAs, GaP, InP), Group IV semiconductors (SiC, diamond), and alloys of these semiconductors. In ohmic contacts based on lightly doped semiconductors, the main mechanism of current flow is thermionic emission with the metal-semiconductor potential barrier height equal to 0.1-0.2 eV. In ohmic contacts based on heavily doped semiconductors, the current flow is effected owing to the field emission, while the metal-semiconductor potential barrier height is equal to 0.3-0.5 eV. In alloyed In contacts to GaP and GaN, a mechanism of current flow that is not characteristic of Schottky diodes (current flow through metal shunts formed by deposition of metal atoms onto dislocations or other imperfections in semiconductors) is observed.

  15. Polymer-Metal Schottky Contact with Direct-Current Outputs.

    PubMed

    Shao, Hao; Fang, Jian; Wang, Hongxia; Dai, Liming; Lin, Tong

    2016-02-17

    A freestanding conducting polymer plate with one side forming a Schottky contact and the other side an Ohmic contact with two different metal electrodes can generate a DC voltage with an output current density as high as 218.6 μA cm(-2) upon mechanical deformation. PMID:26639910

  16. High current density contacts for photoconductive semiconductor switches

    SciTech Connect

    Baca, A.G.; Hjalmarson, H.P.; Loubriel, G.M.; McLaughlin, D.L.; Zutavern, F.J.

    1993-08-01

    The current densities implied by current filaments in GaAs photoconductive semiconductor switches (PCSS) are in excess of 1 MA/cm{sup 2}. As the lateral switches are tested repeatedly, damage accumulates at the contacts until electrical breakdown occurs across the surface of the insulating region. In order to improve the switch lifetime, the incorporation of n- and p-type ohmic contacts in lateral switches as well as surface geometry modifications have been investigated. By using p-type AuBe ohmic contacts at the anode and n-type AuGe ohmic contacts at the cathode, contact lifetime improvements of 5--10x were observed compared to switches with n-type contacts at both anode and cathode. Failure analysis on samples operated for 1--1,000 shots show that extensive damage still exists for at least one contact on all switches observed and that temperatures approaching 500{degrees}C are can be reached. However, the n-type AuGe cathode is often found to have no damage observable by scanning electron microscopy (SEM). The observed patterns of contact degradation indicate directions for future contact improvements in lateral switches.

  17. The treatment of contact problems as a non-linear complementarity problem

    SciTech Connect

    Bjorkman, G.

    1994-12-31

    Contact and friction problems are of great importance in many engineering applications, for example in ball bearings, bolted joints, metal forming and also car crashes. In these problems the behavior on the contact surface has a great influence on the overall behavior of the structure. Often problems such as wear and initiation of cracks occur on the contact surface. Contact problems are often described using complementarity conditions, w {>=} 0, p {>=} 0, w{sup T}p = 0, which for example represents the following behavior: (i) two bodies can not penetrate each other, i.e. the gap must be greater than or equal to zero, (ii) the contact pressure is positive and different from zero only if the two bodies are in contact with each other. Here it is shown that by using the theory of non-linear complementarity problems the unilateral behavior of the problem can be treated in a straightforward way. It is shown how solution methods for discretized frictionless contact problem can be formulated. By formulating the problem either as a generalized equation or as a B-differentiable function, it is pointed out how Newton`s method may be extended to contact problems. Also an algorithm for tracing the equilibrium path of frictionless contact problems is described. It is shown that, in addition to the {open_quotes}classical{close_quotes} bifurcation and limit points, there can be points where the equilibrium path has reached an end point or points where bifurcation is possible even if the stiffness matrix is non-singular.

  18. Solving conformal wheel-rail rolling contact problems

    NASA Astrophysics Data System (ADS)

    Vollebregt, Edwin; Segal, Guus

    2014-05-01

    The stresses between railway wheels and rails can be computed using different types of contact models: simplified methods, half-space-based boundary element approaches and finite element models. For conformal contact situations, particularly the contact between flange root and rail gauge corner, none of these models work satisfactorily. Finite element methods are too slow, half-space approaches ignore the effects of conformality, and simplified approaches schematise the elasticity of the material even further. This paper presents a thorough investigation of the conformal wheel-rail rolling contact problem. We use CONTACT's boundary element approach together with numerical influence coefficients, that are computed using the finite element approach. The resulting method is fast and detailed and can be embedded into vehicle system dynamics simulation. The results indicate that the contact area is longer and narrower, with smaller area and reduced stiffness, than is predicted by the half-space approach. The predicted maximum pressures are increased by 30%. Finally the longitudinal and lateral forces changed up to 15% of the Coulomb maximum.

  19. Method and apparatus for producing co-current fluid contact

    DOEpatents

    Trutna, W.R.

    1997-12-09

    An improved packing system and method are disclosed wherein a packing section includes a liquid distributor and a separator placed above the distributor so that gas rising through the liquid distributor contacts liquid in the distributor, forming a gas-liquid combination which rises in co-current flow to the separator. Liquid is collected in the separator, from which gas rises. 13 figs.

  20. Method and apparatus for producing co-current fluid contact

    DOEpatents

    Trutna, William R.

    1997-01-01

    An improved packing system and method are disclosed wherein a packing section includes a liquid distributor and a separator placed above the distributor so that gas rising through the liquid distributor contacts liquid in the distributor, forming a gas-liquid combination which rises in co-current flow to the separator. Liquid is collected in the separator, from which gas rises.

  1. CdS-metal contact at higher current densities.

    NASA Technical Reports Server (NTRS)

    Stirn, R. J.; Boeer, K. W.; Dussel, G. A.

    1973-01-01

    An investigation is conducted concerning the mechanisms by which a steady flow of current proceeds through the contact when an external voltage is applied. The main characteristics of current mechanisms are examined, giving attention to photoemission from the cathode, thermionic emission, minority-carrier extraction, and the tunneling of electrons. A high-field domain analysis is conducted together with experimental studies. Particular attention is given to the range in which tunneling predominates.

  2. A posteriori error estimator and error control for contact problems

    NASA Astrophysics Data System (ADS)

    Weiss, Alexander; Wohlmuth, Barbara I.

    2009-09-01

    In this paper, we consider two error estimators for one-body contact problems. The first error estimator is defined in terms of H( div ) -conforming stress approximations and equilibrated fluxes while the second is a standard edge-based residual error estimator without any modification with respect to the contact. We show reliability and efficiency for both estimators. Moreover, the error is bounded by the first estimator with a constant one plus a higher order data oscillation term plus a term arising from the contact that is shown numerically to be of higher order. The second estimator is used in a control-based AFEM refinement strategy, and the decay of the error in the energy is shown. Several numerical tests demonstrate the performance of both estimators.

  3. Inverse heat transfer problem of thermal contact conductance estimation in periodically contacting surfaces

    NASA Astrophysics Data System (ADS)

    Shojaeefard, M. H.; Goudarzi, K.; Mazidi, M. Sh.

    2009-06-01

    The problems involving periodic contacting surfaces have different practical applications. An inverse heat conduction problem for estimating the periodic Thermal Contact Conductance (TCC) between one-dimensional, constant property contacting solids has been investigated with conjugate gradient method (CGM) of function estimation. This method converges very rapidly and is not so sensitive to the measurement errors. The advantage of the present method is that no a priori information is needed on the variation of the unknown quantities, since the solution automatically determines the functional form over the specified domain. A simple, straight forward technique is utilized to solve the direct, sensitivity and adjoint problems, in order to overcome the difficulties associated with numerical methods. Two general classes of results, the results obtained by applying inexact simulated measured data and the results obtained by using data taken from an actual experiment are presented. In addition, extrapolation method is applied to obtain actual results. Generally, the present method effectively improves the exact TCC when exact and inexact simulated measurements input to the analysis. Furthermore, the results obtained with CGM and the extrapolation results are in agreement and the little deviations can be negligible.

  4. Single Nanoparticle Voltammetry: Contact Modulation of the Mediated Current.

    PubMed

    Li, Xiuting; Batchelor-McAuley, Christopher; Whitby, Samuel A I; Tschulik, Kristina; Shao, Lidong; Compton, Richard G

    2016-03-18

    The cyclic voltammetric responses of individual palladium-coated carbon nanotubes are reported. Upon impact-from the solution phase-with the electrified interface, the nanoparticles act as individual nanoelectrodes catalyzing the hydrogen-oxidation reaction. At high overpotentials the current is shown to reach a quasi-steady-state diffusion limit, allowing determination of the tube length. The electrochemical response of the individual nanotubes also reveals the system to be modulated by the electrical contact between the electrode and carbon nanotube. This modulation presents itself as fluctuations in the recorded Faradaic current. PMID:26515036

  5. Non-Contact EDDY Current Hole Eccentricity and Diameter Measurement

    NASA Technical Reports Server (NTRS)

    Chern, E. James

    1998-01-01

    Precision holes are among the most critical features of a mechanical component. Deviations from permissible tolerances can impede operation and result in unexpected failure. We have developed an automated non-contact eddy current hole diameter and eccentricity measuring system. The operating principle is based on the eddy current lift-off effect, which is the coil impedance as a function of the distance between the coil and the test object. An absolute eddy current probe rotates in the hole. The impedance of each angular position is acquired and input to the computer for integration and analysis. The eccentricity of the hole is the profile of the impedance as a function of angular position as compared to a straight line, an ideal hole. The diameter of the hole is the sum of the diameter of the probe and twice the distance-calibrated impedance. An eddy current image is generated by integrating angular scans for a plurality of depths between the top and bottom to display the eccentricity profile. This system can also detect and image defects in the hole. The method for non-contact eddy current hole diameter and eccentricity measurement has been granted a patent by the U.S. Patent and Trademark Office.

  6. Teaching Tips on Current Environmental Problems.

    ERIC Educational Resources Information Center

    Busch, Phyllis S.

    This manual, prepared by the Science Project Related to Upgrading Conservation Education (Project S.P.R.U.C.E.), contains suggestions for introducing elementary school students to current environmental problems. Problems treated are population density, social pollution, visual pollution, air pollution, and water pollution. A background discussion…

  7. Current-induced dynamics in carbon atomic contacts

    PubMed Central

    Gunst, Tue

    2011-01-01

    Summary Background: The effect of electric current on the motion of atoms still poses many questions, and several mechanisms are at play. Recently there has been focus on the importance of the current-induced nonconservative forces (NC) and Berry-phase derived forces (BP) with respect to the stability of molecular-scale contacts. Systems based on molecules bridging electrically gated graphene electrodes may offer an interesting test-bed for these effects. Results: We employ a semi-classical Langevin approach in combination with DFT calculations to study the current-induced vibrational dynamics of an atomic carbon chain connecting electrically gated graphene electrodes. This illustrates how the device stability can be predicted solely from the modes obtained from the Langevin equation, including the current-induced forces. We point out that the gate offers control of the current, independent of the bias voltage, which can be used to explore current-induced vibrational instabilities due the NC/BP forces. Furthermore, using tight-binding and the Brenner potential we illustrate how Langevin-type molecular-dynamics calculations including the Joule heating effect for the carbon-chain systems can be performed. Molecular dynamics including current-induced forces enables an energy redistribution mechanism among the modes, mediated by anharmonic interactions, which is found to be vital in the description of the electrical heating. Conclusion: We have developed a semiclassical Langevin equation approach that can be used to explore current-induced dynamics and instabilities. We find instabilities at experimentally relevant bias and gate voltages for the carbon-chain system. PMID:22259765

  8. Comparison between FEBio and Abaqus for biphasic contact problems.

    PubMed

    Meng, Qingen; Jin, Zhongmin; Fisher, John; Wilcox, Ruth

    2013-09-01

    Articular cartilage plays an important role in the function of diarthrodial joints. Computational methods have been used to study the biphasic mechanics of cartilage, and Abaqus has been one of the most widely used commercial software packages for this purpose. A newly developed open-source finite element solver, FEBio, has been developed specifically for biomechanical applications. The aim of this study was to undertake a direct comparison between FEBio and Abaqus for some practical contact problems involving cartilage. Three model types, representing a porous flat-ended indentation test, a spherical-ended indentation test, and a conceptual natural joint contact model, were compared. In addition, a parameter sensitivity study was also performed for the spherical-ended indentation test to investigate the effects of changes in the input material properties on the model outputs, using both FEBio and Abaqus. Excellent agreement was found between FEBio and Abaqus for all of the model types and across the range of material properties that were investigated. PMID:23804955

  9. Comparison between FEBio and Abaqus for biphasic contact problems

    PubMed Central

    Jin, Zhongmin; Fisher, John; Wilcox, Ruth

    2013-01-01

    Articular cartilage plays an important role in the function of diarthrodial joints. Computational methods have been used to study the biphasic mechanics of cartilage, and Abaqus has been one of the most widely used commercial software packages for this purpose. A newly developed open-source finite element solver, FEBio, has been developed specifically for biomechanical applications. The aim of this study was to undertake a direct comparison between FEBio and Abaqus for some practical contact problems involving cartilage. Three model types, representing a porous flat-ended indentation test, a spherical-ended indentation test, and a conceptual natural joint contact model, were compared. In addition, a parameter sensitivity study was also performed for the spherical-ended indentation test to investigate the effects of changes in the input material properties on the model outputs, using both FEBio and Abaqus. Excellent agreement was found between FEBio and Abaqus for all of the model types and across the range of material properties that were investigated. PMID:23804955

  10. Exact Null Controllability of a Nonlinear Thermoelastic Contact Problem

    SciTech Connect

    Sivergina, Irina F. Polis, Michael P.

    2005-01-15

    We study the controllability properties of a nonlinear parabolic system that models the temperature evolution of a one-dimensional thermoelastic rod that may come into contact with a rigid obstacle. Basically the system dynamics is described by a one-dimensional nonlocal heat equation with a nonlinear and nonlocal boundary condition of Newmann type.We focus on the control problem and treat the case when the control is distributed over the whole space domain. In this case the system is proved to be exactly null controllable provided the parameters of the system are smooth.The proof is based on changing the control variable and using Aubin's Compactness Lemma to obtain an invariant set for the linearized controllability map. Then, by proving that the found solution is sufficiently smooth, we get the null controllability for the original system.

  11. Conference on Current Problems in College Administration.

    ERIC Educational Resources Information Center

    Nossell, Jerome, Ed.; Pesci, Frank B., Ed.

    The purpose of the 10-day Conference on Current Problems in College Administration were: (1) to improve the effectiveness and efficiency of the administrative services of Saint Joseph College; (2) to identify the principal areas toward which the College should direct future efforts for improvement; (3) to place the administrative staff in contact…

  12. Variationally consistent discretization schemes and numerical algorithms for contact problems

    NASA Astrophysics Data System (ADS)

    Wohlmuth, Barbara

    We consider variationally consistent discretization schemes for mechanical contact problems. Most of the results can also be applied to other variational inequalities, such as those for phase transition problems in porous media, for plasticity or for option pricing applications from finance. The starting point is to weakly incorporate the constraint into the setting and to reformulate the inequality in the displacement in terms of a saddle-point problem. Here, the Lagrange multiplier represents the surface forces, and the constraints are restricted to the boundary of the simulation domain. Having a uniform inf-sup bound, one can then establish optimal low-order a priori convergence rates for the discretization error in the primal and dual variables. In addition to the abstract framework of linear saddle-point theory, complementarity terms have to be taken into account. The resulting inequality system is solved by rewriting it equivalently by means of the non-linear complementarity function as a system of equations. Although it is not differentiable in the classical sense, semi-smooth Newton methods, yielding super-linear convergence rates, can be applied and easily implemented in terms of a primal-dual active set strategy. Quite often the solution of contact problems has a low regularity, and the efficiency of the approach can be improved by using adaptive refinement techniques. Different standard types, such as residual- and equilibrated-based a posteriori error estimators, can be designed based on the interpretation of the dual variable as Neumann boundary condition. For the fully dynamic setting it is of interest to apply energy-preserving time-integration schemes. However, the differential algebraic character of the system can result in high oscillations if standard methods are applied. A possible remedy is to modify the fully discretized system by a local redistribution of the mass. Numerical results in two and three dimensions illustrate the wide range of

  13. AIRBORNE CONTACT DERMATITIS – CURRENT PERSPECTIVES IN ETIOPATHOGENESIS AND MANAGEMENT

    PubMed Central

    Handa, Sanjeev; De, Dipankar; Mahajan, Rahul

    2011-01-01

    The increasing recognition of occupational origin of airborne contact dermatitis has brought the focus on the variety of irritants, which can present with this typical morphological picture. At the same time, airborne allergic contact dermatitis secondary to plant antigens, especially to Compositae family, continues to be rampant in many parts of the world, especially in the Indian subcontinent. The recognition of the contactant may be difficult to ascertain and the treatment may be even more difficult. The present review focuses on the epidemiological, clinical and therapeutic issues in airborne contact dermatitis. PMID:22345774

  14. Contact allergic dermatitis "current topic in tropical dermatology".

    PubMed

    Soyinka, F

    1978-11-01

    Out of a total of 2,666 new dermatology patients, 128 (4.8%) were clinically diagnosed as allergic contact dermatitis. Of these, 107 (4%) reacted positively to different antigens in the patch-test. The commonest contact sensitizers among females were nickel and dyes. Among male patients, the commonest sensitizers were mecaptobenzol-thiazole, chrome and nickel. The incidence of occupational contact dermatitis among bricklayers, construction workers and builders were found to be low and the sensitization rate against chromate was 0.6%. There was no sensitization against cobalt and nickel in the group, however, the length of occupational contact with cement among these group was short. Allergic contact dermatitis is not as uncommon among the Nigeria populace as is generally believed. It seems to be on the increase especially with increase rate of industrialization. PMID:753055

  15. Advances in reduction techniques for tire contact problems

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K.

    1995-01-01

    Some recent developments in reduction techniques, as applied to predicting the tire contact response and evaluating the sensitivity coefficients of the different response quantities, are reviewed. The sensitivity coefficients measure the sensitivity of the contact response to variations in the geometric and material parameters of the tire. The tire is modeled using a two-dimensional laminated anisotropic shell theory with the effects of variation in geometric and material parameters, transverse shear deformation, and geometric nonlinearities included. The contact conditions are incorporated into the formulation by using a perturbed Lagrangian approach with the fundamental unknowns consisting of the stress resultants, the generalized displacements, and the Lagrange multipliers associated with the contact conditions. The elemental arrays are obtained by using a modified two-field, mixed variational principle. For the application of reduction techniques, the tire finite element model is partitioned into two regions. The first region consists of the nodes that are likely to come in contact with the pavement, and the second region includes all the remaining nodes. The reduction technique is used to significantly reduce the degrees of freedom in the second region. The effectiveness of the computational procedure is demonstrated by a numerical example of the frictionless contact response of the space shuttle nose-gear tire, inflated and pressed against a rigid flat surface. Also, the research topics which have high potential for enhancing the effectiveness of reduction techniques are outlined.

  16. The steady-state tangential contact problem for a falling drop type of contact area on corrugated rail by simplified theory of rolling contact

    NASA Astrophysics Data System (ADS)

    Piotrowski, Jerzy

    1991-10-01

    Investigation of contact mechanical nonlinearities of a mathematical model of corrugation revealed that the typical shape of contact patch resembles a falling drop of water. A contact patch of that shape was approximated with a figure composed of two parts of ellipses with different eccentricities. The contact pressure distribution was assumed as a smoothing ensemble of two paraboloidal distributions. The description of a general case of double half elliptical contact area was given but a special case of double half elliptical contact is more interesting as it possesses some Hertzian properties. It was shown how three geometrical parameters of double half elliptical contact can be chosen when actual, non-Hertzian contact is known. A linear theory was written which indicates that the lateral vibrations of the rail may be excited only due to shape variation on corrugation even if any other cause for these vibrations does not exist. For nonlinear theory a computer program, based on FASTSIM algorithm by Kalker, was written. The aim is to calculate the creep forces and frictional power density distribution over the contact area. Also, a graphic program visualizing the solution was written. Numerical results are not provided; unattended and unsolved problems relevant for this type of contact are listed.

  17. Current problems in plasma spray processing

    SciTech Connect

    Berndt, C.C.; Brindley, W.; Goland, A.N.; Herman, H.; Houck, D.L.; Jones, K.; Miller, R.A.; Neiser, R.; Riggs, W.; Sampath, S.; Smith, M.; Spanne, P.

    1991-12-31

    This detailed report summarizes 8 contributions from a thermal spray conference that was held in late 1991 at Brookhaven National Laboratory (Upton, Long Island, NY, USA). The subject of ``Plasma Spray Processing`` is presented under subject headings of Plasma-particle interactions, Deposit formation dynamics, Thermal properties of thermal barrier coatings, Mechanical properties of coatings, Feed stock materials, Porosity: An integrated approach, Manufacture of intermetallic coatings, and Synchrotron x-ray microtomographic methods for thermal spray materials. Each section is intended to present a concise statement of a specific practical and/or scientific problem, then describe current work that is being performed to investigate this area, and finally to suggest areas of research that may be fertile for future activity.

  18. Current problems in plasma spray processing

    SciTech Connect

    Berndt, C.C.; Brindley, W.; Goland, A.N.; Herman, H.; Houck, D.L.; Jones, K.; Miller, R.A.; Neiser, R.; Riggs, W.; Sampath, S.; Smith, M.; Spanne, P. . Thermal Spray Lab.)

    1991-01-01

    This detailed report summarizes 8 contributions from a thermal spray conference that was held in late 1991 at Brookhaven National Laboratory (Upton, Long Island, NY, USA). The subject of Plasma Spray Processing'' is presented under subject headings of Plasma-particle interactions, Deposit formation dynamics, Thermal properties of thermal barrier coatings, Mechanical properties of coatings, Feed stock materials, Porosity: An integrated approach, Manufacture of intermetallic coatings, and Synchrotron x-ray microtomographic methods for thermal spray materials. Each section is intended to present a concise statement of a specific practical and/or scientific problem, then describe current work that is being performed to investigate this area, and finally to suggest areas of research that may be fertile for future activity.

  19. Transient analysis of thermoelastic contact problem of disk brakes

    NASA Astrophysics Data System (ADS)

    Belhocine, Ali; Bouchetara, Mostefa

    2013-06-01

    The main purpose of this study is to analyze the thermomechanical behavior of the dry contact between the brake disk and pads during the braking phase. The simulation strategy is based on computer code ANSYS11. The modeling of transient temperature in the disk is actually used to identify the factor of geometric design of the disk to install the ventilation system in vehicles. The thermal-structural analysis is then used with coupling to determine the deformation established and the Von Mises stresses in the disk, the contact pressure distribution in pads. The results are satisfactory compared to those found in the literature.

  20. Problem Perception in Ascertainment Surveys and Voluntary Contact With the Broadcast Media.

    ERIC Educational Resources Information Center

    LeRoy, David J.; Ungurait, Donald F.

    A total of 431 households in Tallahassee, Florida, were contacted to ascertain community perceptions of social policy issues, as required of television stations applying for license renewal. It was found that 10 percent of those contacted could think of no problems; 14 percent could not name a national problem, and 35 percent could not name a…

  1. Solution of dynamic contact problems by implicit/explicit methods. Final report

    SciTech Connect

    Salveson, M.W.; Taylor, R.L.

    1996-10-14

    The solution of dynamic contact problems within an explicit finite element program such as the LLNL DYNA programs is addressed in the report. The approach is to represent the solution for the deformation of bodies using the explicit algorithm but to solve the contact part of the problem using an implicit approach. Thus, the contact conditions at the next solution state are considered when computing the acceleration state for each explicit time step.

  2. Modulation in current density of metal/n-SiC contact by inserting Al2O3 interfacial layer

    PubMed Central

    2013-01-01

    Metal contact to SiC is not easy to modulate since the contact can be influenced by the metal, the termination of the SiC, the doping, and the fabrication process. In this work, we introduce a method by inserting a thin Al2O3 layer between metal and SiC to solve this problem simply but effectively. The Al2O3/n-SiC interface composition was obtained with X-ray photoemission spectroscopy, and the electrical properties of subsequently deposited metal contacts were characterized by current–voltage method. We can clearly demonstrate that the insertion of Al2O3 interfacial layer can modulate the current density effectively and realize the transfer between the Schottky contact and ohmic contact. PMID:23452618

  3. Health problems have come in wake of contact with chemicals.

    PubMed

    Davies, Tarnia

    2016-05-25

    As a result of working with the chemicals glutaraldehyde and formaldehyde as a theatre nurse some years ago, I believe that I have suffered numerous health problems that resulted in my retirement. PMID:27224623

  4. Analysis of current crowding in thin film contacts from exact field solution

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Y Lau, Y.; Gilgenbach, R. M.

    2015-12-01

    The paper presents a systematic evaluation of current crowding and spreading resistance in thin film contacts, based on the exact field solution that contains very large contrasts in dimensions and resistivity. It is found that current crowding becomes more severe as the interface specific contact resistivity decreases, the resistivity ratio of the contact electrode to the thin film decreases, or the thickness of either the contact or the thin film decreases. The current transfer length {{L}\\text{T}} from our exact field solution is compared to that of transmission line model (TLM), {{L}\\text{TLM}}={≤ft({{ρ\\text{c}}/{ρ\\text{sh}}\\right)}1}/2 , where {ρ\\text{c}} is the interface specific contact resistivity, and ρ sh is the sheet resistance of the thin film under contact. It is found that, if {ρ\\text{c}} is small, {{L}\\text{T}} is bounded by the smaller of the two dimensions—thin film thickness and contact size. As {ρ\\text{c}} increases, {{L}\\text{T}} increases, but saturates at a constant value, determined by the smaller of the two dimensions—contact size and {{L}\\text{TLM}} . The total contact resistance is decomposed into three components: the interface resistance due to {ρ\\text{c}} , the spreading resistance due to current crowding, and the resistance due to the contact electrode. Unambiguously identified, each component is explicitly evaluated and compared in detail.

  5. On the 3D normal tire/off-road vibro-contact problem with friction

    NASA Astrophysics Data System (ADS)

    Munteanu, Ligia; Chiroiu, Veturia; Brişan, Cornel; Dumitriu, Dan; Sireteanu, Tudor; Petre, Simona

    2015-03-01

    In this paper, a virtual experiment concerning driving on off-roads is investigated via 3D normal vibro-contact problem with friction. The dynamic road concept is introduced in order to characterize a particular stretch of road by total longitudinal, lateral, and normal forces and their geometric distributions in the contact patches. The off-road profiles are built by image sonification technique. The cross-sectional curves of off-roads before and after deformation, the contact between the tire and the road, the distribution of contact and friction forces in the contact domain, the natural frequencies and modes when the tire is in ground contact, are estimated. The approach is exercised on two particular problems and results compare favorably to existing analytical and numerical solutions. The feasibility of image sonification technique is useful to build a low-cost virtual reality environment with an increased degree of realism for driving simulators and higher user flexibility.

  6. Effect of contact space charge on current ratings of cryogenic silicon photoconductive switches

    NASA Astrophysics Data System (ADS)

    Petr, Rodney A.; Reilly, James P.; Schaefer, Raymond B.; Kachen, George I.

    1992-05-01

    Under ideal conditions photoconductive switches utilizing ohmic contacts can be made to conduct high currents that scale directly with input optical trigger power. In practice, however, ohmic contacts can only be approximated by using heavily-doped contact/metallization regions, so that photoswitch structures employing intrinsic substrate layers to support switch voltage can be viewed as n-i-n, p-i-n, or p-i-n, depending on the contact doping. Under bias, these contacts preferentially inject majority carriers (either holes or electrons) into the substrate that can form high local space charge electric fields at elevated current densities. In this paper we show both experimentally and analytically that contact space charge formation in a cryogenic silicon n-i-n photoswitch structure ultimately limits its on-state current capability.

  7. Current Problems of Historical-Pedagogical Research.

    ERIC Educational Resources Information Center

    Ravkin, Z. I.

    1995-01-01

    Maintains that contemporary Russian historical research, particularly educational history research, faces complex problems. Asserts that this is a result of the transition from one dominant methodology and world view to pluralistic approaches. Argues that the methodological potential of Marxist teachings is far from exhausted. (CFR)

  8. A system-approach to the elastohydrodynamic lubrication point-contact problem

    NASA Technical Reports Server (NTRS)

    Lim, Sang Gyu; Brewe, David E.

    1991-01-01

    The classical EHL (elastohydrodynamic lubrication) point contact problem is solved using a new system-approach, similar to that introduced by Houpert and Hamrock for the line-contact problem. Introducing a body-fitted coordinate system, the troublesome free-boundary is transformed to a fixed domain. The Newton-Raphson method can then be used to determine the pressure distribution and the cavitation boundary subject to the Reynolds boundary condition. This method provides an efficient and rigorous way of solving the EHL point contact problem with the aid of a supercomputer and a promising method to deal with the transient EHL point contact problem. A typical pressure distribution and film thickness profile are presented and the minimum film thicknesses are compared with the solution of Hamrock and Dowson. The details of the cavitation boundaries for various operating parameters are discussed.

  9. [Current problems in pediatric ophthalmologic oncology].

    PubMed

    Krásný, J; Koutecký, J; Mottl, H

    1991-09-01

    The authors give an account of contemporary problems of child ophthalmological oncology from the paediatrician's aspect. The most serious intraocular tumors are retinoblastomas, in the orbitopalpebral area rhabdomyosarcomas. The authors draw attention to the five main alarming symptoms typical for tumorous processes at these sites: red painful eye, leukokoria, acute visual failure, acute strabism and various rapidly developing protrusions of the bulbus. Subsequently they inform on possible ophthalmological complications of comprehensive oncological treatment. PMID:1751981

  10. Current noise in three-terminal hybrid quantum point contacts.

    PubMed

    Wu, B H; Wang, C R; Chen, X S; Xu, G J

    2014-01-15

    We investigate the current noise of three-terminal hybrid structures at arbitrary bias voltages. Our results indicate that the noise can be a useful tool to extract dynamical information in multi-terminal hybrid structures. The zero-frequency noise is sensitive to the coupling with a normal lead. As a result, the characteristic multiple-step structure of the noise Fano factor due to multiple Andreev reflection will be suppressed as we increase this coupling. In addition, the internal dynamics due to processes of Andreev reflection and multiple Andreev reflection raises rich features in the noise spectrum corresponding to the energy differences of various dynamical processes. PMID:24305057

  11. Current structural vibration problems associated with noise

    NASA Technical Reports Server (NTRS)

    Mixson, J. S.

    1974-01-01

    As the performance of aerospace vehicles has increased, the noise generated by the propulsion system and by the passage of the vehicle through the air has also increased. Further increases in performance are now underway for space vehicles such as the space shuttle vehicle and for short distance takeoff and landing (STOL) aircraft, and are being planned for supersonic aircraft. The flight profiles and design features of these high-performance vehicles are reviewed and an estimate made of selected noise-induced structural vibration problems. Considerations for the prevention of acoustic fatigue, noise transmission, and electronic instrument malfunction are discussed.

  12. [PEDICULOSIS: CURRENT ASPECTS OF THE OLD PROBLEM].

    PubMed

    Lopatina, Yu V

    2015-01-01

    Analysis of data on the incidence of pediculosis worldwide has shown that this disease still remains one of the major health problems in many countries. The ways of transmitting lice and different (social and biological) factors influencing lice infestation are considered. The country's real morbidity rate, such as the ratio of the number of reported pediculosis cases to the amount of pediculicides sold at drugstores in both Russia as a whole and its individual federal districts in particular, has been investigated. The actual morbidity rate has been found to be higher than the officially recorded one. PMID:26152040

  13. Field effects of current crowding in metal-MoS2 contacts

    NASA Astrophysics Data System (ADS)

    Yuan, Hui; Cheng, Guangjun; Yu, Sheng; Hight Walker, Angela R.; Richter, Curt A.; Pan, Minghu; Li, Qiliang

    2016-03-01

    Gate assisted contact-end Kelvin test structures and gate assisted four-probe structures have been designed and fabricated to measure the field effects of current crowding at the source/drain contacts of top-gate MoS2 field effect transistors. The transistors exhibited n-type transistor characteristics. The source/drain contact resistance was measured by using both gate-assisted Kelvin and gate-assisted four-probe structures. The values of contact resistance measured by these two test structures are significantly different. The contact-front contact resistance obtained from the four-probe structure is strongly influenced by field effects on current crowding, while the contact-end resistance obtained from the Kelvin test structure is not. The metal-MoS2 contact current transfer length, LT, can be determined from the comparison between these two measurements. LT was observed to increase linearly with increasing gate voltage. This work indicates that the contact characteristics can be more precisely measured when both gate-assisted test structures are used.

  14. Coulomb frictional contact by explicit projection in the cone for finite displacement quasi-static problems

    NASA Astrophysics Data System (ADS)

    Areias, P.; Rabczuk, T.; de Melo, F. J. M. Queirós; de Sá, J. César

    2015-01-01

    We propose, in this paper, a distinct perspective on the solution of the Coulomb frictional contact problem. By combining the prediction/correction method for the contact force vector with the correction step being a cone projection and writing the friction cone surface in the quadratic form, we directly calculate the contact force. The distance along the friction cone normal is determined by solving a nonlinear problem in closed form. Numerical advantages of this projection are apparent for large values of friction coefficient. Six problems previously indicated as difficult to solve by the node-to-segment discretization and the operator split algorithm are here solved with the new projection algorithm. Discretization follows node-to segment and node-to-face derivations with gap vector defined in a global frame (without tangential and normal decomposition). In addition, we provide source codes for the 2D and 3D contact cases.

  15. [Current problems in pediatric bone marrow transplantation].

    PubMed

    Kato, S

    1993-05-01

    Bone marrow transplantation (BMT) has been increasingly applied to a variety of potentially fatal diseases in childhood. However, trends of indication of BMT are changing because chemotherapy in leukemia and immunosuppressive therapy with/without colony stimulating factor in aplastic anemia are improving. Several progresses have been noted in matched unrelated BMT and peripheral blood stem cell transplantation as well as in sibling BMT or autologous BMT. Many efforts are being made to decrease rejection rate or leukemia relapse and to improve quality of life by new conditioning regimens. Attempts to induce GVL effects or syngeneic GVHD are currently under progress. The quality of life in long term surviving children are generally good and acceptable, although delay in growth, infertility, cataract and obstructive lung disease are seen in a few patients. PMID:8315825

  16. Tunneling current of the contact between impurity-containing graphene nanoribbons

    SciTech Connect

    Belonenko, M. B.; Pak, A. V. Lebedev, N. G.

    2013-05-15

    The current-voltage characteristics of a tunneling contact between two graphene nanoribbons containing impurity atoms are obtained based on the previously calculated density of states. The dependences on the nanoribbon geometrical and energy characteristics are calculated.

  17. THE CURRENT PROBLEMS OF NONSPECIFIC BACK PAIN.

    PubMed

    Seleznova, S; Zabara, A; Mamuladze, D

    2016-01-01

    The article deals with various aspects of pain in degenerative diseases of the spine and with the actual problems of non-specific back pain. The data on the mechanisms of pain and analgesic treatment algorithms of the patients with radicular syndrome, and pharmacological and non-pharmacological therapies is provided. The effect of structural-modifying drugs in relief of nonspecific back pain was investigated and compared with a traditional nonsteroidal anti-inflammatory drug (NSAID) therapy in combination with B vitamins, without chondroprotectors. The study population was composed of 85 patients (42 men and 43 women) aged 38 to 68 years (mean age - (46,3±2,6) years) with chronic vertebral pain syndromes (VPS). For objectification assessment of pain, severity of pain, and evaluate the effectiveness of therapy we used the visual analog scale (VAS).The majority (88%) of the patients included in the study, complained of a moderately severe pain (from 40 to 70 mm on the VAS). Patients were divided into two groups. The first (primary) group consisted of 55 patients (30 men and 25 women). The following treatment was applied: all patients of the first group, in addition to the NSAID administered with hondroprotektror arbitrarily - Struktum 1000 mg twice a day or 300 mg Piaskledin once a day for 40-60 days.The second (control) group consisted of 30 patients (14 men, 16 women). Patients in the control group administered with a traditional NSAID therapy in combination with B vitamins, without chondroprotectors. The results of the study on the influence of drugs Piaskledin 300, Struktum for the relief of nonspecific back pain revealed that in the treatment of vertebral pain, a combination of non-steroidal anti-inflammatory drugs with structure-modifying agents could achieve rapid rehabilitation of patients with locomotor activity and improve quality of life in general. PMID:26870977

  18. Serious Emotional and Behavioral Problems and Mental Health Contacts in American and British Children and Adolescents

    ERIC Educational Resources Information Center

    Mojtabai, Ramin

    2006-01-01

    Objective: To compare prevalence of serious emotional and behavioral problems and mental health contacts for these problems among American and British children and adolescents. Method: Data on children and adolescents ages 5 to 16 years were drawn from the 2004 U.S. National Health Interview Survey (response rate = 79.4%) and the 2004 survey of…

  19. Switch contact device for interrupting high current, high voltage, AC and DC circuits

    DOEpatents

    Via, Lester C.; Witherspoon, F. Douglas; Ryan, John M.

    2005-01-04

    A high voltage switch contact structure capable of interrupting high voltage, high current AC and DC circuits. The contact structure confines the arc created when contacts open to the thin area between two insulating surfaces in intimate contact. This forces the arc into the shape of a thin sheet which loses heat energy far more rapidly than an arc column having a circular cross-section. These high heat losses require a dramatic increase in the voltage required to maintain the arc, thus extinguishing it when the required voltage exceeds the available voltage. The arc extinguishing process with this invention is not dependent on the occurrence of a current zero crossing and, consequently, is capable of rapidly interrupting both AC and DC circuits. The contact structure achieves its high performance without the use of sulfur hexafluoride.

  20. Outcomes of Treatment for Alcohol Problems: Current Methods, Problems, and Results.

    ERIC Educational Resources Information Center

    Nathan, Peter E.; Skinstad, Anne-Helene

    1987-01-01

    Discusses current methods, problems, and results of psychological treatment for alcohol abuse, including alcoholism. Addresses external and internal validity problems specific to issues regarding who is treated for alcohol problems, and treatment and patient factors that predict response to alcoholism treatment. Reviews current data on…

  1. Spin current source based on a quantum point contact with local spin-orbit interaction

    SciTech Connect

    Nowak, M. P.; Szafran, B.

    2013-11-11

    Proposal for construction of a source of spin-polarized current based on quantum point contact (QPC) with local spin-orbit interaction is presented. We show that spin-orbit interaction present within the narrowing acts like a spin filter. The spin polarization of the current is discussed as a function of the Fermi energy and the width of the QPC.

  2. A thermal, thermoelastic, and wear simulation of a high-energy sliding contact problem

    NASA Technical Reports Server (NTRS)

    Kennedy, F. E., Jr.; Ling, F. F.

    1973-01-01

    This paper describes an investigation of the sliding contact problem encountered in high-energy disk brakes. The analysis includes a simulation modeling, using the finite element method, of the thermoelastic instabilities that cause transient changes in contact to occur on the friction surface. In order to include the effect of wear of the concentrated contacts on the friction surface, a wear criterion is proposed that results in prediction of wear rates for disk brakes that are quite close to experimentally determined wear rates. The thermal analysis shows that the transient temperature distribution in a disk brake can be determined more accurately by use of this thermomechanical analysis than by a more conventional analysis that assumes constant contact conditions. It is also shown that lower, more desirable, temperatures in disk brakes can be attained by increasing the volume, the thermal conductivity, and especially, the heat capacity of the brake components.

  3. A constitutive law for finite element contact problems with unclassical friction

    NASA Technical Reports Server (NTRS)

    Plesha, M. E.; Steinetz, B. M.

    1986-01-01

    Techniques for modeling complex, unclassical contact-friction problems arising in solid and structural mechanics are discussed. A constitutive modeling concept is employed whereby analytic relations between increments of contact surface stress (i.e., traction) and contact surface deformation (i.e., relative displacement) are developed. Because of the incremental form of these relations, they are valid for arbitrary load-deformation histories. The motivation for the development of such a constitutive law is that more realistic friction idealizations can be implemented in finite element analysis software in a consistent, straightforward manner. Of particular interest is modeling of two-body (i.e., unlubricated) metal-metal, ceramic-ceramic, and metal-ceramic contact. Interfaces involving ceramics are of engineering importance and are being considered for advanced turbine engines in which higher temperature materials offer potential for higher engine fuel efficiency.

  4. Non-steady state modelling of wheel-rail contact problem

    NASA Astrophysics Data System (ADS)

    Guiral, A.; Alonso, A.; Baeza, L.; Giménez, J. G.

    2013-01-01

    Among all the algorithms to solve the wheel-rail contact problem, Kalker's FastSim has become the most useful computation tool since it combines a low computational cost and enough precision for most of the typical railway dynamics problems. However, some types of dynamic problems require the use of a non-steady state analysis. Alonso and Giménez developed a non-stationary method based on FastSim, which provides both, sufficiently accurate results and a low computational cost. However, it presents some limitations; the method is developed for one time-dependent creepage and its accuracy for varying normal forces has not been checked. This article presents the required changes in order to deal with both problems and compares its results with those given by Kalker's Variational Method for rolling contact.

  5. Leakage current in high-purity germanium detectors with amorphous semiconductor contacts

    NASA Astrophysics Data System (ADS)

    Looker, Q.; Amman, M.; Vetter, K.

    2015-03-01

    Amorphous semiconductor electrical contacts on high-purity Ge radiation detectors have become a valuable technology because they are simple to fabricate, result in thin dead layers, block both electron and hole injection, and can readily be finely segmented as needed for applications requiring imaging or particle tracking. Though significant numbers of detectors have been successfully produced for a variety of applications using the amorphous semiconductor contact technology, there remains a need to better understand the dependence of performance characteristics, particularly leakage current, on the fabrication process parameters so that the performance can be better optimized. To this end, we have performed a systematic study of leakage current on RF-sputter-deposited amorphous-Ge (a-Ge) and amorphous-Si (a-Si) contacts as a function of process and operational parameters including sputter gas pressure and composition, number of detector temperature cycles, and time spent at room temperature. The study focused primarily on the current resulting from electron injection at the contact. Significant findings from the study include that a-Si produces lower electron injection than a-Ge, the time the detector spends at room temperature rather than the number of temperature cycles experienced by the detector is the primary factor associated with leakage current change when the detector is warmed, and the time stability of the a-Ge contact depends on the sputter gas pressure with a higher pressure producing more stable characteristics.

  6. The JKR-type adhesive contact problems for power-law shaped axisymmetric punches

    NASA Astrophysics Data System (ADS)

    Borodich, Feodor M.; Galanov, Boris A.; Suarez-Alvarez, Maria M.

    2014-08-01

    The JKR (Johnson, Kendall, and Roberts) and Boussinesq-Kendall models describe adhesive frictionless contact between two isotropic elastic spheres, and between a flat-ended axisymmetric punch and an elastic half-space respectively. However, the shapes of contacting solids may be more general than spherical or flat ones. In addition, the derivation of the main formulae of these models is based on the assumption that the material points within the contact region can move along the punch surface without any friction. However, it is more natural to assume that a material point that came to contact with the punch sticks to its surface, i.e. to assume that the non-slipping boundary conditions are valid. It is shown that the frictionless JKR model may be generalized to arbitrary convex, blunt axisymmetric body, in particular to the case of the punch shape being described by monomial (power-law) punches of an arbitrary degree d≥1. The JKR and Boussinesq-Kendall models are particular cases of the problems for monomial punches, when the degree of the punch d is equal to two or it goes to infinity respectively. The generalized problems for monomial punches are studied under both frictionless and non-slipping (or no-slip) boundary conditions. It is shown that regardless of the boundary conditions, the solution to the problems is reduced to the same dimensionless relations among the actual force, displacements and contact radius. The explicit expressions are derived for the values of the pull-off force and for the corresponding critical contact radius. Connections of the results obtained for problems of nanoindentation in the case of the indenter shape near the tip has some deviation from its nominal shape and the shape function can be approximated by a monomial function of radius, are discussed.

  7. Survey of current component reliability problems and methods for prevention.

    NASA Technical Reports Server (NTRS)

    Hamiter, L.; Villella, F.

    1972-01-01

    The current reliability problems related to electronic components and microcircuits are presented in this paper. Specific process controls, design, materials, application constraints, destructive testing, electrical tests, and procedures for implementation are recommended to improve the reliability of selected electronic components.

  8. On the the Contact Lens Problem: Modeling Rigid and Elastic Beams on Thin Films

    NASA Astrophysics Data System (ADS)

    Trinh, Philippe; Wilson, Stephen; Stone, Howard

    2011-11-01

    Generally, contact lenses are prescribed by the practitioner to fit each individual patient's eye, but these fitting-philosophies are based on empirical studies and a certain degree of trial-and-error. A badly fitted lens can cause a range of afflictions, which varies from mild dry-eye-discomfort, to more serious corneal diseases. Thus, at this heart of this problem, is the question of how a rigid or elastic plate interacts with the free-surface of a thin viscous film. In this talk, we present several mathematical models for the study of these plate-and-fluid problems. Asymptotic and numerical results are described, and we explain the role of elasticity, surface tension, viscosity, and pressure in determining the equilibrium solutions. Finally, we discuss the implications of our work on the contact lens problem, as well as on other coating processes which involve elastic substrates.

  9. Kalker's algorithm Fastsim solves tangential contact problems with slip-dependent friction and friction anisotropy

    NASA Astrophysics Data System (ADS)

    Piotrowski, J.

    2010-07-01

    This paper presents two extensions of Kalker's algorithm Fastsim of the simplified theory of rolling contact. The first extension is for solving tangential contact problems with the coefficient of friction depending on slip velocity. Two friction laws have been considered: with and without recuperation of the static friction. According to the tribological hypothesis for metallic bodies shear failure, the friction law without recuperation of static friction is more suitable for wheel and rail than the other one. Sample results present local quantities inside the contact area (division to slip and adhesion, traction) as well as global ones (creep forces as functions of creepages and rolling velocity). For the coefficient of friction diminishing with slip, the creep forces decay after reaching the maximum and they depend on the rolling velocity. The second extension is for solving tangential contact problems with friction anisotropy characterised by a convex set of the permissible tangential tractions. The effect of the anisotropy has been shown on examples of rolling without spin and in the presence of pure spin for the elliptical set. The friction anisotropy influences tangential tractions and creep forces. Sample results present local and global quantities. Both extensions have been described with the same language of formulation and they may be merged into one, joint algorithm.

  10. Optimization of the heating surface shape in the contact melting problem

    NASA Technical Reports Server (NTRS)

    Fomin, Sergei A.; Cheng, Shangmo

    1991-01-01

    The theoretical analysis of contact melting by the migrating heat source with an arbitrary shaped isothermal heating surface is presented. After the substantiated simplification, the governing equations are transformed to the convenient equations for engineering calculations relationships. Analytical solutions are used for numerical prediction of optimal shape of the heating surface. The problem is investigated for the constant and for temperature dependent physical properties of the melt.

  11. Inverse Problem in Nondestructive Testing Using Arrayed Eddy Current Sensors

    PubMed Central

    Zaoui, Abdelhalim; Menana, Hocine; Feliachi, Mouloud; Berthiau, Gérard

    2010-01-01

    A fast crack profile reconstitution model in nondestructive testing is developed using an arrayed eddy current sensor. The inverse problem is based on an iterative solving of the direct problem using genetic algorithms. In the direct problem, assuming a current excitation, the incident field produced by all the coils of the arrayed sensor is obtained by the translation and superposition of the 2D axisymmetric finite element results obtained for one coil; the impedance variation of each coil, due to the crack, is obtained by the reciprocity principle involving the dyadic Green’s function. For the inverse problem, the surface of the crack is subdivided into rectangular cells, and the objective function is expressed only in terms of the depth of each cell. The evaluation of the dyadic Green’s function matrix is made independently of the iterative procedure, making the inversion very fast. PMID:22163680

  12. Inverse problem in nondestructive testing using arrayed eddy current sensors.

    PubMed

    Zaoui, Abdelhalim; Menana, Hocine; Feliachi, Mouloud; Berthiau, Gérard

    2010-01-01

    A fast crack profile reconstitution model in nondestructive testing is developed using an arrayed eddy current sensor. The inverse problem is based on an iterative solving of the direct problem using genetic algorithms. In the direct problem, assuming a current excitation, the incident field produced by all the coils of the arrayed sensor is obtained by the translation and superposition of the 2D axisymmetric finite element results obtained for one coil; the impedance variation of each coil, due to the crack, is obtained by the reciprocity principle involving the dyadic Green's function. For the inverse problem, the surface of the crack is subdivided into rectangular cells, and the objective function is expressed only in terms of the depth of each cell. The evaluation of the dyadic Green's function matrix is made independently of the iterative procedure, making the inversion very fast. PMID:22163680

  13. Workshops and problems for benchmarking eddy current codes

    SciTech Connect

    Turner, L.R.; Davey, K.; Ida, N.; Rodger, D.; Kameari, A.; Bossavit, A.; Emson, C.R.I.

    1988-08-01

    A series of six workshops was held in 1986 and 1987 to compare eddy current codes, using six benchmark problems. The problems included transient and steady-state ac magnetic fields, close and far boundary conditions, magnetic and non-magnetic materials. All the problems were based either on experiments or on geometries that can be solved analytically. The workshops and solutions to the problems are described. Results show that many different methods and formulations give satisfactory solutions, and that in many cases reduced dimensionality or coarse discretization can give acceptable results while reducing the computer time required. A second two-year series of TEAM (Testing Electromagnetic Analysis Methods) workshops, using six more problems, is underway. 12 refs., 15 figs., 4 tabs.

  14. Current Quality-of-Life Tools Available for Use in Contact Dermatitis.

    PubMed

    Swietlik, Jacquelyn; Reeder, Margo

    2016-01-01

    Contact dermatitis is a common dermatologic condition that can cause significant impairment in patients' overall quality of life (QoL). This impact is separate and potentially more clinically relevant than one's disease "severity" in contact dermatitis and should be consistently addressed by dermatologists. Despite this, QoL tools specific to contact dermatitis are lacking, and there is little consistency in the literature regarding the tool used to evaluate clinical response to therapies. Measurements currently available to evaluate disease-related QoL in contact dermatitis fit into 1 of the following 3 general types: generic health-related QoL measures, dermatology-related QoL measures, or specific dermatologic disease-related QoL measures. This article reviews the strengths and weaknesses of existing QoL tools used in contact dermatitis including: Short Form Survey 36, Dermatology Life Quality Index, Skindex-29, Skindex-16, Dermatology-Specific Quality of Life, and Fragrance Quality of Life Index. PMID:27427819

  15. Computational dosimetry for grounded and ungrounded human models due to contact current.

    PubMed

    Chan, Kwok Hung; Hattori, Junya; Laakso, Ilkka; Hirata, Akimasa; Taki, Masao

    2013-08-01

    This study presents the computational dosimetry of contact currents for grounded and ungrounded human models. The uncertainty of the quasi-static (QS) approximation of the in situ electric field induced in a grounded/ungrounded human body due to the contact current is first estimated. Different scenarios of cylindrical and anatomical human body models are considered, and the results are compared with the full-wave analysis. In the QS analysis, the induced field in the grounded cylindrical model is calculated by the QS finite-difference time-domain (QS-FDTD) method, and compared with the analytical solution. Because no analytical solution is available for the grounded/ungrounded anatomical human body model, the results of the QS-FDTD method are then compared with those of the conventional FDTD method. The upper frequency limit for the QS approximation in the contact current dosimetry is found to be 3 MHz, with a relative local error of less than 10%. The error increases above this frequency, which can be attributed to the neglect of the displacement current. The QS or conventional FDTD method is used for the dosimetry of induced electric field and/or specific absorption rate (SAR) for a contact current injected into the index finger of a human body model in the frequency range from 10 Hz to 100 MHz. The in situ electric fields or SAR are compared with the basic restrictions in the international guidelines/standards. The maximum electric field or the 99th percentile value of the electric fields appear not only in the fat and muscle tissues of the finger, but also around the wrist, forearm, and the upper arm. Some discrepancies are observed between the basic restrictions for the electric field and SAR and the reference levels for the contact current, especially in the extremities. These discrepancies are shown by an equation that relates the current density, tissue conductivity, and induced electric field in the finger with a cross-sectional area of 1 cm(2). PMID

  16. Computational dosimetry for grounded and ungrounded human models due to contact current

    NASA Astrophysics Data System (ADS)

    Chan, Kwok Hung; Hattori, Junya; Laakso, Ilkka; Hirata, Akimasa; Taki, Masao

    2013-08-01

    This study presents the computational dosimetry of contact currents for grounded and ungrounded human models. The uncertainty of the quasi-static (QS) approximation of the in situ electric field induced in a grounded/ungrounded human body due to the contact current is first estimated. Different scenarios of cylindrical and anatomical human body models are considered, and the results are compared with the full-wave analysis. In the QS analysis, the induced field in the grounded cylindrical model is calculated by the QS finite-difference time-domain (QS-FDTD) method, and compared with the analytical solution. Because no analytical solution is available for the grounded/ungrounded anatomical human body model, the results of the QS-FDTD method are then compared with those of the conventional FDTD method. The upper frequency limit for the QS approximation in the contact current dosimetry is found to be 3 MHz, with a relative local error of less than 10%. The error increases above this frequency, which can be attributed to the neglect of the displacement current. The QS or conventional FDTD method is used for the dosimetry of induced electric field and/or specific absorption rate (SAR) for a contact current injected into the index finger of a human body model in the frequency range from 10 Hz to 100 MHz. The in situ electric fields or SAR are compared with the basic restrictions in the international guidelines/standards. The maximum electric field or the 99th percentile value of the electric fields appear not only in the fat and muscle tissues of the finger, but also around the wrist, forearm, and the upper arm. Some discrepancies are observed between the basic restrictions for the electric field and SAR and the reference levels for the contact current, especially in the extremities. These discrepancies are shown by an equation that relates the current density, tissue conductivity, and induced electric field in the finger with a cross-sectional area of 1 cm2.

  17. Soldered Contact and Current Risetime Effects on Negative Polarity Wire Array Z-pinches

    SciTech Connect

    Chalenski, D. A.; Kusse, B. R.; Greenly, J. B.; Blesener, I. C.; McBride, R. D.; Hammer, D. A.; Knapp, P. F.

    2009-01-21

    The Cornell University COBRA pulser is a nominal 1 MA machine, capable of driving up to 32 wire cylindrical Z-pinch arrays. COBRA can operate with variable current risetimes ranging from 100 ns to 200 ns (short and long pulse, respectively). Wires are typically strung with a 'press' contact to the electrode hardware, where the wire is loosely pulled against the hardware and held there to establish electrical contact. The machine is normally negative, but a bolt-on convolute can be used to modify the current path and effectively produce positive polarity operation at the load.Previous research with single wires on a 1-5 kA pulser has shown that soldering the wire, thereby improving the wire/electrode contact, and operating in positive polarity can improve the energy deposition into the wire and enhance wire core expansion. Negative polarity showed no difference. Previous experiments on the negative polarity, 20 MA, 100 ns Z accelerator have shown that improving the contact improved the x-ray yield.Cornell data were collected on 16-wire Aluminum Z-pinch arrays in negative polarity. Experiments were conducted with both short and long current pulses with soldered and no-soldered wire/electrode contacts. The initiation, ablation, implosion and stagnation phases were compared for these four conditions. Time dependent x-ray signals were measured using diodes and diamond detectors. An inductive voltage monitor was used to infer minimum current radius achieved, as defined by a uniform shell of current moving radially inward, producing a time dependent inductance. Total energy data were collected with a metal-strip bolometer. Self-emission data were collected by an XUV 4-frame camera and an optical streak camera.In negative polarity and with short pulses, soldering appeared to produce a smaller radius pinch and decrease variations in the x-ray pulse shape. The bolometer, laser backlighter, 4-frame and streak cameras showed negligible differences in the initiation ablation

  18. Higher Education in the Philippines: An Overview and Current Problems

    ERIC Educational Resources Information Center

    Perlman, Daniel H.

    1978-01-01

    Among current problems facing higher education in the Philippines are (1) bilingualism (English and Filipino), (2) accreditation, (3) government regulations, (4) overproduction of graduates, (5) mismatch between graduates and needed skills, (6) imbalance between public and private schools, (7) overconcentration of students in Manila, and (8)…

  19. AACSB Accreditation in China--Current Situation, Problems, and Solutions

    ERIC Educational Resources Information Center

    Zhang, Xinrui; Gao, Yan

    2012-01-01

    This paper first introduces the background of the AACSB (Association to Advance Collegiate Schools of Business) accreditation, and then analyzes the current status of the participation of Chinese business schools in AACSB accreditation. Based on the data analysis, the paper points out that there are two main problems in the Chinese business…

  20. Current Domestic Problems, Social Studies: 6416.18.

    ERIC Educational Resources Information Center

    Moore, John A.

    Secondary students learn to deal objectively with domestic issues and problems in this quinmester elective course. Emphasis is upon providing students with an opportunity for indepth study in critical thinking on current controversial issues, using activity units as a principal teaching technique. The objectives are for students to identify and…

  1. Solution of the ZnO/p contact problem in a-Si:H solar cells

    SciTech Connect

    Kubon, M.; Boehmer, E.; Gastel, M.; Siebke, F.; Beyer, W.; Beneking, C.; Wagner, H.

    1994-12-31

    This paper addresses the problem of preparing a good p-layer contact with zinc oxide as TCO. The approach was to deposit pin cells with different p-layer recipes on ZnO coated SnO{sub 2}:F and on uncoated SnO{sub 2}:F in one run. The pin cells prepared on the ZnO surface exhibit a lower fill factor (FF). The experiments demonstrate that the hydrogen interaction with the ZnO surface plays the most decisive role for the ZnO/p contact. The authors explain the observed effects using a band diagram of the ZnO/p interface and show that the accumulation layer at the ZnO surface--caused by atomic hydrogen in the plasma--is responsible for the low FF in pin cells. Based on this model the contact problem is solved by introducing a {micro}c-n-Si intralayer between ZnO nd p layer resulting in an identical high FF on both ZnO and SnO{sub 2} substrates.

