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Sample records for experimental field studies

  1. Experimental studies of sound field suppression at discrete frequencies

    NASA Astrophysics Data System (ADS)

    Fiks, I. Sh.; Korotin, P. I.; Potapov, O. A.; Fiks, G. E.

    2016-03-01

    Practical implementation of an active sound control system ensuring sound suppression in outer space is described as applied to sound insulation problems for equipment whose total noise level is mainly due to low-frequency discrete spectral components. The operational principle of the proposed system is based on inverse field generation with respect to the field of the initial source of quasi-monochromatic signals. The inverse field is formed by a set of radiators, which are controlled by the signals of pressure receivers positioned in the near field of the source. Experimental studies carried out with the proposed sound control system demonstrate its efficiency and testify to the stability of its operation.

  2. Experimental and Numerical Study of Free-Field Blast Mitigation

    NASA Astrophysics Data System (ADS)

    Allen, R. M.; Kirkpatrick, D. J.; Longbottom, A. W.; Milne, A. M.; Bourne, N. K.

    2004-07-01

    The development of a fundamental understanding of the mechanisms governing the attenuation of explosives effects by a surrounding mitigant material or system would benefit many civilian and military applications. Current approaches rely almost exclusively on empirical data, few if any truly predictive models exist. Dstl has recently pursued an experimental programme investigating the mitigation of effects from detonating explosives in support of general requirements to attenuate blast and fragmentation. The physical properties of a range of mitigant materials have been studied at a more fundamental level, both experimentally and numerically. A preliminary numerical parameter study has been undertaken by FGE using two-phase numerical simulations to complement the experimental studies. Initial work used idealised equations of state for generic mitigants but more recently material characterisation experiments have been undertaken at RMCS. Results confirm that porosity and particle density are dominant factors affecting the efficiency of the mitigant in reducing free-field blast.

  3. Experimental studies of plasma wake-field acceleration and focusing

    SciTech Connect

    Rosenzweig, J.B.; Cole, B.; Ho, C.; Gai, W.; Konecny, R.; Mtingwa, S.; Norem, J.; Rosing, M.; Schoessow, P.; Simpson, J.

    1989-07-18

    More than four years after the initial proposal of the Plasma Wake-field Accelerator (PWFA), it continues to be the object of much investigation, due to the promise of the ultra-high accelerating gradients that can exist in relativistic plasma waves driven in the wake of charged particle beams. These large amplitude plasma wake-fields are of interest in the laboratory, both for the wealth of basic nonlinear plasma wave phenomena which can be studied, as well as for the applications of acceleration of focusing of electrons and positrons in future linear colliders. Plasma wake-field waves are also of importance in nature, due to their possible role in direct cosmic ray acceleration. The purpose of the present work is to review the recent experimental advances made in PWFA research at Argonne National Laboratory, in which many interesting beam and plasma phenomena have been observed. Emphasis is given to discussion of the nonlinear aspects of the PWFA beam-plasma interaction. 29 refs., 13 figs.

  4. Review of Experimental Concepts for Studying the Quantum Vacuum Field

    SciTech Connect

    Davis, E. W.; Puthoff, H. E.; Teofilo, V. L.; Nickisch, L. J.; Rueda, A.; Cole, D. C.

    2006-01-20

    We review concepts that provide an experimental framework for exploring the possibility and limitations of accessing energy from the space vacuum environment. Quantum electrodynamics (QED) and stochastic electrodynamics (SED) are the theoretical approaches guiding this experimental investigation. This investigation explores the question of whether the quantum vacuum field contains useful energy that can be exploited for applications under the action of a catalyst, or cavity structure, so that energy conservation is not violated. This is similar to the same technical problem at about the same level of technology as that faced by early nuclear energy pioneers who searched for, and successfully discovered, the unique material structure that caused the release of nuclear energy via the neutron chain reaction.

  5. Feasibility Study for the Establishment of Experimental Field Study Centers (Beachhead Colleges). Final Report.

    ERIC Educational Resources Information Center

    Antioch Coll., Yellow Springs, OH.

    The Union for Research and Experimentation in Higher Education, a consortium of 10 colleges, initiated an experimental study of a new model for off-campus education in selected problematic areas. The model places students and faculty members in Field Study Centers-- or Beachhead Colleges --to help solve local problems through interaction between…

  6. An experimental field study of weight salience and food choice.

    PubMed

    Incollingo Rodriguez, Angela C; Finch, Laura E; Buss, Julia; Guardino, Christine M; Tomiyama, A Janet

    2015-06-01

    Laboratory research has found that individuals will consume more calories and make unhealthy food choices when in the presence of an overweight individual, sometimes even regardless of what that individual is eating. This study expanded these laboratory paradigms to the field to examine how weight salience influences eating in the real world. More specifically, we tested the threshold of the effect of weight salience of food choice to see if a more subtle weight cue (e.g., images) would be sufficient to affect food choice. Attendees (N = 262) at Obesity Week 2013, a weight-salient environment, viewed slideshows containing an image of an overweight individual, an image of a thin individual, or no image (text only), and then selected from complimentary snacks. Results of ordinal logistic regression analysis showed that participants who viewed the image of the overweight individual had higher odds of selecting the higher calorie snack compared to those who viewed the image of the thin individual (OR = 1.77, 95% CI = [1.04, 3.04]), or no image (OR = 2.42, 95% CI = [1.29, 4.54]). Perceiver BMI category did not moderate the influence of image on food choice, as these results occurred regardless of participant BMI. These findings suggest that in the context of societal weight salience, weight-related cues alone may promote unhealthy eating in the general public. PMID:25698080

  7. Experimental study of flow field around a plunging flexible hydrofoil

    NASA Astrophysics Data System (ADS)

    Martin-Alarcon, Leonardo; Yang, Tao; Shu, Fangjun; Wei, Mingjun

    2011-11-01

    Recent developments in micro air vehicles (MAVs) have led to the improvement of computational fluid dynamics (CFD) simulations capable of simulating flexible flapping wing phenomena. For validation of these simulations, an experimental methodology is applied to characterize the flow physics involved with an immersed flexible flapping hydrofoil. Using a one-degree of freedom crank-shaft system, a silicone hydrofoil was actuated to flap under various kinematic conditions. The hydrofoil was subject to active plunging and passive pitching motion in both water and aqueous glycerin solutions. Phase-locked particle image velocimetry (PIV) measurements were obtained around the flapping hydrofoil. These measurements, along with force measurements using a six-axis load cell, are used to compare the results with those of the numerical simulations. By comparing the hydrofoil deformation, vortex evolution and force generation, good agreements between CFD and experimental results were observed. Supported by Army High Performance Computing Research Center.

  8. Experimental studies on ion acceleration and stream line detachment in a diverging magnetic field

    PubMed Central

    Terasaka, K.; Yoshimura, S.; Ogiwara, K.; Aramaki, M.; Tanaka, M. Y.

    2010-01-01

    The flow structure of ions in a diverging magnetic field has been experimentally studied in an electron cyclotron resonance plasma. The flow velocity field of ions has been measured with directional Langmuir probes calibrated with the laser induced fluorescence spectroscopy. For low ion-temperature plasmas, it is concluded that the ion acceleration due to the axial electric field is important compared with that of gas dynamic effect. It has also been found that the detachment of ion stream line from the magnetic field line takes place when the parameter |fciLB∕Vi| becomes order unity, where fci, LB, and Vi are the ion cyclotron frequency, the characteristic scale length of magnetic field inhomogeneity, and the ion flow velocity, respectively. In the detachment region, a radial electric field is generated in the plasma and the ions move straight with the E×B rotation driven by the radial electric field. PMID:20838424

  9. Experimental Study of Magnetic Field Effect on dc Corona Discharge in Low Vacuum

    NASA Astrophysics Data System (ADS)

    Elabbas, K.

    2014-09-01

    In the present paper, an attempt was made to investigate the effect of applying a transverse magnetic field on the dc corona discharge behavior in low vacuum. In general, two experiments were carried out in this work: the first is the ionization-region magnetic field experiment, and the second was the drift region magnetic field experiment. In these experiments, permanent magnets were used to produce magnetic field. The degree of vacuum used in this test was 0.4×105 Pa. It is found that the effect of the magnetic field increases as the degree of vacuum increases. It is also seen from this study that the corona current values are higher with magnetic fields than without magnetic fields. The experimental results indicate that the enhancement of the magnetic field near the wire discharge electrode has a significant influence on the increment of the discharge current. The effect of the magnetic field on the discharge current is the most significant with the negative corona discharges rather than with positive corona discharge. In contrast to, the curves were demonstrated that the application of magnetic fields in drift region magnetic field does not significantly change the corona discharge current. Discharge characteristics of magnetically enhanced corona discharges, extracted from this study, can be applied to various industrial applications, such as, in an electrostatic enhancement filter for the purpose of capturing fine particles, and as effective method for production of high ozone concentrations in a generator as compared to the ultraviolet (UV) radiation method.

  10. Experimental studies of collective excitations of a BEC in light-induced gauge fields

    NASA Astrophysics Data System (ADS)

    Li, Chuan-Hsun; Niffenegger, Robert; Blasing, David; Olson, Abraham; Chen, Yong P.

    2015-05-01

    We present our experimental studies of collective modes including spin dipole mode and scissors mode of a 87Rb Bose-Einstein condensate (BEC) in the presence of Raman light-induced gauge fields and synthetic spin-orbit coupling (SOC). By Raman dressing the mf spin states within the F =1 manifold, we engineer atoms' energy-momentum dispersion to create synthetic SOC, and spin dependent synthetic electric and magnetic fields. We have used spin dependent synthetic electric fields to make two BECs with different spins oscillate and collide in the optical trap. We have studied the effects of SOC on both the momentum damping and thermalization behaviors of the BECs when undergoing such spin dipole oscillations. We have also used spatially dependent synthetic electric fields to excite the scissors mode, which has been used as a probe for superfluidity. We have investigated the effects of the synthetic gauge fields and SOC on the measured scissors mode.

  11. Argand-plane vorticity singularities in complex scalar optical fields: an experimental study using optical speckle.

    PubMed

    Rothschild, Freda; Bishop, Alexis I; Kitchen, Marcus J; Paganin, David M

    2014-03-24

    The Cornu spiral is, in essence, the image resulting from an Argand-plane map associated with monochromatic complex scalar plane waves diffracting from an infinite edge. Argand-plane maps can be useful in the analysis of more general optical fields. We experimentally study particular features of Argand-plane mappings known as "vorticity singularities" that are associated with mapping continuous single-valued complex scalar speckle fields to the Argand plane. Vorticity singularities possess a hierarchy of Argand-plane catastrophes including the fold, cusp and elliptic umbilic. We also confirm their connection to vortices in two-dimensional complex scalar waves. The study of vorticity singularities may also have implications for higher-dimensional fields such as coherence functions and multi-component fields such as vector and spinor fields. PMID:24663998

  12. Experimental studies of zonal flow and field in compact helical system plasma

    SciTech Connect

    Fujisawa, A.; Itoh, K.; Shimizu, A.; Nakano, H.; Ohshima, S.; Iguchi, H.; Matsuoka, K.; Okamura, S.; Minami, T.; Yoshimura, Y.; Nagaoka, K.; Ida, K.; Toi, K.; Takahashi, C.; Kojima, M.; Nishimura, S.; Isobe, M.; Suzuki, C.; Akiyama, T.; Ido, T.

    2008-05-15

    The experimental studies on zonal flows and turbulence have been carried out in Compact Helical System [K. Matsuoka, S. Kubo, M. Hosokawa et al., in Plasma Physics and Controlled Nuclear Fusion Research, Proc. 12th Int. Conf., Nice, 1988 (International Atomic Energy Agency, Vienna, 1989, Vol. 2, p. 411] using twin heavy ion beam probes. The paper presents the experimental observations of stationary zonal flow, nonlinear couplings between zonal flow and turbulence, and the role of zonal flow in the improved confinement, together with the recent discovery of zonal magnetic field. The presented experimental results strongly support the new paradigm that the plasma transport should be considered as a system of drift wave and zonal flows, and provides the first direct evidence for turbulence dynamo that the structured magnetic field can be really generated by turbulence.

