Specimen loading list for the varying temperature experiment
Energy Technology Data Exchange (ETDEWEB)
Qualls, A.L.; Sitterson, R.G. [Oak Ridge National Lab., TN (United States)
1998-09-01
The varying temperature experiment HFIR-RB-13J has been assembled and inserted in the reactor. Approximately 5300 specimens were cleaned, inspected, matched, and loaded into four specimen holders. A listing of each specimen loaded into the steady temperature holder, its position in the capsule, and the identification of the corresponding specimen loaded into the varying temperature holder is presented in this report.
High Flux Isotope Reactor (HFIR)
Federal Laboratory Consortium — The HFIR at Oak Ridge National Laboratory is a light-water cooled and moderated reactor that is the United States’ highest flux reactor-based neutron source. HFIR...
Energy Technology Data Exchange (ETDEWEB)
Imhoff, Seth D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Gibbs, Paul Jacob [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Solis, Eunice Martinez [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2017-09-28
Process exploration for fuel production for the High Flux Isotope Reactor (HFIR) using cast LEU-10wt.%Mo as an initial processing step has just begun. This project represents the first trials concerned with casting design and quality. The studies carried out over the course of this year and information contained in this report address the initial mold development to be used as a starting point for future operations. In broad terms, the final billet design is that of a solid rolling blank with an irregular octagonal cross section. The work covered here is a comprehensive view of the initial attempts to produce a sound casting. This report covers the efforts to simulate, predict, cast, inspect, and revise the initial mold design.
Upgraded HFIR Fuel Element Welding System
Energy Technology Data Exchange (ETDEWEB)
Sease, John D [ORNL
2010-02-01
The welding of aluminum-clad fuel plates into aluminum alloy 6061 side plate tubing is a unique design feature of the High Flux Isotope Reactor (HFIR) fuel assemblies as 101 full-penetration circumferential gas metal arc welds (GMAW) are required in the fabrication of each assembly. In a HFIR fuel assembly, 540 aluminum-clad fuel plates are assembled into two nested annular fuel elements 610 mm (24-inches) long. The welding process for the HFIR fuel elements was developed in the early 1960 s and about 450 HFIR fuel assemblies have been successfully welded using the GMAW process qualified in the 1960 s. In recent years because of the degradation of the electronic and mechanical components in the old HFIR welding system, reportable defects in plate attachment or adapter welds have been present in almost all completed fuel assemblies. In October 2008, a contract was awarded to AMET, Inc., of Rexburg, Idaho, to replace the old welding equipment with standard commercially available welding components to the maximum extent possible while maintaining the qualified HFIR welding process. The upgraded HFIR welding system represents a major improvement in the welding system used in welding HFIR fuel elements for the previous 40 years. In this upgrade, the new inner GMAW torch is a significant advancement over the original inner GMAW torch previously used. The innovative breakthrough in the new inner welding torch design is the way the direction of the cast in the 0.762 mm (0.030-inch) diameter aluminum weld wire is changed so that the weld wire emerging from the contact tip is straight in the plane perpendicular to the welding direction without creating any significant drag resistance in the feeding of the weld wire.
Key metrics for HFIR HEU and LEU models
Energy Technology Data Exchange (ETDEWEB)
Ilas, Germina [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Betzler, Benjamin R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Chandler, David [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Renfro, David G. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Davidson, Eva E. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2016-10-25
This report compares key metrics for two fuel design models of the High Flux Isotope Reactor (HFIR). The first model represents the highly enriched uranium (HEU) fuel currently in use at HFIR, and the second model considers a low-enriched uranium (LEU) interim design fuel. Except for the fuel region, the two models are consistent, and both include an experiment loading that is representative of HFIR's current operation. The considered key metrics are the neutron flux at the cold source moderator vessel, the mass of ^{252}Cf produced in the flux trap target region as function of cycle time, the fast neutron flux at locations of interest for material irradiation experiments, and the reactor cycle length. These key metrics are a small subset of the overall HFIR performance and safety metrics. They were defined as a means of capturing data essential for HFIR's primary missions, for use in optimization studies assessing the impact of HFIR's conversion from HEU fuel to different types of LEU fuel designs.
Fabrication procedures for HFIR control plates
Energy Technology Data Exchange (ETDEWEB)
Bowden, G.A.; Hicks, G.R.; Knight, R.W.
1984-10-01
The HFIR control system uses Alclad cylindrically shaped components, which have regions containing 31 vol % Eu/sub 2/O/sub 3/ and 38 vol % Ta, respectively. Exacting control of the water passage between these components and adjacent reactor parts is mandatory, and precise dimensional control of the finished products is required. This report describes the procedures developed for manufacturing outer control plates and inner control cylinders. Results are cited which demonstrate that circular-shaped outer control plates can be produced with less than 0.025-in. variation from the specified 9.300-in. radius in any region of the plate. Other results show that, by the exercise of careful control, inner control, inner control plates can be welded into cylindrical geometry with diametrical variations held to less than +- 0.010 in. of the intended 17.846-in. average diam. The cylinders can then be explosively sized, while under compression, with diametric variations of less than 0.005 in. while controlling roundness variations to less than 0.030 in. from the specified 17.842-in. finished diam.
Meeting notes of the High Flux Isotope Reactor (HFIR) futures group
Energy Technology Data Exchange (ETDEWEB)
Houser, M.M. [comp.
1995-08-01
This report is a compilation of the notes from the ten meetings. The group charter is: (1) to identify and characterize the range of possibilities and necessities for keeping the HFIR operating for at least the next 15 years; (2) to identify and characterize the range of possibilities for enhancing the scientific and technical utility of the HFIR; (3) to evaluate the benefits or impacts of these possibilities on the various scientific fields that use the HFIR or its products; (4) to evaluate the benefits or impacts on the operation and maintenance of the HFIR facility and the regulatory requirements; (5) to estimate the costs, including operating costs, and the schedules, including downtime, for these various possibilities; and one possible impact of proposed changes may be to stimulate increased pressure for a reduced enrichment fuel for HFIR.
Fracture analysis of HFIR beam tube caused by radiation embrittlement
Energy Technology Data Exchange (ETDEWEB)
Chang, S.J. [Oak Ridge National Lab., TN (United States). Research Reactors Div.
1994-12-31
With an attempt to estimate the neutron beam tube embrittlement condition for the Oak Ridge High Flux Isotope Reactor (HFIR), fracture mechanics calculations are carried out in this paper. The analysis provides some numerical result on how the tube has been structurally weakened. In this calculation, a lateral impact force is assumed. Numerical result is obtained on how much the critical crack size should be reduced if the beam tube has been subjected to an extended period of irradiation. It is also calculated that buckling strength of the tube is increased, not decreased, with irradiation.
Cadmium verification measurements of HFIR shroud assembly 22
Energy Technology Data Exchange (ETDEWEB)
Chapman, J.A.; Schultz, F.J.
1994-04-01
This report discusses radiation-based nondestructive examination methods which have been used to successfully verify the presence of cadmium in High Flux Isotope Reactor (HFIR) spent-fuel shroud assembly number 22 (SA22). These measurements show, in part, that SA22 is certified to meet the criticality safety specifications for a proposed reconfiguration of the HFIR spent-fuel storage array. Measurement of the unique 558.6-keV gamma-ray from neutron radiative capture on cadmium provided conclusive evidence for the presence of cadmium in the outer shroud of the assembly. Cadmium verification in the center post and outer shroud was performed by measuring the degree of neutron transmission in SA22 relative to two calibration shroud assemblies. Each measurement was performed at a single location on the center post and outer shroud. These measurements do not provide information on the spatial distribution or uniformity of cadmium within an assembly. Separate measurements using analog and digital radiography were performed to (a) globally map the continuity of cadmium internal mass, and (b) locally determine the thickness of cadmium. Radiography results will be reported elsewhere. The measurements reported here should not be used to infer the thickness of cadmium in either the center post or outer shroud of an assembly.
Design and simulation of the CG1 beamline at HFIR
Nagler, S E; Moon, R M
2002-01-01
In the near future a super-critical hydrogen cold source will be installed in the HB4 beam tube of the High Flux Isotope Reactor (HFIR), Oak Ridge National Laboratory. The cold source will illuminate four neutron guides. Here we discuss the design and simulation of the guide CG1, dedicated to a new triple axis spectrometer. The conceptual design for the HFIR guides, including CG1, was aided by numerical calculations of neutron trajectories and acceptance diagrams. The CG1 guide consists of a partially trumpeting two-channel bender and a straight guide section. The design was subsequently modeled in detail from source to specimen, utilizing the McStas program. The lessons learned from the McStas simulations resulted in some minor but important changes in the design, and these were also verified using the original method of calculation. The resulting combination of guide and vertically focusing monochromator should deliver a beam with excellent spatial and angular distributions in and out of the scattering plan...
Impact of HFIR LEU Conversion on Beryllium Reflector Degradation Factors
Energy Technology Data Exchange (ETDEWEB)
Ilas, Dan [ORNL
2013-10-01
An assessment of the impact of low enriched uranium (LEU) conversion on the factors that may cause the degradation of the beryllium reflector is performed for the High Flux Isotope Reactor (HFIR). The computational methods, models, and tools, comparisons with previous work, along with the results obtained are documented and discussed in this report. The report documents the results for the gas and neutronic poison production, and the heating in the beryllium reflector for both the highly enriched uranium (HEU) and LEU HFIR configurations, and discusses the impact that the conversion to LEU may have on these quantities. A time-averaging procedure was developed to calculate the isotopic (gas and poisons) production in reflector. The sensitivity of this approach to different approximations is gauged and documented. The results show that the gas is produced in the beryllium reflector at a total rate of 0.304 g/cycle for the HEU configuration; this rate increases by ~12% for the LEU case. The total tritium production rate in reflector is 0.098 g/cycle for the HEU core and approximately 11% higher for the LEU core. A significant increase (up to ~25%) in the neutronic poisons production in the reflector during the operation cycles is observed for the LEU core, compared to the HEU case, for regions close to the core s horizontal midplane. The poisoning level of the reflector may increase by more than two orders of magnitude during long periods of downtime. The heating rate in the reflector is estimated to be approximately 20% lower for the LEU core than for the HEU core. The decrease is due to a significantly lower contribution of the heating produced by the gamma radiation for the LEU core. Both the isotopic (gas and neutronic poisons) production and the heating rates are spatially non-uniform throughout the beryllium reflector volume. The maximum values typically occur in the removable reflector and close to the midplane.
Status of lithium-filled specimen subcapsules for the HFIR-MFE-RB10J experiment
Energy Technology Data Exchange (ETDEWEB)
Robertson, J.P.; Howell, M.; Lenox, K.E. [Oak Ridge National Lab., TN (United States)
1998-09-01
The HFIR-MFE-RB-10J experiment will be irradiated in a Removable Beryllium position in the HFIR for 10 reactor cycles, accumulating approximately 5 dpa in steel. The upper region of the capsule contains two lithium-filled subcapsules containing vanadium specimens. This report describes the techniques developed to achieve a satisfactory lithium fill with a specimen occupancy of 26% in each subcapsule.
Small Specimen Data from a High Temperature HFIR Irradiation Experiment
Energy Technology Data Exchange (ETDEWEB)
Burchell, Timothy D [ORNL; McDuffee, Joel Lee [ORNL; Thoms, Kenneth R [ORNL
2014-01-01
The HTV capsule is a High Flux Isotope Reactor (HFIR) target-rod capsule designed to operate at very high temperatures. The graphite containing section of the capsule (in core) is approximately 18 inches (457.2 mm) long and is separated into eight temperature zones. The specimen diameters within each zone are set to achieve the desired gas gap and hence design temperature (900 C, 1200 C or 1500 C). The capsule has five zones containing 0.400 inch (10.16 mm) diameter specimens, two zones containing 0.350 inch (8.89 mm) diameter specimens and one zone containing 0.300 inch (7.62 mm) diameter specimens. The zones have been distributed within the experiment to optimize the gamma heating from the HFIR core as well as minimize the axial heat flow in the capsule. Consequently, there are two 900 C zones, three 1200 C zones, and three 1500 C zones within the HTV capsule. Each zone contains nine specimens 0.210 0.002 inches (5.334 mm) in length. The capsule will be irradiated to a peak dose of 3.17 displacements per atom. The HTV specimens include samples of the following graphite grades: SGL Carbon s NBG-17 and NBG-18, GrafTech s PCEA, Toyo Tanso s IG-110, Mersen s 2114 and the reference grade H-451 (SGL Carbon). As part of the pre-irradiation program the specimens were characterized using ASTM Standards C559 for bulk density, and ASTM C769 for approximate Young s modulus from the sonic velocity. The probe frequency used for the determination of time of flight of the ultrasonic signal was 2.25 MHz. Marked volume (specimen diameter) effects were noted for both bulk density (increased with increasing specimen volume or diameter) and Dynamic Young s modulus (decreased with increasing specimen volume or diameter). These trends are extended by adding the property vs. diameter data for unirradiated AGC-1 creep specimens (nominally 12.5 mm-diameter x 25.4 mm-length). The relatively large reduction in Dynamic Young s Modulus was surprising given the trend for increasing density
Materials Selection for the HFIR Cold Neutron Source
Energy Technology Data Exchange (ETDEWEB)
Farrell, K.
2001-08-24
In year 2002 the High Flux Isotope Reactor (HFIR) will be fitted with a source of cold neutrons to upgrade and expand its existing neutron scattering facilities. The in-reactor components of the new source consist of a moderator vessel containing supercritical hydrogen gas moderator at a temperature of 20K and pressure of 15 bar, and a surrounding vacuum vessel. They will be installed in an enlarged beam tube located at the site of the present horizontal beam tube, HB-4; which terminates within the reactor's beryllium reflector. These components must withstand exceptional service conditions. This report describes the reasons and factors underlying the choice of 6061-T6 aluminum alloy for construction of the in-reactor components. The overwhelming considerations are the need to minimize generation of nuclear heat and to remove that heat through the flowing moderator, and to achieve a minimum service life of about 8 years coincident with the replacement schedule for the beryllium reflector. 6061-T6 aluminum alloy offers the best combination of low nuclear heating, high thermal conductivity, good fabricability, compatibility with hydrogen, superior cryogenic properties, and a well-established history of satisfactory performance in nuclear environments. These features are documented herein. An assessment is given of the expected performance of each component of the cold source.
In-situ measurement of the electrical conductivity of aluminum oxide in HFIR
Energy Technology Data Exchange (ETDEWEB)
Zinkle, S.J.; White, D.P.; Snead, L.L. [Oak Ridge National Lab., TN (United States)] [and others
1996-10-01
A collaborative DOE/Monbusho irradiation experiment has been completed which measured the in-situ electrical resistivity of 12 different grades of aluminum oxide during HFIR neutron irradiation at 450{degrees}C. No evidence for bulk RIED was observed following irradiation to a maximum dose of 3 dpa with an applied dc electric field of 200 V/mm.
Preliminary Multiphysics Analyses of HFIR LEU Fuel Conversion using COMSOL
Energy Technology Data Exchange (ETDEWEB)
Freels, James D [ORNL; Bodey, Isaac T [ORNL; Arimilli, Rao V [ORNL; Curtis, Franklin G [ORNL; Ekici, Kivanc [ORNL; Jain, Prashant K [ORNL
2011-06-01
4 of this report. The HFIR LEU conversion project has also obtained the services of Dr. Prashant K. Jain of the Reactor & Nuclear Systems Division (RNSD) of ORNL. Prashant has quickly adapted to the COMSOL tools and has been focusing on thermal-structure interaction (TSI) issues and development of alternative 3D model approaches that could yield faster-running solutions. Prashant is the primary contributor to Section 5 of the report. And finally, while incorporating findings from all members of the COMSOL team (i.e., the team) and contributing as the senior COMSOL leader and advocate, Dr. James D. Freels has focused on the 3D model development, cluster deployment, and has contributed primarily to Section 3 and overall integration of this report. The team has migrated to the current release of COMSOL at version 4.1 for all the work described in this report, except where stated otherwise. Just as in the performance of the research, each of the respective sections has been originally authored by the respective authors. Therefore, the reader will observe a contrast in writing style throughout this document.
Study of in-reactor creep of vanadium alloy in the HFIR RB-12J experiment
Energy Technology Data Exchange (ETDEWEB)
Strain, R.V.; Konicek, C.F.; Tsai, H. [Argonne National Lab., IL (United States)
1996-10-01
Biaxial creep specimens will be included in the HFIR RB-12J experiment to study in-reactor creep of the V-4Cr-4Ti alloy at {approx}500{degrees}C and 5 dpa. These specimens were fabricated with the 500-kg, heat (832665) material and pressurized to attain 0, 50, 100, 150, and 200 MPa mid-wall hoop stresses during the irradiation.
Neutron dosimetry and damage calculations for the HFIR-JP-23 irradiations
Energy Technology Data Exchange (ETDEWEB)
Greenwood, L.R.; Ratner, R.T. [Pacific Northwest National Lab., Richland, WA (United States)
1996-10-01
Neutron fluence measurements and radiation damage calculations are reported for the joint US-Japanese experiment JP-23, which was conducted in target position G6 of the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL). The maximum neutron fluence at midplane was 4.4E+22 n/cm{sup 2} resulting in about 9.0 dpa in type 316 stainless steel.
Analysis of HFIR Dosimetry Experiments Performed in Cycles 400 and 401
Energy Technology Data Exchange (ETDEWEB)
Remec, Igor [ORNL; Baldwin, Charles A [ORNL
2008-09-01
The High Flux Isotope Reactor (HFIR) has been in operation at Oak Ridge National Laboratory since 1966. To upgrade and enhance capabilities for neutron science research at the reactor, a larger HB-2 beam tube was installed in April of 2002. To assess, experimentally, the impact of this larger beam tube on radiation damage rates [i.e., displacement-per-atom (dpa) rates] used in vessel life extension studies, dosimetry experiments were performed from April to August 2004 during fuel cycles 400 and 401. This report documents the analysis of the dosimetry experiments and the determination of best-estimate dpa rates. These dpa rates are obtained by performing a least-squares adjustment of calculated neutron and gamma-ray fluxes and the measured responses of radiometric monitors and beryllium helium accumulation fluence monitors. The best-estimate dpa rates provided here will be used to update HFIR pressure vessel life extension studies, which determine the pressure/temperature limits for reactor operation and the HFIR pressure vessel's remaining life. All irradiation parameters given in this report correspond to a reactor power of 85 MW.
Energy Technology Data Exchange (ETDEWEB)
Daily, Charles R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2015-10-01
An assessment of the impact on the High Flux Isotope Reactor (HFIR) reactor vessel (RV) displacements-per-atom (dpa) rates due to operations with the proposed low enriched uranium (LEU) core described by Ilas and Primm has been performed and is presented herein. The analyses documented herein support the conclusion that conversion of HFIR to low-enriched uranium (LEU) core operations using the LEU core design of Ilas and Primm will have no negative impact on HFIR RV dpa rates. Since its inception, HFIR has been operated with highly enriched uranium (HEU) cores. As part of an effort sponsored by the National Nuclear Security Administration (NNSA), conversion to LEU cores is being considered for future HFIR operations. The HFIR LEU configurations analyzed are consistent with the LEU core models used by Ilas and Primm and the HEU balance-of-plant models used by Risner and Blakeman in the latest analyses performed to support the HFIR materials surveillance program. The Risner and Blakeman analyses, as well as the studies documented herein, are the first to apply the hybrid transport methods available in the Automated Variance reduction Generator (ADVANTG) code to HFIR RV dpa rate calculations. These calculations have been performed on the Oak Ridge National Laboratory (ORNL) Institutional Cluster (OIC) with version 1.60 of the Monte Carlo N-Particle 5 (MCNP5) computer code.
Energy Technology Data Exchange (ETDEWEB)
Jain, Prashant K [ORNL; Freels, James D [ORNL; Cook, David Howard [ORNL
2012-08-01
Three dimensional simulation capabilities are currently being developed at Oak Ridge National Laboratory using COMSOL Multiphysics, a finite element modeling software, to investigate thermal expansion of High Flux Isotope Reactor (HFIR) s low enriched uranium fuel plates. To validate simulations, 3D models have also been developed for the experimental setup used by Cheverton and Kelley in 1968 to investigate the buckling and thermal deflections of HFIR s highly enriched uranium fuel plates. Results for several simulations are presented in this report, and comparisons with the experimental data are provided when data are available. A close agreement between the simulation results and experimental findings demonstrates that the COMSOL simulations are able to capture the thermal expansion physics accurately and that COMSOL could be deployed as a predictive tool for more advanced computations at realistic HFIR conditions to study temperature-induced fuel plate deflection behavior.
Transmutation-induced embrittlement of V-Ti-Ni and V-Ni alloys in HFIR
Energy Technology Data Exchange (ETDEWEB)
Ohnuki, S.; Takahashi, H. [Hokkaido Univ., Sapparo (Japan); Garner, F.A. [Pacific Northwest National Laboratory, Richland, WA (United States); Pawel, J.E. [Oak Ridge National Laboratory, TN (United States)] [and others
1996-04-01
Vanadium, V-1Ni, V-10Ti and V-10Ti-1Ni (at %) were irradiated in HFIR to doses ranging from 18 to 30 dpa and temperatures between 300 and 600C. Since the irradiation was conducted in a highly thermalized neutron spectrum without shielding against thermal neutrons, significant levels of chromium (15-22%) were formed by transmutation. The addition of such large chromium levels strongly elevated the ductile to brittle transition temperature. At higher irradiation temperatures radiation-induced segregation of transmutant Cr and solute Ti at specimen surfaces leads to strong increases in the density of the alloy.
Post irradiation tensile and fatigue behavior of austenitic PCA stainless steels irradiated in HFIR
Tanaka, M. P.; Hamada, S.; Hishinuma, A.; Grossbeck, M. L.
1988-07-01
Mechanical properties were determined on solution annealed (SA) and cold worked (CW) JPCA (Ti-modified austenitic stainless steel) irradiated in the High Flux Isotope Reactor (HFIR) at temperatures ranging from 300 to 600°C. The irradiation produced damage levels from 16 to 56 dpa and helium concentration from 1020 to 4100 appm. The improved stability of MC precipitates which formed in the matrix during irradiation prevent loss of ductility at 500°C and below. Application of solution annealed JPCA is recommended for structural components of fusion reactors to be operated at 500°C and below.
Energy Technology Data Exchange (ETDEWEB)
Slater, CO
2005-09-08
To aid in the determinations of reactivity worths for target materials in a proposed High Flux Isotope Reactor (HFIR) target configuration containing two additional hydraulic tubes, the worths of cadmium rabbits within the current hydraulic tube were calculated using a reference model of the HFIR and the MCNP5 computer code. The worths were compared to measured worths for both static and ejection experiments. After accounting for uncertainties in the calculations and the measurements, excellent agreement between the two was obtained. Computational and measurement limitations indicate that accurate estimation of worth is only possible when the worth exceeds 10 cents. Results indicate that MCNP5 and the reactor model can be used to predict reactivity worths of various samples when the expected perturbations are greater than 10 cents. The level of agreement between calculation and experiment indicates that the accuracy of such predictions would be dependent solely on the quality of the nuclear data for the materials to be irradiated. Transients that are approximated by ''piecewise static'' computational models should likewise have an accuracy that is dependent solely on the quality of the nuclear data.
Final report of the HFIR (High Flux Isotope Reactor) irradiation facilities improvement project
Energy Technology Data Exchange (ETDEWEB)
Montgomery, B.H.; Thoms, K.R.; West, C.D.
1987-09-01
The High-Flux Isotope Reactor (HFIR) has outstanding neutronics characteristics for materials irradiation, but some relatively minor aspects of its mechanical design severely limited its usefulness for that purpose. In particular, though the flux trap region in the center of the annular fuel elements has a very high neutron flux, it had no provision for instrumentation access to irradiation capsules. The irradiation positions in the beryllium reflector outside the fuel elements also have a high flux; however, although instrumented, they were too small and too few to replace the facilities of a materials testing reactor. To address these drawbacks, the HFIR Irradiation Facilities Improvement Project consisted of modifications to the reactor vessel cover, internal structures, and reflector. Two instrumented facilities were provided in the flux trap region, and the number of materials irradiation positions in the removable beryllium (RB) was increased from four to eight, each with almost twice the available experimental space of the previous ones. The instrumented target facilities were completed in August 1986, and the RB facilities were completed in June 1987.
Preliminary Evaluation of Alternate Designs for HFIR Low-Enriched Uranium Fuel
Energy Technology Data Exchange (ETDEWEB)
Renfro, David G [ORNL; Chandler, David [ORNL; Cook, David Howard [ORNL; Ilas, Germina [ORNL; Jain, Prashant K [ORNL; Valentine, Jennifer R [ORNL
2014-11-01
Engineering design studies of the feasibility of conversion of the High Flux Isotope Reactor (HFIR) from high-enriched uranium (HEU) to low-enriched uranium (LEU) fuel are ongoing at Oak Ridge National Laboratory (ORNL) as part of an effort sponsored by the U.S. Department of Energy s Global Threat Reduction Initiative (GTRI)/Reduced Enrichment for Research and Test Reactors (RERTR) program. The fuel type selected by the program for the conversion of the five high-power research reactors in the U.S. that still use HEU fuel is a new U-Mo monolithic fuel. Studies by ORNL have previously indicated that HFIR can be successfully converted using the new fuel provided (1) the reactor power can be increased from 85 MW to 100 MW and (2) the fuel can be fabricated to a specific reference design. Fabrication techniques for the new fuel are under development by the program but are still immature, especially for the complex aspects of the HFIR fuel design. In FY 2012, the program underwent a major shift in focus to emphasize developing and qualifying processes for the fabrication of reliable and affordable LEU fuel. In support of this new focus and in an effort to ensure that the HFIR fuel design is as suitable for reliable fabrication as possible, ORNL undertook the present study to propose and evaluate several alternative design features. These features include (1) eliminating the fuel zone axial contouring in the previous reference design by substituting a permanent neutron absorber in the lower unfueled region of all of the fuel plates, (2) relocating the burnable neutron absorber from the fuel plates of the inner fuel element to the side plates of the inner fuel element (the fuel plates of the outer fuel element do not contain a burnable absorber), (3) relocating the fuel zone inside the fuel plate to be centered on the centerline of the depth of the plate, and (4) reshaping the radial contour of the relocated fuel zone to be symmetric about this centerline. The present
Preliminary Evaluation of Alternate Designs for HFIR Low-Enriched Uranium Fuel
Energy Technology Data Exchange (ETDEWEB)
Renfro, David [ORNL; Chandler, David [ORNL; Cook, David [ORNL; Ilas, Germina [ORNL; Jain, Prashant [ORNL; Valentine, Jennifer [ORNL
2014-10-30
Engineering design studies of the feasibility of conversion of the High Flux Isotope Reactor (HFIR) from high-enriched uranium (HEU) to low-enriched uranium (LEU) fuel are ongoing at Oak Ridge National Laboratory (ORNL) as part of an effort sponsored by the U.S. Department of Energy’s Global Threat Reduction Initiative (GTRI)/Reduced Enrichment for Research and Test Reactors (RERTR) program. The fuel type selected by the program for the conversion of the five high-power research reactors in the U.S. that still use HEU fuel is a new U-Mo monolithic fuel. Studies by ORNL have previously indicated that HFIR can be successfully converted using the new fuel provided (1) the reactor power can be increased from 85 MW to 100 MW and (2) the fuel can be fabricated to a specific reference design. Fabrication techniques for the new fuel are under development by the program but are still immature, especially for the “complex” aspects of the HFIR fuel design. In FY 2012, the program underwent a major shift in focus to emphasize developing and qualifying processes for the fabrication of reliable and affordable LEU fuel. In support of this new focus and in an effort to ensure that the HFIR fuel design is as suitable for reliable fabrication as possible, ORNL undertook the present study to propose and evaluate several alternative design features. These features include (1) eliminating the fuel zone axial contouring in the previous reference design by substituting a permanent neutron absorber in the lower unfueled region of all of the fuel plates, (2) relocating the burnable neutron absorber from the fuel plates of the inner fuel element to the side plates of the inner fuel element (the fuel plates of the outer fuel element do not contain a burnable absorber), (3) relocating the fuel zone inside the fuel plate to be centered on the centerline of the depth of the plate, and (4) reshaping the radial contour of the relocated fuel zone to be symmetric about this centerline. The
Energy Technology Data Exchange (ETDEWEB)
Sawai, T.; Shiba, K.; Hishinuma, A.
1996-04-01
Austenitic stainless steels, including specimens taken from various electron beam (EB) welds, have been irradiated in HFIR Phase II capsules, JP9-16. Fifteen specimens irradiated at 300, 400, and 500{degrees}C up to 17 dpa are so far examined by a transmission electron microscope (TEM). In 300{degrees}C irradiation, cavities were smaller than 2nm and different specimens showed little difference in cavity microstructure. At 400{degrees}C, cavity size was larger, but still very small (<8 nm). At 500{degrees}C, cavity size reached 30 nm in weld metal specimens of JPCA, while cold worked JPCA contained a small (<5 nm) cavities. Inhomogeneous microstructural evolution was clearly observed in weld-metal specimens irradiated at 500{degrees}C.
2D Thermal Hydraulic Analysis and Benchmark in Support of HFIR LEU Conversion using COMSOL
Energy Technology Data Exchange (ETDEWEB)
Freels, James D [ORNL; Bodey, Isaac T [ORNL; Lowe, Kirk T [ORNL; Arimilli, Rao V [ORNL
2010-09-01
The research documented herein was funded by a research contract between the Research Reactors Division (RRD) of Oak Ridge National Laboratory (ORNL) and the University of Tennessee, Knoxville (UTK) Mechanical, Aerospace and Biomedical Engineering Department (MABE). The research was governed by a statement of work (SOW) which clearly defines nine specific tasks. This report is outlined to follow and document the results of each of these nine specific tasks. The primary goal of this phase of the research is to demonstrate, through verification and validation methods, that COMSOL is a viable simulation tool for thermal-hydraulic modeling of the High Flux Isotope Reactor (HFIR) core. A secondary goal of this two-dimensional phase of the research is to establish methodology and data base libraries that are also needed in the full three-dimensional COMSOL simulation to follow. COMSOL version 3.5a was used for all of the models presented throughout this report.
Saturation behavior of irradiation hardening in F82H irradiated in the HFIR
Energy Technology Data Exchange (ETDEWEB)
Hirose, T. [Blanket Engineering Group, Japan Atomic Energy Agency, Naka, Ibaraki (Japan); Shiba, K.; Tanigawa, H.; Ando, M. [Japan Atomic Energy Agency, Tokai-mura, Naga-gun, Ibaraki-ken (Japan); Klueh, R.L. [Oak Ridge National Laboratory, TN (United States); Stoller, R. [ORNL - Oak Ridge National Laboratory, Materials Science and Technology Div., Oak Ridge, AK TN (United States)
2007-07-01
Full text of publication follows: Post irradiation tensile tests on reduced activation ferritic/martensitic steel, F82H have been conducted over the past two decades using Japan Materials Testing Reactor (JMTR) of JAEA, and Fast Flux Testing Facility (FFTF) of PNNL and High Flux Isotope Reactor (HFIR) of ORNL, USA, under Japan/US collaboration programs. According to these results, F82H does not demonstrate irradiation hardening above 673 K up to 60 dpa. The current study has been concentrated on hardening behavior at temperature around 573 K. A series of low temperature irradiation experiment has been conducted at the HFIR under the international collaborative research between JAEA/US-DOE. In this collaboration, the irradiation condition is precisely controlled by the well matured capsule designing and instrumentation. This paper summarizes recent results of the irradiation experiments focused on F82H and its modified steels compared with the irradiation properties database on F82H. Post irradiation tensile tests have been conducted on the F82H and its modified steels irradiated at 573 K and the dose level was up to 25 dpa. According to these results, irradiation hardening of F82H is saturated by 9 dpa and the as-irradiated 0.2 % proof stress is less than 1 GPa at ambient temperature. The deterioration of total elongation was also saturated by 9 dpa irradiation. The ductility of some modified steels which showed larger total elongation than that of F82H before irradiation become the same level as that of standard F82H steel after irradiation, even though its magnitude of irradiation hardening is smaller than that of F82H. This suggests that the more ductile steel demonstrates the more ductility loss at this temperature, regardless to the hardening level. The difference in ductility loss behavior between various tensile specimens will be discussed as the ductility could depend on the specimen dimension. (authors)
Energy Technology Data Exchange (ETDEWEB)
Bucholz, J.A.
2000-07-01
The High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory is in the midst of a massive upgrade program to enhance experimental facilities. The reactor presently has four horizontal experimental beam tubes, all of which will be replaced or redesigned. The HB-2 beam tube will be enlarged to support more guide tubes, while the HB-4 beam tube will soon include a cold neutron source.
Analysis of dpa Rates in the HFIR Reactor Vessel using a Hybrid Monte Carlo/Deterministic Method*
Directory of Open Access Journals (Sweden)
Risner J.M.
2016-01-01
Full Text Available The Oak Ridge High Flux Isotope Reactor (HFIR, which began full-power operation in 1966, provides one of the highest steady-state neutron flux levels of any research reactor in the world. An ongoing vessel integrity analysis program to assess radiation-induced embrittlement of the HFIR reactor vessel requires the calculation of neutron and gamma displacements per atom (dpa, particularly at locations near the beam tube nozzles, where radiation streaming effects are most pronounced. In this study we apply the Forward-Weighted Consistent Adjoint Driven Importance Sampling (FW-CADIS technique in the ADVANTG code to develop variance reduction parameters for use in the MCNP radiation transport code. We initially evaluated dpa rates for dosimetry capsule locations, regions in the vicinity of the HB-2 beamline, and the vessel beltline region. We then extended the study to provide dpa rate maps using three-dimensional cylindrical mesh tallies that extend from approximately 12 in. below to approximately 12 in. above the height of the core. The mesh tally structures contain over 15,000 mesh cells, providing a detailed spatial map of neutron and photon dpa rates at all locations of interest. Relative errors in the mesh tally cells are typically less than 1%.
Analysis of dpa rates in the HFIR reactor vessel using a hybrid Monte Carlo/deterministic method
Energy Technology Data Exchange (ETDEWEB)
Blakeman, Edward [Retired
2016-01-01
The Oak Ridge High Flux Isotope Reactor (HFIR), which began full-power operation in 1966, provides one of the highest steady-state neutron flux levels of any research reactor in the world. An ongoing vessel integrity analysis program to assess radiation-induced embrittlement of the HFIR reactor vessel requires the calculation of neutron and gamma displacements per atom (dpa), particularly at locations near the beam tube nozzles, where radiation streaming effects are most pronounced. In this study we apply the Forward-Weighted Consistent Adjoint Driven Importance Sampling (FW-CADIS) technique in the ADVANTG code to develop variance reduction parameters for use in the MCNP radiation transport code. We initially evaluated dpa rates for dosimetry capsule locations, regions in the vicinity of the HB-2 beamline, and the vessel beltline region. We then extended the study to provide dpa rate maps using three-dimensional cylindrical mesh tallies that extend from approximately 12 below to approximately 12 above the axial extent of the core. The mesh tally structures contain over 15,000 mesh cells, providing a detailed spatial map of neutron and photon dpa rates at all locations of interest. Relative errors in the mesh tally cells are typically less than 1%.
Energy Technology Data Exchange (ETDEWEB)
Knapp, F.F. Jr.; Beets, A.L.; Mirzadeh, S.; Alexander, C.W.; Hobbs, R.L.
1998-06-01
The High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory (ORNL) represents an important resource for the production of a wide variety of medical radioisotopes. In addition to serving as a key production site for californium-252 and other transuranic elements, important examples of therapeutic radioisotopes which are currently routinely produced in the HFIR for distribution include dysprosium-166 (parent of holmium-166), rhenium-186, tin-117m and tungsten-188 (parent of rhenium-188). The nine hydraulic tube (HT) positions in the central high flux region permit the insertion and removal of targets at any time during the operating cycle and have traditionally represented a major site for production of medical radioisotopes. To increase the irradiation capabilities of the HFIR, special target holders have recently been designed and fabricated which will be installed in the six Peripheral Target Positions (PTP), which are also located in the high flux region. These positions are only accessible during reactor refueling and will be used for long-term irradiations, such as required for the production of tin-117m and tungsten-188. Each of the PTP tubes will be capable of housing a maximum of eight HT targets, thus increasing the total maximum number of HT targets from the current nine, to a total of 57. In this paper the therapeutic use of reactor-produced radioisotopes for bone pain palliation and vascular brachytherapy and the therapeutic medical radioisotope production capabilities of the ORNL HFIR are briefly discussed.
Tensile properties of V-(4-15)Cr-5Ti alloys irradiated at 400{degrees}C in the HFIR
Energy Technology Data Exchange (ETDEWEB)
Chung, H.M.; Nowicki, L.; Smith, D.L. [Argonne National Lab., IL (United States)
1996-10-01
V-(4-15)Cr-5Ti alloys were irradiated in a helium environment to {approx}10 dpa at {approx}400{degrees}C in the High Flux Isotope Reactor (HFIR). This report presents results of postirradiation tests of tensile properties of V-4Cr-4Ti, V-8Cr-6Ti, V-10Cr-5Ti, and V-15Cr-5Ti. Despite concerns on the effects of transmutation of vanadium to Cr and impurity pickup from the helium environment, all of the alloys exhibited ductile tensile behavior. However, the alloys exhibited ductilities somewhat lower than those of the specimens irradiated to a similar dose and at a similar temperature in an Li environment in fast reactors. Uniform plastic strain in the V-Cr-(4-5)Ti alloys decreased monotonically with increasing Cr content.
Knapp, F. F.; Beets, A. L.; Mirzadeh, S.; Alexander, C. W.; Hobbs, R. L.
1999-01-01
The High Flux Isotope Reactor ( HFIR) at the Oak Ridge National Laboratory ( ORNL) represents an important resource for the production of a wide variety of medical radioisotopes. First beginning operation in 1965, the high thermal neutron flux (2.5×1015 neutrons/cm2/sec at 85 MW) and versatile target irradiation and handling facilities provide the opportunity for production of a wide variety of neutron-rich medical radioisotopes of current interest for therapy. In addition to serving as a key production site for californium-252 and other transuranic elements, important examples of therapeutic radioisotopes which are currently routinely produced in the HFIR for distribution include dysprosium-166 (parent of holmium-166), rhenium-186, tin-117 m and tungsten-188 (parent of rhenium-188). The nine hydraulic tube ( HT) positions in the central high flux region permit the insertion and removal of targets at any time during the operating cycle (22-24 days) and have traditionally represented a major site for production of medical radioisotopes. To increase the irradiation capabilities of the HFIR, special target holders have recently been designed and fabricated which will be installed in the six Peripheral Target Positions ( PTP), which are also located in the high flux region. These positions are only accessible during reactor refueling and will be used for long-term irradiations, such as required for the production of tin-117 m and tungsten-188. Each of the PTP tubes will be capable of housing a maximum of eight HT targets, thus increasing the total maximum number of HT targets from the current nine, to a total of 57. In this paper the therapeutic use of reactor-produced radioisotopes for bone pain palliation and vascular brachytherapy and the therapeutic medical radioisotope production capabilities of the ORNL HFIR are briefly discussed.
M3FT-16OR0203052-Test Design for FeCrAl Alloy Tube Irradiation in HFIR
Energy Technology Data Exchange (ETDEWEB)
Terrani, Kurt A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Petrie, Christian M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2016-05-01
This calculation summarizes thermal analyses of a flexible rabbit design for irradiating a variety of pressurized water reactor (PWR) cladding materials (stainless steel, iron-chromium aluminum [FeCrAl], Zircaloy, and Inconel) with variable dimensions at a temperature of 350 °C in the flux trap of the High Flux Isotope Reactor (HFIR). The design can accommodate standard cladding for outer diameters (ODs) of approximately 9.50 mm with thickness ranging from 0.30 mm to 0.70 mm. The length is generally between 10 and 50 mm. The specimens contain moly inserts with a variable OD that provides the heat flux necessary to achieve the design temperature with such a small fixed gas gap. The primary outer containment is an Al-6061 housing with a slightly enlarged inner diameter (ID) of 9.60 mm. The specimen temperature is controlled by determining a helium/argon gas mixture specific to the as-built specimen and housing. Variables that affect the required gas mixture are the cladding material (thermal expansion, density, heat generation rate), cladding OD, housing ID, and cladding ID. This calculation documents the analyses performed to determine required gas mixtures for a variety of scenarios.
Energy Technology Data Exchange (ETDEWEB)
Billone, M.C. [Argonne National Lab., IL (United States)
1998-03-01
The tensile data for all unirradiated and irradiated vanadium alloys samples tested at Argonne National Laboratory (ANL) have been critically reviewed and, when necessary, revised. The review and revision are based on reanalyzing the original load-displacement strip chart recordings by a methodology consistent with current ASTM standards. For unirradiated alloys (162 samples), the revised values differ from the previous values as follows: {minus}11{+-}19 MPa ({minus}4{+-}6%) for yield strength (YS), {minus}3{+-}15 MPa ({minus}1{+-}3%) for ultimate tensile strength (UTS), {minus}5{+-}2% strain for uniform elongation (UE), and {minus}4{+-}2% strain for total elongation (TE). Of these changes, the decrease in {minus}1{+-}6 MPa (0{+-}1%) for UTS, {minus}5{+-}2% for UE, and {minus}4{+-}2% for TE. Of these changes, the decrease in UE values for alloys irradiated and tested at 400--435 C is the most significant. This decrease results from the proper subtraction of nongauge-length deformation from measured crosshead deformation. In previous analysis of the tensile curves, the nongauge-length deformation was not correctly determined and subtracted from the crosshead displacement. The previously reported and revised tensile values for unirradiated alloys (20--700 C) are tabulated in Appendix A. The revised tensile values for the FFTF-irradiated (400--600 C) and HFIR-irradiated (400 C) alloys are tabulated in Appendix B, along with the neutron damage and helium levels. Appendix C compares the revised values to the previously reported values for irradiated alloys. Appendix D contains previous and revised values for the tensile properties of unirradiated V-5Cr-5Ti (BL-63) alloy exposed to oxygen.
Smoothly Varying Bright Blazars
Van Alfen, Nicholas; Hindman, Lauren; Moody, Joseph Ward; Biancardi, Rochelle; Whipple, Parkes; Gaunt, Caleb
2018-01-01
It is becoming increasingly apparent that blazar light can vary sinusoidally with periods of hundreds of days to tens of years. Such behavior is expected of, among other things, jets coming from binary black holes. To look for general variability in lesser-known blazars and AGN, in 2015-2016 we monitored 182 objects with Johnson V-band magnitudes reported as being < 16. In all, this campaign generated 22,000 frames from 2,000 unique pointings. We find that approximately one dozen of these objects show evidence of smooth variability consistent with sinusoidal periods. We report on the entire survey sample, highlighting those that show sinusoidal variations.
varying elastic parameters distributions
Moussawi, Ali
2014-12-01
The experimental identication of mechanical properties is crucial in mechanics for understanding material behavior and for the development of numerical models. Classical identi cation procedures employ standard shaped specimens, assume that the mechanical elds in the object are homogeneous, and recover global properties. Thus, multiple tests are required for full characterization of a heterogeneous object, leading to a time consuming and costly process. The development of non-contact, full- eld measurement techniques from which complex kinematic elds can be recorded has opened the door to a new way of thinking. From the identi cation point of view, suitable methods can be used to process these complex kinematic elds in order to recover multiple spatially varying parameters through one test or a few tests. The requirement is the development of identi cation techniques that can process these complex experimental data. This thesis introduces a novel identi cation technique called the constitutive compatibility method. The key idea is to de ne stresses as compatible with the observed kinematic eld through the chosen class of constitutive equation, making possible the uncoupling of the identi cation of stress from the identi cation of the material parameters. This uncoupling leads to parametrized solutions in cases where 5 the solution is non-unique (due to unknown traction boundary conditions) as demonstrated on 2D numerical examples. First the theory is outlined and the method is demonstrated in 2D applications. Second, the method is implemented within a domain decomposition framework in order to reduce the cost for processing very large problems. Finally, it is extended to 3D numerical examples. Promising results are shown for 2D and 3D problems.
Einstein Equations from Varying Complexity
Czech, Bartłomiej
2018-01-01
A recent proposal equates the circuit complexity of a quantum gravity state with the gravitational action of a certain patch of spacetime. Since Einstein's equations follow from varying the action, it should be possible to derive them by varying complexity. I present such a derivation for vacuum solutions of pure Einstein gravity in three-dimensional asymptotically anti-de Sitter space. The argument relies on known facts about holography and on properties of tensor network renormalization, an algorithm for coarse-graining (and optimizing) tensor networks.
INFLUENCE OF SUPERPLASTICIZER AND VARYING ...
African Journals Online (AJOL)
This paper presents the results of the study on the influence of superplasticizer and varying aggregate size on the drying shrinkage and compressive strength of laterised concrete. Four different samples of laterised concrete were made from prescribed mix ratio of 1:1:2 which include; two control specimens made with ...
Optimistlik Karlovy Vary / Jaan Ruus
Ruus, Jaan, 1938-2017
2007-01-01
42. Karlovy Vary rahvusvahelise filmifestivali auhinnatud filmidest (žürii esimees Peter Bart). Kristallgloobuse sai Islandi-Saksamaa "Katseklaasilinn" (režii Baltasar Kormakur), parimaks režissööriks tunnistati norralane Bard Breien ("Negatiivse mõtlemise kunst"). Austraallase Michael James Rowlandi "Hea õnne teekond" sai žürii eripreemia
Esmaklassiline Karlovy Vary / Jaanus Noormets
Noormets, Jaanus
2007-01-01
Ilmar Raagi mängufilm "Klass" võitis 42. Karlovy Vary rahvusvahelise filmifestivalil kaks auhinda - ametliku kõrvalvõistlusprogrammi "East of the West" eripreemia "Special mention" ja Euroopa väärtfilmikinode keti Europa Cinemas preemia. Ka Asko Kase lühifilmi "Zen läbi prügi linastumisest ning teistest auhinnasaajatest ning osalejatest
DEFF Research Database (Denmark)
Christoffersen, Peter; Feunoua, Bruno; Jeon, Yoontae
We estimate a continuous-time model with stochastic volatility and dynamic crash probability for the S&P 500 index and find that market illiquidity dominates other factors in explaining the stock market crash risk. While the crash probability is time-varying, its dynamic depends only weakly...
Eestlased Karlovy Varys / J. R.
J. R.
2007-01-01
Ilmar Raagi mängufilm "Klass" osaleb 42. Karlovy Vary rahvusvahelise filmifestivali võistlusprogrammis "East of the West" ja Asko Kase lühimängufilm "Zen läbi prügi" on valitud festivali kõrvalprogrammi "Forum of Independents"
Harmonic functions with varying coefficients
Directory of Open Access Journals (Sweden)
Jacek Dziok
2016-05-01
Full Text Available Abstract Complex-valued harmonic functions that are univalent and sense preserving in the open unit disk can be written in the form f = h + g ‾ $f=h+\\overline{g}$ , where h and g are analytic. In this paper we investigate some classes of univalent harmonic functions with varying coefficients related to Janowski functions. By using the extreme points theory we obtain necessary and sufficient convolution conditions, coefficients estimates, distortion theorems, and integral mean inequalities for these classes of functions. The radii of starlikeness and convexity for these classes are also determined.
Varying Constants, Gravitation and Cosmology.
Uzan, Jean-Philippe
2011-01-01
Fundamental constants are a cornerstone of our physical laws. Any constant varying in space and/or time would reflect the existence of an almost massless field that couples to matter. This will induce a violation of the universality of free fall. Thus, it is of utmost importance for our understanding of gravity and of the domain of validity of general relativity to test for their constancy. We detail the relations between the constants, the tests of the local position invariance and of the universality of free fall. We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, solar system observations, meteorite dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic microwave background and big bang nucleosynthesis. At each step we describe the basics of each system, its dependence with respect to the constants, the known systematic effects and the most recent constraints that have been obtained. We then describe the main theoretical frameworks in which the low-energy constants may actually be varying and we focus on the unification mechanisms and the relations between the variation of different constants. To finish, we discuss the more speculative possibility of understanding their numerical values and the apparent fine-tuning that they confront us with.
Varying Constants, Gravitation and Cosmology
Directory of Open Access Journals (Sweden)
Jean-Philippe Uzan
2011-03-01
Full Text Available Fundamental constants are a cornerstone of our physical laws. Any constant varying in space and/or time would reflect the existence of an almost massless field that couples to matter. This will induce a violation of the universality of free fall. Thus, it is of utmost importance for our understanding of gravity and of the domain of validity of general relativity to test for their constancy. We detail the relations between the constants, the tests of the local position invariance and of the universality of free fall. We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, solar system observations, meteorite dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic microwave background and big bang nucleosynthesis. At each step we describe the basics of each system, its dependence with respect to the constants, the known systematic effects and the most recent constraints that have been obtained. We then describe the main theoretical frameworks in which the low-energy constants may actually be varying and we focus on the unification mechanisms and the relations between the variation of different constants. To finish, we discuss the more speculative possibility of understanding their numerical values and the apparent fine-tuning that they confront us with.