  2. Publication analysis of the contact lens field: What are the current topics of interest?

    PubMed Central

    Cardona, Genís; Sanz, Joan P.

    2014-01-01

    Purpose To determine the main current research interests of scientists working in the contact lens field. Methods All articles published in the 2011 issues of all journals included in the Journal Citation Reports subject category Ophthalmology were inspected to expose those papers related to the contact lens field. Information regarding source journal was obtained and authorship details were recorded to determine the top most prolific authors, institutions and countries. A comprehensive list of key words was compiled to generate a two-dimensional term map in which the frequency of occurrence of a particular term is defined by label size and the distance between two terms is an indication of the relatedness of these terms, based on their co-occurrences within groups of key words. Clusters of related terms were also identified. Results Visual examination of all articles uncovered a total of 156 papers, published in 28 different journals. Contact Lens & Anterior Eye, Eye & Contact Lens and Optometry and Vision Science had 27 articles each. The most prolific authors and institutions revealed the predominance of countries with long research tradition in the contact lens field. Ten different word clusters or areas of interest were identified, including both traditional, yet unresolved issues (e.g., comfort or dry eye), and the latest research efforts (e.g., myopia control). Conclusions These findings, which revealed contact lenses to be a fertile area of research, may be of relevance to new researchers as well as to those interested in exploring the latest research trends in this scientific discipline. PMID:25649639

  3. An approach to ERO problem in displacement eddy current sensor

    NASA Astrophysics Data System (ADS)

    Yu, Yating; Tian, Guiyun; Li, Xinhua; Simm, Anthony

    2013-09-01

    Eddy current (EC) sensors are widely applied in displacement (proximity) measurement as well as nondestructive testing and evaluation for defect detection or material characterisation. For displacement measurement, one of the research aims is to overcome measurement uncertainties due to material variation and inhomogeneity. This problem is called as electrical runout (ERO) problem. In this paper, an approach to ERO problem is presented based on the coaxial ellipse distribution (CED) pattern of the EC sensor. In the CED pattern, the real and the imaginary parts of the magnetic flux density in the z-component (B z ), with the variation of the sample conductivity under the different lift-offs, are located on an ellipse curve. Furthermore, the CED pattern is verified by the different sensor specifications, such as excitation frequency and probe coil geometry. According to the CED pattern, the ERO problem in EC sensors can be overcome well when the sample is magnetised to saturation.

  4. Contact Problem Of Conducting And Heated Punch On A Multifield Foundation

    NASA Astrophysics Data System (ADS)

    Rogowski, B.

    2015-08-01

    The solution for a multifield material subjected to temperature loading in a circular region is presented in an explicit analytical form. The study concerns the steady - state thermal loading infinite region (heated embedded inclusion), half - space region and two - constituent magneto - electro - thermo - elastic material region. The new mono - harmonic potential functions, obtained by the author, are used in the analysis of punch problem. The more interested case in which the contact region is annular is analyzed. By using the methods of triple integral equations and series solution technique the solution for an indentured multifield substrate over an annular contact region is given. The sensitivity analysis of obtained indentation parameters shows some interesting points. In particular, it shows that the increasing of the applied electric and magnetic potentials reduces the indentation depth in multifield materials.

  5. Multiple pole electromagnetic propulsion system with separated ballistic guidance and electrical current contact surfaces

    DOEpatents

    Sims, Jr., James R.

    2008-07-15

    An electromagnetic propulsion system is disclosed having separate rails for ballistic guidance and for carrying current. In this system, one or more pairs of ballistic guidance rails are provided, with each ballistic guidance rail having a pair of current carrying rails joined to it to form a combined rail. Each combined rail is separated electrically from adjacent combined rails by electrically insulating blocks. Each of the current carrying rails in a given combined rail pair have the same electrical polarity, and the polarities alternate between adjacent combined rails. Armatures contact current carrying rails to complete the circuit to generate the accelerating Lorentz force on the armatures. Bore riders on the sabot and/or projectile are in contact with the ballistic guide rails. Separation of the current carrying and ballistic guidance functions increases resistance of the system to rail movement and bending, as well as reduced wear/damage to the rails. In further embodiments, a circumferential over wrap providing compressive force on the rails further increases resistance of the system to rail movement and bending.

  6. Solving time-dependent two-dimensional eddy current problems

    NASA Technical Reports Server (NTRS)

    Lee, Min Eig; Hariharan, S. I.; Ida, Nathan

    1988-01-01

    Results of transient eddy current calculations are reported. For simplicity, a two-dimensional transverse magnetic field which is incident on an infinitely long conductor is considered. The conductor is assumed to be a good but not perfect conductor. The resulting problem is an interface initial boundary value problem with the boundary of the conductor being the interface. A finite difference method is used to march the solution explicitly in time. The method is shown. Treatment of appropriate radiation conditions is given special consideration. Results are validated with approximate analytic solutions. Two stringent test cases of high and low frequency incident waves are considered to validate the results.

  7. Numerical results for the WFNDEC 2012 eddy current benchmark problem

    NASA Astrophysics Data System (ADS)

    Theodoulidis, T. P.; Martinos, J.; Poulakis, N.

    2013-01-01

    We present numerical results for the World Federation of NDE Centers (WFNDEC) 2012 eddy current benchmark problem obtained with a commercial FEM package (Comsol Multiphysics). The measurements of the benchmark problem consist of coil impedance values acquired when an inspection probe coil is moved inside an Inconel tube along an axial through-wall notch. The simulation runs smoothly with minimal user interference (default settings used for mesh and solver) and agreement between numerical and experimental results is excellent for all five inspection frequencies. Comments are made for the pros and cons of FEM and also some good practice rules are presented when using such numerical tools.

  8. Current densities and total contact currents during forest clearing tasks under 400 kV power lines.

    PubMed

    Korpinen, Leena; Kuisti, Harri; Elovaara, Jarmo

    2016-09-01

    The aim of the study was to analyze all values of electric currents from measured periods while performing tasks in forest clearing. The objective was also to choose and analyze measurement cases, where current measurements successfully lasted the entire work period (about 30 min). Two forestry workers volunteered to perform four forest clearing tasks under 400 kV power lines. The sampling frequency of the current measurements was 1 sample/s. The maximum values of the current densities were 1.0-1.2 mA/m(2) (calculated internal EFs 5.0-12.0 mV/m), and the average values were 0.2-0.4 mA/m(2) . The highest contact current was 167.4 μA. All measured values during forest clearing tasks were lower than basic restrictions (0.1 V/m and 0.8 V/m) of the International Commission on Non-Ionizing Radiation Protection. Bioelectromagnetics. 37:423-428, 2016. © 2016 The Authors. Bioelectromagnetics published by Wiley Periodicals, Inc. PMID:27192179

  9. Ultrahigh-resolution and non-contact diameter measurement of metallic wire using eddy current sensor.

    PubMed

    Li, Wei; Wang, Hongbo; Feng, Zhihua

    2014-08-01

    This paper proposes a new method using eddy current sensor (ECS) for online non-contact diameter measurement of metallic wires with ultrahigh resolution. A prototype sensor was designed, fabricated, and tested for copper wires with diameters ranging from 1.12 mm to 1.30 mm. A solenoid coil with dimensions of 16 mm long and 2.1 mm in diameter is used as sensing element with a working frequency of 1.3 MHz. With a well-designed bridge, the sensing coil's inductance variation can be detected and the wire's diameter can be calculated. The ECS system demonstrated a dynamic resolution better than 2.2 μm and a static resolution better than 0.42 nm for a wire with a diameter of 1.3 mm. This non-contact method has competitive advantages over other methods in many aspects, especially in terms of measurement resolution. PMID:25173300

  10. Photon assisted current in molecular nanojunctions with novel types of contacts

    SciTech Connect

    Fainberg, Boris D.

    2014-03-31

    We propose new approaches to coherent control of transport via molecular junctions, which bypasses several of the hurdles to experimental realization of optically manipulated nanoelectronics noted in the previous literature. The first method is based on the application of intrinsic semiconductor contacts and optical frequencies below the semiconductor bandgap. Our analytical theory predicts a new phenomenon, referred to as coherent destruction of induced tunnelling, which extends the phenomenon of coherent destruction of tunnelling frequently discussed in the previous literature. We also propose to use graphene electrodes as a platform for effective photon assisted tunneling through molecular conduction nanojunctions. We predict dramatic increasing currents evaluated at side-band energies ∼nħω (n is a whole number) related to the modification of graphene gapless spectrum under the action of external electromagnetic field of frequency ω. Our results illustrate the potential of semiconductor and graphene contacts in coherent control of photocurrent.

  11. Numerical simulations of the moving contact line problem using a diffuse-interface model

    NASA Astrophysics Data System (ADS)

    Afzaal, Muhammad; Sibley, David; Duncan, Andrew; Yatsyshin, Petr; Duran-Olivencia, Miguel A.; Nold, Andreas; Savva, Nikos; Schmuck, Markus; Kalliadasis, Serafim

    2015-11-01

    Moving contact lines are a ubiquitous phenomenon both in nature and in many modern technologies. One prevalent way of numerically tackling the problem is with diffuse-interface (phase-field) models, where the classical sharp-interface model of continuum mechanics is relaxed to one with a finite thickness fluid-fluid interface, capturing physics from mesoscopic lengthscales. The present work is devoted to the study of the contact line between two fluids confined by two parallel plates, i.e. a dynamically moving meniscus. Our approach is based on a coupled Navier-Stokes/Cahn-Hilliard model. This system of partial differential equations allows a tractable numerical solution to be computed, capturing diffusive and advective effects in a prototypical case study in a finite-element framework. Particular attention is paid to the static and dynamic contact angle of the meniscus advancing or receding between the plates. The results obtained from our approach are compared to the classical sharp-interface model to elicit the importance of considering diffusion and associated effects. We acknowledge financial support from European Research Council via Advanced Grant No. 247031.

  12. Bassoonists' medical problems-current state of knowledge.

    PubMed

    Dawson, William J

    2012-06-01

    Specific musical instruments can be a source of physical problems to their players. Based on reviews of the literature and personal experience, this paper summarizes current knowledge of problems affecting musicians who play instruments in the bassoon family (including the bassoon, contrabassoon, and several other instruments). Prevalence rates are higher in reports of surveys (ranging up to 86%), compared to clinical reports of patients seen and treated. Significant risk factors include young age, small body size, female gender, and use of large instruments. Problems unique to bassoonists are rare; most physical difficulties also are seen in general musculoskeletal clinical practices and in musicians playing all types of instruments. The left upper extremity is more commonly affected by overuse-related conditions in bassoonists. Non-playing-related problems are equally important for consideration (such as degenerative disorders and acute trauma), since they also affect practice and performance. Little experimental data exist to validate current and widely-held principles of treatment, rehabilitation, and prevention. PMID:22739824

  13. Contact resistance problems applying ERT on low bulk density forested stony soils. Is there a solution?

    NASA Astrophysics Data System (ADS)

    Deraedt, Deborah; Touzé, Camille; Robert, Tanguy; Colinet, Gilles; Degré, Aurore; Garré, Sarah

    2015-04-01

    Electrical resistivity tomography (ERT) has often been put forward as a promising tool to quantify soil water and solute fluxes in a non-invasive way. In our experiment, we wanted to determine preferential flow processes along a forested hillslope using a saline tracer with ERT. The experiment was conducted in the Houille watershed, subcatchment of the Meuse located in the North of Belgian Ardennes (50° 1'52.6'N, 4° 53'22.5'E). The climate is continental but the soil under spruce (Picea abies (L.) Karst.) and Douglas fire stand (Pseudotsuga menziesii (Mirb.) Franco) remains quite dry (19% WVC in average) during the whole year. The soil is Cambisol and the parent rock is Devonian schist covered with variable thickness of silty loam soil. The soil density ranges from 1.13 to 1.87 g/cm3 on average. The stone content varies from 20 to 89% and the soil depth fluctuates between 70 and 130 cm. The ERT tests took place on June 1st 2012, April 1st, 2nd and 3rd 2014 and May 12th 2014. We used the Terrameter LS 12 channels (ABEM, Sweden) in 2012 test and the DAS-1 (Multi-Phase Technologies, United States) in 2014. Different electrode configurations and arrays were adopted for different dates (transect and grid arrays and Wenner - Schlumberger, Wenner alpha and dipole-dipole configurations). During all tests, we systematically faced technical problems, mainly related to bad electrode contact. The recorded data show values of contact resistance above 14873 Ω (our target value would be below 3000 Ω). Subsequently, we tried to improve the contact by predrilling the soil and pouring water in the electrode holes. The contact resistance improved to 14040 Ω as minimum. The same procedure with liquid mud was then tested to prevent quick percolation of the water from the electrode location. As a result, the lower contact resistance dropped to 11745 Ω. Finally, we applied about 25 litre of saline solution (CaCl2, 0.75g/L) homogeneously on the electrode grid. The minimum value of

  14. Evaluation of the energy barrier for failure of Au atomic contact based on temperature dependent current-voltage characteristics.

    PubMed

    Aiba, Akira; Kaneko, Satoshi; Fujii, Shintaro; Nishino, Tomoaki; Kiguchi, Manabu

    2016-08-01

    We investigated the mechanical stability of single gold atomic contacts at an applied bias voltage of 0-1 V using a nano-fabricated mechanically controllable break junction technique at 300-400 K under ambient conditions. The single atomic contact shows the quantized conductance (G0 = 2e(2)/h) and can carry considerably large current, which results in the current-induced failure of the contact. The contact failure behaviour under the applied bias conditions was studied by statistical analysis of the current-voltage (I-V) curves of the single Au contacts. We demonstrated that, at the elevated temperature of 300-400 K, the current-induced local heating effect is negligibly small and current-induced forces in the contact are responsible for the observed failure of the single gold contacts under the high bias voltage conditions (>0.4 V). Furthermore, based on the temperature dependence of the contact failure behaviour in the I-V curves, the energy barrier of the contact-failure was evaluated to be ca. 0.1 V. PMID:27427285

  15. An alternative formulation for quasi-static frictional and cohesive contact problems

    NASA Astrophysics Data System (ADS)

    Areias, P.; Pinto da Costa, A.; Rabczuk, T.; Queirós de Melo, F. J. M.; Dias-da-Costa, D.; Bezzeghoud, Mourad

    2014-04-01

    It is known by Engineering practitioners that quasi-static contact problems with friction and cohesive laws often present convergence difficulties in Newton iteration. These are commonly attributed to the non-smoothness of the equilibrium system. However, non-uniqueness of solutions is often an obstacle for convergence. We discuss these conditions in detail and present a general algorithm for 3D which is shown to have quadratic convergence in the Newton-Raphson iteration even for parts of the domain where multiple solutions exist. Chen-Mangasarian replacement functions remove the non-smoothness corresponding to both the stick-slip and normal complementarity conditions. Contrasting with Augmented Lagrangian methods, second-order updating is performed for all degrees-of-freedom. Stick condition is automatically selected by the algorithm for regions with multiple solutions. The resulting Jacobian determinant is independent of the friction coefficient, at the expense of an increased number of nodal degrees-of-freedom. Aspects such as a dedicated pivoting for constrained problems are also of crucial importance for a successful solution finding. The resulting 3D mixed formulation, with 7 degrees-of-freedom in each node (displacement components, friction multiplier, friction force components and normal force) is tested with representative numerical examples (both contact with friction and cohesive force), which show remarkable robustness and generality.

  16. Inverse problem for the current loop model: Possibilities and restrictions

    NASA Astrophysics Data System (ADS)

    Demina, I. M.; Farafonova, Yu. G.

    2016-07-01

    The possibilities of determining arbitrary current loop parameters based on the spatial structures of the magnetic field components generated by this loop on a sphere with a specified radius have been considered with the use of models. The model parameters were selected such that anomalies created by current loops on a sphere with a radius of 6378 km would be comparable in value with the different-scale anomalies of the observed main geomagnetic field (MGF). The least squares method was used to solve the inverse problem. Estimates close to the specified values were obtained for all current loop parameters except the current strength and radius. The radius determination error can reach ±120 km; at the same time, the magnetic moment value is determined with an accuracy of ±1%. The resolvability of the current force and radius can to a certain degree be improved by decreasing the observation sphere radius such that the ratio of the source distance to the current loop radius would be at least smaller than eight, which can be difficult to reach when modeling MGF.

  17. Effect of interfacial oxide layers on the current-voltage characteristics of Al-Si contacts

    NASA Technical Reports Server (NTRS)

    Porter, W. A.; Parker, D. L.

    1976-01-01

    Aluminum-silicon contacts with very thin interfacial oxide layers and various surface impurity concentrations are studied for both n and p-type silicon. To determine the surface impurity concentrations on p(+)-p and n(+)-n structures, a modified C-V technique was utilized. Effects of interfacial oxide layers and surface impurity concentrations on current-voltage characteristics are discussed based on the energy band diagrams from the conductance-voltage plots. The interfacial oxide and aluminum layer causes image contrasts on X-ray topographs.

  18. Theoretical study of Contact Effects in Current through an Organic Molecule

    NASA Astrophysics Data System (ADS)

    Nara, Jun; Kino, Hiori; Kobayashi, Nobuhiko; Tsukada, Masaru; Ohno, Takahisa

    2003-03-01

    Recently, the transport properties of single-organic molecules have attracted much attention. In analyzing their transport properties theoretically, it is important to include the realistic atomic configurations of the contact between molecules and metal electrodes. We calculated the conductance of a benzene-(1,4)-dithiolate sandwiched with two gold electrodes by means of ab initio method, and examined the effect of the contact structures on it. It is found that the conductance depends significantly on the bonding site of the S atom on Au(111) surface such that a current through the ontop site is much smaller than that through the hollow site or the bridge site. These results suggest that the contact structure is essential to determine the conductance properties of molecular devices. The present calculations were carried out using the Numerical Materials Simulator in National Institute for Materials Science. This research is partially supported by ACT-JST and Special Coordination Funds of the Ministry of Education, Culture, Sports, Science and Technology of the Japanese Government.

  19. A contact algorithm for 3D discrete and finite element contact problems based on penalty function method

    NASA Astrophysics Data System (ADS)

    Zang, Mengyan; Gao, Wei; Lei, Zhou

    2011-11-01

    A contact algorithm in the context of the combined discrete element (DE) and finite element (FE) method is proposed. The algorithm, which is based on the node-to-surface method used in finite element method, treats each spherical discrete element as a slave node and the surfaces of the finite element domain as the master surfaces. The contact force on the contact interface is processed by using a penalty function method. Afterward, a modification of the combined DE/FE method is proposed. Following that, the corresponding numerical code is implemented into the in-house developed code. To test the accuracy of the proposed algorithm, the impact between two identical bars and the vibration process of a laminated glass plate under impact of elastic sphere are simulated in elastic range. By comparing the results with the analytical solution and/or that calculated by using LS-DYNA, it is found that they agree with each other very well. The accuracy of the algorithm proposed in this paper is proved.

  20. Designer switches: Effect of contact geometry on the transient current of a strongly correlated quantum dot

    NASA Astrophysics Data System (ADS)

    Goker, Ali Ihsan; Zhu, Zhiyong; Schwingenschlogl, Udo; Manchon, Aurelien

    2011-03-01

    The time-dependent non-crossing approximation is utilized to investigate the influence of the geometry of contacts made of gold on time dependent current through a quantum dot suddenly shifted into the Kondo regime via a gate voltage. For an asymmetrically coupled system, instantaneous conductance exhibits complex fluctuations. We identify the frequencies participating in these fluctuations and they turn out to be proportional to the separation between the sharp features in the density of states and the Fermi level. Increasing ambient temperature or bias quenches the amplitude of these fluctuations. This suggests that the interference between the emerging Kondo resonance and the van Hove singularities in the density of states is the underlying microscopic mechanism for these fluctuations. Based on these observations, we predict that using different electrode geometries would give rise to drastically different transient currents which can be accessed with state-of-the-art ultrafast pump-probe techniques. King Abdullah University of Science and Technology.

  1. Solving time-dependent two-dimensional eddy current problems

    NASA Technical Reports Server (NTRS)

    Lee, Min Eig; Hariharan, S. I.; Ida, Nathan

    1990-01-01

    Transient eddy current calculations are presented for an EM wave-scattering and field-penetrating case in which a two-dimensional transverse magnetic field is incident on a good (i.e., not perfect) and infinitely long conductor. The problem thus posed is of initial boundary-value interface type, where the boundary of the conductor constitutes the interface. A potential function is used for time-domain modeling of the situation, and finite difference-time domain techniques are used to march the potential function explicitly in time. Attention is given to the case of LF radiation conditions.

  2. Imaging the local forward current density of solar cells by dynamical precision contact thermography

    SciTech Connect

    Breitenstein, O.; Eberhardt, W.; Iwig, K.

    1994-12-31

    In spite of many techniques of measuring the local lifetime or the local short circuit current, no non-destructive technique has been available for imaging the local forward current density, which determines the open circuit voltage and the fill factor of solar cells. The authors demonstrate the application of a new analyzing technique, enabling non-destructive shunt hunting in forward direction. A periodical forward current is applied to the cell, and only the dynamical temperature response is measured in contact mode with a resolution below 10 {micro}K. Mechanical scanning of the T-sensor position yields a thermogram with a spatial resolution well below 1 mm and a current density resolution well below 1 mA/cm{sup 2}. First results show that both the edges of solar cells and their interior may have sites of a locally increased forward current. Hot spots measured in reverse bias direction only occasionally coincide with these warm spots measured in forward direction.

  3. Problem of the length of the current interglacial

    NASA Astrophysics Data System (ADS)

    Dergachev, V. A.; Raspopov, O. M.

    2013-12-01

    The climate during the past hundreds of thousands of years has been characterized by a rather distinct periodicity of about 100000 yr with brief warming periods (interglacials) lasting approximately 10000-12000 yr. Today, mankind is living in an interglacial period that began about 11 ka ago. In light of the discussion about global warming observed in recent decades, which advocates of an anthropogenic impact associate with emission of greenhouse gases due to combustion of fossil fuel, the question arises concerning the duration of the current interglacial. The data available on climate change and solar radiation on a time scale of the last millions of years are critically analyzed in this article and the problem of the length of the current interglacial is discussed.

  4. Neural prosthetic systems: current problems and future directions.

    PubMed

    Chestek, Cindy A; Cunningham, John P; Gilja, Vikash; Nuyujukian, Paul; Ryu, Stephen I; Shenoy, Krishna V

    2009-01-01

    By decoding neural activity into useful behavioral commands, neural prosthetic systems seek to improve the lives of severely disabled human patients. Motor decoding algorithms, which map neural spiking data to control parameters of a device such as a prosthetic arm, have received particular attention in the literature. Here, we highlight several outstanding problems that exist in most current approaches to decode algorithm design. These include two problems that we argue will unlikely result in further dramatic increases in performance, specifically spike sorting and spiking models. We also discuss three issues that have been less examined in the literature, and we argue that addressing these issues may result in dramatic future increases in performance. These include: non-stationarity of recorded waveforms, limitations of a linear mappings between neural activity and movement kinematics, and the low signal to noise ratio of the neural data. We demonstrate these problems with data from 39 experimental sessions with a non-human primate performing reaches and with recent literature. In all, this study suggests that research in cortically-controlled prosthetic systems may require reprioritization to achieve performance that is acceptable for a clinically viable human system. PMID:19963796

  5. Effect of the periphery of metal-semiconductor contacts with Schottky barriers on their static current-voltage characteristic

    SciTech Connect

    Torkhov, N. A.

    2010-05-15

    Kelvin probe atomic-force microscopy of the electrostatic surface potential of gold Schottky contacts on n-GaAs showed that there is an extended transition area (halo) (tens of micrometers) around contacts in which the surface potential varies from the n-GaAs free surface potential to the gold contact surface potential. The contact potential and its distribution in the surrounding halo are controlled by the contact structure. The study of spreading currents showed that there is a high-conductance area (periphery) around the contact perimeter due to strong electric fields of the halo, which causes leakage currents. The conductivity of the main contact area is caused by 100- to 200-nm local areas with higher and lower conducting abilities. Mesa formation around contacts causes a decrease in the work function, a decrease in the halo extent and electric field strength, which is accompanied by spreading and decreasing of the peripheral area conductance. This results in disappearance of leakage currents and a decrease in the ideality index. In contrast, protection of the peripheral area by a SiO{sub 2} insulating film 0.5 {mu}m thick increases the work function, which is accompanied by the formation of potential lobes around the contact in two mutually perpendicular crystallographic directions. A stronger penetration of halo electric fields into the contact area results in an increase in the ideality index and disappearance of high-conductance peripheral area and leakage currents. The difference between the electrical properties of the periphery, gold grains, and their boundaries controls the contact switching mechanism when applying forward or reverse biases.

  6. Inflammatory bowel diseases: Current problems and future tasks.

    PubMed

    Actis, Giovanni C; Pellicano, Rinaldo; Rosina, Floriano

    2014-08-01

    Current knowledge on inflammatory bowel disease (IBD) is mainly endorsed by controlled trials and epidemiologic studies. Yet, we seldom look at the messages from real-world practice. Among a patient population followed since 2008, we looked at an unselected sample of 64 IBD patients [26 Crohn's disease (CD) and 38 ulcerative colitis (UC)] who had been seen as out-patients in the last year. Inducing remission, mesalamines (86% for UC/69% for CD/33%-16% as MMX formulation) prevailed as prescriptions; steroids (55%/19% for UC/CD) ranked second. Prescription of third-party drugs (antibiotics, NSAIDs, biologics) and adherence, were issues in the maintenance. 34% of CD, and 23% of UC patients showed accompanying immunologic diseases: CD-associated familiar psoriasis (4:9) ranked first. Main Message. The association between IBD (CD mainly) and psoriasis, now found in our practice, matches current basic science gathering IBD together with psoriasis (and perhaps chronic respiratory disease) under the comprehensive term "barrier organ disease" wherein an epithelial surface with sensor systems rules contacts between outer antigens and a reactive underneath tissue, with the balance between inflammation and quiescence kept at any time by mucosal permeability. IBD is thus viewed as a polyfactorial/polygenic/syndromic disorder, embedded into a galaxy of immune conditions offering multiple points of attack. This mindset of splitting the IBDs into pathogenic categories may allow overcoming the uniformly targeting of a single cytokine by biological drugs, in favor of demarcating the boundaries between different disease-subtype-specific indications, and paving the way to future personalized strategies. PMID:25133045

  7. Inflammatory bowel diseases: Current problems and future tasks

    PubMed Central

    Actis, Giovanni C; Pellicano, Rinaldo; Rosina, Floriano

    2014-01-01

    Current knowledge on inflammatory bowel disease (IBD) is mainly endorsed by controlled trials and epidemiologic studies. Yet, we seldom look at the messages from real-world practice. Among a patient population followed since 2008, we looked at an unselected sample of 64 IBD patients [26 Crohn’s disease (CD) and 38 ulcerative colitis (UC)] who had been seen as out-patients in the last year. Inducing remission, mesalamines (86% for UC/69% for CD/33%-16% as MMX formulation) prevailed as prescriptions; steroids (55%/19% for UC/CD) ranked second. Prescription of third-party drugs (antibiotics, NSAIDs, biologics) and adherence, were issues in the maintenance. 34% of CD, and 23% of UC patients showed accompanying immunologic diseases: CD-associated familiar psoriasis (4:9) ranked first. Main Message. The association between IBD (CD mainly) and psoriasis, now found in our practice, matches current basic science gathering IBD together with psoriasis (and perhaps chronic respiratory disease) under the comprehensive term “barrier organ disease” wherein an epithelial surface with sensor systems rules contacts between outer antigens and a reactive underneath tissue, with the balance between inflammation and quiescence kept at any time by mucosal permeability. IBD is thus viewed as a polyfactorial/polygenic/syndromic disorder, embedded into a galaxy of immune conditions offering multiple points of attack. This mindset of splitting the IBDs into pathogenic categories may allow overcoming the uniformly targeting of a single cytokine by biological drugs, in favor of demarcating the boundaries between different disease-subtype-specific indications, and paving the way to future personalized strategies. PMID:25133045

  8. Ionic channels in excitable membranes. Current problems and biophysical approaches.

    PubMed Central

    Hille, B

    1978-01-01

    Ionic channels are gated aqueous pores whose conformational changes are driven by the electric field in the membrane. Gating may be studied by three electrical methods: ionic current transients, ionic current fluctuations, and "gating current," and probably occurs through a series of conformational changes in the channel leading to an all-or-nothing opening of the pore. When the potential is held constant, the gating steps come to equilibrium rather than reaching an energy-dissipating, cyclic steady state. The kinetic models now in use eventually need to be changed to correct disagreements with several recent studies. Diffusion of ions through open channels is very fast but involves many interactions of ions, pore, and solvent that lead to ionic selectivity, saturation, block, and flux coupling. Our description of the ionic fluxes can be improved by abandoning continuum models in favor of more structured ones. Problems to be solved include determining how many ions occupy a channel at once and what to be solved include determining how many ions occupy a channel at once and what kind of energy barriers they must cross in traversing the membrane. Ultimately we will need to know the chemical structure of the whole system to understand how it functions. PMID:656545

  9. Emotional/Behavioral Difficulties and Mental Health Service Contacts of Students in Special Education for Non-Mental Health Problems

    ERIC Educational Resources Information Center

    Pastor, Patricia N.; Reuben, Cynthia A.

    2009-01-01

    Background: Emotional/behavioral difficulties and mental health (MH) service contacts of 3 groups of youth were compared: students in special education for non-MH problems, students in special education for MH problems, and youth not in special education. Methods: Parents reported the characteristics, special education placement,…

  10. Historical origins of current problems in cancer control

    PubMed Central

    Hayter, C R

    1998-01-01

    Canada's provinces have some of the most highly developed cancer control systems in the world, but the recent crisis in waiting times for radiotherapy has drawn attention to many weaknesses and inadequacies. Focusing on the province with the largest cancer control system, Ontario, this paper explores the historical origins of current problems in cancer control and shows that they are directly related to policy decisions made in the early years of the system. The development of cancer control in Ontario from the 1920s to the present is outlined, and the historical origins of 3 specific problems related to patient care are discussed: fragmentation of care, which has resulted from an emphasis on radiotherapy rather than comprehensive care and from tensions between the medical profession and government; variation in practice, which can be traced to the empirical origin of much cancer treatment and the slow implementation of research programs; and inequitable access to care, which can be attributed to the emphasis on geographic centralization of services. Attempts to reform Ontario's cancer control system are unlikely to be successful unless these fundamental issues are recognized and addressed. PMID:9676551

  11. Total shoulder arthroplasty -- current problems and possible solutions.

    PubMed

    Skirving, A P

    1999-01-01

    The concept and design of a cemented unconstrained total shoulder arthroplasty (TSA), introduced by Charles Neer II 25 years ago, has been successful in the management of degenerative and inflammatory conditions of the shoulder, controlling pain and, in many patients, significantly improving function. The clinical outcome is very much determined by the nature and severity of the pathology, as well as by the surgeon's experience and ability to correctly locate and fix the components. Total shoulder arthroplasty is a technically difficult procedure with perhaps a greater potential for technical errors and complications compared with other commonly performed arthroplasties. Current systems are modular on the humeral side, with varying head diameters and neck lengths, allowing more accurate coverage of the cut surface of the humeral neck and improved ability to establish the position of the joint line within the requirements of correct soft tissue tension and balance. Cemented all-polyethylene glenoid components remain the most favored, but the majority now have an increased radius of curvature compared with their corresponding humeral head, to allow translation during movement. Aseptic glenoid component loosening is the most frequently encountered long-term complication and is hastened by conforming prostheses, incorrect positioning, rotator cuff tears, and capsular contractures, but is protected by secure glenoid fixation. Cemented one-piece metal-backed glenoids have been disappointing, but non-cemented glenoids are being trialed with promising early results, although they have introduced their own particular problems of rapid polyethylene wear and component dissociation. Although cemented humeral components have a very low incidence of symptomatic loosening, most surgeons currently use press-fit designs supplemented with metaphyseal porous coating for osseous integration. Based on increased understanding of the morphology of the upper humerus, current designs are

  12. Theory of Cooper-pair mass spectroscopy by the current-induced contact-potential difference

    SciTech Connect

    Mishonov, T.M. )

    1994-08-01

    The creation of contactless Cooper-pair mass spectroscopy based on the Bernoulli-Venturi effect in thin superconducting films is suggested. The preparation of layered metal-insulator-superconductor-type heterostructures and standard electronics are necessary for the realization of the method. Two electrodes are patterned from the metallic layer: a circle and concentric-ring electrode. The currents in the superconducting film are induced by a drive coil concentric to the electrodes. The Bernoulli potential of the charged Cooper-pair superfluid creates a measurable electric polarization of gate electrodes of this plane-capacitor device. The current-induced contact-potential difference is limited by the Ginzburg-Landau potential [minus][ital a][sub GL]([ital T])= 1/2[h bar][ital e][sup *][ital H][sub [ital c]2]([ital T])/[ital m][sup *][ital c]=[h bar][sup 2]/2[ital m][sup *][xi][sup 2]([ital T]). The additional charge of the polarized circular electrode has the same sign as the free charge carriers of the superconductor.

  13. Ohmic contact and space-charge-limited current in molybdenum oxide modified devices

    NASA Astrophysics Data System (ADS)

    Lü, Zhaoyue; Deng, Zhenbo; Zheng, Jianjie; Zou, Ye; Chen, Zheng; Xu, Denghui; Wang, Yongsheng

    2009-10-01

    The effect of indium-tin oxide (ITO) surface treatment on hole injection of devices with molybdenum oxide (MoO 3) as a buffer layer on ITO was studied. The Ohmic contact is formed at the metal/organic interface due to high work function of MoO 3. Hence, the current is due to space charge limited when ITO is positively biased. The hole mobility of N, N‧-bis-(1-napthyl)-N, N‧-diphenyl-1, 1‧biphenyl-4, 4‧-diamine (NPB) at various thicknesses (100-400 nm) has been estimated by using space-charge-limited current measurements. The hole mobility of NPB, 1.09×10 -5 cm 2/V s at 100 nm is smaller than the value of 1.52×10 -4 cm 2/V s at 400 nm at 0.8 MV/cm, which is caused by the interfacial trap states restricted by the surface interaction. The mobility is hardly changed with NPB thickness for the effect of interfacial trap states on mobility which can be negligible when the thickness is more than 300 nm.

  14. Power counting of contact-range currents in effective field theory.

    PubMed

    Valderrama, M Pavón; Phillips, D R

    2015-02-27

    We analyze the power counting of two-body currents in nuclear effective field theories (EFTs). We find that the existence of nonperturbative physics at low energies, which is manifest in the existence of the deuteron and the ^{1}S_{0} NN virtual bound state, combined with the appearance of singular potentials in versions of nuclear EFT that incorporate chiral symmetry, modifies the renormalization-group flow of the couplings associated with contact operators that involve nucleon-nucleon pairs and external fields. The order of these couplings is thereby enhanced with respect to the naive-dimensional-analysis estimate. Consequently, short-range currents enter at a lower order in the chiral EFT than has been appreciated up until now, and their impact on low-energy observables is concomitantly larger. We illustrate the changes in the power counting with a few low-energy processes involving external probes and few-nucleon systems, including electron-deuteron elastic scattering and radiative neutron capture by protons. PMID:25768760

  15. Deformation of contact surfaces in a vacuum interrupter after high-current interruptions

    NASA Astrophysics Data System (ADS)

    Wang, Haoran; Wang, Zhenxing; Zhou, Zhipeng; Jiang, Yanjun; Wang, Jianhua; Geng, Yingsan; Liu, Zhiyuan

    2016-08-01

    In a high-current interruption, the contact surface in a vacuum interrupter might be severely damaged by constricted vacuum arcs causing a molten area on it. As a result, a protrusion will be initiated by a transient recovery voltage after current zero, enhancing the local electric field and making breakdowns occur easier. The objective of this paper is to simulate the deformation process on the molten area under a high electric field by adopting the finite element method. A time-dependent Electrohydrodynamic model was established, and the liquid-gas interface was tracked by the level-set method. From the results, the liquid metal can be deformed to a Taylor cone if the applied electric field is above a critical value. This value is correlated to the initial geometry of the liquid metal, which increases as the size of the liquid metal decreases. Moreover, the buildup time of a Taylor cone obeys the power law t = k × E-3, where E is the initial electric field and k is a coefficient related to the material property, indicating a temporal self-similar characteristic. In addition, the influence of temperature has little impact on the deformation but has great impact on electron emission. Finally, the possible reason to initiate a delayed breakdown is associated with the deformation. The breakdown does not occur immediately when the voltage is just applied upon the gap but is postponed to several milliseconds later when the tip is formed on the liquid metal.

  16. The influence of small impurity additions and direct electric current on the kinetics of contact melting in metals

    NASA Astrophysics Data System (ADS)

    Ahkubekov, A. A.; Ahkubekova, S. N.; Enaldieva, O. L.; Orkvasov, T. A.; Sozaev, V. A.

    2008-02-01

    Using the experimental data on contact melting of polycrystalline indium, tin and lead - based solid solutions with low-melting alloys we show that besides the diffusive, adhesive and low - dimensional mechanisms of contact melting it is necessary to take into account the segregational mechanism as well. The surfaces of a contact between the polycrystalline solid solutions and low - melting metals enrich in lower melting components due to the grain-boundary and surface segregation. One can influence on the kinetics of contact melting using alkali metals as impurity additives and applying the direct electric current. For example, the sodium addition to indium results in 3 times expansion of contact layer in the (In + 0.1 at. % Na) - Bi system, but in 2 times shrinking of that layer in the (In + 0.1 at. % Na) - Cd system in comparison to experiments without impurities.

  17. Bifocal contact lenses: History, types, characteristics, and actual state and problems

    PubMed Central

    Toshida, Hiroshi; Takahashi, Kozo; Sado, Kazushige; Kanai, Atsushi; Murakami, Akira

    2008-01-01

    Since people who wear contact lenses (CL) often continue using CL even when they develop presbyopia, there are growing expectations for bifocal CL. To understand actual state and problems, history, types, and their characteristics are summarized in this review. Bifocal CL have a long history over 70 years. Recently, bifocal CL have achieved remarkable progress. However, there still is an impression that prescription of bifocal CL is not easy. It should also be remembered that bifocal CL have limits, including limited addition for near vision, as well as the effects of aging and eye diseases in the aged, such as dry eye, astigmatism, cataract, etc. Analysis of the long-term users of bifocal CL among our patients has revealed the disappearance of bifocal CL that achieved unsatisfactory vision and poor contrast compared with those provided by other types of CL. Changing the prescription up to 3 times for lenses of the same brand may be appropriate. Lenses that provide poor contrast sensitivity, suffer from glare, or give unsatisfactory vision have been weeded out. The repeated replacement of products due to the emergence of improved or new products will be guessed. PMID:19668441

  18. Grounding line dynamics inferred from a 3D full-Stokes model solving the contact problem

    NASA Astrophysics Data System (ADS)

    Favier, Lionel; Gagliardini, Olivier; Durand, Gael; Zwinger, Thomas

    2010-05-01

    The mass balance of marine ice-sheets, such as the West Antarctic Ice Sheet, is mostly controlled by their grounding line dynamics. Most numerical models simulating marine ice-sheets involve simplifications and do not include all the stress gradients. First results obtained with a 3D full-Stokes model for the grounded ice-sheet / floating ice-shelf transition, using the finite-element code Elmer/Ice, are presented. The initial geometry, which takes into account a dome and a calving front, has been laterally extruded from a previously investigated 2D flowline geometry. The grounding line migration is computed by solving the contact problem between the ice and the rigid downward sloping bedrock, where a non linear friction law is applied in the two horizontal directions. The evolutions of the sea-air and sea-ice interfaces are determined by the solution of a local transport equation. The consistency between the 3D model and the analogous results of the flowline model is shown by comparing the results in the basic extruded case, with no normal flux through lateral boundaries. Thereafter, spatially non uniform perturbations are introduced, to simulate the grounding line dynamics under fully three-dimensional perturbations.

  19. Experimental evidence of direct contact formation for the current transport in silver thick film metallized silicon emitters

    NASA Astrophysics Data System (ADS)

    Cabrera, Enrique; Olibet, Sara; Glatz-Reichenbach, Joachim; Kopecek, Radovan; Reinke, Daniel; Schubert, Gunnar

    2011-12-01

    Great advances have been achieved in the development of silver pastes. The use of smaller silver particles, higher silver content, and, thus, less glass frit allow modern silver pastes to contact high resistive emitters without the necessity of a selective emitter or subsequent plating. To identify the microscopic key reasons behind the improvement of silver paste, it is essential to understand the current transport mechanism from the silicon emitter into the bulk of the silver finger. Two current transport theories predominate: i) The current flows through the Ag crystallites grown into the Si emitter, which are separated by a thin glass layer or possibly in direct contact with the silver finger. ii) The current is transported by means of multistep tunneling into the silver finger across nano-Ag colloids in the glass layer, which are formed at optimal firing conditions; the formation of Ag crystallites into the Si surface is synonymous with over-firing. In this study, we contact Si solar cell emitters with different silver pastes on textured and flat silicon surfaces. A sequential selective silver-glass etching process is employed to expose and isolate the different contact components for current transport. The surface configurations after the etching sequences are observed with scanning electron microscopy. Liquid conductive silver is then applied to each sample and the contact resistivity is measured to determine the dominant microscopic conduction path system. We observe glass-free emitter areas at the tops of the pyramidal-textured Si that lead to the formation of direct contacts between the Ag crystallites grown into the Si emitter and the bulk of the silver finger. We present experimental evidence that the major current flow into the silver finger is through these direct contacts.

  20. Nonlinear time-series analysis of current signal in cathodic contact glow discharge electrolysis

    NASA Astrophysics Data System (ADS)

    Allagui, Anis; Rojas, Andrea Espinel; Bonny, Talal; Elwakil, Ahmed S.; Abdelkareem, Mohammad Ali

    2016-05-01

    In the standard two-electrode configuration employed in electrolytic process, when the control dc voltage is brought to a critical value, the system undergoes a transition from conventional electrolysis to contact glow discharge electrolysis (CGDE), which has also been referred to as liquid-submerged micro-plasma, glow discharge plasma electrolysis, electrode effect, electrolytic plasma, etc. The light-emitting process is associated with the development of an irregular and erratic current time-series which has been arbitrarily labelled as "random," and thus dissuaded further research in this direction. Here, we examine the current time-series signals measured in cathodic CGDE configuration in a concentrated KOH solution at different dc bias voltages greater than the critical voltage. We show that the signals are, in fact, not random according to the NIST SP. 800-22 test suite definition. We also demonstrate that post-processing low-pass filtered sequences requires less time than the native as-measured sequences, suggesting a superposition of low frequency chaotic fluctuations and high frequency behaviors (which may be produced by more than one possible source of entropy). Using an array of nonlinear time-series analyses for dynamical systems, i.e., the computation of largest Lyapunov exponents and correlation dimensions, and re-construction of phase portraits, we found that low-pass filtered datasets undergo a transition from quasi-periodic to chaotic to quasi-hyper-chaotic behavior, and back again to chaos when the voltage controlling-parameter is increased. The high frequency part of the signals is discussed in terms of highly nonlinear turbulent motion developed around the working electrode.

  1. Advanced Curation: Solving Current and Future Sample Return Problems

    NASA Technical Reports Server (NTRS)

    Fries, M.; Calaway, M.; Evans, C.; McCubbin, F.

    2015-01-01

    Advanced Curation is a wide-ranging and comprehensive research and development effort at NASA Johnson Space Center that identifies and remediates sample related issues. For current collections, Advanced Curation investigates new cleaning, verification, and analytical techniques to assess their suitability for improving curation processes. Specific needs are also assessed for future sample return missions. For each need, a written plan is drawn up to achieve the requirement. The plan draws while upon current Curation practices, input from Curators, the analytical expertise of the Astromaterials Research and Exploration Science (ARES) team, and suitable standards maintained by ISO, IEST, NIST and other institutions. Additionally, new technologies are adopted on the bases of need and availability. Implementation plans are tested using customized trial programs with statistically robust courses of measurement, and are iterated if necessary until an implementable protocol is established. Upcoming and potential NASA missions such as OSIRIS-REx, the Asteroid Retrieval Mission (ARM), sample return missions in the New Frontiers program, and Mars sample return (MSR) all feature new difficulties and specialized sample handling requirements. The Mars 2020 mission in particular poses a suite of challenges since the mission will cache martian samples for possible return to Earth. In anticipation of future MSR, the following problems are among those under investigation: What is the most efficient means to achieve the less than 1.0 ng/sq cm total organic carbon (TOC) cleanliness required for all sample handling hardware? How do we maintain and verify cleanliness at this level? The Mars 2020 Organic Contamination Panel (OCP) predicts that organic carbon, if present, will be present at the "one to tens" of ppb level in martian near-surface samples. The same samples will likely contain wt% perchlorate salts, or approximately 1,000,000x as much perchlorate oxidizer as organic carbon

  2. Current-phase relation and h /e -periodic critical current of a chiral Josephson contact between one-dimensional Majorana modes

    NASA Astrophysics Data System (ADS)

    Shapiro, Dmitriy S.; Shnirman, Alexander; Mirlin, Alexander D.

    2016-04-01

    We explore a long Josephson contact transporting Cooper pairs between one-dimensional (1D) charge-neutral chiral Majorana modes in the leads via charged Dirac chiral modes in the normal region. We investigate the regimes of (i) transparent contacts and (ii) tunnel junctions implemented in 3D topological insulator/superconductor/magnet hybrid structures. The setup acts as a SQUID controlled by the magnetic flux enclosed by the chiral loop of the normal region. This chirality leads to the fractional h /e -periodic pattern of critical current. The current-phase relation can have sawtoothlike shape with spikes at unusual even phases of 2 π n .

  3. Reduced leakage currents of CdZnTe radiation detectors with HgTe/HgCdTe superlattice contacts

    NASA Astrophysics Data System (ADS)

    Chang, Y.; Grein, C. H.; Becker, C. R.; Huang, J.; Ghosh, S.; Aqariden, F.; Sivananthan, S.

    2012-10-01

    Room-temperature-operating CdZnTe radiation detectors have high energy resolution, linear energy response and are capable of operating in normal counting and spectroscopic modes, hence are highly desirable for medical diagnosis, nondestructive industrial evaluations, homeland security, counterterrorism inspections and nuclear proliferation detection to ensure national and international nuclear safety. HgTe/HgCdTe superlattices can be designed to selectively transport one carrier species while hindering transport of the other. Specifically, one designs a large carrier effective mass for undesired carriers in the electric field direction, which results in low carrier velocities, and yet a density of states for undesired carrier that is lower than that of a comparable bulk semiconductor, which results in low carrier concentrations, hence a low current density under an electric field. The opposite carrier species can be designed to have a large velocity and high density of states, hence producing a large current density. By employing HgTe/HgCdTe superlattices as contact layers intermediate between CdZnTe absorbers and metal contacts, leakage currents under high electric fields are reduced and improved x-ray and γ-ray detector performance is anticipated. Pixilated CdZnTe radiation detectors arrays were fabricated and characterized to evaluate the effectiveness of HgTe/HgCdTe superlattices in reducing leakage currents. Current-voltage characteristics show that HgTe/HgCdTe superlattice contact layers consistently result in significantly reduced leakage currents relative to detectors with only metal contacts.

  4. Contact Precautions for Multidrug-Resistant Organisms (MDROs): Current Recommendations and Actual Practice

    PubMed Central

    Clock, Sarah A.; Cohen, Bevin; Behta, Maryam; Ross, Barbara; Larson, Elaine L.

    2009-01-01

    Background Contact precautions are recommended for interactions with patients colonized/infected with multidrug-resistant organisms; however, rates of contact precautions practice are unknown. Methods Observers recorded the availability of supplies and staff/visitor adherence to contact precautions at rooms of patients indicated for contact precautions. Data were collected at three sites in a New York City hospital network. Results Contact precautions signs were present for 85.4% of indicated patients. The largest proportions were indicated for isolation for vancomycin-resistant enterococci and methicillin-resistant Staphylococcus aureus cultures. Isolation carts were available outside 93.7-96.7% of rooms displaying signs, and personal protective equipment was available at rates of 49.4-72.1% for gloves (all sizes: small, medium, and large) and 91.7-95.2% for gowns. Overall adherence rates upon room entry and exit, respectively, were 19.4% and 48.4% for hand hygiene, 67.5% and 63.5% for gloves, and 67.9% and 77.1% for gowns. Adherence was significantly better in intensive care units (p<0.05) and by patient-care staff (p<0.05), and patient-care staff compliance with one contact precautions behavior was predictive of adherence to additional behaviors (p<0.001). Conclusions Our findings support the recommendation that methods to monitor contact precautions and identify and correct non-adherent practices should be a standard component of infection prevention and control programs. PMID:19913329

  5. Some Current Problems in Simulator Design, Testing and Use.

    ERIC Educational Resources Information Center

    Caro, Paul W.

    Concerned with the general problem of the effectiveness of simulator training, this report reflects information developed during the conduct of aircraft simulator training research projects sponsored by the Air Force, Army, Navy, and Coast Guard. Problems are identified related to simulator design, testing, and use, all of which impact upon…

  6. Contact problem for an elastic reinforcement bonded to an elastic plate

    NASA Technical Reports Server (NTRS)

    Erdogan, F.; Civelek, M. B.

    1973-01-01

    The stiffening layer is treated as an elastic membrane and the base plate is assumed to be an elastic continuum. The bonding between the two materials is assumed to be either one of direct adhesion ro through a thin adhesive layer which is treated as a shear spring. The solution for the simple case in which both the stiffener and the base plate are treated as membranes is also given. The contact stress is obtained for a series of numerical examples. In the direct adhesion case the contact stress becomes infinite at the stiffener ends with a typical square root singularity for the continuum model, and behaving as a delta function for the membrane model. In the case of bonding through an adhesive layer the contact stress becomes finite and continuous along the entire contact area.

  7. Acanthamoeba keratitis in Tennessee: a growing problem in patients wearing contact lenses.

    PubMed

    Johns, K J; Parrish, C M; Seal, M R; Jerkins, G W; Berrie, W R; Litchford, D W; Sullivan, W R; Boone, J E; Elliott, J H; O'Day, D M

    1989-11-01

    All physicians evaluating a painful red eye in a contact lens wearer should consider the diagnosis of Acanthamoeba keratitis. Although it remains relatively rare, the incidence of this infection is on the rise. Clues to the correct diagnosis include a corneal abrasion that fails to heal appropriately, pain out of proportion to the clinical findings, and a history of poor contact lens hygiene. Prompt recognition and appropriate ophthalmologic intervention can improve the visual outcome for patients with this devastating corneal infection. PMID:2622154

  8. Differentiation of the functional in an optimization problem for diffusion and convective transfer coefficients of elliptic imperfect contact interface problems

    NASA Astrophysics Data System (ADS)

    Manapova, Aigul

    2016-08-01

    We consider optimal control problems for second order elliptic equations with non-self-adjoint operators-convection-diffusion problems. Control processes are described by semi-linear convection-diffusion equation with discontinuous data and solutions (states) subject to the boundary interface conditions of imperfect type (i.e., problems with a jump of the coefficients and the solution on the interface; the jump of the solution is proportional to the normal component of the flux). Controls are involved in the coefficients of diffusion and convective transfer. We prove differentiability and Lipshitz continuity of the cost functional, depending on a state of the system and a control. The calculation of the gradients uses the numerical solutions of direct problems for the state and adjoint problems.

  9. Au nanoparticles embedded at the interface of Al/4H-SiC Schottky contacts for current density enhancement

    NASA Astrophysics Data System (ADS)

    Gorji, Mohammad Saleh; Cheong, Kuan Yew

    2015-01-01

    Nanostructured contacts, comprised of nanoparticles (NPs) embedded at the interface of contact/semiconductor, offer a viable solution in modification of Schottky barrier height (SBH) in Schottky contacts. The successful performance of devices with such nanostructured contacts requires a feasible selection of NPs/contact material based on theoretical calculations and a cost effective and reproducible route for NPs deposition. Acidification of commercially available colloidal Au NPs solution by HF has been selected here as a simple bench-top technique for deposition of Au NPs on n- and p-type 4H-SiC substrates. Theoretical calculations based on the model of inhomogeneity in SBH (ISBH) were used to make a more appropriate selection of NPs type (Au) and size (5 and 10 nm, diameter) with respect to contact metal (Al). Al/Au NPs/SiC Schottky barrier diodes were then fabricated, and their electrical characteristics exhibited current density enhancement due to the SBH lowering. The source of SBH lowering was determined to be the local electric field enhancement due to NPs effect, which was further investigated using the models of ISBH and tunneling enhancement at triple interface.

  10. An automatic contact algorithm in DYNA3D for impact problems

    SciTech Connect

    Whirley, R.G.; Engelmann, B.E.

    1993-07-23

    This paper presents a new approach for the automatic definition and treatment of mechanical contact in explicit nonlinear finite element analysis. Automatic contact offers the benefits of significantly reduced model construction time and fewer opportunities for user error, but faces significant challenges in reliability and computational costs. Key aspects of the proposed new method include automatic identification of adjacent and opposite surfaces in the global search phase, and the use of a well-defined surface normal which allows a consistent treatment of shell intersection and corner contact conditions without a ad-hoc rules. The paper concludes with three examples which illustrate the performance of the newly proposed algorithm in the public DYNA3D code.

  11. Observation of current polarity effect in stressing as-formed sub-micron Al-Si-Cu/TiW/TiSi 2 contacts

    NASA Astrophysics Data System (ADS)

    Chen, Li-Zen; Hsu, Klaus Y.-J.

    1999-06-01

    Formation of good silicide contacts becomes more important but difficult as the contact size continues shrinking toward the deep sub-micron regime. At the same time, higher current density, which may easily appear in small regions, could pose strong impact to the long-term reliability of sub-micron contacts. In this work, high current density stress experiments were conducted on the Al-Si-Cu/TiW/TiSi 2 contacts with the size ranging from 0.5×0.5 μm 2 down to 0.25×0.25 μm 2. The self-aligned silicide contacts were formed by using collimated sputtering, E-beam lithography, RTA, and RIE techniques. The silicide contacts were sintered at 400°C for 30 min. Cross-bridge Kelvin resistor structures were formed for electrical stressing and contact resistance measurement. One-way and two-way stressings were performed at high current density (˜10 7 A/cm 2) and the contact resistance was measured periodically at low current density during the stressing to monitor the evolution. It was found that the initial resistance of as-formed contacts was higher than expected. This is probably due to the difficulty of forming good interfaces in the small contact region by sputtering and that the sintering temperature may not be high enough to smear out the imperfection. The stressing was found to anneal the contacts. With electrons flowing from metal layer into the contact window, the contact resistance was reduced more efficiently than with reverse current of the same density. Stressed first by reverse current then by normal current, the resistance showed a two-step reduction with a significant transition at the switch of current polarity. For prolonged stressing, the contacts were gradually degraded and the reverse current induced more severe damage. These observations indicate strong electromigration effect at the small contacts.

  12. CHAPTER 10: CURRENT TECHNICAL PROBLEMS IN EMERGY ANALYSIS

    EPA Science Inventory

    Technical problems related to the determination of the emergy base for self-organization in environmental systems are considered in this paper. The comparability of emergy analysis results depends on emergy analysts making similar choices in determining the emergy base for a part...

  13. Differential Item Functioning (DIF): Current Problems and Future Directions

    ERIC Educational Resources Information Center

    Karami, Hossein; Salmani Nodoushan, Mohammad Ali

    2011-01-01

    With the rising concerns over the fairness of language tests, Differential Item Functioning (DIF) has been increasingly applied in bias analysis. Despite its widespread use in psychometric circles, DIF is facing a number of serious problems. This paper is an attempt to shed light on a number of the issues involved in DIF analysis. Specifically,…

  14. Current State and Problems of Higher Education Reform

    ERIC Educational Resources Information Center

    Salnikov, N.; Burukhin, S.

    2009-01-01

    Higher education in Russia is experiencing changes in curriculum and in the specialization and function of institutions in the search for a better model for a post-Soviet society. The early 1990s saw the start of the reform of the system of education in Russia. However, problems of quality and of continuity with secondary education have still not…

  15. Study of semitransparent palladium contacts on mercuric iodide by photoluminescence spectroscopy and thermally stimulated current measurements

    NASA Astrophysics Data System (ADS)

    Bao, X. J.; Schlesinger, T. E.; James, R. B.; Gentry, G. L.; Cheng, A. Y.; Ortale, C.

    1991-04-01

    Semitransparent palladium contacts on mercuric iodide were studied by low temperature photoluminescence spectroscopy and thermally stimulated conductivity. These contacts were deposited either by thermal evaporation or by plasma sputtering. Changes due to palladium deposition were found in the photoluminescence spectra and were attributed to modifications in the stoichiometry within the palladium/mercuric iodide interfacial region. Thermally stimulated conductivity measurements revealed two dominant traps with activation energies of 0.010 and 0.54 eV. The importance of these traps in the application of nuclear detection is discussed.

  16. On the distinguished limits of the Navier slip model of the moving contact line problem

    NASA Astrophysics Data System (ADS)

    Ren, Weiqing; Trinh, Philippe H.; E, Weinan

    2015-06-01

    When a droplet spreads on a solid substrate, it is unclear what are the correct boundary conditions to impose at the moving contact line. The classical no-slip condition is generally acknowledged to lead to a non-integrable singularity at the moving contact line, for which a slip condition, associated with a small slip parameter, $\\lambda$, serves to alleviate. In this paper, we discuss what occurs as the slip parameter, $\\lambda$, tends to zero. In particular, we explain how the zero-slip limit should be discussed in consideration of two distinguished:: one where time is held constant $t = O(1)$, and one where time tends to infinity at the rate $t = O(|\\log \\lambda|)$. The crucial result is that in the case where time is held constant, the $\\lambda \\to 0$ limit converges to the slip-free equation, and contact line slippage occurs as a regular perturbative effect. However, if $\\lambda \\to 0$ and $t \\to \\infty$, then contact line slippage is a leading-order singular effect.