  13. Experimental studies on remanence acquisition processes and regional geomagnetic field variability from archeointensity studies

    NASA Astrophysics Data System (ADS)

    Mitra, Ritayan

    The dissertation comprises two separate topics. Chapters 2 and 3 are experimental studies on remanence acquisition processes. Chapters 4 and 5 investigate the geomagnetic field variability in Africa and India between 1000 BCE and 1000 CE. Chapter 2 is a study in which the role of flocculation in sedimentary magnetization is analyzed with the help of laboratory redeposition experiments and a simple numerical model. At small floc sizes DRM acquisition is likely to be non-linear but it may record the directions with higher fidelity. In environments having bigger flocs the sediments are likely to record either intensities or directions with high fidelity, but not both. Also flocculation may inhibit a large fraction of magnetic grains from contributing to the net remanence and this might have consequences for intensity normalization in sediments. Chapter 3 presents a fresh perspective on the long standing debate of the nature of magnetocrystalline anisotropy in Mid-Ocean Ridge Basalts (MORBs). A new parameter, IRAT, defined as the ratio of the isothermal remanences in antiparallel directions is used to differentiate between uniaxial single domain grains (IRAT ˜1) and multiaxial single domain grains (IRAT<1). The theoretical predictions were first validated with standard samples and then multiple MORB samples were analyzed. The observed IRAT ratios indicate a dominant non-uniaxial anisotropy in the MORBs. Chapters 4 and 5 are archeointensity studies from two data poor regions of the world viz., Africa and India. With stringent data selection criteria and well established archeological constraints these datasets provide important constraints on the field intensity from 1000 BCE to 1000 CE in Africa and 500 BCE to 1000 CE in India. The African dataset has a higher age resolution than the Indian dataset. The African dataset matches well with the global CALS3k.4 model and shows significant non-axial-dipolar contribution in the region. The Indian dataset is not of a similar

  14. Experimental study of the formation of field-reversed configurations employing high-order multipole fields

    NASA Astrophysics Data System (ADS)

    Slough, J. T.; Hoffman, A. L.

    1990-04-01

    A high-order multipole ``barrier'' field was applied at the vacuum tube wall in the TRX experiment [Phys. Fluids B 1, 840 (1989)] during both the preionization and field reversal phases of field-reversed configuration (FRC) formation. Use of this field during field reversal resulted in a significant reduction of impurities as well as increased flux trapping. With a large enough Bθ at the wall, sheath detachment from the wall became apparent, and flux loss through the sheath became negligible (<10%). At larger wall Bθ (>1.5 kG), destructive rotational spin-up occurred, driven by Hall current forces. When the multipole barrier field was also applied during either axial discharge or ringing theta current preionization, a very symmetric and uniform breakdown of the fill gas was achieved. In particular, using ringing theta preionization, complete ionization of the fill gas was accomplished with purely inductive fields of remarkably low magnitude, where Ez≤3 V/cm, and Eθ≤20 V/cm. Due to the improved ionization symmetry, about 65% to 75% of the lift-off flux (flux remaining after field reversal) could be retained through the remaining formation processes into an equilibrium FRC. Using the multipole field during both preionization and formation, it was possible to form FRC's with good confinement with greater than 3 mWb of trapped flux at 15 mTorr D2 or H2 in a 10 cm radius device. Values of s in excess of 4 could be achieved in this manner.

  15. Experimental studies of far-field superlens for sub-diffractional optical imaging

    NASA Astrophysics Data System (ADS)

    Liu, Zhaowei; Durant, Stéphane; Lee, Hyesog; Pikus, Yuri; Xiong, Yi; Sun, Cheng; Zhang, Xiang

    2007-05-01

    Contrary to the conventional near-field superlensing, subwavelength superlens imaging is experimentally demonstrated in the far-field. The key element is termed as a Far-field SuperLens (FSL) which consists of a conventional superlens and a nanoscale coupler. The evanescent fields from the object are enhanced and then converted into propagating fields by the FSL. By only measuring the propagating field in the far-field, the object image can be reconstructed with subwavelength resolution. As an example of this concept, we design and fabricate a silver structured one dimensional FSL. Experimental results show that feature resolution of better than 50nm is possible using current FSL design.

  16. Combining experimental evolution and field population assays to study the evolution of host range breadth.

    PubMed

    Fellous, S; Angot, G; Orsucci, M; Migeon, A; Auger, P; Olivieri, I; Navajas, M

    2014-05-01

    Adapting to specific hosts often involves trade-offs that limit performance on other hosts. These constraints may either lead to narrow host ranges (i.e. specialists, able to exploit only one host type) or wide host ranges often leading to lower performance on each host (i.e. generalists). Here, we combined laboratory experiments on field populations with experimental evolution to investigate the impact of adaptation to the host on host range evolution and associated performance over this range. We used the two-spotted spider mite, Tetranychus urticae, a model organism for studies on the evolution of specialization. Field mite populations were sampled on three host plant species: tomato, citrus tree and rosebay (Nerium oleander). Testing these populations in the laboratory revealed that tomato populations of mites could exploit tomato only, citrus populations could exploit citrus and tomato whereas Nerium populations could exploit all three hosts. Besides, the wider niche ranges of citrus and Nerium populations came at the cost of low performance on their non-native hosts. Experimental lines selected to live on the same three host species exhibited similar patterns of host range and relative performance. This result suggests that adaptation to a new host species may lead to wider host ranges but at the expense of decreased performance on other hosts. We conclude that experimental evolution may reliably inform on evolution in the field. PMID:24689448

  17. Experimental and theoretical study on field emission properties of zinc oxide nanoparticles decorated carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Li, Xin; Zhou, Wei-Man; Liu, Wei-Hua; Wang, Xiao-Li

    2015-05-01

    Field emission properties of zinc oxide (ZnO) nanoparticles (NPs) decorated carbon nanotubes (CNTs) are investigated experimentally and theoretically. CNTs are in situ decorated with ZnO NPs during the growth process by chemical vapor deposition using a carbon source from the iron phthalocyanine pyrolysis. The experimental field emission test shows that the ZnO NP decoration significantly improves the emission current from 50 μA to 275 μA at 550 V and the reduced threshold voltage from 450 V to 350 V. The field emission mechanism of ZnO NPs on CNTs is theoretically studied by the density functional theory (DFT) combined with the Penn-Plummer method. The ZnO NPs reconstruct the ZnO-CNT structure and pull down the surface barrier of the entire emitter system to 0.49 eV so as to reduce the threshold electric field. The simulation results suggest that the presence of ZnO NPs would increase the LDOS near the Fermi level and increase the emission current. The calculation results are consistent with the experiment results. Project supported by the National Natural Science Foundation of China (Grant Nos. 91123018, 61172040, and 61172041) and the Natural Science Foundation of Shaanxi Province, China (Grant No. 2014JM7277).

  18. An Experimental Study of the Effects of A Rotating Magnetic Field on Electrically Conducting Aqueous Solutions

    NASA Technical Reports Server (NTRS)

    Ramachandran Narayanan; Mazuruk, Konstantin

    1998-01-01

    The use of a rotating magnetic field for stirring metallic melts has been a commonly adopted practice for a fairly long period. The elegance of the technique stems from its non-intrusive nature and the intense stirring it can produce in an electrically conducting medium. A further application of the method in recent times has been in the area of crystal growth from melts (e.g. germanium). The latter experiments have been mainly research oriented in order to understand the basic physics of the process and to establish norms for optimizing such a technique for the commercial production of crystals. When adapted for crystal growth applications, the rotating magnetic field is used to induce a slow flow or rotation in the melt which in effect significantly curtails temperature field oscillations in the melt. These oscillations are known to cause dopant striations and thereby inhomogeneities in the grown crystal that essentially degrades the crystal quality. The applied field strength is typically of the order of milli-Teslas with a frequency range between 50-400 Hz. In this investigation, we report findings from experiments that explore the feasibility of applying a rotating magnetic field to aqueous salt solutions, that are characterized by conductivities that are several orders of magnitude smaller than semi-conductor melts. The aim is to study the induced magnetic field and consequently the induced flow in such in application. Detailed flow field description obtained through non-intrusive particle displacement tracking will be reported along with an analytical assessment of the results. It is anticipated that the obtained results will facilitate in establishing a parameter range over which the technique can be applied to obtain a desired flow field distribution. This method can find applicability in the growth of crystals from aqueous solutions and give an experimenter another controllable parameter towards improving the quality of the grown crystal.

  19. Experimental Study of Soil Organic Matter Loss From Cultivated Field Plots In The Venezuelan Andes.

    NASA Astrophysics Data System (ADS)

    Bellanger, B.; Huon, S.; Velasquez, F.; Vallès, V.; Girardin A, C.; Mariotti, A. B.

    The question of discriminating sources of organic matter in suspended particles of stream flows can be addressed by using total organic carbon (TOC) concentration and stable isotope (13C, 15N) measurements when constant fluxes of organic matter supply can be assumed. However, little is known on the dynamics of organic matter release during soil erosion and on the temporal stability of its isotopic signature. In this study, we have monitored soil organic carbon loss and water runoff using natural rainfall events on three experimental field plots with different vegetation cover (bare soil, maize and coffee fields), set up on natural slopes of a tropical mountainous watershed in NW Venezuela (09°13'32'' ­ 09°10'00''N, 70°13'49'' ­ 70°18'34''W). Runoff and soil loss are markedly superior for the bare field plot than for the coffee field plot: by a factor 15 ­ 36, respectively, for the five-month experiment, and by a factor 30 ­ 120, respectively, during a single rainfall event experiment. Since runoff and soil organic matter loss are closely linked during most of the flow (at the time scales of this study), TOC concentration in suspended matter is constant. Furthermore, stable isotope compositions reflect those of top-soil organic matter from which they originate.

  20. Lignin fate in soils studied at the long-term experimental field of "Les Closeaux" (France)

    NASA Astrophysics Data System (ADS)

    Dignac, M.-F.; Thevenot, M.; Bahri, H.; Rasse, D. P.; Rumpel, C.

    2009-04-01

    Lignins are one of the most abundant plant molecules in soils and are considered as having a great impact on the soil organic matter (SOM) content and fate. However, the dynamics and turnover of lignins in soils are not clear on the long-term basis. Some studies suggest that lignins turnover could be faster than that of the bulk SOM (Lobe et al., 2002; Dignac et al., 2005), whereas other studies suggest the opposite (Hoffman et al., 2009). The lignin fate in soils and their role in the SOM dynamics require further elucidation. To this end, a long-term study based on a wheat-maize transition chronosequence was set up in 1993, at the "Les Closeaux" experimental field in Versailles (France). In this field the C3 to C4 vegetation change makes it possible to use stable isotopes to study bulk and molecular SOM turnover. The influence of maize cropping on lignin and SOM dynamics was studied using the CuO oxidation and chromatographic methods coupled with isotopic measurements. Based on this experimental setup and methodology, we calculated a lignin turnover of 47% over a 9-year period, when 9% of the bulk soil organic matter had turned over. Moreover, we showed (Bahri et al., 2006) that the turnover of lignins is monomer specific. A simple two-pool model calibrated on the lignin-specific 13C isotopic analyses was developed to quantify the lignin turnover rates (Rasse et al., 2006). The first results obtained suggest that only 8% of the lignins applied to the soil is retained, the mechanisms of stabilization being to be elucidated. The "Les Closeaux" experimental field has already furnished much information on lignin fate in soils and will be used in the future to elucidate further the processes of lignin degradation in soil. Bahri H., Dignac M.-F., Rumpel C., Rasse D.P., Chenu C., Mariotti A., 2006. Soil Biology & Biochemistry 38, 1977-1988. Dignac M.-F, Bahri H., Rumpel C., Rasse D.P., Bardoux G., Balesdent J., Girardin C., Chenu C., Mariotti A., 2005. Geoderma 128, 3

  1. An Experimental Field Study of Delayed Density Dependence in Natural Populations of Aedes albopictus

    PubMed Central

    Walsh, Rachael K.; Bradley, Caitlin; Apperson, Charles S.; Gould, Fred

    2012-01-01

    Aedes albopictus, a species known to transmit dengue and chikungunya viruses, is primarily a container-inhabiting mosquito. The potential for pathogen transmission by Ae. albopictus has increased our need to understand its ecology and population dynamics. Two parameters that we know little about are the impact of direct density-dependence and delayed density-dependence in the larval stage. The present study uses a manipulative experimental design, under field conditions, to understand the impact of delayed density dependence in a natural population of Ae. albopictus in Raleigh, North Carolina. Twenty liter buckets, divided in half prior to experimentation, placed in the field accumulated rainwater and detritus, providing oviposition and larval production sites for natural populations of Ae. albopictus. Two treatments, a larvae present and larvae absent treatment, were produced in each bucket. After five weeks all larvae were removed from both treatments and the buckets were covered with fine mesh cloth. Equal numbers of first instars were added to both treatments in every bucket. Pupae were collected daily and adults were frozen as they emerged. We found a significant impact of delayed density-dependence on larval survival, development time and adult body size in containers with high larval densities. Our results indicate that delayed density-dependence will have negative impacts on the mosquito population when larval densities are high enough to deplete accessible nutrients faster than the rate of natural food accumulation. PMID:22563428

  2. Experimental study of the nonlinear diffusion of a magnetic field and skin explosion of cylindrical conductors

    SciTech Connect

    Chaikovsky, S. A.; Datsko, I. M.; Labetskaya, N. A.; Rybka, D. V.; Ratakhin, N. A.; Oreshkin, V. I.