Barrow, John D
2014-01-01
In a recent paper we demonstrated how the simplest model for varying alpha may be interpreted as the effect of a dielectric material, generalized to be consistent with Lorentz invariance. Unlike normal dielectrics, such a medium cannot change the speed of light, and its dynamics obey a Klein-Gordon equation. This work immediately suggests an extension of the standard theory, even if we require compliance with Lorentz invariance. Instead of a wave equation, the dynamics may satisfy a local algebraic relation involving the permittivity and the properties of the electromagnetic field, in analogy with more conventional dielectric (but still preserving Lorentz invariance). We develop the formalism for such theories and investigate some phenomenological implications. The problem of the divergence of the classical self-energy can be solved, or at least softened, in this framework. Some interesting new cosmological solutions for the very early universe are found, including the possibility of a bounce, inflation and e...
Weighted approximation with varying weight
Totik, Vilmos
1994-01-01
A new construction is given for approximating a logarithmic potential by a discrete one. This yields a new approach to approximation with weighted polynomials of the form w"n"(" "= uppercase)P"n"(" "= uppercase). The new technique settles several open problems, and it leads to a simple proof for the strong asymptotics on some L p(uppercase) extremal problems on the real line with exponential weights, which, for the case p=2, are equivalent to power- type asymptotics for the leading coefficients of the corresponding orthogonal polynomials. The method is also modified toyield (in a sense) uniformly good approximation on the whole support. This allows one to deduce strong asymptotics in some L p(uppercase) extremal problems with varying weights. Applications are given, relating to fast decreasing polynomials, asymptotic behavior of orthogonal polynomials and multipoint Pade approximation. The approach is potential-theoretic, but the text is self-contained.
Diurnally-Varying Lunar Hydration
Hendrix, A. R.; Hurley, D.; Retherford, K. D.; Mandt, K.; Greathouse, T. K.; Farrell, W. M.; Vilas, F.
2016-12-01
Dayside, non-polar lunar hydration signatures have been observed by a handful of instruments and present insights into the lunar water cycle. In this study, we utilize the unique measurements from the current Lunar Reconnaissance Orbiter (LRO) mission to study the phenomenon of diurnally-varying dayside lunar hydration. The Lyman Alpha Mapping Project (LAMP) onboard LRO senses a strong far-ultraviolet water absorption edge indicating hydration in small abundances in the permanently shadowed regions as well as on the lunar dayside. We report on diurnal variability in hydration in different terrain types. We investigate the importance of different sources of hydration, including solar wind bombardment and meteoroid bombardment, by observing trends during magnetotail and meteor stream crossings.
Gait phase varies over velocities.
Liu, Yancheng; Lu, Kun; Yan, Songhua; Sun, Ming; Lester, D Kevin; Zhang, Kuan
2014-02-01
We sought to characterize the percent (PT) of the phases of a gait cycle (GC) as velocity changes to establish norms for pathological gait characteristics with higher resolution technology. Ninety five healthy subjects (49 males and 46 females with age 34.9 ± 11.8 yrs, body weight 64.0 ± 11.7 kg and BMI 23.5 ± 3.6) were enrolled and walked comfortably on a 10-m walkway at self-selected slower, normal, and faster velocities. Walking was recorded with a high speed camera (250 frames per second) and the eight phases of a GC were determined by examination of individual frames for each subject. The correlation coefficients between the mean PT of the phases of the three velocities gaits and PT defined by previous publications were all greater than 0.99. The correlation coefficient between velocity and PT of gait phases is -0.83 for loading response (LR), -0.75 for mid stance (MSt), and -0.84 for pre-swing (PSw). While the PT of the phases of three velocities from this study are highly correlated with PT described by Dr. Jacquenlin Perry decades ago, actual PT of each phase varied amongst these individuals with the largest coefficient variation of 24.31% for IC with slower velocity. From slower to faster walk, the mean PT of MSt diminished from 35.30% to 25.33%. High resolution recording revealed ambiguity of some gait phase definitions, and these data may benefit GC characterization of normal and pathological gait in clinical practice. The study results indicate that one should consider individual variations and walking velocity when evaluating gaits of subjects using standard gait phase classification. Copyright © 2013 Elsevier B.V. All rights reserved.
Matching Value Propositions with Varied Customer Needs
DEFF Research Database (Denmark)
Heikka, Eija-Liisa; Frandsen, Thomas; Hsuan, Juliana
2018-01-01
Organizations seek to manage varied customer segments using varied value propositions. The ability of a knowledge-intensive business service (KIBS) provider to formulate value propositions into attractive offerings to varied customers becomes a competitive advantage. In this specific business bas...
Tavatult jahe Karlovy Vary / Jaanus Noormets
Noormets, Jaanus
2011-01-01
1.-10. juulini toimunud Karlovy Vary 46. filmifestivalist (muusikafilmide alajaotuses näidati Marianne Kõrveri dokumentaalfilmi "Erkki-Sven Tüür: 7 etüüdi piltides" (2010) programmis "A Musical Odyssey")
Eesti film võistleb Karlovy Varys
2008-01-01
8. juulil esilinastub Karlovy Vary filmifestivalil Rene Vilbre noortefilm "Mina olin siin", mille aluseks on Sass Henno romaan "Mina olin siin. Esimene arest", stsenaariumi kirjutas Ilmar Raag. Film võistleb võistlusprogrammis "East of the West"
Rumor Detection over Varying Time Windows
National Research Council Canada - National Science Library
Sejeong Kwon; Meeyoung Cha; Kyomin Jung
2017-01-01
This study determines the major difference between rumors and non-rumors and explores rumor classification performance levels over varying time windows--from the first three days to nearly two months...
Compilation of Instantaneous Source Functions for Varying ...
African Journals Online (AJOL)
Compilation of Instantaneous Source Functions for Varying Architecture of a Layered Reservoir with Mixed Boundaries and Horizontal Well Completion Part IV: Normal and Inverted Letter 'h' and 'H' Architecture.
Compilation of Instantaneous Source Functions for Varying ...
African Journals Online (AJOL)
Compilation of Instantaneous Source Functions for Varying Architecture of a Layered Reservoir with Mixed Boundaries and Horizontal Well Completion Part III: B-Shaped Architecture with Vertical Well in the Upper Layer.
Arthritis Mechanisms May Vary by Joint
... Issues Subscribe August 2016 Print this issue Arthritis Mechanisms May Vary by Joint En español Send us ... joints have unique patterns of chemical tags—called epigenetic markers—that differ between rheumatoid arthritis and osteoarthritis. ...
Digital repetitive control under varying frequency conditions
Ramos, Germán A; Olm, Josep M
2013-01-01
The tracking/rejection of periodic signals constitutes a wide field of research in the control theory and applications area. Repetitive Control has proven to be an efficient way to face this topic. However, in some applications the frequency of the reference/disturbance signal is time-varying or uncertain. This causes an important performance degradation in the standard Repetitive Control scheme. This book presents some solutions to apply Repetitive Control in varying frequency conditions without loosing steady-state performance. It also includes a complete theoretical development and experimental results in two representative systems. The presented solutions are organized in two complementary branches: varying sampling period Repetitive Control and High Order Repetitive Control. The first approach allows dealing with large range frequency variations while the second allows dealing with small range frequency variations. The book also presents applications of the described techniques to a Roto-magnet plant and...
Varying flexibilities in systems of organised decentralisation
DEFF Research Database (Denmark)
Ilsøe, Anna; Andersen, Søren Kaj
be while the response of the German system should rather be interpreted as a reactive organised decentralisation. 3) The varying regulation of working time flexibility in Germany and Denmark implies varying risks in the regulation. In Germany lacking competencies in small or medium-sized companies lead...... to this paradox a qualitative study of working time regulation in the metal industry in Denmark and Germany was performed in the spring of 2005. In addition to five case studies of company-based agreements in Denmark and Germany (Baden-Württemberg) the study consisted of analysing statistical data, legislative...
Varying G. [in Einstein gravitation theory
Canuto, V.; Hsieh, S.-H.; Owen, J. R.
1979-01-01
The problem of the variation of the gravitational constant with cosmological time is critically analyzed. Since Einstein's equation does not allow G to vary on any time scale, no observational data can be analyzed within the context of the standard theory. The recently proposed scale covariant theory, which allows (but does not demand) G to vary, and which has been shown to have passed several standard cosmological tests, is employed to discuss some recent nonnull observational results which indicate a time variation of G.
2010-01-01
45. Karlovy Vary filmifestivali võistlusprogrammis "East of the West" märgiti ära Veiko Õunpuu film "Püha Tõnu kiusamine". Peaauhind läks rumeenlase Cristi Puiu filmile "Aurora". Grand prix´sai Augustĺ Vila film "La mosquitera". Teisi preemiasaajaid
RETRACTED ARTICLE: Gradually varied flow computation in ...
Indian Academy of Sciences (India)
Mohammad Jahandar Malekabadi
The article ''Gradually varied flow computation in channel networks by adaptive algorithm'' (DOI 10.1007/s12046- · 017-0640-x) which has been published online has been retracted by Chief Editor of the journal Sadhana as per the. Committee on Publication Ethics (COPE) guidelines on redundant publication.
Ellipsometry with randomly varying polarization states
Liu, Fenz; Lee, Christopher James; Chen, Juequan; Chen, J.; Louis, Eric; van der Slot, Petrus J.M.; Boller, Klaus J.; Bijkerk, Frederik
2012-01-01
We show that, under the right conditions, one can make highly accurate polarization-based measurements without knowing the absolute polarization state of the probing light field. It is shown that light, passed through a randomly varying birefringent material has a well-defined orbit on the Poincar
Ellipsometry with random varying polarization state
Liu, Fenz; van Albada, B.; Lee, c; Bijkerk, Frederik
2012-01-01
We show that, under the right conditions, one can make highly accurate polarization-based measurements without knowing the absolute polarization state of the probing light field. It is shown that light, passed through a randomly varying birefringent material has a well-defined orbit on the Poincar
"Mina olin siin" esilinastub Karlovy Varys
2008-01-01
Karlovy Vary filmifestivalil esilinastub Rene Vilbre noortefilm "Mina olin siin", mille aluseks on Sass Henno romaan "Mina olin siin. Esimene arest", stsenaariumi kirjutas Ilmar Raag. Film võistleb võistlusprogrammis "East of the West". Esitlema sõidavad R. Vilbre, R. Sildos, R. Kaljujärv, T. Tuisk
Tracking time-varying coefficient-functions
DEFF Research Database (Denmark)
Nielsen, Henrik Aalborg; Nielsen, Torben Skov; Joensen, Alfred K.
2000-01-01
is a combination of recursive least squares with exponential forgetting and local polynomial regression. It is argued, that it is appropriate to let the forgetting factor vary with the value of the external signal which is the argument of the coefficient functions. Some of the key properties of the modified method...... are studied by simulation...
Efficient Estimation in Heteroscedastic Varying Coefficient Models
Directory of Open Access Journals (Sweden)
Chuanhua Wei
2015-07-01
Full Text Available This paper considers statistical inference for the heteroscedastic varying coefficient model. We propose an efficient estimator for coefficient functions that is more efficient than the conventional local-linear estimator. We establish asymptotic normality for the proposed estimator and conduct some simulation to illustrate the performance of the proposed method.
Filmihullu eluvesi voolab Karlovy Varys / Margit Tõnson
Tõnson, Margit, 1978-
2010-01-01
Karlovy Vary rahvusvahelisest filmifestivalist. Filmidest "Mr. Nobody" (rež. Jaco Van Dormaeli), "Kasside ema Teresa" (rež. Pawel Sala) ja "The Arbor" (rež. Clio Barnardi). Nimekiri võitnud töödest ja viimastel aastatel festivalil näidatud Eesti mängufilmidest
Components in time-varying graphs
Nicosia, Vincenzo; Tang, John; Musolesi, Mirco; Russo, Giovanni; Mascolo, Cecilia; Latora, Vito
2012-06-01
Real complex systems are inherently time-varying. Thanks to new communication systems and novel technologies, today it is possible to produce and analyze social and biological networks with detailed information on the time of occurrence and duration of each link. However, standard graph metrics introduced so far in complex network theory are mainly suited for static graphs, i.e., graphs in which the links do not change over time, or graphs built from time-varying systems by aggregating all the links as if they were concurrent in time. In this paper, we extend the notion of connectedness, and the definitions of node and graph components, to the case of time-varying graphs, which are represented as time-ordered sequences of graphs defined over a fixed set of nodes. We show that the problem of finding strongly connected components in a time-varying graph can be mapped into the problem of discovering the maximal-cliques in an opportunely constructed static graph, which we name the affine graph. It is, therefore, an NP-complete problem. As a practical example, we have performed a temporal component analysis of time-varying graphs constructed from three data sets of human interactions. The results show that taking time into account in the definition of graph components allows to capture important features of real systems. In particular, we observe a large variability in the size of node temporal in- and out-components. This is due to intrinsic fluctuations in the activity patterns of individuals, which cannot be detected by static graph analysis.
Anistropically varying conductivity in irreversible electroporation simulations.
Labarbera, Nicholas; Drapaca, Corina
2017-11-01
One recent area of cancer research is irreversible electroporation (IRE). Irreversible electroporation is a minimally invasive procedure where needle electrodes are inserted into the body to ablate tumor cells with electricity. The aim of this paper is to propose a mathematical model that incorporates a tissue's conductivity increasing more in the direction of the electrical field as this has been shown to occur in experiments. It was necessary to mathematically derive a valid form of the conductivity tensor such that it is dependent on the electrical field direction and can be easily implemented into numerical software. The derivation of a conductivity tensor that can take arbitrary functions for the conductivity in the directions tangent and normal to the electrical field is the main contribution of this paper. Numerical simulations were performed for isotropic-varying and anisotropic-varying conductivities to evaluate the importance of including the electrical field's direction in the formulation for conductivity. By starting from previously published experimental results, this paper derived a general formulation for an anistropic-varying tensor for implementation into irreversible electroporation modeling software. The anistropic-varying tensor formulation allows the conductivity to take into consideration both electrical field direction and magnitude, as opposed to previous published works that only took into account electrical field magnitude. The anisotropic formulation predicts roughly a five percent decrease in ablation size for the monopolar simulation and approximately a ten percent decrease in ablation size for the bipolar simulations. This is a positive result as previously reported results found the isotropic formulation to overpredict ablation size for both monopolar and bipolar simulations. Furthermore, it was also reported that the isotropic formulation overpredicts the ablation size more for the bipolar case than the monopolar case. Thus, our
A time-varying magnetic flux concentrator
Kibret, B.; Premaratne, M.; Lewis, P. M.; Thomson, R.; Fitzgerald, P. B.
2016-08-01
It is known that diverse technological applications require the use of focused magnetic fields. This has driven the quest for controlling the magnetic field. Recently, the principles in transformation optics and metamaterials have allowed the realization of practical static magnetic flux concentrators. Extending such progress, here, we propose a time-varying magnetic flux concentrator cylindrical shell that uses electric conductors and ferromagnetic materials to guide magnetic flux to its center. Its performance is discussed based on finite-element simulation results. Our proposed design has potential applications in magnetic sensors, medical devices, wireless power transfer, and near-field wireless communications.
Tracking Time-Varying Coefficient-Functions
DEFF Research Database (Denmark)
Nielsen, Henrik Aalborg; Nielsen, Torben Skov; Joensen, Alfred K.
1999-01-01
of recursive least squares with exponential forgetting and local polynomial regression. However, it is argued, that it is appropriate to let the forgetting factor vary with the value of the external signal shich is argument of the coeffieient-functions.The properties of the modified method are sutdied...... by simulation. A particular feature is that this effectiv forgetting factor will adapt to the bandwidth used so that the effective number of observtions behind the estimates will be almost independent of the actual bandwidth or of the type of bandwidth selection used (fixed or nearest neighbour). The choice...
Conceptual Modeling of Time-Varying Information
DEFF Research Database (Denmark)
Gregersen, Heidi; Jensen, Christian Søndergaard
2004-01-01
A wide range of database applications manage information that varies over time. Many of the underlying database schemas of these were designed using the Entity-Relationship (ER) model. In the research community as well as in industry, it is common knowledge that the temporal aspects of the mini-world...... are important, but difficult to capture using the ER model. Several enhancements to the ER model have been proposed in an attempt to support the modeling of temporal aspects of information. Common to the existing temporally extended ER models, few or no specific requirements to the models were given...
Linear Parameter Varying Control of Induction Motors
DEFF Research Database (Denmark)
Trangbæk, Klaus
The subject of this thesis is the development of linear parameter varying (LPV) controllers and observers for control of induction motors. The induction motor is one of the most common machines in industrial applications. Being a highly nonlinear system, it poses challenging control problems...... for high performance applications. This thesis demonstrates how LPV control theory provides a systematic way to achieve good performance for these problems. The main contributions of this thesis are the application of the LPV control theory to induction motor control as well as various contributions...
Stereoscopic depth perception varies with hues
Chen, Zaiqing; Shi, Junsheng; Tai, Yonghang; Yun, Lijun
2012-09-01
The contribution of color information to stereopsis is controversial, and whether the stereoscopic depth perception varies with chromaticity is ambiguous. This study examined the changes in depth perception caused by hue variations. Based on the fact that a greater disparity range indicates more efficient stereoscopic perception, the effect of hue variations on depth perception was evaluated through the disparity range with random-dot stereogram stimuli. The disparity range was obtained by constant-stimulus method for eight chromaticity points sampled from the CIE 1931 chromaticity diagram. Eight sample points include four main color hues: red, yellow, green, and blue at two levels of chroma. The results show that the disparity range for the yellow hue is greater than the red hue, the latter being greater than the blue hue and the disparity range for green hue is smallest. We conclude that the perceived depth is not the same for different hues for a given size of disparity. We suggest that the stereoscopic depth perception can vary with chromaticity.
Optimizing power output by varying repetition tempo.
Pryor, Riana R; Sforzo, Gary A; King, Deborah L
2011-11-01
The effects of varying interrepetition rest and eccentric velocity on power output (PO) and the number of repetitions performed during a bench press set were examined in 24 college-aged resistance trained men. On 6 separate occasions, subjects performed a set of bench press at 80% 1 repetition maximum until volitional fatigue. For each of the 6 repetition tempo trials, the bench press set was paced by metronome to a unique repetition tempo involving a combination of the following: interrepetition rest of 0 or 4 seconds; eccentric velocity of 1 or 4 seconds and bottom rest of 0 or 3 seconds. The velocity of concentric contraction was maximal during all 6 tempo trials. During each trial, video data were captured to determine PO variables and number of successful repetitions completed at each tempo. One-way repeated measures analysis of variance showed tempos with a fast eccentric phase (1 second), and no bottom rest produced significantly greater (p ≤ 0.05) PO and repetitions than tempos involving slower eccentric velocity (4 seconds) or greater bottom rest (4 seconds). This combination of greater repetitions and PO resulted in a greater volume of work. Varying interrepetition rest (1 or 4 seconds) did not significantly affect PO or repetitions. The results of this study support the use of fast eccentric speed and no bottom rest during acute performance testing to maximize PO and number of repetitions during a set of bench press.
Adaptive time-varying detrended fluctuation analysis.
Berthouze, Luc; Farmer, Simon F
2012-07-30
Detrended fluctuation analysis (DFA) is a technique commonly used to assess and quantify the presence of long-range temporal correlations (LRTCs) in neurophysiological time series. Convergence of the method is asymptotic only and therefore its application assumes a constant scaling exponent. However, most neurophysiological data are likely to involve either spontaneous or experimentally induced scaling exponent changes. We present a novel extension of the DFA method that permits the characterisation of time-varying scaling exponents. The effectiveness of the methodology in recovering known changes in scaling exponents is demonstrated through its application to synthetic data. The dependence of the method on its free parameters is systematically explored. Finally, application of the methodology to neurophysiological data demonstrates that it provides experimenters with a way to identify previously un-recognised changes in the scaling exponent in the data. We suggest that this methodology will make it possible to go beyond a simple demonstration of the presence of scaling to an appreciation of how it may vary in response to either intrinsic changes or experimental perturbations. Copyright © 2012 Elsevier B.V. All rights reserved.
Climate dynamics: Why does climate vary?
Schultz, Colin
2011-08-01
In recent years, climate change has become a major focus of public and political discussion. Ongoing scientific inquiry, revolving predominantly around understanding the anthropogenic effects of rising greenhouse gas levels, coupled with how successfully findings are communicated to the public, has made climate science both contentious and exigent. In the AGU monograph Climate Dynamics: Why Does Climate Vary?, editors De-Zheng Sun and Frank Bryan reinforce the importance of investigating the complex dynamics that underlie the natural variability of the climate system. Understanding this complexity—particularly how the natural variability of climate may enhance or mask anthropogenic warming—could have important consequences for the future. In this interview, Eos talks to De-Zheng Sun.
Time varying arctic climate change amplification
Energy Technology Data Exchange (ETDEWEB)
Chylek, Petr [Los Alamos National Laboratory; Dubey, Manvendra K [Los Alamos National Laboratory; Lesins, Glen [DALLHOUSIE U; Wang, Muyin [NOAA/JISAO
2009-01-01
During the past 130 years the global mean surface air temperature has risen by about 0.75 K. Due to feedbacks -- including the snow/ice albedo feedback -- the warming in the Arctic is expected to proceed at a faster rate than the global average. Climate model simulations suggest that this Arctic amplification produces warming that is two to three times larger than the global mean. Understanding the Arctic amplification is essential for projections of future Arctic climate including sea ice extent and melting of the Greenland ice sheet. We use the temperature records from the Arctic stations to show that (a) the Arctic amplification is larger at latitudes above 700 N compared to those within 64-70oN belt, and that, surprisingly; (b) the ratio of the Arctic to global rate of temperature change is not constant but varies on the decadal timescale. This time dependence will affect future projections of climate changes in the Arctic.
Time-Varying Periodicity in Intraday Volatility
DEFF Research Database (Denmark)
Andersen, Torben Gustav; Thyrsgaard, Martin; Todorov, Viktor
with a constant time-of-day periodic component. We first construct time-of-day volatility estimates and studentize the high-frequency returns with these periodic components. If the intraday volatility periodicity is invariant over time, then the distribution of the studentized returns should be identical across......We develop a nonparametric test for deciding whether return volatility exhibits time-varying intraday periodicity using a long time-series of high-frequency data. Our null hypothesis, commonly adopted in work on volatility modeling, is that volatility follows a stationary process combined...... the trading day. Consequently, the test is based on comparing the empirical characteristic function of the studentized returns across the trading day. The limit distribution of the test depends on the error in recovering volatility from discrete return data and the empirical process error associated...
Optical vortex array in spatially varying lattice
Kapoor, Amit; Senthilkumaran, P; Joseph, Joby
2015-01-01
We present an experimental method based on a modified multiple beam interference approach to generate an optical vortex array arranged in a spatially varying lattice. This method involves two steps which are: numerical synthesis of a consistent phase mask by using two-dimensional integrated phase gradient calculations and experimental implementation of produced phase mask by utilizing a phase only spatial light modulator in an optical 4f Fourier filtering setup. This method enables an independent variation of the orientation and period of the vortex lattice. As working examples, we provide the experimental demonstration of various spatially variant optical vortex lattices. We further confirm the existence of optical vortices by formation of fork fringes. Such lattices may find applications in size dependent trapping, sorting, manipulation and photonic crystals.
Supernumerary teeth vary depending on gender
Directory of Open Access Journals (Sweden)
Erika Calvano Küchler
2011-02-01
Full Text Available The presence of supernumerary teeth (ST is a dental developmental anomaly of patterning and morphogenesis. Its variability of morphology, location and developmental timing can shed light on its etiology. In this work we report ST patterns. Orthopantomograms of 1,166 pediatric subjects were examined and the morphology, location and timing of the formation of ST were determined. The frequency of supernumerary teeth in the studied population was 2.3% (n = 27. Twenty-five subjects presented one ST. Maxilla midline was the most commonly affected region (nine cases. We noted high incidence of conical morphology in the midline region. Only teeth with tuberculate morphology presented delayed formation. ST in the midline region occurred more often in males whereas ST in the incisor region were more common in females. In conclusion, ST patterns vary depending on gender.
Varying Collimation for Dark-Field Extraction
Directory of Open Access Journals (Sweden)
Ge Wang
2009-01-01
Full Text Available Although x-ray imaging is widely used in biomedical applications, biological soft tissues have small density changes, leading to low contrast resolution for attenuation-based x-ray imaging. Over the past years, x-ray small-angle scattering was studied as a new contrast mechanism to enhance subtle structural variation within the soft tissue. In this paper, we present a detection method to extract this type of x-ray scattering data, which are also referred to as dark-field signals. The key idea is to acquire an x-ray projection multiple times with varying collimation before an x-ray detector array. The projection data acquired with a collimator of a sufficiently high collimation aspect ratio contain mainly the primary beam with little scattering, while the data acquired with an appropriately reduced collimation aspect ratio include both the primary beam and small-angle scattering signals. Then, analysis of these corresponding datasets will produce desirable dark-field signals; for example, via digitally subtraction. In the numerical experiments, the feasibility of our dark-field detection technology is demonstrated in Monte Carlo simulation. The results show that the acquired dark field signals can clearly reveal the structural information of tissues in terms of Rayleigh scattering characteristics.
Varied acceptance of clinical trial results.
Klimt, C R
1989-12-01
The subject of varied acceptance of clinical trial results is discussed in the context of review of trials with which I have been involved and my subjective evaluation of their impact on the practice of clinical medicine. My experience goes back to 1949 and a World Health Organization trial of hyperimmune gamma globulin against rabies. This was followed by a large trial of secondary prevention of poliomyelitis. I participated in the planning and initiation of the first chronic disease trial, the University Group Diabetes Program (UGDP). The latter lasted for 15 years and its ramifications continue to this day. My next trial was the Coronary Drug Project (CDP), a complex trial with more than 8,000 patients. The trials of aspirin and aspirin combined with persantine (the CDPA, AMIS, PARIS I, and PARIS II) followed. My last three trials were a trial of photocoagulation in diabetic retinopathy (DRS), a six-country trial of the antiarrhythmic drug mexiletine (IMPACT), and a study involving two diagnostic procedures for pulmonary embolism (PIOPED). When one considers, in retrospect, the plethora of trials one is struck by the uniform absence of a priori considerations of the impact on medical practice, or likely lack thereof, of possible outcomes.
Microsatellites in varied arenas of research
Directory of Open Access Journals (Sweden)
K S Remya
2010-01-01
Full Text Available Microsatellites known as simple-sequence repeats (SSRs or short-tandem repeats (STRs, represent specific sequences of DNA consisting of tandemly repeated units of one to six nucleotides. The repetitive nature of microsatellites makes them particularly prone to grow or shrink in length and these changes can have both good and bad consequences for the organisms that possess them. They are responsible for various neurological diseases and hence the same cause is now utilized for the early detection of various diseases, such as, Schizophrenia and Bipolar Disorder, Congenital generalized Hypertrichosis, Asthma, and Bronchial Hyperresponsiveness. These agents are widely used for forensic identification and relatedness testing, and are predominant genetic markers in this area of application. The application of microsatellites is an extending web and covers the varied scenarios of science, such as, conservation biology, plant genetics, and population studies. At present, researches are progressing round the globe to extend the use of these genetic repeaters to unmask the hidden genetic secrets behind the creation of the world.
Dermatophyte susceptibility varies towards antimicrobial textiles.
Hammer, Timo R; Mucha, Helmut; Hoefer, Dirk
2012-07-01
Dermatophytoses are a widespread problem worldwide. Textiles in contact with infected skin can serve as a carrier for fungus propagation. Hitherto, it is unknown, whether antifungal textiles could contribute in controlling dermatophytes e.g. by disrupting the chain of infection. Testing of antimicrobial fabrics for their antifungal activities therefore is a fundamental prerequisite to assess the putative clinical relevance of textiles for dermatophyte prevention. Fabrics finished with either didecyldimethylammonium chloride (DDAC), poly-hexamethylenbiguanide, copper and two silver chloride concentrations were tested for their antifungal activity against Trichophyton rubrum, Trichophyton mentagrophytes and Candida albicans. To prove dermatophyte susceptibility towards the textiles, swatches were subjected to DIN EN 14199 (Trichophyton sp.) or DIN EN ISO 20743 (C. albicans) respectively. In addition, samples were embedded, and semi-thin sections were analysed microscopically. While all samples showed a clear inhibition of C. albicans, activity against Trichophyton sp. varied significantly: For example, DDAC completely inhibited T. rubrum growth, whereas T. mentagrophytes growth remained unaffected even in direct contact to the fibres. The results favour to add T. mentagrophytes as a test organism in textile dermatophyte efficacy tests. Microscopic analysis of swatches allowed detailed evaluation of additional parameters like mycelium thickness, density and hyphae penetration depth into the fabric. © 2011 Blackwell Verlag GmbH.
Varying Inundation Regimes Differentially Affect Natural and ...
Climate change is altering sea-level rise rates and precipitation patterns worldwide. Coastal wetlands are vulnerable to these changes. System responses to stressors are important for resource managers and environmental stewards to understand in order to best manage them. Thin layer sand or sediment application to drowning and eroding marshes is one approach to build elevation and resilience. The above- and below-ground structure, soil carbon dioxide emissions, and pore water constituents in vegetated natural marsh sediments and sand-amended sediments were examined at varying inundation regimes between mean sea level and mean high water (0.82 m NAVD88 to 1.49 m NAVD88) in a field experiment at Laws Point, part of the Plum Island Sound Estuary (MA). Significantly lower salinities, pH, sulfides, phosphates, and ammonium were measured in the sand-amended sediments than in the natural sediments. In natural sediments there was a pattern of increasing salinity with increasing elevation while in the sand-amended sediments the trend was reversed, showing decreasing salinity with increasing elevation. Sulfide concentrations generally increased from low to high inundation with highest concentrations at the highest inundation (i.e., at the lowest elevations). High pore water phosphate concentrations were measured at low elevations in the natural sediments, but the sand-amended treatments had mostly low concentrations of phosphate and no consistent pattern with elevation. A
Functional Piezocrystal Characterisation under Varying Conditions
Directory of Open Access Journals (Sweden)
Xiaochun Liao
2015-12-01
Full Text Available Piezocrystals, especially the relaxor-based ferroelectric crystals, have been subject to intense investigation and development within the past three decades, motivated by the performance advantages offered by their ultrahigh piezoelectric coefficients and higher electromechanical coupling coefficients than piezoceramics. Structural anisotropy of piezocrystals also provides opportunities for devices to operate in novel vibration modes, such as the d36 face shear mode, with domain engineering and special crystal cuts. These piezocrystal characteristics contribute to their potential usage in a wide range of low- and high-power ultrasound applications. In such applications, conventional piezoelectric materials are presently subject to varying mechanical stress/pressure, temperature and electric field conditions. However, as observed previously, piezocrystal properties are significantly affected by a single such condition or a combination of conditions. Laboratory characterisation of the piezocrystal properties under these conditions is therefore essential to fully understand these materials and to allow electroacoustic transducer design in realistic scenarios. This will help to establish the extent to which these high performance piezocrystals can replace conventional piezoceramics in demanding applications. However, such characterisation requires specific experimental arrangements, examples of which are reported here, along with relevant results. The measurements include high frequency-resolution impedance spectroscopy with the piezocrystal material under mechanical stress 0–60 MPa, temperature 20–200 °C, high electric AC drive and DC bias. A laser Doppler vibrometer and infrared thermal camera are also integrated into the measurement system for vibration mode shape scanning and thermal conditioning with high AC drive. Three generations of piezocrystal have been tested: (I binary, PMN-PT; (II ternary, PIN-PMN-PT; and (III doped ternary, Mn
Toxoplasma gondii seroprevalence varies by cat breed.
Must, Kärt; Hytönen, Marjo K; Orro, Toomas; Lohi, Hannes; Jokelainen, Pikka
2017-01-01
Toxoplasma gondii is a widespread zoonotic parasite that is relevant for veterinary and public health. The domestic cat, the definitive host species with the largest worldwide population, has become evolutionarily and epidemiologically the most important host of T. gondii. The outcome of T. gondii infection is influenced by congenital and acquired host characteristics. We detected differences in T. gondii seroprevalence by cat breed in our previous studies. The aims of this study were to estimate T. gondii seroprevalence in selected domestic cat breeds, and to evaluate whether being of a certain breed is associated with T. gondii seropositivity, when the age and lifestyle of the cat are taken into account. The studied breeds were the Birman, British Shorthair, Burmese, Korat, Norwegian Forest Cat, Ocicat, Persian, and Siamese. Plasma samples were analyzed for the presence of immunoglobulin G antibodies against T. gondii with a commercial direct agglutination test at dilution 1:40. The samples were accompanied by owner-completed questionnaires that provided background data on the cats. Overall, 41.12% of the 1121 cats tested seropositive, and the seroprevalence increased with age. The Burmese had the lowest seroprevalence (18.82%) and the Persian had the highest (60.00%). According to the final multivariable logistic regression model, the odds to test seropositive were four to seven times higher in Birmans, Ocicats, Norwegian Forest Cats, and Persians when compared with the Burmese, while older age and receiving raw meat were also risk factors for T. gondii seropositivity. This study showed that T. gondii seroprevalence varies by cat breed and identified being of certain breeds, older age, and receiving raw meat as risk factors for seropositivity.
Functional Piezocrystal Characterisation under Varying Conditions.
Liao, Xiaochun; Qiu, Zhen; Jiang, Tingyi; Sadiq, Muhammad R; Huang, Zhihong; Demore, Christine E M; Cochran, Sandy
2015-12-02
Piezocrystals, especially the relaxor-based ferroelectric crystals, have been subject to intense investigation and development within the past three decades, motivated by the performance advantages offered by their ultrahigh piezoelectric coefficients and higher electromechanical coupling coefficients than piezoceramics. Structural anisotropy of piezocrystals also provides opportunities for devices to operate in novel vibration modes, such as the d36 face shear mode, with domain engineering and special crystal cuts. These piezocrystal characteristics contribute to their potential usage in a wide range of low- and high-power ultrasound applications. In such applications, conventional piezoelectric materials are presently subject to varying mechanical stress/pressure, temperature and electric field conditions. However, as observed previously, piezocrystal properties are significantly affected by a single such condition or a combination of conditions. Laboratory characterisation of the piezocrystal properties under these conditions is therefore essential to fully understand these materials and to allow electroacoustic transducer design in realistic scenarios. This will help to establish the extent to which these high performance piezocrystals can replace conventional piezoceramics in demanding applications. However, such characterisation requires specific experimental arrangements, examples of which are reported here, along with relevant results. The measurements include high frequency-resolution impedance spectroscopy with the piezocrystal material under mechanical stress 0-60 MPa, temperature 20-200 °C, high electric AC drive and DC bias. A laser Doppler vibrometer and infrared thermal camera are also integrated into the measurement system for vibration mode shape scanning and thermal conditioning with high AC drive. Three generations of piezocrystal have been tested: (I) binary, PMN-PT; (II) ternary, PIN-PMN-PT; and (III) doped ternary, Mn:PIN-PMN-PT. Utilising
Time Frequency Features of Rotor Systems with Slowly Varying Mass
Directory of Open Access Journals (Sweden)
Tao Yu
2011-01-01
Full Text Available With the analytic method and numerical method respectively, the asymptotic solutions and finite element model of rotor system with single slowly varying mass is obtained to investigate the time frequency features of such rotor system; furthermore, with given model of slowly varying mass, the rotor system with dual slowly varying mass is studied. For the first order approximate solution is used, there exists difference between the results with analytic method and numerical method. On the base of common characteristics of rotor system with dual slowly varying mass, the general rules and formula describing the frequency distribution of rotor system with multiple slowly varying mass are proposed.
Estimating varying coefficients for partial differential equation models.
Zhang, Xinyu; Cao, Jiguo; Carroll, Raymond J
2017-09-01
Partial differential equations (PDEs) are used to model complex dynamical systems in multiple dimensions, and their parameters often have important scientific interpretations. In some applications, PDE parameters are not constant but can change depending on the values of covariates, a feature that we call varying coefficients. We propose a parameter cascading method to estimate varying coefficients in PDE models from noisy data. Our estimates of the varying coefficients are shown to be consistent and asymptotically normally distributed. The performance of our method is evaluated by a simulation study and by an empirical study estimating three varying coefficients in a PDE model arising from LIDAR data. © 2017, The International Biometric Society.
Methods for time-varying exposure related problems in pharmacoepidemiology
DEFF Research Database (Denmark)
Pazzagli, Laura; Linder, Marie; Zhang, Mingliang
2017-01-01
PURPOSE: Lack of control for time-varying exposures can lead to substantial bias in estimates of treatment effects. The aim of this study is to provide an overview and guidance on some of the available methodologies used to address problems related to time-varying exposure and confounding...... pharmacoepidemiological problems, construction of treatment episodes, time-varying confounders, cumulative exposure and latency, and treatment switching. RESULTS: A correct treatment episodes construction is fundamental to avoid bias in treatment effect estimates. Several methods exist to address time-varying covariates...
Audio Effects Based on Biorthogonal Time-Varying Frequency Warping
Directory of Open Access Journals (Sweden)
Sergio Cavaliere
2001-03-01
Full Text Available We illustrate the mathematical background and musical use of a class of audio effects based on frequency warping. These effects alter the frequency content of a signal via spectral mapping. They can be implemented in dispersive tapped delay lines based on a chain of all-pass filters. In a homogeneous line with first-order all-pass sections, the signal formed by the output samples at a given time is related to the input via the Laguerre transform. However, most musical signals require a time-varying frequency modification in order to be properly processed. Vibrato in musical instruments or voice intonation in the case of vocal sounds may be modeled as small and slow pitch variations. Simulation of these effects requires techniques for time-varying pitch and/or brightness modification that are very useful for sound processing. The basis for time-varying frequency warping is a time-varying version of the Laguerre transformation. The corresponding implementation structure is obtained as a dispersive tapped delay line, where each of the frequency dependent delay element has its own phase response. Thus, time-varying warping results in a space-varying, inhomogeneous, propagation structure. We show that time-varying frequency warping is associated to an expansion over biorthogonal sets generalizing the discrete Laguerre basis. Slow time-varying characteristics lead to slowly varying parameter sequences. The corresponding sound transformation does not suffer from discontinuities typical of delay lines based on unit delays.
Time-varying interaction leads to amplitude death in coupled ...
Indian Academy of Sciences (India)
A new form of time-varying interaction in coupled oscillators is introduced. In this interaction, each individual oscillator has always time-independent self-feedback while its interaction with other oscillators are modulated with time-varying function. This interaction gives rise to a phenomenon called amplitude death even in ...
Time-frequency representation based on time-varying ...
Indian Academy of Sciences (India)
Abstract. A parametric time-frequency representation is presented based on time- varying autoregressive model (TVAR), followed by applications to non-stationary vibration signal processing. The identification of time-varying model coefficients and the determination of model order, are addressed by means of neural ...
Linear Parameter Varying Control of Doubly Fed Induction Machines
Tien, H. Nguyen; Scherer, Carsten W.; Scherpen, Jacquelien M.A.; Müller, Volkmar
This paper is concerned with the design of a self-scheduled current controller for doubly fed induction machines. The design is based on the framework of linear parameter-varying systems where the mechanical angular speed is considered to be a measurable time-varying parameter. The objective is to
Surface sealing and hydraulic conductances under varying-intensity rains
Giménez, D.; Dirksen, C.; Miedema, R.; Eppink, L.A.A.J.; Schoonderbeek, D.
1992-01-01
In the past, investigations on surface seals developing under simulated rains usually were performed with uniform rainfall intensities. Recent studies, however, showed that varying-intensity rains affect erosion and volumes of runoff. We conducted a study on surface sealing under varying-intensity
Expected optimal feedback with Time-Varying Parameters
Tucci, M.P.; Kendrick, D.A.; Amman, H.M.|info:eu-repo/dai/nl/070970777
2011-01-01
In this paper we derive the closed loop form of the Expected Optimal Feedback rule, sometimes called passive learning stochastic control, with time varying parameters. As such this paper extends the work of Kendrick (1981,2002, Chapter 6) where parameters are assumed to vary randomly around a known
How Do Parenting Concepts Vary within and between the Families?
Roskam, Isabelle; Meunier, Jean Christophe
2009-01-01
How do parenting concepts vary within and between the families? The present study regards parenting as a complex family process by considering three concepts of parenting: styles, differential treatment and coparenting consistency. A main question was addressed: whether and how these parenting concepts vary within the families towards siblings or…
Time varying voltage combustion control and diagnostics sensor
Chorpening, Benjamin T [Morgantown, WV; Thornton, Jimmy D [Morgantown, WV; Huckaby, E David [Morgantown, WV; Fincham, William [Fairmont, WV
2011-04-19
A time-varying voltage is applied to an electrode, or a pair of electrodes, of a sensor installed in a fuel nozzle disposed adjacent the combustion zone of a continuous combustion system, such as of the gas turbine engine type. The time-varying voltage induces a time-varying current in the flame which is measured and used to determine flame capacitance using AC electrical circuit analysis. Flame capacitance is used to accurately determine the position of the flame from the sensor and the fuel/air ratio. The fuel and/or air flow rate (s) is/are then adjusted to provide reduced flame instability problems such as flashback, combustion dynamics and lean blowout, as well as reduced emissions. The time-varying voltage may be an alternating voltage and the time-varying current may be an alternating current.
Free Electron Lasers with Slowly Varying Beam and Undulator Parameters
Huang, Zhirong
2005-01-01
The performance of a free electron lasers (FEL) is affected when the electron beam energy varies alone the undulator as would be caused by vacuum pipe wakefields and/or when the undulator strength parameter is tapered in the small signal regime until FEL saturation. In this paper, we present a self-consistent theory of FELs with slowly-varying beam and undulator parameters. A general method is developed to apply the WKB approximation to the beam-radiation system by employing the adjoint eigenvector that is orthogonal to the eigenfunctions of the coupled Maxwell-Vlasov equations. This method may be useful for other slowly varying processes in beam dynamics.
Robust Stabilization of Nonlinear Systems with Uncertain Varying Control Coefficient
Directory of Open Access Journals (Sweden)
Zaiyue Yang
2014-01-01
Full Text Available This paper investigates the stabilization problem for a class of nonlinear systems, whose control coefficient is uncertain and varies continuously in value and sign. The study emphasizes the development of a robust control that consists of a modified Nussbaum function to tackle the uncertain varying control coefficient. By such a method, the finite-time escape phenomenon has been prevented when the control coefficient is crossing zero and varying its sign. The proposed control guarantees the asymptotic stabilization of the system and boundedness of all closed-loop signals. The control performance is illustrated by a numerical simulation.
Influence of feeding varying crude protein and digestible energy ...
African Journals Online (AJOL)
Influence of feeding varying crude protein and digestible energy levels on the development of individual muscles, rate of lean and fat deposition in pigs reared from 9 to 60kg liveweight in a humid tropical environment.
Estimation of Time Varying Autoregressive Symmetric Alpha Stable
National Aeronautics and Space Administration — In this work, we present a novel method for modeling time-varying autoregressive impulsive signals driven by symmetric alpha stable distributions. The proposed...
Uus Eesti film pandi eile Karlovy Varys projektorisse / Kristiina Davidjants
Davidjants, Kristiina, 1974-
2008-01-01
8. juulil esilinastus Karlovy Vary filmifestivalil Rene Vilbre noortefilm "Mina olin siin", mille aluseks on Sass Henno romaan "Mina olin siin. Esimene arest". Film võistleb võistlusprogrammis "East of the West"
Modeling non-Gaussian time-varying vector autoregressive process
National Aeronautics and Space Administration — We present a novel and general methodology for modeling time-varying vector autoregressive processes which are widely used in many areas such as modeling of chemical...
Toluene metabolism during exposure to varying concentrations combined with exercise
DEFF Research Database (Denmark)
Bælum, Jesper; Døssing, M; Hansen, S H
1987-01-01
The urinary excretion of hippuric acid (HA) and ortho-cresol (O-cr) in man was measured in two studies of 7-h exposure to toluene in a climate chamber, either constant concentration of 100 ppm or varying concentrations containing peaks of 300 ppm but with a time-weighted average of 100 ppm....... In Study A, four males were exposed to clean air and to constant and varying concentrations of toluene in combination with rest and with 100 W exercise in 140 min. Exercise increased end exposure excretion rate of HA and O-cr by 47 and 114%, respectively. After exposure, all excess HA was excreted within 4...... h, while O-cr was eliminated with a half life of about 3 h. Alveolar air concentration of toluene varied between 21 and 31 ppm during constant exposure and between 13 and 57 ppm during varying exposure, but no difference in mean alveolar toluene concentration or in metabolite excretion was seen...
A Semiparametric Recurrent Events Model with Time-varying Coefficients
Yu, Zhangsheng; Liu, Lei; Bravata, Dawn M.; Williams, Linda S.; Tepper, Robert S.
2013-01-01
SUMMARY We consider a recurrent events model with time-varying coefficients motivated by two clinical applications. A random effects (Gaussian frailty) model is used to describe the intensity of recurrent events. The model can accommodate both time-varying and time-constant coefficients. The penalized spline method is used to estimate the time-varying coefficients. Laplace approximation is used to evaluate the penalized likelihood without a closed form. The smoothing parameters are estimated in a similar way to variance components. We conduct simulations to evaluate the performance of the estimates for both time-varying and time-independent coefficients. We apply this method to analyze two data sets: a stroke study and a child wheeze study. PMID:22903343
Quality of Eggs Under Varying Storage Periods, Conditions and ...
African Journals Online (AJOL)
Quality of Eggs Under Varying Storage Periods, Conditions and Seasons in ... and egg weight on external and internal characteristics of chicken eggs. ... Storage time did not affect (p>0.05) shell weight, shape index, egg length and egg width.
Analysis of time-varying psoriasis lesion image patterns
DEFF Research Database (Denmark)
Maletti, Gabriela Mariel; Ersbøll, Bjarne Kjær; Nielsen, Allan Aasbjerg
2004-01-01
The multivariate alteration detection transform is applied to pairs of within and between time varying registered psoriasis image patterns. Color band contribution to the variates explaining maximal change is analyzed....
Gut microbiomes of Indian children of varying nutritional status
National Research Council Canada - National Science Library
Ghosh, Tarini Shankar; Gupta, Sourav Sen; Bhattacharya, Tanudeep; Yadav, Deepak; Barik, Anamitra; Chowdhury, Abhijit; Das, Bhabatosh; Mande, Sharmila S; Nair, G Balakrish
2014-01-01
.... Consequently, dysbiosis of the gut microbiota has been implicated in malnutrition. Metagenomics approach was adopted to investigate the gut microbiome sampled from 20 rural Indian children with varying nutritional status...
Design of 2D Time-Varying Vector Fields
Chen, Guoning
2012-10-01
Design of time-varying vector fields, i.e., vector fields that can change over time, has a wide variety of important applications in computer graphics. Existing vector field design techniques do not address time-varying vector fields. In this paper, we present a framework for the design of time-varying vector fields, both for planar domains as well as manifold surfaces. Our system supports the creation and modification of various time-varying vector fields with desired spatial and temporal characteristics through several design metaphors, including streamlines, pathlines, singularity paths, and bifurcations. These design metaphors are integrated into an element-based design to generate the time-varying vector fields via a sequence of basis field summations or spatial constrained optimizations at the sampled times. The key-frame design and field deformation are also introduced to support other user design scenarios. Accordingly, a spatial-temporal constrained optimization and the time-varying transformation are employed to generate the desired fields for these two design scenarios, respectively. We apply the time-varying vector fields generated using our design system to a number of important computer graphics applications that require controllable dynamic effects, such as evolving surface appearance, dynamic scene design, steerable crowd movement, and painterly animation. Many of these are difficult or impossible to achieve via prior simulation-based methods. In these applications, the time-varying vector fields have been applied as either orientation fields or advection fields to control the instantaneous appearance or evolving trajectories of the dynamic effects. © 1995-2012 IEEE.
Electricity futures prices: time varying sensitivity to fundamentals
Fleten, Stein-Erik; Huisman, Ronald; Kilic, Mehtap; Pennings, Enrico; Westgaard, Sjur
2014-01-01
This paper provides insight into the time-varying relation between electricity futures prices and fundamentals in the form of contract prices for fossil fuels. As supply curves are not constant and different producers have different marginal costs of production, we argue that the relation between the prices of electricity futures and those of underlying fundamentals such as natural gas, coal and emission rights varies over time. We test this view by applying a model that linearly relates elec...
Bounds and asymptotics for orthogonal polynomials for varying weights
Levin, Eli
2018-01-01
This book establishes bounds and asymptotics under almost minimal conditions on the varying weights, and applies them to universality limits and entropy integrals. Orthogonal polynomials associated with varying weights play a key role in analyzing random matrices and other topics. This book will be of use to a wide community of mathematicians, physicists, and statisticians dealing with techniques of potential theory, orthogonal polynomials, approximation theory, as well as random matrices. .