  17. Spin-polarized currents in the tunnel contact of a normal conductor and a two-dimensional topological insulator

    SciTech Connect

    Sukhanov, A. A. Sablikov, V. A.

    2013-11-15

    The spin filtering of electrons tunneling from the edge states of a two-dimensional topological insulator into a normal conductor under a magnetic field (external or induced due to proximity to a magnetic insulator) is studied. Calculations are performed for a tunnel contact of finite length between the topological insulator and an electronic multimode quantum strip. It is shown that the flow of tunneling electrons is split in the strip, so that spin-polarized currents arise in its left and right branches. These currents can be effectively controlled by the contact voltage and the chemical potential of the system. The presence of a magnetic field, which splits the spin subbands of the electron spectrum in the strip, gives rise to switching of the spin current between the strip branches.

  18. Asymmetrically contacted germanium photodiode using a metal-interlayer-semiconductor-metal structure for extremely large dark current suppression.

    PubMed

    Zang, Hwan-Jun; Kim, Gwang-Sik; Park, Gil-Jae; Choi, Yong-Soo; Yu, Hyun-Yong

    2016-08-15

    In this study, we proposed germanium (Ge) metal-interlayer-semiconductor-metal (MISM) photodiodes (PD), with an anode of a metal-interlayer-semiconductor (MIS) contact and a cathode of a metal-semiconductor (MS) contact, to efficiently suppress the dark current of Ge PD. We selected titanium dioxide (TiO2) as an interlayer material for the MIS contact, due to its large valence band offset and negative conduction band offset to Ge. We significantly suppress the dark current of Ge PD by introducing the MISM structure with a TiO2 interlayer, as this enhances the hole Schottky barrier height, and thus acts as a large barrier for holes. In addition, it collects photo-generated carriers without degradation, due to its negative conduction band offset to Ge. This reduces the dark current of Ge MISM PDs by ×8000 for 7-nm-thick TiO2 interlayer, while its photo current is still comparable to that of Ge metal-semiconductor-metal (MSM) PDs. Furthermore, the proposed Ge PD shows ×6,600 improvement of the normalized photo-to-dark-current ratio (NPDR) at a wavelength of 1.55 μm. The proposed Ge MISM PD shows considerable promise for low power and high sensitivity Ge-based optoelectronic applications. PMID:27519063

  19. Scale bridging in molecular simulation. Recurrent problems and current options

    NASA Astrophysics Data System (ADS)

    Hartmann, Carsten; Delle Site, Luigi

    2015-09-01

    Multiscale and multiphysics approaches have become an integral part of the molecular modeling and simulation toolbox and are used to attack various real-world problems that would be out of reach without these techniques. This special topics issue is devoted to a critical appraisal of some of the most popular scale bridging techniques for molecular simulation. It features regular articles and a "Discussion and Debate" section, in which experts in the field discuss specific articles and general aspects of scale bridging techniques.

  20. Eddy-current NDE inverse problem with sparse grid algorithm

    NASA Astrophysics Data System (ADS)

    Zhou, Liming; Sabbagh, Harold A.; Sabbagh, Elias H.; Murphy, R. Kim; Bernacchi, William; Aldrin, John C.; Forsyth, David; Lindgren, Eric

    2016-02-01

    In model-based inverse problems, the unknown parameters (such as length, width, depth) need to be estimated. When the unknown parameters are few, the conventional mathematical methods are suitable. But the increasing number of unknown parameters will make the computation become heavy. To reduce the burden of computation, the sparse grid algorithm was used in our work. As a result, we obtain a powerful interpolation method that requires significantly fewer support nodes than conventional interpolation on a full grid.

  1. Unsolved problems in biology--The state of current thinking.

    PubMed

    Dev, Sukhendu B

    2015-03-01

    Many outstanding problems have been solved in biology and medicine for which scientists have been awarded prestigious prizes including the Nobel Prize, Lasker Award and Breakthrough Prizes in life sciences. These have been the fruits of years of basic research. From time to time, publications have appeared listing "unsolved" problems in biology. In this article, I ask the question whether it is possible to have such a list, if not a unique one, at least one that is analogous to the Millennium Prize in mathematics. My approach to finding an answer to this question was to gather views of leading biologists. I have also included my own views. Analysis of all the responses received over several years has convinced me that it is difficult, but not impossible, to have such a prize. Biology is complex and very interdisciplinary these days at times involving large numbers of teams, unlike mathematics, where Andrew Wiles spent seven years in complete isolation and secrecy solving Fermat's last theorem. Such an approach is simply not possible in biology. Still I would like to suggest that a similar prize can be established by a panel of distinguished scientists. It would be awarded to those who solved one of the listed problems in biology that warrant a verifiable solution. Despite many different opinions, I found that there is some commonality in the responses I received - I go on to discuss what these are and how they may impact future thinking. PMID:25687284

  2. Taxation of Fringe Benefits: Alternative Approaches to Current Problems.

    ERIC Educational Resources Information Center

    Cohen, Anita E.

    1979-01-01

    The current IRS tax treatment of fringe benefits is seen as inadequate, and the judicial precept confusing, because groups of employee benefits are inappropriately excluded from taxation as perquisites. A tax equalization approach is proposed. Available from Suffolk University Law Review Office, 41 Temple St., Boston, MA 02114. (MSE)

  3. Transient three-dimensional contact problems: mortar method. Mixed methods and conserving integration

    NASA Astrophysics Data System (ADS)

    Hesch, Christian; Betsch, Peter

    2011-10-01

    The present work deals with the development of an energy-momentum conserving method to unilateral contact constraints and is a direct continuation of a previous work (Hesch and Betsch in Comput Mech 2011, doi: 10.1007/s00466-011-0597-2) dealing with the NTS method. In this work, we introduce the mortar method and a newly developed segmentation process for the consistent integration of the contact interface. For the application of the energy-momentum approach to mortar constraints, we extend an approach based on a mixed formulation to the segment definition of the mortar constraints. The enhanced numerical stability of the newly proposed discretization method will be shown in several examples.

  4. Reconsidering sore throats. Part I: Problems with current clinical practice.

    PubMed Central

    McIsaac, W. J.; Goel, V.; Slaughter, P. M.; Parsons, G. W.; Woolnough, K. V.; Weir, P. T.; Ennet, J. R.

    1997-01-01

    OBJECTIVE: To provide evidence-based answers to clinical questions posed by family physicians about Group A streptococcus pharyngitis and to further understanding of why management is controversial. QUALITY OF EVIDENCE: Evidence from randomized trials was not found for most questions. The most critical information came from high-quality community prevalence studies and criterion standard studies of physician clinical judgement. MAIN FINDINGS: Expert recommendations for physician management are not likely to help prevent rheumatic fever, as most people with sore throats do not seek medical care. Current clinical practices result in overuse of antibiotics because accuracy of clinical judgment is limited. CONCLUSIONS: Costs associated with visits for upper respiratory infections as well as increasing antibiotic resistance necessitate reconsidering the current clinical approach. An alternative management strategy is presented in part 2. PMID:9116520

  5. Human body impedance and threshold currents for perception and pain for contact hazard analysis in the VLF-MF band

    SciTech Connect

    Chatterjee, I.; Wu, D.; Gandhi, O.P.

    1986-05-01

    The body impedance and threshold currents needed to produce sensations of perception and pain have been measured for 367 human subjects for the frequency range 10 kHz to 3 MHz. A sufficient number of subjects (197 male and 170 female subjects of ages between 18 and 70 years) were utilized in the study to make valid statistical predictions for the general adult population. Various types of contact with metallic electrodes were used to simulate the situation where a human being would be in contact with a large metallic object (car, van, school bus, etc.) in an electromagnetic field in the VLF to MF band. Based on these measurements, it is speculated that the body impedance of a human being is inversely proportional to the body dimensions and the threshold current for perception is directly proportional to the square of the body dimensions. Predictions are made, based on scaling, for the corresponding threshold values for ten-year-old children. The average measured impedance and threshold current values are used to calculate threshold electric fields required to produce sensations of perception and pain in humans in contact with these vehicles. It is concluded from these calculations that many situations can exist in which the present ANSI (American National Standards Institute) recommended standard of 632 V/m for the frequency band 0.3-3 MHz is too high. The usefulness of safety devices like electrical safety shoes and gloves has been evaluated and it is concluded that they offer adequate protection from VLF to MF currents only up to a frequency of 1 MHz and 3 MHz, respectively. The current flowing through the hand of a human in conductive contact with the handle of an ungrounded van is shown to be as high as 879 mA and produces a local SAR in the wrist of about 1045 W/kg.

  6. Captive breeding of pangolins: current status, problems and future prospects

    PubMed Central

    Hua, Liushuai; Gong, Shiping; Wang, Fumin; Li, Weiye; Ge, Yan; Li, Xiaonan; Hou, Fanghui

    2015-01-01

    Abstract Pangolins are unique placental mammals with eight species existing in the world, which have adapted to a highly specialized diet of ants and termites, and are of significance in the control of forest termite disaster. Besides their ecological value, pangolins are extremely important economic animals with the value as medicine and food. At present, illegal hunting and habitat destruction have drastically decreased the wild population of pangolins, pushing them to the edge of extinction. Captive breeding is an important way to protect these species, but because of pangolin’s specialized behaviors and high dependence on natural ecosystem, there still exist many technical barriers to successful captive breeding programs. In this paper, based on the literatures and our practical experience, we reviewed the status and existing problems in captive breeding of pangolins, including four aspects, the naturalistic habitat, dietary husbandry, reproduction and disease control. Some recommendations are presented for effective captive breeding and protection of pangolins. PMID:26155072

  7. Management of Energy and Environment Conservation: Current Methodical Problems

    NASA Astrophysics Data System (ADS)

    Michna, J.; Ekmanis, J.; Zeltins, N.; Zebergs, V.; Siemianowicz, J.

    2011-01-01

    The paper presents a continuation in the series of works devoted to the acute problems of energy use management in different periods of economic transition in the CEE countries. Research carried out by the team of scientists has resulted in creation of modern management methods. In particular, unitary indices were worked out which connect the consumption of energy carriers and environment pollutions in a definite time period and the values of production (services) realised in this period. The cooperation of researchers from different countries has given rise to the ICEEP (International Center of Energy and Environment Policy), where under research are issues of the risk management in the conditions of informational uncertainty, non-knowledge, as well as dynamic and stochastic behaviour of systems (processes). The main emphasis in the methodical approaches is given to the complex (strategic) thinking, which would be necessary for establishment of global regulations in the scope of energy and environment conservation.

  8. Captive breeding of pangolins: current status, problems and future prospects.

    PubMed

    Hua, Liushuai; Gong, Shiping; Wang, Fumin; Li, Weiye; Ge, Yan; Li, Xiaonan; Hou, Fanghui

    2015-01-01

    Pangolins are unique placental mammals with eight species existing in the world, which have adapted to a highly specialized diet of ants and termites, and are of significance in the control of forest termite disaster. Besides their ecological value, pangolins are extremely important economic animals with the value as medicine and food. At present, illegal hunting and habitat destruction have drastically decreased the wild population of pangolins, pushing them to the edge of extinction. Captive breeding is an important way to protect these species, but because of pangolin's specialized behaviors and high dependence on natural ecosystem, there still exist many technical barriers to successful captive breeding programs. In this paper, based on the literatures and our practical experience, we reviewed the status and existing problems in captive breeding of pangolins, including four aspects, the naturalistic habitat, dietary husbandry, reproduction and disease control. Some recommendations are presented for effective captive breeding and protection of pangolins. PMID:26155072

  9. Future of primary healthcare education: current problems and potential solutions.

    PubMed

    Lord, J

    2003-10-01

    This review examines the origins of primary care and the pressures currently faced in terms of patient expectation, regulation, accountability, and work force shortages. It recognises the appropriateness of adding to the burden in primary care further by the shift both of more services and more medical education from secondary care. Some conclusions are drawn concerning potential solutions including skill mix changes, centralisation of services, a change in attitudes to professional mistakes, increased protected development time, evidence based education, and academic, leadership, and feedback skills for general practitioners. Six recommendations are offered as a prescription for organisational and educational change. PMID:14612596

  10. A nonlinear inverse problem for the prediction of local thermal contact conductance in plate finned-tube heat exchangers

    NASA Astrophysics Data System (ADS)

    Huang, C.-H.; Hsu, G.-C.; Jang, J.-Y.

    A nonlinear inverse problem utilizing the Conjugate Gradient Method (CGM) of minimization is used successfully to estimate the temporally and circumferentially varying thermal contact conductance of a plate finned-tube heat exchanger by reading the simulated transient temperature measurement data from the thermocouples located on the plate. The thermal properties of the fin and tube are assumed to be functions of temperature, and this makes the problem nonlinear. It is assumed that no prior information is available on the functional form of the unknown thermal contact conductance in the present study, thus, it is classified as the function estimation in the inverse calculation. The accuracy of the inverse analysis is examined by using the simulated temperature measurements. Finally the inverse solutions with and without the consideration of temperature-dependent thermal properties are compared. Results show that when the nonlinear inverse calculations are performed an excellent estimation on the thermal contact conductance can be obtained with any arbitrary initial guesses within a couple of minute's CPU time on a HP-730 workstation.

  11. Shift Work and Health: Current Problems and Preventive Actions

    PubMed Central

    2010-01-01

    The paper gives an overview of the problems to be tackled nowadays by occupational health with regards to shift work as well as the main guidelines at organizational and medical levels on how to protect workers' health and well-being. Working time organization is becoming a key factor on account of new technologies, market globalization, economic competition, and extension of social services to general populations, all of which involve more and more people in continuous assistance and control of work processes over the 24 hours in a day. The large increase of epidemiological and clinical studies on this issue document the severity of this risk factor on human health and well being, at both social and psychophysical levels, starting from a disruption of biological circadian rhythms and sleep/wake cycle and ending in several psychosomatic troubles and disorders, likely also including cancer, and extending to impairment of performance efficiency as well as family and social life. Appropriate interventions on the organization of shift schedules according to ergonomic criteria and careful health surveillance and social support for shift workers are important preventive and corrective measures that allow people to keep working without significant health impairment. PMID:22953171

  12. Shift work and health: current problems and preventive actions.

    PubMed

    Costa, Giovanni

    2010-12-01

    The paper gives an overview of the problems to be tackled nowadays by occupational health with regards to shift work as well as the main guidelines at organizational and medical levels on how to protect workers' health and well-being. Working time organization is becoming a key factor on account of new technologies, market globalization, economic competition, and extension of social services to general populations, all of which involve more and more people in continuous assistance and control of work processes over the 24 hours in a day. The large increase of epidemiological and clinical studies on this issue document the severity of this risk factor on human health and well being, at both social and psychophysical levels, starting from a disruption of biological circadian rhythms and sleep/wake cycle and ending in several psychosomatic troubles and disorders, likely also including cancer, and extending to impairment of performance efficiency as well as family and social life. Appropriate interventions on the organization of shift schedules according to ergonomic criteria and careful health surveillance and social support for shift workers are important preventive and corrective measures that allow people to keep working without significant health impairment. PMID:22953171

  13. Motion of high-current vacuum arcs on spiral-type contacts

    SciTech Connect

    Dullni, E. )

    1989-12-01

    Motion of vacuum arcs on spiral-type contacts is not only controlled by self-induced magnetic fields, but also by heating phenomena. In this paper, an expression is derived which enables the calculation of the speed of the arc from a computation of the time needed to heat the surface up to boiling temperature. Heat flux density of the constricted arc at the anode is required as input for the calculation. Good coincidence is achieved with experimental data. The speed of the arc varies from 5 to 400 m/s depending upon experimental conditions.

  14. Sleep medicine in Saudi Arabia: Current problems and future challenges

    PubMed Central

    BaHammam, Ahmed S.

    2011-01-01

    Sleep medicine is a relatively new specialty in the medical community. The practice of sleep medicine in Saudi Arabia (KSA) began in the mid to late nineties. Since its inception, the specialty has grown, and the number of specialists has increased. Nevertheless, sleep medicine is still underdeveloped in the KSA, particularly in the areas of clinical service, education, training and research. Based on available data, it appears that sleep disorders are prevalent among Saudis, and the demand for sleep medicine service is expected to rise significantly in the near future. A number of obstacles have been defined that hinder the progress of the specialty, including a lack of trained technicians, specialists and funding. Awareness about sleep disorders and their serious consequences is low among health care workers, health care authorities, insurance companies and the general public. A major challenge for the future is penetrating the educational system at all levels to demonstrate the high prevalence and serious consequences of sleep disorders. To attain adequate numbers of staff and facilities, the education and training of health care professionals at the level of sleep medicine specialists and sleep technologists is another important challenge that faces the specialty. This review discusses the current position of sleep medicine as a specialty in the KSA and the expected challenges of the future. In addition, it will guide clinicians interested in setting up new sleep medicine services in the KSA or other developing countries through the potential obstacles that may face them in this endeavor. PMID:21264164

  15. Technologies for Continuous Glucose Monitoring: Current Problems and Future Promises

    PubMed Central

    Vaddiraju, Santhisagar; Burgess, Diane J; Tomazos, Ioannis; Jain, Faquir C; Papadimitrakopoulos, Fotios

    2010-01-01

    Devices for continuous glucose monitoring (CGM) are currently a major focus of research in the area of diabetes management. It is envisioned that such devices will have the ability to alert a diabetes patient (or the parent or medical care giver of a diabetes patient) of impending hypoglycemic/hyperglycemic events and thereby enable the patient to avoid extreme hypoglycemic/hyperglycemic excursions as well as minimize deviations outside the normal glucose range, thus preventing both life-threatening events and the debilitating complications associated with diabetes. It is anticipated that CGM devices will utilize constant feedback of analytical information from a glucose sensor to activate an insulin delivery pump, thereby ultimately realizing the concept of an artificial pancreas. Depending on whether the CGM device penetrates/breaks the skin and/or the sample is measured extracorporeally, these devices can be categorized as totally invasive, minimally invasive, and noninvasive. In addition, CGM devices are further classified according to the transduction mechanisms used for glucose sensing (i.e., electrochemical, optical, and piezoelectric). However, at present, most of these technologies are plagued by a variety of issues that affect their accuracy and long-term performance. This article presents a critical comparison of existing CGM technologies, highlighting critical issues of device accuracy, foreign body response, calibration, and miniaturization. An outlook on future developments with an emphasis on long-term reliability and performance is also presented. PMID:21129353

  16. Ti/Pd/Ag Contacts to n-Type GaAs for High Current Density Devices

    NASA Astrophysics Data System (ADS)

    Huo, Pengyun; Rey-Stolle, Ignacio

    2016-06-01

    The metallization stack Ti/Pd/Ag on n-type Si has been readily used in solar cells due to its low metal/semiconductor specific contact resistance, very high sheet conductance, bondability, long-term durability, and cost-effectiveness. In this study, the use of Ti/Pd/Ag metallization on n-type GaAs is examined, targeting electronic devices that need to handle high current densities and with grid-like contacts with limited surface coverage (i.e., solar cells, lasers, or light emitting diodes). Ti/Pd/Ag (50 nm/50 nm/1000 nm) metal layers were deposited on n-type GaAs by electron beam evaporation and the contact quality was assessed for different doping levels (from 1.3 × 1018 cm-3 to 1.6 × 1019 cm-3) and annealing temperatures (from 300°C to 750°C). The metal/semiconductor specific contact resistance, metal resistivity, and the morphology of the contacts were studied. The results show that samples doped in the range of 1018 cm-3 had Schottky-like I- V characteristics and only samples doped 1.6 × 1019 cm-3 exhibited ohmic behavior even before annealing. For the ohmic contacts, increasing annealing temperature causes a decrease in the specific contact resistance ( ρ c,Ti/Pd/Ag ~ 5 × 10-4 Ω cm2). In regard to the metal resistivity, Ti/Pd/Ag metallization presents a very good metal conductivity for samples treated below 500°C ( ρ M,Ti/Pd/Ag ~ 2.3 × 10-6 Ω cm); however, for samples treated at 750°C, metal resistivity is strongly degraded due to morphological degradation and contamination in the silver overlayer. As compared to the classic AuGe/Ni/Au metal system, the Ti/Pd/Ag system shows higher metal/semiconductor specific contact resistance and one order of magnitude lower metal resistivity.

  17. Transition from stick to slip in Hertzian contact with ``Griffith'' friction: The Cattaneo-Mindlin problem revisited

    NASA Astrophysics Data System (ADS)

    Ciavarella, M.

    2015-11-01

    Classically, the transition from stick to slip is modelled with Amonton-Coulomb law, leading to the Cattaneo-Mindlin problem, which is amenable to quite general solutions using the idea of superposing normal contact pressure distributions - in particular superposing the full sliding component of shear with a corrective distribution in the stick region. However, faults model in geophysics and recent high-speed measurements of the real contact area and the strain fields in dry (nominally flat) rough interfaces at macroscopic but laboratory scale, all suggest that the transition from 'static' to 'dynamic' friction can be described, rather than by Coulomb law, by classical fracture mechanics singular solutions of shear cracks. Here, we introduce an 'adhesive' model for friction in a Hertzian spherical contact, maintaining the Hertzian solution for the normal pressures, but where the inception of slip is given by a Griffith condition. In the slip region, the standard Coulomb law continues to hold. This leads to a very simple solution for the Cattaneo-Mindlin problem, in which the "corrective" solution in the stick area is in fact similar to the mode II equivalent of a JKR singular solution for adhesive contact. The model departs from the standard Cattaneo-Mindlin solution, showing an increased size of the stick zone relative to the contact area, and a sudden transition to slip when the stick region reaches a critical size (the equivalent of the pull-off contact size of the JKR solution). The apparent static friction coefficient before sliding can be much higher than the sliding friction coefficient and, for a given friction fracture "energy", the process results in size and normal load dependence of the apparent static friction coefficient. Some qualitative agreement with Fineberg's group experiments for friction exists, namely the stick-slip boundary quasi-static prediction may correspond to the arrest of their slip "precursors", and the rapid collapse to global

  18. Chronic heart failure in the elderly: a current medical problem.

    PubMed

    Nessler, Jadwiga; Skrzypek, Agnieszka

    2008-10-01

    As a result of population ageing and improved medical care that contribute to better life expectancy, heart failure occurs more and more commonly in the elderly. In the USA approximately 80% of patients discharged from hospital with newly diagnosed heart failure are over 65 years of age, whereas 50% are over 75. The average 5-year mortality rate is about 50% in subjects with systolic dysfunction and similar in those with preserved left ventricular systolic function. Disorders of the cardiovascular system occurring in the elderly (e.g. increased left ventricular mass, myocardial rigidity, atrial fibrillation, decreased maximum oxygen uptake in cardiopulmonary exercise tests) result from the physiological ageing; they may also be caused by a concomitant cardiac failure syndrome. In the elderly, heart failure is often accompanied by concomitant conditions that often make diagnosis and treatment of chronic heart disease difficult. Non-specific clinical symptoms in the elderly as well as those associated with age (e.g. easy fatigability, exertional dyspnea) make a correct diagnosis difficult. The recognized biochemical marker of heart failure--brain natriuretic peptide, N-terminal pro-brain natriuretic peptide--has a limited diagnostic value in the elderly. Echocardiography plays a key role in the diagnosis. Owing to altered metabolism, impairment of hepatic processes to various degrees and decreased renal excretion of drugs, treatment requires attention, individual choice of drugs and doses, as well as periodic modification of both the doses and the intervals between them. Correct treatment improves quality of life and prolongs it. The aim of the present work is to present the differences in the pathophysiology, diagnostic evaluation and management of chronic heart failure in the elderly, in light of the current views and standards. PMID:19112819

  19. Defining the value of injection current and effective electrical contact area for EGaIn-based molecular tunneling junctions.

    PubMed

    Simeone, Felice C; Yoon, Hyo Jae; Thuo, Martin M; Barber, Jabulani R; Smith, Barbara; Whitesides, George M

    2013-12-01

    Analysis of rates of tunneling across self-assembled monolayers (SAMs) of n-alkanethiolates SCn (with n = number of carbon atoms) incorporated in junctions having structure Ag(TS)-SAM//Ga2O3/EGaIn leads to a value for the injection tunnel current density J0 (i.e., the current flowing through an ideal junction with n = 0) of 10(3.6±0.3) A·cm(-2) (V = +0.5 V). This estimation of J0 does not involve an extrapolation in length, because it was possible to measure current densities across SAMs over the range of lengths n = 1-18. This value of J0 is estimated under the assumption that values of the geometrical contact area equal the values of the effective electrical contact area. Detailed experimental analysis, however, indicates that the roughness of the Ga2O3 layer, and that of the Ag(TS)-SAM, determine values of the effective electrical contact area that are ~10(-4) the corresponding values of the geometrical contact area. Conversion of the values of geometrical contact area into the corresponding values of effective electrical contact area results in J0(+0.5 V) = 10(7.6±0.8) A·cm(-2), which is compatible with values reported for junctions using top-electrodes of evaporated Au, and graphene, and also comparable with values of J0 estimated from tunneling through single molecules. For these EGaIn-based junctions, the value of the tunneling decay factor β (β = 0.75 ± 0.02 Å(-1); β = 0.92 ± 0.02 nC(-1)) falls within the consensus range across different types of junctions (β = 0.73-0.89 Å(-1); β = 0.9-1.1 nC(-1)). A comparison of the characteristics of conical Ga2O3/EGaIn tips with the characteristics of other top-electrodes suggests that the EGaIn-based electrodes provide a particularly attractive technology for physical-organic studies of charge transport across SAMs. PMID:24187999

  20. Non-contact current and voltage sensor having detachable housing incorporating multiple ferrite cylinder portions

    DOEpatents

    Carpenter, Gary D.; El-Essawy, Wael; Ferreira, Alexandre Peixoto; Keller, Thomas Walter; Rubio, Juan C.; Schappert, Michael A.

    2016-04-26

    A detachable current and voltage sensor provides an isolated and convenient device to measure current passing through a conductor such as an AC branch circuit wire, as well as providing an indication of an electrostatic potential on the wire, which can be used to indicate the phase of the voltage on the wire, and optionally a magnitude of the voltage. The device includes a housing formed from two portions that mechanically close around the wire and that contain the current and voltage sensors. The current sensor is a ferrite cylinder formed from at least three portions that form the cylinder when the sensor is closed around the wire with a hall effect sensor disposed in a gap between two of the ferrite portions along the circumference to measure current. A capacitive plate or wire is disposed adjacent to, or within, the ferrite cylinder to provide the indication of the voltage.

  1. Geology and religion - historical perspective and current problems

    NASA Astrophysics Data System (ADS)

    Kölbl-Ebert, Martina

    2010-05-01

    Today, when referring to the relationship between geology and religion, people usually at once think of Christian (and other) fundamentalists and their chronic palaeontological illiteracy leading to Creationism, to Intelligent Design, and a distrust of science in general among them most prominently geology, palaeontology and evolutionary biology. Thus the relationship of geology and religion is usually considered to be under strain. In former times things used to be quite different, and for most of human history the observation of geological phenomena and the acquisition of geological expertise was intimately connected with religious ideas. The Judeo-Christian sense of a finite Earth history prepared the ground for accepting the Earth's different strata as testimony to the development of our globe through time. It was this religious, theological framework, from which the early geology started to evolve. However, with increasing observations there was a growing mismatch between what was expected according to ancient, scriptural authorities and the actual data. The release of geology from religious connotations or associations was a development closely connected with the Enlightenment, when geology and religion started to drift apart not with a violent rupture but in a subtle and sometimes circuitous manner. However, outside the group of people with geological expertise, not all was smooth and peaceful, and some conservative clergymen as well as laypersons were rather shocked by the new ideas that came with geology: the immensity of the timescale, a dynamic Earth, not just a ruin shaped by the Deluge, and a dynamic biology too with the Darwinian theory of evolution, which was founded in part on palaeontological evidence and the assumption of a long geological time scale. Nevertheless and interestingly the Creationism we face today is a rather recent phenomenon influenced by a number of motives, most of them philosophical and theological in nature. And so, the current

  2. General case of contact problems for a regular polygon weakened with full-strength hole

    NASA Astrophysics Data System (ADS)

    Odishelidze, Nana; Criado-Aldeanueva, Francisco; Criado, Francisco; Sanchez, Jose Maria

    2015-06-01

    The paper addresses a problem of plane elasticity theory for a doubly connected body whose external boundary is a regular polygon and the internal boundary is the required full-strength hole including the origin of coordinates. The full-strength hole is cycle symmetric. It is assumed that to every link of the broken line conforming the outer boundary of the given body are applied absolutely smooth rigid punches with rectilinear bases, which are under the action of the force P that applies to their middle points. There is no friction between the surface of the given elastic body and the punches. The uniformly distributed normal stress Q is applied to the hole boundary. Using the methods of complex analysis, the analytical image of Kolosov-Muskhelishvili's complex potentials (characterizing an elastic equilibrium of the body) and the shape of the hole's contour are determined under the condition that the tangential normal stress arising at it takes a constant value. A similar problem is considered for a square and an equilateral triangle, which are weakened with full-strength holes. Using the method developed here, the partially unknown boundary value problems under consideration is reduced to known boundary value problems of the theory of analytic functions. The solutions are presented in quadratures, and full-strength contours are constructed.

  3. Promoting Health by Addressing Basic Needs: Effect of Problem Resolution on Contacting Health Referrals

    ERIC Educational Resources Information Center

    Thompson, Tess; Kreuter, Matthew W.; Boyum, Sonia

    2016-01-01

    Members of vulnerable populations have heightened needs for health services. One advantage of integrating health risk assessment and referrals into social service assistance systems such as 2-1-1 is that such systems help callers resolve problems in other areas (e.g., housing). Callers to 2-1-1 in Missouri (N = 1,090) with at least one behavioral…

  4. Non-contact current and voltage sensing method using a clamshell housing and a ferrite cylinder

    DOEpatents

    Carpenter, Gary D.; El-Essawy, Wael; Ferreira, Alexandre Peixoto; Keller, Thomas Walter; Rubio, Juan C.; Schappert, Michael

    2016-04-26

    A method of measurement using a detachable current and voltage sensor provides an isolated and convenient technique for to measuring current passing through a conductor such as an AC branch circuit wire, as well as providing an indication of an electrostatic potential on the wire, which can be used to indicate the phase of the voltage on the wire, and optionally a magnitude of the voltage. The device includes a housing that contains the current and voltage sensors, which may be a ferrite cylinder with a hall effect sensor disposed in a gap along the circumference to measure current, or alternative a winding provided through the cylinder along its axis and a capacitive plate or wire disposed adjacent to, or within, the ferrite cylinder to provide the indication of the voltage.

  5. Effect of contact between a current collector and a polyacetylene electrode on electrochemical behavior in polyacetylene/lithium batteries

    NASA Astrophysics Data System (ADS)

    Chen, S.-A.; Chiou, Y.-C.

    1984-05-01

    Organic batteries with a polyacetylene film (PA) as the anode, a lithium strip as the cathode, and lithium perchlorate dissolved in propylene carbonate as the electrolyte are constructed. Charging and discharging characteristics of three batteries with different types of PA electrode are investigated. Type a PA electrode involves mechanical pressed contact of nickel gauze with the upper portion of the PA electrode; charging and discharging of the battery are difficult due to the semiconducting characteristic of the PA. Type b involves a PA film which has one side coated with a sputtered palladium (Pd) film; good contact of the Pd current collector with the PA electrode makes charging and discharging easily manageable. Type c involves an iodine-doped PA film; the battery is easily charged and discharged, but cleaning the surface of the lithium electrode is necessary after a few cycles.

  6. Inelastic electron-phonon scattering and excess current in superconducting point contacts with a short coherence length

    NASA Astrophysics Data System (ADS)

    Bobrov, N. L.

    2015-08-01

    Nonlinear electrical effects in superconducting S-c-S contacts, including the spectroscopy of electron-phonon interactions (EPI) in these systems, and the recovery of the EPI function from experimental data are discussed. The effect of a magnetic field on the current-voltage characteristics (I-V curves) and their derivatives for ErNi2B2C point contacts (PC) with d ≥ ξ (where d is the diameter of the PC and ξ is the coherence length) is studied. It is found that in zero magnetic fields and in near-critical fields, when the size of the superconducting gap can be neglected, the position of the peaks in dV/dI coincides with the peaks in the Yanson EPI spectra. In low fields the peaks are shifted toward lower energies and in intermediate fields, the peaks split. For PC with diameters greater than or on the order of the coherence length, the relative size of the negative phonon contribution to the excess current is considerably greater than in ballistic contacts. This leads to substantial suppression of the high-frequency peaks in the spectra for the superconducting state. In order to recover the EPI function from these spectra it is necessary to correct their intensities at high energies. For "dirty" NbSe2 and Nb point-contacts with d ≥ ξ, which have no phonon features in the second derivative of the I-V curve in the normal state, the EPI can be reconstructed from the superconducting state.

  7. Multiplicity of inhabited worlds and the problem of setting up contacts among them

    NASA Technical Reports Server (NTRS)

    Shklovskiy, I. S.

    1974-01-01

    The numerous planetary systems in our galaxy appear to a high degree of probability to contain some planets with a biosphere similar to earth' environment. The possibility of communicating with those extraterrestrial alien planetary civilizations centers on the high level of technological development that is required to overcome the problem of distance. It is conceivable that advanced civilizations can produce energy at a level of 10 to the 43rd power erg/year and that an artificial biosphere can be developed within the limits of 10 to the 22nd power to 10 to the 23rd power cm.

  8. A new solver for the elastic normal contact problem using conjugate gradients, deflation, and an FFT-based preconditioner

    NASA Astrophysics Data System (ADS)

    Vollebregt, E. A. H.

    2014-01-01

    This paper presents our new solver BCCG+FAI for solving elastic normal contact problems. This is a comprehensible approach that is based on the Conjugate Gradients (CG) algorithm and that uses FFTs. A first novel aspect is the definition of the “FFT-based Approximate Inverse” preconditioner. The underlying idea is that the inverse matrix can be approximated well using a Toeplitz or block-Toeplitz form, which can be computed using the FFT of the original matrix elements. This preconditioner makes the total number of CG iterations effectively constant in 2D and very slowly increasing in 3D problems. A second novelty is how we deal with a prescribed total force. This uses a deflation technique in such a way that CGs convergence and finite termination properties are maintained. Numerical results show that this solver is more effective than existing CG-based strategies, such that it can compete with Multi-Grid strategies over a much larger problem range. In our opinion it could be the new method of choice because of its simple structure and elegant theory, and because robust performance is achieved independently of any problem specific parameters.

  9. Which doctors and with what problems contact a specialist service for doctors? A cross sectional investigation

    PubMed Central

    Garelick, Antony I; Gross, Samantha R; Richardson, Irene; von der Tann, Matthias; Bland, Julia; Hale, Rob

    2007-01-01

    Background In the United Kingdom, specialist treatment and intervention services for doctors are underdeveloped. The MedNet programme, created in 1997 and funded by the London Deanery, aims to fill this gap by providing a self-referral, face-to-face, psychotherapeutic assessment service for doctors in London and South-East England. MedNet was designed to be a low-threshold service, targeting doctors without formal psychiatric problems. The aim of this study was to delineate the characteristics of doctors utilising the service, to describe their psychological morbidity, and to determine if early intervention is achieved. Methods A cross-sectional study including all consecutive self-referred doctors (n = 121, 50% male) presenting in 2002–2004 was conducted. Measures included standardised and bespoke questionnaires both self-report and clinician completed. The multi-dimensional evaluation included: demographics, CORE (CORE-OM, CORE-Workplace and CORE-A) an instrument designed to evaluate the psychological difficulties of patients referred to outpatient services, Brief Symptom Inventory to quantify caseness and formal psychiatric illness, and Maslach Burnout Inventory. Results The most prevalent presenting problems included depression, anxiety, interpersonal, self-esteem and work-related issues. However, only 9% of the cohort were identified as severely distressed psychiatrically using this measure. In approximately 50% of the sample, problems first presented in the preceding year. About 25% were on sick leave at the time of consultation, while 50% took little or no leave in the prior 12 months. A total of 42% were considered to be at some risk of suicide, with more than 25% considered to have a moderate to severe risk. There were no significant gender differences in type of morbidity, severity or days off sick. Conclusion Doctors displayed high levels of distress as reflected in the significant proportion of those who were at some risk of suicide; however, low

  10. Modeling of the anode surface deformation in high-current vacuum arcs with AMF contacts

    NASA Astrophysics Data System (ADS)

    Huang, Xiaolong; Wang, Lijun; Deng, Jie; Jia, Shenli; Qin, Kang; Shi, Zongqian

    2016-02-01

    A high-current vacuum arc subjected to an axial magnetic field is maintained in a diffuse status. With an increase in arc current, the energy carried by the arc column to the anode becomes larger and finally leads to the anode temperature exceeding the melting point of the anode material. When the anode melting pool is formed, and the rotational plasma of the arc column delivers its momentum to the melting pool, the anode melting pool starts to rotate and also flow outwards along the radial direction, which has been photographed by some researchers using high-speed cameras. In this paper, the anode temperature and melting status is calculated using the melting and solidification model. The swirl flow of the anode melting pool and deformation of the anode is calculated using the magneto-hydrodynamic (MHD) model with the volume of fraction (VOF) method. All the models are transient 2D axial-rotational symmetric models. The influence of the impaction force of the arc plasma, electromagnetic force, viscosity force, and surface tension of the liquid metal are all considered in the model. The heat flux density injected into the anode and the arc pressure are obtained from the 3D numerical simulation of the high-current vacuum arc using the MHD model, which gives more realistic parameters for the anode simulation. Simulation results show that the depth of the anode melting pool increases with an increase in the arc current. Some droplets sputter out from the anode surface, which is caused by the inertial centrifugal force of the rotational melting pool and strong plasma pressure. Compared with the previous anode melting model without consideration of anode deformation, when the deformation and swirl flow of the anode melting pool are considered, the anode temperature is relatively lower, and just a little more than the melting point of Cu. This is because of liquid droplets sputtering out of the anode surface taking much of the energy away from the anode surface. The

  11. Non-contact current-phase measurements of topological weak links with scanning SQUID

    NASA Astrophysics Data System (ADS)

    Watson, C. A.; Sochnikov, I.; Kirtley, J. R.; Moler, K. A.; Deng, M.; Chang, W.; Krogstrup, P.; Jespersen, T. S.; Nygard, J.; Marcus, C. M.; Maier, L.; Gould, C.; Tkachov, G.; Hankiewicz, E. M.; Brüne, C.; Buhmann, H.; Molenkamp, L. W.

    2015-03-01

    Topological superconductivity has recently generated substantial interest as a pathway to Majorana physics in the solid state. Experimental efforts have focused on the superconducting proximity effect in topologically non-trivial junctions, but proof of the topological nature of the induced superconductivity remains elusive. We employ scanning superconducting quantum interference device (SQUID) susceptometry to study conventional superconducting Nb rings interrupted by weak links of 3D topological insulator HgTe and Al rings with InAs nanowire junctions. Varying the flux through each ring, we directly measure the current-phase relation (CPR) of the junction. Forward skewness in the CPR of 3D-HgTe which persists even in junctions long compared to the mean free path suggests that helicity may play a role in the high transmittance of Andreev Bound States that carry the Josephson current. Progress in InAs nanowire junction CPR measurements is also discussed. These measurements showcase the CPR as a fundamental characteristic of superconducting weak links and establish scanning SQUID microscopy as a powerful probe for performing such measurements.

  12. An analytical solution of a one-dimensional thermal contact conductance problem with one heat flux and one insulated boundary condition

    SciTech Connect

    Tsai, Y.M.; Crane, R.A. )

    1992-05-01

    Heat transfer across surfaces in imperfect contact occurs in many practical situations. Since the thermal contact conductance problem has appeared in the literature, substantial efforts have been made to estimate the thermal conductance across the interface. Some of the techniques recently developed of estimating thermal contact conductance are based on experimental temperature data at one or several interior positions of the contacting solids and the calculation of the temperature at these locations for known contact conductance. Consequently, an accurate and efficient method for computing temperature distributions because quite important. FDM and FEM are most widely used. However, for most contact conductance computation methods, only the temperatures at the contacting regions and several other positions near the interface need to be determined, so the general FDM and FEM are not particularly efficient in solving this problem. This paper presents an analytical temperature distribution solution to the one-dimensional symmetric system with heat flux on one outside surface and insulation on the other. This analysis provides a theoretical basis for transient measurement of thermal contact conductance. While it is common practice in steady-state measurements to use a water-cooled heat sink, it is possible to limit the transient solution to time interval prior to any detectable temperature increase at the cold end. This effectively eliminates the need for water cooling and permits the use of an insulated boundary. The analytical solution to the mentioned problem obtained shows that for a symmetric system the temperature distribution solution includes two sets of distinct eigenfunctions.

  13. Stray neutral current problems and analysis associated with multiple ATS generator installations

    NASA Astrophysics Data System (ADS)

    Dunn, Samuel Douglas

    In generator installations where there is more than one 3-pole automatic-transfer-switch (ATS) on a 4-wire system, stray neutral currents and unwanted magnetic fields may arise. These stray currents and fields can cause a multitude of problems. Magnetic fields created by stray neutral currents can cause objectionable current on the conduit system. Objectionable current of this type can cause voltage rises on the grounding system. Geometries of stray neutral current paths can cause magnetic fields through areas of buildings that may cause problems with sensitive electronic equipment. Ground fault protection devices may detect incorrect ground fault condition. The presence of stray ground currents in multi-ATS installations is dependent on equipment selection and bonding connection points, whereas the magnitude of these currents depend on the system geometry, raceway size/types, and other factors. This paper looks at several stray neutral configurations tested in the Vanderbilt Power Laboratory.

  14. Non-contact ACL injuries in female athletes: an International Olympic Committee current concepts statement

    PubMed Central

    Renstrom, P; Ljungqvist, A; Arendt, E; Beynnon, B; Fukubayashi, T; Garrett, W; Georgoulis, T; Hewett, T E; Johnson, R; Krosshaug, T; Mandelbaum, B; Micheli, L; Myklebust, G; Roos, E; Roos, H; Schamasch, P; Shultz, S; Werner, S; Wojtys, E; Engebretsen, L

    2014-01-01

    The incidence of anterior cruciate ligament (ACL) injury remains high in young athletes. Because female athletes have a much higher incidence of ACL injuries in sports such as basketball and team handball than male athletes, the IOC Medical Commission invited a multidisciplinary group of ACL expert clinicians and scientists to (1) review current evidence including data from the new Scandinavian ACL registries; (2) critically evaluate high-quality studies of injury mechanics; (3) consider the key elements of successful prevention programmes; (4) summarise clinical management including surgery and conservative management; and (5) identify areas for further research. Risk factors for female athletes suffering ACL injury include: (1) being in the preovulatory phase of the menstrual cycle compared with the postovulatory phase; (2) having decreased intercondylar notch width on plain radiography; and (3) developing increased knee abduction moment (a valgus intersegmental torque) during impact on landing. Well-designed injury prevention programmes reduce the risk of ACL for athletes, particularly women. These programmes attempt to alter dynamic loading of the tibiofemoral joint through neuromuscular and proprioceptive training. They emphasise proper landing and cutting techniques. This includes landing softly on the forefoot and rolling back to the rearfoot, engaging knee and hip flexion and, where possible, landing on two feet. Players are trained to avoid excessive dynamic valgus of the knee and to focus on the “knee over toe position” when cutting. PMID:18539658

  15. Magnetotransport and current-induced spin transfer torque in a ferromagnetically contacted graphene.

    PubMed

    Zhou, Benhu; Chen, Xiongwen; Wang, Haiyan; Ding, Kai-He; Zhou, Guanghui

    2010-11-10

    We theoretically investigate the spin-dependent transport through a graphene sheet between two ferromagnetic (FM) leads with arbitrary polarization directions at low temperatures, where a magnetic insulator is deposited on the graphene to induce an exchange splitting between spin-up and spin-down carriers. By using standard nonequilibrium Green's function (NGF) techniques, it is demonstrated that the density of states (DOS) decreases for spin-up and increases for spin-down when the polarization strength of the two leads in parallel alignment increases. For the electron energy around the exchange splitting, the DOS for both spin-up and spin-down channels is independent of the polarization. In contrast, the conductance increases for spin-up but decreases for spin-down with an increase of the polarization. Interestingly, the magnitude of tunneling magnetoresistance (TMR) can be dramatically suppressed with the increase of the exchange splitting in graphene. Furthermore, the current-induced spin transfer torque (STT) dependence on the relative angle θ between the magnetic moments of the two leads shows a sine-like behavior and is enhanced with an increase of the polarization and/or the bias voltage. We attribute these spin-resolved effects to the breaking of the insulator-type properties of graphene with an exchange splitting between spin-up and spin-down carriers. PMID:21403343

  16. The Case of Web-Based Course on Taxation: Current Status, Problems and Future Improvement

    NASA Astrophysics Data System (ADS)

    Qin, Zhigang

    This paper mainly introduces the case of the web-based course on taxation developed by Xiamen University. We analyze the current status, problems and future improvement of the web-based course. The web-based course has the basic contents and modules, but it has several problems including unclear object, lacking interaction, lacking examination module, lacking study management module, and the learning materials and the navigation are too simple. According to its problems, we put forward the measures to improve it.

  17. Rotary electrical contact device and method for providing current to and/or from a rotating member

    DOEpatents

    Koplow, Jeffrey P

    2013-11-19

    Examples of rotary electrical connectors include a first pair and a second pair of opposing sheaves coupled together by intersecting first shaft connecting the first pair of opposing sheaves and a second shaft connecting the second pair of opposing sheaves, and at least partially electrically conductive belt disposed about respective perimeters of the first pair and second pair of opposing sheaves and adapted to remain in contact with at least a portion of the respective perimeters of the sheaves during motion of said sheaves. In example devices, one of the plurality of sheaves may remain stationary during operation of the device while the remaining sheaves rotate and/or orbit around a center axis of the stationary sheave, the device being configured to couple current between a stationary power source and a rotating member through the electrically conductive belt.

  18. The Current Often Implemented Fitness Tests in Physical Education Programs: Problems and Future Directions

    ERIC Educational Resources Information Center

    Keating, Xiaofen Deng

    2003-01-01

    This paper aims to examine current nationwide youth fitness test programs, address problems embedded in the programs, and possible solutions. The current Fitnessgram, President's Challenge, and YMCA youth fitness test programs were selected to represent nationwide youth fitness test programs. Sponsors of the nationwide youth fitness test programs…

  19. Solution of 3D inverse scattering problems by combined inverse equivalent current and finite element methods

    SciTech Connect

    Kılıç, Emre Eibert, Thomas F.

    2015-05-01

    An approach combining boundary integral and finite element methods is introduced for the solution of three-dimensional inverse electromagnetic medium scattering problems. Based on the equivalence principle, unknown equivalent electric and magnetic surface current densities on a closed surface are utilized to decompose the inverse medium problem into two parts: a linear radiation problem and a nonlinear cavity problem. The first problem is formulated by a boundary integral equation, the computational burden of which is reduced by employing the multilevel fast multipole method (MLFMM). Reconstructed Cauchy data on the surface allows the utilization of the Lorentz reciprocity and the Poynting's theorems. Exploiting these theorems, the noise level and an initial guess are estimated for the cavity problem. Moreover, it is possible to determine whether the material is lossy or not. In the second problem, the estimated surface currents form inhomogeneous boundary conditions of the cavity problem. The cavity problem is formulated by the finite element technique and solved iteratively by the Gauss–Newton method to reconstruct the properties of the object. Regularization for both the first and the second problems is achieved by a Krylov subspace method. The proposed method is tested against both synthetic and experimental data and promising reconstruction results are obtained.

  20. Effects of tissue conductivity and electrode area on internal electric fields in a numerical human model for ELF contact current exposures

    NASA Astrophysics Data System (ADS)

    Tarao, H.; Kuisti, H.; Korpinen, L.; Hayashi, N.; Isaka, K.

    2012-05-01

    Contact currents flow through the human body when a conducting object with different potential is touched. There are limited reports on numerical dosimetry for contact current exposure compared with electromagnetic field exposures. In this study, using an anatomical human adult male model, we performed numerical calculation of internal electric fields resulting from 60 Hz contact current flowing from the left hand to the left foot as a basis case. Next, we performed a variety of similar calculations with varying tissue conductivity and contact area, and compared the results with the basis case. We found that very low conductivity of skin and a small electrode size enhanced the internal fields in the muscle, subcutaneous fat and skin close to the contact region. The 99th percentile value of the fields in a particular tissue type did not reliably account for these fields near the electrode. In the arm and leg, the internal fields for the muscle anisotropy were identical to those in the isotropy case using a conductivity value longitudinal to the muscle fibre. Furthermore, the internal fields in the tissues abreast of the joints such as the wrist and the elbow, including low conductivity tissues, as well as the electrode contact region, exceeded the ICNIRP basic restriction for the general public with contact current as the reference level value.

  1. The current status and future direction of self-help treatments for problem gamblers.

    PubMed

    Raylu, Namrata; Oei, Tian P S; Loo, Jasmine

    2008-12-01

    The self-help treatment (SHT) studies for other psychological problems significantly outweigh those for problem gambling. Currently, very little is published about the application and efficacy of various forms of SHTs for problem gambling. Thus, this paper reviews the self-help literature (using the PsycINFO database--all years up to April 2008) to stimulate further research in this area for problem gambling. The findings show that SHTs in problem gambling are still in their infancy. Although the problem gambling literature has mainly reported on two forms of SHTs with problem gamblers (i.e. use of self-help manuals and audiotapes), the review discuss utilizing a wide range of SHTs with problem gamblers. These include written materials (e.g. self-help books and treatment manuals), audiotapes, videotapes, computer-based SHTs implemented on palmtop computers, desktop computers, via telephone (Interactive Voice Response systems--IVR) or via the Internet and virtual reality applications. These SHTs would suit those problem gamblers who are not accessing professional treatment due to shame, guilt, fear of stigma, privacy concerns or financial difficulties, as well as those living in rural areas or with less severe gambling problems. The review also suggest future protocols for conducting further research in this area with problem gamblers, highlighting a need for a cohesive theory to guide research. PMID:18760868

  2. The effects of an uncapped nanocrystal on a simulated induced current collected by a nano-contact

    SciTech Connect

    Doan, Quang-Tri; El Hdiy, Abdelillah

    2015-03-21

    The effects of the charge capture process by an isolated and uncapped nanocrystal on the electron beam induced current are studied by the use of the Monte Carlo simulation. In the calculation, the current is created by an electron beam irradiation and is collected by a hemispherical nano-contact. The nanocrystal is considered as a recombination center, and the surface recombination velocity at the free surface is assumed to be equal to zero. The diffusion length is taken out from the fitting of simulated collection efficiency profiles, and studied as a function of the electron beam energy. The diffusion length rapidly decreases at very low energy (≤∼5 keV), increases to reach a maximum at middle energies (∼13 keV), and then decreases to reach saturation for high energy (≥∼25 keV). The effect of the isolated nanocrystal at the surface is highlighted at high energy, when the diffusion length becomes energy independent. This situation leads to determination of effective surface recombination velocities the values of which underline the trapping process in the nanocrystal.

  3. Prevalence, putative mechanisms, and current management of sleep problems during chemotherapy for cancer

    PubMed Central

    Palesh, Oxana; Peppone, Luke; Innominato, Pasquale F; Janelsins, Michelle; Jeong, Monica; Sprod, Lisa; Savard, Josee; Rotatori, Max; Kesler, Shelli; Telli, Melinda; Mustian, Karen

    2012-01-01

    Sleep problems are highly prevalent in cancer patients undergoing chemotherapy. This article reviews existing evidence on etiology, associated symptoms, and management of sleep problems associated with chemotherapy treatment during cancer. It also discusses limitations and methodological issues of current research. The existing literature suggests that subjectively and objectively measured sleep problems are the highest during the chemotherapy phase of cancer treatments. A possibly involved mechanism reviewed here includes the rise in the circulating proinflammatory cytokines and the associated disruption in circadian rhythm in the development and maintenance of sleep dysregulation in cancer patients during chemotherapy. Various approaches to the management of sleep problems during chemotherapy are discussed with behavioral intervention showing promise. Exercise, including yoga, also appear to be effective and safe at least for subclinical levels of sleep problems in cancer patients. Numerous challenges are associated with conducting research on sleep in cancer patients during chemotherapy treatments and they are discussed in this review. Dedicated intervention trials, methodologically sound and sufficiently powered, are needed to test current and novel treatments of sleep problems in cancer patients receiving chemotherapy. Optimal management of sleep problems in patients with cancer receiving treatment may improve not only the well-being of patients, but also their prognosis given the emerging experimental and clinical evidence suggesting that sleep disruption might adversely impact treatment and recovery from cancer. PMID:23486503

  4. Non-contact online thickness measurement system for metal films based on eddy current sensing with distance tracking technique

    NASA Astrophysics Data System (ADS)

    Li, Wei; Wang, Hongbo; Feng, Zhihua

    2016-04-01

    This paper proposes an online, non-contact metal film thickness measurement system based on eddy current sensing. The slope of the lift-off curve (LOC) is used for characterizing target thickness. Theoretical derivation was conducted to prove that the slope is independent of the lift-off variation. In practice, the measurement has some immunity to the lift-off, but not perfect. The slope of LOC is still affected at some extent by the lift-off. Hence, a height tracking system was also proposed, which could stabilize the distance between the sensor and the target and significantly reduce the lift-off effect. The height tracking system contains a specially designed probe, which could vibrate rapidly to obtain a fast measurement speed, and its height can be adjusted up and down continuously to stabilize the lift-off. The sensor coil in the thickness measurement system was also used as the height sensor in the height tracking system. Several experiments were conducted to test the system performances under static and dynamic conditions. This measurement system demonstrated significant advantages, such as simple and clear conversion between the slope of LOC and target thickness, high resolution and stability, and minimized effect of lift-off variation.

  5. Non-contact online thickness measurement system for metal films based on eddy current sensing with distance tracking technique.

    PubMed

    Li, Wei; Wang, Hongbo; Feng, Zhihua

    2016-04-01

    This paper proposes an online, non-contact metal film thickness measurement system based on eddy current sensing. The slope of the lift-off curve (LOC) is used for characterizing target thickness. Theoretical derivation was conducted to prove that the slope is independent of the lift-off variation. In practice, the measurement has some immunity to the lift-off, but not perfect. The slope of LOC is still affected at some extent by the lift-off. Hence, a height tracking system was also proposed, which could stabilize the distance between the sensor and the target and significantly reduce the lift-off effect. The height tracking system contains a specially designed probe, which could vibrate rapidly to obtain a fast measurement speed, and its height can be adjusted up and down continuously to stabilize the lift-off. The sensor coil in the thickness measurement system was also used as the height sensor in the height tracking system. Several experiments were conducted to test the system performances under static and dynamic conditions. This measurement system demonstrated significant advantages, such as simple and clear conversion between the slope of LOC and target thickness, high resolution and stability, and minimized effect of lift-off variation. PMID:27131700

  6. Peer Problems in Attention Deficit Hyperactivity Disorder: Current Status and Future Directions

    ERIC Educational Resources Information Center

    McQuade, Julia D.; Hoza, Betsy

    2008-01-01

    This article extends previous reviews regarding the peer problems of children with Attention Deficit Hyperactivity Disorder (ADHD) in several ways. In addition to summarizing past and current literature regarding the social behaviors of children with ADHD, these behaviors are discussed in terms of subtype and gender differences and treatment…

  7. Overview of Current Trends in Mental Health Problems for Australia's Youth and Adolescents

    ERIC Educational Resources Information Center

    Rickwood, Debra; White, Angela; Eckersley, Richard

    2007-01-01

    This paper provides an overview of current trends in the mental health problems of Australia's youth and adolescents. It presents information derived from the most recent and comprehensive Australian surveys of youth mental health, and provides international comparisons and views from professional practice where relevant. An update of trends for…

  8. Effect of Polya Problem-Solving Model on Senior Secondary School Students' Performance in Current Electricity

    ERIC Educational Resources Information Center

    Olaniyan, Ademola Olatide; Omosewo, Esther O.; Nwankwo, Levi I.

    2015-01-01

    This study was designed to investigate the Effect of Polya Problem-Solving Model on Senior School Students' Performance in Current Electricity. It was a quasi experimental study of non- randomized, non equivalent pre-test post-test control group design. Three research questions were answered and corresponding three research hypotheses were tested…

  9. Evaluation of current state of agricultural land using problem-oriented fuzzy indicators in GIS environment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Current state of agricultural lands is defined under influence of processes in soil, plants and atmosphere and is described by observation data, complicated models and subjective opinion of experts. Problem-oriented indicators summarize this information in useful form for decision of the same specif...

  10. Current Problems of Teacher Education. Report of a Meeting of International Experts.

    ERIC Educational Resources Information Center

    Yates, Alfred, Ed.

    This report is the outcome of an international meeting of the UNESCO Institute for Education in Hamburg in 1969. To stimulate interest in the potentialities of research in the field of teacher education, it incorporates the major conclusions reached at the meeting concerning those current problems in teacher education to which methods of empirical…

  11. Semi-analytical solution to the 2014 eddy current benchmark problem

    NASA Astrophysics Data System (ADS)

    Miorelli, Roberto; Reboud, Christophe; Voulgaraki, Charitini; Poulakis, Nikolaos; Theodoulidis, Theodoros

    2015-03-01

    This work proposes a solution to the 2014 eddy current testing benchmark, published by the WFNDEC and proposed by the authors. The aim of this benchmark is to provide reference data for eddy current testing configurations involving magnetic sensors -here Hall sensors- as receivers, as they present some advantages in terms of resolution and sensitivity. After a presentation of the benchmark cases, the theoretical approach used to solve the equivalent electromagnetic problem is detailed and a alternative computation of eddy current signals is proposed. Then, simulations are quantitatively compared to experimental data in each case and the results are discussed.

  12. Redundant drive current imbalance problem of the Automatic Radiator Inspection Device (ARID)

    NASA Technical Reports Server (NTRS)

    Latino, Carl D.