    2015-11-15

    The paper presents the results of an experimental study of the skin explosion of cylindrical conductors of diameter 1–3 mm (copper, aluminum, titanium, steel 3, and stainless steel) at a peak magnetic field of 200–600 T. The experiments were carried out on the MIG pulsed power generator at a current of up to 2.5 MA and a current rise time of 100 ns. The surface explosion of a conductor was identified by the appearance of a flash of extreme ultraviolet radiation. A minimum magnetic induction has been determined below which no plasma is generated at the conductor surface. For copper, aluminum, steel 3, titanium, and stainless steel, the minimum magnetic induction has been estimated to be (to within 10%) 375, 270, 280, 220, and 245 T, respectively.

  3. Experimental study of the nonlinear diffusion of a magnetic field and skin explosion of cylindrical conductors

    NASA Astrophysics Data System (ADS)

    Chaikovsky, S. A.; Oreshkin, V. I.; Datsko, I. M.; Labetskaya, N. A.; Rybka, D. V.; Ratakhin, N. A.

    2015-11-01

    The paper presents the results of an experimental study of the skin explosion of cylindrical conductors of diameter 1-3 mm (copper, aluminum, titanium, steel 3, and stainless steel) at a peak magnetic field of 200-600 T. The experiments were carried out on the MIG pulsed power generator at a current of up to 2.5 MA and a current rise time of 100 ns. The surface explosion of a conductor was identified by the appearance of a flash of extreme ultraviolet radiation. A minimum magnetic induction has been determined below which no plasma is generated at the conductor surface. For copper, aluminum, steel 3, titanium, and stainless steel, the minimum magnetic induction has been estimated to be (to within 10%) 375, 270, 280, 220, and 245 T, respectively.

  4. Experimental studies of the pressures generated by a liquid oxygen slug in a magnetic field

    NASA Astrophysics Data System (ADS)

    Boulware, Jeffrey C.; Ban, Heng; Jensen, Scott; Wassom, Steve

    2010-07-01

    The strong paramagnetic susceptibility of liquid oxygen (LOX) has established it as a good candidate for a cryogenic magnetic fluid system. While its properties have been known for several decades, a fundamental understanding of the behavior of LOX in a magnetically controlled fluid system is needed for the development of a suitable space application that can operate reliably and efficiently. This study conducted quantitative experiments on the dynamics of a LOX slug in a tube when subjected to electrically-induced magnetic fields within a solenoid. The experiments used a quartz tube with an inner diameter of 1.9 mm and LOX slugs of 0.6, 1.3, 1.9, 2.5, and 3.2 mm length at various initial positions relative to the solenoid. The pressures generated by the motion of the LOX slug under the magnetic force were recorded to characterize the pressure differential generated and the breakdown of the slug. The highest attainable pressure differential was found to be 1.45 kPa, which correlated well to theoretical predictions once the analysis accounted for the resistance heating of the solenoid. The noted differences between experimental results and theory could also be attributed to impeded slug motion from shear and mass forces. Within the workable pressure range, however, an optimal slug length was found which appropriately balances the pressure, shear, and magnetic forces in the system. This paper presents the experimental data on the dynamics and the maximum pressure differential generated by a LOX slug in a magnetic field and discusses the viability of LOX in a magnetic fluid management system intended for space applications.

  5. Experimental and numerical studies on plasma behavior flowing across perpendicular magnetic field

    NASA Astrophysics Data System (ADS)

    Takezaki, T.; Takahashi, K.; Sasaki, T.; Kikuchi, T.; Harada, N.

    2016-05-01

    To understand particle acceleration mechanisms in a collisionless shock, we have investigated the behaviors of a one-dimensional fast plasma flow in a perpendicular magnetic field by experimental and numerical simulations in a laboratory scale experiment. The velocity of the plasma flow generated by a taper-cone-shaped plasma focus device has varied by the gradient of the perpendicular magnetic field. The plasma flow has accelerated by applying the magnetic field with the negative gradient. To clarify the behavior of the plasma flow in the perpendicular magnetic field, numerical simulations based on an electromagnetic hybrid particle-in-cell (PIC) method have been carried out. These results indicate that the magnetic field gradient affects the plasma flow velocity.

  6. Analytical and experimental study of axisymmetric truncated plug nozzle flow fields

    NASA Technical Reports Server (NTRS)

    Muller, T. J.; Sule, W. P.; Fanning, A. E.; Giel, T. V.; Galanga, F. L.

    1972-01-01

    Experimental and analytical investigation of the flow field and base pressure of internal-external-expansion truncated plug nozzles are discussed. Experimental results for two axisymmetric, conical plug-cylindrical shroud, truncated plug nozzles are presented for both open and closed wake operations. These results include extensive optical and pressure data covering nozzle flow field and base pressure characteristics, diffuser effects, lip shock strength, Mach disc behaviour, and the recompression and reverse flow regions. Transonic experiments for a special planar transonic section are presented. An extension of the analytical method of Hall and Mueller to include the internal shock wave from the shroud exit is presented for closed wake operation. Results of this analysis include effects on the flow field and base pressure of ambient pressure ratio, nozzle geometry, and the ratio of specific heats. Static thrust is presented as a function of ambient pressure ratio and nozzle geometry. A new transonic solution method is also presented.

  7. An Experimental Study of the Near Field Region of a Free Jet with Passive Mixing Tabs

    NASA Technical Reports Server (NTRS)

    Bohl, D. G.; Foss, J. F.

    1997-01-01

    An experimental study was performed to determine the flow characteristics of a tabbed free jet. Results were acquired in the near field (nominally 2 tab widths upstream to 2 tab widths downstream of the exit plane) of a tabbed jet. Upstream pressure results showed static pressure distributions in both the x-and y-directions along the top surface of the tunnel. Hot-wire measurements showed rapid expansion of the core fluid into the ambient region. Two counter rotating regions of streamwise vorticity were shown on each side of the primary tab. An enhancement of the tabbed jet concept was proposed and tested. Specifically, two tabs, half the scale of the primary tab, were added to the primary tab to provide attachment surfaces for the normally occurring ejection of fluid. The secondary tabs caused a slight increase in the streamwise vorticity created from the upstream static pressure gradient while significantly increasing the re-oriented boundary layer vorticity. The combined pumping effect of the two counter rotating regions of vorticity caused a significant increase in the transport of the jet core fluid into the surrounding region.

  8. Experimental Study of Dispersion Control Utilizing both Magnetic and Electric Fields

    SciTech Connect

    Tanabe, Mikio; Ikegami, Masahiro; Noda, Akira; Shirai, Toshiyuki; Souda, Hikaru; Tongu, Hiromu; Shibuya, Shinji; Noda, Koji

    2006-03-20

    An experiment to control dispersion of beams in one bending section has been carried out. This experiment is based on a theory that the dispersion of accumulated beams can be controlled, if they are bent by a cross field composed of magnetic and an electric fields. Suppression of the dispersion can ease a shear which affects the 3-dimensionally ordered structure of the ultimate-low-temperature beams. In order to realize this scheme experimentally, we have manufactured a set of electrodes to create precise electric fields whose strength is 6.6 x 104 V/m for 24Mg+, 35keV beam. The electrodes have been inserted to the gap of dipole magnet. 3-dimensional field calculation shows that the error of the electric fields is less than 0.1% within {+-} 5mm from the reference orbit. We also tested the effect of the electric field using a single set of bending elements. The result showed that the linear dispersion can be controlled or canceled by changing the ratio of magnetic and electric fields.

  9. The biomineralization and fossilization of magnetotactic bacteria: Insights from experimental and field studies

    NASA Astrophysics Data System (ADS)

    Pan, Y.; LI, J.; Menguy, N.; Deng, C.; Kissel, C.; Liu, Q.; Zhu, R.

    2015-12-01

    Magnetotactic bacteria (MTB) are widespread prokaryotes which can navigate along the Earth's magnetic field lines and produce tens to hundreds of nanocrystals of magnetite (Fe3O4) or/and greigite (Fe3S4) aligned in chain(s) within a cell. The remains of MTB (i.e. magnetofossils) within geological records have therefore been considered as potential recorders of paleomagnetic, paleoenvironmental and ancient-life signals. These intracellularly-formed nanocrystals, called magnetosomes, generally have distinctively physical, chemical and crystallographic features from those magnetic minerals produced by abiotic or extracellular mineralization processes, and therefore could be distinguished by rock magnetic and electron microscopic approaches. However, identification and quantification of magnetofossils from sediments or sedimentary rocks are nevertheless not straightforward not only due to their tiny sizes, relatively low concentration, always mixing with abiotic magnetic minerals, but also the chain collapse and crystal maghemization during post-depositional processes. Comprehensive studies on the biomineralization and fossilization of magnetosomes are therefore essential for unambiguously identifying and quantitating magnetofossils from geologic samples. In this presentation, we summarize the biomineralization processes and magnetic properties of magnetosome chains within modern cultured and uncultured MTB. Experimental studies on the effects of the chain aligning and collapsing on the magnetic properties of magnetosomes are discussed, which give useful clues to understand the possible occurrence of magnetofossils within natural materials and their corresponding magnetic changes. Recent findings in magnetofossils from marine and lake sediments, showing how to identify magnetofossils from sediments by using the comprehensive rock magnetism, ferromagnetic resonance, and transmission electron microscopy approaches, as well as their implications for sedimentary magnetism

  10. Experimental Study of Entropy Production in Cells under Alternating Electric Field

    NASA Astrophysics Data System (ADS)

    Ding, Chang-Jiang; Luo, Liao-Fu

    2012-08-01

    We put forward a new method for measuring the entropy production in the living cell. It involves heating the sample by alternating the electric field and recording the outward heat flow. The entropy production in a normal cell MCF10A and a cancerous cell MDA-MB-231 were measured and compared. The results show that the method is effective for the entropy measurement of a living organism. The scaled electro-induced entropy production rate (SEEP) of MDA-MB-231 monotonically increases with the electric field strength at 5-40 V/cm. While that of MCF10A changes non-monotonically and there exists a peak at 5-30 V/cm. The electro-induced entropy production ratio (EEPR) is smaller than 1 in a large range of field strengths, from 5 to 25 V/cm, which reveals that under 5-25 V/cm electric field exposure, the direction of the entropy flow may be changed from normal tissue to cancerous cells. We present a facile and effective strategy for experimentally investigating the thermodynamic properties of the cell and give a deeper insight into the physical difference between normal and cancerous cells under electric field exposure.

  11. Experimental and numerical study of error fields in the CNT stellarator

    NASA Astrophysics Data System (ADS)

    Hammond, K. C.; Anichowski, A.; Brenner, P. W.; Pedersen, T. S.; Raftopoulos, S.; Traverso, P.; Volpe, F. A.

    2016-07-01

    Sources of error fields were indirectly inferred in a stellarator by reconciling computed and numerical flux surfaces. Sources considered so far include the displacements and tilts of the four circular coils featured in the simple CNT stellarator. The flux surfaces were measured by means of an electron beam and fluorescent rod, and were computed by means of a Biot–Savart field-line tracing code. If the ideal coil locations and orientations are used in the computation, agreement with measurements is poor. Discrepancies are ascribed to errors in the positioning and orientation of the in-vessel interlocked coils. To that end, an iterative numerical method was developed. A Newton–Raphson algorithm searches for the coils’ displacements and tilts that minimize the discrepancy between the measured and computed flux surfaces. This method was verified by misplacing and tilting the coils in a numerical model of CNT, calculating the flux surfaces that they generated, and testing the algorithm’s ability to deduce the coils’ displacements and tilts. Subsequently, the numerical method was applied to the experimental data, arriving at a set of coil displacements whose resulting field errors exhibited significantly improved agreement with the experimental results.