Vibration Analysis of Composite Beams with Sinusoidal Periodically Varying Interfaces
Li, Botong; Liu, Chein-Shan; Zhu, Liangliang
2017-12-01
As an increasing variety of composite materials with complex interfaces are emerging, we develop a theory to investigate composite beams and shed some light on new physical insights into composite beams with sinusoidal periodically varying interfaces. For the natural vibration of composite beams with continuous or periodically varying interfaces, the governing equation has been derived according to the generalised Hamiltonian principle. For composite beams having different boundary conditions, we transform the governing equations into integral equations and solve them by using the sinusoidal functions as test functions as well as the basis of the vibration modes. Due to the orthogonality of the sinusoidal functions, expansion coefficients in closed form can be found. Therefore, the proposed iterative schemes, with the help of the Rayleigh quotient and boundary functions, can quickly find the eigenvalues and free vibration modes. The obtained natural frequencies agree well with those obtained using the finite element method. In addition, the proposed method can be extended easily to laminated composite beams in more general cases or complex components and geometries in vibration engineering. The effects of different material properties of the upper and lower components and varying interface geometry function on the frequency of the composite beams are examined. According to our investigation, the natural frequency of a laminated beam with a continuous or periodically varying interface can be changed by altering the density or elastic modulus. We also show the responses of the frequencies of the components to the varying periodic interface.
Energy Technology Data Exchange (ETDEWEB)
Mascarenhas, Ajith Arthur [Univ. of North Carolina, Chapel Hill, NC (United States)
2006-01-01
I present time-varying Reeb graphs as a topological framework to support the analysis of continuous time-varying data. Such data is captured in many studies, including computational fluid dynamics, oceanography, medical imaging, and climate modeling, by measuring physical processes over time, or by modeling and simulating them on a computer. Analysis tools are applied to these data sets by scientists and engineers who seek to understand the underlying physical processes. A popular tool for analyzing scientific datasets is level sets, which are the points in space with a fixed data value s. Displaying level sets allows the user to study their geometry, their topological features such as connected components, handles, and voids, and to study the evolution of these features for varying s. For static data, the Reeb graph encodes the evolution of topological features and compactly represents topological information of all level sets. The Reeb graph essentially contracts each level set component to a point. It can be computed efficiently, and it has several uses: as a succinct summary of the data, as an interface to select meaningful level sets, as a data structure to accelerate level set extraction, and as a guide to remove noise. I extend these uses of Reeb graphs to time-varying data. I characterize the changes to Reeb graphs over time, and develop an algorithm that can maintain a Reeb graph data structure by tracking these changes over time. I store this sequence of Reeb graphs compactly, and call it a time-varying Reeb graph. I augment the time-varying Reeb graph with information that records the topology of level sets of all level values at all times, that maintains the correspondence of level set components over time, and that accelerates the extraction of level sets for a chosen level value and time. Scientific data sampled in space-time must be extended everywhere in this domain using an interpolant. A poor choice of interpolant can create degeneracies that are
Robust linear parameter varying induction motor control with polytopic models
Directory of Open Access Journals (Sweden)
Dalila Khamari
2013-01-01
Full Text Available This paper deals with a robust controller for an induction motor which is represented as a linear parameter varying systems. To do so linear matrix inequality (LMI based approach and robust Lyapunov feedback controller are associated. This new approach is related to the fact that the synthesis of a linear parameter varying (LPV feedback controller for the inner loop take into account rotor resistance and mechanical speed as varying parameter. An LPV flux observer is also synthesized to estimate rotor flux providing reference to cited above regulator. The induction motor is described as a polytopic model because of speed and rotor resistance affine dependence their values can be estimated on line during systems operations. The simulation results are presented to confirm the effectiveness of the proposed approach where robustness stability and high performances have been achieved over the entire operating range of the induction motor.
Precoder and decoder prediction in time-varying MIMO channel
DEFF Research Database (Denmark)
Nguyen, Tuan Hung; Leus, Geert; Khaled, Nadia
2005-01-01
In mobile communications, time varying channels make the available channel information out of date. Timely updating the channel state is an obvious solution to improve the system performance in a time varying channel. However, a better knowledge of the channel comes at the cost of a decrease...... in the system throughput. Thus, predicting the future channel conditions can improve not only the performance but also the throughput of many types of wireless systems. This is especially true for a wireless system where multiple antennas are applied at both link ends. In this report we propose and evaluate...
Partially linear varying coefficient models stratified by a functional covariate
Maity, Arnab
2012-10-01
We consider the problem of estimation in semiparametric varying coefficient models where the covariate modifying the varying coefficients is functional and is modeled nonparametrically. We develop a kernel-based estimator of the nonparametric component and a profiling estimator of the parametric component of the model and derive their asymptotic properties. Specifically, we show the consistency of the nonparametric functional estimates and derive the asymptotic expansion of the estimates of the parametric component. We illustrate the performance of our methodology using a simulation study and a real data application.
Computation of gradually varied flow in compound open channel ...
Indian Academy of Sciences (India)
In this method, the energy and continuity equations are solved for steady, gradually varied flow by the Newton–Raphson method and the proposed methodology is applied to tree-type and looped-channel networks. An algorithm is presented to determine multiple critical depths in a compound channel. Modifications in ...
Time Varying Market Integration and Expected Rteurns in Emerging Markets
de Jong, F.C.J.M.; de Roon, F.A.
2001-01-01
We use a simple model in which the expected returns in emerging markets depend on their systematic risk as measured by their beta relative to the world portfolio as well as on the level of integration in that market.The level of integration is a time-varying variable that depends on the market value
Overcoming Spurious Regression Using time-Varying Fourier ...
African Journals Online (AJOL)
Non-stationary time series data have been traditionally analyzed in the frequency domain by assuming constant amplitudes regardless of the timelag. A new approach called time-varying amplitude method (TVAM) is presented here. Oscillations are analyzed for changes in the magnitude of Fourier Coefficients which are ...
Multivariate Option Pricing with Time Varying Volatility and Correlations
DEFF Research Database (Denmark)
Rombouts, Jeroen V.K.; Stentoft, Lars Peter
In recent years multivariate models for asset returns have received much attention, in particular this is the case for models with time varying volatility. In this paper we consider models of this class and examine their potential when it comes to option pricing. Specifically, we derive the risk ...
Microwave oven-induced decalcification at varying temperatures: A ...
African Journals Online (AJOL)
This study was designed to evaluate the effect of decalcifying fluid types on bone tissue architecture and its staining properties following decalcification at varying temperatures. A decalcification methodology using Golding and Stewards (GS) fluid, and Jenkings fluid (JK), and a modern household microwave oven to ...
A five-dimensional model of varying fine structure constant
Indian Academy of Sciences (India)
A five-dimensional model of varying fine structure constant. J P MBELEK. Service d'Astrophysique, C.E. Saclay, F-91191 Gif-sur-Yvette Cedex, France. Abstract. The cosmological variation of the fine structure constant « is explored from an effective theory, under the form of an improved version of the 5D Kaluza-Klein theory.
A five-dimensional model of varying fine structure constant
Indian Academy of Sciences (India)
dimensional model of varying fine structure constant. J P Mbelek. Cosmology Volume 62 Issue 3 March 2004 pp 741-743. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/pram/062/03/0741-0743 ...
Incremental Closed-loop Identification of Linear Parameter Varying Systems
DEFF Research Database (Denmark)
Bendtsen, Jan Dimon; Trangbæk, Klaus
2011-01-01
This paper deals with system identification for control of linear parameter varying systems. In practical applications, it is often important to be able to identify small plant changes in an incremental manner without shutting down the system and/or disconnecting the controller; unfortunately, cl...
Effects of varying protein levels on broiler performance when dietary ...
African Journals Online (AJOL)
Effects of varying protein levels on broiler performance when dietary energy levels remain constant. S A Osei, K Effah-Baah. Abstract. (Ghana Journal of Agricultural Science, 1987-90, 20-23: 21-24). Full Text: EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT · AJOL African Journals ...
Adolescent Sexual Behaviors at Varying Levels of Substance Use Frequency
Floyd, Leah J.; Latimer, William
2010-01-01
Combining substance use and sex compounds the risk of contracting sexually transmitted diseases, including HIV. However, the association between substance use and sexual behaviors may vary by substance and sexual behavior. The current study sought to examine the relationship between alcohol and marijuana use frequency and specific sexual…
Response of Japanese Breeder Quails to Varying Dietary Protein ...
African Journals Online (AJOL)
A three months feeding trial was conducted to assess the effects of feeding varying levels of dietary protein on productive performance, egg quality characteristics and hatchability using 930 six weeks breeders quails. The birds were randomly divided into five dietary treatment groups of 186 birds, and were further replicated ...
Performance and cost implication of finisher turkeys fed varying ...
African Journals Online (AJOL)
A 28-day experiment was conducted to determine the effect of feeding varying levels of rice milling waste as a substitute on maize on the performance, nutrient utilization and the economics implication on finisher turkeys. Five turkey finisher diets were formulated by substituting maize with rice milling waste at 0%, 25%, 50%, ...
Effect of Varying Concentration of Auxins and Stem Length on ...
African Journals Online (AJOL)
A study was carried out to evaluate the effect of varying hormonal treatments and length of cuttings of clonal materials on the sprouting and rooting abilities of Jatropha curcas L. Two stem cutting lengths: 30cm and 60cm were pre-treated with two types of auxins: Naphthalene Acetic Acid (NAA) and Indole-3-Butyric Acid ...
Non-stationary vibrations of mechanical systems with slowly varying ...
African Journals Online (AJOL)
The paper presents an approximate analytical solution for investigation of vibration responses in linear Single-Degree-of-Freedom-Systems (SDOF) with slowly varying natural frequency subjected to a transient excitalion force with constant amplitude. The solution employs the WBKJ-approximation method, the method of ...
Time-frequency representation based on time-varying ...
Indian Academy of Sciences (India)
A parametric time-frequency representation is presented based on timevarying autoregressive model (TVAR), followed by applications to non-stationary vibration signal processing. The identiﬁcation of time-varying model coefﬁcients and the determination of model order, are addressed by means of neural networks and ...
Explicit Analytical Solution of a Pendulum with Periodically Varying Length
Yang, Tianzhi; Fang, Bo; Li, Song; Huang, Wenhu
2010-01-01
A pendulum with periodically varying length is an interesting physical system. It has been studied by some researchers using traditional perturbation methods (for example, the averaging method). But due to the limitation of the conventional perturbation methods, the solutions are not valid for long-term prediction of the pendulum. In this paper,…
SANS investigation on evolution of pore morphology for varying ...
Indian Academy of Sciences (India)
morphology for varying sintering time in porous ceria. A K PATRA1, S RAMANATHAN2, D SEN1 and S MAZUMDER1. 1Solid State Physics Division; 2Materials Science Division, Bhabha Atomic Research. Centre, Mumbai 400 085, India. E-mail: apatra@magnum.barc.ernet.in. Abstract. Precipitates of ceria were synthesized ...
Time-varying correlation and common structures in volatility
Liu, Yang
2016-01-01
This thesis studies time series properties of the covariance structure of multivariate asset returns. First, the time-varying feature of correlation is investigated at the intraday level with a new correlation model incorporating the intraday correlation dynamics. Second, the thesis develops a
Crop-Livestock Farming Systems Varying with Different Altitudes in ...
African Journals Online (AJOL)
In Sub-Saharan Africa, rangeland is increasingly converted to cropland, creating diverse crop-livestock practices in different environments. As these practices lead to highly adapted livestock production systems using resources that vary locally and seasonally, not much is known about their similarities and differences.
Time-varying Combinations of Predictive Densities using Nonlinear Filtering
M. Billio (Monica); R. Casarin (Roberto); F. Ravazzolo (Francesco); H.K. van Dijk (Herman)
2012-01-01
textabstractWe propose a Bayesian combination approach for multivariate predictive densities which relies upon a distributional state space representation of the combination weights. Several specifications of multivariate time-varying weights are introduced with a particular focus on weight dynamics
The Multi-Vari Chart -- A Systematic Approach
de Mast, J.; Roes, K.C.B.; Does, R.J.M.M.
1999-01-01
Prior to setting up a designed experiment or setting up a monitoring system for a process most experimenters perform an exploratory study to investigate thestructure of the process' variation. Tools that are frequently used for such a study are predominantly graphical in nature.The multi-vari chart
Sheep response to sugar cane tops supplemented with varying ...
African Journals Online (AJOL)
This study was conducted to examine the response of West African Dwarf (WAD) sheep to sugarcane (Sacccharum officinarum) tops supplemented with varying levels of Leucaena leucocephala foliage. Twenty WAD sheep averaging 10.14kg were randomly divided into four groups of 5 replicates, and each group was fed ...
Estimation of time-varying channels - A block approach
Leus, G.; Tang, Z.; Banelli, P.
2011-01-01
Channel state information (CSI) is indispensable for coherent detection in a wireless communication system. The pilot-aided method is one of the most intensively studied approaches for channel estimation. This method is especially attractive for time-varying channels because of their short coherence
Artificial Bee Colony Algorithm with Time-Varying Strategy
Directory of Open Access Journals (Sweden)
Quande Qin
2015-01-01
Full Text Available Artificial bee colony (ABC is one of the newest additions to the class of swarm intelligence. ABC algorithm has been shown to be competitive with some other population-based algorithms. However, there is still an insufficiency that ABC is good at exploration but poor at exploitation. To make a proper balance between these two conflictive factors, this paper proposed a novel ABC variant with a time-varying strategy where the ratio between the number of employed bees and the number of onlooker bees varies with time. The linear and nonlinear time-varying strategies can be incorporated into the basic ABC algorithm, yielding ABC-LTVS and ABC-NTVS algorithms, respectively. The effects of the added parameters in the two new ABC algorithms are also studied through solving some representative benchmark functions. The proposed ABC algorithm is a simple and easy modification to the structure of the basic ABC algorithm. Moreover, the proposed approach is general and can be incorporated in other ABC variants. A set of 21 benchmark functions in 30 and 50 dimensions are utilized in the experimental studies. The experimental results show the effectiveness of the proposed time-varying strategy.
Response of rabbits to varying levels of cassava and Leucaena ...
African Journals Online (AJOL)
An experiment was carried out to determine the performance, haematology, carcass characteristics and sensory evaluation of meat from rabbits (n = 30) fed varying levels of cassava and Leucaena leaf meal diets. Rabbits were randomly allocated to five dietary treatments of 0, 10, 20, 30 and 40% CLM replaced with LLM for ...
Water use efficiency of six rangeland grasses under varied soil ...
African Journals Online (AJOL)
The changes in soil moisture content were measured by Gypsum Block which aided in determining the irrigation schedules. The grasses demonstrated varied levels of WUE which was evaluated by amount of biomass productivity in relation to evapotranspired water during the growing period. The three soil moisture content ...
Performance and External Egg Quality of Layers under Varying ...
African Journals Online (AJOL)
Performance and External Egg Quality of Layers under Varying Stocking ... Study determined the performance and external egg quality of layers in locally fabricated metal-type battery cage at different stocking density. ... Birds stocked at 2/cell gained 15g/birds in weight while birds stocked 3 and 4 ... OTHER RESOURCES.
Electricity Futures Prices : Time Varying Sensitivity to Fundamentals
S-E. Fleten (Stein-Erik); R. Huisman (Ronald); M. Kilic (Mehtap); H.P.G. Pennings (Enrico); S. Westgaard (Sjur)
2014-01-01
textabstractThis paper provides insight in the time-varying relation between electricity futures prices and fundamentals in the form of prices of contracts for fossil fuels. As supply curves are not constant and different producers have different marginal costs of production, we argue that the
Mining Graphs for Understanding Time-Varying Volumetric Data.
Gu, Yi; Wang, Chaoli; Peterka, Tom; Jacob, Robert; Kim, Seung Hyun
2016-01-01
A notable recent trend in time-varying volumetric data analysis and visualization is to extract data relationships and represent them in a low-dimensional abstract graph view for visual understanding and making connections to the underlying data. Nevertheless, the ever-growing size and complexity of data demands novel techniques that go beyond standard brushing and linking to allow significant reduction of cognition overhead and interaction cost. In this paper, we present a mining approach that automatically extracts meaningful features from a graph-based representation for exploring time-varying volumetric data. This is achieved through the utilization of a series of graph analysis techniques including graph simplification, community detection, and visual recommendation. We investigate the most important transition relationships for time-varying data and evaluate our solution with several time-varying data sets of different sizes and characteristics. For gaining insights from the data, we show that our solution is more efficient and effective than simply asking users to extract relationships via standard interaction techniques, especially when the data set is large and the relationships are complex. We also collect expert feedback to confirm the usefulness of our approach.
Modelling Acoustic Wave Propagation in Axisymmetric Varying-Radius Waveguides
DEFF Research Database (Denmark)
Bæk, David; Willatzen, Morten
2008-01-01
A computationally fast and accurate model (a set of coupled ordinary differential equations) for fluid sound-wave propagation in infinite axisymmetric waveguides of varying radius is proposed. The model accounts for fluid heat conduction and fluid irrotational viscosity. The model problem is solved...
Effects of varying dietary zinc levels on energy and nitrogen ...
African Journals Online (AJOL)
Effects of varying dietary zinc levels on energy and nitrogen utilization in West African dwarf kids. ... Animals were transferred to individual metabolic cages for separate collection of feaces and urine 14 and 15 weeks later. Parameters determined were dry matter intake (DMI), energy utilization and nitrogen utilization.
The Mathematics of Ghanaian circular musical drumheads: varying ...
African Journals Online (AJOL)
In this work the drumhead is modeled, by making the tension in it to vary as a periodic function of time, using the two dimensional wave equation. The separated Ordinary Differential Equations (ODEs) are solved and the Fourier- Bessel coefficients are determined using the initial and boundary conditions imposed on the ...
Effects Of Varying Levels Of Dietary Protein On The Carcass ...
African Journals Online (AJOL)
Sixteen New Zealand White rabbits aged 9-10 weeks and weighing 0.72-0.99 kg were used to examine the effects of varying levels of dietary protein on carcass characteristics of rabbits. They were divided into four groups and allotted to four dietary treatments A, B, C and D formulated with 10, 13, 16 and 20 % crude protein ...
with varying Levels of Moringa oleifera Leaves Powder
African Journals Online (AJOL)
The study was conducted to evaluate the organoleptic properties of soy meatball at varying levels of Moringa oleifera leaves powder inclusion. The result of the sensory evaluation of the products showed that they were generally accepted above average (3.5). However, soy meatball sample without Moringa oleifera leaves ...
Peer influence on school learning among students of varying socio ...
African Journals Online (AJOL)
This study examined peer Influence on School Learning among students of varying socio-economic backgrounds. One hundred and twenty students (60 males and 60 females) with a mean age 15.1 years were randomly selected from four co-educational Secondary Schools in Ikenne Local Government area of Ogun State.
Time varying market efficiency of the GCC stock markets
Charfeddine, Lanouar; Khediri, Karim Ben
2016-02-01
This paper investigates the time-varying levels of weak-form market efficiency for the GCC stock markets over the period spanning from May 2005 to September 2013. We use two empirical approaches: (1) the generalized autoregressive conditional heteroscedasticity in mean (GARCH-M) model with state space time varying parameter (Kalman filter), and (2) a rolling technique sample test of the fractional long memory parameter d. As long memory estimation methods, we use the detrended fluctuation analysis (DFA) technique, the modified R/S statistic, the exact local whittle (ELW) and the feasible Exact Local Whittle (FELW) methods. Moreover, we use the Bai and Perron (1998, 2003) multiple structural breaks technique to test and date the time varying behavior of stock market efficiency. Empirical results show that GCC markets have different degrees of time-varying efficiency, and also have experiencing periods of efficiency improvement. Results also show evidence of structural breaks in all GCC markets. Moreover, we observe that the recent financial shocks such as Arab spring and subprime crises have a significant impact on the time path evolution of market efficiency.
Weakly Nonlinear Waves with Slowly-Varying Speed | Chikwendu ...
African Journals Online (AJOL)
A previously developed method of generating uniformly valid, multiple- scale asymptotic expansions for the solution of weakly nonlinear one-dimensional wave equations is applied to problems with slowly-varying speed. The method is also shown to be applicable specifically to periodic initial data.
Karlovy Varys linastub kaks Eesti filmi / Andris Feldmanis
Feldmanis, Andris, 1982-
2007-01-01
Ilmar Raagi mängufilm "Klass" osaleb 42. Karlovy Vary rahvusvahelise filmifestivali võistlusprogrammis "East of the West" ja Asko Kase lühimängufilm "Zen läbi prügi" on valitud festivali kõrvalprogrammi "Forum of Independents"
570 comparative evaluation of concrete properties with varying
African Journals Online (AJOL)
Osondu
2013-09-03
Sep 3, 2013 ... Periwinkle shell ash; Varying proportions. Introduction. Building construction works and Civil. Engineering practice in Nigeria depend, to a very large extent, on concrete as major construction material. The versatility, strength and durability of cement are of utmost priority over other construction materials.
Effect of varying concentrations of orally ingested glucose on platelet ...
African Journals Online (AJOL)
The physiologic basis of bleeding is a function of normal platelets and coagulation factors. This study is aimed at ascertaining the effect of varying concentrations of orally ingested glucose on platelet count and hemoglobin concentration during menstruation. Forty menstruating students between the ages of 18 and 25 from ...
Modelling Flow over Stepped Spillway with Varying Chute Geometry ...
African Journals Online (AJOL)
This study has modeled some characteristics of the flows over stepped spillway with varying chute geometry through a laboratory investigation. Using six physically built stepped spillway models, with each having six horizontal plain steps at 4cm constant height, 30 cm width and respective chute slope angles at 310, 320, ...
Nonlinear MPC Design for Identified Nonlinear Parameter Varying (NPV Model
Directory of Open Access Journals (Sweden)
Jiangang Lu
2012-09-01
Full Text Available In this paper, a novel nonlinear model predictive controller (MPC is proposed based on an identified nonlinear parameter varying (NPV model. Firstly, an NPV model scheme is present for process identification, which is featured by its nonlinear hybrid Hammerstein model structure and varying model parameters. The hybrid Hammerstein model combines a normalized static artificial neural network with a linear transfer function to identify general nonlinear systems at each fixed working point. Meanwhile, a model interpolating philosophy is utilized to obtain the global model across the whole operation domain. The NPV model considers both the nonlinearity of transition dynamics due to the variation of the working-point and the nonlinear mapping from the input to the output at fixed working points. Moreover, under the new NPV framework, the control action is computed via a multistep linearization method aimed for nonlinear optimization problems. In the proposed scheme, only low cost tests are needed for system identification and the controller can achieve better output performance than MPC methods based on linear parameter varying (LPV models. Numerical examples validate the effectiveness of the proposed approach. Keywords: Nonlinear parameter varying (NPV, Hammerstein model, nonlinear MPC.
Additional Surgery after Breast-Conserving Surgery Varies Widely
A study published in the Feb. 1, 2012, issue of JAMA found that the number of women who have one or more additional surgeries to remove suspected residual tumor tissue (re-excisions) following breast-conserving surgery (BCS) for breast cancer varies widely across surgeons and hospitals.
Steady shear viscosity of stirred yoghurts with varying ropiness
van Marle, M.E.; van Marle, M.E.; van den Ende, Henricus T.M.; de Kruif, C.G.; de Kruif, C.G.; Mellema, J.
1999-01-01
Stirred yogurt was viewed as a concentrated dispersion of aggregates consisting of protein particles. The steady-shear behavior of three types of stirred yogurt with varying ropiness was investigated experimentally. To describe the shear-dependent viscosity, a microrheological model was used which
Effects of fertilizer types and varying population on the performance ...
African Journals Online (AJOL)
On the two-year averages,the significant percentage increases in the length of cocoyam cormel under fertilizer types were 67, 93 and 148% by inorganic, organic and inorganic + organic fertilizers, respectively. The significant percentage decreases in the length of cocoyam cormels under varying populations of 10,000, ...
Nutrient Intake and Digestibility of Red Sokoto Bucks Fed Varying ...
African Journals Online (AJOL)
An experiment was conducted to evaluate dry matter intake, total tract digestibility and nitrogen balance by red Sokoto bucks fed varying levels of Gmelina arborea leaf meal (GLM). Diet 1 devoid of GLM served as the control. Diets 2, 3 and 4 had GLM supplemented at 10, 20, 30% levels, respectively. A 4X4 Latin square ...
Eshtehardiha, S.; Poudeh, M. Bayati
2008-10-01
Reliable evaluation of distribution systems is of high importance in the maintenance and expansion of these systems. A time-sequential simulation technique is presented in this paper in which the effects of weather conditions and maintenance methods in the assessment of reliable cost of integrated distribution systems are provided. Time-Varying Weight Factors (TVWF) are defined to investigate the effect of weather conditions and present maintenance methods on Failure rates (FR). In fact, the average Failure Rate (FR) is combined with TVWF to provide time-varying repair times (TVRT) for each component. Similarly, the average Repair Time (RT) is also combined with TVWF to produce Time-Varying-Repair Time (TVRT). An experimental distribution system showed that TVFR has more effects on the interruption costs of the sensitive costumers. It has also significant effects on the indices of all costumers. So, it is necessary to consider TVRT in evaluating the reliability of the network cost.
Vesicle biomechanics in a time-varying magnetic field.
Ye, Hui; Curcuru, Austen
2015-01-01
Cells exhibit distortion when exposed to a strong electric field, suggesting that the field imposes control over cellular biomechanics. Closed pure lipid bilayer membranes (vesicles) have been widely used for the experimental and theoretical studies of cellular biomechanics under this electrodeformation. An alternative method used to generate an electric field is by electromagnetic induction with a time-varying magnetic field. References reporting the magnetic control of cellular mechanics have recently emerged. However, theoretical analysis of the cellular mechanics under a time-varying magnetic field is inadequate. We developed an analytical theory to investigate the biomechanics of a modeled vesicle under a time-varying magnetic field. Following previous publications and to simplify the calculation, this model treated the inner and suspending media as lossy dielectrics, the membrane thickness set at zero, and the electric resistance of the membrane assumed to be negligible. This work provided the first analytical solutions for the surface charges, electric field, radial pressure, overall translational forces, and rotational torques introduced on a vesicle by the time-varying magnetic field. Frequency responses of these measures were analyzed, particularly the frequency used clinically by transcranial magnetic stimulation (TMS). The induced surface charges interacted with the electric field to produce a biomechanical impact upon the vesicle. The distribution of the induced surface charges depended on the orientation of the coil and field frequency. The densities of these charges were trivial at low frequency ranges, but significant at high frequency ranges. The direction of the radial force on the vesicle was dependent on the conductivity ratio between the vesicle and the medium. At relatively low frequencies (biomechanics under a time-varying magnetic field. Biological effects of clinical TMS are not likely to occur via alteration of the biomechanics of brain
Zuk, Nathaniel; Delgutte, Bertrand
2017-07-01
Binaural cues occurring in natural environments are frequently time varying, either from the motion of a sound source or through interactions between the cues produced by multiple sources. Yet, a broad understanding of how the auditory system processes dynamic binaural cues is still lacking. In the current study, we directly compared neural responses in the inferior colliculus (IC) of unanesthetized rabbits to broadband noise with time-varying interaural time differences (ITD) with responses to noise with sinusoidal amplitude modulation (SAM) over a wide range of modulation frequencies. On the basis of prior research, we hypothesized that the IC, one of the first stages to exhibit tuning of firing rate to modulation frequency, might use a common mechanism to encode time-varying information in general. Instead, we found weaker temporal coding for dynamic ITD compared with amplitude modulation and stronger effects of adaptation for amplitude modulation. The differences in temporal coding of dynamic ITD compared with SAM at the single-neuron level could be a neural correlate of "binaural sluggishness," the inability to perceive fluctuations in time-varying binaural cues at high modulation frequencies, for which a physiological explanation has so far remained elusive. At ITD-variation frequencies of 64 Hz and above, where a temporal code was less effective, noise with a dynamic ITD could still be distinguished from noise with a constant ITD through differences in average firing rate in many neurons, suggesting a frequency-dependent tradeoff between rate and temporal coding of time-varying binaural information.NEW & NOTEWORTHY Humans use time-varying binaural cues to parse auditory scenes comprising multiple sound sources and reverberation. However, the neural mechanisms for doing so are poorly understood. Our results demonstrate a potential neural correlate for the reduced detectability of fluctuations in time-varying binaural information at high speeds, as occurs in
Design of crusher liner based on time - varying uncertainty theory
Tang, J. C.; Shi, B. Q.; Yu, H. J.; Wang, R. J.; Zhang, W. Y.
2017-09-01
This article puts forward the time-dependent design method considering the load fluctuation factors for the liner based on the time-varying uncertainty theory. In this method, the time-varying uncertainty design model of liner is constructed by introducing the parameters that affect the wear rate, the volatility and the drift rate. Based on the design example, the timevarying design outline of the moving cone liner is obtained. Based on the theory of minimum wear, the gap curve of wear resistant cavity is designed, and the optimized cavity is obtained by the combination of the thickness of the cone and the cavity gap. Taking the PYGB1821 multi cylinder hydraulic cone crusher as an example, it is proved that the service life of the new liner is improved by more than 14.3%.
Poverty Index With Time Varying Consumption and Income Distributions
Chattopadhyay, Amit K; Mallick, Sushanta K
2016-01-01
In a recent work (Chattopadhyay, A. K. et al, Europhys. Lett. {\\bf 91}, 58003, 2010) based on food consumption statistics, we showed how a stochastic agent based model could represent the time variation of the income distribution statistics in a developing economy, thereby defining an alternative \\enquote{poverty index} (PI) that largely agreed with poverty gap index data. This PI used two variables, the probability density function of the income statistics and a consumption deprivation (CD) function, representing the shortfall in the minimum consumption needed for survival. Since the time dependence of the CD function was introduced there through data extrapolation only and not through an endogenous time dependent series, this model left unexplained how the minimum consumption needed for survival varies with time. The present article overcomes these limitations and arrives at a new unified theoretical structure through time varying consumption and income distributions where trade is only allowed when the inc...
Local Feature Learning for Face Recognition under Varying Poses
DEFF Research Database (Denmark)
Duan, Xiaodong; Tan, Zheng-Hua
2015-01-01
In this paper, we present a local feature learning method for face recognition to deal with varying poses. As opposed to the commonly used approaches of recovering frontal face images from profile views, the proposed method extracts the subject related part from a local feature by removing the pose...... related part in it on the basis of a pose feature. The method has a closed-form solution, hence being time efficient. For performance evaluation, cross pose face recognition experiments are conducted on two public face recognition databases FERET and FEI. The proposed method shows a significant...... recognition improvement under varying poses over general local feature approaches and outperforms or is comparable with related state-of-the-art pose invariant face recognition approaches. Copyright ©2015 by IEEE....
Performance of Traffic Noise Barriers with Varying Cross-Section
Directory of Open Access Journals (Sweden)
Sanja Grubeša
2011-05-01
Full Text Available The efficiency of noise barriers largely depends on their geometry. In this paper, the performance of noise barriers was simulated using the numerical Boundary Element Method (BEM. Traffic noise was particularly considered with its standardized noise spectrum adapted to human hearing. The cross-section of the barriers was varied with the goal of finding the optimum shape in comparison to classical rectangular barriers. The barrier performance was calculated at different receiver points for a fixed barrier height and source position. The magnitude of the insertion loss parameter was used to evaluate the performance change, both in one-third octave bands and as the broadband mean insertion loss value. The proposed barriers of varying cross-section were also compared with a typical T-shape barrier of the same height.
Fault detection in reciprocating compressor valves under varying load conditions
Pichler, Kurt; Lughofer, Edwin; Pichler, Markus; Buchegger, Thomas; Klement, Erich Peter; Huschenbett, Matthias
2016-03-01
This paper presents a novel approach for detecting cracked or broken reciprocating compressor valves under varying load conditions. The main idea is that the time frequency representation of vibration measurement data will show typical patterns depending on the fault state. The problem is to detect these patterns reliably. For the detection task, we make a detour via the two dimensional autocorrelation. The autocorrelation emphasizes the patterns and reduces noise effects. This makes it easier to define appropriate features. After feature extraction, classification is done using logistic regression and support vector machines. The method's performance is validated by analyzing real world measurement data. The results will show a very high detection accuracy while keeping the false alarm rates at a very low level for different compressor loads, thus achieving a load-independent method. The proposed approach is, to our best knowledge, the first automated method for reciprocating compressor valve fault detection that can handle varying load conditions.
Modelling Time-Varying Volatility in Financial Returns
DEFF Research Database (Denmark)
Amado, Cristina; Laakkonen, Helinä
2014-01-01
The “unusually uncertain” phase in the global financial markets has inspired many researchers to study the effects of ambiguity (or “Knightian uncertainty”) on the decisions made by investors and their implications for the capital markets. We contribute to this literature by using a modified...... being captured by a stable GARCH(1,1) process and the second driven by the level of uncertainty in the financial market....... version of the time-varying GARCH model of Amado and Teräsvirta (2013) to analyze whether the increasing uncertainty has caused excess volatility in the US and European government bond markets. In our model, volatility is multiplicatively decomposed into two time-varying conditional components: the first...
Non-minimally coupled varying constants quantum cosmologies
Balcerzak, Adam
2015-01-01
We consider gravity theory with varying speed of light and varying gravitational constant. Both constants are represented by non-minimally coupled scalar fields. We examine the cosmological evolution in the near curvature singularity regime. We find that at the curvature singularity the speed of light goes to infinity while the gravitational constant vanishes. This corresponds to the Newton's Mechanics limit represented by one of the vertex of the Bronshtein-Zelmanov-Okun cube. The cosmological evolution includes both the pre-big-bang and post-big-bang phases separated by the curvature singularity. We also investigate the quantum counterpart of the considered theory and find the probability of transition of the universe from the collapsing pre-big-bang phase to the expanding post-big-bang phase.
Non-minimally coupled varying constants quantum cosmologies
Balcerzak, Adam
2015-04-01
We consider gravity theory with varying speed of light and varying gravitational constant. Both constants are represented by non-minimally coupled scalar fields. We examine the cosmological evolution in the near curvature singularity regime. We find that at the curvature singularity the speed of light goes to infinity while the gravitational constant vanishes. This corresponds to the Newton's Mechanics limit represented by one of the vertex of the Bronshtein-Zelmanov-Okun cube [1,2]. The cosmological evolution includes both the pre-big-bang and post-big-bang phases separated by the curvature singularity. We also investigate the quantum counterpart of the considered theory and find the probability of transition of the universe from the collapsing pre-big-bang phase to the expanding post-big-bang phase.
Control of Linear Parameter Varying Systems with Applications
Mohammadpour, Javad
2012-01-01
Control of Linear Parameter Varying Systems with Applications compiles state-of-the-art contributions on novel analytical and computational methods to address system modeling and identification, complexity reduction, performance analysis and control design for time-varying and nonlinear systems in the LPV framework. The book has an interdisciplinary character by emphasizing techniques that can be commonly applied in various engineering fields. It also includes a rich collection of illustrative applications in diverse domains to substantiate the effectiveness of the design methodologies and provide pointers to open research directions. The book is divided into three parts. The first part collects chapters of a more tutorial character on the background of LPV systems modeling and control. The second part gathers chapters devoted to the theoretical advancement of LPV analysis and synthesis methods to cope with the design constraints such as uncertainties and time delay. The third part of the volume showcases con...
Hemolymph drop impact outcomes on surfaces with varying wettability
Milionis, Athanasios; Ghokulla Krishnan, K.; Loth, Eric
2015-08-01
Insect fouling from coagulated hemolymph and exoskeleton parts is a major challenge in the aerospace industry for the next generation of aerodynamic surfaces, which will employ laminar flow that requires extremely smooth surfaces. However, the wetting physics and dynamics of hemolymph (insect blood) on surfaces are not well understood. The present study seeks to gain a fundamental insight on the effect of surface wetting characteristics and dynamics resulting from a hemolymph drop impact, the first such study. In particular, hemolymph drops extracted from Acheta domesticus were dispensed from a range of heights to vary the kinetic impact on surfaces, which had widely varying water wetting behavior (from superhydrophilic to superhydrophobic). The impact dynamics were investigated with high-speed imaging while the dried residues were studied with optical microscopy. It was found that a superhydrophobic surface (based on thermoplastic with silica nano-particles) was able to significantly reduce hemolymph drop spreading, and even provide complete rebound when impacting on inclined surfaces.
Utilization of varying proportions of maize milling waste and cowpea ...
African Journals Online (AJOL)
Dry matter intake (DMI), daily weight gain (DWG), feed efficiency and economics of including varying levels of MMW and CPS were studied for eight weeks. The DMI and DWG were significantly (p<0.05) higher for diets C, D and E (59.40, 57.60 and 61.00 g/day and 11.94, 10.89 and 11.42 g/day respectively) compared to ...
The value premium and time-varying volatility
Li, X.; Brooks, C.; Miffre, J.
2009-01-01
Numerous studies have documented the failure of the static and conditional capital asset pricing models to explain the difference in returns between value and growth stocks. This paper examines the post-1963 value premium by employing a model that captures the time-varying total risk of the value-minus-growth portfolios. Our results show that the time-series of value premia is strongly and positively correlated with its volatility. This conclusion is robust to the criterion used to sort stock...
Tracking time-varying parameters with local regression
DEFF Research Database (Denmark)
Joensen, Alfred Karsten; Nielsen, Henrik Aalborg; Nielsen, Torben Skov
2000-01-01
This paper shows that the recursive least-squares (RLS) algorithm with forgetting factor is a special case of a varying-coe\\$cient model, and a model which can easily be estimated via simple local regression. This observation allows us to formulate a new method which retains the RLS algorithm, bu......, but extends the algorithm by including polynomial approximations. Simulation results are provided, which indicates that this new method is superior to the classical RLS method, if the parameter variations are smooth....
The Value Premium and Time-Varying Unsystematic Risk
Chris Brooks; Xiafei Li; Joelle Miffre
2007-01-01
Recent research has discussed the possible role of unsystematic risk in explaining equity returns. Simultaneously, but somehow independently, numerous other studies have documented the failure of the static and conditional capital asset pricing models to explain the differences in returns between value and growth stocks. This paper examines the post-1963 value premium by employing a model that captures the time-varying total risk of the value-minus-growth portfolios. In accordance with existi...
Nutrient intake, digestibility and growth rate of rabbits fed varying ...
African Journals Online (AJOL)
Forty young rabbits were fed on five diets varying in cassava leaf meal (CLM} levels from 0% to 60%. Dry matter and nutrient intake and digestibility, weight gain and economics of CLM inclusion were determined The DMI (g/d) ranged from 44.24 (60% CLM) to 66.85 (15% CLM); daily live weight gain (LWG, g/d) from 8.43 ...
Premorbid IQ varies across different definitions of schizophrenia
DEFF Research Database (Denmark)
Urfer Parnas, Annick; Jansson, Lennart; Handest, Peter
2007-01-01
The nature of the association between IQ and schizophrenia is still unclear. So far no study addressed this issue in relation to the breadth or scope of the very concept of schizophrenia. We examined the premorbid IQ in a polydiagnostic study with four classifications of schizophrenia: ICD-8/9, I...... of schizophrenia in relation to IQ revealed associations between low premorbid IQ and hallucinations as well as negative symptoms. It is concluded that premorbid IQ varies across different definitions of schizophrenia....
Twist defect in chiral photonic structures with spatially varying pitch
Chen, Jiun-Yeu; Chen, Lien-Wen
2005-04-01
The properties of photonic defect modes in a chiral photonic structure were investigated using the finite element method. By stacking two cholesteric liquid crystal (ChLC) films, the defect mode due to the introduction of a twist defect was considered in both cases of chiral structures with constant pitch and spatially varying pitch. Two types of linear pitch gradients for achieving a broadband reflection were analysed, and the number of chiral pitches required for establishing the stop band was simulated. The effect of a finite sample thickness on the energy density distribution of the defect mode and on the required polarization of the incident light to excite the defect mode was studied. In both cases of constant pitch and spatially varying pitch, an unusual crossover behaviour in reflection at the defect resonance wavelength of a single circularly polarized mode appears when the structure thickness increases beyond a specific value. The energy distribution inside the sample also reveals the unusual distribution. Two different resonance wavelengths can be created by a twist defect in the ChLC composite film with linearly varying pitch, while only one resonance wavelength can be created in the identical film with constant pitch.
Modeling information diffusion in time-varying community networks
Cui, Xuelian; Zhao, Narisa
2017-12-01
Social networks are rarely static, and they typically have time-varying network topologies. A great number of studies have modeled temporal networks and explored social contagion processes within these models; however, few of these studies have considered community structure variations. In this paper, we present a study of how the time-varying property of a modular structure influences the information dissemination. First, we propose a continuous-time Markov model of information diffusion where two parameters, mobility rate and community attractiveness, are introduced to address the time-varying nature of the community structure. The basic reproduction number is derived, and the accuracy of this model is evaluated by comparing the simulation and theoretical results. Furthermore, numerical results illustrate that generally both the mobility rate and community attractiveness significantly promote the information diffusion process, especially in the initial outbreak stage. Moreover, the strength of this promotion effect is much stronger when the modularity is higher. Counterintuitively, it is found that when all communities have the same attractiveness, social mobility no longer accelerates the diffusion process. In addition, we show that the local spreading in the advantage group has been greatly enhanced due to the agglomeration effect caused by the social mobility and community attractiveness difference, which thus increases the global spreading.
Delivery of continuously-varying stimuli using channelrhodopsin-2.
Tchumatchenko, Tatjana; Newman, Jonathan P; Fong, Ming-fai; Potter, Steve M
2013-01-01
To study sensory processing, stimuli are delivered to the sensory organs of animals and evoked neural activity is recorded downstream. However, noise and uncontrolled modulatory input can interfere with repeatable delivery of sensory stimuli to higher brain regions. Here we show how channelrhodopsin-2 (ChR2) can be used to deliver continuous, subthreshold, time-varying currents to neurons at any point along the sensory-motor pathway. To do this, we first deduce the frequency response function of ChR2 using a Markov model of channel kinetics. We then confirm ChR2's frequency response characteristics using continuously-varying optical stimulation of neurons that express one of three ChR2 variants. We find that wild-type ChR2 and the E123T/H134R mutant ("CheTA") can pass continuously-varying subthreshold stimuli with frequencies up to ~70 Hz. Additionally, we find that wild-type ChR2 exhibits a strong resonance at ~6-10 Hz. Together, these results indicate that ChR2-derived optogenetic tools are useful for delivering highly repeatable artificial stimuli that mimic in vivo synaptic bombardment.
Online dynamic mode decomposition for time-varying systems
Zhang, Hao; Rowley, Clarence; Deem, Eric; Cattafesta, Louis
2017-11-01
Dynamic mode decomposition (DMD) is a popular technique for modal decomposition, flow analysis, and reduced-order modeling. In situations where a system is time varying, one would like to update the system's description online as time evolves. This work provides an efficient method for computing the DMD matrix in real time, updating the approximation of a system's dynamics as new data becomes available. The algorithm does not require storage of past data, and computes the exact DMD matrix using rank-1 updates. A weighting factor that places less weight on older data can be incorporated in a straightforward manner, making the method particularly well suited to time-varying systems. The efficiency of the method is compared against several existing DMD algorithms: for problems in which the state dimension is less than about 200, the proposed algorithm is the most efficient for real-time computation, and it can be orders of magnitude more efficient than the standard DMD algorithm. The method is demonstrated on several examples, including a time-varying linear system and a more complex example using data from a wind tunnel experiment. Supported by AFOSR Grant FA9550-14-1-0289, and by DARPA award HR0011-16-C-0116.
Mass-varying massive gravity with k-essence
Energy Technology Data Exchange (ETDEWEB)
Tannukij, Lunchakorn [Mahidol University, Department of Physics, Faculty of Science, Bangkok (Thailand); Wongjun, Pitayuth [Naresuan University, The Institute for Fundamental Study, Phitsanulok (Thailand); Thailand Center of Excellence in Physics, Ministry of Education, Bangkok (Thailand)
2016-01-15
For a large class of mass-varying massive-gravity models, the graviton mass cannot provide the late-time cosmic expansion of the universe due to its vanishing at late time. In this work, we propose a new class of mass-varying massive gravity models, in which the graviton mass varies according to a kinetic term of a k-essence field. By using a more general form of the fiducial metric, we found a solution such that a non-vanishing graviton mass can drive the accelerated expansion of the universe at late time. We also perform dynamical analyses of such a model and find that without introducing the k-essence Lagrangian, the graviton mass can be responsible for both dark contents of the universe, namely dark energy, which drives the accelerated expansion of the universe, and non-relativistic matter, which plays the role of dark matter. Moreover, by including the k-essence Lagrangian, we find that it is possible to alleviate the so-called cosmic coincidence problem. (orig.)
VariVis: a visualisation toolkit for variation databases
Directory of Open Access Journals (Sweden)
Smith Timothy D
2008-04-01
Full Text Available Abstract Background With the completion of the Human Genome Project and recent advancements in mutation detection technologies, the volume of data available on genetic variations has risen considerably. These data are stored in online variation databases and provide important clues to the cause of diseases and potential side effects or resistance to drugs. However, the data presentation techniques employed by most of these databases make them difficult to use and understand. Results Here we present a visualisation toolkit that can be employed by online variation databases to generate graphical models of gene sequence with corresponding variations and their consequences. The VariVis software package can run on any web server capable of executing Perl CGI scripts and can interface with numerous Database Management Systems and "flat-file" data files. VariVis produces two easily understandable graphical depictions of any gene sequence and matches these with variant data. While developed with the goal of improving the utility of human variation databases, the VariVis package can be used in any variation database to enhance utilisation of, and access to, critical information.
Sensor trustworthiness in uncertain time varying stochastic environments
Verma, Ajay; Fernandes, Ronald; Vadakkeveedu, Kalyan
2011-06-01
Persistent surveillance applications require unattended sensors deployed in remote regions to track and monitor some physical stimulant of interest that can be modeled as output of time varying stochastic process. However, the accuracy or the trustworthiness of the information received through a remote and unattended sensor and sensor network cannot be readily assumed, since sensors may get disabled, corrupted, or even compromised, resulting in unreliable information. The aim of this paper is to develop information theory based metric to determine sensor trustworthiness from the sensor data in an uncertain and time varying stochastic environment. In this paper we show an information theory based determination of sensor data trustworthiness using an adaptive stochastic reference sensor model that tracks the sensor performance for the time varying physical feature, and provides a baseline model that is used to compare and analyze the observed sensor output. We present an approach in which relative entropy is used for reference model adaptation and determination of divergence of the sensor signal from the estimated reference baseline. We show that that KL-divergence is a useful metric that can be successfully used in determination of sensor failures or sensor malice of various types.
Social contagions on time-varying community networks
Liu, Mian-Xin; Wang, Wei; Liu, Ying; Tang, Ming; Cai, Shi-Min; Zhang, Hai-Feng
2017-05-01
Time-varying community structures exist widely in real-world networks. However, previous studies on the dynamics of spreading seldom took this characteristic into account, especially those on social contagions. To study the effects of time-varying community structures on social contagions, we propose a non-Markovian social contagion model on time-varying community networks based on the activity-driven network model. A mean-field theory is developed to analyze the proposed model. Through theoretical analyses and numerical simulations, two hierarchical features of the behavior adoption processes are found. That is, when community strength is relatively large, the behavior can easily spread in one of the communities, while in the other community the spreading only occurs at higher behavioral information transmission rates. Meanwhile, in spatial-temporal evolution processes, hierarchical orders are observed for the behavior adoption. Moreover, under different information transmission rates, three distinctive patterns are demonstrated in the change of the whole network's final adoption proportion along with the growing community strength. Within a suitable range of transmission rate, an optimal community strength can be found that can maximize the final adoption proportion. Finally, compared with the average activity potential, the promoting or inhibiting of social contagions is much more influenced by the number of edges generated by active nodes.
On enhanced time-varying distributed H systems
Directory of Open Access Journals (Sweden)
Sergey Verlan
2002-11-01
Full Text Available An enhanced time-varying distributed H system (ETVDH system is a slightly different definition of the time-varying distributed H system (TVDH system [9] and it was proposed by M. Margenstern and Yu. Rogozhin in [4] under the name of "extended time-varying distributed H system''. The main difference is that the components of the ETVDH system are H systems and therefore splicing rules may be applied more than once as it is done in TVDH systems. This leads to difficulties in investigating the behavior of such systems because they have a higher level of parallelism. It is proved that ETVDH systems of degree 2 (i.e. with 2 components generate all recursively enumerable languages in a sequential way [7] and that ETVDH systems of degree 4 generate all recursively enumerable languages in a "parallel'' way, modelling a formal type-0 grammar [11]. In this paper we improve the last result and we present an ETVDH system of degree 3 which generates all recursively enumerable languages modelling type-0 formal grammars. The problem of the existence of ETVDH systems of degree 2 which generate all recursively enumerable languages in a "parallel'' way is left open.
VISAR fringe analysis under extreme spatially varying shock loading
Erskine, David; Fratanduono, Dayne
2017-06-01
Many VISAR velocity interferometers employ a streak camera to record fringes along the spatial axis (Y) of a target, versus time. When the shock loading (thus velocity history) varies rapidly versus Y, the fringe analysis challenges traditional algorithms since the Y-spacing of fringes can vary strongly with Y, and be significantly different than the uniform pre-shock (bias) spacing. For traditional colum-by-column analysis the intensity signal shape would be a sinusoid with rapidly varying frequency (chirped), which can confuse a traditional algorithm expecting a monochromatic peak in Fourier space. And for a traditional push-pull row-by-row approach, the phase steps are irregular. We describe preliminary success in analyzing such data in simulation. We find it useful to (a) separate the nonfringing component from the data early; (b) maximize linearity of a plot of fringing magnitude versus nonfringing intensity to choose optimal weight values; (c) when using a row-by-row approach sampling 0, 90, 180, and 270 degrees phase we add a fifth sample at 360 degrees, which is averaged with the 0 degree sample and replaces it. This increases the robustness to variable phase step (following P. Hariharan). The pre-shock and post-shock regions are separately processed/concatenated. Prepared by LLNL under Contract DE-AC52-07NA27344.