    1992-01-01

    The Automatic Radiator Inspection Device (ARID) is a 4 Degree of Freedom (DOF) robot with redundant drive motors at each joint. The device is intended to automate the labor intensive task of space shuttle radiator inspection. For safety and redundancy, each joint is driven by two independent motor systems. Motors driving the same joint, however, draw vastly different currents. The concern was that the robot joints could be subjected to undue stress. It was the objective of this summer's project to determine the cause of this current imbalance. In addition it was to determine, in a quantitative manner, what was the cause, how serious the problem was in terms of damage or undue wear to the robot and find solutions if possible. It was concluded that most problems could be resolved with a better motor control design. This document discusses problems encountered and possible solutions.

  13. The role of contact resistance in GeTe and Ge2Sb2Te5 nanowire phase change memory reset switching current

    NASA Astrophysics Data System (ADS)

    Hwang, Inchan; Cho, Yong-Jun; Lee, Myoung-Jae; Jo, Moon-Ho

    2015-05-01

    Nanowire (NW) structures offer a model system for investigating material and scaling properties of phase change random access memory (PCRAM) at the nanometer scale. Here, we investigate the relationship between nanowire device contact resistance and reset current (Ireset) for varying diameters of NWs. Because the reset switching current directly affects possible device density of PCRAM NWs, it is considered one of the most important parameters for PCRAM. We found that the reset switching current, Ireset, was inversely proportional to the contact resistance of PCRAM NW devices decreasing as NW diameter was reduced from 250 nm to 20 nm. Our observations suggest that the reduction of power consumption of PCRAM in the sub-lithographic regime can be achieved by lowering the contact resistance.

  14. [Current problems and challenges in the diagnosis and treatment of colorectal cancer in China].

    PubMed

    Wang, Jianping; Wang, Lei

    2014-06-01

    In the past 20 years, researches regarding colorectal cancer have experienced unprecedented boom in China. However, a seris problems have been exposed, including a rapid increase in morbility, the geographical limitations of tumor screening, nonstandard diagnosis and treatment, very limited mechanism researches, and lack of randomized controlled clinical trials with Chinese characteristics. This article puts forward some main emphases of the current work, based on the above problems and challenges, in order to improve the overall level of the diagnosis and treatment of colorectal cancer in China. PMID:24953353

  15. Capillary forces exerted by liquid drops caught between crossed cylinders. A 3-D meniscus problem with free contact line

    NASA Technical Reports Server (NTRS)

    Patzek, T. W.; Scriven, L. E.

    1982-01-01

    The Young-Laplace equation is solved for three-dimensional menisci between crossed cylinders, with either the contact line fixed or the contact angle prescribed, by means of the Galerkin/finite element method. Shapes are computed, and with them the practically important quantities: drop volume, wetted area, capillary pressure force, surface tension force, and the total force exerted by the drop on each cylinder. The results show that total capillary force between cylinders increases with decreasing contact angle, i.e. with better wetting. Capillary force is also increases with decreasing drop volume, approaching an asymptotic limit. However, the wetted area on each cylinder decreases with decreasing drop volume, which raises the question of the optimum drop volume to strive for, when permanent bonding is sought from solidified liquid. For then the strength of the bond is likely to depend upon the area of contact, which is the wetted area when the bonding agent was introduced in liquid form.

  16. Childhood Abuse and Current Health Problems among Older Adults: The Mediating Role of Self-Efficacy

    PubMed Central

    Sachs-Ericsson, Natalie; Medley, Amanda N.; Kendall – Tackett, Kathleen; Taylor, John

    2011-01-01

    Objectives Child abuse has negative consequences on health functioning and the self-concept. Prior studies have garnered support for these relationships in younger adults; yet few studies have looked at the effects of abuse on health in older adults and the psychosocial variables, specifically self-efficacy, that may influence the abuse-health relationship. Methods Data obtained from the Physical Health and Disability Study were used to explore the impact of child abuse on current medical problems among older adults who were screened on physical disability status (N=1396, Mean age = 67, SD = 10.2). The study was conducted in South Florida and employed a multiethnic sample that is representative of the general population in this area. Results Child abuse was associated with the number of current medical problems and disability. Child abuse was also related to lower self-efficacy, and self-efficacy explained the relationship between abuse and the number of health problems. Conclusions There are far reaching effects of child abuse on older adults' health and self-concept. Health care providers and gerontologists need to be aware that child abuse is a life-long risk factor for increased disability and specific health problems, especially among the elderly. Future research should examine treatments designed to increase self-efficacy, especially among those who experienced child abuse, and observe any positive effects on health functioning. PMID:21922052

  17. Fast solver for large scale eddy current non-destructive evaluation problems

    NASA Astrophysics Data System (ADS)

    Lei, Naiguang

    Eddy current testing plays a very important role in non-destructive evaluations of conducting test samples. Based on Faraday's law, an alternating magnetic field source generates induced currents, called eddy currents, in an electrically conducting test specimen. The eddy currents generate induced magnetic fields that oppose the direction of the inducing magnetic field in accordance with Lenz's law. In the presence of discontinuities in material property or defects in the test specimen, the induced eddy current paths are perturbed and the associated magnetic fields can be detected by coils or magnetic field sensors, such as Hall elements or magneto-resistance sensors. Due to the complexity of the test specimen and the inspection environments, the availability of theoretical simulation models is extremely valuable for studying the basic field/flaw interactions in order to obtain a fuller understanding of non-destructive testing phenomena. Theoretical models of the forward problem are also useful for training and validation of automated defect detection systems. Theoretical models generate defect signatures that are expensive to replicate experimentally. In general, modelling methods can be classified into two categories: analytical and numerical. Although analytical approaches offer closed form solution, it is generally not possible to obtain largely due to the complex sample and defect geometries, especially in three-dimensional space. Numerical modelling has become popular with advances in computer technology and computational methods. However, due to the huge time consumption in the case of large scale problems, accelerations/fast solvers are needed to enhance numerical models. This dissertation describes a numerical simulation model for eddy current problems using finite element analysis. Validation of the accuracy of this model is demonstrated via comparison with experimental measurements of steam generator tube wall defects. These simulations generating two

  18. Shoe allergic contact dermatitis.

    PubMed

    Matthys, Erin; Zahir, Amir; Ehrlich, Alison

    2014-01-01

    Foot dermatitis is a widespread condition, affecting men and women of all ages. Because of the location, this condition may present as a debilitating problem to those who have it. Allergic contact dermatitis involving the feet is frequently due to shoes or socks. The allergens that cause shoe dermatitis can be found in any constituent of footwear, including rubber, adhesives, leather, dyes, metals, and medicaments. The goal of treatment is to identify and minimize contact with the offending allergen(s). The lack of product information released from shoe manufacturers and the continually changing trends in footwear present a challenge in treating this condition. The aim of this study is to review the current literature on allergic contact shoe dermatitis; clinical presentation, allergens, patch testing, and management will be discussed. PubMed and MEDLINE databases were used for the search, with a focus on literature updates from the last 15 years. PMID:25000234

  19. A practical solution in delineating thin conducting structures and suppression problem in direct current resistivity sounding

    NASA Astrophysics Data System (ADS)

    Sharma, Shashi Prakash; Biswas, Arkoprovo

    2013-08-01

    In hard rock areas, conventional apparent resistivity measurement using Schlumberger resistivity sounding fails to detect thin conducting structures (2-D and 3-D fractures filled with groundwater and mineral aggregate) concealed at a large depth. In the present study, an attempt is made to way-out the detection problem of deep seated thin conducting layer. It is proposed to study the apparent conductance simultaneously with resistivity sounding to detect such conductive zones qualitatively. Apparent conductance is defined as the magnitude of current flowing in the subsurface for a unit applied voltage through current electrodes. Even though such measurement is of qualitative importance, it gives extremely valuable information for the presence of conductive zones at depth in challenging hard rock terrain. It has been observed that apparent conductance increases significantly when groundwater bearing fractures and conductive bodies are encountered in the subsurface. Field data from different locations are presented to demonstrate the efficacy of such measurement. The measurement assists to the conventional resistivity sounding for successful prediction of groundwater zones at large depth in different hard rock areas and is of enormous importance. The approach is also used for possible solution of suppression problem in the DC resistivity sounding when intermediate layer is not reflected in the resistivity sounding curve. Finally, the approach can be used together with resistivity sounding to solve many practical problems.

  20. Effects of mother-infant skin-to-skin contact on severe latch-on problems in older infants: a randomized trial

    PubMed Central

    2013-01-01

    Background Infants with latch-on problems cause stress for parents and staff, often resulting in early termination of breastfeeding. Healthy newborns experiencing skin-to-skin contact at birth are pre-programmed to find the mother’s breast. This study investigates if skin-to-skin contact between mothers with older infants having severe latching on problems would resolve the problem. Methods Mother-infant pairs with severe latch-on problems, that were not resolved during screening procedures at two maternity hospitals in Stockholm 1998–2004, were randomly assigned to skin-to-skin contact (experimental group) or not (control group) during breastfeeding. Breastfeeding counseling was given to both groups according to a standard model. Participants were unaware of their treatment group. Objectives were to compare treatment groups concerning the proportion of infants regularly latching on, the time from intervention to regular latching on and maternal emotions and pain before and during breastfeeding. Results On hundred and three mother-infant pairs with severe latch-on problems 1–16 weeks postpartum were randomly assigned and analyzed. There was no significant difference between the groups in the proportion of infants starting regular latching-on (75% experimental group, vs. 86% control group). Experimental group infants, who latched on, had a significantly shorter median time from start of intervention to regular latching on than control infants, 2.0 weeks (Q1 = 1.0, Q3 = 3.7) vs. 4.7 weeks (Q1 = 2.0, Q3 = 8.0), (p-value = 0.020). However, more infants in the experimental group (94%), with a history of “strong reaction” during “hands-on latch intervention”, latched-on within 3 weeks compared to 33% in the control infants (Fisher Exact test p-value = 0.0001). Mothers in the experimental group (n = 53) had a more positive breastfeeding experience according to the Breastfeeding Emotional Scale during the intervention than mothers in the control group (n = 50

  1. Peer problems in Attention Deficit Hyperactivity Disorder: current status and future directions.

    PubMed

    McQuade, Julia D; Hoza, Betsy

    2008-01-01

    This article extends previous reviews regarding the peer problems of children with Attention Deficit Hyperactivity Disorder (ADHD) in several ways. In addition to summarizing past and current literature regarding the social behaviors of children with ADHD, these behaviors are discussed in terms of subtype and gender differences and treatment implications. Given limited effectiveness of treatment options, whether it be medication, behavioral modification, or social skills training, there is a need to examine additional factors that may contribute to the social impairment of children with ADHD. Therefore, this review focuses on potential neuropsychological deficits, biased perceptions of social ability, and deficits in encoding and processing social information that may contribute to the social impairment of children with ADHD. These topics are discussed both in terms of their contribution to our understanding of the peer problems of children with ADHD and as potential avenues for future research. PMID:19072753

  2. Storage and treatment of SNF of Alfa class nuclear submarines: current status and problems

    SciTech Connect

    Ignatiev, Sviatoslav; Zabudko, Alexey; Pankratov, Dmitry; Somov, Ivan; Suvorov, Gennady

    2007-07-01

    Available in abstract form only. Full text of publication follows: The current status and main problems associated with storage, defueling and following treatment of spent nuclear fuel (SNF) of Nuclear Submarines (NS) with heavy liquid metal cooled reactors are considered. In the final analysis these solutions could be realized in the form of separate projects to be funded through national and bi- and multilateral funding in the framework of the international collaboration of the Russian Federation on complex utilization of NS and rehabilitation of contaminated objects allocated in the North-West region of Russia. (authors)

  3. Dialysis in the frail elderly--a current ethical problem, an impending ethical crisis.

    PubMed

    Thorsteinsdottir, Bjorg; Swetz, Keith M; Tilburt, Jon C

    2013-11-01

    The current practice of hemodialysis for the frail elderly frequently ignores core bioethical principles. Lack of transparency and shared decision making coupled with financial incentives to treat have resulted in problems of overtreatment near the end of life. Imminent changes in reimbursement for hemodialysis will reverse the financial incentives to favor not treating high-risk patients. In this article, we describe what is empirically known about the approach to hemodialysis today, and how it violates four core ethical principles. We then discuss how the new financial system turns physician and organizational incentives upside down in ways that may exacerbate the ethical dilemmas, but in the opposite direction. PMID:23686511

  4. Finite element simulation of eddy current problems using magnetic scalar potentials

    NASA Astrophysics Data System (ADS)

    Alonso Rodríguez, Ana; Bertolazzi, Enrico; Ghiloni, Riccardo; Valli, Alberto

    2015-08-01

    We propose a new implementation of the finite element approximation of eddy current problems using, as the principal unknown, the magnetic field. In the non-conducting region a scalar magnetic potential is introduced. The method can deal automatically with any topological configuration of the conducting region and, being based on the search of a scalar magnetic potential in the non-conducting region, has the advantage of making use of a reduced number of unknowns. Several numerical tests are presented for illustrating the performance of the proposed method; in particular, the numerical simulation of a new type of transformer of complicated topological shape is shown.

  5. Simplified Numerical Analysis of ECT Probe - Eddy Current Benchmark Problem 3

    SciTech Connect

    Sikora, R.; Chady, T.; Gratkowski, S.; Stawicki, K.

    2005-04-09

    In this paper a third eddy current benchmark problem is considered. The objective of the benchmark is to determine optimal operating frequency and size of the pancake coil designated for testing tubes made of Inconel. It can be achieved by maximization of the change in impedance of the coil due to a flaw. Approximation functions of the probe (coil) characteristic were developed and used in order to reduce number of required calculations. It results in significant speed up of the optimization process. An optimal testing frequency and size of the probe were achieved as a final result of the calculation.

  6. Some problems in using a polyvinylidene fluoride transducer for the intra-articular determination of joint contact stress.

    PubMed

    Hale, J E; Vaughan, C L

    1993-01-01

    A piezoelectric transducer and associated instrumentation were developed and evaluated as a means of experimentally determining joint contact stress. Each transducer, fabricated from a polyvinylidene fluoride film, comprised four discrete sensing elements. Following dynamic calibration of all sensing elements, in vitro evaluations were performed with transducers positioned in canine tibio-femoral joints. Quantitative measurements of contact stress as a function of time were obtained using these transducers, the magnitudes of which ranged between 0.01 and 7.99 MPa. Limitations associated with the transducer material and its use in this specific application included calibration variability and temporal phase shift of the transducer output signal relative to the applied load. PMID:8280314

  7. Towards a more accurate microscopic description of the moving contact line problem - incorporating nonlocal effects through a statistical mechanics framework

    NASA Astrophysics Data System (ADS)

    Nold, Andreas; Goddard, Ben; Sibley, David; Kalliadasis, Serafim

    2014-03-01

    Multiscale effects play a predominant role in wetting phenomena such as the moving contact line. An accurate description is of paramount interest for a wide range of industrial applications, yet it is a matter of ongoing research, due to the difficulty of incorporating different physical effects in one model. Important small-scale phenomena are corrections to the attractive fluid-fluid and wall-fluid forces in inhomogeneous density distributions, which often previously have been accounted for by the disjoining pressure in an ad-hoc manner. We systematically derive a novel model for the description of a single-component liquid-vapor multiphase system which inherently incorporates these nonlocal effects. This derivation, which is inspired by statistical mechanics in the framework of colloidal density functional theory, is critically discussed with respect to its assumptions and restrictions. The model is then employed numerically to study a moving contact line of a liquid fluid displacing its vapor phase. We show how nonlocal physical effects are inherently incorporated by the model and describe how classical macroscopic results for the contact line motion are retrieved. We acknowledge financial support from ERC Advanced Grant No. 247031 and Imperial College through a DTG International Studentship.

  8. Physically based mathematical models in soil science: History, current state, problems, and outlook (Analytical Review)

    NASA Astrophysics Data System (ADS)

    Shein, E. V.

    2015-07-01

    The formation, development, and some problems of the current physically based models of water and solute transfer are considered in this review. These models appeared about a half century ago. They were based on the basic laws of soil physics and other branches of soil science (laws of balance, transfer, diffusion, hydrodynamic dispersion, etc.) described by the corresponding equations and programs and supported by the experimental data in the form of physically based parameters. At present, one of the main problems in the development, adaptation, and application of these models is that the current and future mathematical models should rest upon the experimental support with a clear physical basis characterizing the nature of the phenomenon described. This experimental support enables creating research models, drawing conceptual conclusions, and, hence, understanding, analyzing, and managing soil processes. This is apparently possible only if the set of methods for the experimental support of models is substantiated, preferably in direct physical experiments and under field conditions close to the future model prognoses.

  9. Finite element solution of nonlinear eddy current problems with periodic excitation and its industrial applications.

    PubMed

    Bíró, Oszkár; Koczka, Gergely; Preis, Kurt

    2014-05-01

    An efficient finite element method to take account of the nonlinearity of the magnetic materials when analyzing three-dimensional eddy current problems is presented in this paper. The problem is formulated in terms of vector and scalar potentials approximated by edge and node based finite element basis functions. The application of Galerkin techniques leads to a large, nonlinear system of ordinary differential equations in the time domain. The excitations are assumed to be time-periodic and the steady-state periodic solution is of interest only. This is represented either in the frequency domain as a finite Fourier series or in the time domain as a set of discrete time values within one period for each finite element degree of freedom. The former approach is the (continuous) harmonic balance method and, in the latter one, discrete Fourier transformation will be shown to lead to a discrete harmonic balance method. Due to the nonlinearity, all harmonics, both continuous and discrete, are coupled to each other. The harmonics would be decoupled if the problem were linear, therefore, a special nonlinear iteration technique, the fixed-point method is used to linearize the equations by selecting a time-independent permeability distribution, the so-called fixed-point permeability in each nonlinear iteration step. This leads to uncoupled harmonics within these steps. As industrial applications, analyses of large power transformers are presented. The first example is the computation of the electromagnetic field of a single-phase transformer in the time domain with the results compared to those obtained by traditional time-stepping techniques. In the second application, an advanced model of the same transformer is analyzed in the frequency domain by the harmonic balance method with the effect of the presence of higher harmonics on the losses investigated. Finally a third example tackles the case of direct current (DC) bias in the coils of a single-phase transformer. PMID

  10. Contact dermatitis

    MedlinePlus

    Dermatitis - contact; Allergic dermatitis; Dermatitis - allergic; Irritant contact dermatitis; Skin rash - contact dermatitis ... There are 2 types of contact dermatitis. Irritant dermatitis: This ... can be by contact with acids, alkaline materials such as soaps ...

  11. Numerical analysis of some problems related to the mechanics of pneumatic tires: Finite deformation/rolling contact of a viscoelastic cylinder and finite deformation of cord-reinforced rubber composites

    NASA Technical Reports Server (NTRS)

    Oden, J. T.; Becker, E. B.; Lin, T. L.; Hsieh, K. T.

    1984-01-01

    The formulation and numerical analysis of several problems related to the behavior of pneumatic tires are considered. These problems include the general rolling contact problem of a rubber-like viscoelastic cylinder undergoing finite deformations and the finite deformation of cord-reinforced rubber composites. New finite element models are developed for these problems. Numerical results obtained for several representative cases are presented.

  12. The Host Immune Response to Tissue-Engineered Organs: Current Problems and Future Directions.

    PubMed

    Wiles, Katherine; Fishman, Jonathan M; De Coppi, Paolo; Birchall, Martin A

    2016-06-01

    As the global health burden of chronic disease increases, end-stage organ failure has become a costly and intractable problem. De novo organ creation is one of the long-term goals of the medical community. One of the promising avenues is that of tissue engineering: the use of biomaterials to create cells, structures, or even whole organs. Tissue engineering has emerged from its nascent stage, with several proof-of-principle trials performed across various tissue types. As tissue engineering moves from the realm of case trials to broader clinical study, three major questions have emerged: (1) Can the production of biological scaffolds be scaled up accordingly to meet current and future demands without generating an unfavorable immune response? (2) Are biological scaffolds plus or minus the inclusion of cells replaced by scar tissue or native functional tissue? (3) Can tissue-engineered organs be grown in children and adolescents given the different immune profiles of children? In this review, we highlight current research in the immunological response to tissue-engineered biomaterials, cells, and whole organs and address the answers to these questions. PMID:26701069

  13. Mathematical model of electrical contact bouncing

    NASA Astrophysics Data System (ADS)

    Kharin, Stanislav

    2015-09-01

    Mathematical model of a contact bouncing takes into account elastic-plastic and electrodynamic forces, phase transformations during interaction of electrical arc with the contact surface as a result of increasing temperature. It is based on the integro-differential equations for the contact motion and Stefan problem for the temperature field. These equations describe four consecutive stages of the contact vibration from the impact at contact closing up to opening after bouncing including effects of penetration and restitution. The new method for the solution of the Stefan problem is elaborated, which enables us to get the information about dynamics of zones of elasticity, plasticity and phase transformations during contact vibration. It is shown that the decrement of damping depends on the coefficient of plasticity and the moment of inertia only, while the frequency of vibration depends also on the hardness of contact, its temperature, properties of contact spring, and geometry of rotational mechanism. It is found also from the solution of Stefan problem that the relationship between dynamical zones of plasticity and melting explains the decrease of current density and contact welding. The results of calculations are compared with the experimental data.

  14. Health and safety problems associated with long working hours: a review of the current position.

    PubMed

    Spurgeon, A; Harrington, J M; Cooper, C L

    1997-06-01

    The European Community Directive on Working Time, which should have been implemented in member states of the European Community by November 1996, contains several requirements related to working hours, including the right of employees to refuse to work more than 48 hours a week. The United Kingdom government attempted to oppose the Directive, arguing that there is no convincing evidence that hours of work should be limited on health and safety grounds. Much of the research in this area has focused on the problems of shiftworking and previous reviews have therefore tended to emphasise this aspect of working hours. However, there is much less information about the effects of overtime work, which is a central element of the terms of the Directive. This paper reviews the current evidence relating to the potential effects on health and performance of extensions to the normal working day. Several gaps in the literature are identified. Research to date has been restricted to a limited range of health outcomes--namely, mental health and cardiovascular disorders. Other potential effects which are normally associated with stress--for example, gastrointestinal disorders, musculoskeletal disorders, and problems associated with depression of the immune system, have received little attention. Also, there have been few systematic investigations of performance effects, and little consideration of the implications for occupational exposure limits of extensions to the working day. Existing data relate largely to situations where working hours exceed 50 a week and there is a lack of information on hours below this level, which is of direct relevance to the European Community proposal. Finally, it is clear from investigations relating to shiftwork that a range of modifying factors are likely to influence the level and nature of health and performance outcomes. These include the attitudes and motivation of the people concerned, the job requirements, and other aspects of the

  15. Health and safety problems associated with long working hours: a review of the current position.

    PubMed Central

    Spurgeon, A; Harrington, J M; Cooper, C L

    1997-01-01

    The European Community Directive on Working Time, which should have been implemented in member states of the European Community by November 1996, contains several requirements related to working hours, including the right of employees to refuse to work more than 48 hours a week. The United Kingdom government attempted to oppose the Directive, arguing that there is no convincing evidence that hours of work should be limited on health and safety grounds. Much of the research in this area has focused on the problems of shiftworking and previous reviews have therefore tended to emphasise this aspect of working hours. However, there is much less information about the effects of overtime work, which is a central element of the terms of the Directive. This paper reviews the current evidence relating to the potential effects on health and performance of extensions to the normal working day. Several gaps in the literature are identified. Research to date has been restricted to a limited range of health outcomes--namely, mental health and cardiovascular disorders. Other potential effects which are normally associated with stress--for example, gastrointestinal disorders, musculoskeletal disorders, and problems associated with depression of the immune system, have received little attention. Also, there have been few systematic investigations of performance effects, and little consideration of the implications for occupational exposure limits of extensions to the working day. Existing data relate largely to situations where working hours exceed 50 a week and there is a lack of information on hours below this level, which is of direct relevance to the European Community proposal. Finally, it is clear from investigations relating to shiftwork that a range of modifying factors are likely to influence the level and nature of health and performance outcomes. These include the attitudes and motivation of the people concerned, the job requirements, and other aspects of the

  16. Probing cellular processes by long-term live imaging--historic problems and current solutions.

    PubMed

    Coutu, Daniel L; Schroeder, Timm

    2013-09-01

    Living organisms, tissues, cells and molecules are highly dynamic. The importance of their continuous and long-term observation has been recognized for over a century but has been limited by technological hurdles. Improvements in imaging technologies, genetics, protein engineering and data analysis have more recently allowed us to answer long-standing questions in biology using quantitative continuous long-term imaging. This requires a multidisciplinary collaboration between scientists of various backgrounds: biologists asking relevant questions, imaging specialists and engineers developing hardware, and informaticians and mathematicians developing software for data acquisition, analysis and computational modeling. Despite recent improvements, there are still obstacles to be addressed before this technology can achieve its full potential. This Commentary aims at providing an overview of currently available technologies for quantitative continuous long-term single-cell imaging, their limitations and what is required to bring this field to the next level. We provide an historical perspective on the development of this technology and discuss key issues in time-lapse imaging: keeping cells alive, using labels, reporters and biosensors, and hardware and software requirements. We highlight crucial and often non-obvious problems for researchers venturing into the field and hope to inspire experts in the field and from related disciplines to contribute to future solutions. PMID:23943879

  17. Numerical solution of the general 3D eddy current problem for magnetic induction tomography (spectroscopy).

    PubMed

    Merwa, Robert; Hollaus, Karl; Brandstätter, Bernhard; Scharfetter, Hermann

    2003-05-01

    Magnetic induction tomography (MIT) is used for reconstructing the changes of the conductivity in a target object using alternating magnetic fields. Applications include, for example, the non-invasive monitoring of oedema in the human brain. A powerful software package has been developed which makes it possible to generate a finite element (FE) model of complex structures and to calculate the eddy currents in the object under investigation. To validate our software a model of a previously published experimental arrangement was generated. The model consists of a coaxial coil system and a conducting sphere which is moved perpendicular to the coil axis (a) in an empty space and (b) in a saline-filled cylindrical tank. The agreement of the measured and simulated data is very good when taking into consideration the systematic measurement errors in case (b). Thus the applicability of the simulation algorithm for two-compartment systems has been demonstrated even in the case of low conductivities and weak contrast. This can be considered an important step towards the solution of the inverse problem of MIT. PMID:12812437

  18. A Survey on Renewable Energy Development in Malaysia: Current Status, Problems and Prospects

    NASA Astrophysics Data System (ADS)

    Alam, Syed Shah; Nor, Nor Fariza Mohd; Ahmad, Maisarah; Hashim, Nik Hazrul Nik

    2016-05-01

    Energy demand in Malaysia is increasing over seven per cent a year, while forty per cent of the energy is supplied from conventional fossil fuel. However, a number of social barriers have mired the social acceptance of renewable energy among the users. This study investigates the current status of renewable energy, problems and future outlook of renewable energy in Malaysia. A total of 200 respondents were surveyed from Klang Valley in Malaysia. Majority of the respondents use energy to generate electricity. Although some respondents reported using solar energy, there is lack of retail availability for solar energy. The findings show that limited information on renewable energy technologies, lack of awareness, and limited private sector engagement emerged as major barriers to sustainable renewable energy development. In addition, the respondents suggest for increasing policy support from the government to make information more accessible to mass users, provide economic incentives to investors and users, and promote small-community based renewable energy projects. The study suggests that the government begin small scale projects to build awareness on renewable energy, while academically, higher learning institutions include renewable energy syllabus in their academic curriculum. The study concluded that to have sustainable renewable energy development, government's initiative, private sector engagement and users awareness must be given priority.

  19. Contact Interface Verification for DYNA3D Scenario 1: Basic Contact

    SciTech Connect

    McMichael, L D

    2006-05-10

    A suite of test problems has been developed to examine contact behavior within the nonlinear, three-dimensional, explicit finite element analysis (FEA) code DYNA3D (Lin, 2005). The test problems address the basic functionality of the contact algorithms, including the behavior of various kinematic, penalty, and Lagrangian enforcement formulations. The results from the DYNA3D analyses are compared to closed form solutions to verify the contact behavior. This work was performed as part of the Verification and Validation efforts of LLNL W Program within the NNSA's Advanced Simulation and Computing (ASC) Program. DYNA3D models the transient dynamic response of solids and structures including the interactions between disjoint bodies (parts). A wide variety of contact surfaces are available to represent the diverse interactions possible during an analysis, including relative motion (sliding), separation and gap closure (voids), and fixed relative position (tied). The problem geometry may be defined using a combination of element formulations, including one-dimensional beam and truss elements, two-dimensional shell elements, and three-dimensional solid elements. Consequently, it is necessary to consider various element interactions for each contact algorithm being verified. Most of the contact algorithms currently available in DYNA3D are examined; the exceptions are the Type 4--Single Surface Contact and Type 11--SAND algorithms. It is likely that these algorithms will be removed since their functionality is embodied in other, more robust, contact algorithms. The automatic contact algorithm is evaluated using the Type 12 interface. Two other variations of automatic contact, Type 13 and Type 14, offer additional means to adapt the interface domain, but share the same search and restoration algorithms as Type 12. The contact algorithms are summarized in Table 1. This report and associated test problems examine the scenario where one contact surface exists between two

  20. THE CURRENT STATUS OF RESEARCH AND THEORY IN HUMAN PROBLEM SOLVING.

    ERIC Educational Resources Information Center

    DAVIS, GARY A.

    PROBLEM-SOLVING THEORIES IN THREE AREAS - TRADITIONAL (STIMULUS-RESPONSE) LEARNING, COGNITIVE-GESTALT APPROACHES, AND COMPUTER AND MATHEMATICAL MODELS - WERE SUMMARIZED. RECENT EMPIRICAL STUDIES (1960-65) ON PROBLEM SOLVING WERE CATEGORIZED ACCORDING TO TYPE OF BEHAVIOR ELICITED BY PARTICULAR PROBLEM-SOLVING TASKS. ANAGRAM, "INSIGHT,""WATER-JAR,"…

  1. Astronomical Site in the Ukraine: Current Status and Problems of Preservation

    NASA Astrophysics Data System (ADS)

    Vavilova, I. B.; Karetnikov, V. G.; Konovalenko, A. A.; Logvinenko, O. O.; Pinigin, G. I.; Steshenko, N. V.; Tarady, V. K.; Yatskiv, Ya. S.

    The present status of optical and radio astronomical sites in Ukraine and the problems of preservation are briefly reviewed. The problems of light pollution and the influence of thechnology can be solved using scientific and engeneering methods. However the main problem of preservation is the economic one of maintaining the infrastructure.

  2. A comprehensive study of charge trapping in organic field-effect devices with promising semiconductors and different contact metals by displacement current measurements

    NASA Astrophysics Data System (ADS)

    Bisoyi, Sibani; Rödel, Reinhold; Zschieschang, Ute; Kang, Myeong Jin; Takimiya, Kazuo; Klauk, Hagen; Tiwari, Shree Prakash

    2016-02-01

    A systematic and comprehensive study on the charge-carrier injection and trapping behavior was performed using displacement current measurements in long-channel capacitors based on four promising small-molecule organic semiconductors (pentacene, DNTT, C10-DNTT and DPh-DNTT). In thin-film transistors, these semiconductors showed charge-carrier mobilities ranging from 1.0 to 7.8 cm2 V-1 s-1. The number of charges injected into and extracted from the semiconductor and the density of charges trapped in the device during each measurement were calculated from the displacement current characteristics and it was found that the density of trapped charges is very similar in all devices and of the order 1012 cm-2, despite the fact that the four semiconductors show significantly different charge-carrier mobilities. The choice of the contact metal (Au, Ag, Cu, Pd) was also found to have no significant effect on the trapping behavior.

  3. Military aviation: a contact lens review.

    PubMed

    Lattimore, M R

    1990-10-01

    The military aviation communities have benefitted from the development of advanced electro-optical avionics systems. One drawback that has emerged is an increasing system incompatibility with traditional spectacle visual corrections. An alternative solution to the refractive error correction problem that some services have been investigating is that of contact lens wear. Since this much-debated topic is currently of command interest, a general overview of contact lens issues is presented as a framework for future discussions. PMID:2241737

  4. Activities and current research from the EC, standards, measurements and testing programme (SMT) in the area of food contact materials.

    PubMed

    Boenke, A

    1997-01-01

    The EC, Standards, Measurements and Testing Programme (SMT) is the successor of the Measurements and Testing Programme (M&T) and the Community Bureau of Reference (BCR). Its objectives include the provision of research and technical support to standardization and health of the society when it is required to improve the competitive position of European industry, and for the development or implementation of Community policy. The SMT-Programme is currently supporting a number of different types of collaborative projects in the food packaging sphere. Their objectives range from method development via preparation and certification of reference materials, preparation of a handbook and the update of a spectral atlas to pre-normative research providing information on a number of sources and wide range of packed products being transported throughout Europe. PMID:9373520

  5. Enhancement of magnetic properties in magnesium diboride and characterization of Josephson and quasiparticle currents in magesium diboride contact junctions

    NASA Astrophysics Data System (ADS)

    Shen, Yi

    Methods to produce MgB2 thin films and tunneling devices have been developed. Thin films have been optimized for high field applications by exploring a range of doping and growth conditions. Josephson junction devices have been produced using a novel technique to optimize the quality of the barrier and near-interface superconducting materials. The effects of impurities incorporation in MgB2 thin films in the physical properties were studied. First, rubidium and cesium were ex-situ introduced into thin films by annealing in quartz ampoules containing elemental alkali metals. No significant change in transition temperature (Tc) was observed by resistivity measurement, in contrast to an earlier report of enhanced Tcs (>50 K) from susceptibility measurements. A significant drop in Jc and an increase in Deltarho (rho 300-rho40) arise from a decrease in inter-granular connectivity during annealing. Second, oxygen was incorporated using in-situ post-growth anneals in an oxygen environment. Analysis of the electrical data indicates that oxygen is distributed both within and between the grains. High values of Jc (˜4x105 A/cm2 at 8 T and 4.2 K), extrapolated Hc2(0) > 45 T and |dHc2/dT| Tc| ≈ 1.4 T/K are observed. A novel deposition approach allows films of magnesium plus boron to be deposited on unheated c-plane sapphire substrates by co-evaporation, and then subsequently annealed in a reducing atmosphere at temperatures below 600°C. The use of a combination of a magnesium rich stoichiometry (Mg/B > 1/2) in the as-deposited film, and a two-step annealing process, was found to be critical in obtaining unusual high values of Hc2(0) > 43 T and |dH c2/dT|Tc| ≈ 2.5 T/K. Josephson junctions fabricated by pressing two oxidized MgB2 thin films together. This facilitates the production of Josephson Junctions with two MgB2 electrodes without exposure to the high second electrode deposition temperature. These junctions, with electrode Tcs of ˜32 K, have critical currents up to

  6. Contact Dermatitis

    MedlinePlus

    ... care Kids’ zone Video library Find a dermatologist Contact dermatitis Overview Contact dermatitis: Many health care workers ... to touching her face while wearing latex gloves. Contact dermatitis: Overview Almost everyone gets this type of ...

  7. Finite element modeling of conducting shells for eddy current NDE problems using ``impedance-type`` interface conditions

    SciTech Connect

    Badics, Z.; Matsumoto, Yoshihiro; Kojima, Sota; Usui, Yoshihiko; Aoki, Kazuhiko; Nakayasu, Fumio

    1997-03-01

    A 3D finite element scheme is developed to calculate eddy current probe responses (impedance or induced emf changes of coils) due to conducting shells in eddy current NDE (nondestructive evaluation) problems. These problems are related to the eddy current inspection of copper and magnetite deposit zones of steam generator tubing in PWR atomic power plants. The finite element scheme uses impedance interface conditions to model the deposit shells and calculates the probe responses by performing integrals over the shell surfaces, thereby ensuring high accuracy even if the probe signal is very small. Two benchmark arrangements are investigated. One, which has an analytical solution, is a conducting thin plate with an impedance probe. The other is a stainless steel tube with a copper shell attached to its outer surface and scanned by a transmitter-receiver probe. In both problems, the calculated probe responses show good agreement with the analytical and experimental data.

  8. A Problem-Solving Approach to Addressing Current Global Challenges in Education

    ERIC Educational Resources Information Center

    Chapman, Judith D.; Aspin, David N.

    2013-01-01

    This paper begins with an analysis of global problems shaping education, particularly as they impact upon learning and life chances. In addressing these problems a range of philosophical positions and controversies are considered, including: traditional romantic and institutional views of schooling; and more recent maximalist, neo-liberal,…

  9. Reading Problems, Attentional Deficits, and Current Mental Health Status in Adjudicated Adolescent Males

    ERIC Educational Resources Information Center

    O'Brien, Natalie; Langhinrichsen-Rohling, Jennifer; Shelley-Tremblay, John

    2007-01-01

    This study examined the prevalence of reading problems and self-reported symptoms of attentional deficits in a sample of adjudicated adolescent males (N = 101) aged 12 to 18 years who were residing in an alternative sentencing residential program. Thirty-four percent of the youth had reading problems while only 9% of the boys had self-reported…

  10. Ionic liquid gating on atomic layer deposition passivated GaN: Ultra-high electron density induced high drain current and low contact resistance

    NASA Astrophysics Data System (ADS)

    Zhou, Hong; Du, Yuchen; Ye, Peide D.

    2016-05-01

    Herein, we report on achieving ultra-high electron density (exceeding 1014 cm-2) in a GaN bulk material device by ionic liquid gating, through the application of atomic layer deposition (ALD) of Al2O3 to passivate the GaN surface. Output characteristics demonstrate a maximum drain current of 1.47 A/mm, the highest reported among all bulk GaN field-effect transistors, with an on/off ratio of 105 at room temperature. An ultra-high electron density exceeding 1014 cm-2 accumulated at the surface is confirmed via Hall-effect measurement and transfer length measurement. In addition to the ultra-high electron density, we also observe a reduction of the contact resistance due to the narrowing of the Schottky barrier width on the contacts. Taking advantage of the ALD surface passivation and ionic liquid gating technique, this work provides a route to study the field-effect and carrier transport properties of conventional semiconductors in unprecedented ultra-high charge density regions.

  11. Intergenerational Contact: A Way to Counteract Ageism.

    ERIC Educational Resources Information Center

    Peacock, E. Winnifred; Talley, William M.

    1984-01-01

    Examines the problem of ageism and questions some sociocultural barriers and prevalent attitudes that promote such behavior. Benefits of intergenerational contact are emphasized. Discusses some means of bringing together age groups and describes some of the current projects in this area which have been successful. (JAC)

  12. A Current Review of Multisystemic Therapy: A Social-Ecological Approach to the Treatment of Conduct Problems among Adolescents

    ERIC Educational Resources Information Center

    Harpell, Jody V.; Andrews, Jac

    2006-01-01

    A current empirical review of the treatment efficacy of Multisystemic Therapy (MST) for adolescent conduct problems (CP) was conducted. Conclusions based on this review suggest that MST can be a very powerful alternative to the usual legal and social service approaches (e.g. justice system, day treatment programs) used in the treatment of…

  13. Sleep Problems in Children with Attention Deficit/Hyperactivity Disorder: Current Status of Knowledge and Appropriate Management.

    PubMed

    Tsai, Ming-Horng; Hsu, Jen-Fu; Huang, Yu-Shu

    2016-08-01

    Attention deficit hyperactivity disorder (ADHD) affects approximately 5 % of children and adolescents, and sleep problems are common in these patients. There is growing evidence informing the significant importance of sleep problems in youth with ADHD. The sleep problems in children with ADHD include specific sleep disorders and sleep disturbances due to comorbid psychiatric disorders or ADHD medications. The specific sleep disorders of ADHD children include behaviorally based insomnia, sleep-disordered breathing, and restless legs syndrome/periodic limb movement disorder. Current practices on the management of sleep problems for ADHD children are based mostly on expert consensus, whereas more evidence-based literature can be found only recently. Assessment of the sleep conditions in ADHD children before initiation of pharmacotherapy is the currently recommended guideline, and good sleep hygiene can be considered as the first-line treatment option. In addition to modifying the dose regimens, formulation, or alternative stimulants when sleep problems are encountered in ADHD children, atomoxetine, once daily guanfacine extended release, and melatonin are potential choices for ADHD children with more severe sleep problems. In this review, we aimed to provide the most updated information, preferably based on meta-analyses, systemic review, and randomized controlled trials published in the latest 3 years, in order to be clinically useful for practitioners and clinicians. PMID:27357497

  14. Voltage versus Current, or the Problem of the Chicken and the Egg

    ERIC Educational Resources Information Center

    Silva, Antonio Alberto; Soares, Rolando

    2007-01-01

    In an electric circuit, is it the current that causes the voltage, or the inverse? This is a false dilemma, as shown by an introductory and qualitative approach to a circuit as a system. (Contains 9 figures and 7 footnotes.)

  15. Mutual Inductance Problem for a System Consisting of a Current Sheet and a Thin Metal Plate

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    Rapid inspection of aircraft structures for flaws is of vital importance to the commercial and defense aircraft industry. In particular, inspecting thin aluminum structures for flaws is the focus of a large scale R&D effort in the nondestructive evaluation (NDE) community. Traditional eddy current methods used today are effective, but require long inspection times. New electromagnetic techniques which monitor the normal component of the magnetic field above a sample due to a sheet of current as the excitation, seem to be promising. This paper is an attempt to understand and analyze the magnetic field distribution due to a current sheet above an aluminum test sample. A simple theoretical model, coupled with a two dimensional finite element model (FEM) and experimental data will be presented in the next few sections. A current sheet above a conducting sample generates eddy currents in the material, while a sensor above the current sheet or in between the two plates monitors the normal component of the magnetic field. A rivet or a surface flaw near a rivet in an aircraft aluminum skin will disturb the magnetic field, which is imaged by the sensor. Initial results showed a strong dependence of the flaw induced normal magnetic field strength on the thickness and conductivity of the current-sheet that could not be accounted for by skin depth attenuation alone. It was believed that the eddy current imaging method explained the dependence of the thickness and conductivity of the flaw induced normal magnetic field. Further investigation, suggested the complexity associated with the mutual inductance of the system needed to be studied. The next section gives an analytical model to better understand the phenomenon.

  16. Self-Monitoring Interventions for Students with Behavior Problems: A Systematic Review of Current Research

    ERIC Educational Resources Information Center

    Bruhn, Allison; McDaniel, Sara; Kreigh, Christi

    2015-01-01

    Explicitly teaching skills associated with self-determination has been promoted to support students' independence and control over their own lives. This is especially important for students with behavior problems. One self-determination skill or behavior that has been studied widely is self-monitoring. Although multiple reviews of various…

  17. Current Administrative Problems in Reading. Highlights of the 1967 Pre-Convention Institutes.

    ERIC Educational Resources Information Center

    Berg, Paul C., Ed.; George, John E., Ed.

    Five papers concerning administrative problems in reading discuss administrative innovation, reading research, inservice education, and program funding. Forces promoting innovation include the federal government, industry, and educational research, the force which is seen as the basis for progress in education. Learning resource centers,…

  18. Involvement in a Current Problem as a Basis for Writing (Instructional Note).

    ERIC Educational Resources Information Center

    Guiher-Huff, Susan

    1990-01-01

    Describes a freshman composition class in which students write essays about pollution. Explains that students classified and divided problems, cited examples, explored pollution's processes, used narrative, and offered comparisons. Describes how students prepared cause-and-effect oral presentations and then wrote persuasive letters. Concludes that…

  19. The Current State and Problems of the Prevention of Homelessness and Neglect of Minor Children

    ERIC Educational Resources Information Center

    Vetrov, Iu. P.

    2006-01-01

    One of the most urgent problems of Russian society today remains children's homelessness and neglect. This social phenomenon, which has come about due to a number of factors, is characterized by the following indicators: (1) More than 100,000 children have been left without parental care; and (2) The number of parents who have been stripped of…

  20. AGRICULTURAL LABOR--THE PROBLEM, ATTEMPTS AT ORGANIZATION, CURRENT LAWS, AND WHAT ARE THE ISSUES.

    ERIC Educational Resources Information Center

    CALL, DAVID

    THE NUMBER OF HIRED FARM WORKERS IS DECREASING WITH THE INCREASED USE OF LABORSAVING FARM MACHINERY AND TECHNOLOGY WHICH ALLOWS GREATER OUTPUT PER WORKER. THE LOW WAGE SCALE PREVALENT IN AGRICULTURE IS THE MAJOR CAUSE OF THE FARM LABOR PROBLEM. WAGE RATES ARE DIFFICULT TO MEASURE ACCURATELY BECAUSE OF A GREAT DIVERSITY IN METHODS OF PAYMENT AND…

  1. BISON Contact Improvements CASL FY14 Report

    SciTech Connect

    B. W. Spencer; J. D. Hales; D. R. Gaston; D. A. Karpeev; R. L. Williamson; S. R. Novascone; D. M. Perez; R. J. Gardner; K. A. Gamble

    2014-09-01

    The BISON code is the foundation for multiple fuel performance modeling efforts, and is cur- rently under heavy development. For a variety of fuel forms, the effects of heat conduction across a gap and mechanical contact between components of a fuel system are very significant. It is thus critical that BISON have robust capabilities for enforcement of thermal and mechanical contact. BISON’s solver robustness has generally been quite good before mechanical contact between the fuel and cladding occurs, but there have been significant challenges obtaining converged so- lutions once that contact occurs and the solver begins to enforce mechanical contact constraints. During the current year, significant development effort has been focused on the enforcement of mechanical contact to provide improved solution robustness. In addition to this work to improve mechanical contact robustness, an investigation into ques- tionable results attributable to thermal contact has been performed. This investigation found that the order of integration typically used on the surfaces involved in thermal contact was not suffi- ciently high. To address this problem, a new option was provided to permit the use of a different integration order for surfaces, and new usage recommendations were provided.

  2. Analysis of leakage current mechanisms in Pt/Au Schottky contact on Ga-polarity GaN by Frenkel-Poole emission and deep level studies

    SciTech Connect

    Rao, Peta Koteswara; Park, Byungguon; Lee, Sang-Tae; Noh, Young-Kyun; Kim, Moon-Deock; Oh, Jae-Eung

    2011-07-01

    We report the Frenkel-Poole emission in Pt/Au Schottky contact on Ga-polarity GaN grown by molecular beam epitaxy using current-voltage-temperature (I-V-T) characteristics in the temperature ranging from 200 K to 375 K. Using thermionic emission model, the estimated Schottky barrier height is 0.49 eV at 200 K and 0.83 eV at 375 K, respectively, and it is observed that the barrier height increases with increase in temperature. The extracted emission barrier height ({phi}{sub t}) for Ga-polarity GaN Schottky diode by Frenkel-Poole theory is about 0.15 eV. Deep level transient spectroscopy study shows a deep level with activation energy of 0.44 eV, having capture cross-section 6.09 x 10{sup -14} cm{sup 2}, which is located between the metal and semiconductor interface, and trap nature is most probably associated with dislocations in Ga-polarity GaN. The analysis of I-V-T characteristics represents that the leakage current is due to effects of electrical field and temperature on the emission of electron from a trap state near the metal-semiconductor interface into continuum states associated with conductive dislocations in Ga-polarity GaN Schottky diode.

  3. Analysis of leakage current mechanisms in Pt/Au Schottky contact on Ga-polarity GaN by Frenkel-Poole emission and deep level studies

    NASA Astrophysics Data System (ADS)

    Rao, Peta Koteswara; Park, Byungguon; Lee, Sang-Tae; Noh, Young-Kyun; Kim, Moon-Deock; Oh, Jae-Eung

    2011-07-01

    We report the Frenkel-Poole emission in Pt/Au Schottky contact on Ga-polarity GaN grown by molecular beam epitaxy using current-voltage-temperature (I-V-T) characteristics in the temperature ranging from 200 K to 375 K. Using thermionic emission model, the estimated Schottky barrier height is 0.49 eV at 200 K and 0.83 eV at 375 K, respectively, and it is observed that the barrier height increases with increase in temperature. The extracted emission barrier height (ϕt) for Ga-polarity GaN Schottky diode by Frenkel-Poole theory is about 0.15 eV. Deep level transient spectroscopy study shows a deep level with activation energy of 0.44 eV, having capture cross-section 6.09 × 10-14 cm2, which is located between the metal and semiconductor interface, and trap nature is most probably associated with dislocations in Ga-polarity GaN. The analysis of I-V-T characteristics represents that the leakage current is due to effects of electrical field and temperature on the emission of electron from a trap state near the metal-semiconductor interface into continuum states associated with conductive dislocations in Ga-polarity GaN Schottky diode.

  4. Current Welfare Problems Facing Horses in Great Britain as Identified by Equine Stakeholders

    PubMed Central

    Horseman, Susan V.; Buller, Henry

    2016-01-01

    Despite growing concerns about the welfare of horses in Great Britain (GB) there has been little surveillance of the welfare status of the horse population. Consequently we have limited knowledge of the range of welfare problems experienced by horses in GB and the situations in which poor welfare occurs. Thirty-one in-depth interviews were conducted with a cross -section of equine stakeholders, in order to explore their perceptions of the welfare problems faced by horses in GB. Welfare problems relating to health, management and riding and training were identified, including horses being under or over weight, stabling 24 hours a day and the inappropriate use of training aids. The interviewees also discussed broader contexts in which they perceived that welfare was compromised. The most commonly discussed context was where horses are kept in unsuitable environments, for example environments with poor grazing. The racing industry and travellers horses were identified as areas of the industry where horse welfare was particularly vulnerable to compromise. Lack of knowledge and financial constraints were perceived to be the root cause of poor welfare by many interviewees. The findings give insight into the range of welfare problems that may be faced by horses in GB, the contexts in which these may occur and their possible causes. Many of the problems identified by the interviewees have undergone limited scientific investigation pointing to areas where further research is likely to be necessary for welfare improvement. The large number of issues identified suggests that some form of prioritisation may be necessary to target research and resources effectively. PMID:27501387

  5. Current Welfare Problems Facing Horses in Great Britain as Identified by Equine Stakeholders.

    PubMed

    Horseman, Susan V; Buller, Henry; Mullan, Siobhan; Whay, Helen R

    2016-01-01

    Despite growing concerns about the welfare of horses in Great Britain (GB) there has been little surveillance of the welfare status of the horse population. Consequently we have limited knowledge of the range of welfare problems experienced by horses in GB and the situations in which poor welfare occurs. Thirty-one in-depth interviews were conducted with a cross -section of equine stakeholders, in order to explore their perceptions of the welfare problems faced by horses in GB. Welfare problems relating to health, management and riding and training were identified, including horses being under or over weight, stabling 24 hours a day and the inappropriate use of training aids. The interviewees also discussed broader contexts in which they perceived that welfare was compromised. The most commonly discussed context was where horses are kept in unsuitable environments, for example environments with poor grazing. The racing industry and travellers horses were identified as areas of the industry where horse welfare was particularly vulnerable to compromise. Lack of knowledge and financial constraints were perceived to be the root cause of poor welfare by many interviewees. The findings give insight into the range of welfare problems that may be faced by horses in GB, the contexts in which these may occur and their possible causes. Many of the problems identified by the interviewees have undergone limited scientific investigation pointing to areas where further research is likely to be necessary for welfare improvement. The large number of issues identified suggests that some form of prioritisation may be necessary to target research and resources effectively. PMID:27501387

  6. The Experimental Investigation of the Missing N*- and Δ-RESONANCES Problem:. Current Status and Perspectives

    NASA Astrophysics Data System (ADS)

    Sumachev, V. V.; Bekrenev, V. S.; Beloglazov, Yu. A.; Filimonov, E. A.; Kovalev, A. I.; Kozlenko, N. G.; Kruglov, S. P.; Kulbardis, A. A.; Lopatin, I. V.; Novinsky, D. V.; Shchedrov, V. A.; Trautman, V. Yu.; Alekseev, I. G.; Budkovsky, P. E.; Kanavets, V. P.; Koroleva, L. I.; Morozov, B. V.; Nesterov, V. M.; Ryltsov, V. V.; Sulimov, A. D.; Svirida, D. N.; Bazhanov, N. A.; Bunyatova, E. I.

    2007-11-01

    Numerous attempts to create a model that would exactly reproduce the N* - and Δ - resonances spectrum (that was presented in the Review of Particle Physics) failed. The existing models usually predicted considerably more resonances (twice or more in number) than were found in elastic πN - scattering. This problem is known as the problem of "missing" resonances. The recent partial wave analysis (PWA) SP06 that was made at George Washington University (2006) and included the modern experimental data revealed considerably fewer (approximately half) the N*- and Δ-resonances than those presented in the Review of Particle Physics (RPP) tables (2006). This disagreement invites further experimental investigation of the pion-nucleon interactions. Recent spin rotation parameter A and R measurements of the PNPI and PNPI-ITEP collaborations resolved a part of the twofold ambiguities of the PWA's. These results were used in the last PWA of the George Washington University (GWU) groups. The proposal for the additional measurements of the differential cross section and spin-rotation parameters R and A in the resonance region of the πN interactions is motivated. Such additional experiments are necessary to resolve the problem of the narrow (Γ < 30 MeV) baryon resonances existing and to complete monosemantic PWA of the πN elastic scattering.

  7. Asthma Management: Part I: An Overview of the Problem and Current Trends.

    ERIC Educational Resources Information Center

    Baker, Valerie O'Toole; Friedman, Janet; Schmitt, Rita

    2002-01-01

    Describes the pathophysiology of asthma and the types, risk factors, and current trends in management of the disease. The role of the school nurse in asthma management is outlined, including identifying children with asthma, evaluating the child's response to the asthma management plan, and controlling environmental factors that precipitate asthma…

  8. On the problems of stability and durability of field-emission current sources for electrovacuum devices

    NASA Astrophysics Data System (ADS)

    Yakunin, Alexander N.; Aban'shin, Nikolay P.; Akchurin, Garif G.; Akchurin, Georgy G.; Avetisyan, Yuri A.

    2016-03-01

    The results of the practical implementation of the concept of field-emission current source with high average current density of 0.1-0.3 A-cm-2 are shown. The durability of cathode samples at a level of 6000 hours is achieved under conditions of technical vacuum. A phenomenological model is suggested that describes the tunneling of both equilibrium and nonequilibrium electrons in a vacuum from the zone of concentration of electrostatic field. Conditions are discussed as the resulting increase in the emission current due to the connection mechanism of the photoelectric effect is thermodynamically favorable, that is not accompanied by an undesirable increase in the temperature of the local emission zone. It is shown that to ensure stability and durability of the cathode is also important to limit the concentration of equilibrium carriers using composite structures «DLC film on Mo substrate." This helps to reduce the criticality of the CVC. A possible alternative is to use a restrictive resistance in the cathode. However, this increases the heat losses and thus decreases assembly efficiency. The results of experimental studies of the structure showing the saturation of photoemission current component with an increase in operating voltage. This fact suggests the existence of an effective mechanism for control of emission at constant operating voltage. This is fundamentally important for the stabilization of field emission cathode, providing a reliability and durability. The single-photon processes and the small thickness DLC films (15-20 nm) provide high-speed process of control.

  9. Issues and Problems in the Current Development of Vocational Education in China

    ERIC Educational Resources Information Center

    Shi, Weiping

    2013-01-01

    Chinese vocational education is currently in its most optimal development period in history. This article discusses several challenges of different dimensions faced by vocational education in China as it develops, such as scale versus quality, development goals, a lifelong vocational education system, and creating model institutions; and puts…

  10. Using Adolescent Fiction That Deals with Current Problems and Lifestyles to Explore Contemporary Values.

    ERIC Educational Resources Information Center

    Schwartz, Sheila

    This paper argues that a value structure must be developed and taught in the schools. The values and principles contained in the Humanistic Manifesto II are examined in the context of current adolescent literature. Discussed are such books as "It's Not What You Expect" and "Mom, The Wolfman and Me" by Norma Klein; "First Person Singular" by Vida…

  11. Control of large space structures: Status report on achievements and current problems

    NASA Technical Reports Server (NTRS)

    Lyons, M. G.; Aubrun, J. N.

    1983-01-01

    The objectives, state-of-the-art, and problems of large space structures control are outlined. The general objectives range from basic deployment and maneuvering, where some vibration modes may be suppressed, to disturbance rejection for very high performance imaging applications. The controls selected generally must produce some combination of eigenvalue/eigenvector and loads modification in order to achieve the mission objectives. An experiment illustrating the dynamic control of a suspended circular plate is described. Analysis methods used in system modelling, signal processing, and process control and monitoring are discussed. Sensor and actuator performance are assessed.

  12. [Problems of work world and its impact on health. Current financial crisis].

    PubMed

    Tomasina, Fernando

    2012-06-01

    Health and work are complex processes. Besides, they are multiple considering the forms they take. These two processes are linked to each other and they are influenced by each other. According to this, it is possible to establish that work world is extremely complex and heterogeneous. In this world, "old" or traditional risks coexist with "modern risks", derived from the new models of work organization and the incorporation of new technologies. Unemployment, work relationships precariousness and work risks outsourcing are results of neoliberal strategies. Some negative results of health-sickness process derived from transformation in work world and current global economic crisis have been noticed in current work conditions. Finally, the need for reconstructing policies focusing on this situation derived from work world is suggested. PMID:23258747

  13. Problems and the potential direction of reforms for the current individual medical savings accounts in the Chinese health care system.

    PubMed

    Kong, Xiangjin; Yang, Yang; Gong, Fuqing; Zhao, Mingjie

    2012-12-01

    Individual health savings accounts are an important part of the current basic medical insurance system for urban workers in China. Since 1998 when the system of personal medical insurance accounts was first implemented, there has been considerable controversy over its function and significance within different social communities. This paper analyzes the main problems in the practical implementation of individual medical insurance accounts and discusses the social and cultural foundations for the establishment of family health savings accounts from the perspective of Chinese Confucian familism. Accordingly, it addresses the direction of the reform and the development of the current system of individual health insurance accounts in China. PMID:23192456

  14. Radioimmunodetection of cancer with monoclonal antibodies: current status, problems, and future directions

    SciTech Connect

    Murray, J.L.; Unger, M.W.