  12. Experimental study of stratified jet by simultaneous measurements of velocity and density fields

    NASA Astrophysics Data System (ADS)

    Xu, Duo; Chen, Jun

    2012-07-01

    Stratified flows with small density difference commonly exist in geophysical and engineering applications, which often involve interaction of turbulence and buoyancy effect. A combined particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) system is developed to measure the velocity and density fields in a dense jet discharged horizontally into a tank filled with light fluid. The illumination of PIV particles and excitation of PLIF dye are achieved by a dual-head pulsed Nd:YAG laser and two CCD cameras with a set of optical filters. The procedure for matching refractive indexes of two fluids and calibration of the combined system are presented, as well as a quantitative analysis of the measurement uncertainties. The flow structures and mixing dynamics within the central vertical plane are studied by examining the averaged parameters, turbulent kinetic energy budget, and modeling of momentum flux and buoyancy flux. At downstream, profiles of velocity and density display strong asymmetry with respect to its center. This is attributed to the fact that stable stratification reduces mixing and unstable stratification enhances mixing. In stable stratification region, most of turbulence production is consumed by mean-flow convection, whereas in unstable stratification region, turbulence production is nearly balanced by viscous dissipation. Experimental data also indicate that at downstream locations, mixing length model performs better in mixing zone of stable stratification regions, whereas in other regions, eddy viscosity/diffusivity models with static model coefficients represent effectively momentum and buoyancy flux terms. The measured turbulent Prandtl number displays strong spatial variation in the stratified jet.

  13. Simulation and experimental study of DC electric field distribution characteristics of rat hippocampal slices in vitro

    NASA Astrophysics Data System (ADS)

    Zheng, Yu; Dong, Lei; Gao, Yang; Qiu, Qian; Li, Ze-yan; Zhao, Zhe; Chen, Rui-juan; Wang, Hui-quan

    2016-06-01

    Direct current (DC) electric field is a noninvasive neuromodulation tool that can inhibit or facilitate excitability of neurons. Despite its efficacy, the dielectric constant of artificial cerebrospinal fluid and the position and direction of brain slices and other factors can affect the field intensity and distribution acting on the surface of rat hippocampus slices, thus causing errors. In this study, we describe a new analytical method optimized for DC electric fields acting on brain slices, and the design of an external DC electric field stimulator to allow scientific evaluation of brain slices. We investigated parameters regarding the uniformity of electric field distribution and identified the maximal parameters using the finite element method. Then, we selected and simplified slice images using magnetic resonance imaging data and calculated the electric field intensity of the original and simplified models. The electric field simulator induced action potential and excitatory postsynaptic current with intensities of 1, 5, and 10 V/m. This study describes the development of a new electric field stimulator and successfully demonstrates its practicability for scientific evaluation of tissue slices.

  14. Modeling and experimental study on near-field acoustic levitation by flexural mode.

    PubMed

    Liu, Pinkuan; Li, Jin; Ding, Han; Cao, Wenwu

    2009-12-01

    Near-field acoustic levitation (NFAL) has been used in noncontact handling and transportation of small objects to avoid contamination. We have performed a theoretical analysis based on nonuniform vibrating surface to quantify the levitation force produced by the air film and also conducted experimental tests to verify our model. Modal analysis was performed using ANSYS on the flexural plate radiator to obtain its natural frequency of desired mode, which is used to design the measurement system. Then, the levitation force was calculated as a function of levitation distance based on squeeze gas film theory using measured amplitude and phase distributions on the vibrator surface. Compared with previous fluid-structural analyses using a uniform piston motion, our model based on the nonuniform radiating surface of the vibrator is more realistic and fits better with experimentally measured levitation force. PMID:20040404

  15. Experimental studies of protozoan response to intense magnetic fields and forces

    NASA Astrophysics Data System (ADS)

    Guevorkian, Karine

    Intense static magnetic fields of up to 31 Tesla were used as a novel tool to manipulate the swimming mechanics of unicellular organisms. It is shown that homogenous magnetic fields alter the swimming trajectories of the single cell protozoan Paramecium caudatum, by aligning them parallel to the applied field. Immobile neutrally buoyant paramecia also oriented in magnetic fields with similar rates as the motile ones. It was established that the magneto-orientation is mostly due to the magnetic torques acting on rigid structures in the cell body and therefore the response is a non-biological, passive response. From the orientation rate of paramecia in various magnetic field strengths, the average anisotropy of the diamagnetic susceptibility of the cell was estimated. It has also been demonstrated that magnetic forces can be used to create increased, decreased and even inverted simulated gravity environments for the investigation of the gravi-responses of single cells. Since the mechanisms by which Earth's gravity affects cell functioning are still not fully understood, a number of methods to simulate different strength gravity environments, such as centrifugation, have been employed. Exploiting the ability to exert magnetic forces on weakly diamagnetic constituents of the cells, we were able to vary the gravity from -8 g to 10 g, where g is Earth's gravity. Investigations of the swimming response of paramecia in these simulated gravities revealed that they actively regulate their swimming speed to oppose the external force. This result is in agreement with centrifugation experiments, confirming the credibility of the technique. Moreover, the Paramecium's swimming ceased in simulated gravity of 10 g, indicating a maximum possible propulsion force of 0.7 nN. The magnetic force technique to simulate gravity is the only earthbound technique that can create increased and decreased simulated gravities in the same experimental setup. These findings establish a general

  16. Ex-situ experimental studies on serpentine flow field design for redox flow battery systems

    NASA Astrophysics Data System (ADS)

    Jyothi Latha, T.; Jayanti, S.

    2014-02-01

    Electrolyte distribution using parallel flow field for redox flow battery (RFB) applications shows severe non-uniformity, while the conventional design of using the carbon felt itself as the flow distributor gives too high pressure drop. An optimized flow field design for uniform flow distribution at a minimal parasitic power loss is therefore needed for RFB systems. Since the materials and geometrical dimensions in RFBs are very different from those used in fuel cells, the hydrodynamics of the flow fields in RFBs is likely to be very different. In the present paper, we report on a fundamental study of the hydrodynamics of a serpentine flow field relevant to RFB applications. The permeability of the porous medium has been measured under different compression ratios and this is found to be in the range of 5-8 × 10-11 m2. The pressure drop in two serpentine flow fields of different geometric characteristics has been measured over a range of Reynolds numbers. Further analysis using computational fluid dynamics simulations brings out the importance of the compression of the porous medium as an additional parameter in determining the flow distribution and pressure drop in these flow fields.

  17. Experimental study of near-field air entrainment by subsonic volcanic jets

    USGS Publications Warehouse

    Solovitz, S.A.; Mastin, L.G.

    2009-01-01

    The flow structure in the developing region of a turbulent jet has been examined using particle image velocimetry methods, considering the flow at steady state conditions. The velocity fields were integrated to determine the ratio of the entrained air speed to the jet speed, which was approximately 0.03 for a range of Mach numbers up to 0.89 and. Reynolds numbers up to 217,000. This range of experimental Mach and Reynolds numbers is higher than previously considered for high-accuracy entrainment measures, particularly in the near-vent region. The entrainment values are below those commonly used for geophysical analyses of volcanic plumes, suggesting that existing 1-D models are likely to understate the tendency for column collapse. Copyright 2009 by the American Geophysical Union.

  18. Rock Abrasion and Ventifact Formation on Mars from Field Analog, Theoretical, and Experimental Studies

    NASA Technical Reports Server (NTRS)

    Bridges, N. T.; Laity, J. E.

    2001-01-01

    Rocks observed by the Viking Landers and Pathfinder Lander/Sojourner rover exhibit a suite of perplexing rock textures. Among these are pits, spongy textures, penetrative flutes, lineaments, crusts, and knobs Fluvial, impact, chemical alteration, and aeolian mechanisms have been proposed for many of these. In an effort to better understand the origin and characteristics of Martian rock textures, abraded rocks in the Mojave Desert and other regions have been studied. We find that most Martian rock textures, as opposed to just a few, bear close resemblance to terrestrial aeolian textures and can most easily be explained by wind, not other, processes. Flutes, grooves, and some pits on Mars are consistent with abrasion by saltating particles, as described previously. However, many other rock textures probably also have an aeolian origin. Sills at the base of rocks that generally lie at high elevations, such as Half Dome, are consistent with such features on Earth that are related to moats or soil ramps that shield the basal part of the rock from erosion. Crusts consisting of fluted fabrics, such as those on Stimpy and Chimp, are similar to fluted crusts on Earth that spall off over time. Knobby and lineated rocks are similar to terrestrial examples of heterogeneous rocks that differentially erode. The location of specific rock textures on Mars also gives insight into their origin. Many of the most diagnostic ventifacts found at the Pathfinder site are located on rocks that lie near the crests or the upper slopes of ridges. On Earth, the most active ventifact formation occurs on sloped or elevated topography, where windflow is accelerated and particle kinetic energy and flux are increased. Integrated 0 together, these observations point to significant aeolian 0 modification of rocks on Mars and cast doubt on whether many primary textures resulting from other processes are preserved. Experimental simulations of abrasion in the presence of abundant sand indicate that

  19. Experimental and theoretical pore-scale study of thermal field responses to drying of porous surfaces

    NASA Astrophysics Data System (ADS)

    Aminzadeh, M.; Or, D.

    2015-12-01

    The drying of porous surfaces involves pores invasion at a sequence reflecting their respective capillary size (large pores invaded first similar to drainage). The emptying of an evaporating pore is accompanied by changes in the thermal field forming on the surface around the invaded pore that consequently affects surface temperature and energy partitioning over the drying surface. A novel experimental system was designed to systematically evaluate the coupling between surface temperature and evaporative flux from individual and clusters of pores drilled into rough glass surfaces connected to a liquid reservoir. Details of thermal fields around individual evaporating pores were observed for sparse and dense pore spacings including measurements of evaporating flux dynamics and results were compared with PCEB model [Aminzadeh and Or, 2014] predictions. We observed drying-induced pore emptying sequences of sintered glass bead surfaces by visual and thermal imaging using high resolution infrared imager. The links between pore emptying sequence at a drying surface inferred from pore size distribution, and surface temperature dynamics offer a possibility of predicting energy partitioning over drying terrestrial surfaces.

  20. Experimental research on electric propulsion. Note 5: Experimental study of a magnetic field stabilized arc-jet

    NASA Technical Reports Server (NTRS)

    Robotti, A. C.; Oggero, M.

    1984-01-01

    The possibility of using an electric arc under the influence of a magnetic field in ambient air to transform the heat energy of the working fluid arc into the kinetic energy of the jet was investigated. A convergent-divergent type nozzle was used. Variation of specific thrust and chamber pressure are discussed. Nitrogen was the propellant used.

  1. Experimental study of the flow field induced by a resonating piezoelectric flapping wing

    NASA Astrophysics Data System (ADS)

    Bidakhvidi, M. Ahmadi; Shirzadeh, R.; Steenackers, G.; Vanlanduit, S.

    2013-11-01

    Flexible plate structures with integrated piezoelectric patches offer interesting possibilities when considered as actuation mechanisms for energy harvesting devices, cooling devices and propulsion devices of micro-aerial vehicles. Most of the studies reported in literature are based on the assumption of a 2D aerodynamic flow. However, the flow behind a finite span wing is significantly more complex than that of an infinite span wing. In order to corroborate this statement, the present experimental study contains high-speed particle image velocimetry measurements performed on a piezoelectric finite span wing oscillating in air, at 84.8 Hz. The paper focuses on the situation of low Keulegan-Carpenter numbers (KC < 3). The dimensionless KC number describes the relative importance of the drag forces over inertia forces for objects that oscillate in a fluid flow at rest. The evolution of the unsteady vortex structures near the plate is characterized for different conditions. This allows a better understanding of the unsteady aerodynamics of flapping flight. The accomplished experimental data analysis has shown that the flow phenomena are strongly dependent on the KC values.

  2. Low dose short duration pulsed electromagnetic field effects on cultured human chondrocytes: An experimental study

    PubMed Central

    Anbarasan, Selvam; Baraneedharan, Ulaganathan; Paul, Solomon FD; Kaur, Harpreet; Rangaswami, Subramoniam; Bhaskar, Emmanuel

    2016-01-01

    Background: Pulsed electromagnetic field (PEMF) is used to treat bone and joint disorders for over 30 years. Recent studies demonstrate a significant effect of PEMF on bone and cartilage proliferation, differentiation, synthesis of extracellular matrix (ECM) and production of growth factors. The aim of this study is to assess if PEMF of low frequency, ultralow field strength and short time exposure have beneficial effects on in-vitro cultured human chondrocytes. Materials and Methods: Primary human chondrocytes cultures were established using articular cartilage obtained from knee joint during joint replacement surgery. Post characterization, the cells were exposed to PEMF at frequencies ranging from 0.1 to 10 Hz and field intensities ranging from 0.65 to 1.95 μT for 60 min/day for 3 consecutive days to analyze the viability, ECM component synthesis, proliferation and morphology related changes post exposure. Association between exposure doses and cellular effects were analyzed with paired't’ test. Results: In-vitro PEMF exposure of 0.1 Hz frequency, 1.95 μT and duration of 60 min/day for 3 consecutive days produced the most favorable response on chondrocytes viability (P < 0.001), ECM component production (P < 0.001) and multiplication. Exposure of identical chondrocyte cultures to PEMFs of 0.65 μT field intensity at 1 Hz frequency resulted in less significant response. Exposure to 1.3 μT PEMFs at 10 Hz frequency does not show any significant effects in different analytical parameters. Conclusions: Short duration PEMF exposure may represent a new therapy for patients with Osteoarthritis (OA). PMID:26955182

  3. Experimental study of the reduction of field emission by gas injection in vacuum for accelerator applications

    NASA Astrophysics Data System (ADS)

    Almaksour, K.; Kirkpatrick, M. J.; Dessante, Ph.; Odic, E.; Simonin, A.; de Esch, H. P. L.; Lepetit, B.; Alamarguy, D.; Bayle, F.; Teste, Ph.