Neural processing of reward magnitude under varying attentional demands.
Stoppel, Christian Michael; Boehler, Carsten Nicolas; Strumpf, Hendrik; Heinze, Hans-Jochen; Hopf, Jens-Max; Schoenfeld, Mircea Ariel
2011-04-06
Central to the organization of behavior is the ability to represent the magnitude of a prospective reward and the costs related to obtaining it. Therein, reward-related neural activations are discounted in dependence of the effort required to resolve a given task. Varying attentional demands of the task might however affect reward-related neural activations. Here we employed fMRI to investigate the neural representation of expected values during a monetary incentive delay task with varying attentional demands. Following a cue, indicating at the same time the difficulty (hard/easy) and the reward magnitude (high/low) of the upcoming trial, subjects performed an attention task and subsequently received feedback about their monetary reward. Consistent with previous results, activity in anterior-cingulate, insular/orbitofrontal and mesolimbic regions co-varied with the anticipated reward-magnitude, but also with the attentional requirements of the task. These activations occurred contingent on action-execution and resembled the response time pattern of the subjects. In contrast, cue-related activations, signaling the forthcoming task-requirements, were only observed within attentional control structures. These results suggest that anticipated reward-magnitude and task-related attentional demands are concurrently processed in partially overlapping neural networks of anterior-cingulate, insular/orbitofrontal, and mesolimbic regions. Copyright © 2011 Elsevier B.V. All rights reserved.
Varying hemin concentrations affect Porphyromonas gingivalis strains differently.
Ohya, Manabu; Cueno, Marni E; Tamura, Muneaki; Ochiai, Kuniyasu
2016-05-01
Porphyromonas gingivalis requires heme to grow, however, heme availability and concentration in the periodontal pockets vary. Fluctuations in heme concentration may affect each P. gingivalis strain differently, however, this was never fully demonstrated. Here, we elucidated the effects of varying hemin concentrations in representative P. gingivalis strains. Throughout this study, representative P. gingivalis strains [FDC381 (type I), MPWIb-01 (type Ib), TDC60 (type II), ATCC49417 (type III), W83 (type IV), and HNA99 (type V)] were used and grown for 24 h in growth media under varying hemin concentrations (5 × , 1 × , 0.5 × , 0.1 × ). Samples were lysed and protein standardized. Arg-gingipain (Rgp), H2O2, and superoxide dismutase (SOD) levels were subsequently measured. We focused our study on 24 h-grown strains which excluded MPWIb-01 and HNA99. Rgp activity among the 4 remaining strains varied with Rgp peaking at: 1 × for FDC381, 5 × for TDC60, 0.5 × for ATCC49417, 5 × and 0.5 × for W83. With regards to H2O2 and SOD amounts: FDC381 had similar H2O2 amounts in all hemin concentrations while SOD levels varied; TDC60 had the lowest H2O2 amount at 1 × while SOD levels became higher in relation to hemin concentration; ATCC49417 also had similar H2O2 amounts in all hemin concentrations while SOD levels were higher at 1 × and 0.5 × ; and W83 had statistically similar H2O2 and SOD amounts regardless of hemin concentration. Our results show that variations in hemin concentration affect each P. gingivalis strain differently. Published by Elsevier Ltd.
Time-varying value of electric energy efficiency
Energy Technology Data Exchange (ETDEWEB)
Mims, Natalie A.; Eckman, Tom; Goldman, Charles
2017-06-30
Electric energy efficiency resources save energy and may reduce peak demand. Historically, quantification of energy efficiency benefits has largely focused on the economic value of energy savings during the first year and lifetime of the installed measures. Due in part to the lack of publicly available research on end-use load shapes (i.e., the hourly or seasonal timing of electricity savings) and energy savings shapes, consideration of the impact of energy efficiency on peak demand reduction (i.e., capacity savings) has been more limited. End-use load research and the hourly valuation of efficiency savings are used for a variety of electricity planning functions, including load forecasting, demand-side management and evaluation, capacity and demand response planning, long-term resource planning, renewable energy integration, assessing potential grid modernization investments, establishing rates and pricing, and customer service. This study reviews existing literature on the time-varying value of energy efficiency savings, provides examples in four geographically diverse locations of how consideration of the time-varying value of efficiency savings impacts the calculation of power system benefits, and identifies future research needs to enhance the consideration of the time-varying value of energy efficiency in cost-effectiveness screening analysis. Findings from this study include: -The time-varying value of individual energy efficiency measures varies across the locations studied because of the physical and operational characteristics of the individual utility system (e.g., summer or winter peaking, load factor, reserve margin) as well as the time periods during which savings from measures occur. -Across the four locations studied, some of the largest capacity benefits from energy efficiency are derived from the deferral of transmission and distribution system infrastructure upgrades. However, the deferred cost of such upgrades also exhibited the greatest range
Reduced dielectric response in spatially varying electric fields
DEFF Research Database (Denmark)
Hansen, Jesper Schmidt
2015-01-01
In this paper, the dynamical equation for polarization is derived. From this the dielectric response to a spatially varying electric field is analyzed showing a reduced response due to flux of polarization in the material. This flux is modeled as a diffusive process through linear constitutive...... relations between the flux and the gradient of the polarization. Comparison between the theory and molecular dynamics simulations confirms this effect. The effect is significant for small length scale electric field variations and the inclusion of the flux is thus important in nanoscale modeling...
Varying the exchange interaction between NiO nanoparticles
DEFF Research Database (Denmark)
Bahl, Christian Robert Haffenden; Mørup, Steen
2006-01-01
We demonstrate that exchange interactions between antiferromagnetic nanoparticles of 57Fe-doped NiO can be varied by simple macroscopic treatments. Mössbauer spectroscopy studies of the superparamagnetic relaxation behaviour show that grinding or suspension in water of nanoparticles of NiO can si...... significantly reduce interparticle interactions. Slow drying of aqueous suspensions of NiO nanoparticles did not lead to enhanced interparticle interactions. This is opposite to the behaviour of α-Fe2O3 (hematite) nanoparticles....
Adjusting Permittivity by Blending Varying Ratios of SWNTs
Tour, James M.; Stephenson, Jason J.; Higginbotham, Amanda
2012-01-01
A new composite material of singlewalled carbon nanotubes (SWNTs) displays radio frequency (0 to 1 GHz) permittivity properties that can be adjusted based upon the nanotube composition. When varying ratios of raw to functionalized SWNTs are blended into the silicone elastomer matrix at a total loading of 0.5 percent by weight, a target real permittivity value can be obtained between 70 and 3. This has particular use for designing materials for microwave lenses, microstrips, filters, resonators, high-strength/low-weight electromagnetic interference (EMI) shielding, antennas, waveguides, and low-loss magneto-dielectric products for applications like radome construction.
Non-coherent Network Coding: An Arbitrarily Varying Channel Approach
Jafari Siavoshani, Mahdi; Yang, Shenghao; Yeung, Raymond
2012-01-01
In this paper, we propose an “arbitrarily varying channel” (AVC) approach to study the capacity of non-coherent transmission in a network that employs randomized linear network coding. The network operation is modeled by a matrix channel over a ﬁnite ﬁeld where the transfer matrix changes arbitrarily from time-slot to time-slot but up to a known distribution over its rank. By extending the AVC results to this setup, we characterize the capacity of such a non-coherent transmission scheme and s...
Budgerigar flight in a varying environment: flight at distinct speeds?
Schiffner, Ingo; Srinivasan, Mandyam V.
2016-01-01
How do flying birds respond to changing environments? The behaviour of budgerigars, Melopsittacus undulatus, was filmed as they flew through a tapered tunnel. Unlike flying insects���which vary their speed progressively and continuously by holding constant the optic flow induced by the walls���the birds showed a tendency to fly at only two distinct, fixed speeds. They switched between a high speed in the wider section of the tunnel, and a low speed in the narrower section. The transition betw...
Timed arrays wideband and time varying antenna arrays
Haupt, Randy L
2015-01-01
Introduces timed arrays and design approaches to meet the new high performance standards The author concentrates on any aspect of an antenna array that must be viewed from a time perspective. The first chapters briefly introduce antenna arrays and explain the difference between phased and timed arrays. Since timed arrays are designed for realistic time-varying signals and scenarios, the book also reviews wideband signals, baseband and passband RF signals, polarization and signal bandwidth. Other topics covered include time domain, mutual coupling, wideband elements, and dispersion. The auth
Dynamics of a Delay-Varying Computer Virus Propagation Model
Directory of Open Access Journals (Sweden)
Jianguo Ren
2012-01-01
Full Text Available By considering the varying latency period of computer virus, we propose a novel model for computer virus propagation in network. Under this model, we give the threshold value determining whether or not the virus finally dies out, and study the local stability of the virus-free and virus equilibrium. It is found that the model may undergo a Hopf bifurcation. Next, we use different methods to prove the global asymptotic stability of the equilibria: the virus-free equilibrium by using the direct Lyapunov method and virus equilibrium by using a geometric approach. Finally, some numerical examples are given to support our conclusions.
A von Bertalanffy growth model with a seasonally varying coefficient
Cloern, James E.; Nichols, Frederic H.
1978-01-01
The von Bertalanffy model of body growth is inappropriate for organisms whose growth is restricted to a seasonal period because it assumes that growth rate is invariant with time. Incorporation of a time-varying coefficient significantly improves the capability of the von Bertalanffy equation to describe changing body size of both the bivalve mollusc Macoma balthicain San Francisco Bay and the flathead sole, Hippoglossoides elassodon, in Washington state. This simple modification of the von Bertalanffy model should offer improved predictions of body growth for a variety of other aquatic animals.
Context dependent substitution biases vary within the human genome
Directory of Open Access Journals (Sweden)
Nevarez P Andrew
2010-09-01
Full Text Available Abstract Background Models of sequence evolution typically assume that different nucleotide positions evolve independently. This assumption is widely appreciated to be an over-simplification. The best known violations involve biases due to adjacent nucleotides. There have also been suggestions that biases exist at larger scales, however this possibility has not been systematically explored. Results To address this we have developed a method which identifies over- and under-represented substitution patterns and assesses their overall impact on the evolution of genome composition. Our method is designed to account for biases at smaller pattern sizes, removing their effects. We used this method to investigate context bias in the human lineage after the divergence from chimpanzee. We examined bias effects in substitution patterns between 2 and 5 bp long and found significant effects at all sizes. This included some individual three and four base pair patterns with relatively large biases. We also found that bias effects vary across the genome, differing between transposons and non-transposons, between different classes of transposons, and also near and far from genes. Conclusions We found that nucleotides beyond the immediately adjacent one are responsible for substantial context effects, and that these biases vary across the genome.
Cysts of Gastrointestinal Origin in Children: Varied Presentation
Tiwari, Charu; Waghmare, Mukta; Makhija, Deepa; Khedkar, Kiran
2017-01-01
Purpose Abdominal cysts of gastrointestinal origin are rare. Their rarity and varied clinical presentations make their pre-operative diagnosis difficult. Methods Fourteen patients with histological diagnosis of cysts of gastrointestinal origin admitted between 2009 and 2015 were retrospectively analyzed with respect to age, sex, clinical presentation, diagnostic modality, site and type of cyst, management, outcome and follow-up. Results The mean age at presentation was 4 years and there were six males and eight females. Abdominal pain was the most common presenting symptom. Five patients had an acute presentation-three had distal ileal mesenteric cysts and two had ileal duplication cyst sharing a common wall with ileum. Six patients presented with chronic abdominal pain and lump—three patients had omental cysts and three had mesenteric cysts—two of these in distal ileum and one in sigmoid colon. Two patients presented with antenatally diagnosed palpable abdominal lump. One had a mesenteric cyst of the ileum and the other had a distal ileal duplication cyst which required excision with resection and anastomosis. One patient had an atypical presentation. He was a known case of sickle cell trait and had presented with vague abdominal pain, recurrent cough and multiple episodes of haemoptysis over a period of one year. At laparotomy, gastric duplication cyst was found which was excised completely. Histopathology confirmed the diagnosis. Conclusion Cysts of gastrointestinal origin are rare and have varied presentation. Surgical excision is the mainstay of treatment. The results and prognosis are good. PMID:28730133
Study of selected phenotype switching strategies in time varying environment
Energy Technology Data Exchange (ETDEWEB)
Horvath, Denis, E-mail: horvath.denis@gmail.com [Centre of Interdisciplinary Biosciences, Institute of Physics, Faculty of Science, P.J. Šafárik University in Košice, Jesenná 5, 040 01 Košice (Slovakia); Brutovsky, Branislav, E-mail: branislav.brutovsky@upjs.sk [Department of Biophysics, Institute of Physics, P.J. Šafárik University in Košice, Jesenná 5, 040 01 Košice (Slovakia)
2016-03-22
Population heterogeneity plays an important role across many research, as well as the real-world, problems. The population heterogeneity relates to the ability of a population to cope with an environment change (or uncertainty) preventing its extinction. However, this ability is not always desirable as can be exemplified by an intratumor heterogeneity which positively correlates with the development of resistance to therapy. Causation of population heterogeneity is therefore in biology and medicine an intensively studied topic. In this paper the evolution of a specific strategy of population diversification, the phenotype switching, is studied at a conceptual level. The presented simulation model studies evolution of a large population of asexual organisms in a time-varying environment represented by a stochastic Markov process. Each organism disposes with a stochastic or nonlinear deterministic switching strategy realized by discrete-time models with evolvable parameters. We demonstrate that under rapidly varying exogenous conditions organisms operate in the vicinity of the bet-hedging strategy, while the deterministic patterns become relevant as the environmental variations are less frequent. Statistical characterization of the steady state regimes of the populations is done using the Hellinger and Kullback–Leibler functional distances and the Hamming distance. - Highlights: • Relation between phenotype switching and environment is studied. • The Markov chain Monte Carlo based model is developed. • Stochastic and deterministic strategies of phenotype switching are utilized. • Statistical measures of the dynamic heterogeneity reveal universal properties. • The results extend to higher lattice dimensions.
Study of runoff generation responding to varied catchment morphology
Zhang, Jun; Han, Dawei
2017-04-01
Hydrological processes are inevitably related to the catchment morphology, which includes hillslope, area, shape and drainage network, etc. The topic has attracted attentions of numerous studies on it. The previous studies mostly compare runoff generation processes in various catchments to derive empirical equations. However, due to the variability of catchment properties and climate conditions, it is highly possible that other factors would compound the results when one tries to focus on one particular catchment property. In this study, virtual catchments are built based on an actual catchment, the Brue catchment in UK. These catchments are assigned with varied morphology, including hillslope, area, width and length etc., and are simulated using a fully distributed model. When one catchment property is tested, the other properties are assumed as control variables. The whole hydrological processes are compared among all the catchments, in which the time to peak (Tp) and peak volume (Qp) are mainly considered as the assessment indicators. The results show that catchment morphology has significant influence on runoff generation. To illustrate, when the average slope of the catchment increases, the peak volume increases and the time to peak decreases following particular curves. Moreover, when the slope increases to a certain threshold level, the influence of slope on runoff generation is plateaued. An empirical model is built according to the results, which is able to provide a useful guide for runoff generation in varied catchments.
Study of selected phenotype switching strategies in time varying environment
Horvath, Denis; Brutovsky, Branislav
2016-03-01
Population heterogeneity plays an important role across many research, as well as the real-world, problems. The population heterogeneity relates to the ability of a population to cope with an environment change (or uncertainty) preventing its extinction. However, this ability is not always desirable as can be exemplified by an intratumor heterogeneity which positively correlates with the development of resistance to therapy. Causation of population heterogeneity is therefore in biology and medicine an intensively studied topic. In this paper the evolution of a specific strategy of population diversification, the phenotype switching, is studied at a conceptual level. The presented simulation model studies evolution of a large population of asexual organisms in a time-varying environment represented by a stochastic Markov process. Each organism disposes with a stochastic or nonlinear deterministic switching strategy realized by discrete-time models with evolvable parameters. We demonstrate that under rapidly varying exogenous conditions organisms operate in the vicinity of the bet-hedging strategy, while the deterministic patterns become relevant as the environmental variations are less frequent. Statistical characterization of the steady state regimes of the populations is done using the Hellinger and Kullback-Leibler functional distances and the Hamming distance.
Sensitivity of solar g-modes to varying G cosmologies
Guenther, D. B.; Sills, Ken; Demarque, Pierre; Krauss, Lawrence M.
1995-01-01
The sensitivity of the solar g-mode oscillation spectrum to variability in the universal gravitational constant G is described. Solar models in varying G cosmologies were constructed by evolving a zero-age main-sequence stellar model to the Sun's current age, while allowing the value of G to change according to the power law G(t) proportional to t(exp -beta), where Beta approximately equals delta G/GH and H is the Hubble constant. All solar models were constrained to the observed luminosity and radius at the current age of the Sun by adjusting the helium abundance and the mixing-length parameter of the models in the usual way for standard stellar models. Low-l g-mode oscillation periods were calculated for each of the models and compared to the claimed observation of the solar g-mode oscillation spectrum by Hill & Gu (1990). If one accepts Hill & Gu's claims, then within the uncertainties of the physics of the solar model calculation, our models rule out all but (delta G/GH) less than approximately 0.05. In other words, we conclude that G could not have varied by more than 2% over the past 4.5 Gyr, the lifetime of the present-day Sun. This result lends independent support to the validity of the standard solar model.
Tolerable Time-Varying Overflow on Grass-Covered Slopes
Directory of Open Access Journals (Sweden)
Steven A. Hughes
2015-03-01
Full Text Available Engineers require estimates of tolerable overtopping limits for grass-covered levees, dikes, and embankments that might experience steady overflow. Realistic tolerance estimates can be used for both resilient design and risk assessment. A simple framework is developed for estimating tolerable overtopping on grass-covered slopes caused by slowly-varying (in time overtopping discharge (e.g., events like storm surges or river flood waves. The framework adapts the well-known Hewlett curves of tolerable limiting velocity as a function of overflow duration. It has been hypothesized that the form of the Hewlett curves suggests that the grass erosion process is governed by the flow work on the slope above a critical threshold velocity (referred to as excess work, and the tolerable erosional limit is reached when the cumulative excess work exceeds a given value determined from the time-dependent Hewlett curves. The cumulative excess work is expressed in terms of overflow discharge above a critical discharge that slowly varies in time, similar to a discharge hydrograph. The methodology is easily applied using forecast storm surge hydrographs at specific locations where wave action is minimal. For preliminary planning purposes, when storm surge hydrographs are unavailable, hypothetical equations for the water level and overflow discharge hydrographs are proposed in terms of the values at maximum overflow and the total duration of overflow. An example application is given to illustrate use of the methodology.
A hierarchical nest survival model integrating incomplete temporally varying covariates
Converse, Sarah J.; Royle, J. Andrew; Adler, Peter H.; Urbanek, Richard P.; Barzan, Jeb A.
2013-01-01
Nest success is a critical determinant of the dynamics of avian populations, and nest survival modeling has played a key role in advancing avian ecology and management. Beginning with the development of daily nest survival models, and proceeding through subsequent extensions, the capacity for modeling the effects of hypothesized factors on nest survival has expanded greatly. We extend nest survival models further by introducing an approach to deal with incompletely observed, temporally varying covariates using a hierarchical model. Hierarchical modeling offers a way to separate process and observational components of demographic models to obtain estimates of the parameters of primary interest, and to evaluate structural effects of ecological and management interest. We built a hierarchical model for daily nest survival to analyze nest data from reintroduced whooping cranes (Grus americana) in the Eastern Migratory Population. This reintroduction effort has been beset by poor reproduction, apparently due primarily to nest abandonment by breeding birds. We used the model to assess support for the hypothesis that nest abandonment is caused by harassment from biting insects. We obtained indices of blood-feeding insect populations based on the spatially interpolated counts of insects captured in carbon dioxide traps. However, insect trapping was not conducted daily, and so we had incomplete information on a temporally variable covariate of interest. We therefore supplemented our nest survival model with a parallel model for estimating the values of the missing insect covariates. We used Bayesian model selection to identify the best predictors of daily nest survival. Our results suggest that the black fly Simulium annulus may be negatively affecting nest survival of reintroduced whooping cranes, with decreasing nest survival as abundance of S. annulus increases. The modeling framework we have developed will be applied in the future to a larger data set to evaluate the
Varying domains in a general class of sublinear elliptic problems
Directory of Open Access Journals (Sweden)
Santiago Cano-Casanova
2004-05-01
Full Text Available In this paper we use the linear theory developed in [8] and [9] to show the continuous dependence of the positive solutions of a general class of sublinear elliptic boundary value problems of mixed type with respect to the underlying domain. Our main theorem completes the results of Daners and Dancer [12] -and the references there in-, where the classical Robin problem was dealt with. Besides the fact that we are working with mixed non-classical boundary conditions, it must be mentioned that this paper is considering problems where bifurcation from infinity occurs; now a days, analyzing these general problems, where the coefficients are allowed to vary and eventually vanishing or changing sign, is focusing a great deal of attention -as they give rise to metasolutions (e.g., [20]-.
Educational differentials in disability vary across and within welfare regimes
DEFF Research Database (Denmark)
Cambois, Emmanuelle; Solé-Auró, Aïda; Brønnum-Hansen, Henrik
2016-01-01
BACKGROUND: Social differentials in disability prevalence exist in all European countries, but their scale varies markedly. To improve understanding of this variation, the article focuses on each end of the social gradient. It compares the extent of the higher disability prevalence in low social...... groups (referred to as disability disadvantage) and of the lower prevalence in high social groups (disability advantage); country-specific advantages/disadvantages are discussed regarding the possible influence of welfare regimes. METHODS: Cross-sectional disability prevalence is measured by longstanding...... and Germany (youngest age-band). There were notable differences within welfare regime groups. CONCLUSIONS: The country-specific disability advantages/disadvantages across educational groups identified here could help to identify determining factors and the efficiency of national policies implemented to tackle...
Controlling Electricity Consumption by Forecasting its Response to Varying Prices
DEFF Research Database (Denmark)
Corradi, Olivier; Ochsenfeld, Henning Peter; Madsen, Henrik
2013-01-01
In a real-time electricity pricing context where consumers are sensitive to varying prices, having the ability to anticipate their response to a price change is valuable. This paper proposes models for the dynamics of such price-response, and shows how these dynamics can be used to control...... electricity consumption using a one-way price signal. Estimation of the price-response is based on data measurable at grid level, removing the need to install sensors and communication devices between each individual consumer and the price-generating entity. An application for price-responsive heating systems...... is studied based on real data, before conducting a control by price experiment using a mixture of real and synthetic data. With the control objective of following a constant consumption reference, peak heating consumption is reduced by nearly 5%, and 11% of the mean daily heating consumption is shifted....
Time-varying risk aversion. An application to energy hedging
Energy Technology Data Exchange (ETDEWEB)
Cotter, John [Centre for Financial Markets, School of Business, University College Dublin, Blackrock, Co. Dublin (Ireland); Hanly, Jim [School of Accounting and Finance, Dublin Institute of Technology, Dublin 2 (Ireland)
2010-03-15
Risk aversion is a key element of utility maximizing hedge strategies; however, it has typically been assigned an arbitrary value in the literature. This paper instead applies a GARCH-in-Mean (GARCH-M) model to estimate a time-varying measure of risk aversion that is based on the observed risk preferences of energy hedging market participants. The resulting estimates are applied to derive explicit risk aversion based optimal hedge strategies for both short and long hedgers. Out-of-sample results are also presented based on a unique approach that allows us to forecast risk aversion, thereby estimating hedge strategies that address the potential future needs of energy hedgers. We find that the risk aversion based hedges differ significantly from simpler OLS hedges. When implemented in-sample, risk aversion hedges for short hedgers outperform the OLS hedge ratio in a utility based comparison. (author)
Varied definitions of risk related to sensation seeking trait
Energy Technology Data Exchange (ETDEWEB)
Daastoel, P.Oe.U.; Drottz-Sjoeberg, B.M. [Norwegian Univ. of Science and Technology, Trondheim (Norway). Dept. of Psychology
1999-12-01
This pilot study is based on the assumption and the knowledge that previous results show that the normal use of the word risk varies across subjects. The risk definitions the subjects use have also been shown to be related to various educational interests. A related field of research has developed measures for Sensation Seeking personality trait, with four facets. Three independent groups of first year psychology students reported their normal definition of the word risk using one of three measurement formats. The results showed, e.g. that the typical open-ended response to the personal definition of risk was danger. Subjects who defined risk as the combination of probability and consequences tended to score higher on the total Sensation Seeking Scale, as compared to those defining risk as the probability of an event.
Optical waveguide device with an adiabatically-varying width
Energy Technology Data Exchange (ETDEWEB)
Watts,; Michael R. (Albuquerque, NM), Nielson; Gregory, N [Albuquerque, NM
2011-05-10
Optical waveguide devices are disclosed which utilize an optical waveguide having a waveguide bend therein with a width that varies adiabatically between a minimum value and a maximum value of the width. One or more connecting members can be attached to the waveguide bend near the maximum value of the width thereof to support the waveguide bend or to supply electrical power to an impurity-doped region located within the waveguide bend near the maximum value of the width. The impurity-doped region can form an electrical heater or a semiconductor junction which can be activated with a voltage to provide a variable optical path length in the optical waveguide. The optical waveguide devices can be used to form a tunable interferometer (e.g. a Mach-Zehnder interferometer) which can be used for optical modulation or switching. The optical waveguide devices can also be used to form an optical delay line.
Controlling the Quantum State with a time varying potential.
Carrasco, Sebastián; Rogan, José; Valdivia, Juan Alejandro
2017-10-16
The problem of controlling the quantum state of a system is investigated using a time varying potential. As a concrete example we study the problem of a particle in a box with a periodically oscillating infinite square-well potential, from which we obtain results that can be applied to systems with periodically oscillating boundary conditions. We derive an analytic expression for the frequencies of resonance between states, and against standard intuition, we show how to use this behavior to control the quantum state of the system at will. In particular, we offer as an example the transition from the ground state to the first excited state of the square well potential. At first sight, it may be counter intuitive that we can control the state of such a quantum Hamiltonian, as the Schrödinger equation conserves the norm of the wave function. In this manuscript, we show how that can be achieved.
Robust topology optimization accounting for spatially varying manufacturing errors
DEFF Research Database (Denmark)
Schevenels, M.; Lazarov, Boyan Stefanov; Sigmund, Ole
2011-01-01
This paper presents a robust approach for the design of macro-, micro-, or nano-structures by means of topology optimization, accounting for spatially varying manufacturing errors. The focus is on structures produced by milling or etching; in this case over- or under-etching may cause parts...... of the structure to become thinner or thicker than intended. This type of error is modeled by means of a projection technique: a density filter is applied, followed by a Heaviside projection, using a low projection threshold to simulate under-etching and a high projection threshold to simulate over......-etching. In order to simulate the spatial variation of the manufacturing error, the projection threshold is represented by a (non-Gaussian) random field. The random field is obtained as a memoryless transformation of an underlying Gaussian field, which is discretized by means of an EOLE expansion. The robust...
Premorbid IQ varies across different definitions of schizophrenia
DEFF Research Database (Denmark)
Urfer Parnas, Annick; Jansson, Lennart; Handest, Peter
2007-01-01
The nature of the association between IQ and schizophrenia is still unclear. So far no study addressed this issue in relation to the breadth or scope of the very concept of schizophrenia. We examined the premorbid IQ in a polydiagnostic study with four classifications of schizophrenia: ICD-8/9, ICD......-10, St. Louis and Flexible System-Wide. Only the ICD-10 schizophrenia patients exhibited a significantly lower premorbid IQ. There were suggestive differences between the four examined systems as well as between the ICD-10 paranoid and non-paranoid subtypes. Exploration of crucial diagnostic features...... of schizophrenia in relation to IQ revealed associations between low premorbid IQ and hallucinations as well as negative symptoms. It is concluded that premorbid IQ varies across different definitions of schizophrenia....
Epidemic spreading in time-varying community networks
Energy Technology Data Exchange (ETDEWEB)
Ren, Guangming, E-mail: wangxy@dlut.edu.cn, E-mail: ren-guang-ming@163.com [School of Electronic and Information, Guangdong Polytechnic Normal University, Guangzhou 510665 (China); Faculty of Electronic Information and Electrical Engineering, Dalian University of Technology, Dalian 116024 (China); Wang, Xingyuan, E-mail: wangxy@dlut.edu.cn, E-mail: ren-guang-ming@163.com [Faculty of Electronic Information and Electrical Engineering, Dalian University of Technology, Dalian 116024 (China)
2014-06-15
The spreading processes of many infectious diseases have comparable time scale as the network evolution. Here, we present a simple networks model with time-varying community structure, and investigate susceptible-infected-susceptible epidemic spreading processes in this model. By both theoretic analysis and numerical simulations, we show that the efficiency of epidemic spreading in this model depends intensively on the mobility rate q of the individuals among communities. We also find that there exists a mobility rate threshold q{sub c}. The epidemic will survive when q > q{sub c} and die when q < q{sub c}. These results can help understanding the impacts of human travel on the epidemic spreading in complex networks with community structure.
Model microswimmers in channels with varying cross section
Malgaretti, Paolo; Stark, Holger
2017-05-01
We study different types of microswimmers moving in channels with varying cross section and thereby interacting hydrodynamically with the channel walls. Starting from the Smoluchowski equation for a dilute suspension, for which interactions among swimmers can be neglected, we derive analytic expressions for the lateral probability distribution between plane channel walls. For weakly corrugated channels, we extend the Fick-Jacobs approach to microswimmers and thereby derive an effective equation for the probability distribution along the channel axis. Two regimes arise dominated either by entropic forces due to the geometrical confinement or by the active motion. In particular, our results show that the accumulation of microswimmers at channel walls is sensitive to both the underlying swimming mechanism and the geometry of the channels. Finally, for asymmetric channel corrugation, our model predicts a rectification of microswimmers along the channel, the strength and direction of which strongly depends on the swimmer type.
Bilateral Teleoperation in Cartesian Space with Time-Varying Delay
Directory of Open Access Journals (Sweden)
Zhang Chen
2012-10-01
Full Text Available The bilateral control of a teleoperator in Cartesian space with time-varying delay is studied in this paper. Compared with the traditional joint-space teleoperation mode, bilateral control in Cartesian space has advantages when dealing with the kinematically dissimilar (KDS teleoperation systems. A Cartesian space-based PD-like bilateral controller with dissipation factors is designed. Considering the fact that attitude errors derived by rotation matrix cannot be directly used for PD control, a quaternion-based approach is adopted to calculate the attitude errors in Cartesian space. In order to overcome the instability brought about by communication delay, local damping components are employed at both ends of the teleoperator system. The variation of time delay may generate extra energy and influence the stability of the system, thus dissipation factors are introduced into the controller. The stability of the proposed bilateral controller is proved and the simulations show the effectiveness of the approach.
Unified dark energy thermodynamics: varying w and the -1-crossing
Energy Technology Data Exchange (ETDEWEB)
Saridakis, Emmanuel N [Department of Physics, University of Athens, GR-15771 Athens (Greece); Gonzalez-Diaz, Pedro F [Colina de los Chopos, Instituto de Fisica Fundamental, Consejo Superior de Investigaciones Cientificas, Serrano 121, 28006 Madrid (Spain); Sigueenza, Carmen L [Estacion Ecologica de BiocosmologIa, Pedro de Alvarado 14, 06411 Medellin (Spain)
2009-08-21
We investigate, in a unified and general way, the thermodynamic properties of dark energy with an arbitrary, varying equation-of-state parameter w(a). We find that all quantities are well defined and regular for every w(a), including the -1-crossing, with the temperature being negative in the phantom regime (w(a) < -1) and positive in the quintessence one (w(a) > -1). The density and entropy are always positive while the chemical potential can be arbitrary. At the -1-crossing, both temperature and chemical potential are zero. The temperature negativity can only be interpreted in the quantum framework. The regular behavior of all quantities at the -1-crossing leads to the conclusion that such a crossing does not correspond to a phase transition, but rather to a smooth crossover.
Calving rates at tidewater glaciers vary strongly with ocean temperature.
Luckman, Adrian; Benn, Douglas I; Cottier, Finlo; Bevan, Suzanne; Nilsen, Frank; Inall, Mark
2015-10-09
Rates of ice mass loss at the calving margins of tidewater glaciers (frontal ablation rates) are a key uncertainty in sea level rise projections. Measurements are difficult because mass lost is replaced by ice flow at variable rates, and frontal ablation incorporates sub-aerial calving, and submarine melt and calving. Here we derive frontal ablation rates for three dynamically contrasting glaciers in Svalbard from an unusually dense series of satellite images. We combine ocean data, ice-front position and terminus velocity to investigate controls on frontal ablation. We find that frontal ablation is not dependent on ice dynamics, nor reduced by glacier surface freeze-up, but varies strongly with sub-surface water temperature. We conclude that calving proceeds by melt undercutting and ice-front collapse, a process that may dominate frontal ablation where submarine melt can outpace ice flow. Our findings illustrate the potential for deriving simple models of tidewater glacier response to oceanographic forcing.
Time-Varying Space-Only Codes for Coded MIMO
Duyck, Dieter; Takawira, Fambirai; Boutros, Joseph J; Moeneclaey, Marc
2012-01-01
Multiple antenna (MIMO) devices are widely used to increase reliability and information bit rate. Optimal error rate performance (full diversity and large coding gain), for unknown channel state information at the transmitter and for maximal rate, can be achieved by approximately universal space-time codes, but comes at a price of large detection complexity, infeasible for most practical systems. We propose a new coded modulation paradigm: error-correction outer code with space-only but time-varying precoder (as inner code). We refer to the latter as Ergodic Mutual Information (EMI) code. The EMI code achieves the maximal multiplexing gain and full diversity is proved in terms of the outage probability. Contrary to most of the literature, our work is not based on the elegant but difficult classical algebraic MIMO theory. Instead, the relation between MIMO and parallel channels is exploited. The theoretical proof of full diversity is corroborated by means of numerical simulations for many MIMO scenarios, in te...
Redshift drift in varying speed of light cosmology
Energy Technology Data Exchange (ETDEWEB)
Balcerzak, Adam, E-mail: abalcerz@wmf.univ.szczecin.pl [Institute of Physics, University of Szczecin, Wielkopolska 15, 70-451 Szczecin (Poland); Copernicus Center for Interdisciplinary Studies, Sławkowska 17, 31-016 Kraków (Poland); Dabrowski, Mariusz P., E-mail: mpdabfz@wmf.univ.szczecin.pl [Institute of Physics, University of Szczecin, Wielkopolska 15, 70-451 Szczecin (Poland); Copernicus Center for Interdisciplinary Studies, Sławkowska 17, 31-016 Kraków (Poland)
2014-01-20
We derive a redshift drift formula within the framework of varying speed of light (VSL) theory using the specific ansatz for the variability of c(t)=c{sub 0}a{sup n}(t). We show that negative values of the parameter n, which correspond to diminishing value of the speed of light during the evolution of the universe, effectively rescale dust matter to become little negative pressure matter, and the cosmological constant to became phantom. Positive values of n (growing c(t)) make VSL model to become more like Cold Dark Matter (CDM) model. Observationally, there is a distinction between the VSL model and the ΛCDM model for the admissible values of the parameter n∼−10{sup −5}, though it will be rather difficult to detect by planned extremely large telescopes (EELT, TMT, GMT) within their accuracy.
Network Coded Cooperation Over Time-Varying Channels
DEFF Research Database (Denmark)
Khamfroush, Hana; Lucani Rötter, Daniel Enrique; Barros, joao
2014-01-01
In this paper, we investigate the optimal design of cooperative network-coded strategies for a three-node wireless network with time-varying, half-duplex erasure channels. To this end, we formulate the problem of minimizing the total cost of transmitting M packets from source to two receivers...... that are suitable for practical systems. We use two wireless channel models to analyse the performance of the proposed heuristics in practical wireless networks, namely, (a) an infrastructure-to-vehicle (I2V) communication in a highway scenario considering Rayleigh fading, and (b) real packet loss measurements...... for WiFi using Aalborg University’s Raspberry Pi testbed. We compare our results with random linear network coding (RLNC) broadcasting schemes showing that our heuristics can provide up to 2x gains in completion time and up to 4x gains in terms of reliably serviced data packets....
Wildland-urban interface maps vary with purpose and context
Stewart, S.I.; Wilmer, B.; Hammer, R.B.; Aplet, G.H.; Hawbaker, T.J.; Miller, C.; Radeloff, V.C.
2009-01-01
Maps of the wildland-urban interface (WUI) are both policy tools and powerful visual images. Although the growing number of WUI maps serve similar purposes, this article indicates that WUI maps derived from the same data sets can differ in important ways related to their original intended application. We discuss the use of ancillary data in modifying census data to improve WUI maps and offer a cautionary note about this practice. A comparison of two WUI mapping approaches suggests that no single map is "best" because users' needs vary. The analysts who create maps are responsible for ensuring that users understand their purpose, data, and methods; map users are responsible for paying attention to these features and using each map accordingly. These considerations should apply to any analysis but are especially important to analyses of the WUI on which policy decisions will be made.
Chronic arsenicosis with varied pulmonary involvement – A case series
Directory of Open Access Journals (Sweden)
Agnik Pal
2015-01-01
Full Text Available Arsenic is an element which occurs naturally in the earth’s crust and in small quantities in rock, soil, water and air. Chronic arsenic toxicity produces various dermal and systemic manifestations including cancer. It may also cause different pulmonary diseases. Here, we have described a case series of three chronic arsenicosis patients having varied pulmonary involvements ranging from bronchiectasis to chronic obstructive pulmonary diseases. They all had classic raindrop pigmentations with one patient developing squamous cell carcinoma. Pulmonary manifestations were severe with more cutaneous manifestations as well as more arsenic levels in hair and nail samples of patients. Manifestations also seemed severe with increased duration of exposure and more amount of arsenic in their drinking water.
Factors influencing eating a varied diet in old age
DEFF Research Database (Denmark)
Dean, Moira; Raats, Monique M.; Grunert, Klaus G.
2009-01-01
Objective: To investigate the influences of resources and food-related goals on the variety of food choice among older people. Design: A questionnaire-based survey in eight European countries: Poland, Portugal, United Kingdom, Germany, Sweden, Denmark, Italy and Spain. Subjects: Participants (n...... levels. Food-related goals contributed to variety of food intake that was not accounted for by the amount of material resources possessed or the social and other resources perceived to be possessed. Conclusions: Older people's variety of food intake depended on material resources (e.g. monthly income...... kitchen facilities, access to good service providers and support from friends and neighbours, all contributed to how varied a diet they ate....
Time-varying Capital Requirements and Disclosure Rules
DEFF Research Database (Denmark)
Kragh, Jonas; Rangvid, Jesper
Unique and confidential Danish data allow us to identify how changes in disclosure requirements and bank-specific time-varying capital requirements affect banks' lending and capital accumu-lation decisions. We find that banks increase their capital ratios after capital requirements are increased......, implying that resilience in the banking system is also increased. The increase in capital ratios is partly due to a modest reduction in lending. Using a policy changes, we show that banks react stronger to changes in capital requirements when these are public. Our results further suggest that the impact...... of capital requirements differ for small and large banks. Large banks raise their capital ratios more, reduce lending less, and accumulate more new capital compared to small banks....
Integrodifference models for persistence in temporally varying river environments.
Jacobsen, Jon; Jin, Yu; Lewis, Mark A
2015-02-01
To fully understand population persistence in river ecosystems, it is necessary to consider the effect of the water flow, which varies tremendously with seasonal fluctuations of water runoff and snow melt. In this paper, we study integrodifference models for growth and dispersal in the presence of advective flow with both periodic (alternating) and random kernel parameters. For the alternating kernel model, we obtain the principal eigenvalue of the linearization operator to determine population persistence and derive a boundary value problem to calculate it. For the random model, we establish two persistence metrics: a generalized spectral radius and the asymptotic growth rate, which are mathematically equivalent but can be understood differently, to determine population persistence or extinction. The theoretical framework and methods for calculations are provided, and the framework is applied to calculating persistence in highly variable river environments.
A Diagnostic System for Speed-Varying Motor Rotary Faults
Directory of Open Access Journals (Sweden)
Chwan-Lu Tseng
2014-01-01
Full Text Available This study proposed an intelligent rotary fault diagnostic system for motors. A sensorless rotational speed detection method and an improved dynamic structural neural network are used. Moreover, to increase the convergence speed of training, a terminal attractor method and a hybrid discriminant analysis are also adopted. The proposed method can be employed to detect the rotary frequencies of motors with varying speeds and can enhance the discrimination of motor faults. To conduct the experiments, this study used wireless sensor nodes to transmit vibration data and employed MATLAB to write codes for functional modules, including the signal processing, sensorless rotational speed estimation, neural network, and stochastic process control chart. Additionally, Visual Basic software was used to create an integrated human-machine interface. The experimental results regarding the test of equipment faults indicated that the proposed novel diagnostic system can effectively estimate rotational speeds and provide superior ability of motor fault discrimination with fast training convergence.
Time-varying magnetic fields: effect on DNA synthesis.
Liboff, A R; Williams, T; Strong, D M; Wistar, R
1984-02-24
Human fibroblasts have exhibited enhanced DNA synthesis when exposed to sinusoidally varying magnetic fields for a wide range of frequencies (15 hertz to 4 kilohertz) and amplitudes (2.3 X 10(-6) to 5.6 X 10(-4) tesla). This effect, which is at maximum during the middle of the S phase of the cell cycle, appears to be independent of the time derivative of the magnetic field, suggesting an underlying mechanism other than Faraday's law. The threshold is estimated to be between 0.5 X 10(-5) and 2.5 X 10(-5) tesla per second. These results bring into question the allegedly specific magnetic wave shapes now used in therapeutic devices for bone nonunion. The range of magnetic field amplitudes tested encompass the geomagnetic field, suggesting the possibility of mutagenic interactions directly arising from short-term changes in the earth's field.
SPECTRAL IMAGING FROM UAVS UNDER VARYING ILLUMINATION CONDITIONS
Directory of Open Access Journals (Sweden)
T. Hakala
2013-08-01
Full Text Available Rapidly developing unmanned aerial vehicles (UAV have provided the remote sensing community with a new rapidly deployable tool for small area monitoring. The progress of small payload UAVs has introduced greater demand for light weight aerial payloads. For applications requiring aerial images, a simple consumer camera provides acceptable data. For applications requiring more detailed spectral information about the surface, a new Fabry-Perot interferometer based spectral imaging technology has been developed. This new technology produces tens of successive images of the scene at different wavelength bands in very short time. These images can be assembled in spectral data cubes with stereoscopic overlaps. On field the weather conditions vary and the UAV operator often has to decide between flight in sub optimal conditions and no flight. Our objective was to investigate methods for quantitative radiometric processing of images taken under varying illumination conditions, thus expanding the range of weather conditions during which successful imaging flights can be made. A new method that is based on insitu measurement of irradiance either in UAV platform or in ground was developed. We tested the methods in a precision agriculture application using realistic data collected in difficult illumination conditions. Internal homogeneity of the original image data (average coefficient of variation in overlapping images was 0.14–0.18. In the corrected data, the homogeneity was 0.10–0.12 with a correction based on broadband irradiance measured in UAV, 0.07–0.09 with a correction based on spectral irradiance measurement on ground, and 0.05–0.08 with a radiometric block adjustment based on image data. Our results were very promising, indicating that quantitative UAV based remote sensing could be operational in diverse conditions, which is prerequisite for many environmental remote sensing applications.
Social structure varies with elevation in an Alpine ant.
Purcell, Jessica; Pellissier, Loïc; Chapuisat, Michel
2015-01-01
Insect societies vary greatly in social organization, yet the relative roles of ecological and genetic factors in driving this variation remain poorly understood. Identifying how social structure varies along environmental gradients can provide insights into the ecological conditions favouring alternative social organizations. Here, we investigate how queen number variation is distributed along elevation gradients within a socially polymorphic ant, the Alpine silver ant Formica selysi. We sampled low- and high-elevation populations in multiple Alpine valleys. We show that populations belonging to different drainage basins are genetically differentiated. In contrast, there is little genetic divergence between low- and high-elevation populations within the same drainage basin. Thus, elevation gradients in each of the drainage basins represent independent contrasts. Whatever the elevation, all well-sampled populations are socially polymorphic, containing both monogynous (= one queen) and polygynous (= multiple queen) colonies. However, the proportion of monogynous colonies per population increases at higher elevation, while the effective number of queens in polygynous colonies decreases, and this pattern is replicated in each drainage basin. The increased prevalence of colonies with a single queen at high elevation is correlated with summer and winter average temperature, but not with precipitation. The colder, unpredictable and patchy environment encountered at higher elevations may favour larger queens with the ability to disperse and establish incipient monogynous colonies independently, while the stable and continuous habitat in the lowlands may favour large, fast-growing polygynous colonies. By highlighting differences in the environmental conditions favouring monogynous or polygynous colonies, this study sheds light on the ecological factors influencing the distribution and maintenance of social polymorphism. © 2014 John Wiley & Sons Ltd.
Mixed lipid bilayers with locally varying spontaneous curvature and bending.
Gueguen, Guillaume; Destainville, Nicolas; Manghi, Manoel
2014-08-01
A model of lipid bilayers made of a mixture of two lipids with different average compositions on both leaflets, is developed. A Landau Hamiltonian describing the lipid-lipid interactions on each leaflet, with two lipidic fields ψ 1 and ψ 2, is coupled to a Helfrich one, accounting for the membrane elasticity, via both a local spontaneous curvature, which varies as C 0 + C 1(ψ 1 - ψ 2/2), and a bending modulus equal to κ 0 + κ 1(ψ 1 + ψ 2)/2. This model allows us to define curved patches as membrane domains where the asymmetry in composition, ψ 1 - ψ 2, is large, and thick and stiff patches where ψ 1 + ψ 2 is large. These thick patches are good candidates for being lipidic rafts, as observed in cell membranes, which are composed primarily of saturated lipids forming a liquid-ordered domain and are known to be thick and flat nano-domains. The lipid-lipid structure factors and correlation functions are computed for globally spherical membranes and planar ones and for a whole set of parameters including the surface tension and the coupling in the two leaflet compositions. Phase diagrams are established, within a Gaussian approximation, showing the occurrence of two types of Structure Disordered phases, with correlations between either curved or thick patches, and an Ordered phase, corresponding to the divergence of the structure factor at a finite wave vector. The varying bending modulus plays a central role for curved membranes, where the driving force κ 1 C 0 (2) is balanced by the line tension, to form raft domains of size ranging from 10 to 100 nm. For planar membranes, raft domains emerge via the cross-correlation with curved domains. A global picture emerges from curvature-induced mechanisms, described in the literature for planar membranes, to coupled curvature- and bending-induced mechanisms in curved membranes forming a closed vesicle.
Slowly Varying Dilaton Cosmologies and Their Field Theory Duals
Energy Technology Data Exchange (ETDEWEB)
Awad, Adel; /British U. in Egypt /Ain Shams U., Cairo; Das, Sumit R.; Ghosh, Archisman; Oh, Jae-Hyuk; /Kentucky U.; Trivedi, Sandip P.; /Tata Inst. /Stanford U., ITP /SLAC
2011-06-28
We consider a deformation of the AdS{sub 5} x S{sup 5} solution of IIB supergravity obtained by taking the boundary value of the dilaton to be time dependent. The time dependence is taken to be slowly varying on the AdS scale thereby introducing a small parameter {epsilon}. The boundary dilaton has a profile which asymptotes to a constant in the far past and future and attains a minimum value at intermediate times. We construct the sugra solution to first non-trivial order in {epsilon}, and find that it is smooth, horizon free, and asymptotically AdS{sub 5} x S{sup 5} in the far future. When the intermediate values of the dilaton becomes small enough the curvature becomes of order the string scale and the sugra approximation breaks down. The resulting dynamics is analysed in the dual SU(N) gauge theory on S{sup 3} with a time dependent coupling constant which varies slowly. When N{epsilon} << 1, we find that a quantum adiabatic approximation is applicable, and use it to argue that at late times the geometry becomes smooth AdS{sub 5} x S{sup 5} again. When N{epsilon} >> 1, we formulate a classical adiabatic perturbation theory based on coherent states which arises in the large N limit. For large values of the tHooft coupling this reproduces the supergravity results. For small 'tHooft coupling the coherent state calculations become involved and we cannot reach a definite conclusion. We argue that the final state should have a dual description which is mostly smooth AdS5 space with the possible presence of a small black hole.
Gut microbiomes of Indian children of varying nutritional status.