    1988-01-01

    Early studies of immunoscintography with affinity-purified /sup 131/I-labeled polyclonal antibodies reactive against oncofetal antigens such as carcinoembryonic antigen (CEA) were moderately successful in detecting metastatic colorectal carcinoma. However, because of low tumor to background ratios of isotope, background subtraction techniques using /sup 99/Tc-labeled albumin were required to visualize small lesions. Antisera were often of low titer and lacked specificity. These problems could be overcome for the most part following the development of highly specific monoclonal antibodies (MoAb) against a variety of tumor-associated antigens. A number of clinical trials using /sup 131/I- or /sup 111/In-labeled MoAb to image tumors have demonstrated successful localization without the use of subtraction techniques. Variables limiting the usefulness of murine MoAb for diagnosis have included increased localization in liver and spleen, tumor vascularity and heterogeneity of antigen expression, and development of human antimurine globulins. Methods to overcome some of these problems are discussed. Radiolabeled MoAb appear useful as an adjunct to conventional diagnostic techniques both as a means to predict which antibodies might be useful for treatment and, in select patients, as a basis for treatment decisions. 163 references.

  15. Current treatment of chronic hepatitis C in China: Dilemma and potential problems.

    PubMed

    Han, Qun-Ying; Liu, Zheng-Wen

    2016-05-21

    Major advances have been made in the treatment of chronic hepatitis C virus (HCV) infection with the advent of direct-acting antiviral agents (DAAs). China has the most cases of HCV infection worldwide, but none of the DAAs has been approved in mainland China so far, and interferon (IFN)-α-based treatment remains the standard of care. HCV patients without response or with contraindications to IFN-based therapy have no alternative options. However, many patients buy DAAs, especially the generic forms of sofosbuvir, from other countries or areas. Under these circumstances, the use of these drugs may cause many predictable and unpredictable problems in ethics, law and medical practice. Given the obstacles of legal accessibility to DAAs and the potential problems of obtaining and using DAAs in China, the early launching of the DAAs in China or the legalization of buying drugs from areas outside China and using these drugs in China is an urgent issue and needs to be dealt with as soon as possible, in the interest of the patients. PMID:27217693

  16. Current treatment of chronic hepatitis C in China: Dilemma and potential problems

    PubMed Central

    Han, Qun-Ying; Liu, Zheng-Wen

    2016-01-01

    Major advances have been made in the treatment of chronic hepatitis C virus (HCV) infection with the advent of direct-acting antiviral agents (DAAs). China has the most cases of HCV infection worldwide, but none of the DAAs has been approved in mainland China so far, and interferon (IFN)-α-based treatment remains the standard of care. HCV patients without response or with contraindications to IFN-based therapy have no alternative options. However, many patients buy DAAs, especially the generic forms of sofosbuvir, from other countries or areas. Under these circumstances, the use of these drugs may cause many predictable and unpredictable problems in ethics, law and medical practice. Given the obstacles of legal accessibility to DAAs and the potential problems of obtaining and using DAAs in China, the early launching of the DAAs in China or the legalization of buying drugs from areas outside China and using these drugs in China is an urgent issue and needs to be dealt with as soon as possible, in the interest of the patients. PMID:27217693

  17. Shock-interface interaction: Current research on the Richtmyer- Meshkov problem

    SciTech Connect

    Rupert, V.

    1991-07-17

    The basis for the study of the evolution of a shocked interface stems from the question of the Rayleigh-Taylor (RT) instability (Taylor 1950). Starting in the late 18th century, the stability of an interface submitted to gravitational forces was investigated for the case in which the density of one of the materials across the interface was negligible compared to the other. Taylor analyzed the case in which the Atwood number (ratio of the difference of the densities to their sum) is less than 1, and the acceleration of the system is constant. He determined that the interface was unstable to small perturbations only if the direction of the acceleration normal to the interface coincides with that of the density gradient. Richtmyer (1960) extended Taylor's analysis to the case of an implusive acceleration. His results implied that the interface would be unstable irrespective of the relative orientation of the velocity impulse and the density gradient. His predictions were verified experimentally by Meshkov (1969), and the Richtmyer-Meshkov (RM) instability became a subject of research in its own right. Experimental, numerical, and theoretical works address this problem. The RM problem has been studied with both the shock-tube and laser experiments. In this paper, only shock-tube work is considered. 48 refs., 6 figs.

  18. High-Performance Computing and Four-Dimensional Data Assimilation: The Impact on Future and Current Problems

    NASA Technical Reports Server (NTRS)

    Makivic, Miloje S.

    1996-01-01

    This is the final technical report for the project entitled: "High-Performance Computing and Four-Dimensional Data Assimilation: The Impact on Future and Current Problems", funded at NPAC by the DAO at NASA/GSFC. First, the motivation for the project is given in the introductory section, followed by the executive summary of major accomplishments and the list of project-related publications. Detailed analysis and description of research results is given in subsequent chapters and in the Appendix.

  19. Novel method for rapid in-situ hybridization of HER2 using non-contact alternating-current electric-field mixing

    PubMed Central

    Saito, Yoshitaro; Imai, Kazuhiro; Nakamura, Ryuta; Nanjo, Hiroshi; Terata, Kaori; Konno, Hayato; Akagami, Yoichi; Minamiya, Yoshihiro

    2016-01-01

    Human epidermal growth factor receptor 2 (HER2)-targeted agents are an effective approach to treating HER2-positive breast cancer patients. However, the lack of survival benefit in HER2-negative patients as well as the toxic effects and high cost of the drugs highlight the need for accurate and prompt assessment of HER2 status. Our aim was to evaluate the clinical utility of a novel rapid dual in-situ hybridization (RISH) method developed to facilitate hybridization. The method takes advantage of the non-contact mixing effect of an alternating current (AC) electric field. One hundred sixty-three specimens were used from patients diagnosed with primary breast cancers identified immunohistochemically as HER2 0/1(+), (2+) or (3+). The specimens were all tested using conventional dual in-situ hybridization (DISH), DISH with an automated slide stainer, and RISH. With RISH the HER2 test was completed within 6 h, as compared to 20–22 h needed for the standard protocol. Although RISH produced results more promptly using smaller amounts of labeled antibody, the staining and accuracy of HER2 status evaluation with RISH was equal to or greater than with DISH. These results suggest RISH could be used as a clinical tool to promptly determine HER2 status. PMID:27443187

  20. Novel method for rapid in-situ hybridization of HER2 using non-contact alternating-current electric-field mixing.

    PubMed

    Saito, Yoshitaro; Imai, Kazuhiro; Nakamura, Ryuta; Nanjo, Hiroshi; Terata, Kaori; Konno, Hayato; Akagami, Yoichi; Minamiya, Yoshihiro

    2016-01-01

    Human epidermal growth factor receptor 2 (HER2)-targeted agents are an effective approach to treating HER2-positive breast cancer patients. However, the lack of survival benefit in HER2-negative patients as well as the toxic effects and high cost of the drugs highlight the need for accurate and prompt assessment of HER2 status. Our aim was to evaluate the clinical utility of a novel rapid dual in-situ hybridization (RISH) method developed to facilitate hybridization. The method takes advantage of the non-contact mixing effect of an alternating current (AC) electric field. One hundred sixty-three specimens were used from patients diagnosed with primary breast cancers identified immunohistochemically as HER2 0/1(+), (2+) or (3+). The specimens were all tested using conventional dual in-situ hybridization (DISH), DISH with an automated slide stainer, and RISH. With RISH the HER2 test was completed within 6 h, as compared to 20-22 h needed for the standard protocol. Although RISH produced results more promptly using smaller amounts of labeled antibody, the staining and accuracy of HER2 status evaluation with RISH was equal to or greater than with DISH. These results suggest RISH could be used as a clinical tool to promptly determine HER2 status. PMID:27443187

  1. Current challenges for confronting the public health problem of snakebite envenoming in Central America.

    PubMed

    Gutiérrez, José María

    2014-01-01

    Snakebite envenoming is a serious public health problem in Central America, where approximately 5,500 cases occur every year. Panama has the highest incidence and El Salvador the lowest. The majority, and most severe, cases are inflicted by the pit viper Bothrops asper (family Viperidae), locally known as 'terciopelo', 'barba amarilla' or 'equis'. About 1% of the bites are caused by coral snakes of the genus Micrurus (family Elapidae). Despite significant and successful efforts in Central America regarding snakebite envenomings in the areas of research, antivenom manufacture and quality control, training of health professionals in the diagnosis and clinical management of bites, and prevention of snakebites, much remains to be done in order to further reduce the impact of this medical condition. This essay presents seven challenges for improving the confrontation of snakebite envenoming in Central America. Overcoming these challenges demands a coordinated partnership of highly diverse stakeholders though inter-sectorial and inter-programmatic interventions. PMID:24602234

  2. Presymplectic current and the inverse problem of the calculus of variations

    SciTech Connect

    Khavkine, Igor

    2013-11-15

    The inverse problem of the calculus of variations asks whether a given system of partial differential equations (PDEs) admits a variational formulation. We show that the existence of a presymplectic form in the variational bicomplex, when horizontally closed on solutions, allows us to construct a variational formulation for a subsystem of the given PDE. No constraints on the differential order or number of dependent or independent variables are assumed. The proof follows a recent observation of Bridges, Hydon, and Lawson [Math. Proc. Cambridge Philos. Soc. 148(01), 159–178 (2010)] and generalizes an older result of Henneaux [Ann. Phys. 140(1), 45–64 (1982)] from ordinary differential equations (ODEs) to PDEs. Uniqueness of the variational formulation is also discussed.

  3. Rising rates of vaccine exemptions: problems with current policy and more promising remedies.

    PubMed

    Constable, Catherine; Blank, Nina R; Caplan, Arthur L

    2014-04-01

    Parents of school-age children are increasingly claiming nonmedical exemptions to refuse vaccinations required for school entry. The resultant unvaccinated pockets in many areas of the country have been linked with outbreaks of vaccine-preventable diseases. Many states are now focused on reducing rates of nonmedical exemptions by making exemption processes more restrictive or burdensome for the exemptor. These strategies, however, pose ethical problems and may ultimately be inadequate. A shift to strategies that raise the financial liabilities of exemptors may lead to better success and prove ethically more sound. Potential areas of reform include tax law, health insurance, and private school funding programs. We advocate an approach that combines this type of incentive with more effective vaccination education. PMID:24530934

  4. Environmental problems in the People`s Republic of China: Current magnitude and possible control options

    SciTech Connect

    Bhadtti, N.; Biang, C.A.; Poch, L.A.; Tompkins, M.M.

    1995-09-01

    The People`s Republic of China has been undergoing rapid economic development over the past several decades. This development has taken place with little or no attention being paid to its environmental consequences. This situation has resulted in severe contamination of the air, water, and soil resources of China, with attendant damage to human and natural populations. This report determines the major causes of air, water, and soil pollution in China and assesses their extent and magnitude. It then examines the impacts of the pollutants on various components of the human and natural environment. It identifies possible regulatory and ameliorative options available to China to deal with these pollution problems and provides information on specific strategies and the costs associated with their implementation. The objective is to shed light on China`s pollution control and remediation requirements in the near future.

  5. On variational formulation of current drive problem in uniformly magnetized relativistic plasma

    NASA Astrophysics Data System (ADS)

    Hu, Y. M.; Hu, Y. J.

    2016-01-01

    A fully relativistic extension of the variational principle with the modified test function for the Spitzer function with momentum conservation in the electron-electron collision is investigated in uniformly magnetized plasma. The term of the momentum conserving constraint in Hirshman’s variational calculation is studied. The model developed is extended for arbitrary temperatures and covers exactly the asymptotic for u\\gg 1 when {{Z}\\text{eff}}\\gg 1 , and the results obtained are suited to facilitate the development of a rigorous variational formulation of current drive efficiency in tokamak plasma.

  6. Telocyte's contacts.

    PubMed

    Faussone-Pellegrini, Maria-Simonetta; Gherghiceanu, Mihaela

    2016-07-01

    Telocytes (TC) are an interstitial cell type located in the connective tissue of many organs of humans and laboratory mammals. By means of homocellular contacts, TC build a scaffold whose meshes integrity and continuity are guaranteed by those contacts having a mechanical function; those contacts acting as sites of intercellular communication allow exchanging information and spreading signals. Heterocellular contacts between TC and a great variety of cell types give origin to mixed networks. TC, by means of all these types of contacts, their interaction with the extracellular matrix and their vicinity to nerve endings, are part of an integrated system playing tissue/organ-specific roles. PMID:26826524

  7. Chloramphenicol Derivatives as Antibacterial and Anticancer Agents: Historic Problems and Current Solutions

    PubMed Central

    Dinos, George P.; Athanassopoulos, Constantinos M.; Missiri, Dionissia A.; Giannopoulou, Panagiota C.; Vlachogiannis, Ioannis A.; Papadopoulos, Georgios E.; Papaioannou, Dionissios; Kalpaxis, Dimitrios L.

    2016-01-01

    Chloramphenicol (CAM) is the D-threo isomer of a small molecule, consisting of a p-nitrobenzene ring connected to a dichloroacetyl tail through a 2-amino-1,3-propanediol moiety. CAM displays a broad-spectrum bacteriostatic activity by specifically inhibiting the bacterial protein synthesis. In certain but important cases, it also exhibits bactericidal activity, namely against the three most common causes of meningitis, Haemophilus influenzae, Streptococcus pneumoniae and Neisseria meningitidis. Resistance to CAM has been frequently reported and ascribed to a variety of mechanisms. However, the most important concerns that limit its clinical utility relate to side effects such as neurotoxicity and hematologic disorders. In this review, we present previous and current efforts to synthesize CAM derivatives with improved pharmacological properties. In addition, we highlight potentially broader roles of these derivatives in investigating the plasticity of the ribosomal catalytic center, the main target of CAM. PMID:27271676

  8. [Current problems in the prevention and treatment of infections in patients with cirrhosis].

    PubMed

    Bellot, Pablo; Jara Pérez López, Neftalí; Martínez Moreno, Belén; Such, José

    2010-12-01

    Infections in patients with cirrhosis are a common complication causing substantial morbidity and mortality. Bacterial translocation plays an important role in the pathogenesis of many infections in cirrhosis. In turn, infections are involved in the pathogenesis of many episodes of decompensated cirrhosis, such as esophageal variceal bleeding, renal insufficiency, the hemodynamic alterations of cirrhosis, and hepatic encephalopathy. Spontaneous bacterial peritonitis is currently the most frequent infection in cirrhosis. Mortality from this entity has recently decreased due to early diagnosis, the use of appropriate antibiotic therapy, and albumin administration. However, infections due to multiresistant microorganisms have recently increased, leading to greater mortality. Primary prophylaxis with quinolones is effective in preventing infections and is associated with lower mortality in a selected population of patients with liver cirrhosis. PMID:20444525

  9. Chloramphenicol Derivatives as Antibacterial and Anticancer Agents: Historic Problems and Current Solutions.

    PubMed

    Dinos, George P; Athanassopoulos, Constantinos M; Missiri, Dionissia A; Giannopoulou, Panagiota C; Vlachogiannis, Ioannis A; Papadopoulos, Georgios E; Papaioannou, Dionissios; Kalpaxis, Dimitrios L

    2016-01-01

    Chloramphenicol (CAM) is the D-threo isomer of a small molecule, consisting of a p-nitrobenzene ring connected to a dichloroacetyl tail through a 2-amino-1,3-propanediol moiety. CAM displays a broad-spectrum bacteriostatic activity by specifically inhibiting the bacterial protein synthesis. In certain but important cases, it also exhibits bactericidal activity, namely against the three most common causes of meningitis, Haemophilus influenzae, Streptococcus pneumoniae and Neisseria meningitidis. Resistance to CAM has been frequently reported and ascribed to a variety of mechanisms. However, the most important concerns that limit its clinical utility relate to side effects such as neurotoxicity and hematologic disorders. In this review, we present previous and current efforts to synthesize CAM derivatives with improved pharmacological properties. In addition, we highlight potentially broader roles of these derivatives in investigating the plasticity of the ribosomal catalytic center, the main target of CAM. PMID:27271676

  10. Carbon Nanotubes Exposure Risk Assessment: From Toxicology to Epidemiologic Studies (Overview of the Current Problem)

    PubMed Central

    Fatkhutdinova, L. M.; Khaliullin, T. O.; Shvedova, A. A.

    2015-01-01

    Nanoscale size and fiber like structure of carbon nanotubes (CNTs) may determine high reactivity and penetration, as well as the pathogenicity of asbestos and other mineral fibers. Despite many in vitro and in vivo studies, the absence of full-scale data on CNT effects on human health clearly point out the necessity for epidemiological studies. Currently, several projects are initiated worldwide on studying health risks associated with the inhalation of industrial CNTs, including NIOSH-promoted research (United States), the European CANTES study, and the Russian CNT-ERA project. Studies comprising several successive steps, such as CNT exposure assessment in occupational settings, toxicological evaluation, and epidemiological observations, are critical for determining material safety and use criteria. PMID:26457172

  11. Current challenges for confronting the public health problem of snakebite envenoming in Central America

    PubMed Central

    2014-01-01

    Snakebite envenoming is a serious public health problem in Central America, where approximately 5,500 cases occur every year. Panama has the highest incidence and El Salvador the lowest. The majority, and most severe, cases are inflicted by the pit viper Bothrops asper (family Viperidae), locally known as ‘terciopelo’, ‘barba amarilla’ or ‘equis’. About 1% of the bites are caused by coral snakes of the genus Micrurus (family Elapidae). Despite significant and successful efforts in Central America regarding snakebite envenomings in the areas of research, antivenom manufacture and quality control, training of health professionals in the diagnosis and clinical management of bites, and prevention of snakebites, much remains to be done in order to further reduce the impact of this medical condition. This essay presents seven challenges for improving the confrontation of snakebite envenoming in Central America. Overcoming these challenges demands a coordinated partnership of highly diverse stakeholders though inter-sectorial and inter-programmatic interventions. PMID:24602234

  12. Obesity, More than a 'Cosmetic' Problem. Current Knowledge and Future Prospects of Human Obesity Genetics.

    PubMed

    Shabana; Hasnain, Shahida

    2016-02-01

    Obesity has been designated as a global epidemic by WHO as its prevalence has increased at an alarming rate in the last few decades worldwide. It is a risk factor for diabetes, hypertension, cardiovascular problems, etc. The contribution of genes to the development of obesity was confirmed in late twentieth century. The concept of monogenic obesity came with the identification of leptin, and mutations in its gene, followed by the discovery of more single gene mutations. However, the recent explosion of obesity could not be explained on the basis of these rare mutations and it was after the first genome-wide association study in 2007 that made possible the identification of different effect size variants in many candidate and non-candidate genes acting in a quantitative way to add to body weight. These studies laid down the basis for polygenic cause of common forms of obesity. The role of epigenetic regulation in the modulation of energy regulation pathway was another important explanation put forward in the latter half of the past decade. Taking into account the quantitative contribution of different variants has given the concept of obesity risk scoring in order to score individuals into different risk groups so as to decide for treatment options. PMID:26581848

  13. Non-insulin antidiabetic therapy in cardiac patients: current problems and future prospects.

    PubMed

    Fisman, Enrique Z; Motro, Michael; Tenenbaum, Alexander

    2008-01-01

    Five types of oral antihyperglycemic drugs are currently approved for the treatment of diabetes: biguanides, sulfonylureas, meglitinides, glitazones and alpha-glucosidase inhibitors. We briefly review the cardiovascular effects of the most commonly used antidiabetic drugs in these groups in an attempt to improve knowledge and awareness regarding their influences and potential risks when treating patients with coronary artery disease (CAD). Regarding biguanides, gastrointestinal disturbances such as diarrhea are frequent, and the intestinal absorption of group B vitamins and folate is impaired during chronic therapy. This deficiency may lead to increased plasma homocysteine levels which, in turn, accelerate the progression of vascular disease due to adverse effects on platelets, clotting factors, and endothelium. The existence of a graded association between homocysteine levels and overall mortality in patients with CAD is well established. In addition, metformin may lead to lethal lactic acidosis, especially in patients with clinical conditions that predispose to this complication, such as heart failure or recent myocardial infarction. Sulfonylureas avoid ischemic preconditioning. During myocardial ischemia, they may prevent opening of the ATP-dependent potassium channels, impeding the necessary hyperpolarization that protects the cell by blocking calcium influx. Meglitinides may exert similar effects due to their analogous mechanism of action. During treatment with glitazones, edema has been reported in 5% of patients, and these drugs are contraindicated in diabetics with NYHA class III or IV cardiac status. The long-term effects of alpha-glucosidase inhibitors on morbidity and mortality rates and on diabetic micro- and macrovascular complications is still unknown. Combined sulfonylurea/metformin therapy reveals additive effects on mortality. Four points should be mentioned: (1) the five oral antidiabetic drug groups present proven or potential cardiac hazards; (2

  14. Current problems in treating tuberculosis in Italian HIV-infected patients.

    PubMed

    Monno, L; Angarano, G; Carbonara, S; Infante, G; Coppola, S; Costa, D; Quarto, M; Pastore, G

    1993-08-01

    31 Italian HIV-infected patients with newly diagnosed tuberculosis (TB) were reviewed to verify the effectiveness of the most common antituberculosis drugs. The patients were mostly intravenous drug addicts (90%), and 14 (45%) had recently been in prison. 5 patients (16%) had pulmonary TB, 15 (48%) had both pulmonary and extrapulmonary involvement, and 11 (30%) had extrapulmonary disease alone. 6 patients received the association of HRZ, and a 4-drug association including ethambutol was given to an additional 7 patients. The remaining 18 patients were administered the association of HRE. Response to therapy was good in 13 patients (42%), and lacking or delayed in 18 patients (58%). Treatment failure was partly related to the increased occurrence in our area of Mycobacterium tuberculosis strains resistant to the first-line anti-tuberculosis drugs. These observations, along with the need of a faster response to therapy than that currently obtained for TB in AIDS and in view of epidemiological effects, should prompt the definition of alternative therapeutic and prophylactic regimens. PMID:8219181

  15. WKB approach to the problem of MHD shock propagation through the heliospheric current sheet

    NASA Astrophysics Data System (ADS)

    Uralova, S. V.; Uralov, A. M.

    1994-07-01

    The interplanetary shock wave front shape and intensity are calculated numerically by means of the Wentzel-Kramer-Brillouin (WKB)-approach, with nonlinear effects taken into account. The solar flare is modelled as an isotropic point explosion at the solar wind base. The heliospheric current sheet (HCS) is represented by a radially diverging stream with a higher plasma concentration and a lower wind speed. Fast magnetosonic shock wave propagation along the HCS is connected with the effect of regular accumulation of the wave energy in the vicinity of the HCS. In this place the wave intensity is increased, and the corresponding front fragments go ahead to form a shock-wave forerunner as a 'pimple'. The 'pimple', in turn, is located inside quite a large, but less-contrast, 'dimple' in the wave surface. This 'dimple' approximately coincides with the HCS stream contours. If the flare is outside the HCS boundaries, the picture discussed above is conserved, but asymmetry effects arise. Thus the interplanetary shock is stronger when the Earth's observer and the flare are on the same side of the HCS and is weaker in the opposite case.

  16. Current Progress in Tissue Engineering of Heart Valves: Multiscale Problems, Multiscale Solutions

    PubMed Central

    Cheung, Daniel Y; Duan, Bin; Butcher, Jonathan T.

    2016-01-01

    Introduction Heart valve disease is an increasingly prevalent and clinically serious condition. There are no clinically effective biological diagnostics or treatment strategies. The only recourse available is replacement with a prosthetic valve, but the inability of these devices to grow or respond biologically to their environments necessitates multiple resizing surgeries and life-long coagulation treatment, especially in children. Tissue engineering has a unique opportunity to impact heart valve disease by providing a living valve conduit, capable of growth and biological integration. Areas covered This review will cover current tissue engineering strategies in fabricating heart valves and their progress towards the clinic, including molded scaffolds using naturally-derived or synthetic polymers, decellularization, electrospinning, 3D bioprinting, hybrid techniques, and in vivo engineering. Expert opinion While much progress has been made to create functional living heart valves, a clinically viable product is not yet realized. The next leap in engineered living heart valves will require a deeper understanding of how the natural multi-scale structural and biological heterogeneity of the tissue ensures its efficient function. Related, improved fabrication strategies must be developed that can replicate this de novo complexity, which is likely instructive for appropriate cell differentiation and remodeling whether seeded with autologous stem cells in vitro or endogenously recruited cells. PMID:26027436

  17. Current problems in communication from the weather forecast in the prevention of hydraulic and hydrogeological risk

    NASA Astrophysics Data System (ADS)

    Fazzini, Massimiliano; Vaccaro, Carmela

    2014-05-01

    The Italian territory is one of the most fragile hydraulic and hydro geologic of the world, due to its complexity physiographic, lithological and above meteo-climatic too. Moreover, In recent years, the unhappy urbanization, the abandonment of mountain areas and countryside have fostered hydro geological instability, ever more devastating, in relation to the extremes of meteorological events. After the dramatic floods and landscapes of the last 24 months - in which more than 50 people died - it is actually open a public debate on the issues related to prevention, forecasting and management of hydro-meteorological risk. Aim of the correct weather forecasting at different spatial and temporal scales is to avoid or minimize the potential occurrence of damage or human losses resulting from the increasingly of frequent extreme weather events. In Italy, there are two major complex problems that do not allow for effective dissemination of the correct weather forecasting. First, the absence of a national meteorological service - which can ensure the quality of information. In this regard, it is at an advanced stage the establishment of a unified national weather service - formed by technicians to national and regional civil protection and the Meteorological Service of the Air Force, which will ensure the quality of the prediction, especially through exclusive processing of national and local weather forecasting and hydro geological weather alert. At present, however, this lack favors the increasing diffusion of meteorological sites more or less professional - often totally not "ethical" - which, at different spatial scales, tend to amplify the signals from the weather prediction models, describing them the users of the web such as exceptional or rare phenomena and often causing unjustified alarmism. This behavior is almost always aimed at the desire of give a forecast before other sites and therefore looking for new commercial sponsors, with easy profits. On the other hand

  18. Effective probe response calculation using impedance boundary condition in eddy current NDE problems with massive conducting regions present

    SciTech Connect

    Badics, Z.; Matsumoto, Y.; Aoki, K.; Nakayasu, F.

    1996-05-01

    A 3-D finite element scheme is described for calculating probe responses in eddy current NDE problems if massive conducting regions with small penetration depth are in the vicinity of the host specimen. These problems are related to the eddy current inspection of the tube support plate or tube sheet zones in PWR steam generator tubing. Recently, an efficient finite element scheme has been introduced to calculate the probe responses outside these zones. As a sequel to that work, the authors extend here the technique for the tube support plate and the tube sheet zones. They use impedance boundary conditions (IBC) on the surface of the massive conductors and evaluate the probe responses due to these components by performing an integral over these IBC surfaces, thereby ensuring the same accuracy as in the previous work for the flaw signals. Benchmark problems--models of tube support plate zones with defects--have been measured and analyzed. The calculated probe responses show good agreement with the experimental data.

  19. [Current problems of microbial safety of the interior environment of orbital stations after extended period of operation].

    PubMed

    Viktorov, A N; Novikova, N D; Polikarpov, N A; Gorshkova, V P; Konstantinova, S V

    1995-01-01

    The authors give considerations to one of the core hygienic problems arising in the process of long-term operation of orbital stations, i.e. ensuring microbial health of the milieu interior. Data pertaining the origin, interactions, and transformation of the microbial risk factors are analyzed as applied to this class of spacecraft. A concept of microbial health of the milieu interior including both medical and technological aspects relating to the reliability of space hardware is proposed. Based on the result of investigations in space flight, the developed criteria and indices of microbial health can be turned to practical use. The currently central tasks to be solved within the context of the problem and in view of the construction of international space station ALPHA are listed. PMID:8664877

  20. Case studies: Application of SEA in provincial level expressway infrastructure network planning in China - Current existing problems

    SciTech Connect

    Zhou Kaiyi; Sheate, William R.

    2011-11-15

    Since the Law of the People's Republic of China on Environmental Impact Assessment was enacted in 2003 and Huanfa 2004 No. 98 was released in 2004, Strategic Environmental Assessment (SEA) has been officially being implemented in the expressway infrastructure planning field in China. Through scrutinizing two SEA application cases of China's provincial level expressway infrastructure (PLEI) network plans, it is found that current SEA practice in expressway infrastructure planning field has a number of problems including: SEA practitioners do not fully understand the objective of SEA; its potential contributions to strategic planning and decision-making is extremely limited; the employed application procedure and prediction and assessment techniques are too simple to bring objective, unbiased and scientific results; and no alternative options are considered. All these problems directly lead to poor quality SEA and consequently weaken SEA's effectiveness.

  1. A general-purpose contact detection algorithm for nonlinear structural analysis codes

    SciTech Connect

    Heinstein, M.W.; Attaway, S.W.; Swegle, J.W.; Mello, F.J.

    1993-05-01

    A new contact detection algorithm has been developed to address difficulties associated with the numerical simulation of contact in nonlinear finite element structural analysis codes. Problems including accurate and efficient detection of contact for self-contacting surfaces, tearing and eroding surfaces, and multi-body impact are addressed. The proposed algorithm is portable between dynamic and quasi-static codes and can efficiently model contact between a variety of finite element types including shells, bricks, beams and particles. The algorithm is composed of (1) a location strategy that uses a global search to decide which slave nodes are in proximity to a master surface and (2) an accurate detailed contact check that uses the projected motions of both master surface and slave node. In this report, currently used contact detection algorithms and their associated difficulties are discussed. Then the proposed algorithm and how it addresses these problems is described. Finally, the capability of the new algorithm is illustrated with several example problems.

  2. Platelet-rich plasma therapy for knee joint problems: review of the literature, current practice and legal perspectives in Korea.

    PubMed

    Park, Yong-Geun; Han, Seung Beom; Song, Sang Jun; Kim, Tae Jin; Ha, Chul-Won

    2012-06-01

    Platelet-rich plasma (PRP) is a concentrate extract of platelets from autologous blood, and represents a possible treatment option for the stimulation and acceleration of soft-tissue healing and regeneration in orthopedics. Currently, the availability of devices for outpatient preparation and delivery contributes to the increase in the clinical use of PRP therapy in practical setting of orthopedic fields. However, there is still paucity of scientific evidence in the literature to prove efficacy of PRP therapy for the treatment of ligament or tendon problems around the knee joint. Moreover, strong evidence from well-designed clinical trials to support the PRP therapy for osteoarthritis of the knee joint is yet scanty in the literature. Scientific studies need to be performed to assess clinical indications, efficacy, and safety of PRP, and this will require high powered randomized controlled trials. Nonetheless, some hospitals exaggeratedly advertise PRP procedures as the ultimate treatment and a novel technology with abundant scientific evidence for the treatment of knee problems. As a matter of fact, PRP protocols are currently approved only for use in clinical trials and research, and are not allowed for treatment purpose by any institutions in Korea. At present, clinical use of PRP therapy for ligament or tendon problems or osteoarthritis of knee joint is defined as illegal medical practice, regardless of whether it is performed as a sole procedure or as a part of prolotherapy, because the safety and validity are not yet approved by the Ministry of Health and Welfare and Health Insurance Review and Assessment Service. Practicing physicians should remember that injection of PRP to patients by imposing medical charge is still illegal as per the current medical law in Korea. PMID:22708106

  3. On the interpretation of current-voltage curves in ionization chambers using the exact solution of the Thomson problem

    NASA Astrophysics Data System (ADS)

    Ridenti, M. A.; Pascholati, P. R.; Gonçalves, J. A. C.; Bueno, C. C.

    2015-09-01

    The I - ΔV characteristic curve of a well type ionization chamber irradiated with 192Ir sources (0.75 Ci-120 Ci) was fitted using the exact solution of the Thomson problem. The recombination coefficient and saturation current were estimated using this new approach. The saturation current was compared with the results of the conventional method based on Boag-Wilson formula. It was verified that differences larger than 1% between both methods only occurred at activities higher than 55 Ci. We concluded that this new approach is recommended for a more accurate estimate of the saturation current when it is not possible to measure currents satisfying the condition I /Isat > 0.95. From the calibration curve the average value of pairs of carriers created per unit volume was estimated to be equal to η = 8.1 ×10-3cm-3s-1 Bq-1 and from that value it was estimated that ~ 17 pairs were created on average per second for each decay of the source.

  4. Selective LPCVD tungsten for contact barrier applications

    SciTech Connect

    Levy, R.A.; Green, M.L.; Gallagher, P.K.; Ali, Y.S.

    1986-09-01

    This study assesses the use of selective LPCVD tungsten as a contact barrier in VLSI circuits. Measurements of the contact resistance and leakage current are evaluated as a function of variations in W deposition parameters, implant type, implant dosage, and metallization heat-treatment. Addition of SiF/sub 4/ to alter the equilibrium of the displacement reaction is seen to cause minimal erosion and encroachment of the Si contacts as well as produce low and thermally stable contact resistance to both n/sup +/ and p/sup +/ diffusions. For surface doping concentrations of 1.44 x 10/sup 20/ cm/sup -3/ As and 0.62 x 10/sup 20/ cm/sup -3/B, measured values for the contact resistance for 2.0 ..mu..m sized vias are near 30..cap omega... Such values are quite compatible with high performance CMOS device requirements. Further reductions in these values are achieved with use of a self-aligned PtSi/W contact barrier metallization. The contact resistance for 2.0 ..mu..m sized vias are, in this case, near 4 and 15..cap omega.. for the n/sup +/ and p/sup +/ diffusions, respectively. Sporadic leakage across shallow n/sup +//P-Tub junctions remains, however, a serious problem associated with this selective LPCVD W process. Understanding the origin of this leakage and eliminating it can lead to numerous applications of this technology in VLSI manufacturing.

  5. Summary of some current and possible future environmental problems related to geology and hydrology at Memphis, Tennessee

    USGS Publications Warehouse

    Parks, William Scott; Lounsbury, Richard W.

    1976-01-01

    This report summarizes information concerning many aspects of the geology and hydrology at Memphis, Tenn. It also outlines some of the current problems related to the local geology and hydrology or ones that may arise as a result of urbanization and industrialization of the area. The city is in the Coastal Plain physiographic province and is underlain at shallow depths by sand, clay, silt, gravel, and lignite. These post-Midway strata (Wilcox and younger) make up geologic units belonging to the uppermost Paleocene, Eocene, and Pliocene ( ) Series of the Tertiary System and to the Pleistocene and Holocene Series of the Quaternary System. Environmental problems of immediate or future concern are associated with six general topics: (1) aggregate resources, (2) foundation materials, (3) earthquake hazards, (4) flood hazards, (5) water resources, and (6) solid waste disposal. Consideration of these topics provide an overall insight into the close interrelation of the problems and the need for coordinated studies of the geology and hydrology at Memphis. (Woodard-USGS)

  6. An analytic solution to the homogeneous EIT problem on the 2D disk and its application to estimation of electrode contact impedances

    PubMed Central

    Demidenko, Eugene

    2011-01-01

    An analytic solution of the potential distribution on a 2D homogeneous disk for electrical impedance tomography under the complete electrode model is expressed via an infinite system of linear equations. For the shunt electrode model with two electrodes, our solution coincides with the previously derived solution expressed via elliptic integral (Pidcock et al 1995). The Dirichlet-to-Neumann map is derived for statistical estimation via nonlinear least squares. The solution is validated in phantom experiments and applied for breast contact impedance estimation in vivo. Statistical hypothesis testing is used to test whether the contact impedances are the same across electrodes or all equal zero. Our solution can be especially useful for a rapid real-time test for bad surface contact in clinical setting. PMID:21799240

  7. Current Health Problems.

    ERIC Educational Resources Information Center

    Gay, John; And Others

    The basic premise of this text is that, in addition to the presentation of basic cognitive and affective information, health education should go one step further by assisting student in developing decision-making skills. The text begins by offering the student a basic foundation of what is meant by health and how this meaning applies to the world,…

  8. Electrical Contacts to Nanomaterials.

    PubMed

    Bandaru, P R; Faraby, H; DiBattista, M

    2015-12-01

    The efficient passage of electrical current from an external contact to a nanomaterial is necessary for harnessing characteristics unique to the nanoscale, such as those relevant to energy quantization. However, an intrinsic resistance pertinent to dimensionality crossover and the presence of impurities precludes optimal electrical contact formation. In this review, we first discuss the relevant principles and contact resistance measurement methodologies, with modifications necessary for the nanoscale. Aspects related to the deposition of the contact material are deemed to be crucial. Consequently, the use of focused ion beam (FIB) based deposition, which relies on the ion-induced decomposition of a metallorganic precursor, and which has been frequently utilized for nanoscale contacts is considered in detail. PMID:26682353

  9. Electron transfer at the contact between Al electrode and gold nanoparticles of polymer: Nanoparticle resistive switching devices studied by alternating current impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Ouyang, Jianyong

    2013-12-01

    Electron transfer at the contact between an Al electrode and Au nanoparticles of polymer:nanoparticle devices is studied by ac impedance spectroscopy. The devices have a polystyrene layer embedded with Au nanoparticles capped with conjugated 2-naphthalenethiol sandwiched between Al and MoO3/Al electrodes, and they exhibit electrode-sensitive resistive switches. The devices in the pristine or high resistance state have high capacitance. The capacitance decreases after the devices switch to a low resistance state by a voltage scan. The change in the capacitance is attributed to the voltage-induced change on the electronic structure of the contact between the Al electrode and Au nanoparticles.

  10. Electron transfer at the contact between Al electrode and gold nanoparticles of polymer: Nanoparticle resistive switching devices studied by alternating current impedance spectroscopy

    SciTech Connect

    Ouyang, Jianyong

    2013-12-02

    Electron transfer at the contact between an Al electrode and Au nanoparticles of polymer:nanoparticle devices is studied by ac impedance spectroscopy. The devices have a polystyrene layer embedded with Au nanoparticles capped with conjugated 2-naphthalenethiol sandwiched between Al and MoO{sub 3}/Al electrodes, and they exhibit electrode-sensitive resistive switches. The devices in the pristine or high resistance state have high capacitance. The capacitance decreases after the devices switch to a low resistance state by a voltage scan. The change in the capacitance is attributed to the voltage-induced change on the electronic structure of the contact between the Al electrode and Au nanoparticles.

  11. Optimization of the front contact to minimize short-circuit current losses in CdTe thin-film solar cells

    NASA Astrophysics Data System (ADS)

    Kephart, Jason Michael

    With a growing population and rising standard of living, the world is in need of clean sources of energy at low cost in order to meet both economic and environmental needs. Solar energy is an abundant resource which is fundamentally adequate to meet all human energy needs. Photovoltaics are an attractive way to safely convert this energy to electricity with little to no noise, moving parts, water, or arable land. Currently, thin-film photovoltaic modules based on cadmium telluride are a low-cost solution with multiple GW/year commercial production, but have lower conversion efficiency than the dominant technology, crystalline silicon. Increasing the conversion efficiency of these panels through optimization of the electronic and optical structure of the cell can further lower the cost of these modules. The front contact of the CdTe thin-film solar cell is critical to device efficiency for three important reasons: it must transmit light to the CdTe absorber to be collected, it must form a reasonably passive interface and serve as a growth template for the CdTe, and it must allow electrons to be extracted from the CdTe. The current standard window layer material, cadmium sulfide, has a low bandgap of 2.4 eV which can block over 20% of available light from being converted to mobile charge carriers. Reducing the thickness of this layer or replacing it with a higher-bandgap material can provide a commensurate increase in device efficiency. When the CdS window is made thinner, a degradation in electronic quality of the device is observed with a reduction in open-circuit voltage and fill factor. One commonly used method to enable a thinner optimum CdS thickness is a high-resistance transparent (HRT) layer between the transparent conducting oxide electrode and window layer. The function of this layer has not been fully explained in the literature, and existing hypotheses center on the existence of pinholes in the window layer which are not consistent with observed results

  12. Cross-contact chain

    NASA Technical Reports Server (NTRS)

    Lieneweg, Udo (Inventor)

    1988-01-01

    A system is provided for use with wafers that include multiple integrated circuits that include two conductive layers in contact at multiple interfaces. Contact chains are formed beside the integrated circuits, each contact chain formed of the same two layers as the circuits, in the form of conductive segments alternating between the upper and lower layers and with the ends of the segments connected in series through interfaces. A current source passes a current through the series-connected segments, by way of a pair of current tabs connected to opposite ends of the series of segments. While the current flows, voltage measurements are taken between each of a plurality of pairs of voltage tabs, the two tabs of each pair connected to opposite ends of an interface that lies along the series-connected segments. A plot of interface conductances on a normal probability chart, enables prediction of the yield of good integrated circuits from the wafer.

  13. Cross-contact chain

    NASA Technical Reports Server (NTRS)

    Lieneweg, U. (Inventor)

    1986-01-01

    A system is provided for use with wafers that include multiple integrated circuits that include two conductive layers in contact at multiple interfaces. Contact chains are formed beside the integrated circuits, each contact chain formed of the same two layers as the circuits, in the form of conductive segments alternating between the upper and lower layers and with the ends of the segments connected in series through interfaces. A current source passes a current through the series-connected segments, by way of a pair of current tabs connected to opposite ends of the series of segments. While the current flows, voltage measurements are taken between each of a plurality of pairs of voltage tabs, the two tabs of each pair connected to opposite ends of an interface that lies along the series-connected segments. A plot of interface conductances on normal probability chart enables prediction of the yield of good integrated circuits from the wafer.

  14. ASME Heat Transfer Division: Proceedings. Volume 1: Heat transfer in microgravity systems, radiative heat transfer and radiative heat transfer in low-temperature environments, and thermal contact conductance and inverse problems in heat transfer; HTD-Volume 332

    SciTech Connect

    Gopinath, A.; Sadhal, S.S.; Jones, P.D.; Seyed-Yagoobi, J.; Woodbury, K.A.

    1996-12-31

    In the first section on heat transfer in microgravity, the papers cover phase-change phenomena and thermocapillary flows and surface effects. In the second section, several papers cover solution methods for radiative heat transfer while the rest cover heat transfer in low-temperature environments. The last section covers papers containing valuable information for thermal contact conductance of various materials plus papers on inverse problems in heat transfer. Separate abstracts were prepared for most papers in this volume.

  15. A QR accelerated volume-to-surface boundary condition for finite element solution of eddy current problems

    SciTech Connect

    White, D; Fasenfest, B; Rieben, R; Stowell, M

    2006-09-08

    We are concerned with the solution of time-dependent electromagnetic eddy current problems using a finite element formulation on three-dimensional unstructured meshes. We allow for multiple conducting regions, and our goal is to develop an efficient computational method that does not require a computational mesh of the air/vacuum regions. This requires a sophisticated global boundary condition specifying the total fields on the conductor boundaries. We propose a Biot-Savart law based volume-to-surface boundary condition to meet this requirement. This Biot-Savart approach is demonstrated to be very accurate. In addition, this approach can be accelerated via a low-rank QR approximation of the discretized Biot-Savart law.

  16. Implied-Consent Laws: A Review of the Literature and Examination of Current Problems and Related Statutes

    PubMed Central

    Voas, Robert B.; Kelley-Baker, Tara; Romano, Eduardo; Vishnuvajjala, Radha

    2009-01-01

    Problem A substantial proportion of drivers arrested for DUI refuse the BAC test, thereby reducing the likelihood that they will be convicted and potentially increasing the number of highrisk multiple offenders contributing to alcohol-related crashes. Method This paper reviews the information on the current status of implied-consent laws (which impose a sanction on offenders who refuse the BAC test) in the 50 states and the other relevant traffic safety laws and policies that may influenced state refusal rates. Results Although there appears to be only a weak relationship between state refusal rates and crash rates, there is strong evidence that BAC test refusals significantly compromise the arrest, prosecution, and sentencing of DUI suspects and the overall enforcement of DUI laws in the United States. Discussion Laws and policies that may reduce the number of refusals are discussed. Impact on industry Alcohol-related crash injuries are an important cost problem for U.S. industry, because of property damage from crashes, crash injuries to employees that raise health costs, or through the reduction of time on the job resulting from a highway injury. PMID:19433199

  17. EDITORIAL: Close contact Close contact

    NASA Astrophysics Data System (ADS)

    Demming, Anna

    2010-07-01

    means to produce nanoscale device elements, such as carbon nanotube transistors [5] and high-density memory crossbar circuits [6]. Recently, the use of scanning tunnelling microscopes has broached a new field of research, which is currently attracting enormous interest—single molecule detection. In issue 25 of Nanotechnology researchers in Houston reported unprecedented sensitivities using localized surface plasmon resonance shifts of gold bipyramids to detect concentrations of substances down to the single molecule level [7]. In issue 26 a collaboration of researchers from the US and Czech Republic describe a different approach, namely tunnelling recognition. In their topical review they describe hydrogen-bond mediated tunnelling and the associated experimental methods that facilitate the detection of single molecules in a tunnel junction using chemically functionalized electrodes [8]. The nanoworld depicted by scanning probe microgaphs over 20 years ago may have looked as extraterrestrial as any science fiction generated alien terrain, but though study and analysis these nano-landscapes have become significantly less alien territory. The work so far to unveil the intricacies of electronic contact has been a story of progress in investigating this new territory and manipulating the mechanisms that govern it to formulate new devices and delve deeper into phenomena at the nanoscale. References [1] Binning G, Rohrer H, Gerber Ch and Weibel E 1982 Phys. Rev. Lett. 49 57-61 [2] X D Cui, X Zarate, J Tomfohr, O F Sankey, A Primak, A L Moore, T A Moore, D Gust, G~Harris and S M Lindsay 2002 Nanotechnology 13 5-14 [3] Martin C A, van Ruitenbeek J M and van der Zant S J H 2010 Nanotechnology 21 265201 [4] Davis J J and Hanyu Y 2010 Nanotechnology 21 265302 [5] Tans S J, Verschueren A R M and Dekker C 1998 Nature 393 49-52 [6] Chen Y, Jung G-Y, Ohlberg D A A, Li X, Stewart D R, Jeppesen J O, Nielsen K A, Stoddart J F and Williams R S 2003 Nanotechnology 14 462-8 [7] Mayer K M

  18. Using the Sherman Morrison Woodbury formula for coupling external circuits with FEM for Simulation of eddy current problems

    SciTech Connect

    White, D

    2009-04-30

    Simulation of three-dimensional transient eddy current problems is important to numerous applications. The Finite Element Method (FEM) has proven be to be powerful numerical technique for solving the Partial Differential Equations (PDE) describing eddy currents. In order to solve the PDE, boundary conditions must be provided, and in many applications the boundary conditions are not known explicitly but can be provided by a Resistor-Inductor-Capacitor (RLC) circuit model. The emphasis of this paper is on an efficient and exact coupling of the RLC network equations with the FEM equations. The coupling is based on an exact linear algebra identity known as the Sherman-Morrison-Woodbury (SMW) formula. One advantage of this approach is that the FEM matrices are not modified. This is important if a fast 'black-box' solver is available for the FEM matrices, these solvers typically require that the matrices have certain mathematical properties and these properties are not modified by the SMW approach. A second advantage is that the SMW approach is valid for an arbitrary number of independent external circuits.

  19. Multigrid contact detection method

    NASA Astrophysics Data System (ADS)

    He, Kejing; Dong, Shoubin; Zhou, Zhaoyao

    2007-03-01

    Contact detection is a general problem of many physical simulations. This work presents a O(N) multigrid method for general contact detection problems (MGCD). The multigrid idea is integrated with contact detection problems. Both the time complexity and memory consumption of the MGCD are O(N) . Unlike other methods, whose efficiencies are influenced strongly by the object size distribution, the performance of MGCD is insensitive to the object size distribution. We compare the MGCD with the no binary search (NBS) method and the multilevel boxing method in three dimensions for both time complexity and memory consumption. For objects with similar size, the MGCD is as good as the NBS method, both of which outperform the multilevel boxing method regarding memory consumption. For objects with diverse size, the MGCD outperform both the NBS method and the multilevel boxing method. We use the MGCD to solve the contact detection problem for a granular simulation system based on the discrete element method. From this granular simulation, we get the density property of monosize packing and binary packing with size ratio equal to 10. The packing density for monosize particles is 0.636. For binary packing with size ratio equal to 10, when the number of small particles is 300 times as the number of big particles, the maximal packing density 0.824 is achieved.

  20. Interrelationship between long-wave current sensitivity and thermionic current of Ag-O-Cs photocathode and problems of its tolerable physical model

    NASA Astrophysics Data System (ADS)

    Rabinovich, A. I.; Pakhomov, M. T.

    1993-01-01

    Interrelation between current sensitivity at (lambda) >= 1.06 micrometers and thermoemission current (calculate data and their correlation with experimental results) is used as an indicator of choice between the donor and acceptor models of Ag-O-Cs-photocathode.

  1. [Contact allergies in musicians].

    PubMed

    Gasenzer, E R; Neugebauer, E A M

    2012-12-01

    During the last years, the problem of allergic diseases has increased. Allergies are errant immune responses to a normally harmless substance. In musicians the allergic contact dermatitis to exotic woods is a special problem. Exotic rosewood contains new flavonoids, which trigger an allergic reaction after permanent contact with the instrument. High quality woodwind instruments such as baroque flute or clarinets are made in ebony or palisander because of its great sound. Today instruments for non-professional players are also made in these exotic materials and non-professionals may have the risk to develop contact dermatitis, too. Brass-player has the risk of an allergic reaction to the different metals contained in the metal sheets of modern flutes and brass instruments. Specially nickel and brass alloys are used to product flute tubes or brass instruments. Special problem arises in children: patients who are allergic to plants or foods have a high risk to develop contact dermatitis. Parents don't know the materials of low-priced instruments for beginners. Often unknown cheap woods from exotic areas are used. Low-priced brass instruments contain high amount of brass and other cheap metals. Physicians should advice musician-patients or parents about the risks of the different materials and look for the reason of eczema on mouth, face, or hands. PMID:23233303

  2. Khat chewing, cardiovascular diseases and other internal medical problems: the current situation and directions for future research.

    PubMed

    Al-Motarreb, A; Al-Habori, M; Broadley, K J

    2010-12-01

    The leaves of khat (Catha edulis Forsk.) are chewed as a social habit for the central stimulant action of their cathinone content. This review summarizes the prevalence of the habit worldwide, the actions, uses, constituents and adverse health effects of khat chewing. There is growing concern about the health hazards of chronic khat chewing and this review concentrates on the adverse effects on health in the peripheral systems of the body, including the cardiovascular system and gastrointestinal tract. Comparisons are made with amphetamine and ecstasy in particular on the detrimental effects on the cardiovascular system. The underlying mechanisms of action of khat and its main constituent, cathinone, on the cardiovascular system are discussed. Links have been proposed between khat chewing and the incidence of myocardial infarction, dilated cardiomyopathy, vascular disease such as hypertension, cerebrovascular ischaemia and thromboembolism, diabetes, sexual dysfunction, duodenal ulcer and hepatitis. The evidence, however, is often based on limited numbers of case reports and only few prospective controlled studies have been undertaken. There is therefore an urgent need for more thorough case-control studies to be performed. This review outlines the current knowledge on the adverse health effects of khat chewing on the cardiovascular system and other internal medical problems, it assesses the evidence and the limitations of the studies and identifies the questions that future studies should address. PMID:20621179

  3. The formulation of dynamical contact problems with friction in the case of systems of rigid bodies and general discrete mechanical systems—Painlevé and Kane paradoxes revisited

    NASA Astrophysics Data System (ADS)

    Charles, Alexandre; Ballard, Patrick

    2016-08-01

    The dynamics of mechanical systems with a finite number of degrees of freedom (discrete mechanical systems) is governed by the Lagrange equation which is a second-order differential equation on a Riemannian manifold (the configuration manifold). The handling of perfect (frictionless) unilateral constraints in this framework (that of Lagrange's analytical dynamics) was undertaken by Schatzman and Moreau at the beginning of the 1980s. A mathematically sound and consistent evolution problem was obtained, paving the road for many subsequent theoretical investigations. In this general evolution problem, the only reaction force which is involved is a generalized reaction force, consistently with the virtual power philosophy of Lagrange. Surprisingly, such a general formulation was never derived in the case of frictional unilateral multibody dynamics. Instead, the paradigm of the Coulomb law applying to reaction forces in the real world is generally invoked. So far, this paradigm has only enabled to obtain a consistent evolution problem in only some very few specific examples and to suggest numerical algorithms to produce computational examples (numerical modeling). In particular, it is not clear what is the evolution problem underlying the computational examples. Moreover, some of the few specific cases in which this paradigm enables to write down a precise evolution problem are known to show paradoxes: the Painlevé paradox (indeterminacy) and the Kane paradox (increase in kinetic energy due to friction). In this paper, we follow Lagrange's philosophy and formulate the frictional unilateral multibody dynamics in terms of the generalized reaction force and not in terms of the real-world reaction force. A general evolution problem that governs the dynamics is obtained for the first time. We prove that all the solutions are dissipative; that is, this new formulation is free of Kane paradox. We also prove that some indeterminacy of the Painlevé paradox is fixed in this

  4. Effects of School-Wide Positive Behavioral Interventions and Supports on Internalizing Problems: Current Evidence and Future Directions

    ERIC Educational Resources Information Center

    McIntosh, Kent; Ty, Sophie V.; Miller, Lynn D.

    2014-01-01

    School-Wide Positive Behavioral Interventions and Supports (SWPBIS) has a large evidence base for preventing and addressing externalizing problem behavior, but there is little research examining its effects on internalizing problems, such as anxiety and depression. Given the prevalence of internalizing problems in today's children and youth,…

  5. Prioritized Contact Transport Stream

    NASA Technical Reports Server (NTRS)

    Hunt, Walter Lee, Jr. (Inventor)

    2015-01-01

    A detection process, contact recognition process, classification process, and identification process are applied to raw sensor data to produce an identified contact record set containing one or more identified contact records. A prioritization process is applied to the identified contact record set to assign a contact priority to each contact record in the identified contact record set. Data are removed from the contact records in the identified contact record set based on the contact priorities assigned to those contact records. A first contact stream is produced from the resulting contact records. The first contact stream is streamed in a contact transport stream. The contact transport stream may include and stream additional contact streams. The contact transport stream may be varied dynamically over time based on parameters such as available bandwidth, contact priority, presence/absence of contacts, system state, and configuration parameters.

  6. Types of Contact Lenses

    MedlinePlus

    ... Consumer Devices Consumer Products Contact Lenses Types of Contact Lenses Share Tweet Linkedin Pin it More sharing ... Orthokeratology (Ortho-K) Decorative (Plano) Contact Lenses Soft Contact Lenses Soft contact lenses are made of soft, ...

  7. Study of effects of uncertainties of comet and asteroid encounter and contact guidance requirements. Part 2: Tumbling problem studies. [development of navigation and guidance techniques for space rendezvous

    NASA Technical Reports Server (NTRS)

    Cochran, J. E., Jr.

    1974-01-01

    The problem of determining the rotational motion of a tumbling celestial body of the asteroid type using spacecraft-acquired data is addressed. The rotational motion of the body is modeled by free-Eulerian motion of a triaxial, rigid body and its translational motion with respect, to a nonrotating, observing spacecraft, which is not thrusting, is assumed to be uniform during the time observations are made. The mathematical details which form the basis for a digital simulation of the motion and observations are presented. Two algorithms for determining the motion from observations for the special case of uniform rotational motion are given.

  8. Protein folding using contact maps.

    PubMed

    Vendruscolo, M; Domany, E

    2000-01-01

    We discuss the problem of representations of protein structure and give the definition of contact maps. We present a method to obtain a three-dimensional polypeptide conformation from a contact map. We also explain how to deal with the case of nonphysical contact maps. We describe a stochastic method to perform dynamics in contact map space. We explain how the motion is restricted to physical regions of the space. First, we introduce the exact free energy of a contact map and discuss two simple approximations to it. Second, we present a method to derive energy parameters based on perception learning. We prove in an extensive number of situations that the pairwise contact approximation both when alone and when supplemented with a hydrophobic term is unsuitable for stabilizing proteins' native states. PMID:10668399

  9. JKR adhesion in cylindrical contacts

    NASA Astrophysics Data System (ADS)

    Sundaram, Narayan; Farris, T. N.; Chandrasekar, S.

    2012-01-01

    Planar JKR adhesive solutions use the half-plane assumption and do not permit calculation of indenter approach or visualization of adhesive force-displacement curves unless the contact is periodic. By considering a conforming cylindrical contact and using an arc crack analogy, we obtain closed-form indenter approach and load-contact size relations for a planar adhesive problem. The contact pressure distribution is also obtained in closed-form. The solutions reduce to known cases in both the adhesion-free and small-contact solution ( Barquins, 1988) limits. The cylindrical system shows two distinct regimes of adhesive behavior; in particular, contact sizes exceeding the critical (maximum) size seen in adhesionless contacts are possible. The effects of contact confinement on adhesive behavior are investigated. Some special cases are considered, including contact with an initial neat-fit and the detachment of a rubbery cylinder from a rigid cradle. A comparison of the cylindrical solution with the half-plane adhesive solution is carried out, and it indicates that the latter typically underestimates the adherence force. The cylindrical adhesive system is novel in that it possesses stable contact states that may not be attained even on applying an infinite load in the absence of adhesion.

  10. Advances in contact algorithms and their application to tires

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K.; Tanner, John A.

    1988-01-01

    Currently used techniques for tire contact analysis are reviewed. Discussion focuses on the different techniques used in modeling frictional forces and the treatment of contact conditions. A status report is presented on a new computational strategy for the modeling and analysis of tires, including the solution of the contact problem. The key elements of the proposed strategy are: (1) use of semianalytic mixed finite elements in which the shell variables are represented by Fourier series in the circumferential direction and piecewise polynomials in the meridional direction; (2) use of perturbed Lagrangian formulation for the determination of the contact area and pressure; and (3) application of multilevel iterative procedures and reduction techniques to generate the response of the tire. Numerical results are presented to demonstrate the effectiveness of a proposed procedure for generating the tire response associated with different Fourier harmonics.