    2014-10-01

    Field emission current from surfaces under vacuum and at high field strengths can be reduced by the injection of gas into the evacuated volume. In this paper, the effects of H2, He, N2, and Ar on this "dark" current emitted from a tungsten carbide point cathode for 2 cm gap distance is studied. Exposure to any of these gases at pressures on the order of 10-3-10-2 Pa was found to reduce the emission current by up to 90% with a time constant on the order of ˜1 minute as compared to the current at 10-6 Pa. The effect was strongly dependent on the gas nature, with Ar and N2 having larger effects at lower pressures than He and H2. The reduction was reversible, with the current increasing to near its original value with a time constant on the order of ˜1-10 minutes after pumping down. The effect of the gas remained in the absence of electric field, whatever the gas pressure. Mechanisms for these and related phenomena are discussed.

  4. Experimental study of the magnetic field enhanced Payne effect in magnetorheological elastomers.

    PubMed

    Sorokin, Vladislav V; Ecker, Eva; Stepanov, Gennady V; Shamonin, Mikhail; Monkman, Gareth J; Kramarenko, Elena Yu; Khokhlov, Alexei R

    2014-11-21

    The dynamic modulus and the loss factor of magnetorheological elastomers (MREs) of various compositions and anisotropies are studied by dynamic torsion oscillations performed in the absence and in the presence of an external magnetic field. The emphasis is on the Payne effect, i.e. the dependence of the elastomer magnetorheological characteristics on the strain amplitude and their evolution with cyclically increasing and decreasing strain amplitudes. MREs are based on two silicone matrices differing in storage modulus (soft, G' ∼ 10(3) Pa, and hard, G' ∼ 10(4) Pa, matrices). For each matrix, the concentration of carbonyl iron particles with diameters of 3-5 μm was equal to 70 and 82 mass% (22 and 35 vol%, respectively) in the composite material. Samples for each filler content, isotropic and aligned-particles, are investigated. It is found that the Payne effect significantly increases in the presence of an external magnetic field and varies with the cyclical loading which reaches saturation after several cycles. The results are interpreted as the processes of formation-destruction-reformation of the internal filler structure under the simultaneously applied mechanical force and magnetic field. Impacts of matrix elasticity and magnetic interactions on the filler alignment are elucidated. PMID:25278263

  5. An experimental study of gas-bubble evolution on a single exposure to a variable pressure field

    NASA Astrophysics Data System (ADS)

    Pavlenko, A. V.; Shestachenko, O. E.; Tyaktev, A. A.; Piskunov, Yu A.; Popov, V. N.; Bugaenko, I. L.; Sviridov, E. V.; Andreev, A. M.; Baishev, A. I.; Medvedev, V. M.

    2013-07-01

    This paper gives experimental results on the geometry of a gas bubble upfloating in a liquid for the case of a single exposure to a pressure pulse. An apparatus operated in the mode of rarefaction-compression wave generation in a liquid was used for experiments with two media: gas-air and liquid-water. Geometrical sizes were registered with the help of the optical shadow method. Experimental results were used to study how the evolution of dimensionless volume of the upfloating gas bubble depends on time (V(t)/V0) in the case of exposure to a variable dimensionless pressure field in time P(t)/P0.

  6. Mother-calf vocal communication in Atlantic walrus: a first field experimental study.

    PubMed

    Charrier, Isabelle; Aubin, Thierry; Mathevon, Nicolas

    2010-05-01

    In all colonial pinnipeds studied, mother-young vocal recognition exists and allows rapid and reliable meetings in spite of the confusing environment of the breeding colony. The efficiency of this recognition process guarantees pup survival, especially in species where females alternate foraging sea trips and lactation periods on land. The Atlantic Walrus (Odobenus rosmarus rosmarus) is a highly gregarious pinniped with females attending their calves for an extended period of time (2-3 years). Although we expect mother-calf vocal recognition to occur in this species due to the high density of individuals packed in herds, it has never been experimentally demonstrated. Here, we assessed the individual stereotypy of both mother and calf barks recorded in the wild by measuring frequency and temporal acoustic parameters. Both discriminant function and artificial neural network analyses resulted in high correct classification rates, underlying a well-defined individual stereotypy in parameters related to frequency modulation and frequency values. Playback experiments showed that mothers were more responsive to the barks of their own calf than to those of unrelated young. Finally, propagation experiments revealed that barks propagate at greater distances over water surface than over ice, acoustic features such as frequency modulation and frequency spectrum being highly resistant to degradation during propagation. Thus, acoustic analysis and propagation experiments suggest that these frequency parameters might be the key acoustic features involved in the individual identification process. This experimental study clearly demonstrates that Atlantic walrus has developed a highly reliable mother-calf vocal communication allowing such strong social bond. PMID:19960216

  7. Experimental study of the turbulent field behind a perforated vortex generator

    NASA Astrophysics Data System (ADS)

    Habchi, C.; Lemenand, T.; Della Valle, D.; Al Shaer, A.; Peerhossaini, H.

    2015-07-01

    The influence of the wake vortex arising behind a perforated tab on the mixing process in heat exchangers and chemical reactors is analyzed. The preliminary step of this study, i.e., investigation of the turbulent field generated by a single perforated tab, is presented here. For this aim, laser Doppler velocimetry measurements are conducted downstream from a perforated trapezoidal vortex generator placed in a wind tunnel. It is shown that two shear layers are generated by the tab. The first shear layer is located at the upper edge of the tab, and the other is ejected from the perforation edges. These shear layers are characterized by high turbulent kinetic energy levels, which are profitable for meso-mixing enhancement. Finally, a spectral study shows that the turbulent macro-scale is nearly the same for typical locations in the shear layers shed from the tab and perforation edges.

  8. An Experimental Study of Boiling in Reduced and Zero Gravity Fields

    NASA Technical Reports Server (NTRS)

    Usiskin, C. M.; Siegel, R.

    1961-01-01

    A pool boiling apparatus was mounted on a counterweighted platform which could be dropped a distance of nine feet. By varying the size of the counterweight, the effective gravity field on the equipment was adjusted between zero and unity. A study of boiling burnout in water indicated that a variation in the critical heat flux according to the one quarter power of gravity was reasonable. A consideration of the transient burnout process was necessary in order to properly interpret the data. A photographic study of nucleate boiling showed how the velocity of freely rising vapor bubbles decreased as gravity was reduced. The bubble diameters at the time of breakoff from the heated surface were found to vary inversely as gravity to the 1/3.5 power. Motion pictures were taken to illustrate both nucleate and film boiling in the low gravity range.

  9. Experimental and Field Studies of Escherichia coli O157:H7 in White-Tailed Deer

    PubMed Central

    Fischer, John R.; Zhao, Tong; Doyle, Michael P.; Goldberg, Martin R.; Brown, Cathy A.; Sewell, Christopher T.; Kavanaugh, Darrell M.; Bauman, Christopher D.

    2001-01-01

    Studies were conducted to evaluate fecal shedding of Escherichia coli O157:H7 in a small group of inoculated deer, determine the prevalence of the bacterium in free-ranging white-tailed deer, and elucidate relationships between E. coli O157:H7 in wild deer and domestic cattle at the same site. Six young, white-tailed deer were orally administered 108 CFU of E. coli O157:H7. Inoculated deer were shedding E. coli O157:H7 by 1 day postinoculation (DPI) and continued to shed decreasing numbers of the bacteria throughout the 26-day trial. Horizontal transmission to an uninoculated deer was demonstrated. Although E. coli O157:H7 bacteria were recovered from the gastrointestinal tracts of deer necropsied from 4 to 26 DPI, attaching and effacing lesions were not apparent in any deer. Results are similar to those of inoculation studies in calves and sheep. In field studies, E. coli O157 was not detected in 310 fresh deer fecal samples collected from the ground. It was detected in feces, but not in meat, from 3 of 469 free-ranging deer in 1997. In 1998, E. coli O157 was not detected in 140 deer at the single positive site found in 1997; however, it was recovered from 13 of 305 dairy and beef cattle at the same location. Isolates of E. coli O157:H7 from deer and cattle at this site differed with respect to pulsed-field gel electrophoresis patterns and genes encoding Shiga toxins. The low overall prevalence of E. coli O157:H7 and the identification of only one site with positive deer suggest that wild deer are not a major reservoir of E. coli O157:H7 in the southeastern United States. However, there may be individual locations where deer sporadically harbor the bacterium, and venison should be handled with the same precautions recommended for beef, pork, and poultry. PMID:11229913

  10. Experimental study of near-field entrainment of moderately overpressured jets

    USGS Publications Warehouse

    Solovitz, S.A.; Mastin, L.G.; Saffaraval, F.

    2011-01-01

    Particle image velocimetry (PIV) experiments have been conducted to study the velocity flow fields in the developing flow region of high-speed jets. These velocity distributions were examined to determine the entrained mass flow over a range of geometric and flow conditions, including overpressured cases up to an overpressure ratio of 2.83. In the region near the jet exit, all measured flows exhibited the same entrainment up until the location of the first shock when overpressured. Beyond this location, the entrainment was reduced with increasing overpressure ratio, falling to approximately 60 of the magnitudes seen when subsonic. Since entrainment ratios based on lower speed, subsonic results are typically used in one-dimensional volcanological models of plume development, the current analytical methods will underestimate the likelihood of column collapse. In addition, the concept of the entrainment ratio normalization is examined in detail, as several key assumptions in this methodology do not apply when overpressured.

  11. Experimental and theoretical study on nonsequential double ionization of carbon disulfide in strong near-IR laser fields

    NASA Astrophysics Data System (ADS)

    Zuo, Wanlong; Ben, Shuai; Lv, Hang; Zhao, Lei; Guo, Jing; Liu, Xue-Shen; Xu, Haifeng; Jin, Mingxing; Ding, Dajun

    2016-05-01

    Nonsequential double ionization (NSDI) of carbon disulfide CS2 in strong 800-nm laser fields is studied experimentally and theoretically. A knee structure is observed in the intensity-dependent double ionization (DI) yield in linearly polarized laser fields, which exhibits a strong dependence on the laser ellipticity. The electron momentum distributions and energy trajectories after DI in both linearly and circularly polarized laser fields are investigated by employing the two-dimensional classical ensemble method. The results clearly show the evidence of NSDI in the strong-field DI of CS2 molecules. It is demonstrated that, similar to that of atoms, NSDI of CS2 molecules is produced via laser-driven electron recollision with the ion core and presents electron-electron correlations in the process. Analysis indicates that both mechanisms in atomic strong-field NSDI, i.e., recollision impact ionization and recollision excitation with subsequent ionization, may also be contributed to NSDI of CS2 in strong laser fields. Further studies are no doubt necessary for a full understanding of the underlying physical mechanism of molecular strong-field NSDI, due to the multicenter character of the molecular structure and the complex molecular excited states that could be involved in the ionization.

  12. An experimental setup to study the expansion dynamics of laser blow-off plasma plume in variable transverse magnetic field

    NASA Astrophysics Data System (ADS)

    Kumar, Ajai; Chaudhari, Vishnu; Patel, Kiran; George, Sony; Sunil, S.; Singh, R. K.; Singh, Ranjeet

    2009-03-01

    In the present work we report generation of uniform and variable pulsed magnetic field in synchronization with pulsed plasma for the study of the expansion dynamics of laser blow-off (LBO) plasma plume. The experimental procedure for optimizing various parameters of the setup, e.g., the production of pulsed field and its synchronization with pulsed plasma and diagnostics system, is also reported. Until now the effect of magnetic field was studied using fixed field. The present setup, however, provides variable and uniform field in synchronization with the setup. A low cost time sequencing control module has been developed for the above purpose. Although the main emphasis is on the technical aspect of the setup, salient features of the effect of transverse magnetic field on the evolution features of the neutral and ionic species are also reported briefly. It is observed that LBO generated plume have a stronger correlation with the magnetic field in comparison to the conventional laser produced plasma experiments as reported earlier.