Directory of Open Access Journals (Sweden)
Tarini Shankar Ghosh
Full Text Available BACKGROUND: Malnutrition is a global health problem affecting more than 300 million pre-school children worldwide. It is one of the major health concerns in India since around 50% of children below the age of two suffer from various forms of malnutrition. The gut microbiome plays an important role in nutrient pre-processing, assimilation and energy harvest from food. Consequently, dysbiosis of the gut microbiota has been implicated in malnutrition. METHODOLOGY/PRINCIPAL FINDINGS: Metagenomics approach was adopted to investigate the gut microbiome sampled from 20 rural Indian children with varying nutritional status. The changes in the abundances of various taxonomic and functional groups were investigated across these gut microbiomes. A core set of 23 genera were observed across samples, with some showing differential abundances with varying nutritional status. One of the findings of the current study is the positive/negative associations of specific taxonomic and functional groups with the nutritional status of the children. Notable alterations in the architecture of the inter-microbial co-occurrence networks were also observed with changes in nutritional status. A key example is the clustering of potentially pathogenic groups into a distinct hub in severely malnourished gut. Our data does not demonstrate causality with the microbiome patterns that we observed, rather a description of some interesting patterns, whose underlying mechanism remains to be uncovered. CONCLUSIONS: The present study envisioned interrelationships between the pattern of gut microbiome and the nutritional status of children. The cause of this pattern needs to be explored. However, insights obtained from the present study form the basis for further metagenomic investigations on larger population of children. Results of such studies will be useful in identifying the key microbial groups that can be utilized for targeted therapeutic interventions for managing severe acute
Ice sheet growth with laterally varying bedrock relaxation time
van der Wal, Wouter; Vizcaino Rubio, Pablo; De Boer, Bas; van de Wal, Roderik
2017-04-01
Isostatic response of the bedrock, or glacial isostatic adjustment (GIA) in included in most ice sheet models. This is important because the surface elevation determines the mass balance and thereby implicitly also the strength of the mass balance feedback where higher surface elevation yields lower temperatures implying less melt and vice versa. Usually a single relaxation time or a set of relaxation times is used to model the response everywhere on Earth or at least for an entire ice sheet. In reality the viscosity in the Earth's mantle, and hence the relaxation time experienced by the ice, varies with location. Seismic studies indicate that several regions that were covered by ice during the last glacial cycle are underlain by mantle in which viscosity varies with orders of magnitude, such as Antarctica and North America. The question is whether such a variation of viscosity influences ice evolution. Several GIA models exist that can deal with 3D viscosity, but their large computation times make it nearly impossible to couple them to ice sheet models. Here we use the ANICE ice-sheet model (de Boer et al. 2013) with a simple bedrock-relaxation model in which a different relaxation time is used for separate regions. A temperature anomaly is applied to grow a schematic ice sheet on a flat earth, with other forcing mechanisms neglected. It is shown that in locations with a fast relaxation time of 300 years the equilibrium ice sheet is significantly thinner and narrower but also ice thickness in neighbouring regions (with the more standard relaxation time of 3000 years) is affected.
Hydrodynamic simulations of accretion flows with time-varying viscosity
Roy, Abhishek; Chakrabarti, Sandip K.
2017-12-01
X-ray outbursts of stellar-mass black hole candidates are believed to be due to a sudden rise in viscosity, which transports angular momentum efficiently and increases the accretion rates, causing higher X-ray flux. After the viscosity is reduced, the outburst subsides and the object returns back to the pre-outburst quiescence stage. In the absence of a satisfactory understanding of the physical mechanism leading to such a sharp time dependence of viscous processes, we perform numerical simulations where we include the rise and fall of a viscosity parameter at an outer injection grid, assumed to be located at the accumulation radius where matter from the companion is piled up before being released by enhanced viscosity. We use a power-law radial dependence of the viscosity parameter (α ˜ rɛ), but the exponent (ɛ) is allowed to vary with time to mimic a fast rise and decay of the viscosity parameter. Since X-ray spectra of a black hole candidate can be explained by a Keplerian disc component in the presence of a post-shock region of an advective flow, our goal here is also to understand whether the flow configurations required to explain the spectral states of an outbursting source could be obtained by a time-varying viscosity. We present the results of our simulations to prove that low-angular-momentum (sub-Keplerian) advective flows do form a Keplerian disc in the pre-shock region when the viscosity is enhanced, which disappears on a much longer time-scale after the viscosity is withdrawn. From the variation of the Keplerian disc inside an advective halo, we believe that our result, for the first time, is able to simulate the two-component advective flow dynamics during an entire X-ray outburst and explain the observed hysteresis effects in the hardness-intensity diagram.
Gut microbiomes of Indian children of varying nutritional status.
Ghosh, Tarini Shankar; Gupta, Sourav Sen; Bhattacharya, Tanudeep; Yadav, Deepak; Barik, Anamitra; Chowdhury, Abhijit; Das, Bhabatosh; Mande, Sharmila S; Nair, G Balakrish
2014-01-01
Malnutrition is a global health problem affecting more than 300 million pre-school children worldwide. It is one of the major health concerns in India since around 50% of children below the age of two suffer from various forms of malnutrition. The gut microbiome plays an important role in nutrient pre-processing, assimilation and energy harvest from food. Consequently, dysbiosis of the gut microbiota has been implicated in malnutrition. Metagenomics approach was adopted to investigate the gut microbiome sampled from 20 rural Indian children with varying nutritional status. The changes in the abundances of various taxonomic and functional groups were investigated across these gut microbiomes. A core set of 23 genera were observed across samples, with some showing differential abundances with varying nutritional status. One of the findings of the current study is the positive/negative associations of specific taxonomic and functional groups with the nutritional status of the children. Notable alterations in the architecture of the inter-microbial co-occurrence networks were also observed with changes in nutritional status. A key example is the clustering of potentially pathogenic groups into a distinct hub in severely malnourished gut. Our data does not demonstrate causality with the microbiome patterns that we observed, rather a description of some interesting patterns, whose underlying mechanism remains to be uncovered. The present study envisioned interrelationships between the pattern of gut microbiome and the nutritional status of children. The cause of this pattern needs to be explored. However, insights obtained from the present study form the basis for further metagenomic investigations on larger population of children. Results of such studies will be useful in identifying the key microbial groups that can be utilized for targeted therapeutic interventions for managing severe acute malnutrition.
Spall behavior of cast iron with varying microstructures
Plume, Gifford; Rousseau, Carl-Ernst
2014-07-01
The spall strength of cast iron with varying microstructures has been investigated using plate impact at moderate speed. Stress history measurements were made with manganin stress gauges embedded between the back face of the specimen and a low impedance polycarbonate backing. Five separate cast irons were tested. Four of these consisted of gray cast iron with graphite in flake form, with three classified as Type VII A2 and the fourth containing a bimodal distribution of Types VII A4 and VII D8. The fifth casting consisted of ductile cast iron with graphite in nodular form, classified as Type I, size class 5. The spall strength for the Type VII A2 gray cast irons varied between 40 and 370 MPa, and that of the additional gray cast iron, between 410 and 490 MPa. The spall strength of the ductile cast iron fell within the range of 0.94-1.2 GPa. It is shown that the spall strength is linked to the damage level at the spall plane, where an increased level of tensile stress is required to generate higher levels of damage. Post mortem analysis was performed on the recovered samples, revealing the graphite phase to be the primary factor governing the spall fracture of cast irons, where crack nucleation is directly correlated to the debonding of graphite from the metal matrix. The average length of graphite found within a casting is linked to the material's strength, where strength increases as a function of decreasing length. The morphology and mean free path of graphite precipitates further govern the subsequent coalescence of initiated cracks to form a complete fracture plane. In cases where graphite spacing is large, increased energy level is required to complete the fracture process. A secondary factor governing the spall fracture of cast irons has also been linked to the microstructure of the metal matrix, with pearlite yielding higher spall strengths than free ferrite.
Circular motion analysis of time-varying bioimpedance.
Sanchez, B; Louarroudi, E; Rutkove, S B; Pintelon, R
2015-11-01
This paper presents a step forward towards the analysis of a linear periodically time-varying (PTV) bioimpedance ZPTV(jw, t), which is an important subclass of a linear time-varying (LTV) bioimpedance. Similarly to the Fourier coefficients of a periodic signal, a PTV impedance can be decomposed into frequency dependent impedance phasors, [Formula: see text], that are rotating with an angular speed of wr = 2πr/TZ. The vector length of these impedance phasors corresponds to the amplitude of the rth-order harmonic impedance |Zr( jw)| and the initial phase is given by Φr(w, t0) = [Symbol: see text]Zr( jw) + 2πrt0/TZ, with t0∈[0, T] being a time instant within the measurement time T. The impedance period TZ stands for the cycle length of the bio-system under investigation; for example, the elapsed time between two consecutive R-waves in the electrocardiogram or the breathing periodicity in case of the heart or lungs, respectively. First, it is demonstrated that the harmonic impedance phasor [Formula: see text], at a particular measured frequency k, can be represented by a rotating phasor, leading to the so-called circular motion analysis technique. Next, the two dimensional (2D) representation of the harmonic impedance phasors is then extended to a three-dimensional (3D) coordinate system by taking into account the frequency dependence. Finally, we introduce a new visualizing tool to summarize the frequency response behavior of ZPTV( jw, t) into a single 3D plot using the local Frenet-Serret frame. This novel 3D impedance representation is then compared with the 3D Nyquist representation of a PTV impedance. The concepts are illustrated through real measurements conducted on a PTV RC-circuit.
Time-varying trends of global vegetation activity
Pan, N.; Feng, X.; Fu, B.
2016-12-01
Vegetation plays an important role in regulating the energy change, water cycle and biochemical cycle in terrestrial ecosystems. Monitoring the dynamics of vegetation activity and understanding their driving factors have been an important issue in global change research. Normalized Difference Vegetation Index (NDVI), an indicator of vegetation activity, has been widely used in investigating vegetation changes at regional and global scales. Most studies utilized linear regression or piecewise linear regression approaches to obtain an averaged changing rate over a certain time span, with an implicit assumption that the trend didn't change over time during that period. However, no evidence shows that this assumption is right for the non-linear and non-stationary NDVI time series. In this study, we adopted the multidimensional ensemble empirical mode decomposition (MEEMD) method to extract the time-varying trends of NDVI from original signals without any a priori assumption of their functional form. Our results show that vegetation trends are spatially and temporally non-uniform during 1982-2013. Most vegetated area exhibited greening trends in the 1980s. Nevertheless, the area with greening trends decreased over time since the early 1990s, and the greening trends have stalled or even reversed in many places. Regions with browning trends were mainly located in southern low latitudes in the 1980s, whose area decreased before the middle 1990s and then increased at an accelerated rate. The greening-to-browning reversals were widespread across all continents except Oceania (43% of the vegetated areas), most of which happened after the middle 1990s. In contrast, the browning-to-greening reversals occurred in smaller area and earlier time. The area with monotonic greening and browning trends accounted for 33% and 5% of the vegetated area, respectively. By performing partial correlation analyses between NDVI and climatic elements (temperature, precipitation and cloud cover
Innovation diffusion on time-varying activity driven networks
Rizzo, Alessandro; Porfiri, Maurizio
2016-01-01
Since its introduction in the 1960s, the theory of innovation diffusion has contributed to the advancement of several research fields, such as marketing management and consumer behavior. The 1969 seminal paper by Bass [F.M. Bass, Manag. Sci. 15, 215 (1969)] introduced a model of product growth for consumer durables, which has been extensively used to predict innovation diffusion across a range of applications. Here, we propose a novel approach to study innovation diffusion, where interactions among individuals are mediated by the dynamics of a time-varying network. Our approach is based on the Bass' model, and overcomes key limitations of previous studies, which assumed timescale separation between the individual dynamics and the evolution of the connectivity patterns. Thus, we do not hypothesize homogeneous mixing among individuals or the existence of a fixed interaction network. We formulate our approach in the framework of activity driven networks to enable the analysis of the concurrent evolution of the interaction and individual dynamics. Numerical simulations offer a systematic analysis of the model behavior and highlight the role of individual activity on market penetration when targeted advertisement campaigns are designed, or a competition between two different products takes place.
Ultrasonic Adaptive Detection for Aerospace Components with Varying Thickness
Directory of Open Access Journals (Sweden)
Zhen Xiao
2017-01-01
Full Text Available Automatic inspection of microdefects located in the aerospace components is difficult due to the imprecise scanning trajectory, especially for those specimens with varying thickness. In this paper, a new ultrasonic nondestructive testing (NDT system using the robotic scanning trajectory is constructed for inspecting turbine blades. Additionally, an approach based on the analysis of ultrasonic signals is proposed to calibrate the trajectory; the ultrasonic image based on the threshold function represents the distribution of inner defects when the following gate is used to track the flaw echo. Therefore, the characteristic parameters of the flaw echo signals are easy to be discriminated if the reflection waves are stable in the time domain. Experimental result verified the effective and feasibility of the proposed approach; the distribution of inner defects can be shown with a higher resolution than other NDT methods when robotic orientation is correct at each point of scanning trajectory. Furthermore, the feature signals can be tracked more accurately during the ultrasonic signal processing if the ultrasonic distance was considered as a calibration coefficient of positional matrix. The proposed ultrasonic adaptive detection is adapted to complex geometric structure with a minimum resolution of equivalent diameter of the inner flaw being 0.15 millimeters.
Backbone Hydrogen Bond Strengths Can Vary Widely in Transmembrane Helices.
Cao, Zheng; Hutchison, James M; Sanders, Charles R; Bowie, James U
2017-08-09
Although backbone hydrogen bonds in transmembrane (TM) helices have the potential to be very strong due to the low dielectric and low water environment of the membrane, their strength has never been assessed experimentally. Moreover, variations in hydrogen bond strength might be necessary to facilitate the TM helix breaking and bending that is often needed to satisfy functional imperatives. Here we employed equilibrium hydrogen/deuterium fractionation factors to measure backbone hydrogen bond strengths in the TM helix of the amyloid precursor protein (APP). We find an enormous range of hydrogen bond free energies, with some weaker than water-water hydrogen bonds and some over 6 kcal/mol stronger than water-water hydrogen bonds. We find that weak hydrogen bonds are at or near preferred γ-secretase cleavage sites, suggesting that the sequence of APP and possibly other cleaved TM helices may be designed, in part, to make their backbones accessible for cleavage. The finding that hydrogen bond strengths in a TM helix can vary widely has implications for membrane protein function, dynamics, evolution, and design.
Ensilage performance of sorghum hybrids varying in extractable sugars
Energy Technology Data Exchange (ETDEWEB)
Philipp, Dirk; Moore, Kenneth J. [Iowa State University, Ames (United States); Pedersen, Jeffrey F.; Mitchell, Robert B. [University of Nebraska, Lincoln, NE (United States). USDA-ARS, Department of Agronomy; Grant, Richard J. [William H. Miner Agricultural Research Institute, Chazy, NY (United States); Redfearn, Daren D. [Oklahoma State University, Stillwater, OK (United States). Department of Plant and Soil Sciences
2007-07-15
Renewable feedstock resources require novel storage technologies to optimize industrial use. Solid state fermentation of biomass feedstock may provide organic chemicals and fibers while reducing the risk of current dry-storage procedures. Here, we compare the chemical composition and fermentation of six sorghum hybrids (Sorghum bicolor L. Moench) following 1, 7, and 21 days of storage. Ensilage of 7 days resulted in a pH of 3.8 and declined further to 3.75 at day 21. Lactate increased during ensilage from 2.0 to 3.9 g 100 g{sup -1}. Acetic acid increased between 1 and 7 days of ensiling but did not change until the end of the ensiling period. Total organic acids averaged 2.5 g 100 g{sup -1} after day 1 and increased to 4.2 and 4.7 g '100 g{sup -1} after days 7 and 21, respectively. Neutral detergent fiber ranged from 38 to 50 g 100 g{sup -1} among hybrids and total non-structural carbohydrates varied from 18 to 32 g 100 g{sup -1}. Hemicellulose and cellulose ranged from 13 to 19 g 100 g{sup -1} and 20 and 28 g 100 g{sup -1}, respectively. Genotypic variation in sorghum may offer designing dual-purpose hybrids for production of biomass and economically valuable byproducts. (author)
Statistical Hierarchy of Varying Speed of Light Cosmologies
Salzano, Vincenzo; Da¸browski, Mariusz P.
2017-12-01
Many varying speed of light (VSL) theories have been developed recently. Here we address the issue of their observational verification in a fully comprehensive way. By using the most updated cosmological probes, we test three different candidates for a VSL theory (Barrow & Magueijo, Avelino & Martins, and Moffat). We consider many different Ansätze for both the functional form of c(z) and the dark energy dynamics. We compare these results using a reliable statistical tool such as the Bayesian evidence. We find that the present cosmological data are perfectly compatible with any of these VSL scenarios, but for the Moffat model there is a higher Bayesian evidence ratio in favor of VSL rather than the c = constant ΛCDM scenario. Moreover, in such a scenario, the VSL signal can help to strengthen constraints on the spatial curvature (with indication toward an open universe), to clarify some properties of dark energy (exclusion of a cosmological constant at 2σ level), and is also falsifiable in the near future owing to peculiar issues that differentiate this model from the standard one. Finally, we apply an information prior and entropy prior in order to put physical constraints on the models, though still in favor Moffat’s proposal.
Instability of low viscosity elliptic jets with varying aspect ratio
Kulkarni, Varun
2011-11-01
In this work an analytical description of capillary instability of liquid elliptic jets with varying aspect ratio is presented. Linear stability analysis in the long wave approximation with negligible gravitational effects is employed. Elliptic cylindrical coordinate system is used and perturbation velocity potential substituted in the Laplace equation to yield Mathieu and Modified Mathieu differential equations. The dispersion relation for elliptical orifices of any aspect ratio is derived and validated for axisymmetric disturbances with m = 0, in the limit of aspect ratio, μ = 1 , i.e. the case of a circular jet. As Mathieu functions and Modified Mathieu function solutions converge to Bessel's functions in this limit the Rayleigh-Plateau instability criterion is met. Also, stability of solutions corresponding to asymmetric disturbances for the kink mode, m = 1 and flute modes corresponding to m >= 2 is discussed. Experimental data from earlier works is used to compare observations made for elliptical orifices with μ ≠ 1 . This novel approach aims at generalizing the results pertaining to cylindrical jets with circular cross section leading to better understanding of breakup in liquid jets of various geometries.
Sighting ocular dominance magnitude varies with test distance.
Ho, Raymond; Thompson, Benjamin; Babu, Raiju J; Dalton, Kristine
2017-10-31
Ocular dominance can be defined as the preference of an individual for viewing with one eye over the other for particular visual tasks. It is relevant to monovision contact lens wear, cataract surgery and sports vision. Clinically, the measurement of ocular dominance is typically done at an arbitrary distance using a sighting test, such as the hole-in-card method that has a binary outcome. We investigated the effect of test distance on ocular dominance measured using a binocular sighting test that provided a continuous measurement of dominance. Ten participants with normal binocular vision took part in this study. Their binocular sighting ocular dominance and phorias were measured at one, two, four, eight and 10 metres. During the dominance tests participants made a binocular alignment judgment and then were asked to indicate the relative alignment of each eye using a visual analogue scale as a reference. Eight participants had strong ocular dominance (five right, three left). For these participants, there was a significant increase in the magnitude of dominance with increasing test distance (p 0.05), despite changes in convergence demand. When ocular dominance is present, its magnitude varies significantly with test distance. This has significant implications for the accurate measurement of ocular dominance in the clinic and may reflect the neural processes that influence eye preference. © 2017 Optometry Australia.
Imprints of Dynamically Varying Vegetation on Simulated Climate
Koster, R. D.; Walker, G.
2013-12-01
The interaction of soil moisture with the atmosphere has been known for decades to influence the climate simulated with Earth system models, 'reddening', for example, the spectra of simulated air temperature. A land surface model fitted with dynamic vegetation phenology (the 'Catchment-CN' model) allows for similar examinations of phenology impacts on simulated climate. Here we examine the climate variability inherent in three parallel multi-decadal simulations with the NASA/GMAO GEOS-5 atmosphere/land modeling system: (i) a simulation with phenological variations (LAI) set to climatological seasonal cycles, as determined from an offline simulation with the Catchment-CN model driven with observations-based meteorological forcing; (ii) a simulation with interannually-varying (but prescribed) phenological variations, as again determined from the offline simulation; and (iii) a simulation with fully interactive vegetation phenology. The spectral characters of temperature and precipitation generated in these simulations are quantified and compared. Comparison of the first and third simulations in particular indicate the 'memory' imparted to the climate system through memory in phenology.
Opinion formation with time-varying bounded confidence.
Zhang, YunHong; Liu, QiPeng; Zhang, SiYing
2017-01-01
When individuals in social groups communicate with one another and are under the influence of neighbors' opinions, they typically revise their own opinions to adapt to such peer opinions. The individual threshold of bounded confidence will thus be affected by both a change in individual confidence and by neighbor influence. Individuals thus update their own opinions with new bounded confidence, while their updated opinions also influence their neighbors' opinions. Based on this reasoned factual assumption, we propose an opinion dynamics model with time-varying bounded confidence. A directed network is formed by the rule of the individual bounded confidence threshold. The threshold of individual bounded confidence involves both confidence variation and the in/out degree of the individual node. When the confidence variation is greater, an individual's confidence in persisting in his own opinion in interactions is weaker, and the individual is more likely to adopt neighbors' opinions. In networks, the in/out degree is determined by individual neighbors. Our main research involves the process of opinion evolution and the basic laws of opinion cluster formation. Group opinions converge exponentially to consensus with stable neighbors. An individual opinion evolution is determined by the average neighbor opinion effect strength. We also explore the conditions involved in forming a stable neighbor relationship and the influence of the confidence variation in the convergence of the threshold of bounded confidence. The results show that the influence on opinion evolution is greater with increased confidence variation.
Complexity Variability Assessment of Nonlinear Time-Varying Cardiovascular Control
Valenza, Gaetano; Citi, Luca; Garcia, Ronald G.; Taylor, Jessica Noggle; Toschi, Nicola; Barbieri, Riccardo
2017-02-01
The application of complex systems theory to physiology and medicine has provided meaningful information about the nonlinear aspects underlying the dynamics of a wide range of biological processes and their disease-related aberrations. However, no studies have investigated whether meaningful information can be extracted by quantifying second-order moments of time-varying cardiovascular complexity. To this extent, we introduce a novel mathematical framework termed complexity variability, in which the variance of instantaneous Lyapunov spectra estimated over time serves as a reference quantifier. We apply the proposed methodology to four exemplary studies involving disorders which stem from cardiology, neurology and psychiatry: Congestive Heart Failure (CHF), Major Depression Disorder (MDD), Parkinson’s Disease (PD), and Post-Traumatic Stress Disorder (PTSD) patients with insomnia under a yoga training regime. We show that complexity assessments derived from simple time-averaging are not able to discern pathology-related changes in autonomic control, and we demonstrate that between-group differences in measures of complexity variability are consistent across pathologies. Pathological states such as CHF, MDD, and PD are associated with an increased complexity variability when compared to healthy controls, whereas wellbeing derived from yoga in PTSD is associated with lower time-variance of complexity.
Varying face occlusion detection and iterative recovery for face recognition
Wang, Meng; Hu, Zhengping; Sun, Zhe; Zhao, Shuhuan; Sun, Mei
2017-05-01
In most sparse representation methods for face recognition (FR), occlusion problems were usually solved via removing the occlusion part of both query samples and training samples to perform the recognition process. This practice ignores the global feature of facial image and may lead to unsatisfactory results due to the limitation of local features. Considering the aforementioned drawback, we propose a method called varying occlusion detection and iterative recovery for FR. The main contributions of our method are as follows: (1) to detect an accurate occlusion area of facial images, an image processing and intersection-based clustering combination method is used for occlusion FR; (2) according to an accurate occlusion map, the new integrated facial images are recovered iteratively and put into a recognition process; and (3) the effectiveness on recognition accuracy of our method is verified by comparing it with three typical occlusion map detection methods. Experiments show that the proposed method has a highly accurate detection and recovery performance and that it outperforms several similar state-of-the-art methods against partial contiguous occlusion.
Time-varying multiplex network: Intralayer and interlayer synchronization
Rakshit, Sarbendu; Majhi, Soumen; Bera, Bidesh K.; Sinha, Sudeshna; Ghosh, Dibakar
2017-12-01
A large class of engineered and natural systems, ranging from transportation networks to neuronal networks, are best represented by multiplex network architectures, namely a network composed of two or more different layers where the mutual interaction in each layer may differ from other layers. Here we consider a multiplex network where the intralayer coupling interactions are switched stochastically with a characteristic frequency. We explore the intralayer and interlayer synchronization of such a time-varying multiplex network. We find that the analytically derived necessary condition for intralayer and interlayer synchronization, obtained by the master stability function approach, is in excellent agreement with our numerical results. Interestingly, we clearly find that the higher frequency of switching links in the layers enhances both intralayer and interlayer synchrony, yielding larger windows of synchronization. Further, we quantify the resilience of synchronous states against random perturbations, using a global stability measure based on the concept of basin stability, and this reveals that intralayer coupling strength is most crucial for determining both intralayer and interlayer synchrony. Lastly, we investigate the robustness of interlayer synchronization against a progressive demultiplexing of the multiplex structure, and we find that for rapid switching of intralayer links, the interlayer synchronization persists even when a large number of interlayer nodes are disconnected.
Home visits: why do rates vary so much?
LENUS (Irish Health Repository)
Stewart, P
2012-03-01
Data including information on patient age, gender, who initiated the visit and call classification was collected during office hours from 12 G.P. rural teaching practices with a combined GMS patient population of 24,720, over a 2 month period. There were a total of 603 home visits, giving an annual visiting rate of 143\\/1000. Visiting rates varied between practices from 45 to 305\\/1000 per year. When high visiting practices (>210\\/1000\\/year) were compared to low visiting rate practices (>90\\/1000\\/year), patients tended to be older (79.7 v. 74.5 years) and calls were 12 times more likely to be doctor initiated (16.6% v. 1.4%) or classified as routine( 50.7% v. 44.9%). The variation between practices was related in part to patient age but appears largely due to differences in doctor home visiting behaviour. There are no recent figures on home visiting in Ireland.
NARAC SOFTWARE QUALITY ASSURANCE: ADAPTING FORMALISM TO MEET VARYING NEEDS
Energy Technology Data Exchange (ETDEWEB)
Walker, H; Nasstrom, J S; Homann, S G
2007-11-20
The National Atmospheric Release Advisory Center (NARAC) provides tools and services that predict and map the spread of hazardous material accidentally or intentionally released into the atmosphere. NARAC is a full function system that can meet a wide range of needs with a particular focus on emergency response. The NARAC system relies on computer software in the form of models of the atmosphere and related physical processes supported by a framework for data acquisition and management, user interface, visualization, communications and security. All aspects of the program's operations and research efforts are predicated to varying degrees on the reliable and correct performance of this software. Consequently, software quality assurance (SQA) is an essential component of the NARAC program. The NARAC models and system span different levels of sophistication, fidelity and complexity. These different levels require related but different approaches to SQA. To illustrate this, two different levels of software complexity are considered in this paper. As a relatively simple example, the SQA procedures that are being used for HotSpot, a straight-line Gaussian model focused on radiological releases, are described. At the other extreme, the SQA issues that must be considered and balanced for the more complex NARAC system are reviewed.
Novel regression equations predicting lung age from varied spirometric parameters.
Yamaguchi, Kazuhiro; Omori, Hisamitsu; Onoue, Ayumi; Katoh, Takahiko; Ogata, Yasuhiro; Kawashima, Hidetoshi; Onizawa, Shigemitsu; Tsuji, Takao; Aoshiba, Kazutetsu; Nagai, Atsushi
2012-08-15
Although lung age calculated backward from regression formulas constructed for FEV(1) estimation is widely used, it possesses a couple of faults. We developed novel equations predicting lung age from varied spirometric parameters (spirometry-derived lung age (SDL-age)). Applying multiple regression analysis, equations predicting SDL-age were invented using data from 8015 never-smokers with normal spirometry (group I). Validation was made based on data from 6398 never-smokers with normal spirometry (group II). Equations were further applied for 446 subjects with airflow limitation. FEV(1), FEV(1)/FVC, FEF(50), and PEF were selected as explanatory variables for reference value of SDL-age. Normal limits of difference between SDL-age and chronological-age were ± 13.4 years in the male and ± 15.0 years in the female. Established equations predicted SDL-age of group II. SDL-age was older than chronological-age only in subjects with severe airflow limitation. Novel regression equations allowing prediction of reference value of SDL-age and normal limits of difference between SDL-age and chronological-age were elaborated in both genders. Copyright © 2012 Elsevier B.V. All rights reserved.
Perception of acoustically presented time series with varied intervals.
Wackermann, Jiří; Pacer, Jakob; Wittmann, Marc
2014-03-01
Data from three experiments on serial perception of temporal intervals in the supra-second domain are reported. Sequences of short acoustic signals ("pips") separated by periods of silence were presented to the observers. Two types of time series, geometric or alternating, were used, where the modulus 1+δ of the inter-pip series and the base duration Tb (range from 1.1 to 6s) were varied as independent parameters. The observers had to judge whether the series were accelerating, decelerating, or uniform (3 paradigm), or to distinguish regular from irregular sequences (2 paradigm). "Intervals of subjective uniformity" (isus) were obtained by fitting Gaussian psychometric functions to individual subjects' responses. Progression towards longer base durations (Tb=4.4 or 6s) shifts the isus towards negative δs, i.e., accelerating series. This finding is compatible with the phenomenon of "subjective shortening" of past temporal intervals, which is naturally accounted for by the lossy integration model of internal time representation. The opposite effect observed for short durations (Tb=1.1 or 1.5s) remains unexplained by the lossy integration model, and presents a challenge for further research. © 2013 Elsevier B.V. All rights reserved.
Stability of stationary and time-varying nongyrotropic particle distributions
Directory of Open Access Journals (Sweden)
A. L. Brinca
Full Text Available The ubiquity of nongyrotropic particle populations in space plasmas warrants the study of their characteristics, in particular their stability. The unperturbed nongyrotropic distribution functions in homogeneous media without sources and sinks (closed phase space must be rotating and time-varying (TNG, whereas consideration of open phase spaces allows for the occurrence of homogeneous and stationary distributions (SNG. The free energy brought about by the introduction of gyrophase organization in a particle population can destabilize otherwise thoroughly stable magnetoplasmas (or, a fortiori, enhance pre-existing gyrotropic instabilities and feed intense wave growth both in TNG and SNG environments: The nongyrotropic (electron or ion species can originate unstable coupling among the gyrotropic characteristic waves. The stability properties of these two types of homogeneous nongyrotropy shall be contrasted for parallel (with respect to the ambient magnetic field and perpendicular propagation, and their potential role as wave activity sources shall be illustrated resorting to solutions of the appropriate dispersion equations and numerical simulations.
Key words. Space plasma physics (waves and instabilities · Magnetospheric physics (plasma waves and instabilities · Interplanetary physics (plasma waves and turbulence
The varying ethical attitudes towards resuscitation in Europe.
Baskett, Peter J F; Lim, Andy
2004-09-01
This study was conducted to assess the varying attitudes in Europe towards ethical aspects of resuscitation in Europe. The ethics of resuscitation is a key discussion topic in the European Resuscitation Council Advanced Life Support (ALS) course. A questionnaire was sent to all leading ALS course directors in 20 European countries. All completed the questionnaire. The results were compiled in March 2004. Views were sought on the following ethical aspects:When not to attempt resuscitation Active euthanasia When to abandon resuscitation efforts The diagnosis of death by non physicians Permission for relatives to be with the patient during resuscitation if they wish Teaching on the recently dead Breaking bad news Results: The results reveal a considerable variation in the interpretation of ethical dilemmas within European countries. It is interesting to note that the results do not necessarily conform to traditional beliefs in the characteristic differences between Northern and Southern Europe. The Mediterranean countries do not all have the same attitudes, any more than the Nordic or Central European countries share the same views. There remains a widespread divergence of views on ethical aspects of resuscitation with the countries of Europe that are largely unpredictable according to commonly perceived national characteristics. The trend over the past 6 years is towards a more permissive attitude. For many ethical questions there can be no clear and correct didactic answers.
Cold surge: a sudden and spatially varying threat to health?
Wu, Pei-Chih; Chen, Vivian Yi-Ju; Su, Huey-Jen
2011-01-01
While cold surge is one of the most conspicuous features of the winter monsoon in East Asia, its impact on human health remains underexplored. Based on the definition by the Central Weather Bureau in Taiwan, we identified four cold surges between 2000 and 2003 and collected the cardiovascular disease mortality data two weeks before and two weeks after these events. We attempted to answer the following research questions: 1) whether the cold surges impose an adverse and immediate effect on cardiovascular mortality; 2) whether the people living in temperate zones have a higher tolerance of extreme temperature drop than do those in the subtropics. With geographic weighting techniques, we not only found that the cardiovascular disease mortality rates increased significantly after the cold surges, but also discovered a spatially varying pattern of tolerance to cold surges. Even within a small study area such as Taiwan, human reaction to severe weather drop differs across space. Needless to say, in the U.S., these findings should be considered in redirecting policy to address populations living in warm places when extreme temperature drops occur. PMID:19162302
On the Anonymity Risk of Time-Varying User Profiles
Directory of Open Access Journals (Sweden)
Silvia Puglisi
2017-04-01
Full Text Available Websites and applications use personalisation services to profile their users, collect their patterns and activities and eventually use this data to provide tailored suggestions. User preferences and social interactions are therefore aggregated and analysed. Every time a user publishes a new post or creates a link with another entity, either another user, or some online resource, new information is added to the user profile. Exposing private data does not only reveal information about single users’ preferences, increasing their privacy risk, but can expose more about their network that single actors intended. This mechanism is self-evident in social networks where users receive suggestions based on their friends’ activities. We propose an information-theoretic approach to measure the differential update of the anonymity risk of time-varying user profiles. This expresses how privacy is affected when new content is posted and how much third-party services get to know about the users when a new activity is shared. We use actual Facebook data to show how our model can be applied to a real-world scenario.
Detection of epigenetic changes using ANOVA with spatially varying coefficients.
Guanghua, Xiao; Xinlei, Wang; Quincey, LaPlant; Nestler, Eric J; Xie, Yang
2013-03-13
Identification of genome-wide epigenetic changes, the stable changes in gene function without a change in DNA sequence, under various conditions plays an important role in biomedical research. High-throughput epigenetic experiments are useful tools to measure genome-wide epigenetic changes, but the measured intensity levels from these high-resolution genome-wide epigenetic profiling data are often spatially correlated with high noise levels. In addition, it is challenging to detect genome-wide epigenetic changes across multiple conditions, so efficient statistical methodology development is needed for this purpose. In this study, we consider ANOVA models with spatially varying coefficients, combined with a hierarchical Bayesian approach, to explicitly model spatial correlation caused by location-dependent biological effects (i.e., epigenetic changes) and borrow strength among neighboring probes to compare epigenetic changes across multiple conditions. Through simulation studies and applications in drug addiction and depression datasets, we find that our approach compares favorably with competing methods; it is more efficient in estimation and more effective in detecting epigenetic changes. In addition, it can provide biologically meaningful results.
Partial migration: growth varies between resident and migratory fish.
Gillanders, Bronwyn M; Izzo, Christopher; Doubleday, Zoë A; Ye, Qifeng
2015-03-01
Partial migration occurs in many taxa and ecosystems and may confer survival benefits. Here, we use otolith chemistry data to determine whether fish from a large estuarine system were resident or migratory, and then examine whether contingents display differences in modelled growth based on changes in width of otolith growth increments. Sixty-three per cent of fish were resident based on Ba : Ca of otoliths, with the remainder categorized as migratory, with both contingents distributed across most age/size classes and both sexes, suggesting population-level bet hedging. Migrant fish were in slightly better condition than resident fish based on Fulton's K condition index. Migration type (resident versus migratory) was 56 times more likely to explain variation in growth than a model just incorporating year- and age-related growth trends. While average growth only varied slightly between resident and migratory fish, year-to-year variation was significant. Such dynamism in growth rates likely drives persistence of both life-history types. The complex relationships in growth between contingents suggest that management of species exhibiting partial migration is challenging, especially in a world subject to a changing climate. © 2015 The Author(s) Published by the Royal Society. All rights reserved.
The Activity of Antimicrobial Surfaces Varies by Testing Protocol Utilized.
Directory of Open Access Journals (Sweden)
Matias D Campos
Full Text Available Contaminated hospital surfaces are an important source of nosocomial infections. A major obstacle in marketing antimicrobial surfaces is a lack of efficacy data based on standardized testing protocols.We compared the efficacy of multiple testing protocols against several "antimicrobial" film surfaces.Four clinical isolates were used: one Escherichia coli, one Klebsiella pneumoniae, and two Staphylococcus aureus strains. Two industry methods (modified ISO 22196 and ASTM E2149, a "dried droplet", and a "transfer" method were tested against two commercially available antimicrobial films, one film in development, an untreated control, and a positive (silver control film. At 2 (only ISO and 24 hours following inoculation, bacteria were collected from film surfaces and enumerated.Compared to untreated films in all protocols, there were no significant differences in recovery on either commercial brand at 2 or 24 hours after inoculation. The silver surface demonstrated significant microbicidal activity (mean loss 4.9 Log10 CFU/ml in all methods and time points with the exception of 2 hours in the ISO protocol and the transfer method. Using our novel droplet method, no differences between placebo and active surfaces were detected. The surface in development demonstrated variable activity depending on method, organism, and time point. The ISO demonstrated minimal activity at 2 hours but significant activity at 24 hours (mean 4.5 Log10 CFU/ml difference versus placebo. The ASTEM protocol exhibited significant differences in recovery of staphylococci (mean 5 Log10 CFU/ml but not Gram-negative isolates (10 fold decrease. Minimal activity was observed with this film in the transfer method.Varying results between protocols suggested that efficacy of antimicrobial surfaces cannot be easily and reproducibly compared. Clinical use should be considered and further development of representative methods is needed.
Fluoride in Dental Biofilm Varies across Intra-Oral Regions.
Staun Larsen, Line; Baelum, Vibeke; Tenuta, Livia Maria Andaló; Richards, Alan; Nyvad, Bente
2017-01-01
Information on differences in biofilm fluoride concentration across intra-oral regions may help explain the distribution of caries within the dentition. The aim of this cross-sectional study was to describe the fluoride concentration in saliva and in biofilm fluid and biofilm solids across 6 intra-oral regions. Unstimulated whole saliva was collected from 42 participants and biofilm harvested from the buccal sites in the 4 molar and 2 anterior regions. Samples were collected at least 1 h after use of fluoride dentifrice. No attempt was made to control the participants' food consumption or use of other topical agents. Centrifuged saliva, biofilm fluid, and biofilm solids were analysed for fluoride using a fluoride ion-selective electrode, adapted for microanalysis. Fluoride in biofilm varied across intra-oral regions. The mean biofilm fluid fluoride concentrations across the oral cavity ranged from 11.6 to 16.8 µM, being statistically significantly higher in the upper anterior region than in any other region. In all regions the fluoride concentration in biofilm fluid was higher than in saliva. For biofilm solids the fluoride concentration was highest in the lower anterior region (2,461 μmol/kg) and lowest in the lower molar regions (388 and 406 μmol/kg, respectively). Within biofilm, the solids contained most of the fluoride (81 to >99%). The biofilm fluid fluoride concentration was significantly positively associated with salivary fluoride and only marginally associated with that of biofilm solids. In conclusion, this study has shown pronounced differences in fluoride distribution across intra-oral regions and compartments. This shows that the sampling site is a crucial factor for studies of biofilm fluoride. © 2017 S. Karger AG, Basel.
TDR Using Autocorrelation and Varying-Duration Pulses
Lucena, Angel; Mullinex, Pam; Huang, PoTien; Santiago, Josephine; Mata, Carlos; Zavala, Carlos; Lane, John
2008-01-01
In an alternative to a prior technique of time-domain-reflectometry (TDR) in which very short excitation pulses are used, the pulses have very short rise and fall times and the pulse duration is varied continuously between a minimum and a maximum value. In both the present and prior techniques, the basic idea is to (1) measure the times between the generation of excitation pulses and the reception of reflections of the pulses as indications of the locations of one or more defects along a cable and (2) measure the amplitudes of the reflections as indication of the magnitudes of the defects. In general, an excitation pulse has a duration T. Each leading and trailing edge of an excitation pulse generates a reflection from a defect, so that a unique pair of reflections is associated with each defect. In the present alternative technique, the processing of the measured reflection signal includes computation of the autocorrelation function R(tau) identical with fx(t)x(t-tau)dt where t is time, x(t) is the measured reflection signal at time t, and taus is the correlation interval. The integration is performed over a measurement time interval short enough to enable identification and location of a defect within the corresponding spatial interval along the cable. Typically, where there is a defect, R(tau) exhibits a negative peak having maximum magnitude for tau in the vicinity of T. This peak can be used as a means of identifying a leading-edge/trailing-edge reflection pair. For a given spatial interval, measurements are made and R(tau) computed, as described above, for pulse durations T ranging from the minimum to the maximum value. The advantage of doing this is that the effective signal-to-noise ratio may be significantly increased over that attainable by use of a fixed pulse duration T.
Imaging spatially varying biomechanical properties with neural networks
Hoerig, Cameron; Reyes, Wendy; Fabre, Léo.; Ghaboussi, Jamshid; Insana, Michael F.
2017-03-01
Elastography comprises a set of modalities that image the biomechanical properties of soft tissues for disease detection and diagnosis. Quasi-static ultrasound elastography, in particular, tracks sub-surface displacements resulting from an applied surface force. The local displacement information and measured surface loads may be used to compute a parametric summary of biomechanical properties; however, the inverse problem is under- determined, limiting most techniques to estimating a single linear-elastic parameter. We previously described a new method to develop mechanical models using a combination of computational mechanics and machine learning that circumvents the limitations associated with the inverse problem. The Autoprogressive method weaves together finite element analysis and artificial neural networks (ANNs) to develop empirical models of mechanical behavior using only measured force-displacement data. We are extending that work by incorporating spatial information with the material properties. Previously, the ANNs accepted only a strain vector input and computed the corresponding stress, meaning any spatial information was encoded in the finite element mesh. Now, using a pair of ANNs working in tandem with spatial coordinates included as part of the input, these new Cartesian ANNs are able to learn the spatially varying mechanical behavior of complex media. We show that a single Cartesian ANN is able to describe the same mechanical behavior of an object that previously required at least two ANNs. Furthermore, we show the new ANNs can learn complex material property distributions and reconstruct images of the Young's modulus distribution, not merely classify, filter, or otherwise process an existing image. For the first time, we present results using Cartesian neural networks within the Autoprogressive Method to form elastic modulus images.
Microstructural Model of Ignition for Time Varying Loading Conditions
Browning, Richard V.; Scammon, Richard J.
2002-07-01
A micro-mechanical based model of ignition was developed about five years ago based on a simple inter-granular friction model of mechanical dissipation coupled with a fit to extensive direct numerical simulations of the resulting thermally induced decomposition. The chemical model used was the McGuire-Tarver ODTX based model for HMX decomposition. The resulting power law type model has been reasonably successful in predicting threshold conditions for Steven type experiments. The final power law form was obtained by assuming a constant time history for both the pressure and shear strain rate, resulting in time independent loading conditions for the chemical model. Here we propose to extend the model to handle time varying loading conditions. This is done using a linear operator that models reactive heat transfer simulations done for a wide variety of loading conditions. The linear operator is represented by a convolution integral with Prony series kernel form for efficient numerical implementation. To complete the model the same inter-granular friction model used previously is employed. Comparisons are made with results of numerical simulations and experiments. The technique used here is based on the notion of linearizing the reactive heat transfer problem. Although the chemical model involves four reactions and is highly nonlinear, we effectively linearize the problem around ignition conditions with a linear operator fit. We use a simple power law approximation that gives useful accuracy over at least 4 orders of magnitude in time and fluence. A non-dimensional scaling method is used to determine the final form. We believe the techniques used here could also be used with more detailed chemical models and with other types of mechanical dissipation models.
The Effects of Varying Cosmological Parameters on Halo Substructure
Dooley, Gregory A.; Griffen, Brendan F.; Zukin, Phillip; Ji, Alexander P.; Vogelsberger, Mark; Hernquist, Lars E.; Frebel, Anna
2014-05-01
We investigate how different cosmological parameters, such as those delivered by the WMAP and Planck missions, affect the nature and evolution of the dark matter halo substructure. We use a series of flat Λ cold dark matter cosmological N-body simulations of structure formation, each with a different power spectrum but with the same initial white noise field. Our fiducial simulation is based on parameters from the WMAP seventh year cosmology. We then systematically vary the spectral index, ns ; matter density, Ω M ; and normalization of the power spectrum, σ8, for seven unique simulations. Across these, we study variations in the subhalo mass function, mass fraction, maximum circular velocity function, spatial distribution, concentration, formation times, accretion times, and peak mass. We eliminate dependence of subhalo properties on host halo mass and average the values over many hosts to reduce variance. While the "same" subhalos from identical initial overdensity peaks in higher σ8, ns , and Ω m simulations accrete earlier and end up less massive and closer to the halo center at z = 0, the process of continuous subhalo accretion and destruction leads to a steady state distribution of these properties across all subhalos in a given host. This steady state mechanism eliminates cosmological dependence on all of the properties listed above except for subhalo concentration and V max, which remain greater for higher σ8, ns , and Ω m simulations, and subhalo formation time, which remains earlier. We also find that the numerical technique for computing the scale radius and the halo finder that were used can significantly affect the concentration-mass relationship as computed for a simulation.
Varying influence of environmental gradients on vegetation patterns across biomes
Dahlin, K.; Asner, G. P.; Mascaro, J.; Taylor, P.
2016-12-01
Environmental gradients, like elevation, slope, aspect, and soil properties, filter vegetation types at the local scale. These `environmental filters' create conditions that are conducive to the success or failure of different plant types, influencing landscape-scale heterogeneity in taxonomic diversity, functional diversity, biomass accumulation, greenness, and more. Niche-based models implicitly assume that environmental filtering is the dominant process controlling plant distributions. While environmental filtering is a well understood process, its importance relative to other drivers of heterogeneity, like disturbance, human impacts, and plant-animal interactions, remains unknown and likely varies between biomes. Here we synthesize results from several studies using data from the Carnegie Airborne Observatory - a fused LiDAR and imaging spectroscopy system - that mapped a vegetation patterns in multiple biomes and associated these with environmental gradients. The study sites range from Panama to California, and the patterns range from aboveground carbon to foliar chemistry. We show that at fine spatial scales environmental filtering is a strong predictor of aboveground biomass in a dry system (Jasper Ridge Biological Preserve, California - Dahlin et al 2012) but a weak predictor of plant functional traits in that same system (Dahlin et al 2014), a weak predictor of aboveground carbon in the tropics (Barro Colorado Island, Panama - Mascaro et al 2011; Osa Peninsula, Costa Rica - Taylor et al 2015), and a weak predictor of greenness (NDVI) in a disturbed dry system (Santa Cruz Island, California - Dahlin et al 2014). Collectively, these results suggest that while environmental filtering is an important driver of landscape-scale heterogeneity, it is not the only, or often even the most important, driver for many of these systems and patterns.
Reconciling sensory cues and varied consequences of avian repellents.
Werner, Scott J; Provenza, Frederick D
2011-02-01
We learned previously that red-winged blackbirds (Agelaius phoeniceus) use affective processes to shift flavor preference, and cognitive associations (colors) to avoid food, subsequent to avoidance conditioning. We conducted three experiments with captive red-winged blackbirds to reconcile varied consequences of treated food with conditioned sensory cues. In Experiment 1, we compared food avoidance conditioned with lithium chloride (LiCl) or naloxone hydrochloride (NHCl) to evaluate cue-consequence specificity. All blackbirds conditioned with LiCl (gastrointestinal toxin) avoided the color (red) and flavor (NaCl) of food experienced during conditioning; birds conditioned with NHCl (opioid antagonist) avoided only the color (not the flavor) of food subsequent to conditioning. In Experiment 2, we conditioned experimentally naïve blackbirds using free choice of colored (red) and flavored (NaCl) food paired with an anthraquinone- (postingestive, cathartic purgative), methiocarb- (postingestive, cholinesterase inhibitor), or methyl anthranilate-based repellent (preingestive, trigeminal irritant). Birds conditioned with the postingestive repellents avoided the color and flavor of foods experienced during conditioning; methyl anthranilate conditioned only color (not flavor) avoidance. In Experiment 3, we used a third group of blackbirds to evaluate effects of novel comparison cues (blue, citric acid) subsequent to conditioning with red and NaCl paired with anthraquinone or methiocarb. Birds conditioned with the postingestive repellents did not avoid conditioned color or flavor cues when novel comparison cues were presented during the test. Thus, blackbirds cognitively associate pre- and postingestive consequences with visual cues, and reliably integrate visual and gustatory experience with postingestive consequences to procure nutrients and avoid toxins. Published by Elsevier Inc.
Song trait similarity in great tits varies with social structure.