  11. GIREP Conference in Israel: Oscillations and Waves and Current Problems in Physics Teaching (Weizmann Institute of Science, Rehovot, Israel, 19-24 August 1979).

    ERIC Educational Resources Information Center

    Mikelskis, Helmut

    1980-01-01

    Discusses oscillations and waves as a new topic for primary and secondary science curricula because of the many developments in the fields of optics and electronics. Outlines current problems in physics instruction under the headings of social aspects, disadvantaged pupils, and developing countries. (GS)

  12. Contact: Releasing the news

    NASA Astrophysics Data System (ADS)

    Pinotti, Roberto

    The problem of mass behavior after man's future contacts with other intelligences in the universe is not only a challenge for social scientists and political leaders all over the world, but also a cultural time bomb as well. In fact, since the impact of CETI (Contact with Extraterrestrial Intelligence) on human civilization, with its different cultures, might cause a serious socio-anthropological shock, a common and predetermined worldwide strategy is necessary in releasing the news after the contact, in order to keep possible manifestations of fear, panic and hysteria under control. An analysis of past studies in this field and of parallel historical situations as analogs suggests a definite "authority crisis" in the public as a direct consequence of an unexpected release of the news, involving a devastating "chain reaction" process (from both the psychological and sociological viewpoints) of anomie and maybe the collapse of today's society. The only way to prevent all this is to prepare the world's public opinion concerning contact before releasing the news, and to develop a long-term strategy through the combined efforts of scientists, political leaders, intelligence agencies and the mass media, in order to create the cultural conditions in which a confrontation with ETI won't affect mankind in a traumatic way. Definite roles and tasks in this multi-level model are suggested.

  13. High-energy/high-rate powder consolidation of binderless copper-graphite composites for high-speed, high-current sliding-contact applications

    SciTech Connect

    Wang, M.J.

    1988-01-01

    A novel processing approach was developed to consolidate binderless copper-graphite powder composites. This high-energy/high-rate (HEHR) consolidation process employed a 10-MJ homopolar generator (HPG) as a pulsed power source. The discharge of such a current pulse through the powder mixture under pressure produced a denser product with improved mechanical and electrical properties compared to the conventionally sintered commercial material which was manufactured from the same starting powders. Effect of process parameters including electrode material, discharge rpm, and compacting pressure on compact properties was studied via keeping the material variables fixed. Investigation of the process kinetics and mechanism were carried out through the computer simulation of heat transfer during the discharge and the analysis of processing data. Based on the theoretical relationship between the compact resistance and the compact density obtained from the mathematical derivation, the role of process parameter was revealed and the main densification mechanism for the binderless copper-graphite system was determined to be plastic flow.

  14. Underrepresentation of Culturally Different Students in Gifted Education: Reflections about Current Problems and Recommendations for the Future

    ERIC Educational Resources Information Center

    Ford, Donna Y.

    2010-01-01

    For almost two decades, the author has devoted her professional life to the field of gifted education, as have others. More than any time in her career, she finds herself reflecting even more so on the persistent or stubborn problem of underrepresentation among Black and Hispanic students in gifted education. Is this more frequent self-reflection…

  15. Room temperature spin injection into (110) GaAs quantum wells using Fe/x-AlO{sub x} contacts in the regime of current density comparable to laser oscillation

    SciTech Connect

    Yokota, Nobuhide Aoshima, Yohei; Ikeda, Kazuhiro; Kawaguchi, Hitoshi; Nishizawa, Nozomi; Munekata, Hiro

    2015-10-28

    We investigate the electrical spin injection into (110) GaAs single quantum wells (SQWs) and multiple quantum wells (MQWs) using light-emitting diodes (LEDs) having Fe/crystalline-AlO{sub x} (x-AlO{sub x}) tunnel barrier contacts. A degree of circular polarization (P{sub c}) of 5.0% is obtained for the SQW LED at 4 K with the current density of 1 kA/cm{sup 2} which is comparable to that for the laser oscillation in vertical-cavity surface-emitting lasers (VCSELs). On the basis of electron spin relaxation time and carrier lifetime in the (110) GaAs SQW measured by time-dependent photoluminescence and the value of P{sub c} = 5.0%, the degree of spin polarization of initially injected electrons (P{sub 0}) in the SQW is estimated to be 6.6% at 4 K. By using the MQW LED having a much stronger electroluminescence, a P{sub c} value of 2.6% is obtained at room temperature (RT) with the current density of 1.5 kA/cm{sup 2}. The temperature and current density dependences of P{sub c} are found to be weak in both the SQW and MQW LEDs. The estimated P{sub 0} of 9.3% at RT suggests that the Fe/x-AlO{sub x} contacts can be used for the RT electrical spin injection for spin-controlled VCSELs.

  16. On the ohmicity of Schottky contacts

    NASA Astrophysics Data System (ADS)

    Sachenko, A. V.; Belyaev, A. E.; Konakova, R. V.

    2016-06-01

    An analysis is made of the conditions for ohmic contacts realization in the case of Schottky contacts. Based on the classical notions about the mechanisms of current flow, we consider the generalized model of Schottky contact that takes into account the thermionic current of majority charge carriers and recombination current of minority charge carriers in Schottky contacts with a dielectric gap. An analysis of the results given by that model made it possible to obtain ohmicity criteria for Schottky contacts and compare the conditions for low injection level and ohmicity of Schottky contacts in the case of silicon-based contacts. It is shown that conditions for Schottky contact ohmicity do not coincide with those for p-n junctions.

  17. [Current situation, problem analyses and its countermeasure of formulae of traditional Chinese medicine (FTCM) preventing and curing tumor angiogenesis].

    PubMed

    Xi, Shengyan; Wang, Yanhui; Zhao, Yufang; Lu, Dawei; Li, Pengcheng; Zhang, Qian

    2010-05-01

    Malignant tumor is the common disease that threaten severely to people's health. Formulae of traditional Chinese medicine (FTCM), as the major component of traditional drugs, has played more important role on the prevention and cure to tumor. The Folkman's theory that tumorous growth depends on tumor neovascularization has been confirmed so many years, so to inhibit the tumor angiogenesis, is an important path to treat tumor. The research of FTCM to antagonizing tumor angiogenesis in our country has been started more lately. Since it has been reported some FTCMs can inhibit angiogenesis, and it also exists many problems. The article summarized the correlated research of FTCM to antagonize tumor angiogenesis for the past several years, and according this, analyzed, stated and commented to the problems, countermeasures, development and direction of PTCM to antagonize tumor angiogenesis. PMID:20707214

  18. Resistance of Candida species to antifungal agents used in the treatment of onychomycosis: a review of current problems.

    PubMed

    Evans, E G

    1999-11-01

    Treatment of Candida infections with fluconazole has resulted in the emergence of drug resistance, a problem particularly apparent in HIV-infected patients. Frequently, the yeast is also cross-resistant to itraconazole and other azoles. In neutropenic patients fluconazole therapy or prophylaxis has caused overgrowth and infection by inherently less susceptible species of Candida, principally C. glabrata and C. krusei. Consequently, the use of intermittent long-term azole therapy to treat onychomycosis could result in changes in the commensal yeast flora of patients--either resistance or pathogen shift. An 'off-study' investigation undertaken in patients receiving either continuous terbinafine or intermittent itraconazole for toenail onychomycosis (L.I.ON. study) showed no evidence of changes in the yeast species present, nor in their sensitivity to itraconazole or fluconazole. Although intermittent itraconazole seems unlikely to cause problems in this respect, the situation with regard to intermittent fluconazole therapy of onychomycosis needs further study. PMID:10730912

  19. A Socio-Cultural Reframing of Science and Dis/ability in Education: Past Problems, Current Concerns, and Future Possibilities

    ERIC Educational Resources Information Center

    Connor, David J.; Valle, Jan W.

    2015-01-01

    In this article we assert the value of a socio-cultural reframing of science and dis/ability in education. We begin by problematizing current issues in education pertaining to the often-unquestioned concept of dis/ability and the impact that has upon research, theory, practice, and policy. As our topic is broad, we have chosen to focus upon four…

  20. Implicit Multibody Penalty-BasedDistributed Contact.

    PubMed

    Xu, Hongyi; Zhao, Yili; Barbic, Jernej

    2014-09-01

    The penalty method is a simple and popular approach to resolving contact in computer graphics and robotics. Penalty-based contact, however, suffers from stability problems due to the highly variable and unpredictable net stiffness, and this is particularly pronounced in simulations with time-varying distributed geometrically complex contact. We employ semi-implicit integration, exact analytical contact gradients, symbolic Gaussian elimination and a SVD solver to simulate stable penalty-based frictional contact with large, time-varying contact areas, involving many rigid objects and articulated rigid objects in complex conforming contact and self-contact. We also derive implicit proportional-derivative control forces for real-time control of articulated structures with loops. We present challenging contact scenarios such as screwing a hexbolt into a hole, bowls stacked in perfectly conforming configurations, and manipulating many objects using actively controlled articulated mechanisms in real time. PMID:26357376

  1. Contact Graph Routing

    NASA Technical Reports Server (NTRS)

    Burleigh, Scott C.

    2011-01-01

    Contact Graph Routing (CGR) is a dynamic routing system that computes routes through a time-varying topology of scheduled communication contacts in a network based on the DTN (Delay-Tolerant Networking) architecture. It is designed to enable dynamic selection of data transmission routes in a space network based on DTN. This dynamic responsiveness in route computation should be significantly more effective and less expensive than static routing, increasing total data return while at the same time reducing mission operations cost and risk. The basic strategy of CGR is to take advantage of the fact that, since flight mission communication operations are planned in detail, the communication routes between any pair of bundle agents in a population of nodes that have all been informed of one another's plans can be inferred from those plans rather than discovered via dialogue (which is impractical over long one-way-light-time space links). Messages that convey this planning information are used to construct contact graphs (time-varying models of network connectivity) from which CGR automatically computes efficient routes for bundles. Automatic route selection increases the flexibility and resilience of the space network, simplifying cross-support and reducing mission management costs. Note that there are no routing tables in Contact Graph Routing. The best route for a bundle destined for a given node may routinely be different from the best route for a different bundle destined for the same node, depending on bundle priority, bundle expiration time, and changes in the current lengths of transmission queues for neighboring nodes; routes must be computed individually for each bundle, from the Bundle Protocol agent's current network connectivity model for the bundle s destination node (the contact graph). Clearly this places a premium on optimizing the implementation of the route computation algorithm. The scalability of CGR to very large networks remains a research topic

  2. Contact Zones, Problem Posing and Critical Consciousness

    ERIC Educational Resources Information Center

    Patel, Lisa

    2012-01-01

    In this article, I share the shape and findings of a participatory action research project with newcomer youths on the contours of status in society. This project was nested in a professional internship experience for newcomer youth, and this experience provided the context in which we explored how privilege and status are afforded in American…

  3. Various contact approaches for the finite cell method

    NASA Astrophysics Data System (ADS)

    Konyukhov, Alexander; Lorenz, Christian; Schweizerhof, Karl

    2015-08-01

    The finite cell method (FCM) provides a method for the computation of structures which can be described as a mixture of high-order FEM and a special integration technique. The method is one of the novel computational methods and is highly developed within the last decade. One of the major problems of FCM is the description of boundary conditions inside cells as well as in sub-cells. And a completely open problem is the description of contact. Therefore, the motivation of the current work is to develop a set of computational contact mechanics approaches which will be effective for the finite element cell method. Thus, for the FCM method we are developing and testing hereby focusing on the Hertz problem the following algorithms: direct integration in the cell method, allowing the fastest implementation, but suffering from numerical artifacts such as the "stamp effect"; the most efficient scheme concerning approximation properties the cell-surface-to-analytical-surface contact element designed for contact with rigid bodies leading to cell-wisely contact elements; and finally the discrete-cell-to-cell contact approach based on the finite discrete method. All developed methods are carefully verified with the analytical Hertz solution. The cell subdivisions, the order of the shape functions as well as the selection of the classes for shape functions are investigated for all developed contact approaches. This analysis allows to choose the most robust approach depending on the needs of the user such as correct representation of the stresses, or only satisfaction of geometrical non-penetration conditions.

  4. [Still a small problem with the mad cow disease? Creutzfeldt-Jakob disease and other prion diseases: current status].

    PubMed

    Lundberg, P O

    2001-01-10

    This review is based on recent published research on the BSE/CJD/vCJD problem mainly from UK, Germany and France. The situation in Sweden seems to be fortunate for several reasons. The use of meat and bonemeal as animal fodder was forbidden in this country 13 years ago. Sweden has not had any sheep with scrapie for many years. No animals with BSE have so far been found in our country. The incidence of sporadic CJD in this country followed retrospectively from 1985 to 1996 and prospectively from 1997 to 1999 has been around 1.2 per million per year with no significant increase. Only few cases of familial CJD are known. No patient with iatrogenic CJD has ever been found. The use of growth hormone derived from human pituitary glands was abandoned in 1985 when recombinant human growth hormone became available. So far there is no indication that any of the CJD cases diagnosed in Sweden has been of the vCJD type, the one linked to BSE. However, as the incubation period for prion diseases is very long and the Swedes are frequent travellers there is a risk that people from our country could have contracted vCJD through consuming meat products in countries with BSE. As a precaution the consumption of brain, spinal cord, lymphatic tissue, lungs, and gastrointestinal tract should be avoided. Human pituitary derived growth hormone is still available in some countries and might be illegally imported into Sweden. PMID:11213704

  5. Current state, problems, and prospects of development of the fuel and power industry of the Russian Federation

    SciTech Connect

    Shatalov, A.T.

    1994-09-01

    Despite the political and territorial changes that have occurred in the former USSR, the Russian Federation as before remains the core of the entire energy supply system of countries of the Commonwealth of Independent States (CIS), the three Baltic States, as well as an exporter of oil and gas to European countries. Demonstrated gas reserves in Russia amount to 47 trillion cubic meters and coal reserves more than 200 billion tons. With the dissolution of the USSR, the infrastructure of the entire region was affected. The main production of pipes remained in Ukraine and 80% of the production of oil equipment remained in Azerbaijan. The majority of underground gas storage facilities, refineries, and electric-power installations constructed during the past 20 years remained in Belarus, Baltic Countries, and Ukraine. To solve some of the problems, laws were passed that aimed at the formation of market relations in the economy and power industry. The transition to a market economy in the oil and gas industry should take 5-7 years and has a large effect on the overall markets reforms taking place. The article also outlines the history and present state of petroleum reserves and development in Russia.

  6. A socio-cultural reframing of science and dis/ability in education: past problems, current concerns, and future possibilities

    NASA Astrophysics Data System (ADS)

    Connor, David J.; Valle, Jan W.

    2015-12-01

    In this article we assert the value of a socio-cultural reframing of science and dis/ability in education. We begin by problematizing current issues in education pertaining to the often-unquestioned concept of dis/ability and the impact that has upon research, theory, practice, and policy. As our topic is broad, we have chosen to focus upon four interconnected areas: (1) the historical mistrust of science and pseudo-science by people with dis/abilities; (2) the pervasive use of pseudo-science within the contemporary field of special education; (3) the use of dis/ability studies in education (DSE) to provide a contrast between a traditional positivist framing and a socio-cultural framing of dis/ability, and; (4) a brief exploration of what a DSE/socio-cultural grounding looks like for both schools and classroom teachers. In sum, our intention is to engage science educators to reject deficit-notions of dis/ability in favor of understanding it as part of human variation, and consider the personal and professional benefits of this shift.

  7. Field of researches and applications domains for compact and large-scale DPF devices: Current assets, problems and essentials

    NASA Astrophysics Data System (ADS)

    Gribkov, V. A.

    2014-08-01

    Examination of the most important processes taking place in Dense Plasma Focus (DPF) device that lead to the production of very bright flashes of neutrons and X-rays is presented. It is shown that the current abruption (CA) phenomenon accompanied by the plasma-diode formation plays the key role in these events. Issues of matching of different primary loads with plasma inductive storage and subsequently with plasma diode are discussed. It is shown that at the intermediate energies it is possible to attain the perfect matching. Results in some applications of medium-sized DPF obtained recently in radiation material science, dynamic quality control, biology and medicine are presented. It is shown that for better matching at very high energies the classical intermediate energy compressing element can be used. Besides schemes with laser support switching are discussed. Extrapolations of DPF phenomena to very high and very low energies with their feasibility are examined. Envisioned applications of such huge and tiny DPF devices in power production, medicine and electronics are discussed.

  8. Protein Residue Contacts and Prediction Methods

    PubMed Central

    Adhikari, Badri

    2016-01-01

    In the field of computational structural proteomics, contact predictions have shown new prospects of solving the longstanding problem of ab initio protein structure prediction. In the last few years, application of deep learning algorithms and availability of large protein sequence databases, combined with improvement in methods that derive contacts from multiple sequence alignments, have shown a huge increase in the precision of contact prediction. In addition, these predicted contacts have also been used to build three-dimensional models from scratch. In this chapter, we briefly discuss many elements of protein residue–residue contacts and the methods available for prediction, focusing on a state-of-the-art contact prediction tool, DNcon. Illustrating with a case study, we describe how DNcon can be used to make ab initio contact predictions for a given protein sequence and discuss how the predicted contacts may be analyzed and evaluated. PMID:27115648

  9. Protein Residue Contacts and Prediction Methods.

    PubMed

    Adhikari, Badri; Cheng, Jianlin

    2016-01-01

    In the field of computational structural proteomics, contact predictions have shown new prospects of solving the longstanding problem of ab initio protein structure prediction. In the last few years, application of deep learning algorithms and availability of large protein sequence databases, combined with improvement in methods that derive contacts from multiple sequence alignments, have shown a huge increase in the precision of contact prediction. In addition, these predicted contacts have also been used to build three-dimensional models from scratch.In this chapter, we briefly discuss many elements of protein residue-residue contacts and the methods available for prediction, focusing on a state-of-the-art contact prediction tool, DNcon. Illustrating with a case study, we describe how DNcon can be used to make ab initio contact predictions for a given protein sequence and discuss how the predicted contacts may be analyzed and evaluated. PMID:27115648

  10. Irritant Contact Dermatitis

    MedlinePlus

    ... and rashes clinical tools newsletter | contact Share | Irritant Contact Dermatitis Information for adults A A A This ... severe involvement in the patient's armpit. Overview Irritant contact dermatitis is an inflammatory rash caused by direct ...

  11. Contact Lens Risks

    MedlinePlus

    ... Health and Consumer Devices Consumer Products Contact Lenses Contact Lens Risks Share Tweet Linkedin Pin it More ... redness blurred vision swelling pain Serious Hazards of Contact Lenses Symptoms of eye irritation can indicate a ...

  12. Contact Lens Care

    MedlinePlus

    ... For Consumers Consumer Information by Audience For Women Contact Lens Care Share Tweet Linkedin Pin it More ... 1088, www.fda.gov/medwatch Learn More about Contact Lens Care Other Tips on Contact Lenses Decorative ...

  13. Contact Lens Solution Toxicity

    MedlinePlus

    ... rash and rashes clinical tools newsletter | contact Share | Contact Lens Solution Toxicity Information for adults A A A This image shows a reaction to contact lens solution. The prominent blood vessels and redness ...

  14. Non-contact ECG monitoring

    NASA Astrophysics Data System (ADS)

    Smirnov, Alexey S.; Erlikh, Vadim V.; Kodkin, Vladimir L.; Keller, Andrei V.; Epishev, Vitaly V.

    2016-03-01

    The research is dedicated to non-contact methods of electrocardiography. The authors describe the routine of experimental procedure and suggest the approach to solving the problems which arise at indirect signal recording. The paper presents the results of experiments conducted by the authors, covers the flow charts of ECG recorders and reviews the drawbacks of filtering methods used in foreign equivalents.

  15. Contact charge electrophoresis: experiment and theory.

    PubMed

    Drews, Aaron M; Cartier, Charles A; Bishop, Kyle J M

    2015-04-01

    Contact charge electrophoresis (CCEP) uses steady electric fields to drive the continuous, oscillatory motion of conductive particles and droplets between two or more electrodes. These rapid oscillations can be rectified to direct the motion of objects within microfluidic environments using low-power, dc voltage. Here, we compare high precision experimental measurements of CCEP within a microfluidic system to equally detailed theoretical predictions on the motion of a conductive particle between parallel electrodes. We use a simple, capillary microfluidic platform that combines high-speed imaging with precision electrical measurements to enable the synchronized acquisition of both the particle location and the electric current due to particle motion. The experimental results are compared to those of a theoretical model, which relies on a Stokesian dynamics approach to accurately describe both the electrostatic and hydrodynamic problems governing particle motion. We find remarkable agreement between theory and experiment, suggesting that particle motion can be accurately captured by a combination of classical electrostatics and low-Reynolds number hydrodynamics. Building on this agreement, we offer new insight into the charge transfer process that occurs when the particle nears contact with an electrode surface. In particular, we find that the particle does not make mechanical contact with the electrode but rather that charge transfer occurs at finite surface separations of >0.1 μm by means of an electric discharge through a thin lubricating film. We discuss the implications of these findings on the charging of the particle and its subsequent dynamics. PMID:25785396

  16. Contact potential measurement: The preamplifier

    NASA Astrophysics Data System (ADS)

    Rossi, Frank

    1992-07-01

    The factors governing the choice of preamplifier type for the vibrating capacitive probe used in contact potential measurements are examined. Two types are compared: a high input impedance voltage amplifier and a current amplifier. The latter has been increasingly used in recent years due to its great advantages in dealing with parasitic input capacitance. We extend previous analyses, elucidating other advantages of the current amplifier. Particularly important are (i) the reduction of spurious microphonic signals, implying lower systematic error, and (ii) the white noise spectrum of its equivalent contact potential noise, which allows random error to be effectively reduced by increased averaging periods.

  17. Finite Element Analysis of 2-D Elastic Contacts Involving FGMs

    NASA Astrophysics Data System (ADS)

    Abhilash, M. N.; Murthy, H.

    2014-05-01

    The response of elastic indenters in contact with Functionally Graded Material (FGM) coated homogeneous elastic half space has been presented in the current paper. Finite element analysis has been used due to its ability to handle complex geometry, material, and boundary conditions. Indenters of different typical surface profiles have been considered and the problem has been idealized as a two-dimensional (2D) plane strain problem considering only normal loads. Initially, indenters were considered to be rigid and the results were validated with the solutions presented in the literature. The analysis has then been extended to the case of elastic indenters on FGM-coated half spaces and the results are discussed.

  18. [Fungal contamination of hydrophilic contact lenses (author's transl)].

    PubMed

    Liotet, S; Warnet, V N

    1981-01-01

    A study was conducted on 113 contact lens showing fungal colonies. The main genus isolated was Cepohalosporium (59.4 p. cent). Lens contamination is favoured by a major factor: contact lens spoliation, a secondary factor being inadequate contact lens maintenance. This contamination raises an economic problem, as every affected contact lens must be replaced. PMID:7199063

  19. Contact urticaria from rice.

    PubMed

    Yamakawa, Y; Ohsuna, H; Aihara, M; Tsubaki, K; Ikezawa, Z

    2001-02-01

    A 30-year-old man with atopic dermatitis had had erythema and itching of the hands after washing rice in water, though he had always eaten cooked rice without problems. Handling test with water used to wash regular rice was performed on abraded hands, and produced urticarial erythema after several minutes. Applications of water used to wash allergen-reduced rice were negative for urticarial reaction. Prick test with water used to wash regular rice was +++. However prick test reaction with water used to wash allergen-reduced rice was +. Histamine-release test of regular rice-washing water was grade 3 and that of allergen-reduced rice grade 1. In immunoblotting analysis with regular rice washing water, there were no bands with this patient. These results suggest that the allergen responsible for contact urticaria in this patient might be water-soluble, heat-unstable, and not contained in allergen-reduced rice. PMID:11205411

  20. [Current problems in hospital infection].

    PubMed

    Popkirov, S; Fitschev, G

    1980-01-01

    (1) In surgical infections staphylococci are still dominating. (2) Following nosocomial infections gramnegative pathogens become more and more important. (3) Systemic administration of antibiotics favour the selection of gramnegative bacteria and the increase of resistence. (4) Antibiotics do not substitute asepsis and antisepsis. (5) The systemic administration of antibiotics in surgical infections should be clearly reduced. (6) No prophylactic use of antibiotics in surgery to prevent wounds infections. PMID:6774512

  1. Current Titles

    SciTech Connect

    Various

    2006-06-01

    This booklet is published for those interested in current research being conducted at the National Center for Electron Microscopy. The NCEM is a DOE-designated national user facility and is available at no charge to qualified researchers. Access is controlled by an external steering committee. Interested researchers may contact Jane Cavlina, Administrator, at 510/486-6036.

  2. Pose and motion from contact

    SciTech Connect

    Jia, Y.B.; Erdmann, M.

    1999-05-01

    In the absence of vision, grasping an object often relies on tactile feedback from the fingertips. As the finger pushes the object, the fingertip can feel the contact point move. If the object is known in advance, from this motion the finger may infer the location of the contact point on the object, and thereby, the object pose. This paper primarily investigates the problem of determining the pose (orientation and position) and motion (velocity and angular velocity) of a planar object with known geometry from such contact motion generated by pushing. A dynamic analysis of pushing yields a nonlinear system that relates through contact the object pose and motion to the finger motion. The contact motion on the fingertip thus encodes certain information about the object pose. Nonlinear observability theory is employed to show that such information is sufficient for the finger to observe not only the pose, but also the motion of the object. Therefore, a sensing strategy can be realized as an observer of the nonlinear dynamic system. Two observers are subsequently introduced. The first observer, based on the work of Gautheir, Hammouri, and Othman (1992), has its gain determined by the solution of a Lyapunov-like equation; it can be activated at any time instant during a push. The second observer, based on Newton`s method, solves for the initial (motionless) object pose from three intermediate contact points during a push. Under the Coulomb-friction model, the paper deals with support friction in the plane and/or contact friction between the finger and the object. Extensive simulations have been done to demonstrate the feasibility of the two observers. Preliminary experiments (with an Adept robot) have also been conducted. A contact sensor has been implemented using strain gauges.

  3. On the structure of contact binaries. I - The contact discontinuity

    NASA Technical Reports Server (NTRS)

    Shu, F. H.; Lubow, S. H.; Anderson, L.

    1976-01-01

    The problem of the interior structure of contact binaries is reviewed, and a simple resolution of the difficulties which plague the theory is suggested. It is proposed that contact binaries contain a contact discontinuity between the lower surface of the common envelope and the Roche lobe of the cooler star. This discontinuity is maintained against thermal diffusion by fluid flow, and the transition layer is thin to the extent that the dynamical time scale is short in comparison with the thermal time scale. The idealization that the transition layer has infinitesimal thickness allows a simple formulation of the structure equations which are closed by appropriate jump conditions across the discontinuity. The further imposition of the standard boundary conditions suffices to define a unique model for the system once the chemical composition, the masses of the two stars, and the orbital separation are specified.

  4. Electrical contact resistance degradation of a hot-switched simulated metal MEMS contact.

    SciTech Connect

    Dugger, Michael Thomas; Dickrell, Daniel John, III

    2005-03-01

    Electrical contact resistance testing was performed by hot-switching a simulated gold-platinum metal microelectromechanical systems contact. The experimental objective was to determine the sensitivity of the contact resistance degradation to current level and environment. The contact resistance increased sharply after 100 hot-switched cycles in air. Hot-switching at a reduced current and in nitrogen atmosphere curtailed contact resistance degradation by several orders of magnitude. The mechanism responsible for the resistance degradation was found to be arc-induced decomposition of adsorbed surface contaminants.

  5. A survey of wheel-rail contact models for rail vehicles

    NASA Astrophysics Data System (ADS)

    Meymand, Sajjad Z.; Keylin, Alexander; Ahmadian, Mehdi

    2016-03-01

    Accurate and efficient contact models for wheel-rail interaction are essential for the study of the dynamic behaviour of a railway vehicle. Assessment of the contact forces and moments, as well as contact geometry provide a fundamental foundation for such tasks as design of braking and traction control systems, prediction of wheel and rail wear, and evaluation of ride safety and comfort. This paper discusses the evolution and the current state of the theories for solving the wheel-rail contact problem for rolling stock. The well-known theories for modelling both normal contact (Hertzian and non-Hertzian) and tangential contact (Kalker's linear theory, FASTSIM, CONTACT, Polach's theory, etc.) are reviewed. The paper discusses the simplifying assumptions for developing these models and compares their functionality. The experimental studies for evaluation of contact models are also reviewed. This paper concludes with discussing open areas in contact mechanics that require further research for developing better models to represent the wheel-rail interaction.

  6. Discrete-contact nanowire photovoltaics

    NASA Astrophysics Data System (ADS)

    Chitambar, Michelle J.; Wen, Wen; Maldonado, Stephen

    2013-11-01

    A series of finite-element simulations have been performed to assess the operational characteristics of a new semiconductor nanowire solar cell design operating under high-level injection conditions. Specifically, the steady-state current-voltage behavior of a cylindrical silicon (Si) nanowire with a series of discrete, ohmic-selective contacts under intense sunlight illumination was investigated. The scope of the analysis was limited to only the factors that impact the net internal quantum yield for solar to electricity conversion. No evaluations were performed with regards to optical light trapping in the modeled structures. Several aspects in a discrete-contact nanowire device that could impact operation were explored, including the size and density of ohmic-selective contacts, the size of the nanowire, the electronic quality and conductivity of the nanowire, the surface defect density of the nanowire, and the type of ohmic selectivity employed at each contact. The analysis showed that there were ranges of values for each parameter that supported good to excellent photoresponses, with certain combinations of experimentally attainable material properties yielding internal energy conversion efficiencies at the thermodynamic limit for a single junction cell. The merits of the discrete-contact nanowire cell were contrasted with "conventional" nanowire photovoltaic cells featuring a uniform conformal contact and also with planar point-contact solar cells. The unique capacity of the discrete-contact nanowire solar cell design to operate at useful energy conversion efficiencies with low quality semiconductor nanowires (i.e., possessing short charge-carrier lifetimes) with only light doping is discussed. This work thus defines the impetus for future experimental work aimed at developing this photovoltaic architecture.

  7. Formula Gives Better Contact-Resistance Values

    NASA Technical Reports Server (NTRS)

    Lieneweg, Udo; Hannaman, David J.

    1988-01-01

    Lateral currents in contact strips taken into account. Four-terminal test structures added to intergrated circuits to enable measurement of interfacial resistivities of contacts between thin conducting layers. Thin-film model simplified quasi-two-dimensional potential model that accounts adequately for complicated three-dimensional, nonuniform current densitites. Effects of nonuniformity caused by lateral current flow in strips summarized in equivalent resistance Rs and voltage Vs.

  8. Early contacts between T lymphocytes and activating surfaces

    NASA Astrophysics Data System (ADS)

    Cretel, E.; Touchard, D.; Benoliel, A. M.; Bongrand, P.; Pierres, A.

    2010-05-01

    Cells continually probe their environment to adapt their behaviour. A current challenge is to determine how they analyse nearby surfaces and how they process information to take decisions. We addressed this problem by monitoring human T lymphocyte attachment to surfaces coated with activating anti-CD3 or control anti-HLA antibodies. Interference reflection microscopy allowed us to monitor cell-to-surface apposition with a few nanometre vertical resolution during the first minutes following contact. We found that (i) when a cell fell on a surface, contact extension was preceded by a lag of several tens of seconds. (ii) During this lag, vertical membrane undulations seemed to generate transient contacts with underlying surfaces. (iii) After the lag period, the contact area started increasing linearly with a rate of about 1.5 µm2 s - 1 on activating surfaces and about 0.2 µm2 s - 1 on control surfaces. (iv) Concomitantly with lateral surface extension, the apparent distance between cell membranes and surfaces steadily decreased. These results are consistent with the hypothesis that the cell decision to spread rapidly on activating surfaces resulted from the integration of information yielded by transient contacts with these surfaces generated by membrane undulations during a period of about 1 min.

  9. Using Mathematical Methods to Compensate for Problems Resulting from Differences in Material Properties for Remote-Field Eddy Current Testing in Tubes

    NASA Astrophysics Data System (ADS)

    Jeng, Jin-Jhy

    2005-06-01

    Remote-field eddy current (RFEC) testing is a nondestructive testing method. It has been comprehensively applied to detect wall loss in ferromagnetic tubes. According to our experience, the problem of variations in a material’s electromagnetic characteristics often occurred in practice in carbon steel tubes. Therefore, if we fail to compensate for changes in electromagnetic characteristics during inspection, an error of evaluation will be generated. This study applied the skin-depth theory of RFEC and geometric relationships on the voltage plane to derive a compensatory model using a mathematical methodology. The new evaluation curve established on the basis of this mathematical methodology compensates for the error contributed by changing electromagnetic characteristics in the tube. The method offered by this study has proved to be reasonable, feasible and acceptable in terms of its mathematical derivation and in comparison with experimental result.

  10. Continuum model of tensile fracture of metal melts and its application to a problem of high-current electron irradiation of metals

    SciTech Connect

    Mayer, Alexander E. E-mail: mayer.al.evg@gmail.com; Mayer, Polina N.

    2015-07-21

    A continuum model of the metal melt fracture is formulated on the basis of the continuum mechanics and theory of metastable liquid. A character of temperature and strain rate dependences of the tensile strength that is predicted by the continuum model is verified, and parameters of the model are fitted with the use of the results of the molecular dynamics simulations for ultra-high strain rates (≥1–10/ns). A comparison with experimental data from literature is also presented for Al and Ni melts. Using the continuum model, the dynamic tensile strength of initially uniform melts of Al, Cu, Ni, Fe, Ti, and Pb within a wide range of strain rates (from 1–10/ms to 100/ns) and temperatures (from melting temperature up to 70–80% of critical temperature) is calculated. The model is applied to numerical investigation of a problem of the high-current electron irradiation of Al, Cu, and Fe targets.

  11. Colored Contact Lens Dangers

    MedlinePlus

    ... Halloween Hazard: The Hidden Dangers of Buying Decorative Contact Lenses Without a Prescription Sep. 26, 2013 It ... she first put in a pair of colored contact lenses, Laura Butler of Parkersburg, W.Va., had " ...

  12. Allergic Contact Dermatitis

    MedlinePlus

    ... causes of allergic contact dermatitis include nickel, chromates, rubber chemicals, and topical antibiotic ointments and creams. Frequent ... construction workers who are in contact with cement. Rubber chemicals are found in gloves, balloons, elastic in ...

  13. Contact characteristics for YBCO bulk superconductors

    NASA Astrophysics Data System (ADS)

    Yamamoto, Naoki; Sakai, Tomokazu; Sawa, Koichiro; Tomita, Masaru; Murakami, Masato

    2003-10-01

    We have studied the contact characteristics of two resin-impregnated YBCO (a composite of YBa 2Cu 3O y and Y 2BaCuO 5) bulk superconductors in mechanical contact. A switching phenomenon could be observed at a threshold current or a transfer current value in the V- I curves of the YBCO contact. The transfer current exceeded the previous value of 13.5 A at 77 K in the contact when the sample surfaces were carefully polished. The present results suggest that a pair of YBCO blocks might be applicable to the mechanical persistent current switch for superconducting magnetic energy storage and other superconducting systems run in a persistent current mode.

  14. Evaluation of Contact Separation Force Testing as a Screening Methodology for Electrical Socket Contacts

    NASA Technical Reports Server (NTRS)

    Green, Chris; Greenwell, Chris; Brusse, jay; Krus, Dennis; Leidecker, Henning

    2009-01-01

    During system level testing intermittent and permanent open circuit failures of mated, crimp removable, electrical contact pairs were experienced. The root cause of the failures was determined to be low (but not zero) contact forces applied by the socket contact tines against the engaging pin. The low contact force reduces the effectiveness of the wiping action of the socket tines against the pin. The observed failure mode may be produced when insufficient wiping during mate, demate and small relative movement in use allows for the accumulation of debris or insulating films that electrically separate the contact pair. The investigation identified at least three manufacturing process control problems associated with the socket contacts that enabled shipment of contacts susceptible to developing low contact forces: (1) Improper heat treatment of the socket tines resulting in plastic rather than elastic behavior; (2) Overly thinned socket tines at their base resulting in reduced pin retention forces; (3) insufficient screening tests to identify parts susceptible to the aforementioned failure mechanisms. The results from an extensive screening program of socket contacts utilizing the industry standard contact separation force test procedures are described herein. The investigation shows this method to be capable of identifying initially weak sockets. However, sockets whose contact retention forces may degrade during use may not be screened out by pin retention testing alone. Further investigations are required to correlate low contact retention forces with increased electrical contact resistance in the presence of insulating films that may accumulate in the use environment.

  15. Glasses and Contact Lenses

    MedlinePlus

    ... Here's Help White House Lunch Recipes Glasses and Contact Lenses KidsHealth > For Kids > Glasses and Contact Lenses Print A A A Text Size What's ... together the way they should. But eyeglasses or contact lenses, also called corrective lenses, can help most ...

  16. Complementary Barrier Infrared Detector (CBIRD) Contact Methods

    NASA Technical Reports Server (NTRS)

    Ting, David Z.; Hill, Cory J.; Gunapala, Sarath D.

    2013-01-01

    The performance of the CBIRD detector is enhanced by using new device contacting methods that have been developed. The detector structure features a narrow gap adsorber sandwiched between a pair of complementary, unipolar barriers that are, in turn, surrounded by contact layers. In this innovation, the contact adjacent to the hole barrier is doped n-type, while the contact adjacent to the electron barrier is doped p-type. The contact layers can have wider bandgaps than the adsorber layer, so long as good electrical contacts are made to them. If good electrical contacts are made to either (or both) of the barriers, then one could contact the barrier(s) directly, obviating the need for additional contact layers. Both the left and right contacts can be doped either n-type or ptype. Having an n-type contact layer next to the electron barrier creates a second p-n junction (the first being the one between the hole barrier and the adsorber) over which applied bias could drop. This reduces the voltage drop over the adsorber, thereby reducing dark current generation in the adsorber region.

  17. Contact lens in keratoconus

    PubMed Central

    Rathi, Varsha M; Mandathara, Preeji S; Dumpati, Srikanth

    2013-01-01

    Contact lenses are required for the visual improvement in patients with keratoconus. Various contact lens options, such as rigid gas permeable (RGP) lenses, soft and soft toric lenses, piggy back contact lenses (PBCL), hybrid lenses and scleral lenses are availble. This article discusses about selection of a lens depending on the type of keratoconus and the fitting philosophies of various contact lenses including the starting trial lens. A Medline search was carried out for articles in the English language with the keywords keratoconus and various contact lenses such as Rose k lens, RGP lens, hybrid lens, scleral lens and PBCL. PMID:23925325

  18. Modeling Thermal Contact Resistance

    NASA Technical Reports Server (NTRS)

    Kittel, Peter; Sperans, Joel (Technical Monitor)

    1994-01-01

    One difficulty in using cryocoolers is making good thermal contact between the cooler and the instrument being cooled. The connection is often made through a bolted joint. The temperature drop associated with this joint has been the subject of many experimental and theoretical studies. The low temperature behavior of dry joints have shown some anomalous dependence on the surface condition of the mating parts. There is also some doubts on how well one can extrapolate from the test samples to predicting the performance of a real system. Both finite element and analytic models of a simple contact system have been developed. The model assumes (a) the contact is dry (contact limited to a small portion of the total available area and the spaces in-between the actual contact patches are perfect insulators), (b) contacts are clean (conductivity of the actual contact is the same as the bulk), (c) small temperature gradients (the bulk conductance may be assumed to be temperature independent), (d) the absolute temperature is low (thermal radiation effects are ignored), and (e) the dimensions of the nominal contact area are small compared to the thickness of the bulk material (the contact effects are localized near the contact). The models show that in the limit of actual contact area much less than the nominal area (a much less than A), that the excess temperature drop due to a single point of contact scales as a(exp -1/2). This disturbance only extends a distance approx. A(exp 1/2) into the bulk material. A group of identical contacts will result in an excess temperature drop that scales as n(exp -1/2), where n is the number of contacts and n dot a is constant. This implies that flat rough surfaces will have a lower excess temperature drop than flat polished surfaces.

  19. Barrier/Cu contact resistivity

    SciTech Connect

    Reid, J.S.; Nicolet, M.A.; Angyal, M.S.; Lilienfeld, D.; Shacham-Diamand, Y.; Smith, P.M.

    1995-10-17

    The specific contact resistivity of Cu with ({alpha} + {beta})-Ta, TiN, {alpha}-W, and amorphous-Ta{sub 36}Si{sub 14}N{sub 50} barrier films is measured using a novel four-point-probe approach. Geometrically, the test structures consist of colinear sets of W-plugs to act as current and voltage probes that contact the bottom of a planar Cu/barrier/Cu stack. Underlying Al interconnects link the plugs to the current source and voltmeter. The center-to-center distance of the probes ranges from 3 to 200 {micro}m. Using a relation developed by Vu et al., a contact resistivity of roughly 7 {times} 10{sup {minus}9} {Omega} cm{sup 2} is obtained for all tested barrier/Cu combinations. By reflective-mode small-angle X-ray scattering, the similarity in contact resistivity among the barrier films may be related to interfacial impurities absorbed from the deposition process.

  20. Dynamics of the Molten Contact Line

    NASA Technical Reports Server (NTRS)

    Sonin, Ain A.; Schiaffino, Stefano

    1996-01-01

    In contrast to the ordinary contact line problem, virtually no information is available on the similar problem associated with a molten material spreading on a solid which is below the melt's fusion point. The latter is a more complex problem which heat transfer and solidification take place simultaneously with spreading, and requires answers not only for the hot melt's advance speed over the cold solid as a function of contact angle, but also for how one is to predict the point of the molten contact line's arrest by freezing. This issues are of importance in evolving methods of materials processing. The purpose of our work is to develop, based on both experiments and theory, an understanding of the dynamic processes that occur when a molten droplet touches a subcooled solid, spreads partly over it by capillary action, and freezes. We seek answers to the following basic questions. First, what is the relationship between the melt's contact line speed and the apparent (dynamic) contact angle? Secondly, at what point will the contact line modon be arrested by freezing? The talk will describe three components of our work: (1) deposition experiments with small molten droplets; (2) investigation of the dynamics of the molten contact line by means of a novel forced spreading method; and (3) an attempt to provide a theoretical framework for answering the basic questions posed above.

  1. Effect of microwave treatment on current flow mechanisms in Au-TiB{sub x}-Al-Ti-n{sup +}-n-n{sup +}-GaN-Al{sub 2}O{sub 3} ohmic contacts

    SciTech Connect

    Belyaev, A. E.; Boltovets, N. S.; Vitusevich, S. A.; Ivanov, V. N.; Konakova, R. V. Kudryk, Ya. Ya.; Lebedev, A. A.; Milenin, V. V.; Sveshnikov, Yu. N.; Sheremet, V. N.

    2010-06-15

    The temperature dependences of the contact resistivity {rho}{sub c} of Au-TiB{sub x} Al-Ti-n{sup +}-n-n{sup +}-GaN-Al{sub 2}O{sub 3} ohmic contacts have been studied before and after microwave treatment followed by nine-nonth room-temperature sample storage. The temperature dependences of {rho}{sub c} of initial samples were measured twice. The first measurement showed the temperature dependence typical of ohmic contacts; the repeated measurement in the temperature region above 270 K showed a {rho}{sub c} increase caused by metallic conductivity. After microwave treatment, the metallic conductivity in the ohmic contact is not observed. This is presumably associated with local heating of metal Ga inclusions under microwave irradiation and the formation, due to high chemical activity of liquid gallium, of compounds of it with other metallization components. In this case, the temperature dependence of {rho}{sub c} is controlled by ordinary charge transport mechanisms. After nine-nonth room-temperature storage, the temperature dependence of ?c is described by the tunneling mechanism of charge transport.

  2. Colors and contact dermatitis.

    PubMed

    Bonamonte, Domenico; Foti, Caterina; Romita, Paolo; Vestita, Michelangelo; Angelini, Gianni

    2014-01-01

    The diagnosis of skin diseases relies on several clinical signs, among which color is of paramount importance. In this review, we consider certain clinical presentations of both eczematous and noneczematous contact dermatitis in which color plays a peculiar role orientating toward the right diagnosis. The conditions that will be discussed include specific clinical-morphologic subtypes of eczematous contact dermatitis, primary melanocytic, and nonmelanocytic contact hyperchromia, black dermographism, contact chemical leukoderma, and others. Based on the physical, chemical, and biologic factors underlying a healthy skin color, the various skin shades drawing a disease picture are thoroughly debated, stressing their etiopathogenic origins and histopathologic aspects. PMID:25000236

  3. Constructions of contact manifolds

    NASA Astrophysics Data System (ADS)

    Geiges, Hansjörg

    1997-05-01

    1. IntroductionIt has been known for some time that contact structures show a high degree of topological flexibility in the sense that many topological operations can be performed on contact manifolds while preserving the contact property. For instance, Martinet [14] used a surgery description of 3-manifolds to show that every closed, oriented 3-manifold admits a contact structure, and alternative proofs of this result were given later by Thurston and Winkelnkemper [18], who based their proof on an open book decomposition, and Gonzalo [8], who used branched covers. These, however, are all strictly 3-dimensional constructions.

  4. Optical contact micrometer

    DOEpatents

    Jacobson, Steven D.

    2014-08-19

    Certain examples provide optical contact micrometers and methods of use. An example optical contact micrometer includes a pair of opposable lenses to receive an object and immobilize the object in a position. The example optical contact micrometer includes a pair of opposable mirrors positioned with respect to the pair of lenses to facilitate viewing of the object through the lenses. The example optical contact micrometer includes a microscope to facilitate viewing of the object through the lenses via the mirrors; and an interferometer to obtain one or more measurements of the object.

  5. Evaluation of the electrical contact area in contact-mode scanning probe microscopy

    SciTech Connect

    Celano, Umberto E-mail: u.celano@gmail.com; Chintala, Ravi Chandra; Vandervorst, Wilfried; Hantschel, Thomas; Giammaria, Guido; Conard, Thierry; Bender, Hugo

    2015-06-07

    The tunneling current through an atomic force microscopy (AFM) tip is used to evaluate the effective electrical contact area, which exists between tip and sample in contact-AFM electrical measurements. A simple procedure for the evaluation of the effective electrical contact area is described using conductive atomic force microscopy (C-AFM) in combination with a thin dielectric. We characterize the electrical contact area for coated metal and doped-diamond tips operated at low force (<200 nN) in contact mode. In both cases, we observe that only a small fraction (<10 nm{sup 2}) of the physical contact (∼100 nm{sup 2}) is effectively contributing to the transport phenomena. Assuming this reduced area is confined to the central area of the physical contact, these results explain the sub-10 nm electrical resolution observed in C-AFM measurements.

  6. Evaluation of the electrical contact area in contact-mode scanning probe microscopy

    NASA Astrophysics Data System (ADS)

    Celano, Umberto; Hantschel, Thomas; Giammaria, Guido; Chintala, Ravi Chandra; Conard, Thierry; Bender, Hugo; Vandervorst, Wilfried

    2015-06-01

    The tunneling current through an atomic force microscopy (AFM) tip is used to evaluate the effective electrical contact area, which exists between tip and sample in contact-AFM electrical measurements. A simple procedure for the evaluation of the effective electrical contact area is described using conductive atomic force microscopy (C-AFM) in combination with a thin dielectric. We characterize the electrical contact area for coated metal and doped-diamond tips operated at low force (<200 nN) in contact mode. In both cases, we observe that only a small fraction (<10 nm2) of the physical contact (˜100 nm2) is effectively contributing to the transport phenomena. Assuming this reduced area is confined to the central area of the physical contact, these results explain the sub-10 nm electrical resolution observed in C-AFM measurements.

  7. Language Contact: An Introduction.

    ERIC Educational Resources Information Center

    Thomason, Sarah G.

    This book surveys situations in which language contact arises and focuses on what happens to the languages themselves: sometimes nothing, sometimes the incorporation of new words, sometimes the spread of new sounds and sentence structures across many languages and wide swathes of territory. It outlines the origins and results of contact-induced…

  8. Miniature intermittent contact switch

    NASA Technical Reports Server (NTRS)

    Sword, A.

    1972-01-01

    Design of electric switch for providing intermittent contact is presented. Switch consists of flexible conductor surrounding, but separated from, fixed conductor. Flexing of outside conductor to contact fixed conductor completes circuit. Advantage is small size of switch compared to standard switches.

  9. Multibody dynamic simulation of knee contact mechanics

    PubMed Central

    Bei, Yanhong; Fregly, Benjamin J.

    2006-01-01

    Multibody dynamic musculoskeletal models capable of predicting muscle forces and joint contact pressures simultaneously would be valuable for studying clinical issues related to knee joint degeneration and restoration. Current three-dimensional multi-body knee models are either quasi-static with deformable contact or dynamic with rigid contact. This study proposes a computationally efficient methodology for combining multibody dynamic simulation methods with a deformable contact knee model. The methodology requires preparation of the articular surface geometry, development of efficient methods to calculate distances between contact surfaces, implementation of an efficient contact solver that accounts for the unique characteristics of human joints, and specification of an application programming interface for integration with any multibody dynamic simulation environment. The current implementation accommodates natural or artificial tibiofemoral joint models, small or large strain contact models, and linear or nonlinear material models. Applications are presented for static analysis (via dynamic simulation) of a natural knee model created from MRI and CT data and dynamic simulation of an artificial knee model produced from manufacturer’s CAD data. Small and large strain natural knee static analyses required 1 min of CPU time and predicted similar contact conditions except for peak pressure, which was higher for the large strain model. Linear and nonlinear artificial knee dynamic simulations required 10 min of CPU time and predicted similar contact force and torque but different contact pressures, which were lower for the nonlinear model due to increased contact area. This methodology provides an important step toward the realization of dynamic musculoskeletal models that can predict in vivo knee joint motion and loading simultaneously. PMID:15564115

  10. Noneczematous Contact Dermatitis

    PubMed Central

    Foti, Caterina; Vestita, Michelangelo; Angelini, Gianni

    2013-01-01

    Irritant or allergic contact dermatitis usually presents as an eczematous process, clinically characterized by erythematoedematovesicous lesions with intense itching in the acute phase. Such manifestations become erythematous-scaly as the condition progresses to the subacute phase and papular-hyperkeratotic in the chronic phase. Not infrequently, however, contact dermatitis presents with noneczematous features. The reasons underlying this clinical polymorphism lie in the different noxae and contact modalities, as well as in the individual susceptibility and the various targeted cutaneous structures. The most represented forms of non-eczematous contact dermatitis include the erythema multiforme-like, the purpuric, the lichenoid, and the pigmented kinds. These clinical entities must obviously be discerned from the corresponding “pure” dermatitis, which are not associated with contact with exogenous agents. PMID:24109520

  11. Hertzian contact in two and three dimensions

    NASA Technical Reports Server (NTRS)

    Tripp, J. H.

    1985-01-01

    The basic solution to the problem of mechanical contact between elastically deforming solids was proposed by Hertz over a century ago and has been used by tribologists and others ever since in a steadily increasing number of applications. While the theoretical development is not conceptually difficult and treatments exist to suit all tastes, it is nonetheless interesting to trace the relationships among the solutions in different dimensions. Such an approach is used herein to shed light on the curious and sometimes perplexing behavior of line contacts. A number of the more frequently used contact expressions together as a convenient reference and for comparative purposes.

  12. Quick, stable, safe and economical preheating of glass mat reinforced thermoplastics in a contact heating oven

    SciTech Connect

    Michaeli, W.; Starke, J.

    1993-12-31

    Glass mat reinforced thermoplastics (GMT) which belong to the group of sheet thermoplastic composites (STC) are processed in compression moulding for structural parts. Before moulding the material, it has to be preheated currently by IR-radiation or by air convection. Using a contact heating oven, preheating can be speeded up combined with a significant higher energetic efficiency. But up to now, operation using the contact heating method failed due to the tackiness of the matrix material in solid state. IKV has recently created a solution for the problem of tackiness by transporting the glass mat reinforced material between two belts coated with PTFE through a contact oven. This preheating line includes a shock-cooler to quickly cool down a thin layer of the GMT`s surface. By this, separating the GMT from the PTFE without leaving particles on the belt is possible. The contact heating method not only includes the advantage of a significant higher energetic efficiency, but also benefits in processing. The risk of matrix degradation is distinctly reduced in comparison to other preheating methods, since the material does not expand in thickness for more than 200% and therefore air cannot come intensively into contact with the material. Consequently, the contact preheating is well qualified for matrix materials susceptible for oxidation. In this paper the physical coherence, the adhesion and the cohesion of GMT, are, described. Furthermore experimental results with a contact preheating line are presented.

  13. Color-gradient lattice Boltzmann model for simulating droplet motion with contact-angle hysteresis

    NASA Astrophysics Data System (ADS)

    Ba, Yan; Liu, Haihu; Sun, Jinju; Zheng, Rongye

    2013-10-01

    Lattice Boltzmann method (LBM) is an effective tool for simulating the contact-line motion due to the nature of its microscopic dynamics. In contact-line motion, contact-angle hysteresis is an inherent phenomenon, but it is neglected in most existing color-gradient based LBMs. In this paper, a color-gradient based multiphase LBM is developed to simulate the contact-line motion, particularly with the hysteresis of contact angle involved. In this model, the perturbation operator based on the continuum surface force concept is introduced to model the interfacial tension, and the recoloring operator proposed by Latva-Kokko and Rothman is used to produce phase segregation and resolve the lattice pinning problem. At the solid surface, the color-conserving wetting boundary condition [Hollis , IMA J. Appl. Math.IJAMDM0272-496010.1093/imamat/hxr008 76, 726 (2011)] is applied to improve the accuracy of simulations and suppress spurious currents at the contact line. In particular, we present a numerical algorithm to allow for the effect of the contact-angle hysteresis, in which an iterative procedure is used to determine the dynamic contact angle. Numerical simulations are conducted to verify the developed model, including the droplet partial wetting process and droplet dynamical behavior in a simple shear flow. The obtained results are compared with theoretical solutions and experimental data, indicating that the model is able to predict the equilibrium droplet shape as well as the dynamic process of partial wetting and thus permits accurate prediction of contact-line motion with the consideration of contact-angle hysteresis.

  14. Development of a second generation rolling contact fatigue tester

    NASA Astrophysics Data System (ADS)

    Deshmukh, Satyam U.

    Contact fatigue failure has been in research since the early twentieth century. The need for a second generation sliding-rolling contact fatigue tester was proposed by Gregory Dvorak and Dr. Marcellin Zahui. The first generation RCF tester was used for testing super finishing processes for gear surfaces. The second generation RCF tester was funded by the Advanced Engineering Materials lab of University of North Dakota. Verification of the second generation Rolling Contact Fatigue Tester will be discussed in this thesis including the design details, assembly and testing procedure and to discuss its different parameters. The tester will have the capability of testing hollow specimens using a bobbin eddy current testing probe. This tester will allow a wide range of experiments and is not built for one specific purpose. An eddy current device is used for detecting cracks. The loading force is applied using hydraulic cylinders and a hydraulic power unit. Before testing began, the machine was run for some time at full speed. A lot of minor problems were detected and fixed. Three specimens of AISI 8620 were tested in this tester. All tests gave results matching with some of the other well-known RCF testers. These tests were performed to evaluate mechanical limits of the tester and to evaluate the software performance of the tester.

  15. FAST ACTING CURRENT SWITCH

    DOEpatents

    Batzer, T.H.; Cummings, D.B.; Ryan, J.F.

    1962-05-22

    A high-current, fast-acting switch is designed for utilization as a crowbar switch in a high-current circuit such as used to generate the magnetic confinement field of a plasma-confining and heat device, e.g., Pyrotron. The device particularly comprises a cylindrical housing containing two stationary, cylindrical contacts between which a movable contact is bridged to close the switch. The movable contact is actuated by a differential-pressure, airdriven piston assembly also within the housing. To absorb the acceleration (and the shock imparted to the device by the rapidly driven, movable contact), an adjustable air buffer assembly is provided, integrally connected to the movable contact and piston assembly. Various safety locks and circuit-synchronizing means are also provided to permit proper cooperation of the invention and the high-current circuit in which it is installed. (AEC)

  16. A theoretical study of optical contact of vitreous silica

    NASA Technical Reports Server (NTRS)

    Barber, T. D.

    1972-01-01

    Optical contact has been proposed as a method of bonding quartz parts of the Stanford relativity satellite. The theory of the van der Waals force is outlined and applied to the problem of optical contact. The effect of various contaminations is discussed and a program of experimentation for further study of the problem is presented.

  17. Frictionless contact of aircraft tires

    NASA Technical Reports Server (NTRS)

    Kim, Kyun O.; Tanner, John A.; Noor, Ahmed K.

    1989-01-01

    A computational procedure for the solution of frictionless contact problems of spacecraft tires was developed using a two-dimensional laminated anisotropic shell theory incorporating the effects of variations in material and geometric parameters, transverse shear deformation, and geometric nonlinearities to model the nose-gear tire of a space shuttle. Numerical results are presented for the case when the nose-gear tire is subjected to inflation pressure and pressed against a rigid pavement. The results are compared with experimental results obtained at NASA Langley, demonstrating a high accuracy of the model and the effectiveness of the computational procedure.

  18. Sensing with Superconducting Point Contacts

    PubMed Central

    Nurbawono, Argo; Zhang, Chun

    2012-01-01

    Superconducting point contacts have been used for measuring magnetic polarizations, identifying magnetic impurities, electronic structures, and even the vibrational modes of small molecules. Due to intrinsically small energy scale in the subgap structures of the supercurrent determined by the size of the superconducting energy gap, superconductors provide ultrahigh sensitivities for high resolution spectroscopies. The so-called Andreev reflection process between normal metal and superconductor carries complex and rich information which can be utilized as powerful sensor when fully exploited. In this review, we would discuss recent experimental and theoretical developments in the supercurrent transport through superconducting point contacts and their relevance to sensing applications, and we would highlight their current issues and potentials. A true utilization of the method based on Andreev reflection analysis opens up possibilities for a new class of ultrasensitive sensors. PMID:22778630

  19. Contact microscopy with synchrotron radiation

    SciTech Connect

    Panessa-Warren, B.J.