  13. Plastic Responses of a Sessile Prey to Multiple Predators: A Field and Experimental Study

    PubMed Central

    Hirsch, Philipp Emanuel; Cayon, David; Svanbäck, Richard

    2014-01-01

    Background Theory predicts that prey facing a combination of predators with different feeding modes have two options: to express a response against the feeding mode of the most dangerous predator, or to express an intermediate response. Intermediate phenotypes protect equally well against several feeding modes, rather than providing specific protection against a single predator. Anti-predator traits that protect against a common feeding mode displayed by all predators should be expressed regardless of predator combination, as there is no need for trade-offs. Principal Findings We studied phenotypic anti-predator responses of zebra mussels to predation threat from a handling-time-limited (crayfish) and a gape-size-limited (roach) predator. Both predators dislodge mussels from the substrate but diverge in their further feeding modes. Mussels increased expression of a non-specific defense trait (attachment strength) against all combinations of predators relative to a control. In response to roach alone, mussels showed a tendency to develop a weaker and more elongated shell. In response to crayfish, mussels developed a harder and rounder shell. When exposed to either a combination of predators or no predator, mussels developed an intermediate phenotype. Mussel growth rate was positively correlated with an elongated weaker shell and negatively correlated with a round strong shell, indicating a trade-off between anti-predator responses. Field observations of prey phenotypes revealed the presence of both anti-predator phenotypes and the trade-off with growth, but intra-specific population density and bottom substrate had a greater influence than predator density. Conclusions Our results show that two different predators can exert both functionally equivalent and inverse selection pressures on a single prey. Our field study suggests that abiotic factors and prey population density should be considered when attempting to explain phenotypic diversity in the wild. PMID

  14. An experimental correlation study between field-target overlap and sensitivity of surface plasmon resonance biosensors based on sandwiched immunoassays

    NASA Astrophysics Data System (ADS)

    Ryu, Yeonsoo; Moon, Seyoung; Oh, Youngjin; Kim, Yonghwi; Kim, Donghyun

    2012-10-01

    In this report, we have studied the effectiveness of field-target overlap to evaluate detection sensitivity of surface plasmon resonance (SPR) biosensors. The investigation used theoretical analysis based on the transfer matrix method, which was experimentally confirmed by thin film-based detection in sandwich and reverse sandwich immunoglobulin G (IgG) assays. Both theoretical and experimental results show that strong correlation exists between the overlap and the sensitivity with the coefficient of correlation higher than 95% in all the cases that we have considered. We have also confirmed the correlation in diffraction grating-based SPR measurement of IgG/anti-IgG interactions. The correlation elucidates the mechanism behind the far-field detection sensitivity of SPR biosensors and can lead to the enhancement of SPR biosensing with molecular scale sensitivity.

  15. Effects of Prompting in Reflective Learning Tools: Findings from Experimental Field, Lab, and Online Studies

    PubMed Central

    Renner, Bettina; Prilla, Michael; Cress, Ulrike; Kimmerle, Joachim

    2016-01-01

    Reflective learning is an important type of learning both in formal and informal situations—in school, higher education, at the workplace, and in everyday life. People may benefit from technical support for reflective learning, in particular when supporting each other by reflecting not only upon their own but also upon other people’s problems. We refer to this collective approach where people come together to think about experiences and find solutions to problems as “collaborative reflection.” We present three empirical studies about the effects of prompting in reflective learning tools in such situations where people reflect on others’ issues. In Study 1 we applied a three-stage within-group design in a field experiment, where 39 participants from two organizations received different types of prompts while they used a reflection app. We found that prompts that invited employees to write down possible solutions led to more comprehensive comments on their colleagues’ experiences. In Study 2 we used a three-stage between-group design in a laboratory experiment, where 78 university students were invited to take part in an experiment about the discussion of problems at work or academic studies in online forums. Here we found that short, abstract prompts showed no superiority to a situation without any prompts with respect to quantity or quality of contributions. Finally, Study 3 featured a two-stage between-group design in an online experiment, where 60 participants received either general reflection instructions or detailed instructions about how to reflect on other people’s problems. We could show that detailed reflection instructions supported people in producing more comprehensive comments that included more general advice. The results demonstrate that to increase activity and to improve quality of comments with prompting tools require detailed instructions and specific wording of the prompts. PMID:27303361

  16. Experimental study of temperature fields and thermal fluxes in the electrode walls of an MGD accelerator

    SciTech Connect

    Alferov, V.I.; Vitkovskaya, O.N.; Panfilova, O.V.; Rudakova, A.P.; Sukhobokov, A.D.; Shcherbakov, G.I.

    1980-07-01

    Results are presented of an experimental study of the features of heat transfer from a flow of air with KNa admixture to the electrode walls of an MGD accelerator in a wide range of operating modes (B=1--2.5 T,j=4--45 A/cm/sup 2/,P/sub st/0.2=(en-dash0.5)x10/sup 5/ Pa). Data are obtained on the size and distribution of the thermal fluxes in different zones of an MGD channel and over the electrodes, taken separately. Methods are chosen for calculating the convective thermal flux on the electrode walls over the entire length of the accelerator channel, and the values of the thermal flux in the discharge zone due to processes at the electrodes are determined. A possible explanation is proposed for the difference between the values of the thermal fluxes at the electrode walls over different portions of the MGD channel, which is based on features of the behavior of microarcs on the surface of the electrodes.

  17. Experimental Study of a Two-Dimensional Applied-Field Magnetoplasmadynamic Thruster

    NASA Astrophysics Data System (ADS)

    Iwakawa, Akira; Nakata, Daisuke; Kuninaka, Hitoshi

    A two-dimensional applied-field magnetoplasmadynamic thruster (2D AF-MPDT) has been developed. A strong crossed magnetic field of more than 1 T can be applied to the 2D AF-MPDT. A thrust measurement system was newly developed. Successful operation with several applied magnetic field strengths from 0 T to 1 T was achieved and acceptable thrust efficiency was obtained. The discharge voltage increased when the magnetic field was applied. The thrust efficiency improves with increasing magnetic field. An operation limit such as a voltage hash was not observed. In this paper, the results indicate that the thrust efficiency of the 2D AF-MPDT can be improved with a strong applied crossed magnetic field.

  18. Experimental Study of Corona Properties with a Heated Discharge Electrode and Crossed Magnetic Fields Individually

    NASA Astrophysics Data System (ADS)

    Abu-Elabass, Karim

    2015-07-01

    This work involves ac and dc corona in air with heated discharge electrode, and breakdown streamers in corona in a crossed magnetic field. At first, the triggering of the breakdown streamers in positive and ac corona are governed by the temperature of the discharge electrode. In the negative corona, however, the breakdown streamers found to be practically independent of the temperature of the discharge electrode. Then, the transverse magnetic field, applied perpendicularly to the electric field, result in an improvement in pre-breakdown characteristic of the wire-tube gap. The application of the transverse field has the effect of increasing the corona onset voltage and the breakdown voltage. Also the transverse applied field has the effect of decreasing the corona current. It has been observed that triggering of the breakdown streamers in negative corona is affected appreciably by the transverse magnetic field.

  19. Experimental Study on Current Decay Characteristics of Persistent Current HTS Magnet by Alternating Magnetic Field

    NASA Astrophysics Data System (ADS)

    Park, Young Gun; Lee, Chang Young; Hwang, Young Jin; Lee, Woo Seung; Lee, Jiho; Jo, Hyun Chul; Chung, Yoon Do; Ko, Tae Kuk

    This paper deals with a current decay characteristics of a high temperature superconducting (HTS) magnet operated in persistent current mode (PCM). In superconducting synchronous machine applications such as linear synchronous motor (LSM), the superconducting coil is designed to operate in the PCM to obtain steady magnetic field with DC transport current. This superconducting magnet operates on a direct current, but it can be exposed to alternating magnetic field due to the armature winding. When the magnet is subjected to an external time-varying magnetic field, it is possible to result in a decay of the current in PCM system due to AC loss. In this research, a PCM system with armature coil which generates time-varying magnetic field was fabricated to verify current decay characteristics by external alternating magnetic field. The current decay rate was measured by using a hall sensor as functions of amplitude and frequency of armature coil.

  20. Experimental study of cooling enhancement using a Fe3O4 magnetic nanofluid, in an applied magnetic field

    NASA Astrophysics Data System (ADS)

    Stoian, F. D.; Holotescu, S.

    2014-11-01

    This paper presents the results of an experimental study that envisaged the evaluation of the cooling capabilities of a transformer oil based magnetic nanofluid with the solid volume fraction of magnetite nanoparticles equal to 0.0162, in an AC applied magnetic field (f = 50 Hz). The heating and cooling regimes of a coil immersed in the magnetic nanofluid were compared to that corresponding to the base fluid (transformer oil). The results of our study indicate that the temperature rise rate of the magnetic nanofluid is lower than that corresponding to the transformer oil and a lower stationary temperature is obtained in the coil core, where the magnetic flux density is the largest.

  1. Experimental study of the flow field inside a whirling annular seal

    NASA Technical Reports Server (NTRS)

    Morrison, Gerald L.; Deotte, Robert E., Jr.; Thames, H. Davis, III

    1992-01-01

    The flow field inside a whirling annular seal was measured using a 3-D Laser Doppler Anemometer (LDA) system. The seal investigated has a clearance of 1.27 mm, a length of 37.3 mm, and is mounted on a drive shaft with a 50 percent eccentricity ratio. This results in the rotor whirling at the same speed as the shaft rotation (whirl ratio = 1.0). The seal is operated at Reynolds number of 12,000 and a Taylor number of 6,300 (3,600 rpm). The 3-D LDA system is equipped with a rotary encoding system which is used to produce phase averaged measurements of the entire mean velocity vector field and Reynolds stress tensor field from 0.13 mm upstream to 0.13 mm downstream of the seal. The mean velocity field reveals a highly three dimensional flow field with large radial velocities near the inlet of the seal as well as a recirculation zone on the rotor surface. The location of maximum mean axial velocity migrates from the pressure side of the rotor at the inlet to the suction side at turbulence kinetic energy. However, turbulence production and dissipation attain equilibrium fairly quickly with remaining relatively constant over the last half of the seal.

  2. Validation of in situ networks via field sampling: case study in the South Fork Experimental Watershed

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The calibration and validation of soil moisture remote sensing products is complicated by the logistics of installing a soil moisture network for a long term period in an active landscape. Therefore, these stations are located along field boundaries or in non-representative sites with regards to so...

  3. Experimental and computational studies of the relative flow field in a centrifugal blood pump.

    PubMed

    Ng, B T; Chan, W K; Yu, S C; Li, H D

    2000-01-01

    The relative flow field within the impeller passage of a centrifugal blood pump had been examined using flow visualization technique and computational fluid dynamics. It was found that for a seven-blade radial impeller design, the required flow rate and static pressure rise across the pump could be achieved but the flow field within the blades was highly undesirable. Two vortices were observed near the suction side and these could lead to thrombus formation. Preliminary results presented in this article are part of our overall effort to minimize undesirable flow patterns such flow separation and high shear stress regions within the centrifugal blood pump. This will facilitate the future progress in developing a long-term clinically effective blood pump. PMID:10999375

  4. Validation of in Situ Networks Via Field Sampling: Case Study in the South Fork Experimental Watershed

    NASA Astrophysics Data System (ADS)

    Cosh, M. H.; McKee, L.; Bindlish, R.; Coopersmith, E. J.; Jackson, T. J.; Prueger, J. H.

    2014-12-01

    The calibration and validation of soil moisture remote sensing products is complicated by the logistics of installing a soil moisture network for a long term period in an active landscape. Therefore, these stations are located along field boundaries or in non-representative sites with regards to soil type or soil moisture. The representative character of this network can only be established by large scale field sampling to provide a calibration dataset. A team of samplers were deployed twice a week for the summer of 2014 to collect surface soil moisture data across a variety of land covers at 44 sites. These samples were compared and scaled to the domain to get a better understanding of the large scale soil moisture distributions and dynamics. In addition, comparisons are made to the Soil Moisture Ocean Salinity (SMOS) soil moisture product for the length of the network installation.