Directory of Open Access Journals (Sweden)
Lysanne Snijders
Full Text Available For many animals, long-range signalling is essential to maintain contact with conspecifics. In territorial species, individuals often have to balance signalling towards unfamiliar potential competitors (to solely broadcast territory ownership with signalling towards familiar immediate neighbours (to also maintain so-called "dear enemy" relations. Hence, to understand how signals evolve due to these multilevel relationships, it is important to understand how general signal traits vary in relation to the overall social environment. For many territorial songbirds dawn is a key signalling period, with several neighbouring individuals singing simultaneously without immediate conflict. In this study we tested whether sharing a territory boundary, rather than spatial proximity, is related to similarity in dawn song traits between territorial great tits (Parus major in a wild personality-typed population. We collected a large dataset of automatized dawn song recordings from 72 unique male great tits, during the fertile period of their mate, and compared specific song traits between neighbours and non-neighbours. We show here that both song rate and start time of dawn song were repeatable song traits. Moreover, neighbours were significantly more dissimilar in song rate compared to non-neighbours, while there was no effect of proximity on song rate similarity. Additionally, similarity in start time of dawn song was unrelated to sharing a territory boundary, but birds were significantly more similar in start time of dawn song when they were breeding in close proximity of each other. We suggest that the dissimilarity in dawn song rate between neighbours is either the result of neighbouring great tits actively avoiding similar song rates to possibly prevent interference, or a passive consequence of territory settlement preferences relative to the types of neighbours. Neighbourhood structuring is therefore likely to be a relevant selection pressure shaping
Human scalp electroencephalography reveals that repetition suppression varies with expectation
Directory of Open Access Journals (Sweden)
Christopher eSummerfield
2011-07-01
Full Text Available Repetitions of a sensory event elicit lower levels of brain activity than its initial presentation (‘repetition suppression’. According to one view, repetition suppression depends on the biophysics of neuronal discharge, and is thus an automatic consequence of stimulus processing (‘fatigue’ model. Another account suggests that repetition suppression depends on the statistical structure of the environment, and occurs when repeated stimuli are less surprising than novel stimuli (‘surprise reduction’ model. In support of the latter view, functional magnetic resonance imaging studies have shown that repetition suppression is modulated by the local probability of repetition. However, single-cell recordings from macaque inferotemporal area (IT have failed to replicate this finding. Here, we recorded scalp electroencephalography from human participants viewing pairs of faces that repeated (face1-face1 or alternated (face1-face2, in contexts in which repetitions were expected or unexpected. As previously described, event-related potentials in the range of 100-400 ms recorded at posterior electrode sites and at the vertex differed between repetitions and alternations. Critically, at central electrodes, we observed that the difference between repeated and alternating stimuli was attenuated when repetitions were unexpected, as predicted by the surprise reduction model. These findings demonstrate that the modulation of repetitions suppression by repetition probability is observable using direct neural recording methods in human participants, and that it occurs relatively late (>300 ms post-stimulus. Finally, we found that theta-band (4-8 Hz spectral power over central electrodes varied with the three-way interaction between of repetition, expectation, and the rate of change of the environment, consistent with recent reports that frontal theta may be a hallmark of learning processes originating in the anterior cingulate and medial prefrontal
Covariation among glucocorticoid regulatory elements varies seasonally in house sparrows.
Liebl, Andrea L; Shimizu, Toru; Martin, Lynn B
2013-03-01
Glucocorticoids (GCs) help individuals cope with changes throughout life; one such change is the seasonal transition through life-history stages. Previous research shows that many animals exhibit seasonal variation in baseline GCs and GC responses to stressors, but the effects of season on other aspects of GC regulation have been less studied. Moreover, whether elements of GC regulation covary within individuals and whether covariation changes seasonally has been not been investigated. Evolutionarily, strong linkages among GC regulatory elements is predicted to enhance system efficiency and regulation, however may reduce the plasticity necessary to ensure appropriate responses under varying conditions. Here, we measured corticosterone (CORT), the major avian GC, at baseline, after exposure to a restraint stressor, and in response to dexamethasone (to assess negative feedback capacity) in wild house sparrows (Passer domesticus) during the breeding and molting seasons. We also measured hippocampal mRNA expression of the two receptors primarily responsible for CORT regulation: the mineralocorticoid and glucocorticoid receptors (MR and GR, respectively). Consistent with previous studies, restraint-induced CORT was lower during molt than breeding, but negative-feedback was not influenced by season. Receptor gene expression was affected by season, however, as during breeding, the ratio of MR to GR expression was significantly lower than during molt. Furthermore, MR expression was negatively correlated with CORT released in response to a stressor, but only during molt. We found that individuals that most strongly up-regulated CORT in response to restraint were also most effective at reducing CORT via negative feedback; although these relationships were independent of season, they were stronger during molt. Copyright © 2013 Elsevier Inc. All rights reserved.
Adenoma detection rate varies greatly during colonoscopy training.
van Doorn, Sascha C; Klanderman, Robert B; Hazewinkel, Yark; Fockens, Paul; Dekker, Evelien
2015-07-01
The adenoma detection rate (ADR) is considered the most important quality indicator for colonoscopy and varies widely among colonoscopists. It is unknown whether the ADR of gastroenterology consultants can already be predicted during their colonoscopy training. To evaluate the ADR of fellows in gastroenterology and evaluate whether this predicts their ADR as gastroenterology consultants. Retrospective observational study. Academic and regional centers. Symptomatic patients undergoing colonoscopy. The variance in ADR among 7 gastroenterology fellows during their training (between May 2004 and March 2012) and of the same fellows after they registered as consultants (between October 2011 and April 2014) was evaluated. Multivariate logistic regression was performed to compare the highest detector (endoscopist with highest ADR) with the individual fellows and to evaluate whether an ADR of 20% or higher during the training was predictive of a high ADR as a consultant. During training, ADRs ranged from 14% to 36% (P training. An ADR lower than 20% during training was associated with a lower ADR as a consultant (OR 0.51; 95% CI, 0.30-0.87). Retrospective study. Variance in ADR is already present during the endoscopy training of gastroenterology fellows. Most fellows do not improve their ADR after completing their training. These findings suggest that the ADR can be predicted during colonoscopy training, and we suggest that feedback and benchmarking should be implemented early during training of fellows in an effort to improve ADR in future daily practice as a consultant. Copyright © 2015 American Society for Gastrointestinal Endoscopy. Published by Elsevier Inc. All rights reserved.
Titanium (IV) sol-gel chemistry in varied gravity environments
Hales, Matthew; Martens, Wayde; Steinberg, Theodore
Sol-gel synthesis in reduced gravity is a relatively new topic in the literature and further inves-tigation is essential to realise its potential and application to other sol-gel systems. The sol-gel technique has been successfully applied to the synthesis of silica systems of varying porosity for many diverse applications [1-5]. It is proposed that current methods for the synthesis of silica sol-gels in reduced gravity may be applied to titanium sol-gel processing in order to enhance desirable physical and chemical characteristics of the final materials. The physical and chemical formation mechanisms for titanium alkoxide based sol-gels, to date, is not fully understood. However, various authors [6-9] have described potential methods to control the hydrolysis and condensation reactions of titanium alkoxides through the use of chemical inhibitors. A preliminary study of the reaction kinetics of titanium alkoxide sol-gel reaction in normal gravity was undertaken in order to determine reactant mixtures suitable for further testing under varied gravity conditions of limited duration. Through the use of 1H Nuclear Magnetic Resonance spectroscopy (NMR) for structural analysis of precursor materials, Ultra-Violet-Visible spectroscopy (UV-VIS) and viscosity measurements, it was demonstrated that not only could the rate of the chemical reaction could be controlled, but directed linear chain growth within the resulting gel structure was achievable through the use of increased inhibitor concentrations. Two unique test systems have been fabricated to study the effects of varied gravity (reduced, normal, high) on the formation of titanium sol-gels. Whilst the first system is to be used in conjunction with the recently commissioned drop tower facility at Queensland University of Technology in Brisbane, Australia to produce reduced gravity conditions. The second system is a centrifuge capable of providing high gravity environments of up to 70 G's for extended periods of time
van de Velde, Daan J; Schiller, Niels O; van Heuven, Vincent J; Levelt, Claartje C; van Ginkel, Joost; Beers, Mieke; Briaire, Jeroen J; Frijns, Johan H M
2017-05-01
This study aimed to find the optimal filter slope for cochlear implant simulations (vocoding) by testing the effect of a wide range of slopes on the discrimination of emotional and linguistic (focus) prosody, with varying availability of F0 and duration cues. Forty normally hearing participants judged if (non-)vocoded sentences were pronounced with happy or sad emotion, or with adjectival or nominal focus. Sentences were recorded as natural stimuli and manipulated to contain only emotion- or focus-relevant segmental duration or F0 information or both, and then noise-vocoded with 5, 20, 80, 120, and 160 dB/octave filter slopes. Performance increased with steeper slopes, but only up to 120 dB/octave, with bigger effects for emotion than for focus perception. For emotion, results with both cues most closely resembled results with F0, while for focus results with both cues most closely resembled those with duration, showing emotion perception relies primarily on F0, and focus perception on duration. This suggests that filter slopes affect focus perception less than emotion perception because for emotion, F0 is both more informative and more affected. The performance increase until extreme filter slope values suggests that much performance improvement in prosody perception is still to be gained for CI users.
Correlation between maternal and infant cortisol varies by breastfeeding status.
Benjamin Neelon, Sara E; Stroo, Marissa; Mayhew, Meghan; Maselko, Joanna; Hoyo, Cathrine
2015-08-01
The objective of this study was to examine associations of mother and infant salivary cortisol, measured three times over the course of a day, and assess whether these varied by breastfeeding status. We conducted a cross-sectional study of 54 mothers and their infants aged 4-11 months. Mothers collected their own saliva and that of their infants upon awakening, 30min after waking and at bedtime. Breastfeeding status was reported by mothers and cortisol level was measured in saliva in μg/dl using standard techniques. We used generalized linear models to evaluate relationships between maternal and infant cortisol levels, and assessed whether the relationship differed by breastfeeding status: formula only compared to partial and full breastfeeding, adjusting for infant sex, race, age, maternal education, and family income. Thirty-four infants received formula only and 20 were either partially or fully breastfed. Breastfeeding was associated with higher household income, higher maternal education, and white race. Cortisol levels were higher among breastfed infants at all three time points. After adjustment, maternal cortisol levels were related with infant cortisol at bedtime only (regression estimate 0.06; 95% CI: 0.10, 1.1; p=0.02). The adjusted association between bedtime maternal and infant cortisol was stronger among breastfeeding dyads than among formula-feeding dyads (regression estimate 1.0; 95% CI: 0.1, 2.0; p=0.04 vs. 0.6; CI: -0.1, 1.3; p=0.10). In addition, we assessed the influence of maternal education and household income in our adjusted model; income strengthened the observed association, whereas maternal education did not change the estimate. Breastfeeding mothers and infants had significant correlations for cortisol at bedtime, while formula-feeding dyads did not. These data suggest that several factors may contribute to cortisol synchrony observed in mother/infant dyads, including the transfer of cortisol in human milk, physical interaction such as
Does the HI Mass Function Vary with Environment?
Minchin, Robert F.
2017-01-01
Based on analysis of a large dataset from the ALFALFA survey, Jones et al. (2016) recently claimed that the slope of the HI mass function is constant across different galactic environments, defined by their density. They point out that this finding is “perplexing” given that many previous studies have found that the HI mass functions of groups of galaxies have flat slopes, while the general field has a relatively steep slope. I argue that the analysis of Jones et al., and similar analyses in the past, is flawed as they examine the HI mass function of the galaxies found in environments with a given density, summed across the survey, not the HI mass function actually present in the individual structures at that density. If the position of the knee in the HI mass function were to vary between these structures, then the slope of the HI mass function found by summing across all of the structures with a given density would be steeper than the slope actually found in the individual structures. For example, if a survey were to contain three groups of galaxies, all with flat HI mass functions, but with the ‘knee’, at the mass of the largest galaxy in the group, at 108, 109 and 1010 solar masses, then the summed HI mass function would appear to have a knee at 1010 solar masses and a steep slope below this, rather than the flat slope that is actually present in the individual environments. It is not possible, therefore, to say from the analysis of Jones et al. that there is no dependence of the HI mass function on environment. This scenario explains the “seemingly contradictory findings” of Jones et al. and the earlier studies of individual groups as being due to differences in what is being studies, without having to invoke methodological errors in the derivation of the HI mass function.The Arecibo Observatory is operated by SRI International under a cooperative agreement with the National Science Foundation (AST-1100968), and in alliance with Ana G. M
Directory of Open Access Journals (Sweden)
S Abelman
2006-01-01
Full Text Available Refractive state can be regarded as a dynam-ic quantity. Multiple measurements of refractive state can be determined easily and rapidly on a number of different occasions using an autore-fractor. In an experimental trial undertaken by Gillan, a 30-year-old female was subjected to 30 autorefractor measurements each taken at vari-ous intervals before and after the instillation of Mydriacyl 1% (tropicamide into her right eye. The purpose of this paper is to apply multivar-iate analysis of variance (MANOVA to Gillan’s sample data in order to assess whether instillation of Mydriacyl into the eye affects variability of distance refractive state as well as mean distance refractive state as measured by an autorefractor. In five of the seven cases where pairwise hypotheses tests were performed, it is con-cluded that at a 99% level of confidence there is no difference in variability of distance refrac-tive state before and after cycloplegia. In two of the three cases where MANOVA was applied, there is a significant difference at a 95% and at a 99% level of confidence in both variability of distance refractive state and mean distance refractive state with and without cycloplegia.
Thermal shock behaviour of different tungsten grades under varying conditions
Energy Technology Data Exchange (ETDEWEB)
Wirtz, Oliver Marius
2012-07-19
Thermonuclear fusion power plants are a promising option to ensure the energy supply for future generations, but in many fields of research enormous challenges have to be faced. A major step on the way to the prototype fusion reactor DEMO will be ITER which is build in Cadarache, southern France. One of the most critical issues is the field of in-vessel materials and components, in particular the plasma facing materials (PFM). PFMs that will be used in a device like ITER have to withstand severe environmental conditions in terms of steady state and transient thermal loads as well as high particle fluxes such as hydrogen, helium and neutrons. Candidate wall materials are beryllium, tungsten and carbon based materials like CFC (carbon fibre composite). Tungsten is the most promising material for an application in the divertor region with very severe loading conditions and it will most probably also be used as PFM for DEMO. Hence, this work focuses on the investigation of the thermal shock response of different tungsten grades in order to understand the damage mechanisms and to identify material parameters which influence this behaviour under ITER and DEMO relevant operation conditions. Therefore the microstructure and the mechanical and thermal properties of five industrially manufactured tungsten grades were characterised. All five tungsten grades were exposed to transient thermal events with very high power densities of up to 1.27 GWm{sup -2} at varying base temperatures between RT and 600 C in the electron beam device JUDITH 1. The pulse numbers were limited to a maximum of 1000 in order to avoid immoderate workload on the test facility and to have enough time to cover a wide range of loading conditions. The results of this damage mapping enable to define different damage and cracking thresholds for the investigated tungsten grades and to identify certain material parameters which influence the location of these thresholds and the distinction of the induced
STATISTICAL PROCESSES, MAXIMUM LIKELIHOOD ESTIMATION, *INTERSYMBOL INTERFERENCE, TIME VARYING SYSTEMS, VITERBI DECODING, COMPUTERIZED SIMULATION, DATA TRANSMISSION SYSTEMS , *DIGITAL COMMUNICATION SYSTEMS
Pehlivan, M; Hashash, YMA; Harmon, JA; Rathje, EM; Stewart, JP; Silva, SJ; Campbell, KW; Nikolaou, S
2015-01-01
Spatial variability and uncertainties that exist in natural deposits are often modeled in one-dimensional (1D) site response analysis through multiple spatially varied shear wave velocity (VS) profiles. These spatially varied VS profiles usually exhibit VS reversals that might not be observed in the natural deposits. This study investigates the consequences of allowing VS reversals in spatially varied VS on the 1D site response characteristics. Two sets of sixty (60) spatially varied VS profi...
Barrow, John D
2009-01-01
We review properties of cosmological theories for the variation of the fine structure 'constant'. We highlight some general features of the cosmological models that exist in these theories with reference to recent quasar data that are consistent with time-variation in the fine structure 'constant' since a redshift of 3.5.
Energy Technology Data Exchange (ETDEWEB)
Howard, Richard H [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); McDuffee, Joel Lee [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Okuniewski, Maria A. [Idaho National Lab. (INL), Idaho Falls, ID (United States)
2015-09-01
This report details the fabrication and delivery of two Fuel Cycle Research and Development irradiation capsules (FCRP20 and FCRP03), with associated quality assurance documentation, to the High Flux Isotope Reactor. The capsules and documentation were delivered by September 30, 2015, thus meeting the deadline for milestone M3FT-15OR0203112. These irradiation experiments irradiate metal parallelepiped specimens that may consist of various compositions including uranium metal, steel, etc. This document contains a copy of the completed capsule fabrication request sheets, which detail all constituent components, pertinent drawings, etc., along with a detailed summary of the capsule assembly process performed by the Thermal Hydraulics and Irradiation Engineering Group (THIEG) in the Reactor and Nuclear Systems Division. A complete fabrication package record is maintained by THIEG and is available upon request.
Observer-based linear parameter varying H∞ tracking control for hypersonic vehicles
Directory of Open Access Journals (Sweden)
Yiqing Huang
2016-11-01
Full Text Available This article aims to develop observer-based linear parameter varying output feedback H∞ tracking controller for hypersonic vehicles. Due to the complexity of an original nonlinear model of the hypersonic vehicle dynamics, a slow–fast loop linear parameter varying polytopic model is introduced for system stability analysis and controller design. Then, a state observer is developed by linear parameter varying technique in order to estimate the unmeasured attitude angular for slow loop system. Also, based on the designed linear parameter varying state observer, a kind of attitude tracking controller is presented to reduce tracking errors for all bounded reference attitude angular inputs. The closed-loop linear parameter varying system is proved to be quadratically stable by Lypapunov function technique. Finally, simulation results show that the developed linear parameter varying H∞ controller has good tracking capability for reference commands.
How do experiences of physiotherapy and osteopathy vary between NHS and private practice?
Bradbury, Katherine
2013-01-01
Previous research had shown that experiences of treatments vary between NHS and private practice. It was unclear whether different treatments might vary in the same or in different ways between healthcare sectors. This thesis explored how experiences of physiotherapy and osteopathy vary between NHS and private settings.Study 1: A systematic review of the literature identified psychosocial factors which are likely to be important within physiotherapy for lower back pain.Study 2: A qualitative ...
Todd E. Clark; Francesco Ravazzolo
2012-01-01
This paper compares alternative models of time-varying macroeconomic volatility on the basis of the accuracy of point and density forecasts of macroeconomic variables. In this analysis, we consider both Bayesian autoregressive and Bayesian vector autoregressive models that incorporate some form of time-varying volatility, precisely stochastic volatility (both with constant and time-varying autoregressive coeffi cients), stochastic volatility following a stationary AR process, stochastic volat...
National Research Council Canada - National Science Library
Sznaier, Mario
2001-01-01
.... In this chapter we propose a suboptimal regulator for nonlinear parameter varying, control affine systems based upon the combination of model predictive and control Lyapunov function techniques...
Identification of Time-Varying Pilot Control Behavior in Multi-Axis Control Tasks
Zaal, Peter M. T.; Sweet, Barbara T.
2012-01-01
Recent developments in fly-by-wire control architectures for rotorcraft have introduced new interest in the identification of time-varying pilot control behavior in multi-axis control tasks. In this paper a maximum likelihood estimation method is used to estimate the parameters of a pilot model with time-dependent sigmoid functions to characterize time-varying human control behavior. An experiment was performed by 9 general aviation pilots who had to perform a simultaneous roll and pitch control task with time-varying aircraft dynamics. In 8 different conditions, the axis containing the time-varying dynamics and the growth factor of the dynamics were varied, allowing for an analysis of the performance of the estimation method when estimating time-dependent parameter functions. In addition, a detailed analysis of pilots adaptation to the time-varying aircraft dynamics in both the roll and pitch axes could be performed. Pilot control behavior in both axes was significantly affected by the time-varying aircraft dynamics in roll and pitch, and by the growth factor. The main effect was found in the axis that contained the time-varying dynamics. However, pilot control behavior also changed over time in the axis not containing the time-varying aircraft dynamics. This indicates that some cross coupling exists in the perception and control processes between the roll and pitch axes.
The Effects of Constant versus Varied Reinforcers on Preference and Resistance to Change
Milo, Jessie-Sue; Mace, F. Charles; Nevin, John A.
2010-01-01
Previous research has demonstrated that factors such as reinforcer frequency, amount, and delay have similar effects on resistance to change and preference. In the present study, 4 boys with autism made choices between a constant reinforcer (one that was the same food item every trial) and a varied food reinforcer (one that varied randomly between…
2006-09-01
AVATARS IN DISPLAY DESIGN TO SUPPORT SPATIAL AWARENESS UNDER VARYING WORKLOAD CONDITIONS by Dimitrios Myttas September 2006 Thesis Advisor...Avatars in Display Design to Support Spatial Awareness under Varying Workload Conditions 6. AUTHOR(S) Dimitrios Myttas 5. FUNDING NUMBERS 7...24 5. Human Performance – Workload Measurement ................. 24 III. PROPOSED DISPLAY DESIGN ................................................................... 27
NARX-based BPSO modelling for time-varying steam temperature of ...
African Journals Online (AJOL)
This paper focuses on a nonlinear modelling for a time-varying process of steam temperature by employing a polynomial Nonlinear Auto-Regressive with Exogenous Input (NARX) structure based on Binary Particle Swarm Optimization (BPSO) algorithm. The system identification time-varying steam temperature data was ...
Effect of Varying Concentrations of Auxin (2,4-D) on In vitro Callus ...
African Journals Online (AJOL)
Study was carried out to determine the effect of varying concentrations of auxin on callus initiation using the leaves Artemisia annua as explants which were sterilized and inoculated into Murashig and Skoog basal medium supplemented with varying concentrations of 2,4-Dichlorophenoxy acetic acid (2,4-D) and incubated ...
Spatial variation of fuel loading within varying aged stands of chaparral
Kellie A. Uyeda; Douglas A. Stow; John F. O' Leary; Ian T. Schmidt; Philip J. Riggan
2016-01-01
Questions: How do stand-level biomass and percentage of deadmaterial in chaparral vary as a function of stand age? How do the landscape properties of aggregation index and patch size vary in each of the dominant species groups as a function of stand age? Location: Stands of 7-, 28-and 68-yr-old...
Castellini, Federica; Colombo, Monica; Maffeis, Daniele; Montali, Lorenzo
2011-01-01
This study investigates the sense of community and interethnic relations in two different metropolitan areas that vary in ethnic heterogeneity. The study was conducted in Milan, Italy using a sample of 318 participants living in different city districts that vary in ethnic heterogeneity (low vs. high). The participants completed a questionnaire…
LMI-based gain scheduled controller synthesis for a class of linear parameter varying systems
DEFF Research Database (Denmark)
Bendtsen, Jan Dimon; Anderson, Brian; Lanzon, Alexander
2006-01-01
This paper presents a novel method for constructing controllers for a class of single-input multiple-output (SIMO) linear parameter varying (LPV) systems. This class of systems encompasses many physical systems, in particular systems where individual components vary with time, and is therefore...
DEFF Research Database (Denmark)
Chon, Ki H; Zhong, Yuru; Moore, Leon C
2008-01-01
The extent to which renal blood flow dynamics vary in time and whether such variation contributes substantively to dynamic complexity have emerged as important questions. Data from Sprague-Dawley rats (SDR) and spontaneously hypertensive rats (SHR) were analyzed by time-varying transfer functions...
2015-09-01
ARL-TR-7532 ● SEP 2015 US Army Research Laboratory Characterization of Extremely Lightweight Intrusion Detection (ELIDe) Power...SEP 2015 US Army Research Laboratory Characterization of Extremely Lightweight Intrusion Detection (ELIDe) Power Utilization with Varying...Characterization of Extremely Lightweight Intrusion Detection (ELIDe) Power Utilization with Varying Throughput and Payload Sizes 5a. CONTRACT NUMBER W911QX-07
Eesti filmil läks hästi Karlovy Vary festivalil / Marianne Kõrver
Kõrver, Marianne, 1980-
2006-01-01
Lühimängufilm "Tühirand", režissöör Veiko Õunpuu, osales Karlovy Vary rahvusvahelise filmifestivali "Forum of Independents" programmis. 41. Karlovy Vary filmifestivali avas Korea režissööri Kim Ki-duki "Aeg". Lühidalt ka auhinnatutest ja huvitavamatest filmidest
Bossy and Nice Requests: Varying Language Register in Speakers with Autism Spectrum Disorder (ASD)
Volden, Joanne; Sorenson, Autumn
2009-01-01
The ability to vary language style or register is important for successfully navigating social situations. For example, we speak differently to our boss than we do to our children. This project examined whether high-functioning speakers with ASD were able to vary the language used for requests along continua of "politeness/bossiness", whether any…
Estimation of time-varying selectivity in stock assessments using state-space models
DEFF Research Database (Denmark)
Nielsen, Anders; Berg, Casper Willestofte
2014-01-01
-varying selectivity pattern. The fishing mortality rates are considered (possibly correlated) stochastic processes, and the corresponding process variances are estimated within the model. The model is applied to North Sea cod and it is verified from simulations that time-varying selectivity can be estimated......Time-varying selectivity is one of the main challenges in single species age-based assessment models. In classical deterministic VPA-type models the fishing mortality rates are unfiltered representations of the observed catches. As a consequence the selectivity becomes time......-varying, but this representation is too fluctuating, because it includes the observation noise. In parametric statistical catch at age models a common assumption is that the selectivity is constant in all years, although time-varying selectivity can be introduced by splitting the data period in blocks with different selectivities...
Quantum Yield of Reflection Mode Varied Doping GaN Photocathode
Directory of Open Access Journals (Sweden)
Qiao Jianliang
2016-01-01
Full Text Available Using the NEA photocathode activation and evaluation experiment system, the varied doping GaN photocathode has been activated and evaluated. According to the diffusion and orientation drifting equation, the quantum yield formula of reflection mode varied doping NEA GaN photocathode was gotten. The factors affecting the quantum efficiency of varied doping GaN photocathode were studied. For the varied doping GaN photocathode, the quantum efficiency is mainly decided by the escape probability of electron P, he absorption coefficient α, the electron diffuse length LD, the reflectance of cathode materials for incident light R, emission layer thickness Te and the inside electric field E. The experiment and analysis results show: With the directional inside electric field in the bulk, the varied doping NEA GaN photocathode has better photoemission performance than uniform doping photocathode.
Fast space-varying convolution and its application in stray light reduction
Wei, Jianing; Cao, Guangzhi; Bouman, Charles A.; Allebach, Jan P.
2009-02-01
Space-varying convolution often arises in the modeling or restoration of images captured by optical imaging systems. For example, in applications such as microscopy or photography the distortions introduced by lenses typically vary across the field of view, so accurate restoration also requires the use of space-varying convolution. While space-invariant convolution can be efficiently implemented with the Fast Fourier Transform (FFT), space-varying convolution requires direct implementation of the convolution operation, which can be very computationally expensive when the convolution kernel is large. In this paper, we develop a general approach to the efficient implementation of space-varying convolution through the use of matrix source coding techniques. This method can dramatically reduce computation by approximately factoring the dense space-varying convolution operator into a product of sparse transforms. This approach leads to a tradeoff between the accuracy and speed of the operation that is closely related to the distortion-rate tradeoff that is commonly made in lossy source coding. We apply our method to the problem of stray light reduction for digital photographs, where convolution with a spatially varying stray light point spread function is required. The experimental results show that our algorithm can achieve a dramatic reduction in computation while achieving high accuracy.
Shi, Lei; Yao, Bo; Zhao, Lei; Liu, Xiaotong; Yang, Min; Liu, Yanming
2018-01-01
The plasma sheath-surrounded hypersonic vehicle is a dynamic and time-varying medium and it is almost impossible to calculate time-varying physical parameters directly. The in-fight detection of the time-varying degree is important to understand the dynamic nature of the physical parameters and their effect on re-entry communication. In this paper, a constant envelope zero autocorrelation (CAZAC) sequence based on time-varying frequency detection and channel sounding method is proposed to detect the plasma sheath electronic density time-varying property and wireless channel characteristic. The proposed method utilizes the CAZAC sequence, which has excellent autocorrelation and spread gain characteristics, to realize dynamic time-varying detection/channel sounding under low signal-to-noise ratio in the plasma sheath environment. Theoretical simulation under a typical time-varying radio channel shows that the proposed method is capable of detecting time-variation frequency up to 200 kHz and can trace the channel amplitude and phase in the time domain well under -10 dB. Experimental results conducted in the RF modulation discharge plasma device verified the time variation detection ability in practical dynamic plasma sheath. Meanwhile, nonlinear phenomenon of dynamic plasma sheath on communication signal is observed thorough channel sounding result.
Innovative Varied-Fidelity Simulation Mobile Teaching Cart and Education Project.
Harding, Andrew D; Cullinane Whalen, Kathryn; Silverman, Bradley S
2015-09-01
The use of a varied-fidelity simulation mobile teaching cart is a teaching tool that offers unique advantages in the acute care setting. The cart is used to demonstrate the use of patient monitoring devices, and there are a variety of software tools available with the monitoring technology to ensure that the outputs, including electrocardiographic waves, are analyzed appropriately by nursing staff using this varied-fidelity simulation mobile teaching cart. Bringing varied-fidelity simulation to the nurses' work area is a unique application setting. Copyright © 2015 Emergency Nurses Association. Published by Elsevier Inc. All rights reserved.
Evaluation participative multilocale et pluriannuelle de variétés de mil
African Journals Online (AJOL)
... le mil est l'une des céréales dominantes. Les variétés testées étaient des obtentions du programme d'amélioration variétale du mil à partir des populations locales à la station de recherche de Ferkessédougou. Ces variétés ont été obtenues après avoir fait des évaluations de rendement sur des parcelles expérimentales.
Directory of Open Access Journals (Sweden)
Mingzhu Song
2016-01-01
Full Text Available We address the problem of globally asymptotic stability for a class of stochastic nonlinear systems with time-varying delays. By the backstepping method and Lyapunov theory, we design a linear output feedback controller recursively based on the observable linearization for a class of stochastic nonlinear systems with time-varying delays to guarantee that the closed-loop system is globally asymptotically stable in probability. In particular, we extend the deterministic nonlinear system to stochastic nonlinear systems with time-varying delays. Finally, an example and its simulations are given to illustrate the theoretical results.
The stability of multichannel sound systems with time-varying mixing matrices.
Schlecht, Sebastian J; Habets, Emanuël A P
2016-07-01
Various time-varying algorithms have been applied in multichannel sound systems to improve the system's stability and, among these, frequency shifting has been demonstrated to reach the maximum stability improvement achievable by time-variation in general. However, the modulation artifacts have been found to diminish the gain improvement unusable for a higher number of channels and high-quality applications such as music reproduction. This paper proposes alternatively time-varying mixing matrices, which is an efficient algorithm corresponding to symmetric up and down frequency shifting. It is shown with a statistical approach that time-varying mixing matrices can as well achieve maximum stability improvement for a higher number of channels. A listening test demonstrates the improved quality of time-varying mixing matrices over frequency shifting.
Bishop, J. L.; Rampe, E. B.
2014-07-01
The presence of nanophase allophane, opal and Fe-rich material at Mawrth Vallis together with multiple phyllosilicates indicate varying environmental conditions over time and also suggests regionally different aqueous environments.
Quantifying catchment-scale mixing and its effect on time-varying travel time distributions
Velde, van der Y.; Torfs, P.J.J.F.; Zee, van der S.E.A.T.M.; Uijlenhoet, R.
2012-01-01
Travel time distributions are often used to characterize catchment discharge behavior, catchment vulnerability to pollution and pollutant loads from catchments to downstream waters. However, these distributions vary with time because they are a function of rainfall and evapotranspiration. It is
Quantifying catchment-scale mixing and its effects on time varying travel time distributions
Velde, Y. van der; Torfs, P.J.J.F.; Zee, S.E.A.T.M. van der; Uijlenhoet, R.
2012-01-01
Travel time distributions are often used to characterize catchment discharge behavior, catchment vulnerability to pollution and pollutant loads from catchments to downstream waters. However, these distributions vary with time because they are a function of rainfall and evapotranspiration. It is
perceptions paysannes sur la double riziculture et les variétés de riz ...
African Journals Online (AJOL)
Irrigation et intensification de la production agricole au Sahel : perceptions paysannes sur la double riziculture et les variétés de riz utilisées sur les aménagements hydro - agricoles au Niger.
Clinical Trial Results Vary Widely, But Always Advance Research | NIH MedlinePlus the Magazine
... this page please turn Javascript on. Feature: Clinical Trials Clinical Trial Results Vary Widely, But Always Advance Research Past ... emotional." Should You Be Interested in a Clinical Trial People volunteer to take part in clinical trials ...
National Research Council Canada - National Science Library
Zhou, Mu; Tian, Zengshan; Xu, Kunjie; Yu, Xiang; Wu, Haibo
2014-01-01
...) in logarithmic received signal strength (RSS) varying Wi-Fi environment. To the best of our knowledge, little comprehensive analysis work has appeared on the error performance of neighbor matching localization with respect to the deployment of RPs...
National Research Council Canada - National Science Library
Zhou, Mu; Tian, Zengshan; Xu, Kunjie; Yu, Xiang; Wu, Haibo
2014-01-01
...) in logarithmic received signal strength (RSS) varying Wi-Fi environment. To the best of our knowledge, little comprehensive analysis work has appeared on the error performance of neighbor matching localization with respect to the deployment of RPs...
Xie, Tian; Cui, Baoshan; Li, Shanze
2017-10-15
Important to conserve plant species in coastal wetlands throughout their life cycle. All life stages in these habitats are exposed to varying tidal cycles. It is necessary to investigate all life stages as to how they respond to varying tidal regimes. We examine three wetlands containing populations of an endangered halophyte species, each subjected to different tidal regimes: (1). wetlands completely closed to tidal cycles; (2). wetlands directly exposed to tidal cycles (3). wetlands exposed to a partially closed tidal regime. Our results showed that the most threatened stage varied between wetlands subjected to these varying tidal regimes. We hypothesis that populations of this species have adapted to these different tidal regimes. Such information is useful in developing management options for coastal wetlands and modifying future barriers restricting tidal flushing. Copyright © 2017 Elsevier Ltd. All rights reserved.
Three University Case Studies Show Varying Levels of Sophistication With All Systems GO For MIS
Kornfield, Leo
1971-01-01
Three university case studies - the University of Utah, Ohio State University and the University of Illinois - show varying levels of sophistication in their application, modification and practical use of management information systems. (Editor)
Modeling of Electricity Demand for Azerbaijan: Time-Varying Coefficient Cointegration Approach
Directory of Open Access Journals (Sweden)
Jeyhun I. Mikayilov
2017-11-01
Full Text Available Recent literature has shown that electricity demand elasticities may not be constant over time and this has investigated using time-varying estimation methods. As accurate modeling of electricity demand is very important in Azerbaijan, which is a transitional country facing significant change in its economic outlook, we analyze whether the response of electricity demand to income and price is varying over time in this economy. We employed the Time-Varying Coefficient cointegration approach, a cutting-edge time-varying estimation method. We find evidence that income elasticity demonstrates sizeable variation for the period of investigation ranging from 0.48% to 0.56%. The study has some useful policy implications related to the income and price aspects of the electricity consumption in Azerbaijan.
Modeling and simulation of a time-varying inertia aircraft in aerial refueling
National Research Council Canada - National Science Library
Wang Haitao Dong Xinmin Xue Jianping Liu Jiaolong Wang Jian
2016-01-01
Studied in this paper is dynamic modeling and simulation application of the receiver aircraft with the time-varying mass and inertia property in an integrated simulation environment which includes two...
Computational Simulation of VARI Fluid Process Molding for Stiffened Panel Structural Composites
Directory of Open Access Journals (Sweden)
XIAO Fei
2016-08-01
Full Text Available The resin filling time can be predicted and the flow pattern of resin can be simulated in Composites VARI Fluid Process Molding with simulation software PAM-RTM. The permeability is important parameter in VARI process. In-plane and transverse permeability are usually tested with complicate and expensive enclosed mold.A set of model with simple structure, easy operation, low cost, was built to obtain accurate permeability by using a process of vacuum-assisted resin infusion (VARI. Besides, the method of equivalent model was employed. The simulation results of effective model is compared with those of experimental VARI process. The filling times for simulation method is 254 s which is shorter than 301 s of the experimental process. Based on flow runner project with equivalent model, the stiffened panel structural composite is prepared to validate the selective process.
Gut Microbiomes of Indian Children of Varying Nutritional Status: e95547
National Research Council Canada - National Science Library
Tarini Shankar Ghosh; Sourav Sen Gupta; Tanudeep Bhattacharya; Deepak Yadav; Anamitra Barik; Abhijit Chowdhury; Bhabatosh Das; Sharmila S Mande; G Balakrish Nair
2014-01-01
.... Consequently, dysbiosis of the gut microbiota has been implicated in malnutrition. Methodology/Principal Findings Metagenomics approach was adopted to investigate the gut microbiome sampled from 20 rural Indian children with varying nutritional status...
Design of reduced-order state estimators for linear time-varying multivariable systems
Nguyen, Charles C.
1987-01-01
The design of reduced-order state estimators for linear time-varying multivariable systems is considered. Employing the concepts of matrix operators and the method of canonical transformations, this paper shows that there exists a reduced-order state estimator for linear time-varying systems that are 'lexicography-fixedly observable'. In addition, the eigenvalues of the estimator can be arbitrarily assigned. A simple algorithm is proposed for the design of the state estimator.
Arbitrary eigenvalue assignments for linear time-varying multivariable control systems
Nguyen, Charles C.
1987-01-01
The problem of eigenvalue assignments for a class of linear time-varying multivariable systems is considered. Using matrix operators and canonical transformations, it is shown that a time-varying system that is 'lexicography-fixedly controllable' can be made via state feedback to be equivalent to a time-invariant system whose eigenvalues are arbitrarily assignable. A simple algorithm for the design of the state feedback is provided.
Pravin*, Jeyapratha
2016-01-01
This paper ambit to evaluate the flexural strength of glass fiber sandwich panels with varying z-pins pitches. Failure of sandwich panel are delamination and core shear, to minimize the crack propagation, pins are inserted in z-direction, by varying pitches through its thickness. During the insertion of pin, may cause the material some damage. Despite the damage, flexural property does not affected due interpolation of pins. Although the experiment were pull out with a phenomenal results of z...
2017-04-13
AFRL-RX-WP-JA-2017-0338 SUBSTRATE DEFORMATION CURVATURES DUE TO FILM MISMATCH STRAIN FOR SPATIALLY VARYING SUBSTRATE AND FILM ...22 July 2013 – 13 March 2017 4. TITLE AND SUBTITLE SUBSTRATE DEFORMATION CURVATURES DUE TO FILM MISMATCH STRAIN FOR SPATIALLY VARYING SUBSTRATE...AND FILM THICKNESSES (PREPRINT) 5a. CONTRACT NUMBER IN-HOUSE 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 1) Craig P
Tomographic Probability Representation for States of Charge moving in Varying Field
V. I. Man'ko; Zhebrak, E. D.
2012-01-01
The coherent and Fock states of a charge moving in varying homogeneous magnetic field are studied in the tomographic probability representation of quantum mechanics. The states are expressed in terms of quantum tomograms. The coherent states tomograms are shown to be described by normal distributions with varying dispersions and means. The Fock state tomograms are given in the form of probability distributions described by multivariable Hermite polynomials with time-dependent arguments.
Optimal Control of a Delay-Varying Computer Virus Propagation Model
Ren, Jianguo; Xu, Yonghong; Zhang, Chunming
2013-01-01
By incorporating the objective of keeping a low number of infected nodes and a high number of recovered nodes at a lower cost into a known computer virus model (the delay-varying SIRC model) extended by introducing quarantine, a novel model is described by means of the optimal control strategy and theoretically analyzed. Through the comparison of simulation results, it is shown that the propagation of computer virus with varying latency period can be suppressed effectively by the optimal cont...
1999-01-01
arriving cue ( primacy ), sometimes in favor of the last ( recency ), and sometimes in favor of both, with cues arriving in the middle of a sequence...INFORMATION SOURCES OF VARYING WEIGHTS: THE EFFECT OF DISPLAY FEATURES AND ATTENTION CUEING Christopher D. Wickens, Heather L. Pringle, and James Merlo...SUBTITLE Integration of Information Sources of Varying Weights: The Effect of Display Features and Attention Cueing 5a. CONTRACT NUMBER 5b. GRANT
Framework for Processing Videos in the Presence of Spatially Varying Motion Blur
2016-02-10
AFRL-AFOSR-JP-TR-2016-0030 Framework for Processing Videos in the Presence of Spatially Varying Motion Blur Ambasamudram Rajagopalan INDIAN...for Processing Videos in the Presence of Spatially Varying Motion Blur 5a. CONTRACT NUMBER FA23861314138 5b. GRANT NUMBER 13RSZ116_134138 5c... video analysis, Image Processing, Video analysis, Information Technology 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT SAR 18. NUMBER OF
Diversité variétale de manioc sur la base des nominations ...
African Journals Online (AJOL)
SARAH
31 août 2016 ... Compte tenu des différences de portefeuilles variétaux observés, la mise en place d'une stratégie de conservation combinant conservation in et ex-situ semble nécessaire pour une production durable des ressources génétique du manioc au Congo. Mot clés : Diversité variétale, Manihot esculenta Crantz, ...
International Stock Market Efficiency: A Non-Bayesian Time-Varying Model Approach
Mikio Ito; Akihiko Noda; Tatsuma Wada
2012-01-01
This paper develops a non-Bayesian methodology to analyze the time-varying structure of international linkages and market efficiency in G7 countries. We consider a non-Bayesian time-varying vector autoregressive (TV-VAR) model, and apply it to estimate the joint degree of market efficiency in the sense of Fama (1970, 1991). Our empirical results provide a new perspective that the international linkages and market efficiency change over time and that their behaviors correspond well to historic...
Yoon, Heonjun; Kim, Miso; Park, Choon-Su; Youn, Byeng D.
2018-01-01
Piezoelectric vibration energy harvesting (PVEH) has received much attention as a potential solution that could ultimately realize self-powered wireless sensor networks. Since most ambient vibrations in nature are inherently random and nonstationary, the output performances of PVEH devices also randomly change with time. However, little attention has been paid to investigating the randomly time-varying electroelastic behaviors of PVEH systems both analytically and experimentally. The objective of this study is thus to make a step forward towards a deep understanding of the time-varying performances of PVEH devices under nonstationary random vibrations. Two typical cases of nonstationary random vibration signals are considered: (1) randomly-varying amplitude (amplitude modulation; AM) and (2) randomly-varying amplitude with randomly-varying instantaneous frequency (amplitude and frequency modulation; AM-FM). In both cases, this study pursues well-balanced correlations of analytical predictions and experimental observations to deduce the relationships between the time-varying output performances of the PVEH device and two primary input parameters, such as a central frequency and an external electrical resistance. We introduce three correlation metrics to quantitatively compare analytical prediction and experimental observation, including the normalized root mean square error, the correlation coefficient, and the weighted integrated factor. Analytical predictions are in an excellent agreement with experimental observations both mechanically and electrically. This study provides insightful guidelines for designing PVEH devices to reliably generate electric power under nonstationary random vibrations.
The VariLift® Interbody Fusion System: expandable, standalone interbody fusion
Directory of Open Access Journals (Sweden)
Emstad E
2015-05-01
Full Text Available Erik Emstad,1 Diana Cardenas del Monaco,1 Louis C Fielding,2 Jon E Block2 1Wenzel Spine, Inc., Austin, TX, 2The Jon Block Group, San Francisco, CA, USA Abstract: Intervertebral fusion cages have been in clinical use since the 1990s. Cages offer the benefits of bone graft containment, restored intervertebral and foraminal height, and a more repeatable, stable procedure compared to interbody fusion with graft material alone. Due to concerns regarding postoperative stability, loss of lordosis, and subsidence or migration of the implant, interbody cages are commonly used with supplemental fixation such as pedicle screw systems or anterior plates. While providing additional stability, supplemental fixation techniques increase operative time, exposure, cost, and morbidity. The VariLift® Interbody Fusion System (VariLift® system has been developed as a standalone solution to provide the benefits of intervertebral fusion cages without the requirement of supplemental fixation. The VariLift® system, FDA-cleared for standalone use in both the cervical and lumbar spine, is implanted in a minimal profile and then expanded in situ to provide segmental stability, restored lordosis, and a large graft chamber. Preclinical testing and analyses have found that the VariLift® System is durable, and reduces stresses that may contribute to subsidence and migration of other standalone interbody cages. Fifteen years of clinical development with the VariLift® system have demonstrated positive clinical outcomes, continued patient maintenance of segmental stability and lordosis, and no evidence of implant migration. The purpose of this report is to describe the VariLift® system, including implant characteristics, principles of operation, indications for use, patient selection criteria, surgical technique, postoperative care, preclinical testing, and clinical experience. The VariLift® System represents an improved surgical option for a stable interbody fusion without
Vector-field statistics for the analysis of time varying clinical gait data.
Donnelly, C J; Alexander, C; Pataky, T C; Stannage, K; Reid, S; Robinson, M A
2017-01-01
In clinical settings, the time varying analysis of gait data relies heavily on the experience of the individual(s) assessing these biological signals. Though three dimensional kinematics are recognised as time varying waveforms (1D), exploratory statistical analysis of these data are commonly carried out with multiple discrete or 0D dependent variables. In the absence of an a priori 0D hypothesis, clinicians are at risk of making type I and II errors in their analyis of time varying gait signatures in the event statistics are used in concert with prefered subjective clinical assesment methods. The aim of this communication was to determine if vector field waveform statistics were capable of providing quantitative corroboration to practically significant differences in time varying gait signatures as determined by two clinically trained gait experts. The case study was a left hemiplegic Cerebral Palsy (GMFCS I) gait patient following a botulinum toxin (BoNT-A) injection to their left gastrocnemius muscle. When comparing subjective clinical gait assessments between two testers, they were in agreement with each other for 61% of the joint degrees of freedom and phases of motion analysed. For tester 1 and tester 2, they were in agreement with the vector-field analysis for 78% and 53% of the kinematic variables analysed. When the subjective analyses of tester 1 and tester 2 were pooled together and then compared to the vector-field analysis, they were in agreement for 83% of the time varying kinematic variables analysed. These outcomes demonstrate that in principle, vector-field statistics corroborates with what a team of clinical gait experts would classify as practically meaningful pre- versus post time varying kinematic differences. The potential for vector-field statistics to be used as a useful clinical tool for the objective analysis of time varying clinical gait data is established. Future research is recommended to assess the usefulness of vector-field analyses
Opinion formation in time-varying social networks: The case of Naming Game
Maity, Suman Kalyan; Mukherjee, Animesh
2012-01-01
We study the dynamics of the Naming Game as an opinion formation model on time-varying social networks. This agent-based model captures the essential features of the agreement dynamics by means of a memory-based negotiation process. Our study focuses on the impact of time-varying properties of the social network of the agents on the Naming Game dynamics. We investigate the outcomes of the dynamics on two different types of time-varying data - (i) the networks vary across days and (ii) the networks vary within very short intervals of time (20 seconds). In the first case, we find that networks with strong community structure hinder the system from reaching global agreement; the evolution of the Naming Game in these networks maintains clusters of coexisting opinions indefinitely leading to metastability. In the second case, we investigate the evolution of the Naming Game in perfect synchronization with the time evolution of the underlying social network shedding new light on the traditional emergent properties o...
Directory of Open Access Journals (Sweden)
Naradasu Kumar Ravi
2013-01-01
Full Text Available Diesel engine designers are constantly on the look-out for performance enhancement through efficient control of operating parameters. In this paper, the concept of an intelligent engine control system is proposed that seeks to ensure optimized performance under varying operating conditions. The concept is based on arriving at the optimum engine operating parameters to ensure the desired output in terms of efficiency. In addition, a Support Vector Machines based prediction model has been developed to predict the engine performance under varying operating conditions. Experiments were carried out at varying loads, compression ratios and amounts of exhaust gas recirculation using a variable compression ratio diesel engine for data acquisition. It was observed that the SVM model was able to predict the engine performance accurately.
Urbanek, Jacek; Barszcz, Tomasz; Strączkiewicz, Marcin; Jablonski, Adam
2017-01-01
The paper presents a normalization dedicated to transform non-stationary vibration signals into signals characterized by purely stationary properties. For this purpose, a novel class of generalized periodic signals is defined followed by a proposition of a normalization technique, which takes advantage of available, instantaneous values of operational parameters. Within the paper, a well-known discrete-random separation (DRS) technique is recalled as an exemplary technique, which has been restricted to stationary signals so far. The authors present a step-by-step adoption of the DRS to non-stationary signals. The method is applied to simulated signal, test rig signal, and a vibration signal from industrial object. Additionally, for the purpose of synthesis of simulated signal, a new model of multi-component vibrations generated under varying regime is proposed. The presented method aims to expand existing solutions dealing with varying frequency to a more general solution dealing with independent, simultaneous varying frequency and amplitude of signal components.
Do Men Vary More than Women in Personality? A Study in 51 Cultures.
Borkenau, Peter; McCrae, Robert R; Terracciano, Antonio
2013-04-01
Do men vary more than women in personality? Evolutionary, genetic, and cultural arguments suggest that hypothesis. In this study we tested it using 12,156 college student raters from 51 cultures who described a person they knew well on the 3rd-person version of the Revised NEO Personality Inventory. In most cultures, male targets varied more than female targets, and ratings by female informants varied more than ratings by male informants, which may explain why higher variances for men are not found in self-reports. Variances were higher in more developed, and effects of target sex were stronger in more individualistic societies. It seems that individualistic cultures enable a less restricted expression of personality, resulting in larger variances and particularly so among men.