    1985-10-01

    Soft x-ray contact microscopy with synchrotron radiation offers the biologist and especially the microscopist, a way to morphologically study specimens that could not be imaged by conventional TEM, STEM or SEM methods (i.e. hydrated samples, samples easily damaged by an electron beam, electron dense samples, thick specimens, unstained low contrast specimens) at spatial resolutions approaching those of the TEM, with the additional possibility to obtain compositional (elemental) information about the sample as well. Although flash x-ray sources offer faster exposure times, synchrotron radiation provides a highly collimated, intense radiation that can be tuned to select specific discrete ranges of x-ray wavelengths or specific individual wavelengths which optimize imaging or microanalysis of a specific sample. This paper presents an overview of the applications of x-ray contact microscopy to biological research and some current research results using monochromatic synchrotron radiation to image biological samples. 24 refs., 10 figs.

  20. Telescopic vision contact lens

    NASA Astrophysics Data System (ADS)

    Tremblay, Eric J.; Beer, R. Dirk; Arianpour, Ashkan; Ford, Joseph E.

    2011-03-01

    We present the concept, optical design, and first proof of principle experimental results for a telescopic contact lens intended to become a visual aid for age-related macular degeneration (AMD), providing magnification to the user without surgery or external head-mounted optics. Our contact lens optical system can provide a combination of telescopic and non-magnified vision through two independent optical paths through the contact lens. The magnified optical path incorporates a telescopic arrangement of positive and negative annular concentric reflectors to achieve 2.8x - 3x magnification on the eye, while light passing through a central clear aperture provides unmagnified vision.

  1. Optical contacting of quartz

    NASA Technical Reports Server (NTRS)

    Payne, L. L.

    1982-01-01

    The strength of the bond between optically contacted quartz surfaces was investigated. The Gravity Probe-B (GP-B) experiment to test the theories of general relativity requires extremely precise measurements. The quartz components of the instruments to make these measurements must be held together in a very stable unit. Optical contacting is suggested as a possible method of joining these components. The fundamental forces involved in optical contacting are reviewed and relates calculations of these forces to the results obtained in experiments.

  2. Study of barrier height and trap centers of Au/n-Hg{sub 3}In{sub 2}Te{sub 6} Schottky contacts by current-voltage (I-V) characteristics and deep level transient spectroscopy

    SciTech Connect

    Li, Yapeng; Fu, Li Sun, Jie; Wang, Xiaozhen

    2015-02-28

    The temperature-dependent electrical characteristics of the Au/n-Hg{sub 3}In{sub 2}Te{sub 6} Schottky contact have been studied at the temperature range of 140 K–315 K. Based on the thermionic emission theory, the ideality factor and Schottky barrier height were calculated to decrease and increase from 3.18 to 1.88 and 0.39 eV to 0.5 eV, respectively, when the temperature rose from 140 K to 315 K. This behavior was interpreted by the lateral inhomogeneities of Schottky barrier height at the interface of Au/n-Hg{sub 3}In{sub 2}Te{sub 6} contact, which was shown by the plot of zero-bias barrier heights Φ{sub bo} versus q/2kT. Meanwhile, it was found that the Schottky barrier height with a Gaussian distribution was 0.67 eV and the standard deviation σ{sub 0} was about 0.092 eV, indicating that the uneven distribution of barrier height at the interface region. In addition, the mean value of Φ{sup ¯}{sub b0} and modified Richardson constant was determined to be 0.723 eV and 62.8 A/cm{sup 2}K{sup 2} from the slope and intercept of the ln(I{sub o}/T{sup 2}) – (qσ{sub 0}{sup 2}/2k{sup 2}T{sup 2}) versus q/kT plot, respectively. Finally, two electron trap centers were observed at the interface of Au/n-Hg{sub 3}In{sub 2}Te{sub 6} Schottky contact by means of deep level transient spectroscopy.

  3. Improving performance of the metal-to-metal contact RF MEMS switch with a Pt-Au microspring contact design

    NASA Astrophysics Data System (ADS)

    Liu, Bo; Lv, Zhiqiu; He, Xunjun; Liu, Meng; Hao, Yilong; Li, Zhihong

    2011-06-01

    Performances of the metal-to-metal contact radio frequency (RF) MEMS switches largely rely on the contacts. A novel contact employing the microspring structure is demonstrated in this paper. The microspring contact can achieve a stable contact at lower actuation voltage, alleviating mechanical wear on the contacts, and can effectively increase the fabrication tolerance. An in-line Pt-Au microspring contact switch was fabricated and characterized. To evaluate the improvement in performance, the results were compared with those of the Au-Au solid contact switch without a microspring design. The highest current handled by the Pt-Au microspring contact was 150 mA per contact, whereas only 20 mA was handled by the Au-Au solid contact. The insertion loss of the Pt-Au microspring contact switch was -0.2 dB at 20 GHz, which was comparable with that of the Au-Au solid contact switch. The isolation of the Pt-Au microspring contact switch was -22 dB at 20 GHz, and that of the Au-Au solid contact switch was -18 dB. With the Pt-Au microspring contact, the switch exceeds its power handling ability and reliability with comparable RF performances.

  4. Surrogate modeling of deformable joint contact using artificial neural networks.

    PubMed

    Eskinazi, Ilan; Fregly, Benjamin J

    2015-09-01

    Deformable joint contact models can be used to estimate loading conditions for cartilage-cartilage, implant-implant, human-orthotic, and foot-ground interactions. However, contact evaluations are often so expensive computationally that they can be prohibitive for simulations or optimizations requiring thousands or even millions of contact evaluations. To overcome this limitation, we developed a novel surrogate contact modeling method based on artificial neural networks (ANNs). The method uses special sampling techniques to gather input-output data points from an original (slow) contact model in multiple domains of input space, where each domain represents a different physical situation likely to be encountered. For each contact force and torque output by the original contact model, a multi-layer feed-forward ANN is defined, trained, and incorporated into a surrogate contact model. As an evaluation problem, we created an ANN-based surrogate contact model of an artificial tibiofemoral joint using over 75,000 evaluations of a fine-grid elastic foundation (EF) contact model. The surrogate contact model computed contact forces and torques about 1000 times faster than a less accurate coarse grid EF contact model. Furthermore, the surrogate contact model was seven times more accurate than the coarse grid EF contact model within the input domain of a walking motion. For larger input domains, the surrogate contact model showed the expected trend of increasing error with increasing domain size. In addition, the surrogate contact model was able to identify out-of-contact situations with high accuracy. Computational contact models created using our proposed ANN approach may remove an important computational bottleneck from musculoskeletal simulations or optimizations incorporating deformable joint contact models. PMID:26220591

  5. Design and fabrication of wraparound contact silicon solar cells

    NASA Technical Reports Server (NTRS)

    Scott-Monck, J. A.; Stella, P. M.; Avery, J. E.

    1972-01-01

    Both dielectric insulation and etched junction contact techniques were evaluated for use in wraparound contact cell fabrication. Since a suitable process for depositing the dielectrics was not achieved, the latter approach was taken. The relationship between loss of back contact and power degradation due to increased series resistance was established and used to design a simple contact configuration for 10 ohm-cm etched wraparound junction contact N/P cells. A slightly deeper junction significantly improved cell curve shape and the associated loss of current was regained by using thinner contact grid fingers. One thousand cells with efficiencies greater than 10.5% were fabricated to demonstrate the process.

  6. Occupational Contact Dermatitis

    PubMed Central

    2008-01-01

    Occupational contact dermatitis accounts for 90% of all cases of work-related cutaneous disorders. It can be divided into irritant contact dermatitis, which occurs in 80% of cases, and allergic contact dermatitis. In most cases, both types will present as eczematous lesions on exposed parts of the body, notably the hands. Accurate diagnosis relies on meticulous history taking, thorough physical examination, careful reading of Material Safety Data Sheets to distinguish between irritants and allergens, and comprehensive patch testing to confirm or rule out allergic sensitization. This article reviews the pathogenesis and clinical manifestations of occupational contact dermatitis and provides diagnostic guidelines and a rational approach to management of these often frustrating cases. PMID:20525126

  7. Contacting American Overseas Schools.

    ERIC Educational Resources Information Center

    Engelhardt, David

    1993-01-01

    Provides contacts for architects or educational consultants who wish to work overseas. Cites a directory, newsletters, newspapers, and associations focused on educators involved with independent overseas schools that are organized around the United States curriculum. (MLF)

  8. Metal contact reliability of RF MEMS switches

    NASA Astrophysics Data System (ADS)

    Ma, Qing; Tran, Quan; Chou, Tsung-Kuan A.; Heck, John; Bar, Hanan; Kant, Rishi; Rao, Valluri

    2007-01-01

    It is well-recognized that MEMS switches, compared to their more traditional solid state counterparts, have several important advantages for wireless communications. These include superior linearity, low insertion loss and high isolation. Indeed, many potential applications have been investigated such as Tx/Rx antenna switching, frequency band selection, tunable matching networks for PA and antenna, tunable filters, and antenna reconfiguration. However, none of these applications have been materialized in high volume products to a large extent because of reliability concerns, particularly those related to the metal contacts. The subject of the metal contact in a switch was studied extensively in the history of developing miniaturized switches, such as the reed switches for telecommunication applications. While such studies are highly relevant, they do not address the issues encountered in the sub 100μN, low contact force regime in which most MEMS switches operate. At such low forces, the contact resistance is extremely sensitive to even a trace amount of contamination on the contact surfaces. Significant work was done to develop wafer cleaning processes and storage techniques for maintaining the cleanliness. To preserve contact cleanliness over the switch service lifetime, several hermetic packaging technologies were developed and their effectiveness in protecting the contacts from contamination was examined. The contact reliability is also very much influenced by the contact metal selection. When pure Au, a relatively soft metal, was used as the contact material, significant stiction problems occurred when clean switches were cycled in an N II environment. In addition, various mechanical damages occurred after extended switching cycling tests. Harder metals, while more resistant to deformation and stiction, are more sensitive to chemical reactions, particularly oxidation. They also lead to higher contact resistance because of their lower electrical conductivity

  9. Contact Interface Verification for DYNA3D Scenario 2: Multi-Surface Contact

    SciTech Connect

    McMichael, L D

    2006-05-10

    A suite of test problems has been developed to examine contact behavior within the nonlinear, three-dimensional, explicit finite element analysis (FEA) code DYNA3D (Lin, 2005). The test problems use multiple interfaces and a combination of enforcement methods to assess the basic functionality of the contact algorithms. The results from the DYNA3D analyses are compared to closed form solutions to verify the contact behavior. This work was performed as part of the Verification and Validation efforts of LLNL W Program within the NNSA's Advanced Simulation and Computing (ASC) Program. DYNA3D models the transient dynamic response of solids and structures including the interactions between disjoint bodies (parts). A wide variety of contact surfaces are available to represent the diverse interactions possible during an analysis, including relative motion (sliding), separation and gap closure (voids), and fixed relative position (tied). The problem geometry may be defined using a combination of element formulations, including one-dimensional beam and truss elements, two-dimensional shell elements, and three-dimensional solid elements. Consequently, it is necessary to consider various element interactions during contact. This report and associated test problems examine the scenario where multiple bodies interact with each other via multiple interfaces. The test problems focus on whether any ordering issues exist in the contact logic by using a combination of interface types, contact enforcement options (i.e., penalty, Lagrange, and kinematic), and element interactions within each problem. The influence of rigid materials on interface behavior is also examined. The companion report (McMichael, 2006) and associated test problems address the basic contact scenario where one contact surface exists between two disjoint bodies. The test problems are analyzed using version 5.2 (compiled on 12/22/2005) of DYNA3D. The analytical results are used to form baseline solutions for

  10. Amorphous Ge bipolar blocking contacts on Ge detectors

    SciTech Connect

    Luke, P.N.; Cork, C.P.; Madden, N.W.; Rossington, C.S.; Wesela, M.F.

    1991-10-01

    Semiconductor nuclear radiation detectors are usually operated in a full depletion mode and blocking contacts are required to maintain low leakage currents and high electric fields for charge collection. Blocking contacts on Ge detectors typically consist of n-type contacts formed by lithium diffusion and p-type contacts formed by boron ion implantation. Electrical contacts formed using sputtered amorphous Ge (a-Ge) films on high-purity Ge crystals were found to exhibit good blocking behavior in both polarities with low leakage currents. The a-Ge contacts have thin dead layers associated with them and can be used in place of lithium-diffused, ion-implanted or Schottky barrier contacts on Ge radiation detectors. Multi-electrode detectors can be fabricated with very simple processing steps using these contacts. 12 refs.

  11. ELECTRIC CONTACT MEANS

    DOEpatents

    Grear, J.W. Jr.

    1959-03-10

    A switch adapted to maintain electrical connections under conditions of vibration or acceleration is described. According to the invention, thc switch includes a rotatable arm carrying a conductive bar arranged to close against two contacts spaced in the same plane. The firm and continuous engagement of the conductive bar with the contacts is acheived by utilizeing a spring located betwenn the vbar and athe a rem frzme and slidable mounting the bar in channel between two arms suspendef from the arm frame.

  12. The impact of contact

    NASA Astrophysics Data System (ADS)

    Finney, B.

    1986-10-01

    Scenarios of the impact on human society of radio contact with an extraterrestrial civilization are presented. Some believe that contact with advanced extraterrestrials would quickly devastate the human spirit, while others believe that these super-intelligent beings would show the inhabitants of the earth how to live in peace. It is proposed that the possible existence of extraterrestrial civilizations and the development of means of studying and communicating with them need to be considered.

  13. Contact dermatitis complicating pinnaplasty.

    PubMed

    Singh-Ranger, G; Britto, J A; Sommerlad, B C

    2001-04-01

    Proflavine allergy is uncommon, occurring in approximately 6% of patients attending contact dermatitis clinics. Proflavine wool is used by many surgeons in the UK as a dressing that can be moulded to conform to the contours of a corrected prominent ear. It may have bacteriostatic properties. We present a case where contact dermatitis in response to proflavine developed after pinnaplasty. This caused diagnostic confusion, a lengthened hospital stay and an unsightly hypertrophic scar. PMID:11254419

  14. Contact resistance of 500 mesh regenerator screens

    NASA Astrophysics Data System (ADS)

    Lee, A. C.; Ravikumar, K. V.; Frederking, T. H. K.

    The electrical contact resistance of stainless steel screen stacks at room temperature and at liquid nitrogen temperature has been measured as a function of externally applied mechanical load (weight). The data show a nearly linear voltage versus current function at small loads (up to 100 mA). The force has been varied up to a specific load of 1 N cm -2. From the data the (apparent) thermal conductance is deduced via the Lorenz number and via the (average) elastically deformed contact domain area of the Hertz theory. The conductances obtained appear to be consistent with literature data for thermal contact conductances of similar systems.

  15. Lettuce contact allergy.

    PubMed

    Paulsen, Evy; Andersen, Klaus E

    2016-02-01

    Lettuce (Lactuca sativa L.) and its varieties are important vegetable crops worldwide. They are also well-known, rarely reported, causes of contact allergy. As lettuce allergens and extracts are not commercially available, the allergy may be underdiagnosed. The aims of this article are to present new data on lettuce contact allergy and review the literature. Lettuce is weakly allergenic, and occupational cases are mainly reported. Using aimed patch testing in Compositae-allergic patients, two recent Danish studies showed prevalence rates of positive lettuce reactions of 11% and 22%. The majority of cases are non-occupational, and may partly be caused by cross-reactivity. The sesquiterpene lactone mix seems to be a poor screening agent for lettuce contact allergy, as the prevalence of positive reactions is significantly higher in non-occupationally sensitized patients. Because of the easy degradability of lettuce allergens, it is recommended to patch test with freshly cut lettuce stem and supplement this with Compositae mix. As contact urticaria and protein contact dermatitis may present as dermatitis, it is important to perform prick-to-prick tests, and possibly scratch patch tests as well. Any person who is occupationally exposed to lettuce for longer periods, especially atopics, amateur gardeners, and persons keeping lettuce-eating pets, is potentially at risk of developing lettuce contact allergy. PMID:26289653

  16. Experiments on thermal contact conductance between metals below 100 K

    NASA Astrophysics Data System (ADS)

    Choi, Yeon Suk; Kim, Myung Su

    2014-01-01

    The thermal contact conductance is one of the important components in heat transfer mechanism. The accurate estimation of thermal contact conductance is necessary for the development of a conduction-cooled superconducting magnet system because the metallic materials are thermally connected to the refrigerator or heat sink to cool the superconducting magnet without cryogen. The contact resistance occurs at the interface between metals and the amount of conductance can be affected by various factors, such as surface roughness, contact area, and contact pressure. In the superconducting magnet system, there are several metal components in contact with each other for cooling magnet as well as supplying current to the magnet. Therefore, a temperature gradient exists between superconducting magnet and cryocooler. In this study, we have developed the thermal contact conductance measurement system and used the steady state method to measure the thermal conductance between metals. The effects of temperature, contact pressure and interfacial materials on the thermal contact conductance are also discussed.

  17. Six challenges in measuring contact networks for use in modelling.

    PubMed

    Eames, K; Bansal, S; Frost, S; Riley, S

    2015-03-01

    Contact networks are playing an increasingly important role in epidemiology. A contact network represents individuals in a host population as nodes and the interactions among them that may lead to the transmission of infection as edges. New avenues for data collection in recent years have afforded us the opportunity to collect individual- and population-scale information to empirically describe the patterns of contact within host populations. Here, we present some of the current challenges in measuring empirical contact networks. We address fundamental questions such as defining contact; measurement of non-trivial contact properties; practical issues of bounding measurement of contact networks in space, time and scope; exploiting proxy information about contacts; dealing with missing data. Finally, we consider the privacy and ethical issues surrounding the collection of contact network data. PMID:25843388

  18. Current titles

    SciTech Connect

    1995-07-01

    This booklet is published for those interested in current research being conducted at the National Center for Electron Microscopy. The NCEM is a DOE-designated national user facility and is available at no charge to qualified researchers. Access is controlled by an external steering committee. Interested researchers may contact Gretchen Hermes at (510) 486-5006 or address below for a User`s Guide. Copies of available papers can be ordered from: Theda Crawford National Center for Electron Microscopy, Lawrence Berkeley Laboratory, One Cyclotron Rd., MS72, Berkeley, California, USA 94720.

  19. Inverse Problems of Thermoelectricity

    NASA Astrophysics Data System (ADS)

    Anatychuk, L. I.; Luste, O. J.; Kuz, R. V.; Strutinsky, M. N.

    2011-05-01

    Classical thermoelectricity is based on the use of the Seebeck and Thomson effects that occur in the near-contact areas between n- and p-type materials. A conceptually different approach to thermoelectric power converter design that is based on the law of thermoelectric induction of currents is also known. The efficiency of this approach has already been demonstrated by its first applications. More than 10 basically new types of thermoelements were discovered with properties that cannot be achieved by thermocouple power converters. Therefore, further development of this concept is of practical interest. This paper provides a classification and theory for solving the inverse problems of thermoelectricity that form the basis for devising new thermoelement types. Computer methods for their solution for anisotropic and inhomogeneous media are elaborated. Regularities related to thermoelectric current excitation in anisotropic and inhomogeneous media are established. The possibility of obtaining eddy currents of a particular configuration through control of the temperature field and material parameters for the creation of new thermo- element types is demonstrated for three-dimensional (3D) models of anisotropic and inhomogeneous media.

  20. GIS diagnostics: thermal imaging systems used for poor contact detection

    NASA Astrophysics Data System (ADS)

    Avital, Doron; Brandenbursky, V.; Farber, A.

    2004-04-01

    The reliability of GIS is very high but any failure that occurs can cause extensive damage result and the repair times are considerably long. The consequential losses to system security and economically can be high, especially if the nominal GIS voltage is 420 kV and above. In view of these circumstances, increasing attention is being given to diagnostic techniques for in-service maintenance undertaken to improve the reliability and availability of GIS. Recently considerable progress has been made in diagnostic techniques and they are now used successfully during the service life of the equipment. These diagnostic techniques in general focus on the GIS insulation system and are based on partial discharge (PD) measurements in GIS. There are three main methods for in-service PD detection in GIS: - the chemical method that rely on the detection of cracked gas caused by PD, the acoustic method designed to detect the acoustic emission excited by PD, and, the electrical method which is based on detection of electrical resonance at ultra high frequencies (UHF) up to 1.5 GHz caused by PD excitation in GIS chambers (UHF method). These three dielectric diagnostic methods cannot be used for the detection of poor current carrying contacts in GIS. This problem does not always produce partial discharges and at early stages it does not cause gas cracking. An interesting solution to use two techniques - the current unbalance alarm scheme and partial discharge monitoring was advised by A. Salinas from South California Edison Co. Unfortunately this way is complicated and very expensive. The investigations performed in Japan on standing alone SF6 breaker showed that joule heating of the contact accompanied by released power of 1600 Watt produce temperature difference on the enclosure up to 7 degrees centigrade that could be detected by infra-red Thermal Imaging System. According to CIGRE Joint Working Group 33/23.12 Report, 11% of all GIS failures are due to poor current carrying

  1. The modular approach enables a fully ab initio simulation of the contacts between 3D and 2D materials.

    PubMed

    Fediai, Artem; Ryndyk, Dmitry A; Cuniberti, Gianaurelio

    2016-10-01

    Up to now, the electrical properties of the contacts between 3D metals and 2D materials have never been computed at a fully ab initio level due to the huge number of atomic orbitals involved in a current path from an electrode to a pristine 2D material. As a result, there are still numerous open questions and controversial theories on the electrical properties of systems with 3D/2D interfaces-for example, the current path and the contact length scalability. Our work provides a first-principles solution to this long-standing problem with the use of the modular approach, a method which rigorously combines a Green function formalism with the density functional theory (DFT) for this particular contact type. The modular approach is a general approach valid for any 3D/2D contact. As an example, we apply it to the most investigated among 3D/2D contacts-metal/graphene contacts-and show its abilities and consistency by comparison with existing experimental data. As it is applicable to any 3D/2D interface, the modular approach allows the engineering of 3D/2D contacts with the pre-defined electrical properties. PMID:27502169

  2. Toward patient-specific articular contact mechanics

    PubMed Central

    Ateshian, Gerard A.; Henak, Corinne R.; Weiss, Jeffrey A.

    2015-01-01

    The mechanics of contacting cartilage layers is fundamentally important to understanding the development, homeostasis and pathology of diarthrodial joints. Because of the highly nonlinear nature of both the materials and the contact problem itself, numerical methods such as the finite element method are typically incorporated to obtain solutions. Over the course of five decades, we have moved from an initial qualitative understanding of articular cartilage material behavior to the ability to perform complex, three-dimensional contact analysis, including multiphasic material representations. This history includes the development of analytical and computational contact analysis methods that now provide the ability to perform highly nonlinear analyses. Numerical implementations of contact analysis based on the finite element method are rapidly advancing and will soon enable patient-specific analysis of joint contact mechanics using models based on medical image data. In addition to contact stress on the articular surfaces, these techniques can predict variations in strain and strain through the cartilage layers, providing the basis to predict damage and failure. This opens up exciting areas for future research and application to patient-specific diagnosis and treatment planning applied to a variety of pathologies that affect joint function and cartilage homeostasis. PMID:25698236

  3. Generations of Monic Polynomials such that the Coefficients of Each Polynomial of the Next Generation Coincide with the Zeros of a Polynomial of the Current Generation, and New Solvable Many-Body Problems

    NASA Astrophysics Data System (ADS)

    Bihun, Oksana; Calogero, Francesco

    2016-07-01

    The notion of generations of monic polynomials such that the coefficients of each polynomial of the next generation coincide with the zeros of a polynomial of the current generation is introduced, and its relevance to the identification of endless sequences of new solvable many-body problems "of goldfish type" is demonstrated.

  4. Employment Relations in Maintained Secondary Schools: Research into Current Problems in Staff Management/Employment Relations and Consequent Training Needs of Headteachers in the Maintained Secondary Sector. Report to the Department of Education and Science.

    ERIC Educational Resources Information Center

    Lyons, Geoffrey; And Others

    This report describes and analyzes the principal findings of a research project into contemporary employment relations in maintained secondary schools in England and Wales. The report identifies problems and issues relating to staff management of current concern to school personnel and to local education authorities (LEAs), and further identifies…

  5. Contact Lenses for Vision Correction

    MedlinePlus

    ... Contact Lenses Colored Contact Lenses Contact Lenses for Vision Correction Written by: Kierstan Boyd Reviewed by: Brenda ... on the surface of the eye. They correct vision like eyeglasses do and are safe when used ...

  6. Contact binary stars

    NASA Astrophysics Data System (ADS)

    Mochnacki, S. W.

    1981-04-01

    Densities, corrected primary colors, minimum periods, inferred masses, luminosities, and specific angular momenta are computed from data on 37 W Ursae Majoris systems. A-type systems, having lower densities and angular momenta than the W-type systems, are shown to be evolved, and a new class of contact binary is identified, the OO Aquilae systems, whose members have evolved into contact. Evolutionary grids based on the contact condition agree with observation, except in that the evolved A-type systems have lost more angular momentum than predicted by gravitational radiation alone. This is accounted for by stellar wind magnetic braking, which is shown to be effective on a shorter time scale and to be important in other kinds of binaries containing a cool, tidally coupled component.

  7. Contact sensitization in children.

    PubMed

    Manzini, B M; Ferdani, G; Simonetti, V; Donini, M; Seidenari, S

    1998-01-01

    Our study concerns contact sensitization in children, the frequency of which is still debated in the literature, even though specific reports are increasing. During a 7 year period (1988-1994) 670 patients, 6 months to 12 years of age, were patch tested with the European standard series, integrated with 24 haptens, at the same concentrations as for adults. We observed positive results in 42% of our patients. Thimerosal, nickel sulfate, Kathon CG, fragrance mix, neomycin, wool alcohols, and ammoniated mercury induced most of the positive responses. The highest sensitization rate was found in children from 0 to 3 years of age. Comments on main positive haptens are reported. Seventy-seven percent of our sensitized patients were atopics, suggesting that atopy represents a predisposing factor for contact hypersensitivity. Patch testing represents a useful diagnostic procedure for the definition of childhood eczematous dermatitis and for the identification of agents inducing contact sensitization which is frequently associated with atopic dermatitis. PMID:9496796

  8. Aternating current photovoltaic building block

    DOEpatents

    Bower, Ward Issac; Thomas, Michael G.; Ruby, Douglas S.

    2004-06-15

    A modular apparatus for and method of alternating current photovoltaic power generation comprising via a photovoltaic module, generating power in the form of direct current; and converting direct current to alternating current and exporting power via one or more power conversion and transfer units attached to the module, each unit comprising a unitary housing extending a length or width of the module, which housing comprises: contact means for receiving direct current from the module; one or more direct current-to-alternating current inverters; an alternating current bus; and contact means for receiving alternating current from the one or more inverters.

  9. Single-contact tunneling thermometry

    DOEpatents

    Maksymovych, Petro

    2016-02-23

    A single-contact tunneling thermometry circuit includes a tunnel junction formed between two objects. Junction temperature gradient information is determined based on a mathematical relationship between a target alternating voltage applied across the junction and the junction temperature gradient. Total voltage measured across the junction indicates the magnitude of the target alternating voltage. A thermal gradient is induced across the junction. A reference thermovoltage is measured when zero alternating voltage is applied across the junction. An increasing alternating voltage is applied while measuring a thermovoltage component and a DC rectification voltage component created by the applied alternating voltage. The target alternating voltage is reached when the thermovoltage is nullified or doubled by the DC rectification voltage depending on the sign of the reference thermovoltage. Thermoelectric current and current measurements may be utilized in place of the thermovoltage and voltage measurements. The system may be automated with a feedback loop.

  10. Fractal prediction model of thermal contact conductance of rough surfaces

    NASA Astrophysics Data System (ADS)

    Ji, Cuicui; Zhu, Hua; Jiang, Wei

    2013-01-01

    The thermal contact conductance problem is an important issue in studying the heat transfer of engineering surfaces, which has been widely studied since last few decades, and for predicting which many theoretical models have been established. However, the models which have been existed are lack of objectivity due to that they are mostly studied based on the statistical methodology characterization for rough surfaces and simple partition for the deformation formats of contact asperity. In this paper, a fractal prediction model is developed for the thermal contact conductance between two rough surfaces based on the rough surface being described by three-dimensional Weierstrass and Mandelbrot fractal function and assuming that there are three kinds of asperity deformation modes: elastic, elastoplastic and fully plastic. Influences of contact load and contact area as well as fractal parameters and material properties on the thermal contact conductance are investigated by using the presented model. The investigation results show that the thermal contact conductance increases with the increasing of the contact load and contact area. The larger the fractal dimension, or the smaller the fractal roughness, the larger the thermal contact conductance is. The thermal contact conductance increases with decreasing the ratio of Young's elastic modulus to the microhardness. The results obtained indicate that the proposed model can effectively predict the thermal contact conductance at the interface, which provide certain reference to the further study on the issue of heat transfer between contact surfaces.

  11. Recent Trends in Occupational Contact Dermatitis.

    PubMed

    Wiszniewska, Marta; Walusiak-Skorupa, Jolanta

    2015-07-01

    Occupational contact dermatitis (OCD) remains prevalent among workers and impacts quality of life and workability. The purpose of this review is to summarize the recent advances in occupational contact dermatitis as well as potential hazardous agents in the workplaces causing OCD. The review covers new developments in the epidemiology, etiology, diagnosis, and management of occupational contact dermatitis. This article also provides updated information on the prevalence of work-related skin symptoms and on new contact allergens among working population. It is emphasized that in the context of prevention of OCD, special attention should be focused on the identified high-risk occupational groups, especially healthcare workers and hairdressers starting with the apprentices. Current approaches include working out the standards and guidelines to improve the education, knowledge, diagnosis, and management of OCD based on a multidisciplinary team of medical specialists and an employer. PMID:26143395

  12. Thermal contact conductance for cylindrical and spherical contacts

    NASA Astrophysics Data System (ADS)

    Sunil Kumar, S.; Abilash, P. M.; Ramamurthi, K.

    A prediction methodology based on Monte-Carlo simulation model, developed for flat conforming surfaces in contact, is modified and extended to predict contact conductance between curvilinear surfaces like cylinders and spheres. Experiments are also conducted in vacuum for the measurement of contact conductance between stainless steel and aluminium cylindrical contacts and stainless steel spherical contacts over a range of contact pressures. The contact conductance between cylindrical and spherical bodies is, in general, about an order of magnitude lower than for flat surfaces in contact. Increase of surface roughness and decrease in contact pressure lowers the contact conductance. However, the influence of these parameters is larger than those obtained for flat surfaces. The prediction for different parametric conditions agree closely with those measured in the experiments.

  13. Intermittent contact hydration scanning probe microscopy

    NASA Astrophysics Data System (ADS)

    Aloisi, G.; Bacci, F.; Carlà, M.; Dolci, D.

    2010-07-01

    Hydration scanning probe microscopy is a technique similar to scanning tunneling microscopy, in which the probe current, sustained by the slight surface conduction of a thin hydration layer covering an insulating support surface, is essentially electrochemical in nature instead of electronic tunneling. Such a technique allows the imaging of a great variety of samples, including insulators, provided that they are hydrophilic, as well as the study of molecular samples of biological interest (such as DNA) fixed on a suitable supporting surface. The main problem to obtain stable and reproducible images comes from the very critical determination of the operating conditions under which the probe-hydration layer interaction does not lead to the formation of a relatively large water meniscus. It has been suggested that this issue can be removed by adding a high frequency oscillation to the probe movement, as in tapping atomic force microscopy. Meniscus formation and breakup have been investigated in order to determine the best values for the amplitude and the frequency of the oscillation. Results obtained in this mode are discussed in comparison with the usual continuous contact mode.

  14. Thermal Contact Conductance

    NASA Technical Reports Server (NTRS)

    Salerno, Louis J.; Kittel, Peter

    1997-01-01

    The performance of cryogenic instruments is often a function of their operating temperature. Thus, designers of cryogenic instruments often are required to predict the operating temperature of each instrument they design. This requires accurate thermal models of cryogenic components which include the properties of the materials and assembly techniques used. When components are bolted or otherwise pressed together, a knowledge of the thermal performance of such joints are also needed. In some cases, the temperature drop across these joints represents a significant fraction of the total temperature difference between the instrument and its cooler. While extensive databases exist on the thermal properties of bulk materials, similar databases for pressed contacts do not. This has often lead to instrument designs that avoid pressed contacts or to the over-design of such joints at unnecessary expense. Although many people have made measurements of contact conductances at cryogenic temperatures, this data is often very narrow in scope and even more often it has not been published in an easily retrievable fashion, if published at all. This paper presents a summary of the limited pressed contact data available in the literature.

  15. Compact contacting device

    NASA Technical Reports Server (NTRS)

    Acharya, Arun (Inventor); Gottzmann, Christian F. (Inventor); Lockett, Michael J. (Inventor); Schneider, James S. (Inventor); Victor, Richard A. (Inventor); Zawierucha, Robert (Inventor)

    1994-01-01

    An apparatus comprising a rotatable mass of structured packing for mass or heat transfer between two contacting fluids of different densities wherein the packing mass is made up of corrugated sheets of involute shape relative to the axis of the packing mass and form a logarithmic spiral curved counter to the direction of rotation.

  16. Religious Allergic Contact Dermatitis.

    PubMed

    Goldenberg, Alina; Matiz, Catalina; Eichenfield, Lawrence F

    2015-01-01

    Henna, derived from a combination of natural leaves and coloring additives, is a common decorative dye traditionally used in many Islamic religious celebrations. Para-phenylenediamine (PPD), a major component of black henna tattoo, is a strong sensitizer and common allergen. We report a case of severe connubial allergic contact dermatitis after black henna heterotransfer in a girl. PMID:25968562

  17. Have Confidence in Contact

    ERIC Educational Resources Information Center

    Crisp, Richard J.; Turner, Rhiannon N.

    2010-01-01

    In an article in the May-June 2009 "American Psychologist," we discussed a new approach to reducing prejudice and encouraging more positive intergroup relations (Crisp & Turner, 2009). We named the approach imagined intergroup contact and defined it as "the mental simulation of a social interaction with a member or members of an outgroup category"…

  18. Why is adolescence a key period of alcohol initiation and who is prone to develop long-term problem use?: A review of current available data

    PubMed Central

    Petit, Géraldine; Kornreich, Charles; Verbanck, Paul; Cimochowska, Agnieska; Campanella, Salvatore

    2013-01-01

    Background Early adolescence is a key developmental period for the initiation of alcohol use, and consumption among adolescents is characterized by drinking in high quantities. At the same time, adolescence is characterized by rapid biological transformations including dramatic changes in the brain, particularly in the prefrontal cortex and the mesocorticolimbic dopamine system. Methods This article begins with an overview of the unique neural and behavioural characteristics of adolescent development that predispose these individuals to seek rewards and take risks such as initiation of drinking and high levels of alcohol intake. The authors then outline important factors associated with an increased risk for developing alcohol problems in later adolescence and young adulthood. Thereafter they address causality and the complex interplay of risk factors that lead to the development of alcohol use problems in late adolescence and young adults. Conclusions A few recommendations for the prevention of underage drinking are presented. PMID:24693359

  19. Development of high temperature stable Ohmic and Schottky contacts on n-gallium nitride

    NASA Astrophysics Data System (ADS)

    Khanna, Rohit

    compounds. The barrier height obtained on n GaN was ˜0-5-0.6 eV which was low compared to those obtained by Pt or Ni. This barrier height is too low for use as a gate contact and they can only have limited use, perhaps, in gas sensors where large leakage current can be tolerated in exchange for better thermal reliability. AlGaN/GaN High Electron Mobility Transistors (HEMTs) were fabricated with Ti/Al/TiB2/Ti/Au source/drain ohmic contacts and a variety of gate metal schemes (Pt/Au, Ni/Au, Pt/TiB2/Au or Ni/TiB 2/Au) and were subjected to long-term annealing at 350°C. By comparison with companion devices with conventional Ti/Al/Pt/Au ohmic contacts and Pt/Au gate contacts, the HEMTs with boride-based ohmic metal and either Pt/Au, Ni/Au or Ni/TiB2/Au gate metal showed superior stability of both source-drain current and transconductance after 25 days aging at 350°C. The need for sputter deposition of the borides causes' problem in achieving significantly lower specific contact resistance than with conventional schemes deposited using e-beam evaporation. The borides also seem to be, in general, good getters for oxygen leading to sheet resistivity issues. Ir/Au Schottky contacts and Ti/Al/Ir/Au ohmic contacts on n-type GaN were investigated as a function of annealing temperature and compared to their more common Ni-based counterparts. The Ir/Au ohmic contacts on n-type GaN with n˜1017 cm-3 exhibited barrier heights of 0.55 eV after annealing at 700°C and displayed less intermixing of the contact metals compared to Ni/Au. A minimum specific contact resistance of 1.6 x 10-6 O.cm2 was obtained for the ohmic contacts on n-type GaN with n˜1018 cm-3 after annealing at 900°C. The measurement temperature dependence of contact resistance was similar for both Ti/Al/Ir/Au and Ti/Al/Ni/Au, suggesting the same transport mechanism was present in both types of contacts. The Ir-based ohmic contacts displayed superior thermal aging characteristics at 350°C. Auger Electron Spectroscopy

  20. October 29-31, 2003 geomagnetic storm: geomagnetically induced currents and their relation to problems in the Swedish high-voltage power transmission system

    NASA Astrophysics Data System (ADS)

    Pulkkinen, A. A.; Lindahl, S.; Viljanen, A.; Pirjola, R.

    2004-12-01

    In October 30, 2003, an ongoing geomagnetic superstorm knocked down a part of the high-voltage power transmission system in southern Sweden operated by the Sydkraft company. The blackout lasted for an hour and left about 50000 people without electricity. The incident was probably the most severe GIC failure observed since the well-known March 1989 Québec blackout and thus the problems in a Swedish system deserve a closer look. The geophysical background and the impacts on the Swedish high-voltage power transmission system of the October 29-31, 2003 geomagnetic storm are described in the study at hand. It was seen that athough no serious problems in North-America have been reported, the "three-phase" storm produced exceptionally large geomagnetic activity at the Fennoscandian auroral region. It was also seen that GIC modeled for southern Sweden region using very simplistic methods were able to explain the times of the failures in the Swedish system thus confirming the sources of experienced problems and adding also GIC to the long list of causes of technological impacts of the storm. Though the great diversity of the GIC drivers are addresses in the study, the problems in operating the Swedish system during the exceptionally intense storm of October 29-31, 2003 are attributed geophysically to substorms, SSCs and enhanced ionospheric convection all of which were creating large and complex geoelectric fields capable of driving large GIC. Based on the basic two-fold nature of the failure-related geoelectric field characteristics, a semi-deterministic approach for forecasting GIC-related geomagnetic activity in which average overall activity is supplemented with statistical estimations of the amplitudes of GIC fluctuations is suggested.

  1. PREFACE: Non-contact AFM Non-contact AFM

    NASA Astrophysics Data System (ADS)

    Giessibl, Franz J.; Morita, Seizo

    2012-02-01

    This special issue is focussed on high resolution non-contact atomic force microscopy (AFM). Non-contact atomic force microscopy was established approximately 15 years ago as a tool to image conducting and insulating surfaces with atomic resolution. Since 1998, an annual international conference has taken place, and although the proceedings of these conferences are a useful source of information, several key developments warrant devoting a special issue to this subject. In the theoretic field, the possibility of supplementing established techniques such as scanning tunneling microscopy (STM) and Kelvin probe microscopy with atomically resolved force micrsoscopy poses many challenges in the calculation of contrast and contrast reversal. The surface science of insulators, self-assembled monolayers and adsorbates on insulators is a fruitful field for the application of non-contact AFM: several articles in this issue are devoted to these subjects. Atomic imaging and manipulation have been pioneered using STM, but because AFM allows the measurement of forces, AFM has had a profound impact in this field as well. Three-dimensional force spectroscopy has allowed many important insights into surface science. In this issue a combined 3D tunneling and force microscopy is introduced. Non-contact AFM typically uses frequency modulation to measure force gradients and was initially used mainly in a vacuum. As can be seen in this issue, frequency modulation is now also used in ambient conditions, allowing better spatial and force resolution. We thank all of the contributors for their time and efforts in making this special issue possible. We are also very grateful to the staff of IOP Publishing for handling the administrative aspects and for steering the refereeing process. Non-contact AFM contents Relation between the chemical force and the tunnelling current in atomic point contacts: a simple model Pavel Jelínek, Martin Ondrácek and Fernando Flores Theoretical simulation of

  2. Technology Transfer: A Contact Sport

    NASA Technical Reports Server (NTRS)

    Paynter, Nina P.

    1995-01-01

    Technology transfer is a dynamic process, involving dynamic people as the bridge between NASA Langley Research Center and the outside world. This bridge, for nonaerospace applications, is known as the Technology Applications Group. The introduction of new innovations and expertise where they are needed occurs through a 'push' and 'pull' process. A 'push' occurs when a new technology is first developed with high commercial potential and then a company is found to licence or further develop the technology. The 'pull' process occurs through problem statements. A company or group will submit a written statement of what they need and the shortcomings of commercially available technology. The Technology Transfer Team (T3) reviews these problem statements and decides where NASA LaRC can offer assistance. A researcher or group of researchers are then identified who can help solve the problem and they are put in contact with the company. Depending upon the situation in either method, a Space Act Agreement (SAA), or outline of the responsibilities for each party, is developed.

  3. Exploring the Nature of Contact Freezing

    NASA Astrophysics Data System (ADS)

    Kiselev, A. A.; Hoffmann, N.; Duft, D.; Leisner, T.

    2012-12-01

    The freezing of supercooled water droplets upon contact with aerosol particles (contact nucleation of ice) is the least understood mechanism of ice formation in atmospheric clouds. Although experimental evidences suggest that some aerosols can be better IN in the contact than in the immersion mode (that is, triggering ice nucleation at higher temperature), no final explanation of this phenomena currently exists. On the other hand, the contact freezing is believed to be responsible for the enhanced rate of secondary ice formation occasionally observed in LIDAR measurements in the cold mixed phase clouds. Recently we have been able to show that the freezing of supercooled droplets electrodynamically levitated in the laminar flow containing mineral dust particles (kaolinite) is a process solely governed by a rate of collisions between the supercooled droplet and the aerosol particles. We have shown that the probability of droplet freezing on a single contact with aerosol particle may differ over an order of magnitude for kaolinite particles having different genesis and morphology. In this presentation we extend the study of contact nucleation of ice and compare the IN efficiency measured for DMA-selected kaolinite, illite and hematite particles. We show that the freezing probability increases towards unity as the temperature decreases and discuss the functional form of this temperature dependence. We explore the size dependence of the contact freezing probability and show that it scales with the surface area of the particles, thus resembling the immersion freezing behavior. However, for all minerals investigated so far, the contact freezing has been shown to dominate over immersion freezing on the short experimental time scales. Finally, based on the combined ESEM and electron microprobe analysis, we discuss the significance of particle morphology and variability of chemical composition on its IN efficiency in contact mode.

  4. Contact dermatitis from a prosthesis.

    PubMed

    Munoz, Carla A; Gaspari, Anthony; Goldner, Ronald

    2008-01-01

    Patients wearing a prosthesis face a wide variety of medical problems. Skin complications have long been recognized, but their prevalence is still unknown. The most frequently reported disorders are allergic contact dermatitis (ACD), acroangiodermatitis, epidermoid cysts, epidermal hyperplasia, follicular hyperkeratosis, verrucous hyperplasia, bullous diseases, hyperhidrosis, infections, malignancies, and ulcerations. Contact dermatitis represents one-third of the dermatoses in amputees wearing prostheses. All patients who are suspected of having ACD should be patch tested with standard allergen series as well as materials from the patient's own prosthesis, topical medicaments, moisturizers, and cosmetics. We report a patient with an ACD to mixed dialkyl thiourea present in the rubber parts of his below-the-knee prosthesis. Thiourea derivates are used as accelerators in the manufacture of chloroprene rubber and as fixatives in photography and photocopy paper. Allergy to thiourea is relatively uncommon; different studies have shown a prevalence of 0.7% up to 2.4% in patch-tested patients. Thiourea derivates are often the allergic sources in ACD involving high-grade rubber products made of neoprene such as diving suits, protective goggles, knee braces, and continuous positive airway pressure masks. They are also present in the rubber material of prostheses, as in the case of our patient. PMID:18413115

  5. A 3D Contact Smoothing Method

    SciTech Connect

    Puso, M A; Laursen, T A

    2002-05-02

    Smoothing of contact surfaces can be used to eliminate the chatter typically seen with node on facet contact and give a better representation of the actual contact surface. The latter affect is well demonstrated for problems with interference fits. In this work we present two methods for the smoothing of contact surfaces for 3D finite element contact. In the first method, we employ Gregory patches to smooth the faceted surface in a node on facet implementation. In the second method, we employ a Bezier interpolation of the faceted surface in a mortar method implementation of contact. As is well known, node on facet approaches can exhibit locking due to the failure of the Babuska-Brezzi condition and in some instances fail the patch test. The mortar method implementation is stable and provides optimal convergence in the energy of error. In the this work we demonstrate the superiority of the smoothed versus the non-smoothed node on facet implementations. We also show where the node on facet method fails and some results from the smoothed mortar method implementation.

  6. Low contact resistance in epitaxial graphene devices for quantum metrology

    SciTech Connect

    Yager, Tom E-mail: ywpark@snu.ac.kr; Lartsev, Arseniy; Lara-Avila, Samuel; Kubatkin, Sergey; Cedergren, Karin; Yakimova, Rositsa; Panchal, Vishal; Kazakova, Olga; Tzalenchuk, Alexander; Kim, Kyung Ho; Park, Yung Woo E-mail: ywpark@snu.ac.kr

    2015-08-15

    We investigate Ti/Au contacts to monolayer epitaxial graphene on SiC (0001) for applications in quantum resistance metrology. Using three-terminal measurements in the quantum Hall regime we observed variations in contact resistances ranging from a minimal value of 0.6 Ω up to 11 kΩ. We identify a major source of high-resistance contacts to be due bilayer graphene interruptions to the quantum Hall current, whilst discarding the effects of interface cleanliness and contact geometry for our fabricated devices. Moreover, we experimentally demonstrate methods to improve the reproducibility of low resistance contacts (<10 Ω) suitable for high precision quantum resistance metrology.

  7. Reported lifetime aberrant drug-taking behaviors are predictive of current substance use and mental health problems in primary care patients

    PubMed Central

    Fleming, Michael F.; Davis, James; Passik, Steven D.

    2009-01-01

    Background: The aim of this report is to determine the frequency of aberrant drug behaviors and their relationship substance abuse disorders in a large primary sample of patients receiving opioids for chronic pain. Methods: The data utilized for this report was obtained from 904 chronic pain patients receiving opioid therapy from their primary care physician. A questionnaire was developed based on 12 aberrant drug behaviors reported in the clinical literature. The diagnosis of a current substance use disorder was determined using DSM-IV criteria. Results: The average duration of chronic pain in the sample was 16 years, and for opioid therapy 6.4 years. 80.5% of the sample reported one or more lifetime aberrant drug behaviors. The most frequent behaviors reported included early refills (41.7%), increase dose without physician consent (35.7%) and felt intoxicated from opioids (32.2%). Only 1.1% of subjects with 1-3 aberrant behaviors (n=464, 51.2%) met DSM-IV criteria for current opioid dependence compared to 9.9% of patients with 4 or more behaviors (n=264, 29.3%). Persons with a positive urine toxicology tests for cocaine were 14 times more likely to report 4 or more behaviors than no behaviors (14.1% v.s.1.1%). A logistic model found that subjects who reported four or more aberrant behaviors were more likely to have a current substance use disorder (OR 10.14; 3.72, 27.64), a positive test for cocaine (OR 3.01; 1.74, 15.4), an ASI psychiatric composite score >0.5 (OR 2.38; 1.65, 3.44), male gender (OR 2.08: 1.48, 2.92) and older age (OR 0.69; 0.59, 0.81) compared to subjects with three or fewer behaviors. Pain levels, employment status and morphine equivalent dose do not enter the model. Conclusions: Patients who report 4 or more aberrant drug behaviors are associated with a current substance use disorder and illicit drug use, whereas subjects with up to 3 aberrant behaviors have a very low probability of a current substance abuse disorder. Four behaviors - over

  8. Inside the brachycephalic nose: intranasal mucosal contact points.

    PubMed

    Schuenemann, Riccarda; Oechtering, Gerhard U

    2014-01-01

    The purpose of this study was to evaluate the prevalence of intranasal mucosal contact points in brachycephalic and normocephalic dogs. In total, 82 brachycephalic dogs (42 pugs and 40 French bulldogs) were evaluated by rhinoscopy for their intranasal mucosal contact and 25 normocephalic dogs were evaluated as a control group. Of those, 162 brachycephalic nasal cavities were evaluable and 140 had contact between intranasal structures (87%). Intraconchal and septoconchal mucosal contact points were the most commonly detected sites of contact. French bulldogs had a significantly higher prevalence of mucosal contact and had 3 mean contact points compared with 1.7 mean contact points per nasal cavity in pugs. Septal deviations were present in 62% of brachycephalic dogs. In the control group, mucosal contact points were present in only 7 of 50 nasal cavities (14%), and septal deviations occurred in 16% of those cases. Contact point average was 0.1 in large and 0.3 in small normocephalic dogs. Intranasal mucosal contact was identified as a common and previously unreported problem in brachycephalic dogs. Numerous contact points reduce the lumen of the intranasal passageways and indicate potential intranasal obstruction. Affected dogs might benefit from removal of obstructing conchae, potentially using laser-assisted turbinectomy. PMID:24659729

  9. Computational Contact Formulations for Soft Body Adhesion

    NASA Astrophysics Data System (ADS)

    Sauer, Roger A.

    This article gives an overview of adhesive contact for soft bodies and focuses on a general computational framework that is suitable for treating a large class of adhesion problems. The contact formulation is based on a non-linear continuum approach that is capable of describing bodies down to length scales of several nanometers. Several finite element formulations are presented, that introduce various approximations in order to increase the computational efficiency. The approaches are illustrated by several examples throughout the text. These include carbon nanotube interaction, adhesion of spheres, nanoindentation, thin film peeling, gecko adhesion and self-cleaning surface mechanisms.

  10. Contact dermatitis: facts and controversies.

    PubMed

    Wolf, Ronni; Orion, Edith; Ruocco, Eleonora; Baroni, Adone; Ruocco, Vincenzo

    2013-01-01

    The history of contact dermatitis (CD) is inseparable from the history of the patch test, and the patch test is inseparable from the pioneer in the field, Josef Jadassohn (1860-1936). Despite the fact that we have been diagnosing, treating, and investigating the condition for more than 100 years, there are still many unsolved questions and controversies, which show no signs of coming to an end in the foreseeable future. This contribution reviews and highlights some of the disagreements and discrepancies associated with CD. For example: • What is the real sensitizer in balsam of Peru, one of the most common allergens, and what, if any, is the value of a low-balsam diet? • Is benzalkonium chloride, which has well-known and undisputed irritant properties, a contact allergen as well? • Is cocamidopropyl betaine (CABP) a common contact allergen and what is the actual sensitizer in CABP allergy the molecule itself, or impurities, or intermediaries in its synthesis? • How can the significant differences in the prevalence of sensitization of formaldehyde (FA, a common cause of contact allergy) between the United States (8%-9%) and Europe (2%-3%) be explained? • What is the relationship between formaldehyde releasers (FRs) allergy and an FA allergy? Should we recommend that FA-allergic patients also avoid FRs, and, if so, to what extent? • What is the true frequency of lanolin allergy? This issue remains enigmatic despite the expenditure of thousands of dollars and the innumerable hours spent investigating this subject. • What is the basis behind the so-called "lanolin paradox"? This label was coined in 1996 and is still a matter of controversy. • Is there such a thing as systemic CD from nickel, and, if so, to what extent? Is there a cross-reactivity or concomitant sensitization between nickel and cobalt?These are some of the controversial problems discussed. We have selected the ones that we consider to be of special interest and importance to the

  11. Contact dynamics math model

    NASA Technical Reports Server (NTRS)

    Glaese, John R.; Tobbe, Patrick A.

    1986-01-01

    The Space Station Mechanism Test Bed consists of a hydraulically driven, computer controlled six degree of freedom (DOF) motion system with which docking, berthing, and other mechanisms can be evaluated. Measured contact forces and moments are provided to the simulation host computer to enable representation of orbital contact dynamics. This report describes the development of a generalized math model which represents the relative motion between two rigid orbiting vehicles. The model allows motion in six DOF for each body, with no vehicle size limitation. The rotational and translational equations of motion are derived. The method used to transform the forces and moments from the sensor location to the vehicles' centers of mass is also explained. Two math models of docking mechanisms, a simple translational spring and the Remote Manipulator System end effector, are presented along with simulation results. The translational spring model is used in an attempt to verify the simulation with compensated hardware in the loop results.

  12. Simulating Contact Binaries

    NASA Astrophysics Data System (ADS)

    Kadam, Kundan; Clayton, Geoffrey C.; Frank, Juhan; Tohline, Joel E.; Staff, Jan E.; Motl, Patrick M.; Marcello, Dominic

    2014-06-01

    About one in every 150 stars is a contact binary system of WUMa type and it was thought for a long time that such a binary would naturally proceed towards merger, forming a single star. In September 2008 such a merger was observed in the eruption of a “red nova", V1309 Sco. We are developing a hydrodynamics simulation for contact binaries using Self Consistent Field (SCF) techniques, so that their formation, structural, and merger properties could be studied. This model can also be used to probe the stability criteria such as the large-scale equatorial circulations and the minimum mass ratio. We also plan to generate light curves from the simulation data in order to compare with the observed case of V1309 Sco. A comparison between observations and simulations will help us better understand the nova-like phenomena of stellar mergers.

  13. Magnetron Sputtered Gold Contacts on N-gaas

    NASA Technical Reports Server (NTRS)

    Buonaquisti, A. D.; Matson, R. J.; Russell, P. E.; Holloway, P. H.

    1984-01-01

    Direct current planar magnetron sputtering was used to deposit gold Schottky barrier electrical contacts on n-type GaAs of varying doping densities. The electrical character of the contact was determined from current voltage and electron beam induced voltage data. Without reducing the surface concentration of carbon and oxide, the contacts were found to be rectifying. There is evidence that energetic neutral particles reflected from the magnetron target strike the GaAs and cause interfacial damage similar to that observed for ion sputtering. Particle irradiation of the surface during contact deposition is discussed.

  14. Contact dermatitis in children

    PubMed Central

    2010-01-01

    Contact dermatitis in pediatric population is a common but (previously) under recognized disease. It is usually divided into the allergic and the irritant forms. The diagnosis is usually obtained with the patch test technique after conducting a thorough medical history and careful physical examination but patch testing in infants may be particularly difficult, and false-positive reactions may occur. This study also provides an overview of the most common allergens in pediatric population and discusses various therapeutic modalities. PMID:20205907

  15. Contact stress sensor

    DOEpatents

    Kotovsky, Jack

    2014-02-11

    A method for producing a contact stress sensor that includes one or more MEMS fabricated sensor elements, where each sensor element of includes a thin non-recessed portion, a recessed portion and a pressure sensitive element adjacent to the recessed portion. An electric circuit is connected to the pressure sensitive element. The circuit includes a pressure signal circuit element configured to provide a signal upon movement of the pressure sensitive element.

  16. Contact stress sensor

    DOEpatents

    Kotovsky, Jack

    2012-02-07

    A contact stress sensor includes one or more MEMS fabricated sensor elements, where each sensor element of includes a thin non-recessed portion, a recessed portion and a pressure sensitive element adjacent to the recessed portion. An electric circuit is connected to the pressure sensitive element. The circuit includes a thermal compensator and a pressure signal circuit element configured to provide a signal upon movement of the pressure sensitive element.

  17. English in Albania: Contact and Convergence.

    ERIC Educational Resources Information Center

    Dushku, Silvana

    1998-01-01

    Gives an overview of the current status and usage of English in Albania, outlining the sociolinguistic context in which changes in usage have taken place. Evidence is presented of increasing contact areas of English and standard Albanian under the new, post-communist sociopolitical and economic circumstances. Attention is drawn to need for more…

  18. The Induction of Mental and Contact Contamination

    ERIC Educational Resources Information Center

    Lee, Michelle; Shafran, Roz; Burgess, Charlotte; Carpenter, Jodi; Millard, Emma; Thorpe, Susan

    2013-01-01

    Background: Extreme fear of contamination within obsessive compulsive disorder (OCD) is traditionally conceptualised as a physical phenomenon. More recent research has supported the notion of "mental" contamination (MC) in which people feel contaminated in the absence of physical contact. The current research sought to determine whether feelings…

  19. Functional modular contact lens

    NASA Astrophysics Data System (ADS)

    Shum, Angela J.; Cowan, Melissa; Lähdesmäki, Ilkka; Lingley, Andrew; Otis, Brian; Parviz, Babak A.

    2009-08-01

    Tear fluid offers a potential route for non-invasive sensing of physiological parameters. Utilization of this potential depends on the ability to manufacture sensors that can be placed on the surface of the eye. A contact lens makes a natural platform for such sensors, but contact lens polymers present a challenge for sensor fabrication. This paper describes a microfabrication process for constructing sensors that can be integrated into the structure of a functional contact lens in the future. To demonstrate the capabilities of the process, an amperometric glucose sensor was fabricated on a polymer substrate. The sensor consists of platinum working and counter electrodes, as well as a region of indium-tin oxide (ITO) for glucose oxidase immobilization. An external silver-silver chloride electrode was used as the reference electrode during the characterization experiments. Sensor operation was validated by hydrogen peroxide measurements in the 10- 20 μM range and glucose measurements in the 0.125-20 mM range.