  5. Experimental study on a Nb3Al insert coil under high magnetic field

    NASA Astrophysics Data System (ADS)

    Zhu, Guang; Dai, Yinming; Cheng, Junsheng; Chang, Kun; Liu, Jianhua; Wang, Qiuliang; Pan, Xifeng; Li, Chao

    2016-06-01

    Nb3Al is one of the most promising superconductors to replace Nb3Sn in large scale, high field superconducting magnet. Since the complicated conductor manufacturing process, long and stable Nb3Al conductor is difficult to acquire in a commercial scale. Based on a 70 m length of Nb-Al precursor conductor, we designed and fabricated a Nb3Al coil. The coil winding, low temperature diffusion heat treatment and epoxy impregnation are described in detail. The finished Nb3Al coil is tested as an insert in a background magnet. The test is performed at the background field from 7 T to 15 T. The test results are analyzed and presented in this paper.

  6. Automatic recognition of intermittent failures - An experimental study of field data

    NASA Technical Reports Server (NTRS)

    Iyer, Ravishankar K.; Young, Luke T.; Krishna Iyer, P. V.

    1990-01-01

    A methodology is proposed for recognizing the symptoms of persistent problems in large systems. The system error rate is used to identify the error states among which relationships may exist. Statistical techniques are used to validate and quantify the strength of the relationship among these error states. As input, the approach takes the raw error logs containing a single entry for each error that is detected as an isolated event. As output, it produces a list of symptoms that characterize persistent errors. Thus, given a failure, it is determined whether the failure is an intermittent manifestation of a common fault or whether it is an isolated (transient) incident. The technique is shown to work on two CYBER systems and an IBM 3081 multiprocessor system. Comparisons to real failure/repair information obtained from field engineers show that, in about 85 percent of the cases, the error symptoms recognized by this approach correspond to real problems. The remaining 15 percent of the cases, although not directly supported by field data, are confirmed as being valid problems.

  7. Experimental studies of a gyroklystron operating in the field of a permanent magnet

    NASA Astrophysics Data System (ADS)

    Antakov, I. I.; Gachev, I. G.; Zasypkin, E. V.

    2011-08-01

    We have developed and tested a gyroklystron operating with the second harmonic of the electron cyclotron frequency at a frequency of 32.3 GHz in the field of a permanent magnet. In the two-and three-cavity versions of the gyroklystron, the peak power of the output radiation reached 320 kW with an efficiency of 30%, an amplification coefficient of 20-25 dB, and an operating frequency bandwidth of 0.05%. In the wide-band version of the gyroklystron, the amplification bandwidth was equal to 0.27% for an output power of 200 kW and an amplification coefficient of 13 dB.

  8. Experimental and Numerical Study of Wind and Turbulence in a Near-Field Dispersion Campaign at an Inhomogeneous Site

    NASA Astrophysics Data System (ADS)

    Wei, Xiao; Dupont, Eric; Gilbert, Eric; Musson-Genon, Luc; Carissimo, Bertrand

    2016-04-01

    We present a detailed experimental and numerical study of the local flow field for a pollutant dispersion experimental program conducted at SIRTA (Site Instrumental de Recherche par Télédétection Atmosphérique), a complex and intensively instrumented site in a southern suburb of Paris. Global analysis of continuous measurements over 2 years highlights the impact of terrain heterogeneity on wind and turbulence. It shows that the forest to the north of the experimental field induces strong directional shear and wind deceleration below the forest canopy height. This directional shear is stronger with decreasing height and decreasing distance from the forest edge. Numerical simulations are carried out using Code_Saturne, a computational fluid dynamics code, in Reynolds-averaged Navier-Stokes mode with a standard k{-}\\varepsilon closure and a canopy model, in neutral and stable stratifications. These simulations are shown to reproduce globally well the characteristics of the mean flow, especially the directional wind shear in northeasterly and northwesterly cases and the turbulent kinetic energy increase induced by the forest. However, they slightly underestimate wind speed and the directional shear of the flow below the forest canopy height. Sensitivity studies are performed to investigate the influence of leaf area density, inlet stability condition, and roughness length. These studies show that the typical features of the canopy flow become more pronounced as canopy density increases. Performance statistics indicate that the impact of the forest and adequate inlet profiles are the most important factors in the accurate reproduction of flow at the site, especially under stable stratification.

  9. An experimental study on the effects of temperature and magnetic field strength on the magnetorheological fluid stability and MR effect.

    PubMed

    Rabbani, Yahya; Ashtiani, Mahshid; Hashemabadi, Seyed Hassan

    2015-06-14

    In this study, the stability and rheological properties of a suspension of carbonyl iron microparticles (CIMs) in silicone oil were investigated within a temperature range of 10 to 85 °C. The effect of adding two hydrophobic (stearic and palmitic) acids on the stability and magnetorheological effect of a suspension of CIMs in silicone oil was studied. According to the results, for preparing a stable and efficient magnetorheological (MR) fluid, additives should be utilized. Therefore, 3 wt% of stearic acid was added to the MR fluid which led to an enhancement of the fluid stability over 92% at 25 °C. By investigating shear stress variation due to the changes in the shear rate for acid-based MR fluids, the maximum yield stress was obtained by fitting the Bingham plastic rheological model at high shear rates. Based on the existing correlations of yield stress and either temperature or magnetic field strength, a new model was fitted to the experimental data to monitor the simultaneous effect of magnetic field strength and temperature on the maximum yield stress. The results demonstrated that as the magnetic field intensified or the temperature decreased, the maximum yield stress increased dramatically. In addition, when the MR fluid reached its magnetic saturation, the viscosity of fluid depended only on the shear rate. PMID:25940850

  10. Effects of a tattoo on men's behavior and attitudes towards women: An experimental field study.

    PubMed

    Guéguen, Nicolas

    2013-11-01

    Previous studies have indicated negative evaluations of women with tattoos. However, a study by Swami and Furnham (2007) showed that tattooed women were rated as less physically attractive but more sexually promiscuous. Given that men interpret women's sexual intent according to their physical appearance, we predicted that women with tattoos would be more favorably approached by men. A temporary tattoo was placed on confederates' lower back, or not, and all confederates were instructed to read a book while lying flat on their stomach on a well-known beach. Two experiments were conducted. The first experiment showed that more men (N = 220) approached the tattooed confederates and that the mean latency of their approach was quicker. A second experiment showed that men (N = 440) estimated to have more chances to have a date and to have sex on the first date with tattooed confederates. However, the level of physical attractiveness attributed to the confederate was not influenced by the tattoo condition. These results were discussed with respect to men's possible misinterpretation of women wearing tattoos and the risks associated with this misinterpretation. PMID:23657810

  11. The impact of nutritional labels and socioeconomic status on energy intake. An experimental field study.

    PubMed

    Crockett, Rachel A; Jebb, Susan A; Hankins, Matthew; Marteau, Theresa M

    2014-10-01

    There is some evidence for paradoxical effects of nutritional labelling on energy intake particularly amongst restrained eaters and those with a higher body mass index (BMI) resulting in greater consumption of energy from foods with a positive health message (e.g. "low-fat") compared with the same foods, unlabelled. This study aimed to investigate, in a UK general population sample, the likelihood of paradoxical effects of nutritional labelling on energy intake. Participants (n = 287) attended a London cinema and were offered a large tub of salted or toffee popcorn. Participants were randomised to receive their selected flavour with one of three labels: a green low-fat label, a red high-fat label or no label. Participants watched two film clips while completing measures of demographic characteristics, emotional state and taste of the popcorn. Following the experiment, popcorn consumption was measured. There were no main effects of nutritional labelling on consumption. Contrary to predictions neither BMI nor weight concern moderated the effect of label on consumption. There was a three-way interaction between low-fat label, weight concern and socioeconomic status (SES) such that weight-concerned participants of higher SES who saw a low-fat label consumed more than weight unconcerned participants of similar SES (t = -2.7, P = .04). By contrast, weight-concerned participants of lower SES seeing either type of label, consumed less than those seeing no label (t = -2.04, P = .04). Nutritional labelling may have different effects in different socioeconomic groups. Further studies are required to understand fully the possible contribution of food labelling to health inequalities. PMID:24879885

  12. Effect of pulsed electromagnetic field therapy on experimental pain: A double-blind, randomized study in healthy young adults.

    PubMed

    Beaulieu, Karen; Beland, Patricia; Pinard, Marilee; Handfield, Guilène; Handfield, Nicole; Goffaux, Philippe; Corriveau, Hélène; Léonard, Guillaume

    2016-01-01

    Previous studies suggested that pulsed electromagnetic field (PEMF) therapy can decrease pain. To date, however, it remains difficult to determine whether the analgesic effect observed in patients are attributable to a direct effect of PEMF on pain or to an indirect effect of PEMF on inflammation and healing. In the present study, we used an experimental pain paradigm to evaluate the direct effect of PEMF on pain intensity, pain unpleasantness, and temporal summation of pain. Twenty-four healthy subjects (mean age 22 ± 2 years; 9 males) participated in the experiment. Both real and sham PEMF were administered to every participant using a randomized, double-blind, cross-over design. For each visit, PEMF was applied for 10 minutes on the right forearm using a portable device. Experimental pain was evoked before (baseline) and after PEMF with a 9 cm(2) Pelletier-type thermode, applied on the right forearm (120 s stimulation; temperature individually adjusted to produce moderate baseline pain). Pain intensity and unpleasantness were evaluated using a 0-100 numerical pain rating scale. Temporal summation was evaluated by comparing pain intensity ratings obtained at the end of tonic nociceptive stimulation (120 s) with pain intensity ratings obtained after 60 s of stimulation. When compared to baseline, there was no change in pain intensity and unpleasantness following the application of real or sham PEMF. PEMF did not affect temporal summation. The present observations suggest that PEMF does not directly influence heat pain perception in healthy individuals. PMID:27014804

  13. Analytical and experimental study of the acoustics and the flow field characteristics of cavitating self-resonating water jets

    SciTech Connect

    Chahine, G.L.; Genoux, P.F.; Johnson, V.E. Jr.; Frederick, G.S.

    1984-09-01

    Waterjet nozzles (STRATOJETS) have been developed which achieve passive structuring of cavitating submerged jets into discrete ring vortices, and which possess cavitation incipient numbers six times higher than obtained with conventional cavitating jet nozzles. In this study we developed analytical and numerical techniques and conducted experimental work to gain an understanding of the basic phenomena involved. The achievements are: (1) a thorough analysis of the acoustic dynamics of the feed pipe to the nozzle; (2) a theory for bubble ring growth and collapse; (3) a numerical model for jet simulation; (4) an experimental observation and analysis of candidate second-generation low-sigma STRATOJETS. From this study we can conclude that intensification of bubble ring collapse and design of highly resonant feed tubes can lead to improved drilling rates. The models here described are excellent tools to analyze the various parameters needed for STRATOJET optimizations. Further analysis is needed to introduce such important factors as viscosity, nozzle-jet interaction, and ring-target interaction, and to develop the jet simulation model to describe the important fine details of the flow field at the nozzle exit.

  14. Long lifetimes of high molecular Rydberg states in crossed magnetic and electric fields: An experimental and classical computational study

    NASA Astrophysics Data System (ADS)

    Mühlpfordt, Annette; Even, U.; Rabani, Eran; Levine, R. D.

    1995-05-01

    Crossed magnetic and electric fields are observed to extend the lifetime of high molecular Rydberg states of DABCO (1,4-Diazabicyclo[2.2.2]octane) well into the microsecond range. The experimental and computational (using classical mechanics and for a diatomic polar core) results agree both on the magnitude of the effect and on its decrease with increasing electrical field. Theoretical considerations suggest that this time-stretching effect is only present for high Rydberg states and/or for not too weak fields. The computed lifetime increases as the magnetic-field strength is decreased but it requires a finite magnetic field for the onset of the effect. The experimental technique of detection of the surviving Rydberg states via their ionization in a delayed field pulse (known as ZEKE spectroscopy) is most easily implemented for high (say, n>100) but not too high (n<400) Rydberg states. In this regime, the magnetic field required for the additional time stretching is larger than that due to the earth but can be significantly weaker than that required to induce extensive chaotic behavior. The results of the numerically exact classical simulations are interpreted using equations of motion, cast in the form of a mapping, which retain terms up to second order in the fields. (The first-order terms are qualitatively and quantitatively not, by themselves, sufficient.) As is to be expected on physical grounds, the origin of the effect is the slow, periodic modulation of the magnitude of the magnetic quantum number ml of the electron due to terms second order in the magnetic field. Since the angular momentum l of the electron is bounded from below by ml, and since it requires a low l for the electron to couple effectively to the molecular core, the presence of the magnetic field provides for an elongation of the time scale which is over and above that made possible due to the periodic motion of l due to the dc electric field.

  15. Experimental study on the effect of applying a crossed magnetic field on the insulator flashover behavior in high vacuum

    NASA Astrophysics Data System (ADS)

    Abu-Elabass, K.