Administrative database code accuracy did not vary notably with changes in disease prevalence.
van Walraven, Carl; English, Shane; Austin, Peter C
2016-11-01
Previous mathematical analyses of diagnostic tests based on the categorization of a continuous measure have found that test sensitivity and specificity varies significantly by disease prevalence. This study determined if the accuracy of diagnostic codes varied by disease prevalence. We used data from two previous studies in which the true status of renal disease and primary subarachnoid hemorrhage, respectively, had been determined. In multiple stratified random samples from the two previous studies having varying disease prevalence, we measured the accuracy of diagnostic codes for each disease using sensitivity, specificity, and positive and negative predictive value. Diagnostic code sensitivity and specificity did not change notably within clinically sensible disease prevalence. In contrast, positive and negative predictive values changed significantly with disease prevalence. Disease prevalence had no important influence on the sensitivity and specificity of diagnostic codes in administrative databases. Copyright Â© 2016 Elsevier Inc. All rights reserved.
New Inference Procedures for Semiparametric Varying-Coefficient Partially Linear Cox Models
Directory of Open Access Journals (Sweden)
Yunbei Ma
2014-01-01
Full Text Available In biomedical research, one major objective is to identify risk factors and study their risk impacts, as this identification can help clinicians to both properly make a decision and increase efficiency of treatments and resource allocation. A two-step penalized-based procedure is proposed to select linear regression coefficients for linear components and to identify significant nonparametric varying-coefficient functions for semiparametric varying-coefficient partially linear Cox models. It is shown that the penalized-based resulting estimators of the linear regression coefficients are asymptotically normal and have oracle properties, and the resulting estimators of the varying-coefficient functions have optimal convergence rates. A simulation study and an empirical example are presented for illustration.
Adaptive Control for Nonlinear Systems with Time-Varying Control Gain
Directory of Open Access Journals (Sweden)
Alejandro Rincon
2012-01-01
Full Text Available We propose a scheme for nonlinear plants with time-varying control gain and time-varying plant coefficients, on the basis of a plant model consisting of a Brunovsky-type model with polynomials as approximators. We develop an adaptive robust control scheme for this plant, under the following assumptions: (i the plant terms involve time-varying but bounded coefficients, being its upper bound unknown; (ii the control gain is unknown, not necessarily bounded, and only its signum is known. To achieve robustness, we use a combination of robustifying control inputs and dead zone-type update laws. We apply this methodology to the speed control of a permanent magnet synchronous motor (PMSM, and we achieve proper tracking results.
From calls to communities: a model for time varying social networks
Laurent, Guillaume; Karsai, Márton
2015-01-01
Social interactions vary in time and appear to be driven by intrinsic mechanisms, which in turn shape the emerging structure of the social network. Large-scale empirical observations of social interaction structure have become possible only recently, and modelling their dynamics is an actual challenge. Here we propose a temporal network model which builds on the framework of activity-driven time-varying networks with memory. The model also integrates key mechanisms that drive the formation of social ties - social reinforcement, focal closure and cyclic closure, which have been shown to give rise to community structure and the global connectedness of the network. We compare the proposed model with a real-world time-varying network of mobile phone communication and show that they share several characteristics from heterogeneous degrees and weights to rich community structure. Further, the strong and weak ties that emerge from the model follow similar weight-topology correlations as real-world social networks, i...
Linear Impulsive Periodic System with Time-Varying Generating Operators on Banach Space
Directory of Open Access Journals (Sweden)
Wei W
2007-01-01
Full Text Available A class of the linear impulsive periodic system with time-varying generating operators on Banach space is considered. By constructing the impulsive evolution operator, the existence of -periodic -mild solution for homogeneous linear impulsive periodic system with time-varying generating operators is reduced to the existence of fixed point for a suitable operator. Further the alternative results on -periodic -mild solution for nonhomogeneous linear impulsive periodic system with time-varying generating operators are established and the relationship between the boundness of solution and the existence of -periodic -mild solution is shown. The impulsive periodic motion controllers that are robust to parameter drift are designed for a given periodic motion. An example given for demonstration.
Performance Optimizing Adaptive Control with Time-Varying Reference Model Modification
Nguyen, Nhan T.; Hashemi, Kelley E.
2017-01-01
This paper presents a new adaptive control approach that involves a performance optimization objective. The control synthesis involves the design of a performance optimizing adaptive controller from a subset of control inputs. The resulting effect of the performance optimizing adaptive controller is to modify the initial reference model into a time-varying reference model which satisfies the performance optimization requirement obtained from an optimal control problem. The time-varying reference model modification is accomplished by the real-time solutions of the time-varying Riccati and Sylvester equations coupled with the least-squares parameter estimation of the sensitivities of the performance metric. The effectiveness of the proposed method is demonstrated by an application of maneuver load alleviation control for a flexible aircraft.
A Survey on Gain-Scheduled Control and Filtering for Parameter-Varying Systems
Directory of Open Access Journals (Sweden)
Guoliang Wei
2014-01-01
Full Text Available This paper presents an overview of the recent developments in the gain-scheduled control and filtering problems for the parameter-varying systems. First of all, we recall several important algorithms suitable for gain-scheduling method including gain-scheduled proportional-integral derivative (PID control, H2, H∞ and mixed H2/H∞ gain-scheduling methods as well as fuzzy gain-scheduling techniques. Secondly, various important parameter-varying system models are reviewed, for which gain-scheduled control and filtering issues are usually dealt with. In particular, in view of the randomly occurring phenomena with time-varying probability distributions, some results of our recent work based on the probability-dependent gain-scheduling methods are reviewed. Furthermore, some latest progress in this area is discussed. Finally, conclusions are drawn and several potential future research directions are outlined.
Containment problem with time-varying formation and collision avoidance for multiagent systems
Directory of Open Access Journals (Sweden)
Jesús Santiaguillo-Salinas
2017-05-01
Full Text Available This article studies a time-varying version of the so-called containment problem with collision avoidance for multiagent systems. The proposed control strategy is decentralized, since agents have no global knowledge of the goal to achieve, knowing only the position and velocity of a subset of agents. This control strategy allows a subset of mobile agents (called leaders to track a prescribed trajectory while they achieve a time-varying formation. Simultaneously, another subset of mobile agents (called followers converge exponentially to the region bounded by the leaders. For the collision avoidance, we added a repulsive vector field of the unstable focus type to the time-varying containment control law. Formation graphs are used to represent interactions between agents. The results are presented for the front points of differential-drive mobile robots. The theoretical results are verified by numerical simulation. Additionally, an experimental case study is presented.
Visulization of Time-Varying Multiresolution Date Using Error-Based Temporal-Spatial Resuse
Energy Technology Data Exchange (ETDEWEB)
Nuber, C; LaMar, E; Hamann, B; Joy, K
2002-04-22
In this paper, we report results on exploration of two-dimensional (2D) time varying datasets. We extend the notion of multiresolution spatial data approximation of static datasets to spatio-temporal approximation of time-varying datasets. Time-varying datasets typically do not change ''uniformly,'' i.e., some spatial sub-domains can experience only little or no change for extended periods of time. In these sub-domains, we show that approximation error bounds can be met when using sub-domains from other time-steps effectively. We generate a more general approximation scheme where sub-domains may approximate congruent sub-domains from any other time steps. While this incurs an O(T2) overhead, where T is the total number of time-steps, we show significant reduction in data transmission. We also discuss ideas for improvements to reduce overhead.
Sanchez, B; Louarroudi, E; Jorge, E; Cinca, J; Bragos, R; Pintelon, R
2013-03-01
The bioimpedance measurement/identification of time-varying biological systems Z(ω, t) by means of electrical impedance spectroscopy (EIS) is still a challenge today. This paper presents a novel measurement and identification approach, the so-called parametric-in-time approach, valid for time-varying (bio-)impedance systems with a (quasi) periodic character. The technique is based on multisine EIS. Contrary to the widely used nonparametric-in-time strategy, the (bio-)impedance Z(ω, t) is assumed to be time-variant during the measurement interval. Therefore, time-varying spectral analysis tools are required. This new parametric-in-time measuring/identification technique has experimentally been validated through three independent sets of in situ measurements of in vivo myocardial impedance. We show that the time-varying myocardial impedance Z(ω, t) is dominantly periodically time varying (PTV), denoted as ZPTV(ω, t). From the temporal analysis of ZPTV(ω, t), we demonstrate that it is possible to decompose ZPTV(ω, t) into a(n) (in)finite sum of fundamental (bio-)impedance spectra, the so-called harmonic impedance spectra (HIS) Zk(ω)s with [Formula: see text]. This is similar to the well-known Fourier series of a periodic signal, but now understood at the level of a periodic system's frequency response. The HIS Zk(ω)s for [Formula: see text] actually summarize in the bi-frequency (ω, k) domain all the temporal in-cycle information about the periodic changes of Z(ω, t). For the particular case k = 0 (i.e. on the ω-axis), Z0(ω) reflects the mean in-cycle behavior of the time-varying bioimpedance. Finally, the HIS Zk(ω)s are directly identified from noisy current and voltage myocardium measurements at the multisine measurement frequencies (i.e. nonparametric-in-frequency).
Recovery and purification of nickel-63 from HFIR-irradiated targets
Energy Technology Data Exchange (ETDEWEB)
Williams, D.F.; O`Kelley, G.D.; Knauer, J.B.; Porter, C.E.; Wiggins, J.T.
1993-06-01
The production of large quantities of high-specific-activity {sup 63}Ni (>10 Ci/g) requires both a highly enriched {sup 62}Ni target and a long irradiation period at high neutron flux. Trace impurities in the nickel and associated target materials are also activated and account for a significant fraction of the discharged activity and essentially all of the gamma activity. While most of these undesirable activation products can be removed as chloride complexes during anion exchange, chromium, present at {sup 51}Cr, and scandium, present as {sup 46}Sc, are exceptions and require additional processing to achieve the desired purity. Optimized flowsheets are discussed based upon the current development and production experience.
Recovery and purification of nickel-63 from HFIR-irradiated targets
Energy Technology Data Exchange (ETDEWEB)
Williams, D.F.; O' Kelley, G.D.; Knauer, J.B.; Porter, C.E.; Wiggins, J.T.
1993-06-01
The production of large quantities of high-specific-activity [sup 63]Ni (>10 Ci/g) requires both a highly enriched [sup 62]Ni target and a long irradiation period at high neutron flux. Trace impurities in the nickel and associated target materials are also activated and account for a significant fraction of the discharged activity and essentially all of the gamma activity. While most of these undesirable activation products can be removed as chloride complexes during anion exchange, chromium, present at [sup 51]Cr, and scandium, present as [sup 46]Sc, are exceptions and require additional processing to achieve the desired purity. Optimized flowsheets are discussed based upon the current development and production experience.
Physics Analyses in the Design of the HFIR Cold Neutron Source
Energy Technology Data Exchange (ETDEWEB)
Bucholz, J.A.
1999-09-27
Physics analyses have been performed to characterize the performance of the cold neutron source to be installed in the High Flux Isotope Reactor at the Oak Ridge National Laboratory in the near future. This paper provides a description of the physics models developed, and the resulting analyses that have been performed to support the design of the cold source. These analyses have provided important parametric performance information, such as cold neutron brightness down the beam tube and the various component heat loads, that have been used to develop the reference cold source concept.
Microstructural analysis of ferritic-martensitic steels irradiated at low temperature in HFIR
Energy Technology Data Exchange (ETDEWEB)
Hashimoto, N.; Robertson, J.P.; Rowcliffe, A.F. [Oak Ridge National Lab., TN (United States); Wakai, E. [Japan Atomic Energy Research Inst. (Japan)
1998-09-01
Disk specimens of ferritic-martensitic steel, HT9 and F82H, irradiated to damage levels of {approximately}3 dpa at irradiation temperatures of either {approximately}90 C or {approximately}250 C have been investigated by using transmission electron microscopy. Before irradiation, tempered HT9 contained only M{sub 23}C{sub 6} carbide. Irradiation at 90 C and 250 C induced a dislocation loop density of 1 {times} 10{sup 22} m{sup {minus}3} and 8 {times} 10{sup 21} m{sup {minus}3}, respectively. in the HT9 irradiated at 250 C, a radiation-induced phase, tentatively identified as {alpha}{prime}, was observed with a number density of less than 1 {times} 10{sup 20} m{sup {minus}3}. On the other hand, the tempered F82H contained M{sub 23}C{sub 6} and a few MC carbides; irradiation at 250 C to 3 dpa caused minor changes in these precipitates and induced a dislocation loop density of 2 {times} 10{sup 22} m{sup {minus}3}. Difference in the radiation-induced phase and the loop microstructure may be related to differences in the post-yield deformation behavior of the two steels.
Irradiation performance of HTGR fuel rods in HFIR experiments HRB-11 and -12
Energy Technology Data Exchange (ETDEWEB)
Homan, F.J.; Tiegs, T.N.; Kania, M.J.; Long, E.L. Jr.; Thoms, K.R.; Robbins, J.M.; Wagner, P.
1980-06-01
Capsules HRB-11 and -12 were irradiated in support of development of weak-acid-resin-derived recycle fuel for the high-enriched uranium (HEU) fuel cycle for the HTGR. Fissil fuel particles with initial oxygen-to-metal ratios between 1.0 and 1.7 performed acceptably to full burnup for HEU fuel. Particles with ratios below 1.0 showed excessive chemical interaction between rare earth fission products and the SiC layer.
Bank insolvency risk and time-varying Z-score measures
Lepetit, Laetitia; Strobel, Frank
2013-01-01
International audience; We compare the di¤erent existing approaches to the construction of time-varying Z-score measures, plus an additional alternative one, using a panel of banks for the G20 group of countries covering the period 1992–2009. We examine which ways of estimating the moments used in these di¤erent ap-proaches best …t the data, using a simple root mean squared error criterion. Our results are supportive of our alternative time-varying Z-score measure: it uses mean and standard d...
Block Empirical Likelihood for Longitudinal Single-Index Varying-Coefficient Model
Directory of Open Access Journals (Sweden)
Yunquan Song
2013-01-01
Full Text Available In this paper, we consider a single-index varying-coefficient model with application to longitudinal data. In order to accommodate the within-group correlation, we apply the block empirical likelihood procedure to longitudinal single-index varying-coefficient model, and prove a nonparametric version of Wilks’ theorem which can be used to construct the block empirical likelihood confidence region with asymptotically correct coverage probability for the parametric component. In comparison with normal approximations, the proposed method does not require a consistent estimator for the asymptotic covariance matrix, making it easier to conduct inference for the model's parametric component. Simulations demonstrate how the proposed method works.
Time-varying long term memory in the European Union stock markets
Sensoy, Ahmet; Tabak, Benjamin M.
2015-10-01
This paper proposes a new efficiency index to model time-varying inefficiency in stock markets. We focus on European stock markets and show that they have different degrees of time-varying efficiency. We observe that the 2008 global financial crisis has an adverse effect on almost all EU stock markets. However, the Eurozone sovereign debt crisis has a significant adverse effect only on the markets in France, Spain and Greece. For the late members, joining EU does not have a uniform effect on stock market efficiency. Our results have important implications for policy makers, investors, risk managers and academics.
Long Memory of Financial Time Series and Hidden Markov Models with Time-Varying Parameters
DEFF Research Database (Denmark)
Nystrup, Peter; Madsen, Henrik; Lindström, Erik
2016-01-01
Hidden Markov models are often used to model daily returns and to infer the hidden state of financial markets. Previous studies have found that the estimated models change over time, but the implications of the time-varying behavior have not been thoroughly examined. This paper presents an adaptive...... to reproduce with a hidden Markov model. Capturing the time-varying behavior of the parameters also leads to improved one-step density forecasts. Finally, it is shown that the forecasting performance of the estimated models can be further improved using local smoothing to forecast the parameter variations....
Control of Magnetic Bearings for Rotor Unbalance With Plug-In Time-Varying Resonators.
Kang, Christopher; Tsao, Tsu-Chin
2016-01-01
Rotor unbalance, common phenomenon of rotational systems, manifests itself as a periodic disturbance synchronized with the rotor's angular velocity. In active magnetic bearing (AMB) systems, feedback control is required to stabilize the open-loop unstable electromagnetic levitation. Further, feedback action can be added to suppress the repeatable runout but maintain closed-loop stability. In this paper, a plug-in time-varying resonator is designed by inverting cascaded notch filters. This formulation allows flexibility in designing the internal model for appropriate disturbance rejection. The plug-in structure ensures that stability can be maintained for varying rotor speeds. Experimental results of an AMB-rotor system are presented.
Prediction of the eigenvectors for spatial multiplexing MIMO systems in time-varying channels
DEFF Research Database (Denmark)
Nguyen, Hung Tuan; Leus, Geert; Khaled, Nadia
2005-01-01
: In mobile communications, time varying channels make the available channel information out of date. Timely updating the channel state is an obvious solution to improve the system performance in a time varying channel. However, a better knowledge of the channel comes at the cost of a decrease...... in the system throughput. Thus, predicting the future channel conditions can improve not only the performance but also the throughput of many types of wireless systems. This is especially true for a wireless system where multiple antennas are applied at both link ends. In this paper we propose and evaluate...
Identification of time-varying nonlinear systems using differential evolution algorithm
DEFF Research Database (Denmark)
Perisic, Nevena; Green, Peter L; Worden, Keith
2013-01-01
, thus identification of time-varying systems with nonlinearities can be a very challenging task. In order to avoid conventional least squares and gradient identification methods which require uni-modal and double differentiable objective functions, this work proposes a modified differential evolution...... (DE) algorithm for the identification of time-varying systems. DE is an evolutionary optimisation method developed to perform direct search in a continuous space without requiring any derivative estimation. DE is modified so that the objective function changes with time to account for the continuing...
Magnetic Skyrmion Transport in a Nanotrack With Spatially Varying Damping and Non-adiabatic Torque
Zhang, Xichao; Xia, Jing; Zhao, G. P.; Liu, Xiaoxi; Zhou, Yan
2016-01-01
Reliable transport of magnetic skyrmions is required for any future skyrmion-based information processing devices. Here we present a micromagnetic study of the in-plane current-driven motion of a skyrmion in a ferromagnetic nanotrack with spatially sinusoidally varying Gilbert damping and/or non-adiabatic spin-transfer torque coefficients. It is found that the skyrmion moves in a sinusoidal pattern as a result of the spatially varying Gilbert damping and/or non-adiabatic spin-transfer torque ...
Notes on the compatibility of type Ia supernovae data and varying-G cosmology
Shojai, F.; Shojai, A.
2013-11-01
Observational data for type Ia supernovae shows that the expansion of the universe is accelerated. This accelerated expansion can be described by a cosmological constant or by dark energy models, like quintessence. An interesting question may be raised here. Is it possible to describe the accelerated expansion of the universe using varying-G cosmological models? Here we shall show that the price for having accelerated expansion in slow-varying-G models (in which the dynamical terms of G are ignored) is to have highly non-conserved matter, and also that it is in contradiction with other data.
Effect of varying sample geometry on the failure properties of Zircaloy-4
Energy Technology Data Exchange (ETDEWEB)
Rawers, J.C.; Sizemore, J.
1987-01-01
In this study, the sample size of three-point bend samples was varied and the change in failure properties measured. Sample width, sample thickness and notch depth of a ductile material, Zircaloy-4, were varied while stress intensity, crack-open-displacement and failure energy were determined. In all tests the material showed elastic-plastic behavior. Statistical analysis was used to determine mathematical relationships between the sample geometry and the various failure parameters. It was then shown that the theoretical relationships between failure parameters needed modification for elastic-plastic failures.
DEFF Research Database (Denmark)
Callot, Laurent; Kristensen, Johannes Tang
This paper studies vector autoregressive models with parsimoniously time-varying parameters. The parameters are assumed to follow parsimonious random walks, where parsimony stems from the assumption that increments to the parameters have a non-zero probability of being exactly equal to zero......, or parameters varying randomly.We characterize the finite sample properties of the Lasso by deriving upper bounds on the estimation and prediction errors that are valid with high probability, and provide asymptotic conditions under which these bounds tend to zero with probability tending to one.We also provide...
H∞ Control of Four-Wheel-Independent-Drive Electric Vehicles with Random Time-Varying Delays
Directory of Open Access Journals (Sweden)
Gang Qin
2015-01-01
Full Text Available The random time-varying delays would reduce control performance and even deteriorate the EV system. To deal with random time-varying delays and achieve a real-time steady-state response, considering randomness of delay and a rapid response, an H∞-based delay-tolerant linear quadratic regulator (LQR control method based on Taylor series expansion is proposed in this paper. The results of cosimulations with Simulink and CarSim demonstrate the effectiveness of the proposed controller through the control performance of yaw rate, sideslip angle, and the running track. Moreover, the results of comparison with the other controller illustrate the strength of explicitly.
A Distributed Algorithm for Economic Dispatch Over Time-Varying Directed Networks With Delays
Energy Technology Data Exchange (ETDEWEB)
Yang, Tao; Lu, Jie; Wu, Di; Wu, Junfeng; Shi, Guodong; Meng, Ziyang; Johansson, Karl Henrik
2017-06-01
In power system operation, economic dispatch problem (EDP) is designed to minimize the total generation cost while meeting the demand and satisfying generator capacity limits. This paper proposes an algorithm based on the gradient-push method to solve the EDP in a distributed manner over communication networks potentially with time-varying topologies and communication delays. It has been shown that the proposed method is guaranteed to solve the EDP if the time-varying directed communication network is uniformly jointly strongly connected. Moreover, the proposed algorithm is also able to handle arbitrarily large but bounded time delays on communication links. Numerical simulations are used to illustrate and validate the proposed algorithm.
Directory of Open Access Journals (Sweden)
J. Thipcha
2013-01-01
Full Text Available The global exponential stability for bidirectional associative memory neural networks with time-varying delays is studied. In our study, the lower and upper bounds of the activation functions are allowed to be either positive, negative, or zero. By constructing new and improved Lyapunov-Krasovskii functional and introducing free-weighting matrices, a new and improved delay-dependent exponential stability for BAM neural networks with time-varying delays is derived in the form of linear matrix inequality (LMI. Numerical examples are given to demonstrate that the derived condition is less conservative than some existing results given in the literature.
Canopy damage to conifer plantations within a large mixed-severity wildfire varies with stand age
Jonathan R. Thompson; Thomas A. Spies; Keith A. Olsen
2011-01-01
The 2002 Biscuit Fire burned at mixed-severities encompassing over 200,000 ha of publicly owned forestland, including more than 8300 ha of conifer plantations. We used pre- and post-fire digital aerial photography to examine how the level of canopy damage varied within these plantations in relation to topography, weather, vegetation-cover, and management history, with...
Spatially-varied erosion modeling using WEPP for timber harvested and burned hillslopes
Peter R. Robichaud; T. M. Monroe
1997-01-01
Spatially-varied hydrologic surface conditions exist on steep hillslopes after timber harvest operation and site preparation burning treatments. Site preparation burning creates low- and high-severity burn surface conditions or disturbances. In this study, a hillslope was divided into multiple combinations of surface conditions to determine how their spatial...
Wilson, Celia M.
2010-01-01
Research pertaining to the distortion of the squared canonical correlation coefficient has traditionally been limited to the effects of sampling error and associated correction formulas. The purpose of this study was to compare the degree of attenuation of the squared canonical correlation coefficient under varying conditions of score reliability.…
Incidental learning and memory for food varied in sweet taste in children
Laureati, M.; Pagliarini, E.; Mojet, J.; Köster, E.P.
2011-01-01
This experiment investigated incidental learning and memory in children (age 7–10 years) for three different foods (fruit juice, fruit purée and biscuit), varied in sweetness. Children (N = 286) were exposed to three target foods and 24 h later their incidental learning was tested for one of the
Efficient preconditioning of hphp-FEM matrix sequences with slowly-varying coefficients
DEFF Research Database (Denmark)
Gatto, P.; Hesthaven, J. S.; Christiansen, Rasmus Ellebæk
2017-01-01
previous numerical experiments and develop a preconditioner-update strategy that allows us handle matrix sequences arising from problems with slowly-varying coefficients. We investigate the performance of the preconditioner along with the update strategy in context of topology optimization of an acoustic...
Effects of Simultaneous Script Training on Use of Varied Mand Frames by Preschoolers with Autism
Sellers, Tyra P.; Kelley, Kristen; Higbee, Thomas S.; Wolfe, Katie
2016-01-01
Young children with autism may fail to mand using a range of frames (e.g., "I want," "May I have," "Please give me"). We examined the effects of simultaneous script training and script fading on acquisition and maintenance of varied mand frames with six preschool children with autism. For participants who did not…
Effects of varying degrees of surface strain anisotropies on endothelial cells
Sinha, Ravi; le Gac, Severine; Verdonschot, Nicolaas Jacobus Joseph; van den Berg, Albert; Koopman, Hubertus F.J.M.; Rouwkema, Jeroen
2016-01-01
Introduction: Cyclic strain is well known to affect cell behavior. It is also known that isotropic and anisotropic strain can affect cells differently[1]. While in-vivo cells experience varying degrees of anisotropy (d.o.a.), in-vitro anisotropic strain studies have mostly focused on uniaxial
Helbich, M; Griffith, D
2016-01-01
Real estate policies in urban areas require the recognition of spatial heterogeneity in housing prices to account for local settings. In response to the growing number of spatially varying coefficient models in housing applications, this study evaluated four models in terms of their spatial patterns
DEFF Research Database (Denmark)
Pittalà, Fabio; Msallem, Majdi; Hauske, Fabian N.
2012-01-01
We propose a non-weighted feed-forward equalization method with filter update by averaging channel estimations based on short CAZAC sequences. Three averaging methods are presented and tested by simulations in a time-varying 2×2 MIMO optical system....
Modeling the Time-Varying Nature of Student Exceptionality Classification on Achievement Growth
Nese, Joseph F. T.; Stevens, Joseph J.; Schulte, Ann C.; Tindal, Gerald; Elliott, Stephen N.
2017-01-01
Our purpose was to examine different approaches to modeling the time-varying nature of exceptionality classification. Using longitudinal data from one state's mathematics achievement test for 28,829 students in Grades 3 to 8, we describe the reclassification rate within special education and between general and special education, and compare four…
The time-varying shortest path problem with fuzzy transit costs and speedup
Directory of Open Access Journals (Sweden)
Rezapour Hassan
2016-08-01
Full Text Available In this paper, we focus on the time-varying shortest path problem, where the transit costs are fuzzy numbers. Moreover, we consider this problem in which the transit time can be shortened at a fuzzy speedup cost. Speedup may also be a better decision to find the shortest path from a source vertex to a specified vertex.
Effect of Varying Levels of Inclusion of Shea Nut ( Vitellaria paradoxa )
African Journals Online (AJOL)
Twenty (20) rabbit does aged between 4 – 5 months with average body weight of 1. 75 kg, were used to study the effect of feeding varying level of inclusion of shea nut meal (SNM) on the reproductive performance of doe rabbits. The does were randomly assigned into five groups comprising four rabbits each and were fed ...
Analytical Treatment of the Two-Body Problem with Slowly Varying ...
Indian Academy of Sciences (India)
Abstract. The present work is concerned with the two-body problem with varying mass in case of isotropic mass loss from both components of the binary systems. The law of mass variation used gives rise to a perturbed. Keplerian problem depending on two small parameters. The problem is treated analytically in the ...
A comparative study on the rate of bone decalcification at varying ...
African Journals Online (AJOL)
This study evaluates the rate of bone decalcification at varying temperatures, decalcification fluid and fluid concentrations. A decalcification methodology was adopted using modern household microwave oven to accelerate the decalcification rate of rabbit compact bone sample. Bone biopsy was obtained from a rabbit limb ...
A autonomia na adolescência: revisando conceitos, modelos e variáveis
Directory of Open Access Journals (Sweden)
Paola Vargas Barbosa
2013-12-01
Full Text Available A conquista da autonomia está descrita como uma importante tarefa desenvolvimental da adolescência. Todavia, a complexidade da temática dificulta a compreensão do que seja a autonomia, assim como a comparação dos resultados encontrados na literatura científica. Com o objetivo de descrever os principais conceitos, modelos teóricos e variáveis associadas à autonomia adolescente, realizou-se uma revisão sistemática das publicações brasileiras e internacionais. Selecionaram-se 46 artigos que tratassem da autonomia como capacidade pessoal. Foram classificados de acordo com: conceitos utilizados, amostra, instrumentos e variáveis associadas à autonomia. A análise revelou uma diversidade de conceitos e instrumentos para compreensão do fenômeno; a existência de um perfil de adolescente no qual se baseia grande parte das publicações; a associação desta habilidade a variáveis contextuais, de ajustamento e clima familiar. Percebeu-se a descrição da autonomia como complexa e marcada por variáveis contextuais. Uma discussão critica sobre a produção encontrada na área foi feita.
Trip, Sebastian; Buerger, Mathias; De Persis, Claudio
This paper studies the problem of frequency regulation in power grids under unknown and possible time-varying load changes, while minimizing the generation costs. We formulate this problem as an output agreement problem for distribution networks and address it using incremental passivity and
Micropropagation de deux variétés de papayer ( Carica papaya L.) à ...
African Journals Online (AJOL)
Micropropagation de deux variétés de papayer (Carica papaya L.) à l'IPR/ IFRA de Katibougou, Mali. Abdoulaye Sidibé, Maman Sani Ladan Harouna, Bakary Mamourou Traoré, Moussa Abdoulaye, Ousmane Niangaly ...
Multiscale response of ionic systems to a spatially varying electric field
DEFF Research Database (Denmark)
Hansen, Jesper Schmidt
2017-01-01
In this paper the response of ionic systems subjected to a spatially varying electric field is studied. Following the Nernst-Planck equation, two forces driving the mass flux are present, namely, the concentration gradient and the electric potential gradient. The mass flux due to the concentration...
Emotions in freely varying and mono-pitched vowels, acoustic and EGG analyses.
Waaramaa, Teija; Palo, Pertti; Kankare, Elina
2015-12-01
Vocal emotions are expressed either by speech or singing. The difference is that in singing the pitch is predetermined while in speech it may vary freely. It was of interest to study whether there were voice quality differences between freely varying and mono-pitched vowels expressed by professional actors. Given their profession, actors have to be able to express emotions both by speech and singing. Electroglottogram and acoustic analyses of emotional utterances embedded in expressions of freely varying vowels [a:], [i:], [u:] (96 samples) and mono-pitched protracted vowels (96 samples) were studied. Contact quotient (CQEGG) was calculated using 35%, 55%, and 80% threshold levels. Three different threshold levels were used in order to evaluate their effects on emotions. Genders were studied separately. The results suggested significant gender differences for CQEGG 80% threshold level. SPL, CQEGG, and F4 were used to convey emotions, but to a lesser degree, when F0 was predetermined. Moreover, females showed fewer significant variations than males. Both genders used more hypofunctional phonation type in mono-pitched utterances than in the expressions with freely varying pitch. The present material warrants further study of the interplay between CQEGG threshold levels and formant frequencies, and listening tests to investigate the perceptual value of the mono-pitched vowels in the communication of emotions.
Frequency variations of gravity waves interacting with a time-varying tide
Directory of Open Access Journals (Sweden)
C. M. Huang
2013-10-01
Full Text Available Using a nonlinear, 2-D time-dependent numerical model, we simulate the propagation of gravity waves (GWs in a time-varying tide. Our simulations show that when a GW packet propagates in a time-varying tidal-wind environment, not only its intrinsic frequency but also its ground-based frequency would change significantly. The tidal horizontal-wind acceleration dominates the GW frequency variation. Positive (negative accelerations induce frequency increases (decreases with time. More interestingly, tidal-wind acceleration near the critical layers always causes the GW frequency to increase, which may partially explain the observations that high-frequency GW components are more dominant in the middle and upper atmosphere than in the lower atmosphere. The combination of the increased ground-based frequency of propagating GWs in a time-varying tidal-wind field and the transient nature of the critical layer induced by a time-varying tidal zonal wind creates favorable conditions for GWs to penetrate their originally expected critical layers. Consequently, GWs have an impact on the background atmosphere at much higher altitudes than expected, which indicates that the dynamical effects of tidal–GW interactions are more complicated than usually taken into account by GW parameterizations in global models.
Effects of varying levels of dietary palm oil in concentrate rations on ...
African Journals Online (AJOL)
Twenty Red Sokoto bucks (average liveweight of 21.4±3.2 kg) were used to evaluate the effects of varying levels of palm oil (PO) in concentraterations on nutrients digestibility and nitrogen retention. Five iso-nitrogenous concentrate supplements (CP 160 g/kg concentrate) compounded with 0, 40, 80, 120 and 160 g palm ...
Artificial neural network modeling of DDGS flowability with varying process and storage parameters
Neural Network (NN) modeling techniques were used to predict flowability behavior in distillers dried grains with solubles (DDGS) prepared with varying CDS (10, 15, and 20%, wb), drying temperature (100, 200, and 300°C), cooling temperature (-12, 0, and 35°C) and cooling time (0 and 1 month) levels....
Perfect fluid Bianchi Type-I cosmological models with time varying G ...
Indian Academy of Sciences (India)
Bianchi Type-I cosmological models containing perfect fluid with time varying and have been presented. The solutions obtained represent an expansion scalar bearing a constant ratio to the anisotropy in the direction of space-like unit vector . Of the two models obtained, one has negative vacuum energy density, ...
A note on "Multicriteria adaptive paths in stochastic, time-varying networks"
DEFF Research Database (Denmark)
Pretolani, Daniele; Nielsen, Lars Relund; Andersen, Kim Allan
In a recent paper, Opasanon and Miller-Hooks study multicriteria adaptive paths in stochastic time-varying networks. They propose a label correcting algorithm for finding the full set of efficient strategies. In this note we show that their algorithm is not correct, since it is based on a property...
Hsu, Pi-Sui; Van Dyke, Margot; Smith, Thomas J.
2017-01-01
The purpose of this mixed-methods study was to explore the effect of varied gender groupings on argumentation skills among middle school students in Taiwan and the United States in a project-based learning environment that incorporated a graph-oriented computer-assisted application (GOCAA). A total of 43 students comprised the treatment condition…
Closed-loop Identification for Control of Linear Parameter Varying Systems
DEFF Research Database (Denmark)
Bendtsen, Jan Dimon; Trangbæk, Klaus
2014-01-01
This paper deals with system identification for control of linear parameter varying systems. In practical applications, it is often important to be able to identify small plant changes in an incremental manner without shutting down the system and/or disconnecting the controller; unfortunately, cl...
Thyroid responses to varying doses of oral iodized oil in school ...
African Journals Online (AJOL)
A longitudinal study was conducted during 1994 - 1996 among elementary school children aged 6-14 years in Awassa, South Ethiopia. The aim of the study was to compare the efficacy of varying doses of oral iodized oil (200mg and 400mg) on thyroid function. The study included clinical examination of goitre, biochemical ...
Simple reaction time to the onset of time-varying sounds.
Schlittenlacher, Josef; Ellermeier, Wolfgang
2015-10-01
Although auditory simple reaction time (RT) is usually defined as the time elapsing between the onset of a stimulus and a recorded reaction, a sound cannot be specified by a single point in time. Therefore, the present work investigates how the period of time immediately after onset affects RT. By varying the stimulus duration between 10 and 500 msec, this critical duration was determined to fall between 32 and 40 milliseconds for a 1-kHz pure tone at 70 dB SPL. In a second experiment, the role of the buildup was further investigated by varying the rise time and its shape. The increment in RT for extending the rise time by a factor of ten was about 7 to 8 msec. There was no statistically significant difference in RT between a Gaussian and linear rise shape. A third experiment varied the modulation frequency and point of onset of amplitude-modulated tones, producing onsets at different initial levels with differently rapid increase or decrease immediately afterwards. The results of all three experiments results were explained very well by a straightforward extension of the parallel grains model (Miller and Ulrich Cogn. Psychol. 46, 101-151, 2003), a probabilistic race model employing many parallel channels. The extension of the model to time-varying sounds made the activation of such a grain depend on intensity as a function of time rather than a constant level. A second approach by mechanisms known from loudness produced less accurate predictions.
Tiled Parallel Coordinates for the Visualization of Time-Varying Multichannel EEG Data
Caat, M. ten; Maurits, N.M.; Roerdink, J.B.T.M.
2005-01-01
The field of visualization assists data interpretation in many areas, but some types of data are not manageable by existing visualization techniques. This holds in particular for time-varying multichannel EEG data. No existing technique can simultaneously visualize information from all channels in
Marsicano, Richard T.; Morrison, Julie Q.; Moomaw, Sally C.; Fite, Nathan M.; Kluesener, Courtney M.
2015-01-01
The current study used a single-case design to examine two performance feedback conditions varying in intensity on the frequency of naturalistic math instruction in preschool classrooms during non-instructional times (transition, lunch, free play). Three Head Start teachers received professional development that combined information on four…
Smart panel with time-varying shunted piezoelectric patch absorbers for broadband vibration control
Casagrande, D.; Gardonio, P.; Zilletti, M.
2017-07-01
This paper presents a simulation study concerning the low and mid frequencies control of flexural vibration in a lightly damped thin plate equipped with five time-varying shunted piezoelectric patch absorbers. The panel is excited by a rain-on-the-roof broad frequency band stationary disturbance. The absorbers are composed by piezoelectric patches connected to time-varying RL shunt circuits. Discrete or continuous variations over time of the shunts are implemented in such a way as to either switch, between given values, or sweep, within certain ranges, the natural frequency and damping factor of the electro-mechanical absorbers to control either the resonant response of targeted flexural modes of the plate with natural frequency comprised between 30 Hz and 1 kHz or to control the resonant responses of all flexural modes with natural frequencies comprised between 30 Hz and 1 kHz. The proposed system is firstly presented; then, the vibration control effects produced by a single patch and by the array of five patches implementing the switching and sweeping shunts are investigated. Both time-varying operation modes produce significant vibration control effects, with reductions of the resonance peaks of the target resonances or target frequency band up to 12 dB. The piezoelectric patch absorbers with sweeping shunts offer an interesting practical solution since they are operated blindly, thus they do not require a system identification during installation and effectively work without on line tuning also on systems whose response may vary substantially in time.
Volitional components of consciousness vary across wakefulness, dreaming and lucid dreaming
Dresler, M.; Eibl, L.; Fischer, C.F.; Wehrle, R.; Spoormaker, V.I.; Steiger, A.; Czisch, M.; Pawlowski, M.
2014-01-01
Consciousness is a multifaceted concept; its different aspects vary across species, vigilance states, or health conditions. While basal aspects of consciousness like perceptions and emotions are present in many states and species, higher-order aspects like reflective or volitional capabilities seem
Ammonia volatilization from treatment lagoons varies widely with the total ammonia concentration, pH, temperature, suspended solids, atmospheric ammonia concentration above the water surface, and wind speed. Ammonia emissions were estimated with a process-based mechanistic model integrating ammonia ...
Debating Life on Mars: The Knowledge Integration Environment (KIE) in Varied School Settings.
Shear, Linda
Technology-enabled learning environments are beginning to come of age. Tools and frameworks are now available that have been shown to improve learning and are being deployed more widely in varied school settings. Teachers are now faced with the formidable challenge of integrating these promising new environments with the everyday context in which…
Optimal Consumption and Investment under Time-Varying Relative Risk Aversion
DEFF Research Database (Denmark)
Steffensen, Mogens
2011-01-01
We consider the continuous time consumption-investment problem originally formalized and solved by Merton in case of constant relative risk aversion. We present a complete solution for the case where relative risk aversion with respect to consumption varies with time, having in mind an investor...
The Effects of Varying Latencies in the Stimulus-Response Paradigm of Speech Therapy.
Irwin, Ruth Beckey; And Others
Effects of varying latencies upon articulatory productions in the stimulus-response paradigm were studied. Zero latency was compared to latency equal to stimuli and to latency with silent rehearsal of muscular movements. Thirty children with misarticulated /r/ from kindergarten, first, and second grades participated as subjects. Stimulus /ra/ was…
Wang, Limin; Shao, Cheng
2010-04-01
The issue of exponential stabilisation for a class of special time-varying delay switched systems resulting from actuator faults is considered in this article. The time-varying delay is assumed to belong to an interval and can be a slow or fast time-varying function. A hybrid state feedback strategy is redesigned to guarantee the system stable since the original controller is unavailable for some actuators failures. A class of switching laws incorporating the average dwell time method is proposed so that the special switched system with interval time-varying delay is exponentially stable. New delay-range-dependent stabilisation conditions using state feedback controllers are formulated in terms of linear matrix inequalities (LMIs) by choosing appropriate Lyapunov-Krasovskii functional without neglecting some useful knowledge on system states. Parameterised characterisations of the controllers are given in terms of the feasibility solutions to the LMIs. Two numeral examples are given to demonstrate the applicability and the effectiveness of the proposed method.
Nitrate-induced changes and effect of varying total nitrogen to total ...
African Journals Online (AJOL)
Microcosm experiments were conducted to assess nitrate-induced changes and the effect of varying the ratio of total nitrogen to total phosphorus (TN:TP) on the winter and late summer phytoplankton communities in Lake Chivero, Zimbabwe. In both winter and summer, nitrate addition altered species composition from a ...
Eigenfrequencies and eigenmodes of a beam with periodically continuously varying spatial properties
DEFF Research Database (Denmark)
Sorokin, Vladislav S.; Thomsen, Jon Juel
2015-01-01
A beam with periodically continuously varying spatial properties is analyzed. This structure is a generic model for various systems widely used in industry, e.g. risers, rotor blades, and similar. The aim is to reveal effects of periodic spatial modulation both on the beam eigenfrequencies and ei...
Prospective memory in schizophrenia: The impact of varying retrospective-memory load
Altgassen, A.M.; Kliegel, M.; Rendell, P.G.; Henry, J.D.; Zöllig, J.
2008-01-01
The present study investigated event-based prospective memory in individuals with schizophrenia (nn=n23) and healthy controls (nn=n23). The retrospective-memory load was varied to disentangle the relative contributions of the retrospective and prospective components on prospective-memory
Tracy S. Hawkins; Nathan M. Schiff; Theodor D. Leininger; Emile S Gardiner; Margaret S. Devall; Paul B. Hamel; A. Dan Wilson; Kristina F. Connor
2009-01-01
Forest Service, Southern Research Station, Stoneville, MS 38776). Growth and intraspecific competitive abilities of the dioecious Lindera melissifolia (Lauraceae) in varied flooding regimes. J. Torrey Bot. Soc. 136: 91â101. 2009.âThe contribution of sexual dimorphism to malebiased colony ratios observed in field populations of the federally...
Effects of inclusion of varying levels of three natural spices on the ...
African Journals Online (AJOL)
The results showed that the mineral content of cheese was enhanced by the various inclusion levels of bear berry, ginger and onion. The control consistently had lower values of Ca, PO4, Fe, Mg and Zn. However, organoleptic studies showed that addition of varying levels of bear berry, ginger and onion did not improve the ...
Liu, Qun; Jiang, Daqing; Shi, Ningzhong; Hayat, Tasawar; Alsaedi, Ahmed
2017-03-01
In this paper, we develop a mathematical model for a tuberculosis model with constant recruitment and varying total population size by incorporating stochastic perturbations. By constructing suitable stochastic Lyapunov functions, we establish sufficient conditions for the existence of an ergodic stationary distribution as well as extinction of the disease to the stochastic system.
Understanding the allocation of attention when faced with varying perceptual load in partial report
DEFF Research Database (Denmark)
Kyllingsbæk, Søren; Sy, Jocelyn L; Giesbrecht, Barry
2011-01-01
. Here we present data from two partial report experiments where we varied the number and discriminability of the task-irrelevant stimuli (Experiment 1) and perceptual load (Experiment 2). The TVA fitted the data of the two experiments well thus favoring the simple explanation with a single step...
Low-Complexity Block Turbo Equalization for OFDM Systems in Time-Varying Channels
Fang, K.; Rugini, L.; Leus, G.
2008-01-01
We propose low-complexity block turbo equalizers for orthogonal frequency-division multiplexing (OFDM) systems in time-varying channels. The presented work is based on a soft minimum mean-squared error (MMSE) block linear equalizer (BLE) that exploits the banded structure of the frequency-domain
Identifying time-varying channels with aid of pilots for MIMO-OFDM
Tang, Z.; Leus, G.J.T.
2011-01-01
In this paper, we consider pilot-aided channel estimation for orthogonal frequency division multiplexing (OFDM) systems with a multiple-input multiple-output setup. The channel is time varying due to Doppler effects and can be approximated by an oversampled complex exponential basis expansion model.
Effect of varying dietary fibre and energy levels in multi-fibre source ...
African Journals Online (AJOL)
On this note, this study was carried out to investigate the effect of varying levels of CF at 4, 8 and 12% and Metabolisable Energy (ME) levels of 2600, 2800 and 3000 ME (Kcal/Kg) in multi-fibre source-based diets maintained around calorie: protein ratio of 140:1 on the performance characteristics of broiler finishers during 5 ...
Dual Extended Kalman Filter for the Identification of Time-Varying Human Manual Control Behavior
Popovici, Alexandru; Zaal, Peter M. T.; Pool, Daan M.
2017-01-01
A Dual Extended Kalman Filter was implemented for the identification of time-varying human manual control behavior. Two filters that run concurrently were used, a state filter that estimates the equalization dynamics, and a parameter filter that estimates the neuromuscular parameters and time delay. Time-varying parameters were modeled as a random walk. The filter successfully estimated time-varying human control behavior in both simulated and experimental data. Simple guidelines are proposed for the tuning of the process and measurement covariance matrices and the initial parameter estimates. The tuning was performed on simulation data, and when applied on experimental data, only an increase in measurement process noise power was required in order for the filter to converge and estimate all parameters. A sensitivity analysis to initial parameter estimates showed that the filter is more sensitive to poor initial choices of neuromuscular parameters than equalization parameters, and bad choices for initial parameters can result in divergence, slow convergence, or parameter estimates that do not have a real physical interpretation. The promising results when applied to experimental data, together with its simple tuning and low dimension of the state-space, make the use of the Dual Extended Kalman Filter a viable option for identifying time-varying human control parameters in manual tracking tasks, which could be used in real-time human state monitoring and adaptive human-vehicle haptic interfaces.
Time-Varying Networks of Inter-Ictal Discharging Reveal Epileptogenic Zone
Directory of Open Access Journals (Sweden)
Luyan Zhang
2017-08-01
Full Text Available The neuronal synchronous discharging may cause an epileptic seizure. Currently, most of the studies conducted to investigate the mechanism of epilepsy are based on EEGs or functional magnetic resonance imaging (fMRI recorded during the ictal discharging or the resting-state, and few studies have probed into the dynamic patterns during the inter-ictal discharging that are much easier to record in clinical applications. Here, we propose a time-varying network analysis based on adaptive directed transfer function to uncover the dynamic brain network patterns during the inter-ictal discharging. In addition, an algorithm based on the time-varying outflow of information derived from the network analysis is developed to detect the epileptogenic zone. The analysis performed revealed the time-varying network patterns during different stages of inter-ictal discharging; the epileptogenic zone was activated prior to the discharge onset then worked as the source to propagate the activity to other brain regions. Consistence between the epileptogenic zones detected by our proposed approach and the actual epileptogenic zones proved that time-varying network analysis could not only reveal the underlying neural mechanism of epilepsy, but also function as a useful tool in detecting the epileptogenic zone based on the EEGs in the inter-ictal discharging.
DEFF Research Database (Denmark)
Bjerre, Troels; Hansen, Mads Fogtmann; Aznar, M.
2012-01-01
For deformable registration of computed tomography (CT) scans in image guided radiation therapy (IGRT) we apply Riemannian elasticity regularization. We explore the use of spatially varying elasticity parameters to encourage bone rigidity and local tissue volume change only in the gross tumor...
Prediction of oil expression by uniaxial compression using time-varying oilseed properties
DEFF Research Database (Denmark)
Bargale, P. C.; Wulfsohn, Dvoralai; Irudayaraj, J.
2000-01-01
A mathematical simulation of uniaxial compression of oilseeds for oil extraction was developed based upon combining Terzaghi's theory of consolidation for saturated soils with Darcy's law for unsaturated flow, while incorporating the time-varying nature of the coefficients of permeability...
A comparison of time-varying covariates in two smoking cessation interventions for cardiac patients
Prenger, Hendrikje Cornelia; Pieterse, Marcel E.; Braakman-Jansen, Louise Marie Antoinette; Bolman, Catherine; Ruitenbeek-Wiggers, L.; de Vries, H.
2013-01-01
The aim of the study was to explore the time-varying contribution of social cognitive determinants of smoking cessation following an intervention on cessation. Secondary analyses were performed on data from two comparable randomized controlled trials on brief smoking cessation interventions for
Relating Aspects of Motivation to Facets of Mathematical Competence Varying in Cognitive Demand
Gilbert, Melissa C.
2016-01-01
The author investigated the relationship between aspects of student motivation and performance on mathematical tasks varying in cognitive demand relevant to meeting the expectations of the Common Core State Standards for Mathematics (CCSS-M). A sample of 479 primarily Latino middle school students completed established survey measures of…
Time-Varying Dynamic Properties of Offshore Wind Turbines Evaluated by Modal Testing
DEFF Research Database (Denmark)
Damgaard, Mads; Andersen, J. K. F.; Ibsen, Lars Bo
2014-01-01
resonance of the wind turbine structure. In this paper, free vibration tests and a numerical Winkler type approach are used to evaluate the dynamic properties of a total of 30 offshore wind turbines located in the North Sea. Analyses indicate time-varying eigenfrequencies and damping ratios of the lowest...