  20. Acrylate Systemic Contact Dermatitis.

    PubMed

    Sauder, Maxwell B; Pratt, Melanie D

    2015-01-01

    Acrylates, the 2012 American Contact Dermatitis Society allergen of the year, are found in a range of products including the absorbent materials within feminine hygiene pads. When fully polymerized, acrylates are nonimmunogenic; however, if not completely cured, the monomers can be potent allergens.A 28-year-old woman is presented, who had her teeth varnished with Isodan (Septodont, Saint-Maur-des-Fossés, France) containing HEMA (2-hydroxyethyl methacrylate) with no initial reaction. Approximately 1 month later, the patient developed a genital dermatitis secondary to her feminine hygiene pads. The initial reaction resolved, but 5 months later, the patient developed a systemic contact dermatitis after receiving a second varnishing.The patient was dramatically patch test positive to many acrylates. This case demonstrates a reaction to likely unpolymerized acrylates within a feminine hygiene pad, as well as broad cross-reactivity or cosensitivity to acrylates, and possibly a systemic contact dermatitis with systemic re-exposure to unpolymerized acrylates. PMID:26367207

  1. Pediatric contact dermatitis.

    PubMed

    Sharma, Vinod K; Asati, Dinesh P

    2010-01-01

    Allergic contact dermatitis (ACD) in children, until recently, was considered rare. ACD was considered as a disorder of the adult population and children were thought to be spared due to a lack of exposure to potential allergens and an immature immune system. Prevalence of ACD to even the most common allergens in children, like poison ivy and parthenium, is relatively rare as compared to adults. However, there is now growing evidence of contact sensitization of the pediatric population, and it begins right from early childhood, including 1-week-old neonates. Vaccinations, piercing, topical medicaments and cosmetics in younger patients are potential exposures for sensitization. Nickel is the most common sensitizer in almost all studies pertaining to pediatric contact dermatitis. Other common allergens reported are cobalt, fragrance mix, rubber, lanolin, thiomersol, neomycin, gold, mercapto mix, balsum of Peru and colophony. Different factors like age, sex, atopy, social and cultural practices, habit of parents and caregivers and geographic changes affect the patterns of ACD and their variable clinical presentation. Patch testing should be considered not only in children with lesions of a morphology suggestive of ACD, but in any child with dermatitis that is difficult to control. PMID:20826990

  2. Dual contact pogo pin assembly

    DOEpatents

    Hatch, Stephen McGarry

    2016-06-21

    A contact assembly includes a base and a pair of electrical contacts supported by the base. A first end of the first electrical contact corresponds to a first end of the base and is configured to engage a first external conductive circuit element. A first end of the second electrical contact also corresponds to the first end of the base and is configured to engage a second external conductive circuit element. The first contact and the second contact are electrically isolated from one another and configured to compress when engaging an external connector element. The base includes an aperture positioned on a second end of the base outboard of a second end of the first and second electrical contacts. The aperture presents a narrowing shape with a wide mouth distal the electrical contacts and a narrow internal through-hole proximate the electrical contacts.

  3. Dual contact pogo pin assembly

    DOEpatents

    Hatch, Stephen McGarry

    2015-01-20

    A contact assembly includes a base and a pair of electrical contacts supported by the base. A first end of the first electrical contact corresponds to a first end of the base and is configured to engage a first external conductive circuit element. A first end of the second electrical contact also corresponds to the first end of the base and is configured to engage a second external conductive circuit element. The first contact and the second contact are electrically isolated from one another and configured to compress when engaging an external connector element. The base includes an aperture positioned on a second end of the base outboard of a second end of the first and second electrical contacts. The aperture presents a narrowing shape with a wide mouth distal the electrical contacts and a narrow internal through-hole proximate the electrical contacts.

  4. Adhesion effects in contact interaction of solids

    NASA Astrophysics Data System (ADS)

    Goryacheva, Irina; Makhovskaya, Yulya

    2008-01-01

    An approach to solving problems of the interaction of axisymmetric elastic bodies in the presence of adhesion is developed. The different natures of adhesion, i.e. capillary adhesion, or molecular adhesion described by the Lennard-Jones potential are examined. The effect of additional loading of the interacting bodies outside the contact zone is also investigated. The approach is based on the representation of the pressure outside the contact zone arising from adhesion by a step function. The analytical solution is obtained and is used to analyze the influence of the form of the adhesion interaction potential, of the surface energy of interacting bodies or the films covering the bodies, their shapes (parabolic, higher power exponential function), volume of liquid in the meniscus, density of contact spots, of elastic modulus and the Poisson ratio on the characteristics of the interaction of the bodies in the presence of adhesion. To cite this article: I. Goryacheva, Y. Makhovskaya, C. R. Mecanique 336 (2008).

  5. Atomistic Simulation of Single Asperity Contact

    NASA Astrophysics Data System (ADS)

    Philip; Kromer; Marder, Michael

    2003-03-01

    In the standard (Bowden and Tabor) model of friction, the macroscopic behavior of sliding results from the deformation of microscopic asperities in contact. A recent idea instead extracts macroscopic friction from the aggregate behavior of traveling, self-healing interfacial cracks: certain families of cracks are found to be mathematically forbidden, and the envelope of allowed cracks dictates the familiar Coulomb law of friction. To explore the connection between the new and traditional pictures of friction, we conducted molecular dynamics (MD) simulations of single-asperity contact subjected to an oscillatory sliding force -- a geometry important for the problem of fretting (damage due to small-scale vibratory contact). Our simulations reveal the importance of traveling interface cracks to the dynamics of slip at the interface, and illuminate the dynamics of crack initiation and suppression.

  6. Measuring the specific contact resistance of contacts to semiconductor nanowires

    NASA Astrophysics Data System (ADS)

    Mohney, S. E.; Wang, Y.; Cabassi, M. A.; Lew, K. K.; Dey, S.; Redwing, J. M.; Mayer, T. S.

    2005-02-01

    Ohmic contacts to semiconductor nanowires are essential components of many new nanoscale electronic devices. Equations for extracting specific contact resistance (or contact resistivity) from several different test structures have been developed by modeling the metal/semiconductor contact as a transmission line, leading to the development of equations analogous to those used for planar contacts. The advantages and disadvantages of various test structures are discussed. To fabricate test structures using a convenient four-point approach, silicon nanowires have been aligned using field-assisted assembly and contacts fabricated. Finally, specific contact resistances near 5 × 10 -4 Ω cm 2 have been measured for Ti/Au contacts to p-type Si nanowires with diameters of 78 and 104 nm.

  7. Computing an upper bound on contact stress with surrogate duality

    NASA Astrophysics Data System (ADS)

    Xuan, Zhaocheng; Papadopoulos, Panayiotis

    2016-07-01

    We present a method for computing an upper bound on the contact stress of elastic bodies. The continuum model of elastic bodies with contact is first modeled as a constrained optimization problem by using finite elements. An explicit formulation of the total contact force, a fraction function with the numerator as a linear function and the denominator as a quadratic convex function, is derived with only the normalized nodal contact forces as the constrained variables in a standard simplex. Then two bounds are obtained for the sum of the nodal contact forces. The first is an explicit formulation of matrices of the finite element model, derived by maximizing the fraction function under the constraint that the sum of the normalized nodal contact forces is one. The second bound is solved by first maximizing the fraction function subject to the standard simplex and then using Dinkelbach's algorithm for fractional programming to find the maximum—since the fraction function is pseudo concave in a neighborhood of the solution. These two bounds are solved with the problem dimensions being only the number of contact nodes or node pairs, which are much smaller than the dimension for the original problem, namely, the number of degrees of freedom. Next, a scheme for constructing an upper bound on the contact stress is proposed that uses the bounds on the sum of the nodal contact forces obtained on a fine finite element mesh and the nodal contact forces obtained on a coarse finite element mesh, which are problems that can be solved at a lower computational cost. Finally, the proposed method is verified through some examples concerning both frictionless and frictional contact to demonstrate the method's feasibility, efficiency, and robustness.

  8. Computing an upper bound on contact stress with surrogate duality

    NASA Astrophysics Data System (ADS)

    Xuan, Zhaocheng; Papadopoulos, Panayiotis

    2016-04-01

    We present a method for computing an upper bound on the contact stress of elastic bodies. The continuum model of elastic bodies with contact is first modeled as a constrained optimization problem by using finite elements. An explicit formulation of the total contact force, a fraction function with the numerator as a linear function and the denominator as a quadratic convex function, is derived with only the normalized nodal contact forces as the constrained variables in a standard simplex. Then two bounds are obtained for the sum of the nodal contact forces. The first is an explicit formulation of matrices of the finite element model, derived by maximizing the fraction function under the constraint that the sum of the normalized nodal contact forces is one. The second bound is solved by first maximizing the fraction function subject to the standard simplex and then using Dinkelbach's algorithm for fractional programming to find the maximum—since the fraction function is pseudo concave in a neighborhood of the solution. These two bounds are solved with the problem dimensions being only the number of contact nodes or node pairs, which are much smaller than the dimension for the original problem, namely, the number of degrees of freedom. Next, a scheme for constructing an upper bound on the contact stress is proposed that uses the bounds on the sum of the nodal contact forces obtained on a fine finite element mesh and the nodal contact forces obtained on a coarse finite element mesh, which are problems that can be solved at a lower computational cost. Finally, the proposed method is verified through some examples concerning both frictionless and frictional contact to demonstrate the method's feasibility, efficiency, and robustness.

  9. A Direct analysis of elastic contact using super elements

    NASA Astrophysics Data System (ADS)

    Pedersen, Pauli

    2006-02-01

    Solutions to contact problems are important in mechanical as well as in civil engineering, and even for the most simple problems there is still a need for research results. In the present paper we suggest an alternative finite element procedure and by examples show the need for more knowledge related to the compliance of contact surfaces. The most simple solutions are named Hertz solutions from 1882, and we use some of these solutions for comparison with our finite element results. As a function of the total contact force we find the size of the contact area, the distribution of the contact pressure, and the contact compliance. In models of finite size the compliance depends on the flexibility of the total model, including the boundary condition of the model, and therefore disagreement with the locally based analytical models is expected and found. With computational contact mechanics we can solve more advanced contact problems and treat models that are closer to physical reality. The finite element method is widely used and solutions are obtained by incrementation and/or iteration for these non-linear problems with unknown boundary conditions. Still with these advanced tools the solution is difficult because of extreme sensitivity. Here we present a direct analysis of elastic contact without incrementation and iteration, and the procedure is based on a finite element super element technique. This means that the contacting bodies can be analyzed independently, and are only coupled through a direct analysis with low order super element stiffness matrices. The examples of the present paper are restricted to axisymmetric problems with isotropic, elastic materials and excluding friction. Direct extensions to cases of non-isotropy, including laminates, and to plane and general 3D models are possible.

  10. The effect of a temperature-dependent contact parameter on Mars cloud formation

    NASA Astrophysics Data System (ADS)

    Atsuki Urata, Richard; Hollingsworth, Jeffery; Kahre, Melinda

    2015-11-01

    Modeling the current water cycle on Mars is a complex problem that at present remains a scientific challenge. The water cycle is highly coupled to atmospheric temperature, dust, surface ice temperature, atmospheric transport and mixing (i.e. planetary boundary layer (PBL) processes, and radiation, just to name a few. One of the main features of Mars' water cycle is the formation of the aphelion cloud belt. Clouds are formed at altitude (10-40 km) within the subtropics during the aphelion season (Ls=60°-120°). In general the aphelion cloud belt forms at higher altitudes compared to the polar and high-latitude clouds, and therefore at colder temperatures (180 K and below). Laboratory experiments of nucleation under cold temperatures indicate that nucleation becomes more difficult at and below 180 K than expected. This can be modeled by using a temperature-dependent contact parameter, m(T). In this study we use the NASA Ames Mars Global Circulation Model (Mars GCM) to compare the constant contact parameter with the temperature-dependent contact parameterization described by Iraci et al. (2010). The simulations demonstrate that the contact parameter has a significant affect on the opacity of the aphelion clouds, as well as the clouds that form at the edge of the seasonal CO2 ice caps. Both types of clouds tend to form near 180 K, supporting the importance of a temperature-dependent contact parameter.

  11. Energy flux method for inspection of contact and VIA layer reticles

    NASA Astrophysics Data System (ADS)

    Garcia, Hector I.; Volk, William W.; Xiong, Yalin; Watson, Sterling G.; Yu, Zongchang; Guo, Zhian; Wang, Lantian

    2003-05-01

    Contacts and VIAs are features whose integrity are very susceptible to reticle CD defects or in general, to defects that produce a change of total energy (flux) projected through the reticle. As lithography is extended beyond the 130nm node, the problem becomes more critical. Detecting and analyzing photomask critical dimension (CD) errors and semitransparent defects is vital for qualifying reticles to enable high IC wafer yield for the 90nm node. The current state of the art inspection methods are unable to meet the industry requirements for contact and via features. Using the TeraStarTM pattern inspection system's image computer platform, a new algorithm, TeraFluxTM, has been implemented and tested for the inspection of small 'closed' features. The algorithm compares the transmitted energy flux difference between a test contact (or a group of contacts) and a reference image for small closed features, such as, contacts, trenches, and cells on chrome and half-tone reticles. The algorithm is applicable to both clear and dark field reticles. Sensitivity characterization tests show that the new algorithm provides CD error detection to 6% energy flux variation with low false defect counts. We performed experiments to correlate the sensitivity performance of the new algorithm with wafer printability results. The results will be presented together with results of inspections results of programmed defect plates and production reticles.

  12. Current Therapeutics, Their Problems, and Sulfur-Containing-Amino-Acid Metabolism as a Novel Target against Infections by “Amitochondriate” Protozoan Parasites

    PubMed Central

    Ali, Vahab; Nozaki, Tomoyoshi

    2007-01-01

    The “amitochondriate” protozoan parasites of humans Entamoeba histolytica, Giardia intestinalis, and Trichomonas vaginalis share many biochemical features, e.g., energy and amino acid metabolism, a spectrum of drugs for their treatment, and the occurrence of drug resistance. These parasites possess metabolic pathways that are divergent from those of their mammalian hosts and are often considered to be good targets for drug development. Sulfur-containing-amino-acid metabolism represents one such divergent metabolic pathway, namely, the cysteine biosynthetic pathway and methionine γ-lyase-mediated catabolism of sulfur-containing amino acids, which are present in T. vaginalis and E. histolytica but absent in G. intestinalis. These pathways are potentially exploitable for development of drugs against amoebiasis and trichomoniasis. For instance, l-trifluoromethionine, which is catalyzed by methionine γ-lyase and produces a toxic product, is effective against T. vaginalis and E. histolytica parasites in vitro and in vivo and may represent a good lead compound. In this review, we summarize the biology of these microaerophilic parasites, their clinical manifestation and epidemiology of disease, chemotherapeutics, the modes of action of representative drugs, and problems related to these drugs, including drug resistance. We further discuss our approach to exploit unique sulfur-containing-amino-acid metabolism, focusing on development of drugs against E. histolytica. PMID:17223627

  13. Contact resistivities of metal-insulator-semiconductor contacts and metal-semiconductor contacts

    NASA Astrophysics Data System (ADS)

    Yu, Hao; Schaekers, Marc; Barla, Kathy; Horiguchi, Naoto; Collaert, Nadine; Thean, Aaron Voon-Yew; De Meyer, Kristin

    2016-04-01

    Applying simulations and experiments, this paper systematically compares contact resistivities (ρc) of metal-insulator-semiconductor (MIS) contacts and metal-semiconductor (MS) contacts with various semiconductor doping concentrations (Nd). Compared with the MS contacts, the MIS contacts with the low Schottky barrier height are more beneficial for ρc on semiconductors with low Nd, but this benefit diminishes gradually when Nd increases. With high Nd, we find that even an "ideal" MIS contact with optimized parameters cannot outperform the MS contact. As a result, the MIS contacts mainly apply to devices that use relatively low doped semiconductors, while we need to focus on the MS contacts to meet the sub-1 × 10-8 Ω cm2 ρc requirement for future Complementary Metal-Oxide-Semiconductor (CMOS) technology.

  14. Contact dermatitis in hairdressers.

    PubMed

    Nethercott, J R; MacPherson, M; Choi, B C; Nixon, P

    1986-02-01

    18 cases of hand dermatitis in hairdressers seen over a 5-year period are reviewed. The diagnoses in these patients are discussed with reference to other studies of hand dermatitis in hairdressers. Contact allergy due to paraphenylenediamine and related hair dyes was the presenting complaint in younger hairdressers, while formaldehyde allergy occurred in those who were older. The prognosis in the former group of workers with respect to continued employment in the trade tended to be poorer than the latter. Follow-up revealed that hand dermatitis often resulted in the worker not continuing to work in the hairdressing trade. PMID:2940055

  15. Adhesive Contact Sweeper

    NASA Technical Reports Server (NTRS)

    Patterson, Jonathan D.

    1993-01-01

    Adhesive contact sweeper removes hair and particles vacuum cleaner leaves behind, without stirring up dust. Also cleans loose rugs. Sweeper holds commercially available spools of inverted adhesive tape. Suitable for use in environments in which air kept free of dust; optics laboratories, computer rooms, and areas inhabited by people allergic to dust. For carpets, best used in tandem with vacuum cleaner; first pass with vacuum cleaner removes coarse particles, and second pass with sweeper extracts fine particles. This practice extends useful life of adhesive spools.

  16. Contact dermatitis to methylisothiazolinone*

    PubMed Central

    Scherrer, Maria Antonieta Rios; Rocha, Vanessa Barreto; Andrade, Ana Regina Coelho

    2015-01-01

    Methylisothiazolinone (MI) is a preservative found in cosmetic and industrial products. Contact dermatitis caused by either methylchloroisothiazolinone/methylisothiazolinone (MCI/MI or Kathon CG) or MI has shown increasing frequency. The latter is preferably detected through epicutaneous testing with aqueous MI 2000 ppm, which is not included in the Brazilian standard tray. We describe a series of 23 patients tested using it and our standard tray. A case with negative reaction to MCI/MI and positive to MI is emphasized. PMID:26734880

  17. Rubella contact tracing associated with air travel.

    PubMed

    Kim, Curi; Chavez, Pollyanna; Pierce, Abbi; Murray, Andrew; Sander, Molly; Kenyon, Cynthia; Sharangpani, Ruta; Abernathy, Emily; Icenogle, Joseph; Kutty, Preeta K; Redd, Susan B; Gallagher, Kathleen; Neatherlin, John; Marienau, Karen

    2012-01-01

    This report reviews U.S. guidelines for the identification of persons exposed to rubella during air travel. In response to an individual with rubella who traveled on multiple flights, CDC conducted an airline contact investigation that was expanded beyond customary protocol to assess if current operating procedures are adequate. Of 250 potentially exposed airline passengers, 215 (86%) were contacted and none developed a rubella-like rash, arguing against the need to notify passengers beyond the standard protocol in most cases. PMID:22212199

  18. National directory of space grant contacts

    NASA Technical Reports Server (NTRS)

    1995-01-01

    In this directory of space grant contacts of the NASA Space Grant College and Fellowship Program a listing of participating universities and other institutions are shown from all 50 states and from the District of Columbia and Puerto Rico. These 52 Space Grant State consortia currently consist of 395 institutions of higher learning, 66 industry affiliates, 26 state/local government offices, 40 nonprofit organizations, and 25 other educational entities. This directory is organized alphabetically by state and the contacts, addresses, phone numbers, and internet email addresses (where available) are included.

  19. Interfacial Phenomena in Silver-Copper Sliding Electrical Contact System.

    NASA Astrophysics Data System (ADS)

    Garshasb, Masoud

    Copper-silver sliding electrical contact systems have been investigated using modern surface science and microstructural characterization methods. The experiments involve current carrying metallic brushes sliding on a sputter cleaned rotating slip ring in an ultra high vacuum system. The ambient (and lubricant) of the experiment was water saturated CO(,2) at atmospheric pressure. The characterization techniques included Auger electron spectroscopy (AES), scanning electron microscopy (SEM), x-ray energy spectroscopy (XES), reflection high energy electron diffraction (RHEED), x-ray diffraction (XRD), and in-situ measurements of contact resistance. The electrical contact systems that were studied included homogeneous contacts (Cu/Cu, Ag/Ag) and heterogeneous contacts (Cu/Ag, Ag/Cu). Contact currents ranging from 0 to 50 A were used. In each case the wear particles were characterized by their shape and composition. For the case of heterogeneous contacts, the slip ring surface composition was determined by AES and the concentrations of the elements in the wear debris were plotted versus the contact current to determine the role of current in the Cu-Ag system. Based on the AES and SEM/XES results, some of the characteristic features of the most frequently occurring wear particles are explained and the mechanisms for metal transfer across the interface and wear particle formation are discussed. X-ray diffraction analyses of the mean crystallite size, the non uniform strain and the average lattice parameter of the debris from Cu-Cu systems are presented as a function of contact current. The dependence of the x-ray parameter on current reflects the annealing that takes place at higher currents. This result was supported by RHEED analyses of the wear particles. These various studies have clarified many of the complex mechanisms involved in electrical contact processes.

  20. Adaptive contact elements for three-dimensional explicit transient analysis

    SciTech Connect

    Kulak, R.F.

    1989-01-01

    A finite element method was developed for treating the mechanics of contact between deformable bodies. The method uses a family of adaptive interface elements, which were based on the penalty method, to handle the changing contact configurations that can occur between discretized contacting bodies. The nodal connectivity of these interface elements was allowed to change during the computations in order to accommodate finite sliding. The infusion of these elements in the interface satisfies the stress equilibrium condition during contact. Explicit forms for the nodal internal forces are presented. The methodology has been coded and several sample problems are presented. 23 refs., 29 figs., 6 tabs.

  1. Allergic Contact Dermatitis

    PubMed Central

    Nelson, Jenny L.

    2010-01-01

    Epicutaneous patch testing is the gold standard method for the diagnosis of allergic contact dermatitis. Despite this knowledge, many clinical dermatologists do not offer patch testing in their offices or offer testing with only a limited number of allergens. Introduced in 1995, the Thin-Layer Rapid Use Epicutaneous Test originally contained 23 allergens and one control. In 2007, five additional allergens were added. This United States Food and Drug Administration-approved patch testing system made patch testing more convenient, and after its introduction, more dermatologists offered patch testing services. However, the number of allergens in the Thin-Layer Rapid Use Epicutaneous Test remains relatively low. Every two years, the North American Contact Dermatitis Group collects and reports the data from patch testing among its members to a standardized series of allergens. In 2005-2006, the Group used a series of 65 allergens. Of the top 30 allergens reported in 2005-2006, 10 were not included in the Thin-Layer Rapid Use Epicutaneous Test. Knowledge of and testing for additional allergens such as these may increase patch testing yield. PMID:20967194

  2. [Systemic contact dermatitis].

    PubMed

    Nowak, Daria; Gomułka, Krzysztof; Dziemieszonek, Paulina; Panaszek, Bernard

    2016-01-01

    Systemic contact dermatitis (SCD) is a skin inflammation occurring in a patient after systemic administration of a hapten, which previously caused an allergic contact skin reaction in the same person. Most frequently, hypersensitivity reactions typical for SCD occur after absorption of haptens with food or inhalation. Haptens occur mainly in the forms of metals and compounds present in natural resins, preservatives, food thickeners, flavorings and medicines. For many years, several studies have been conducted on understanding the pathogenesis of SCD in which both delayed type hypersensitivity (type IV) and immediate type I are observed. Components of the complement system are also suspected to attend there. Helper T cells (Th) (Th1 and Th2), cytotoxic T lymphocytes (Tc), and NK cells play a crucial role in the pathogenesis of SCD. They secrete a number of pro-inflammatory cytokines. In addition, regulatory T cells (Tregs) have an important role. They control and inhibit activity of the immune system during inflammation. Tregs release suppressor cytokines and interact directly with a target cell through presentation of immunosuppressive particles at the cell surface. Diagnostic methods are generally the patch test, oral provocation test, elimination diet and lymphocyte stimulation test. There are many kinds of inflammatory skin reactions caused by systemic haptens' distribution. They are manifested in a variety of clinical phenotypes of the disease. PMID:26943310

  3. Mechanical contact by constraints and split-based preconditioning

    SciTech Connect

    Dmitry Karpeyev; Derek Gaston; Jason Hales; Steven Novascone

    2014-03-01

    An accurate implementation of glued mechanical contact was developed in MOOSE based on its Constraint system. This approach results in a superior convergence of elastic structure problems, in particular in BISON. Adaptation of this technique to frictionless and frictional contact models is under way. Additionally, the improved convergence of elastic problems results from the application of the split-based preconditioners to constraint-based systems. This yields a substantial increase in the robustness of elastic solvers when the number of nodes in contact is increased and/or the mesh is refined.

  4. Development of perspective methods for modeling 3D currents for coastal systems in connection with environmental problems in South of France as well as South of Russia

    NASA Astrophysics Data System (ADS)

    Alexeenko, Elena; Sukhinov, Alexander; Roux, Bernard; Meule, Samuel; Chistyakov, Alexander

    2010-05-01

    Shallow water reservoirs are complex multi-parameter hydrodynamic systems. The current and the coupled processes occurring in them are spatially three-dimensional and unsteady, and have essentially nonlinear character. Therefore, the use of field experiments to analyse such a systems is extremely labor intensive and costly. Without underestimating the role of field experiments, it should be nevertheless noted that the most optimal in terms of cost and reliability of the results is an approach based on a combination of relatively inexpensive and safe field experiments and mathematical modeling of the processes under study. The present approach has several advantages with respect to the existing models. Three components of velocity vector from the full system of Navier-Stokes equations (and not on the basis of the hydrostatic approximation) and the equation of the surface elevation are calculated. In most hydrodynamic models of shallow water, the third component of the velocity vector is determined from the equations of continuity and the elevation surface level, which introduces significant error in the determination of the component. Calculation of the three components of velocity vector based on the equations of motion is a time-consuming process, so the hydrostatic approximation is used as an initial approximation for calculating the pressure. This approach greatly reduces the computing time and the costs. Also one of the advantages of the present model is an improved parameterization of the vertical turbulent exchange coefficient, on the basis of ADCP measurement data (Acoustic Doppler Current Profiler). In modern numerical models of vertical turbulent exchange, this coefficient often appears as a fitting parameter. Among the numerous approximations of the coefficient of vertical turbulent exchange, the algebraic subgrid model of Belotcerkovskii, which is based on the determination of turbulent flows as multiplications of averaged over time (correlation

  5. High current capacity electrical connector

    DOEpatents

    Bettis, Edward S.; Watts, Harry L.

    1976-01-13

    An electrical connector is provided for coupling high current capacity electrical conductors such as copper busses or the like. The connector is arranged in a "sandwiched" configuration in which a conductor plate contacts the busses along major surfaces thereof clamped between two stainless steel backing plates. The conductor plate is provided with a plurality of contact buttons affixed therein in a spaced array such that the caps of the buttons extend above the conductor plate surface to contact the busses. When clamping bolts provided through openings in the sandwiched arrangement are tightened, Belleville springs provided under the rim of each button cap are compressed and resiliently force the caps into contact with the busses' contacting surfaces to maintain a predetermined electrical contact area provided by the button cap tops. The contact area does not change with changing thermal or mechanical stresses applied to the coupled conductors.

  6. A differential spin current detection scheme

    NASA Astrophysics Data System (ADS)

    Hemingway, Bryan; Appelbaum, Ian

    2013-09-01

    We provide detailed calculations for modeling an alternative scheme to detect spin polarization of conduction electrons injected into a nonmagnetic metal or degeneratively doped semiconductor using transport to two oppositely polarized ferromagnetic metal contacts. We show that, as in the well-known spin injection problem, detection efficiency can be amplified by the addition of spin-selective tunneling barriers. Considering the appropriate geometry and achievable injection rates, we estimate that the differential current can be as high as 1-10 nA for reasonable design parameters.

  7. Contact heat transfer and thermal contact conductance between nonconforming surfaces in an abrupt contact

    SciTech Connect

    Kumar, R.K.; Kroeger, V.D.

    1996-08-01

    An understanding of the thermal contact conductance behavior when a fuel pin contacts the pressure tube is important in the safety analyses of CANDU reactors. Experiments were therefore performed in a small-scale apparatus with fuel element and pressure tube specimens coming into contact in an argon/oxygen atmosphere, which kinetically simulated steam. The contact was initiated when the fuel-element and pressure-tube specimens were at {approximately} 1,000 C and {approximately} 400 C respectively. The experiments were analyzed using a finite-element code. Heat transfer rates through the contact and thermal contact conductances were determined for contact loads ranging from 20 to 80 N. For most contact loads, the contact conductance increased with time during the transient heat-up of the fuel element specimen. It was found that the calculated thermal contact conductances were in the range of 1 to 30 kW/(m{sup 2} K) based on a reference contact width of 2.5 mm. The variation of contact conductance with contact load was nearly linear.

  8. Solute Transport Across a Contact Interface in Deformable Porous Media

    PubMed Central

    Ateshian, Gerard A.; Maas, Steve; Weiss, Jeffrey A.

    2012-01-01

    A finite element formulation of neutral solute transport across a contact interface between deformable porous media is implemented and validated against analytical solutions. By reducing the integral statements of external virtual work on the two contacting surfaces into a single contact integral, the algorithm automatically enforces continuity of solute molar flux across the contact interface, whereas continuity of the effective solute concentration (a measure of the solute mechano-chemical potential) is achieved using a penalty method. This novel formulation facilitates the analysis of problems in biomechanics where the transport of metabolites across contact interfaces of deformable tissues may be of interest. This contact algorithm is the first to address solute transport across deformable interfaces, and is made available in the public domain, open-source finite element code FEBio (http://mrl.sci.utah.edu/software). PMID:22281406

  9. Solute transport across a contact interface in deformable porous media.

    PubMed

    Ateshian, Gerard A; Maas, Steve; Weiss, Jeffrey A

    2012-04-01

    A finite element formulation of neutral solute transport across a contact interface between deformable porous media is implemented and validated against analytical solutions. By reducing the integral statements of external virtual work on the two contacting surfaces into a single contact integral, the algorithm automatically enforces continuity of solute molar flux across the contact interface, whereas continuity of the effective solute concentration (a measure of the solute mechano-chemical potential) is achieved using a penalty method. This novel formulation facilitates the analysis of problems in biomechanics where the transport of metabolites across contact interfaces of deformable tissues may be of interest. This contact algorithm is the first to address solute transport across deformable interfaces, and is made available in the public domain, open-source finite element code FEBio (http://www.febio.org). PMID:22281406

  10. Attitudes toward community mental health care: the contact paradox revisited.

    PubMed

    Pattyn, E; Verhaeghe, M; Bracke, P

    2013-06-01

    Contact with people with mental illness is considered to be a promising strategy to change stigmatizing attitudes. This study examines the underlying mechanisms of the association between contact and attitudes toward community mental health care. Data are derived from the 2009 survey "Stigma in a Global Context-Belgian Mental Health Study", using the Community Mental Health Ideology-scale. Results show that people who received mental health treatment themselves or have a family member who has been treated for mental health problems report more tolerant attitudes toward community mental health care than people with public contact with people with mental illness. Besides, the perception of the effectiveness of the treatment seems to matter too. Furthermore, emotions arising from public contact are associated with attitudes toward community mental health care. The degree of intimacy and the characteristics of the contact relationship clarify the association between contact and attitudes toward community mental health care. PMID:23179045

  11. Intergroup Contact and Ingroup Reappraisal: Examining the Deprovincialization Thesis

    ERIC Educational Resources Information Center

    Verkuyten, Maykel; Thijs, Jochem; Bekhuis, Hidde

    2010-01-01

    According to the deprovincialization thesis, interethnic contact involves a reappraisal and distancing from the ingroup. Contact can broaden one's horizon by acknowledging and recognizing the value of other cultures and thereby putting the taken-for-granted own cultural standards into perspective. The current research uses data from three surveys…

  12. 47 CFR 25.171 - Contact information reporting requirements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... SERVICES SATELLITE COMMUNICATIONS Applications and Licenses Reporting Requirements for Space Station Operators § 25.171 Contact information reporting requirements. If contact information filed in space station... station's current authorization file. The operator must file the updated information within 10 days....

  13. Disproportionate minority contact.

    PubMed

    Piquero, Alex R

    2008-01-01

    For many years, notes Alex Piquero, youth of color have been overrepresented at every stage of the U.S. juvenile justice system. As with racial disparities in a wide variety of social indicators, the causes of these disparities are not immediately apparent. Some analysts attribute the disparities to "differential involvement"--that is, to differences in offending by minorities and whites. Others attribute them to "differential selection"--that is, to the fact that the justice system treats minority and white offenders in different ways. Still others believe the explanation lies in a combination of the two. Differential involvement may be important earlier in the judicial process, especially in youths' contacts with police, and may influence differential selection later as individuals make their way through the juvenile justice system. Adjudicating between these options, says Piquero, is difficult and may even be impossible. Asking how much minority overrepresentation is due to differences in offending and how much to differences in processing no longer seems a helpful way to frame the discussion. Piquero urges future research to move beyond the debate over "which one matters more" and seek to understand how each of the two hypotheses can explain both the fact of minority overrepresentation in the juvenile justice system and how best to address it. Piquero cites many sizable gaps in the research and policy-relevant literature. Work is needed especially, he says, in analyzing the first stage of the justice system that juveniles confront: police contacts. The police are a critical part of the juvenile justice decision-making system and are afforded far more discretion than any other formal agent of social control, but researchers have paid surprisingly little attention to contacts between police and citizens, especially juveniles. Piquero notes that some states and localities are undertaking initiatives to reduce racial and ethnic disparities. He urges researchers and

  14. Contact Binary Asteroids

    NASA Astrophysics Data System (ADS)

    Rieger, Samantha

    2015-05-01

    Recent observations have found that some contact binaries are oriented such that the secondary impacts with the primary at a high inclination. This research investigates the evolution of how such contact binaries came to exist. This process begins with an asteroid pair, where the secondary lies on the Laplace plane. The Laplace plane is a plane normal to the axis about which the pole of a satellites orbit precesses, causing a near constant inclination for such an orbit. For the study of the classical Laplace plane, the secondary asteroid is in circular orbit around an oblate primary with axial tilt. This system is also orbiting the Sun. Thus, there are two perturbations on the secondarys orbit: J2 and third body Sun perturbations. The Laplace surface is defined as the group of orbits that lie on the Laplace plane at varying distances from the primary. If the secondary is very close to the primary, the inclination of the Laplace plane will be near the equator of the asteroid, while further from the primary the inclination will be similar to the asteroid-Sun plane. The secondary will lie on the Laplace plane because near the asteroid the Laplace plane is stable to large deviations in motion, causing the asteroid to come to rest in this orbit. Assuming the secondary is asymmetrical in shape and the bodys rotation is synchronous with its orbit, the secondary will experience the BYORP effect. BYORP can cause secular motion such as the semi-major axis of the secondary expanding or contracting. Assuming the secondary expands due to BYORP, the secondary will eventually reach the unstable region of the Laplace plane. The unstable region exists if the primary has an obliquity of 68.875 degrees or greater. The unstable region exists at 0.9 Laplace radius to 1.25 Laplace radius, where the Laplace radius is defined as the distance from the central body where the inclination of the Laplace plane orbit is half the obliquity. In the unstable region, the eccentricity of the orbit

  15. Contact dermatitis to Alstroemeria.

    PubMed

    Santucci, B; Picardo, M; Iavarone, C; Trogolo, C

    1985-04-01

    A study was carried out on 50 workers in a floriculture centre to evaluate the incidence of contact dermatitis to Alstroemeria. 3 subjects gave positive reactions to aqueous and ethanolic extracts of cut flowers, stems and leaves. By column chromatography, the allergen was isolated and its chemical structure identified as 6-tuliposide A by proton magnetic resonance and carbon-13 magnetic resonance. Only 6-tuliposide A was isolated from cut flowers, and this gave positive reactions when patch tested at 0.01%; a-methylene-gamma-butyrolactone at 10(-5) (v/v) was positive in the same 3 subjects. Other lactones (gamma-methylene-gamma-butyrolactone, alantolactone, isoalantolactone) were negative at all concentrations used. PMID:3160533

  16. Contact dermatitis in blacks.

    PubMed

    Berardesca, E; Maibach, H I

    1988-07-01

    Black skin is characterized by structural and functional differences such as increased stratum corneum cohesion, melanin content, and stratum corneum layers. These differences seem to make black skin difficult for irritants and light to penetrate, thus explaining the common opinion that skin in blacks is harder and develops contact dermatitis less frequently. The paucity of interpretable epidemiologic data and of clinical and experimental studies does not permit confirmation of this hypothesis, and the few data available are controversial. This article describes the main physiologic differences between black and white barrier function and reviews the literature on irritation, sensitization, and transcutaneous penetration. We found that the data are still too incomplete to generalize on the resistance, or lack thereof, of black skin (versus white skin) to chemical irritation, sensitization, and penetration. PMID:3048818

  17. Impact of environmental conditions on the contact physics of gold contact RF microelectromechanical systems (MEMS) switches

    NASA Astrophysics Data System (ADS)

    Brown, Christopher John

    RF MEMS switch technology is poised to create a new generation of devices capable of vastly outperforming current mechanical and semiconductor switching technology. Despite the efforts of top industrial, academic, and government labs, commercialization of RF MEMS switches has lagged expectations. This dissertation focuses on issues associated with switch contact physics. Understanding the failure mechanisms for metal contact switches is a complex challenge. There is strong interplay between variables such as mechanical creep, deformation, contact heating, contact asperity size, real contact area, and current flow leading to the eventual failure of the switch. Stiction failures moreover are highly sensitive to ambient conditions and absorbed film layers at the switch contact. The experiments in this thesis seek to isolate individual failure mechanisms and tie them to the physics driving that behavior through correlation of experimental data and theoretical modeling. Four experiments in controlled environments were performed: (1) the impact of cryogenic temperatures on RF MEMS contacts, (2) a correlation between experimental data and theoretical modeling for gold asperity creep at room and cryogenic temperatures, (3) a power law relationship between contact resistance and time dependent creep, and (4) the pressure dependence of switch closure. Cryogenic temperatures were used to isolate contaminant film effects. Contaminant films were found to have less mobility at 77 K, and contact resistance measurements showed that the film could be reduced on the contact surface through mechanical cycling and high temperatures at the gold asperities. It was also noted at cryogenic temperatures that the choice of atmosphere was important. A nitrogen atmosphere at liquid nitrogen temperature produced variable contact resistance as the condensed liquid boiled off the switch contacts. Data was correlated with a single asperity creep model to show that change in contact resistance as

  18. Extraterrestrial civilizations: Problems of their evolution

    NASA Technical Reports Server (NTRS)

    Leskov, L. V.

    1987-01-01

    The problem of finding extraterrestrial civilizations and establishing contact with them is directly related to the problem of their evolution. Possible patterns in this evolution and the stages in the evolution of extraterrestrial civilizations are examined.

  19. Reducing contact resistance in graphene devices through contact area patterning.

    PubMed

    Smith, Joshua T; Franklin, Aaron D; Farmer, Damon B; Dimitrakopoulos, Christos D

    2013-04-23

    Performance of graphene electronics is limited by contact resistance associated with the metal-graphene (M-G) interface, where unique transport challenges arise as carriers are injected from a 3D metal into a 2D-graphene sheet. In this work, enhanced carrier injection is experimentally achieved in graphene devices by forming cuts in the graphene within the contact regions. These cuts are oriented normal to the channel and facilitate bonding between the contact metal and carbon atoms at the graphene cut edges, reproducibly maximizing "edge-contacted" injection. Despite the reduction in M-G contact area caused by these cuts, we find that a 32% reduction in contact resistance results in Cu-contacted, two-terminal devices, while a 22% reduction is achieved for top-gated graphene transistors with Pd contacts as compared to conventionally fabricated devices. The crucial role of contact annealing to facilitate this improvement is also elucidated. This simple approach provides a reliable and reproducible means of lowering contact resistance in graphene devices to bolster performance. Importantly, this enhancement requires no additional processing steps. PMID:23473291

  20. Point contacts in encapsulated graphene

    SciTech Connect

    Handschin, Clevin; Fülöp, Bálint; Csonka, Szabolcs; Makk, Péter; Blanter, Sofya; Weiss, Markus; Schönenberger, Christian; Watanabe, Kenji; Taniguchi, Takashi

    2015-11-02

    We present a method to establish inner point contacts with dimensions as small as 100 nm on hexagonal boron nitride (hBN) encapsulated graphene heterostructures by pre-patterning the top-hBN in a separate step prior to dry-stacking. 2- and 4-terminal field effect measurements between different lead combinations are in qualitative agreement with an electrostatic model assuming point-like contacts. The measured contact resistances are 0.5–1.5 kΩ per contact, which is quite low for such small contacts. By applying a perpendicular magnetic field, an insulating behaviour in the quantum Hall regime was observed, as expected for inner contacts. The fabricated contacts are compatible with high mobility graphene structures and open up the field for the realization of several electron optical proposals.

  1. A Prototype Antifungal Contact Lens

    PubMed Central

    Ciolino, Joseph B.; Hudson, Sarah P.; Mobbs, Ashley N.; Hoare, Todd R.; Iwata, Naomi G.; Fink, Gerald R.

    2011-01-01

    Purpose. To design a contact lens to treat and prevent fungal ocular infections. Methods. Curved contact lenses were created by encapsulating econazole-impregnated poly(lactic-co-glycolic) acid (PLGA) films in poly(hydroxyethyl methacrylate) (pHEMA) by ultraviolet photopolymerization. Release studies were conducted in phosphate-buffered saline at 37°C with continuous shaking. The contact lenses and their release media were tested in an antifungal assay against Candida albicans. Cross sections of the pre- and postrelease contact lenses were characterized by scanning electron microscopy and by Raman spectroscopy. Results. Econazole-eluting contact lenses provided extended antifungal activity against Candida albicans fungi. Fungicidal activity varied in duration and effectiveness depending on the mass of the econazole-PLGA film encapsulated in the contact lens. Conclusions. An econazole-eluting contact lens could be used as a treatment for fungal ocular infections. PMID:21527380

  2. Investigation of different contact geometries for partial rear metal contact of high-efficiency silicon solar cells

    NASA Astrophysics Data System (ADS)

    Mitra, Suchismita; Ghosh, Hemanta; Saha, Hiranmay; Datta, Swapan Kumar

    2015-11-01

    In this paper, we have investigated the dependence of the parameters of partial rear metal contact (PRC) solar cells on two commonly used geometrical configurations, viz. grid contact and square contact. It is demonstrated that while the geometry of rear metallic contact having the same fractional coverage changes the base spreading resistance significantly, rear surface passivation and back reflectance depend only on the fractional coverage of the real metal contact and are independent of the geometry of the contact. The performed analysis indicates that the base spreading resistance is much higher for square contact cells compared to that of grid contact cells having the same fractional coverage. While open-circuit voltage and short-circuit current are found to be essentially independent of the contact geometry, the fill factor is significantly affected by the geometry, indicating that the design of high-efficiency cells with partial rear grid contact is less critical in comparison to that of square contact cells for optimized performance. Results indicate that for a 180 μm cell, an efficiency enhancement of 14% is possible for  <10% fractional rear metallization over the baseline efficiency of about 19% for solar cells having full-area rear metallization. For 50 μm thin cells, the corresponding improvement in efficiency is 17%, leading to 22% efficiency solar cells.

  3. Medicare: Helpful Contacts

    MedlinePlus

    ... not support or have Cascading Style Sheets (CSS) disabled. For a more optimal experience viewing this application, ... application currently does not support browsers with "JavaScript" disabled. Please enable JavaScript and refresh the page to ...

  4. Dynamics of the Molten Contact Line

    NASA Technical Reports Server (NTRS)

    Sonin, Ain A.; Duthaler, Gregg; Liu, Michael; Torresola, Javier; Qiu, Taiqing

    1999-01-01

    amorphous silicon dioxide chips. Each chip has 32 sensors distributed on its surface in arrays. The time response is better than 10 ms. At the time of writing, sensor calibration is in progress. Results on thermal transients during contact line passage will be discussed at the conference. While we expect that the data will provide information on the near-contact-line heat transfer process, we also foresee possible problems. First, the spatial resolution of the sensors may be insufficient to resolve the near-contact-line region. Second, the sensors protrude about 0.5 microns above the substrate surface, and may affect the contact line motion. Third, a sensor's temperature history depends on both the heat flux distribution into it from the fusion front and the thermal properties of the substrate below it and the solidified melt between it and the fusion front. The heat flux distribution in the contact line region must therefore be unfolded from computations of the overall system's transient thermal response.

  5. Modeling the Emergence of Contact Languages

    PubMed Central

    Tria, Francesca; Servedio, Vito D.P.; Mufwene, Salikoko S.; Loreto, Vittorio

    2015-01-01

    Contact languages are born out of the non-trivial interaction of two (or more) parent languages. Nowadays, the enhanced possibility of mobility and communication allows for a strong mixing of languages and cultures, thus raising the issue of whether there are any pure languages or cultures that are unaffected by contact with others. As with bacteria or viruses in biological evolution, the evolution of languages is marked by horizontal transmission; but to date no reliable quantitative tools to investigate these phenomena have been available. An interesting and well documented example of contact language is the emergence of creole languages, which originated in the contacts of European colonists and slaves during the 17th and 18th centuries in exogenous plantation colonies of especially the Atlantic and Indian Ocean. Here, we focus on the emergence of creole languages to demonstrate a dynamical process that mimics the process of creole formation in American and Caribbean plantation ecologies. Inspired by the Naming Game (NG), our modeling scheme incorporates demographic information about the colonial population in the framework of a non-trivial interaction network including three populations: Europeans, Mulattos/Creoles, and Bozal slaves. We show how this sole information makes it possible to discriminate territories that produced modern creoles from those that did not, with a surprising accuracy. The generality of our approach provides valuable insights for further studies on the emergence of languages in contact ecologies as well as to test specific hypotheses about the peopling and the population structures of the relevant territories. We submit that these tools could be relevant to addressing problems related to contact phenomena in many cultural domains: e.g., emergence of dialects, language competition and hybridization, globalization phenomena. PMID:25875371

  6. Modeling the emergence of contact languages.

    PubMed

    Tria, Francesca; Servedio, Vito D P; Mufwene, Salikoko S; Loreto, Vittorio

    2015-01-01

    Contact languages are born out of the non-trivial interaction of two (or more) parent languages. Nowadays, the enhanced possibility of mobility and communication allows for a strong mixing of languages and cultures, thus raising the issue of whether there are any pure languages or cultures that are unaffected by contact with others. As with bacteria or viruses in biological evolution, the evolution of languages is marked by horizontal transmission; but to date no reliable quantitative tools to investigate these phenomena have been available. An interesting and well documented example of contact language is the emergence of creole languages, which originated in the contacts of European colonists and slaves during the 17th and 18th centuries in exogenous plantation colonies of especially the Atlantic and Indian Ocean. Here, we focus on the emergence of creole languages to demonstrate a dynamical process that mimics the process of creole formation in American and Caribbean plantation ecologies. Inspired by the Naming Game (NG), our modeling scheme incorporates demographic information about the colonial population in the framework of a non-trivial interaction network including three populations: Europeans, Mulattos/Creoles, and Bozal slaves. We show how this sole information makes it possible to discriminate territories that produced modern creoles from those that did not, with a surprising accuracy. The generality of our approach provides valuable insights for further studies on the emergence of languages in contact ecologies as well as to test specific hypotheses about the peopling and the population structures of the relevant territories. We submit that these tools could be relevant to addressing problems related to contact phenomena in many cultural domains: e.g., emergence of dialects, language competition and hybridization, globalization phenomena. PMID:25875371

  7. Wireless Measurement of Contact and Motion Between Contact Surfaces

    NASA Technical Reports Server (NTRS)

    Woodard, Stanley E.; Taylor, Bryant D.

    2007-01-01

    This method uses a magnetic-field- response contact sensor that is designed to identify surface contact and motion between contact locations. The sensor has three components: (1) a capacitor-inductor circuit with two sets of electrical contact pads, (2) a capacitor with a set of electrical contact pads, and (3) an inductor with a set of electrical contact pads. A unique feature of this sensor is that it is inherently multifunctional. Information can be derived from analyzing such sensor response attributes as amplitude, frequency, and bandwidth. A change in one attribute can be due to a change in a physical property of a system. A change in another attribute can be due to another physical property, which has no relationship to the first one.

  8. Analysis of composite material interface crack face contact and friction effects using a new node-pairs contact algorithm

    NASA Astrophysics Data System (ADS)

    Zhong, Zhi-Peng; He, Yu-Bo; Wan, Shui

    2014-06-01

    A new node-pairs contact algorithm is proposed to deal with a composite material or bi-material interface crack face contact and friction problem (e.g., resistant coating and thermal barrier coatings) subjected to complicated load conditions. To decrease the calculation scale and calculation errors, the local Lagrange multipliers are solved only on a pair of contact nodes using the Jacobi iteration method, and the constraint modification of the tangential multipliers are required. After the calculation of the present node-pairs Lagrange multiplier, it is turned to next contact node-pairs until all node-pairs have finished. Compared with an ordinary contact algorithm, the new local node-pairs contact algorithm is allowed a more precise element on the contact face without the stiffness matrix singularity. The stress intensity factors (SIFs) and the contact region of an infinite plate central crack are calculated and show good agreement with those in the literature. The contact zone near the crack tip as well as its influence on singularity of stress fields are studied. Furthermore, the frictional contacts are also considered and found to have a significant influence on the SIFs. The normalized mode-II stress intensity factors K̂II for the friction coefficient decrease by 16% when f changes from 1 to 0.

  9. Hysteresis during contact angles measurement.

    PubMed

    Diaz, M Elena; Fuentes, Javier; Cerro, Ramon L; Savage, Michael D

    2010-03-15

    A theory, based on the presence of an adsorbed film in the vicinity of the triple contact line, provides a molecular interpretation of intrinsic hysteresis during the measurement of static contact angles. Static contact angles are measured by placing a sessile drop on top of a flat solid surface. If the solid surface has not been previously in contact with a vapor phase saturated with the molecules of the liquid phase, the solid surface is free of adsorbed liquid molecules. In the absence of an adsorbed film, molecular forces configure an advancing contact angle larger than the static contact angle. After some time, due to an evaporation/adsorption process, the interface of the drop coexists with an adsorbed film of liquid molecules as part of the equilibrium configuration, denoted as the static contact angle. This equilibrium configuration is metastable because the droplet has a larger vapor pressure than the surrounding flat film. As the drop evaporates, the vapor/liquid interface contracts and the apparent contact line moves towards the center of the drop. During this process, the film left behind is thicker than the adsorbed film and molecular attraction results in a receding contact angle, smaller than the equilibrium contact angle. PMID:20060981

  10. Some recent advances in 3D crack and contact analysis of elastic solids with transverse isotropy and multifield coupling

    NASA Astrophysics Data System (ADS)

    Chen, Wei-Qiu

    2015-10-01

    Significant progress has been made in mixed boundary-value problems associated with three-dimensional (3D) crack and contact analyses of advanced materials featuring more complexities compared to the conventional isotropic elastic materials. These include material anisotropy and multifield coupling, two typical characteristics of most current multifunctional materials. In this paper we try to present a state-of-the-art description of 3D exact/analytical solutions derived for crack and contact problems of elastic solids with both transverse isotropy and multifield coupling in the latest decade by the potential theory method in the spirit of V. I. Fabrikant, whose ingenious breakthrough brings new vigor and vitality to the old research subject of classical potential theory. We are particularly interested in crack and contact problems with certain nonlinear features. Emphasis is also placed on the coupling between the temperature field (or the like) and other physical fields (e.g., elastic, electric, and magnetic fields). We further highlight the practical significance of 3D contact solutions, in particular in applications related to modern scanning probe microscopes.

  11. Bernoulli effect and contact potential difference in superconductors

    SciTech Connect

    Omel'yanchuk, A.N.; Beloborod'ko, S.I.

    1983-10-01

    An expression is derived for the Bernoulli potential that arises in superconductors with an inhomogeneous current distribution. The expression is valid for arbitrary temperatures and superfluid velocities. In the superconductor--dielectric--superconductor system we consider the Bernoulli effect, which manifests itself in a contact potential difference between the superconductors. The potential difference is determined by the currents flowing through one plate of the contact and can be measured with a voltmeter in the quasi-stationary regime.

  12. Atomically Thin Ohmic Edge Contacts Between Two-Dimensional Materials.

    PubMed

    Guimarães, Marcos H D; Gao, Hui; Han, Yimo; Kang, Kibum; Xie, Saien; Kim, Cheol-Joo; Muller, David A; Ralph, Daniel C; Park, Jiwoong

    2016-06-28

    With the decrease of the dimensions of electronic devices, the role played by electrical contacts is ever increasing, eventually coming to dominate the overall device volume and total resistance. This is especially problematic for monolayers of semiconducting transition-metal dichalcogenides (TMDs), which are promising candidates for atomically thin electronics. Ideal electrical contacts to them would require the use of similarly thin electrode materials while maintaining low contact resistances. Here we report a scalable method to fabricate ohmic graphene edge contacts to two representative monolayer TMDs, MoS2 and WS2. The graphene and TMD layer are laterally connected with wafer-scale homogeneity, no observable overlap or gap, and a low average contact resistance of 30 kΩ·μm. The resulting graphene edge contacts show linear current-voltage (I-V) characteristics at room temperature, with ohmic behavior maintained down to liquid helium temperatures. PMID:27299957

  13. Wearable telescopic contact lens.

    PubMed

    Arianpour, Ashkan; Schuster, Glenn M; Tremblay, Eric J; Stamenov, Igor; Groisman, Alex; Legerton, Jerry; Meyers, William; Amigo, Goretty Alonso; Ford, Joseph E

    2015-08-20

    We describe the design, fabrication, and testing of a 1.6 mm thick scleral contact lens providing both 1× and 2.8× magnified vision paths, intended for use as a switchable eye-borne telescopic low-vision aid. The F/9.7 telescopic vision path uses an 8.2 mm diameter annular entrance pupil and 4 internal reflections in a polymethyl methacrylate precision optic. This gas-impermeable insert is contained inside a smooth outer casing of rigid gas-permeable polymer, which also provides achromatic correction for refraction at the curved lens face. The unmagnified F/4.1 vision path is through the central aperture of the lens, with additional transmission between the annular telescope rings to enable peripheral vision. We discuss potential solutions for providing oxygenation for an extended wear version of the lens. The prototype lenses were characterized using a scale-model human eye, and telescope functionality was confirmed in a small-scale clinical (nondispensed) demonstration. PMID:26368753

  14. Numerical Simulation of Dynamic Contact Angles and Contact Lines in Multiphase Flows using Level Set Method

    NASA Astrophysics Data System (ADS)

    Pendota, Premchand

    Many physical phenomena and industrial applications involve multiphase fluid flows and hence it is of high importance to be able to simulate various aspects of these flows accurately. The Dynamic Contact Angles (DCA) and the contact lines at the wall boundaries are a couple of such important aspects. In the past few decades, many mathematical models were developed for predicting the contact angles of the inter-face with the wall boundary under various flow conditions. These models are used to incorporate the physics of DCA and contact line motion in numerical simulations using various interface capturing/tracking techniques. In the current thesis, a simple approach to incorporate the static and dynamic contact angle boundary conditions using the level set method is developed and implemented in multiphase CFD codes, LIT (Level set Interface Tracking) (Herrmann (2008)) and NGA (flow solver) (Desjardins et al (2008)). Various DCA models and associated boundary conditions are reviewed. In addition, numerical aspects such as the occurrence of a stress singularity at the contact lines and grid convergence of macroscopic interface shape are dealt with in the context of the level set approach.

  15. Problem Periods

    MedlinePlus

    ... gov/ Home Body Getting your period Problem periods Problem periods It’s common to have cramps or feel ... doctor Some common period problems Signs of period problems top One way to know if you may ...

  16. Balance Problems

    MedlinePlus

    ... it could be a sign of a balance problem. Balance problems can make you feel unsteady or as if ... related injuries, such as hip fracture. Some balance problems are due to problems in the inner ear. ...

  17. Balance Problems

    MedlinePlus

    ... often, it could be a sign of a balance problem. Balance problems can make you feel unsteady or as ... fall-related injuries, such as hip fracture. Some balance problems are due to problems in the inner ...

  18. [Short bowel syndrome. Still a current problem].

    PubMed

    Calomino, N; Malerba, M; Oliva, G; Palasciano, G; Cappelli, A; Salvestrini, F; Tanzini, G

    1997-01-01

    In the last year the Authors operated two patients presenting with a clinical feature of intestinal infarct. A wide intestinal resection was performed and patients had a residual tract of 40 cm and 50 cm of bowel respectively, later manifesting as short bowel syndrome. It was not possible during the operation to preserve the Baubin valve in one case, in the other one the value had been sacrificed during a previous operation for right colonic malignancy. In the postoperative period, patients were temporarily transferred to the intensive care unit, returning in the surgery ward after few days, and counting total parenteral nutrition with progressive decreasing mixture in calories. Contemporarly enteral nutrition was started slowly increasing the quantity of water, calories and azote administration. In a second time oral diet was started up to completely weaning parenteral and enteral nutrition. At the present patients are enlisted in quarterly follow-up, completely stabilized, and independent from artificial nutrition with a good quality of life. Furthermore a saving of sanitary costs was obtained. PMID:9296596

  19. Library Networking: Current Problems and Future Prospects!

    ERIC Educational Resources Information Center

    Mockus, Laima

    1983-01-01

    Profiles the New England Library Information Network (NELINET), whose purpose is to serve as focal point for achievement of cost effective library automation through shared resources. Origins of NELINET are highlighted as well as NELINET services, including archival tapes, role as OCLC broker network, cost effectiveness, and successful use of new…

  20. CURRENT TECHNICAL PROBLEMS IN EMERGY ANALYSIS

    EPA Science Inventory

    : Emergy Analysis has been a rapidly evolving assessment methodology for the past 30 years. This process of development was primarily driven by the inquiring mind and ceaseless activity of its founder, H.T. Odum, his students, and colleagues. Historically, as new kinds of proble...