The necessity for a time local dimension in systems with time-varying attractors
DEFF Research Database (Denmark)
Særmark, Knud H; Ashkenazy, Y; Levitan, J
1997-01-01
We show that a simple non-linear system for ordinary differential equations may possess a time-varying attractor dimension. This indicates that it is infeasible to characterize EEG and MEG time series with a single time global dimension. We suggest another measure for the description of non...
Gasim, Anwar A.
2012-01-01
Varying shapes of InGaN nanostructures were simultaneously formed on silicon epitaxially. The nanowires and nanomushrooms emit violet-blue light, and broad yellow-orange-red luminescence, respectively. The combination of which is promising for white light emission.
David N. Cole; Troy E. Hall
2008-01-01
We explore the extent to which visitor experiences and management preferences vary between the most heavily used places in wilderness and places that are less popular. We also contrast day and overnight users. The study was conducted in Forest Service administered wildernesses in Oregon and Washington using both on-site and mailback questionnaires. The on-site...
Kiuru, Noona; Nurmi, Jari-Erik; Aunola, Kaisa; Salmela-Aro, Katariina
2009-01-01
This study investigated whether the members of adolescents' peer groups are similar in terms of their school adjustment and whether this homogeneity varies according to peer group type and gender. A total of 1262 peer group members who had recently moved to post-comprehensive education filled in questionnaires measuring their academic achievement,…
Iodide Residues in Milk Vary between Iodine-Based Teat Disinfectants
French, Elizabeth A; Mukai, Motoko; Zurakowski, Michael; Rauch, Bradley; Gioia, Gloria; Hillebrandt, Joseph R; Henderson, Mark; Schukken, Ynte H; Hemling, Thomas C
Majority of iodine found in dairy milk comes from the diet and teat disinfection products used during milking process. The objective of this study was to evaluate the effects of 4 iodine-based teat dips on milk iodide concentrations varying in iodine level (0.25% vs. 0.5%, w/w), normal low viscosity
The control of self-propelled microjets inside a microchannel with time-varying flow rates
Khalil, I.S.M.; Magdanz, Veronika; Sanchez, Samuel; Schmidt, Oliver S.; Misra, Sarthak
We demonstrate the closed-loop motion control of self-propelled microjets inside a fluidic microchannel. The motion control of the microjets is achieved in hydrogen peroxide solution with time-varying flow rates, under the influence of the controlled magnetic fields and the self-propulsion force.
DEFF Research Database (Denmark)
Andersen, P.; Skjærbæk, P. S.; Kirkegaard, Poul Henning
with the smoothed quanties which have been obtained from SARCOF. The results show the usefulness of the technique for identification of a time varying civil engineering structure. It is found that all the techniques give reliable estiates of the frequencies of the two lowest modes and the first mode shape. Only...
Environmental trade-offs of pig production systems under varied operational efficiencies
DEFF Research Database (Denmark)
McAuliffe, G. A.; Takahashi, T; Mogensen, Lisbeth
2017-01-01
it is imperative to develop alternative systems that can provide the right balance between sustainability and food security. Using an original dataset from the Republic of Ireland, this paper examines the life-cycle environmental impacts of representative pig farms operating under varying production efficiencies...
Caffeine for Apnea of Prematurity trial: benefits may vary in subgroups
Davis, Peter G.; Schmidt, Barbara; Roberts, Robin S.; Doyle, Lex W.; Asztalos, Elizabeth; Haslam, Ross; Sinha, Sunil; Tin, Win; Schmidt, B.; D'Ilario, J.; Cairnie, J.; Dix, J.; Adams, B.; Faber, B.; Callanan, K.; Davis, N.; Duff, J.; Ford, G.; Golec, L.; Lacy, M.; Hohn, D.; Barnett, C.; Goodchildt, L.; Lontis, R.; Fraser, S.; Keng, J.; Saunders, K.; Opie, G.; Kelly, E.; Bairam, A.; Ferland, S.; Laperriere, L.; Bélanger, S.; St Amand, P.; Blayney, M.; Davis, D.; Frank, J.; Lemyre, L.; Solimano, A.; Singh, A.; Chalmers, M.; Ramsay, K.; Synnes, A.; Whitfield, M.; Rogers, M.; Tomlinson, J.; Offringa, M.; Nuytemans, D.; Vermeulen, E.; Kok, J.; van Wassenaer, A.; Arnon, S.; Chalaf, A.; Regev, R.; Netter, I.; Ohlsson, A.; Nesbitt, K.; O'Brien, K.; Hamilton, A. M.; Sankaran, K.; Morgan, S.; Proctor, P.; LaCorte, M.; LeBlanc, P.; Braithwaite, A.; Golan, A.; Barabi, T.; Goldstein, E.; Reynolds, G.; Dromgool, B.; Meskell, S.; McMillan, D.; Schaab, D.; Spellen, L.; Sauve, R.; Christianson, H.; Anseeuw-Deeks, D.; Alvaro, R.; Chiu, A.; Porter, C.; Turner, G.; Moddemann, D.; Granke, N.; Penner, K.; Mulder, T.; Ghys, A.; van der Hoeven, M.; Clarke, M.; Parfitt, J.; MacLean, H.; Nwaesei, C.; Kuhn, L.; Ryan, H.; Saunders, C.; Schulze, A.; Pudenz, P.; Muller, M.; Lagercrantz, H.; Bhiladvala, M.; Legneval, L.; Herlenius, E.; Matthew, D.; Amos, W.; Tulsiani, S.; Tan-Dy, C.; Turner, M.; Shinwell, E.; Levine, R.; Juster-Reicher, A.; Barrington, K.; Kokkotis, T.; Khairy, M.; Grier, P.; Vachon, J.; Tin, W.; Fritz, S.; Walti, H.; Royer, D.; Halliday, H.; Millar, D.; Berry, A.; Mayes, C.; Cummings, C.; Fahnenstich, H.; Philipp, K.; Tillmann, B.; Weber, P.; Canning, R.; Wariyar, U.; Embleton, N.; Bucher, H.-U.; Fauchere, J.-C.; Pfister, R.; Launoy, V.; Huppi, P.; Poets, C.; Urschitz-Duprat, P.; Davis, P.; Doyle, L. W.; Gent, M.; Fraser, W.; Hey, E.; Perlman, M.; Thorpe, K.; Gray, S.; Roberts, R. S.; Chambers, C.; Costantini, L.; McGean, L.; Scapinello, L.
2010-01-01
OBJECTIVE: To determine whether the benefits of caffeine vary in three subgroups of 2006 participants in the Caffeine for Apnea of Prematurity (CAP) trial. STUDY DESIGN: Post-hoc subgroup analyses were performed on the basis of: (1) indication for commencement of study drug: treat apnea, prevent
Feeding Practices of Mothers from Varied Income and Racial/Ethnic Groups
Worobey, John; Borrelli, Amanda; Espinosa, Carolina; Worobey, Harriet S.
2013-01-01
Objective: Relatively few investigators have explored the role of maternal control in describing the feeding behaviour of nonwhite parents of preschool-age children. The present study was conducted to examine if controlling feeding behaviours (i.e. restriction and pressuring) varied by income (middle vs. low) and race/ethnicity (white vs.…
Performance and phytate utilization of meat-type chickens fed varied ...
African Journals Online (AJOL)
This study focuses on the performance and phytate utilization of meat-type chickens fed varied levels of acidified diets. Anti-nutrients such as phytate can inhibit growth performance in chickens; hence the need to supplement additives such as feed grade acidifiers that enhance digestibility and feed utilization.
Dynamic coupling design for nonlinear output agreement and time-varying flow control
Buerger, Mathias; De Persis, Claudio
This paper studies the problem of output agreement in networks of nonlinear dynamical systems under time-varying disturbances, using dynamic diffusive couplings. Necessary conditions are derived for general networks of nonlinear systems, and these conditions are explicitly interpreted as conditions
Uni-directional waves over slowly varying bottom, part II: Deformation of travelling waves
Pudjaprasetya, S.R.; Pudjaprasetya, S.R.; van Groesen, Embrecht W.C.
1996-01-01
A new Korteweg-de Vries type of equation for uni-directional waves over slowly varying bottom has been derived in Part I. The equation retains the Hamiltonian structure of the underlying complete set of equations for surface waves. For flat bottom it reduces to the standard Korteweg-de Vries
The generalized harmonic potential theorem in the presence of a time-varying magnetic field.
Lai, Meng-Yun; Pan, Xiao-Yin
2016-10-17
We investigate the evolution of the many-body wave function of a quantum system with time-varying effective mass, confined by a harmonic potential with time-varying frequency in the presence of a uniform time-varying magnetic field, and perturbed by a time-dependent uniform electric field. It is found that the wave function is comprised of a phase factor times the solution to the unperturbed time-dependent Schrödinger equation with the latter being translated by a time-dependent value that satisfies the classical driven equation of motion. In other words, we generalize the harmonic potential theorem to the case when the effective mass, harmonic potential, and the external uniform magnetic field with arbitrary orientation are all time-varying. The results reduce to various special cases obtained in the literature, particulary to that of the harmonic potential theorem wave function when the effective mass and frequency are both static and the external magnetic field is absent.
The performance of broiler finisher birds fed varying levels of feather ...
African Journals Online (AJOL)
This study focused on the performance of broiler finisher birds fed varying levels of feather meal as replacement for soya bean meal. The cost of livestock feeds had been on an upward trend more especially in developing countries due to competition between man and livestock for feed ingredients such as grains root crops, ...
Frequency variations of gravity waves interacting with a time-varying tide
Energy Technology Data Exchange (ETDEWEB)
Huang, C.M.; Zhang, S.D.; Yi, F.; Huang, K.M.; Gan, Q.; Gong, Y. [Wuhan Univ., Hubei (China). School of Electronic Information; Ministry of Education, Wuhan, Hubei (China). Key Lab. of Geospace Environment and Geodesy; State Observatory for Atmospheric Remote Sensing, Wuhan, Hubei (China); Zhang, Y.H. [Nanjing Univ. of Information Science and Technology (China). College of Hydrometeorolgy
2013-11-01
Using a nonlinear, 2-D time-dependent numerical model, we simulate the propagation of gravity waves (GWs) in a time-varying tide. Our simulations show that when aGW packet propagates in a time-varying tidal-wind environment, not only its intrinsic frequency but also its ground-based frequency would change significantly. The tidal horizontal-wind acceleration dominates the GW frequency variation. Positive (negative) accelerations induce frequency increases (decreases) with time. More interestingly, tidal-wind acceleration near the critical layers always causes the GW frequency to increase, which may partially explain the observations that high-frequency GW components are more dominant in the middle and upper atmosphere than in the lower atmosphere. The combination of the increased ground-based frequency of propagating GWs in a time-varying tidal-wind field and the transient nature of the critical layer induced by a time-varying tidal zonal wind creates favorable conditions for GWs to penetrate their originally expected critical layers. Consequently, GWs have an impact on the background atmosphere at much higher altitudes than expected, which indicates that the dynamical effects of tidal-GW interactions are more complicated than usually taken into account by GW parameterizations in global models.
Varying Language Register According to Listener Needs in Speakers with Autism Spectrum Disorder
Volden, Joanne; Magill-Evans, Joyce; Goulden, Keith; Clarke, Margaret
2007-01-01
The ability to adjust language register, or style, according to listener needs was assessed in 38 high-functioning children and adolescents with ASD. Participants were asked to explain the process of going to a restaurant to a series of listeners who varied in linguistic competence. Results showed that participants with ASD spontaneously…
Robust and Fault-Tolerant Linear Parameter-Varying Control of Wind Turbines
DEFF Research Database (Denmark)
Sloth, Christoffer; Esbensen, Thomas; Stoustrup, Jakob
2011-01-01
a robust controller (RC). This controller is able to take into account model uncertainties in the aerodynamic model. The controllers are based on output feedback and are scheduled on an estimated wind speed to manage the parameter-varying nature of the model. Furthermore, the AFTC relies on information...
Effect of varying rates of Palm Bunch Ash on maize yield in a ...
African Journals Online (AJOL)
Field experiment was conducted to determine the effect of varying rates of palm bunch ash on the grain yield of maize (Zea mays). The experiment was laid out in a randomized complete block design (RCBD) with four treatments replicated three times. The treatments were 0, 100, 200 and 300kg Palm bunch ash/ha.
Model reference adaptive control for linear time varying and nonlinear systems
Abida, L.; Kaufman, H.
1982-01-01
Model reference adaptive control is applied to linear time varying systems and to nonlinear systems amenable to virtual linearization. Asymptotic stability is guaranteed even if the perfect model following conditions do not hold, provided that some sufficient conditions are satisfied. Simulations show the scheme to be capable of effectively controlling certain nonlinear systems.
Effect of diet of Varying Protein concentrations on the Activity of ...
African Journals Online (AJOL)
Alterations in protein diet have been reported to result in alterations in calcium homeostasis in the body. Ca2+Mg2+ATPase is an ubiquitous enzyme important in calcium homeostasis in the body. The effect of varying protein diet on the activities of Ca2+ pump across cell membranes is however yet to be fully elucidated.
Effects of varying levels of n-6:n-3 fatty acid ratio on plasma fatty acid ...
African Journals Online (AJOL)
This study investigated the effects of varying dietary levels of n-6:n-3 fatty acid ratio on plasma fatty acid composition and prostanoid synthesis in pregnant rats. Four groups consisting of seven rats per group of non pregnant rats were fed diets with either a very low n-6:n-3 ratio of 50% soybean oil (SBO): 50% cod liver oil ...
Reduction of time-varying nanotesla magnetic fields from electric power lines by twisting
Been, A.J.; Folkertsma, Gerrit Adriaan; Folkertsma, G.A.; Verputten, H.H.J.; Bolhuis, Thijs; Abelmann, Leon
2009-01-01
Time-varying magnetic fields generated by electrical power lines in the laboratory can disturb electron microscope imaging. Modern microscopes require these fields to be below 10 nT [2]. We calculated and measured magnetic fields from straight and twisted current-carrying wires, and show that
Paunonen, Matti
1993-01-01
A method for compensating for the effect of the varying travel time of a transmitted laser pulse to a satellite is described. The 'observed minus predicted' range differences then appear to be linear, which makes data screening or use in range gating more effective.
Smoothly varying in-plane stiffness heterogeneity evaluated under uniaxial tensile stress
J.M. Considine; F. Pierron; K.T. Turner; P. Lava; X. Tang
2017-01-01
Identification of spatially varying stiffness is a challenging, but important, research topic in the mechanics of materials and can provide the necessary information for material suitability, damage, and process control, especially for highâvalue applications. One homogeneous and 3 heterogeneous virtual field method (VFM) formulations were used to create a methodology...
Re-identification of persons in multi-camera surveillance under varying viewpoints and illumination
Bouma, H.; Borsboom, A.S.; Hollander, R.J.M. den; Landsmeer, S.H.; Worring, M.
2012-01-01
The capability to track individuals in CCTV cameras is important for surveillance and forensics alike. However, it is laborious to do over multiple cameras. Therefore, an automated system is desirable. In literature several methods have been proposed, but their robustness against varying viewpoints
Re-identification of persons in multicamera surveillance under varying viewpoints and illumination
Bouma, H.; Borsboom, S.; den Hollander, R.J.M.; Worring, M.
2012-01-01
The capability to track individuals in CCTV cameras is important for surveillance and forensics alike. However, it is laborious to do over multiple cameras. Therefore, an automated system is desirable. In literature several methods have been proposed, but their robustness against varying viewpoints
Mean square stability of uncertain stochastic BAM neural networks with interval time-varying delays.
Wu, Haixia; Liao, Xiaofeng; Feng, Wei; Guo, Songtao
2012-10-01
The robust asymptotic stability analysis for uncertain BAM neural networks with both interval time-varying delays and stochastic disturbances is considered. By using the stochastic analysis approach, employing some free-weighting matrices and introducing an appropriate type of Lyapunov functional which takes into account the ranges for delays, some new stability criteria are established to guarantee the delayed BAM neural networks to be robustly asymptotically stable in the mean square. Unlike the most existing mean square stability conditions for BAM neural networks, the supplementary requirements that the time derivatives of time-varying delays must be smaller than 1 are released and the lower bounds of time varying delays are not restricted to be 0. Furthermore, in the proposed scheme, the stability conditions are delay-range-dependent and rate-dependent/independent. As a result, the new criteria are applicable to both fast and slow time-varying delays. Three numerical examples are given to illustrate the effectiveness of the proposed criteria.
Analysis of nonlinear systems with time varying inputs and its application to gain scheduling
Directory of Open Access Journals (Sweden)
J.-T. Lim
1996-01-01
Full Text Available An analytical framework for analysis of a class of nonlinear systems with time varying inputs is presented. It is shown that the trajectories of the transformed nonlinear systems are uniformly bounded with an ultimate bound under certain conditions shown in this paper. The result obtained is useful for applications, in particular, analysis and design of gain scheduling.
DEFF Research Database (Denmark)
Tong, Tian; Sira, Daniel; Nielsen, Michael
2009-01-01
using switch-mode power amplifier aided by various linearization techniques can present a feasible way to achieve both high linearity and high power efficiency. In this paper two different implementations of the switch-mode power amplifier a re p resented for varying envelop applications: the RF pulse...
Piai, V.; Roelofs, A.P.A.; Roete, I.E.C.
2015-01-01
Previous dual-task studies examining the locus of semantic interference of distractor words in picture naming have obtained diverging results. In these studies, participants manually responded to tones and named pictures while ignoring distractor words (picture-word interference, PWI) with varying
A> L1-TV algorithm for robust perspective photometric stereo with spatially-varying lightings
DEFF Research Database (Denmark)
Quéau, Yvain; Lauze, Francois Bernard; Durou, Jean-Denis
2015-01-01
We tackle the problem of perspective 3D-reconstruction of Lambertian surfaces through photometric stereo, in the presence of outliers to Lambert's law, depth discontinuities, and unknown spatially-varying lightings. To this purpose, we introduce a robust $L^1$-TV variational formulation of the re...
Time-varying coefficient estimation in SURE models. Application to portfolio management
DEFF Research Database (Denmark)
Casas, Isabel; Ferreira, Eva; Orbe, Susan
This paper provides a detailed analysis of the asymptotic properties of a kernel estimator for a Seemingly Unrelated Regression Equations model with time-varying coefficients (tv-SURE) under very general conditions. Theoretical results together with a simulation study differentiates the cases for...
Physicochemical effects of varying fuel composition on knock characteristics of natural gas mixtures
Gersen, Sander; van Essen, Martijn; van Dijk, Gerco; Levinsky, Howard
2014-01-01
The physicochemical origins of how changes in fuel composition affect autoignition of the end gas, leading to engine knock, are analyzed for a natural gas engine. Experiments in a lean-burn, high-speed medium-BMEP gas engine are performed using a reference natural gas with systematically varied
Measuring the Impact of Varied Instructional Approaches in an Introductory Animal Science Course
Bolt, Brian Grady
2009-01-01
The objectives of this project were to: evaluate the impact of demographic descriptors (gender, class rank and final grade) on student's self perceived level of engagement in classroom activities; measure the impact of varying teaching styles on a student's likelihood of correctly answering a knowledge based question and: assessing the…
Eesti filmid olid Karlovy Vary festivalil publiku seas menukad / Andris Feldmanis
Feldmanis, Andris, 1982-
2007-01-01
Ilmar Raagi mängufilmi "Klass" näidati 42. Karlovy Vary rahvusvahelise filmifestivali võistlusprogrammis "East of the West" ja Asko Kase lühimängufilm "Zen läbi prügi" oli festivali kõrvalprogrammis "Forum of Independents"
Local inertial oscillations in the surface ocean generated by time-varying winds
Chen, Shengli; Polton, Jeff A.; Hu, Jianyu; Xing, Jiuxing
2015-12-01
A new relationship is presented to give a review study on the evolution of inertial oscillations in the surface ocean locally generated by time-varying wind stress. The inertial oscillation is expressed as the superposition of a previous oscillation and a newly generated oscillation, which depends upon the time-varying wind stress. This relationship is employed to investigate some idealized wind change events. For a wind series varying temporally with different rates, the induced inertial oscillation is dominated by the wind with the greatest variation. The resonant wind, which rotates anti-cyclonically at the local inertial frequency with time, produces maximal amplitude of inertial oscillations, which grows monotonically. For the wind rotating at non-inertial frequencies, the responses vary periodically, with wind injecting inertial energy when it is in phase with the currents, but removing inertial energy when it is out of phase. The wind rotating anti-cyclonically with time is much more favorable to generate inertial oscillations than the cyclonic rotating wind. The wind with a frequency closer to the inertial frequency generates stronger inertial oscillations. For a diurnal wind, the induced inertial oscillation is dependent on latitude and is most significant at 30 °. This relationship is also applied to examine idealized moving cyclones. The inertial oscillation is much stronger on the right-hand side of the cyclone path than on the left-hand side (in the northern hemisphere). This is due to the wind being anti-cyclonic with time on the right-hand side, but cyclonic on the other side. The inertial oscillation varies with the cyclone translation speed. The optimal translation speed generating the greatest inertial oscillations is 2 m/s at the latitude of 10 ° and gradually increases to 6 m/s at the latitude of 30 °.
Scale effects on spatially varying relationships between urban landscape patterns and water quality.
Sun, Yanwei; Guo, Qinghai; Liu, Jian; Wang, Run
2014-08-01
Scientific interpretation of the relationships between urban landscape patterns and water quality is important for sustainable urban planning and watershed environmental protection. This study applied the ordinary least squares regression model and the geographically weighted regression model to examine the spatially varying relationships between 12 explanatory variables (including three topographical factors, four land use parameters, and five landscape metrics) and 15 water quality indicators in watersheds of Yundang Lake, Maluan Bay, and Xinglin Bay with varying levels of urbanization in Xiamen City, China. A local and global investigation was carried out at the watershed-level, with 50 and 200 m riparian buffer scales. This study found that topographical features and landscape metrics are the dominant factors of water quality, while land uses are too weak to be considered as a strong influential factor on water quality. Such statistical results may be related with the characteristics of land use compositions in our study area. Water quality variations in the 50 m buffer were dominated by topographical variables. The impact of landscape metrics on water quality gradually strengthen with expanding buffer zones. The strongest relationships are obtained in entire watersheds, rather than in 50 and 200 m buffer zones. Spatially varying relationships and effective buffer zones were verified in this study. Spatially varying relationships between explanatory variables and water quality parameters are more diversified and complex in less urbanized areas than in highly urbanized areas. This study hypothesizes that all these varying relationships may be attributed to the heterogeneity of landscape patterns in different urban regions. Adjustment of landscape patterns in an entire watershed should be the key measure to successfully improving urban lake water quality.
Directory of Open Access Journals (Sweden)
Yao Huang
2017-05-01
Full Text Available Active movements are important in the rehabilitation training for patients with neurological motor disorders, while weight of upper limb impedes movements due to muscles weakness. The objective of this study is to develop a position-varying gravity compensation strategy for a cable-based rehabilitation robot. The control strategy can estimate real-time gravity torque according to position feedback. Then, the performance of this control strategy was compared with the other two kinds of gravity compensation strategies (i.e., without compensation and with fixed compensation during movements tracking. Seven healthy subjects were invited to conduct tracking tasks along four different directions (i.e., upward, forward, leftward, and rightward. The performance of movements with different compensation strategies was compared in terms of root mean square error (RMSE between target and actual moving trajectories, normalized jerk score (NJS, mean velocity ratio (MVR of main motion direction, and the activation of six muscles. The results showed that there were significant effects in control strategies in all four directions with the RMSE and NJS values in the following order: without compensation > fixed compensation > position-varying compensation and MVR values in the following order: without compensation < fixed compensation < position-varying compensation (p < 0.05. Comparing with movements without compensation in all four directions, the activation of muscles during movements with position-varying compensation showed significant reductions, except the activations of triceps and in forward and leftward movements, the activations of upper trapezius and middle parts of deltoid in upward movements and the activations of posterior parts of deltoid in all four directions (p < 0.05. Therefore, with position-varying gravity compensation, the upper limb cable-based rehabilitation robotic system might assist subjects to perform movements with higher quality and
Time-varying Concurrent Risk of Extreme Droughts and Heatwaves in California
Sarhadi, A.; Diffenbaugh, N. S.; Ausin, M. C.
2016-12-01
Anthropogenic global warming has changed the nature and the risk of extreme climate phenomena such as droughts and heatwaves. The concurrent of these nature-changing climatic extremes may result in intensifying undesirable consequences in terms of human health and destructive effects in water resources. The present study assesses the risk of concurrent extreme droughts and heatwaves under dynamic nonstationary conditions arising from climate change in California. For doing so, a generalized fully Bayesian time-varying multivariate risk framework is proposed evolving through time under dynamic human-induced environment. In this methodology, an extreme, Bayesian, dynamic copula (Gumbel) is developed to model the time-varying dependence structure between the two different climate extremes. The time-varying extreme marginals are previously modeled using a Generalized Extreme Value (GEV) distribution. Bayesian Markov Chain Monte Carlo (MCMC) inference is integrated to estimate parameters of the nonstationary marginals and copula using a Gibbs sampling method. Modelled marginals and copula are then used to develop a fully Bayesian, time-varying joint return period concept for the estimation of concurrent risk. Here we argue that climate change has increased the chance of concurrent droughts and heatwaves over decades in California. It is also demonstrated that a time-varying multivariate perspective should be incorporated to assess realistic concurrent risk of the extremes for water resources planning and management in a changing climate in this area. The proposed generalized methodology can be applied for other stochastic nature-changing compound climate extremes that are under the influence of climate change.
Huang, Yao; Yang, Qianqian; Chen, Ying; Song, Rong
2017-01-01
Active movements are important in the rehabilitation training for patients with neurological motor disorders, while weight of upper limb impedes movements due to muscles weakness. The objective of this study is to develop a position-varying gravity compensation strategy for a cable-based rehabilitation robot. The control strategy can estimate real-time gravity torque according to position feedback. Then, the performance of this control strategy was compared with the other two kinds of gravity compensation strategies (i.e., without compensation and with fixed compensation) during movements tracking. Seven healthy subjects were invited to conduct tracking tasks along four different directions (i.e., upward, forward, leftward, and rightward). The performance of movements with different compensation strategies was compared in terms of root mean square error (RMSE) between target and actual moving trajectories, normalized jerk score (NJS), mean velocity ratio (MVR) of main motion direction, and the activation of six muscles. The results showed that there were significant effects in control strategies in all four directions with the RMSE and NJS values in the following order: without compensation > fixed compensation > position-varying compensation and MVR values in the following order: without compensation < fixed compensation < position-varying compensation (p < 0.05). Comparing with movements without compensation in all four directions, the activation of muscles during movements with position-varying compensation showed significant reductions, except the activations of triceps and in forward and leftward movements, the activations of upper trapezius and middle parts of deltoid in upward movements and the activations of posterior parts of deltoid in all four directions (p < 0.05). Therefore, with position-varying gravity compensation, the upper limb cable-based rehabilitation robotic system might assist subjects to perform movements with higher quality and improve the
Almirall, Daniel; Griffin, Beth Ann; McCaffrey, Daniel F.; Ramchand, Rajeev; Yuen, Robert A.; Murphy, Susan A.
2014-01-01
This article considers the problem of examining time-varying causal effect moderation using observational, longitudinal data in which treatment, candidate moderators, and possible confounders are time varying. The structural nested mean model (SNMM) is used to specify the moderated time-varying causal effects of interest in a conditional mean model for a continuous response given time-varying treatments and moderators. We present an easy-to-use estimator of the SNMM that combines an existing regression-with-residuals (RR) approach with an inverse-probability-of-treatment weighting (IPTW) strategy. The RR approach has been shown to identify the moderated time-varying causal effects if the time-varying moderators are also the sole time-varying confounders. The proposed IPTW+RR approach provides estimators of the moderated time-varying causal effects in the SNMM in the presence of an additional, auxiliary set of known and measured time-varying confounders. We use a small simulation experiment to compare IPTW+RR versus the traditional regression approach and to compare small and large sample properties of asymptotic versus bootstrap estimators of the standard errors for the IPTW+RR approach. This article clarifies the distinction between time-varying moderators and time-varying confounders. We illustrate the methodology in a case study to assess if time-varying substance use moderates treatment effects on future substance use. PMID:23873437
Manivannan, R; Samidurai, R; Cao, Jinde; Alsaedi, Ahmed; Alsaadi, Fuad E
2017-03-01
This paper investigates the problems of exponential stability and dissipativity of generalized neural networks (GNNs) with time-varying delay signals. By constructing a novel Lyapunov-Krasovskii functionals (LKFs) with triple integral terms that contain more advantages of the state vectors of the neural networks, and the upper bound on the time-varying delay signals are formulated. We employ a new integral inequality technique (IIT), free-matrix-based (FMB) integral inequality approach, and Wirtinger double integral inequality (WDII) technique together with the reciprocally convex combination (RCC) approach to bound the time derivative of the LKFs. An improved exponential stability and strictly (Q,S,R)-γ-dissipative conditions of the addressed systems are represented by the linear matrix inequalities (LMIs). Finally, four interesting numerical examples are developed to verify the usefulness of the proposed method with a practical application to a biological network. Copyright © 2016 Elsevier Ltd. All rights reserved.
Computational issues of solving the 1D steady gradually varied flow equation
Directory of Open Access Journals (Sweden)
Artichowicz Wojciech
2014-09-01
Full Text Available In this paper a problem of multiple solutions of steady gradually varied flow equation in the form of the ordinary differential energy equation is discussed from the viewpoint of its numerical solution. Using the Lipschitz theorem dealing with the uniqueness of solution of an initial value problem for the ordinary differential equation it was shown that the steady gradually varied flow equation can have more than one solution. This fact implies that the nonlinear algebraic equation approximating the ordinary differential energy equation, which additionally coincides with the wellknown standard step method usually applied for computing of the flow profile, can have variable number of roots. Consequently, more than one alternative solution corresponding to the same initial condition can be provided. Using this property it is possible to compute the water flow profile passing through the critical stage.
Smyth, Imelda; Ojard, Greg; Santhosh, Unni; Ahmad, Jalees; Gowayed, Yasser
2015-03-01
Ceramic matrix composites (CMC's) are attractive materials for use in advanced turbine engines. Due to the nature of available processing techniques, however, the amount and distribution of porosity in CMC's can vary greatly. This can be particularly true in parts with complex geometries. It is therefore important to characterize the porosity with non-destructive techniques and understand its effect on properties. A series of CMC samples were fabricated with varying levels of porosity and analyzed with different NDE techniques. The results were categorized and analyzed with respect to ease of interpretation and degree to which they could be quantified and used in models to determine the effects of defects. The results were also correlated with microstructural examination and mechanical properties.
Canedo-Rodriguez, Adrian; Rodriguez, Jose Manuel; Alvarez-Santos, Victor; Iglesias, Roberto; Regueiro, Carlos V
2015-04-30
In wireless positioning systems, the transmitter's power is usually fixed. In this paper, we explore the use of varying transmission powers to increase the performance of a wireless localization system. To this extent, we have designed a robot positioning system based on wireless motes. Our motes use an inexpensive, low-power sub-1-GHz system-on-chip (CC1110) working in the 433-MHz ISM band. Our localization algorithm is based on a particle filter and infers the robot position by: (1) comparing the power received with the expected one; and (2) integrating the robot displacement. We demonstrate that the use of transmitters that vary their transmission power over time improves the performance of the wireless positioning system significantly, with respect to a system that uses fixed power transmitters. This opens the door for applications where the robot can localize itself actively by requesting the transmitters to change their power in real time.
Cortical Dipole Imaging for Multiple Signal Sources Considering Time-Varying Non-Uniform Noise
Hori, Junichi; Watanabe, Yoshiki
Cortical dipole imaging is one of the spatial enhancement techniques from the scalp electroencephalogram. We investigated the dipole imaging for multiple signal sources under time-varying non-uniform noise conditions. The effects of incorporating statistical information of noise into the spatiotemporal inverse filter were examined by computer simulations and experimental studies in three sphere volume conductor model. The parametric projection filter that incorporated with noise covariance was applied to the inverse problem of EEG measurements. The noise covariance matrix was estimated by applying independent component analysis to the scalp potentials. The spatial filter was expanded to apply to the time-varying non-uniform noise conditions such as eye blink artifact. Moreover, multiple dipole distributions were introduced to extract and to visualize individual signal sources. The proposed imaging technique was applied to human experimental data of visual evoked potentials. We obtained reasonable results that coincide to physiological knowledge.
Effective ergodicity breaking in an exclusion process with varying system length
Schultens, Christoph; Schadschneider, Andreas; Arita, Chikashi
2015-09-01
Stochastic processes of interacting particles in systems with varying length are relevant e.g. for several biological applications. We try to explore what kind of new physical effects one can expect in such systems. As an example, we extend the exclusive queueing process that can be viewed as a one-dimensional exclusion process with varying length, by introducing Langmuir kinetics. This process can be interpreted as an effective model for a queue that interacts with other queues by allowing incoming and leaving of customers in the bulk. We find surprising indications for breaking of ergodicity in a certain parameter regime, where the asymptotic growth behavior depends on the initial length. We show that a random walk with site-dependent hopping probabilities exhibits qualitatively the same behavior.
Modeling and Analysis of a Piezoelectric Energy Harvester with Varying Cross-Sectional Area
Directory of Open Access Journals (Sweden)
Maiara Rosa
2014-01-01
Full Text Available This paper reports on the modeling and on the experimental verification of electromechanically coupled beams with varying cross-sectional area for piezoelectric energy harvesting. The governing equations are formulated using the Rayleigh-Ritz method and Euler-Bernoulli assumptions. A load resistance is considered in the electrical domain for the estimate of the electric power output of each geometric configuration. The model is first verified against the analytical results for a rectangular bimorph with tip mass reported in the literature. The experimental verification of the model is also reported for a tapered bimorph cantilever with tip mass. The effects of varying cross-sectional area and tip mass on the electromechanical behavior of piezoelectric energy harvesters are also discussed. An issue related to the estimation of the optimal load resistance (that gives the maximum power output on beam shape optimization problems is also discussed.
Directory of Open Access Journals (Sweden)
Cheng Liu
2010-01-01
Full Text Available Time-varying coherence is a powerful tool for revealing functional dynamics between different regions in the brain. In this paper, we address ways of estimating evolutionary spectrum and coherence using the general Cohen's class distributions. We show that the intimate connection between the Cohen's class-based spectra and the evolutionary spectra defined on the locally stationary time series can be linked by the kernel functions of the Cohen's class distributions. The time-varying spectra and coherence are further generalized with the Stockwell transform, a multiscale time-frequency representation. The Stockwell measures can be studied in the framework of the Cohen's class distributions with a generalized frequency-dependent kernel function. A magnetoencephalography study using the Stockwell coherence reveals an interesting temporal interaction between contralateral and ipsilateral motor cortices under the multisource interference task.
Model-free adaptive fractional order control of stable linear time-varying systems.
Yakoub, Z; Amairi, M; Chetoui, M; Saidi, B; Aoun, M
2017-03-01
This paper presents a new model-free adaptive fractional order control approach for linear time-varying systems. An online algorithm is proposed to determine some frequency characteristics using a selective filtering and to design a fractional PID controller based on the numerical optimization of the frequency-domain criterion. When the system parameters are time-varying, the controller is updated to keep the same desired performances. The main advantage of the proposed approach is that the controller design depends only on the measured input and output signals of the process. The effectiveness of the proposed method is assessed through a numerical example. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.
Common Brain Structure Findings Across Children with Varied Reading Disability Profiles.
Eckert, Mark A; Vaden, Kenneth I; Maxwell, Amanda B; Cute, Stephanie L; Gebregziabher, Mulugeta; Berninger, Virginia W
2017-07-20
Dyslexia is a developmental disorder in reading that exhibits varied patterns of expression across children. Here we examined the degree to which different kinds of reading disabilities (defined as profiles or patterns of reading problems) contribute to brain morphology results in Jacobian determinant images that represent local brain shape and volume. A matched-pair brain morphometry approach was used to control for confounding from brain size and research site effects in this retrospective multi-site study of 134 children from eight different research sites. Parietal operculum, corona radiata, and internal capsule differences between cases and controls were consistently observed across children with evidence of classic dyslexia, specific comprehension deficit, and language learning disability. Thus, there can be common brain morphology findings across children with quite varied reading disability profiles that we hypothesize compound the developmental difficulties of children with unique reading disability profiles and reasons for their reading disability.
Active-Varying Sampling-Based Fault Detection Filter Design for Networked Control Systems
Directory of Open Access Journals (Sweden)
Yu-Long Wang
2014-01-01
Full Text Available This paper is concerned with fault detection filter design for continuous-time networked control systems considering packet dropouts and network-induced delays. The active-varying sampling period method is introduced to establish a new discretized model for the considered networked control systems. The mutually exclusive distribution characteristic of packet dropouts and network-induced delays is made full use of to derive less conservative fault detection filter design criteria. Compared with the fault detection filter design adopting a constant sampling period, the proposed active-varying sampling-based fault detection filter design can improve the sensitivity of the residual signal to faults and shorten the needed time for fault detection. The simulation results illustrate the merits and effectiveness of the proposed fault detection filter design.
Search for Varying Constants of Nature from Astronomical Observation of Molecules
Ubachs, Wim
2018-02-01
The status of searches for possible variation in the constants of nature from astronomical observation of molecules is reviewed, focusing on the dimensionless constant representing the proton-electron mass ratio μ =mp/me. The optical detection of H2 and CO molecules with large ground-based telescopes (as the ESO-VLT and the Keck telescopes), as well as the detection of H2 with the Cosmic Origins Spectrograph aboard the Hubble Space Telescope is discussed in the context of varying constants, and in connection to different theoretical scenarios. Radio astronomy provides an alternative search strategy bearing the advantage that molecules as NH3 (ammonia) and CH3OH (methanol) can be used, which are much more sensitive to a varying μ than diatomic molecules. Current constraints are |Δ μ /μ | Universe (both at 3σ statistical significance). Existing bottlenecks and prospects for future improvement with novel instrumentation are discussed.
Control of parabolic PDEs with time-varying spatial domain: Czochralski crystal growth process
Ng, James; Aksikas, Ilyasse; Dubljevic, Stevan
2013-09-01
This paper considers the optimal control problem for a class of convection-diffusion-reaction systems modelled by partial differential equations (PDEs) defined on time-varying spatial domains. The class of PDEs is characterised by the presence of a time-dependent convective-transport term which is associated with the time evolution of the spatial domain boundary. The functional analytic description of the PDE yields the representation of the initial and boundary value problem as a nonautonomous parabolic evolution equation on an appropriately defined infinite-dimensional function space. The properties of the time-varying evolution operator to guarantee existence and well posedness of the initial and boundary value problem are demonstrated which serves as the basis for the optimal control problem synthesis. An industrial application of the crystal temperature regulation problem for the Czochralski crystal growth process is considered and numerical simulation results are provided.
Canedo-Rodriguez, Adrian; Rodriguez, Jose Manuel; Alvarez-Santos, Victor; Iglesias, Roberto; Regueiro, Carlos V.
2015-01-01
In wireless positioning systems, the transmitter's power is usually fixed. In this paper, we explore the use of varying transmission powers to increase the performance of a wireless localization system. To this extent, we have designed a robot positioning system based on wireless motes. Our motes use an inexpensive, low-power sub-1-GHz system-on-chip (CC1110) working in the 433-MHz ISM band. Our localization algorithm is based on a particle filter and infers the robot position by: (1) comparing the power received with the expected one; and (2) integrating the robot displacement. We demonstrate that the use of transmitters that vary their transmission power over time improves the performance of the wireless positioning system significantly, with respect to a system that uses fixed power transmitters. This opens the door for applications where the robot can localize itself actively by requesting the transmitters to change their power in real time. PMID:25942641
Estimating time-varying conditional correlations between stock and foreign exchange markets
Tastan, Hüseyin
2006-02-01
This study explores the dynamic interaction between stock market returns and changes in nominal exchange rates. Many financial variables are known to exhibit fat tails and autoregressive variance structure. It is well-known that unconditional covariance and correlation coefficients also vary significantly over time and multivariate generalized autoregressive model (MGARCH) is able to capture the time-varying variance-covariance matrix for stock market returns and changes in exchange rates. The model is applied to daily Euro-Dollar exchange rates and two stock market indexes from the US economy: Dow-Jones Industrial Average Index and S&P500 Index. The news impact surfaces are also drawn based on the model estimates to see the effects of idiosyncratic shocks in respective markets.
A river water quality model for time varying BOD discharge concentration
Directory of Open Access Journals (Sweden)
Oppenheimer Seth F.
1999-01-01
Full Text Available We consider a model for biochemical oxygen demand (BOD in a semi-infinite river where the BOD is prescribed by a time varying function at the left endpoint. That is, we study the problem with a time varying boundary loading. We obtain the well-posedness for the model when the boundary loading is smooth in time. We also obtain various qualitative results such as ordering, positivity, and boundedness. Of greatest interest, we show that a periodic loading function admits a unique asymptotically attracting periodic solution. For non-smooth loading functions, we obtain weak solutions. Finally, for certain special cases, we show how to obtain explicit solutions in the form of infinite series.
Power quality improvement in highly varying loads using thyristor-switched capacitor
Energy Technology Data Exchange (ETDEWEB)
Poshtan, M. [Petroleum Inst., Abu Dhabi (United Arab Emirates). Dept. of Electrical Engineering; Mokhtari, H.; Esmaeili, A. [Sharif Univ. of Technology, Tehran (Iran, Islamic Republic of). Dept. of Electrical Engineering
2007-07-01
Ordinary contactor-based-capacitor (CBC) banks may not be able to response quickly enough in highly varying electrical loads such as welding machines or arc furnace loads. Thyristor-switched capacitor (TSC) banks are therefore used to compensate for reactive power of highly varying loads. In this paper, the performance of a TSC was compared to CBC banks. The 2 systems, were also compared in terms of energy saving in transmission systems. Simulations carried out using PSCAD/EMTDC software showed that there was a considerable difference in the performance of the 2 systems. The shortcomings of existing CBC systems include slow response of mechanical switching systems; problem of switching more than one bank into the system; and, voltage/current transients during on-off switching. 3 refs., 6 tabs., 14 figs.
Dual-pump Kerr Micro-cavity Optical Frequency Comb with varying FSR spacing
Wang, Weiqiang; Chu, Sai T.; Little, Brent E.; Pasquazi, Alessia; Wang, Yishan; Wang, Leiran; Zhang, Wenfu; Wang, Lei; Hu, Xiaohong; Wang, Guoxi; Hu, Hui; Su, Yulong; Li, Feitao; Liu, Yuanshan; Zhao, Wei
2016-01-01
In this paper, we demonstrate a novel dual-pump approach to generate robust optical frequency comb with varying free spectral range (FSR) spacing in a CMOS-compatible high-Q micro-ring resonator (MRR). The frequency spacing of the comb can be tuned by an integer number FSR of the MRR freely in our dual-pump scheme. The dual pumps are self-oscillated in the laser cavity loop and their wavelengths can be tuned flexibly by programming the tunable filter embedded in the cavity. By tuning the pump wavelength, broadband OFC with the bandwidth of >180 nm and the frequency-spacing varying from 6 to 46-fold FSRs is realized at a low pump power. This approach could find potential and practical applications in many areas, such as optical metrology, optical communication, and signal processing systems, for its excellent flexibility and robustness. PMID:27338250
Directory of Open Access Journals (Sweden)
Alfaisal A. Hasan
2012-01-01
Full Text Available The Magnetohydrodynamic stability of a streaming cylindrical model penetrated by varying transverse magnetic field has been discussed. The problem is formulated, the basic equations are solved, upon appropriate boundary conditions the eigenvalue relation is derived and discussed analytically, and the results are verified numerically. The capillary force is destabilizing in a small axisymmetric domain 0<<1 and stabilizing otherwise. The streaming has a strong destabilizing effect in all kinds of perturbation. The toroidal varying magnetic field interior the fluid has no direct effect at all on the stability of the fluid column. The axial exterior field has strong stabilizing effect on the model. The effect of all acting forces altogether could be identified via the numerical analysis of the stability theory of the present model.
Robust Fusion Filtering for Multisensor Time-Varying Uncertain Systems: The Finite Horizon Case
Directory of Open Access Journals (Sweden)
Xiaoliang Feng
2016-01-01
Full Text Available The robust H∞ fusion filtering problem is considered for linear time-varying uncertain systems observed by multiple sensors. A performance index function for this problem is defined as an indefinite quadratic inequality which is solved by the projection method in Krein space. On this basis, a robust centralized finite horizon H∞ fusion filtering algorithm is proposed. However, this centralized fusion method is with poor real time property, as the number of sensors increases. To resolve this difficulty, within the sequential fusion framework, the performance index function is described as a set of quadratic inequalities including an indefinite quadratic inequality. And a sequential robust finite horizon H∞ fusion filtering algorithm is given by solving this quadratic inequality group. Finally, two simulation examples for time-varying/time-invariant multisensor systems are exploited to demonstrate the effectiveness of the proposed methods in the respect of the real time property and filtering accuracy.
Linear parameter-varying and time-delay systems analysis, observation, filtering & control
Briat, Corentin
2015-01-01
This book provides an introduction to the analysis and control of Linear Parameter-Varying Systems and Time-Delay Systems and their interactions. The purpose is to give the readers some fundamental theoretical background on these topics and to give more insights on the possible applications of these theories. This self-contained monograph is written in an accessible way for readers ranging from undergraduate/PhD students to engineers and researchers willing to know more about the fields of time-delay systems, parameter-varying systems, robust analysis, robust control, gain-scheduling techniques in the LPV fashion and LMI based approaches. The only prerequisites are basic knowledge in linear algebra, ordinary differential equations and (linear) dynamical systems. Most of the results are proved unless the proof is too complex or not necessary for a good understanding of the results. In the latter cases, suitable references are systematically provided. The first part pertains on the representation, analysis and ...
Comparative Genomics of Taphrina Fungi Causing Varying Degrees of Tumorous Deformity in Plants
Tsai, Isheng J.; Tanaka, Eiji; Masuya, Hayato; Tanaka, Ryusei; Hirooka, Yuuri; Endoh, Rikiya; Sahashi, Norio; Kikuchi, Taisei
2014-01-01
Taphrina fungi are biotrophic plant pathogens that cause plant deformity diseases. We sequenced the genomes of four Taphrina species—Taphrina wiesneri, T. deformans, T. flavorubra, and T. populina—which parasitize Prunus, Cerasus, and Populus hosts with varying severity of disease symptoms. High levels of gene synteny within Taphrina species were observed, and our comparative analysis further revealed that these fungi may utilize multiple strategies in coping with the host environment that are also found in some specialized dimorphic species. These include species-specific aneuploidy and clusters of highly diverged secreted proteins located at subtelomeres. We also identified species differences in plant hormone biosynthesis pathways, which may contribute to varying degree of disease symptoms. The genomes provide a rich resource for investigation into Taphrina biology and evolutionary studies across the basal ascomycetes clade. PMID:24682155
Optimum Design of Multi-Function Robot Arm Gripper for Varying Shape Green Product
Directory of Open Access Journals (Sweden)
Razali Zol Bahri
2016-01-01
Full Text Available The project focuses on thorough experimentally studies of the optimum design of Multi-function Robot Arm Gripper for varying shape green product. The purpose of this project is to design a few of robot arm gripper for multi-functionally grip a green product with varying shape. The main character of the gripper is that it can automated adjust its finger to suit with the shape of the product. An optimum design of multi-function robot arm gripper is verified through experimental study. The expected result is a series of analytical results on the proposal of gripper design and material that will be selected for the gripper. The analysis of the gripper design proposal by using ANSYS and CATIA software is described in detail in this paper.
LENUS (Irish Health Repository)
Hargrove, M
2008-07-01
Errors in blood flow delivery due to shunting have been reported to reduce flow by, potentially, up to 40-83% during cardiopulmonary bypass. The standard roller-pump measures revolutions per minute and a calibration factor for different tubing sizes calculates and displays flow accordingly. We compared displayed roller-pump flow with ultrasonically measured flow to ascertain if measured flow correlated with the heart-lung pump flow reading. Comparison of flows was measured under varying conditions of pump run duration, temperature, viscosity, varying arterial\\/venous loops, occlusiveness, outlet pressure, use of silicone or polyvinyl chloride (PVC) in the roller race, different tubing diameters, and use of a venous vacuum-drainage device.
Schaefer, Jacob; Hanson, Curt; Johnson, Marcus A.; Nguyen, Nhan
2011-01-01
Three model reference adaptive controllers (MRAC) with varying levels of complexity were evaluated on a high performance jet aircraft and compared along with a baseline nonlinear dynamic inversion controller. The handling qualities and performance of the controllers were examined during failure conditions that induce coupling between the pitch and roll axes. Results from flight tests showed with a roll to pitch input coupling failure, the handling qualities went from Level 2 with the baseline controller to Level 1 with the most complex MRAC tested. A failure scenario with the left stabilator frozen also showed improvement with the MRAC. Improvement in performance and handling qualities was generally seen as complexity was incrementally added; however, added complexity usually corresponds to increased verification and validation effort required for certification. The tradeoff between complexity and performance is thus important to a controls system designer when implementing an adaptive controller on an aircraft. This paper investigates this relation through flight testing of several controllers of vary complexity.