    2015-09-01

    In this study, a possible method of reducing the flashover stress is achieved by the effect of an additional magnetic field in the transverse direction on the main applied electric field. The degree of vacuum used in this study was 5×10-5 Pa. The magnetic flux density B employed in this study extends from 4×10-3 to 24×10-3 T. From the results obtained throughout this work, the transverse magnetic field increases the flashover voltage and decreases the leakage current. The effect of the transverse magnetic field on the surface flashover of the dielectric solid in vacuum shows a marked dependence on the material and the thickness of the test specimen, the vacuum degree, the type of electric field (AC or DC) as well as the type of magnetic field (AC or DC).

  16. An experimental study using flow visualization on the effect of an acoustic field on heat transfer from spheres

    NASA Technical Reports Server (NTRS)

    Leung, W. W.; Baroth, E. C.

    1986-01-01

    The physical mechanisms responsible for the heat transfer process in a thermal-acoustic field were investigated using the technique of holographic interferometry for flow visualization. Experimental results were obtained with sound pressure levels in the range of 120 to 150 decibels, relative to a pressure of 0.0002 dynes/sq cm. Steady state laminar flow was observed when the vibrational Reynolds number was below 400; separated flow was observed when it was above 400. In the presence of a horizontal sound field, the data indicate that the relation between the vibrational Nusselt number, Nu(v) and the vibrational Reynolds number, Re(v) is given by Nu(v) = Re(v) exp 0.22. In the presence of a vertical sound field, the corresponding relation is Nu(v) = Re(v) exp 0.15.

  17. Experimental and theoretical study on effects of magnetic field topology on near wall conductivity in a Hall thruster

    SciTech Connect

    Yu Daren; Li Hong; Ning Zhongxi; Yan Guojun; Wu Zhiwen

    2009-10-15

    An experiment has been made to investigate the effect of curved magnetic field topology on near wall conductivity in the ion acceleration region of Hall thrusters. The experimental results show that the electron current due to near wall conductivity is of the minimum in the case of focused topology and increases in the cases of both less-focus and over-focus topologies. This finding cannot be explained properly by the magnetic mirror effect, which is the one and only reported effect related to the magnetic field curvature so far. Based on the analysis of interaction between the plasma and the wall, a new physical effect is proposed. The difference of magnetic field topology causes different electric potential distribution, leads to different ion flux to the wall, results in the change of sheath property and secondary electron emission, and finally affects the electron current due to near wall conductivity. This effect is further justified by the agreement between the experiment and simulation which is performed with a particle-in-cell model. Therefore, we conclude that the ion flow injection is a significant effect to near wall conductivity in the scope of curved magnetic field topology besides the magnetic mirror effect. Moreover, we find that the focus topology of magnetic field is favorable to obtain a high thruster performance from both the ion acceleration aspect and the electron conduction aspect and so is useful practically for thruster optimization.

  18. Near-field effects in Green's function retrieval from cross-correlation of elastic fields: experimental study with application to elastography.

    PubMed

    Benech, N; Brum, J; Catheline, S; Gallot, T; Negreira, C

    2013-05-01

    In a lossless system, the causal and acausal Green's function for elastic waves can be retrieved by cross-correlating the elastic field at two positions. This field, composed of converging and diverging waves, is interpreted in the frame of a time-reversal process. In this work, the near-field effects on the spatio-temporal focusing of elastic waves are analyzed through the elastodynamic Green's function. Contrary to the scalar field case, the spatial focusing is not symmetric preserving the directivity pattern of a simple source. One important feature of the spatial asymmetry is its dependency on the Poisson ratio of the solid. Additionally, it is shown that the retrieval of the bulk wave speed values is affected by diffraction. The correction factor depends on the relative direction between the source and the observed field. Experimental verification of the analysis is carried out on the volume of a soft-solid. A low-frequency diffuse-like field is generated by random impacts at the sample's free surface. The displacement field is imaged using ultrasound by a standard speckle tracking technique. One important application of this work is in the estimation of the shear elastic modulus in soft biological tissues, whose quantification can be useful in non-invasive diagnosis of various diseases. PMID:23654383

  19. Engineering of electric field distribution in GaN(cap)/AlGaN/GaN heterostructures: theoretical and experimental studies

    NASA Astrophysics Data System (ADS)

    Gladysiewicz, M.; Janicki, L.; Misiewicz, J.; Sobanska, M.; Klosek, K.; Zytkiewicz, Z. R.; Kudrawiec, R.

    2016-09-01

    Polarization engineering of GaN-based heterostructures opens a way to develop advanced transistor heterostructures, although measurement of the electric field in such heterostructures is not a simple task. In this work, contactless electroreflectance (CER) spectroscopy has been applied to measure the electric field in GaN-based heterostructures. For a set of GaN(d  =  0, 5, 15, and 30 nm)/AlGaN(20 nm)/GaN(buffer) heterostructures a decrease of electric field in the GaN(cap) layer from 0.66 MV cm‑1 to 0.27 MV cm‑1 and an increase of the electric field in the AlGaN layer from 0.57 MV cm‑1 to 0.99 MV cm‑1 have been observed with the increase in the GaN(cap) thickness from 5–30 nm. For a set of GaN(20 nm)/AlGaN(d  =  10, 20, 30, and 40 nm)/GaN(buffer) heterostructures a decrease of the electric field in the AlGaN layer from 1.77 MV cm‑1 to 0.64 MV cm‑1 and an increase of the electric field in the GaN layer from 0.57 MV cm‑1 to 0.99 MV cm‑1 were observed with the increase in the AlGaN thickness from 10–40 nm. To determine the distribution of the electric field in these heterostructures the Schrödinger and Poisson equations are solved in a self-consistent manner and matched with experimental data. It is shown that the built-in electric field in the GaN(cap) and AlGaN layers obtained from measurements does not reach values of electric field resulting only from polarization effects. The measured electric fields are smaller due to a screening of polarization effects by free carriers, which are inhomogeneously distributed across the heterostructure and accumulate at interfaces. The results clearly demonstrate that CER measurements supported by theoretical calculations are able to determine the electric field distribution in GaN-based heterostructures quantitatively, which is very important for polarization engineering in this material system.

  20. Experimental study of matrix carbon field-emission cathodes and computer aided design of electron guns for microwave power devices, exploring these cathodes

    SciTech Connect

    Grigoriev, Y.A.; Petrosyan, A.I.; Penzyakov, V.V.; Pimenov, V.G.; Rogovin, V.I.; Shesterkin, V.I.; Kudryashov, V.P.; Semyonov, V.C.

    1997-03-01

    The experimental study of matrix carbon field-emission cathodes (MCFECs), which has led to the stable operation of the cathodes with current emission values up to 100 mA, is described. A method of computer aided design of TWT electron guns (EGs) with MCFEC, based on the results of the MCFEC emission experimental study, is presented. The experimental MCFEC emission characteristics are used to define the field gain coefficient K and the cathode effective emission area S{sub eff}. The EG program computes the electric field upon the MCFEC surface, multiplies it by the K value and uses the Fowler{endash}Nordheim law and the S{sub eff} value to calculate the MCFEC current; the electron trajectories are computed as well. {copyright} {ital 1997 American Vacuum Society.}

  1. Establishment of a large semi-field system for experimental study of African malaria vector ecology and control in Tanzania

    PubMed Central

    Ferguson, Heather M; Ng'habi, Kija R; Walder, Thomas; Kadungula, Demetrius; Moore, Sarah J; Lyimo, Issa; Russell, Tanya L; Urassa, Honorathy; Mshinda, Hassan; Killeen, Gerry F; Knols, Bart GJ

    2008-01-01

    Background Medical entomologists increasingly recognize that the ability to make inferences between laboratory experiments of vector biology and epidemiological trends observed in the field is hindered by a conceptual and methodological gap occurring between these approaches which prevents hypothesis-driven empirical research from being conducted on relatively large and environmentally realistic scales. The development of Semi-Field Systems (SFS) has been proposed as the best mechanism for bridging this gap. Semi-field systems are defined as enclosed environments, ideally situated within the natural ecosystem of a target disease vector and exposed to ambient environmental conditions, in which all features necessary for its life cycle completion are present. Although the value of SFS as a research tool for malaria vector biology is gaining recognition, only a few such facilities exist worldwide and are relatively small in size (< 100 m2). Methods The establishment of a 625 m2 state-of-the-art SFS for large-scale experimentation on anopheline mosquito ecology and control within a rural area of southern Tanzania, where malaria transmission intensities are amongst the highest ever recorded, is described. Results A greenhouse frame with walls of mosquito netting and a polyethylene roof was mounted on a raised concrete platform at the Ifakara Health Institute. The interior of the SFS was divided into four separate work areas that have been set up for a variety of research activities including mass-rearing for African malaria vectors under natural conditions, high throughput evaluation of novel mosquito control and trapping techniques, short-term assays of host-seeking behaviour and olfaction, and longer-term experimental investigation of anopheline population dynamics and gene flow within a contained environment that simulates a local village domestic setting. Conclusion The SFS at Ifakara was completed and ready for use in under two years. Preliminary observations

  2. The Blacktail Creek Tuff: an analytical and experimental study of rhyolites from the Heise volcanic field, Yellowstone hotspot system

    NASA Astrophysics Data System (ADS)

    Bolte, Torsten; Holtz, Francois; Almeev, Renat; Nash, Barbara

    2015-02-01

    The magma storage conditions of the 6.62 Ma Blacktail Creek Tuff eruption, belonging to the Heise volcanic field (6.62-4.45 Ma old) of the Yellowstone hotspot system, have been investigated by combining thermobarometric and experimental approaches. The results from different geothermometers (e.g., Fe-Ti oxides, feldspar pairs, apatite and zircon solubility, and Ti in quartz) indicate a pre-eruptive temperature in the range 825-875 °C. The temperature estimated using two-pyroxene pairs varies in a range of 810-950 °C, but the pyroxenes are probably not in equilibrium with each other, and the analytical results of melt inclusion in pyroxenes indicate a complex history for clinopyroxene, which hosts two compositionally different inclusion types. One natural Blacktail Creek Tuff rock sample has been used to determine experimentally the equilibrium phase assemblages in the pressure range 100-500 MPa and a water activity range 0.1-1.0. The experiments have been performed at fluid-present conditions, with a fluid phase composed of H2O and CO2, as well as at fluid-absent conditions. The stability of the quartzo-feldspathic phases is similar in both types of experiments, but the presence of mafic minerals such as biotite and clinopyroxene is strongly dependent on the experimental approach. Possible explanations are given for this discrepancy which may have strong impacts on the choice of appropriate experimental approaches for the determination of magma storage conditions. The comparison of the composition of natural phases and of experimentally synthesized phases confirms magma storage temperatures of 845-875 °C. Melt water contents of 1.5-2.5 wt% H2O are required to reproduce the natural Blacktail Creek Tuff mineral assemblage at these temperatures. Using the Ti-in-quartz barometer and the Qz-Ab-Or proportions of natural matrix glasses, coexisting with quartz, plagioclase and sanidine, the depth of magma storage is estimated to be in a pressure range between 130 and

  3. Magnetohydrodynamic generator experimental studies

    NASA Technical Reports Server (NTRS)

    Pierson, E. S.

    1972-01-01

    The results for an experimental study of a one wavelength MHD induction generator operating on a liquid flow are presented. First the design philosophy and the experimental generator design are summarized, including a description of the flow loop and instrumentation. Next a Fourier series method of treating the fact that the magnetic flux density produced by the stator is not a pure traveling sinusoid is described and some results summarized. This approach appears to be of interest after revisions are made, but the initial results are not accurate. Finally, some of the experimental data is summarized for various methods of excitation.

  4. Theoretical and experimental studies of electric field distribution in N-polar GaN/AlGaN/GaN heterostructures

    SciTech Connect

    Gladysiewicz, M. Janicki, L.; Kudrawiec, R.; Siekacz, M.; Cywinski, G.

    2015-12-28

    Electric field distribution in N-polar GaN(channel)/AlGaN/GaN(buffer) heterostructures was studied theoretically by solving Schrodinger and Poisson equations in a self-consistent manner for various boundary conditions and comparing results of these calculations with experimental data, i.e., measurements of electric field in GaN(channel) and AlGaN layers by electromodulation spectroscopy. A very good agreement between theoretical calculations and experimental data has been found for the Fermi-level located at ∼0.3 eV below the conduction band at N-polar GaN surface. With this surface boundary condition, the electric field distribution and two dimensional electron gas concentration are determined for GaN(channel)/AlGaN/GaN(buffer) heterostructures of various thicknesses of GaN(channel) and AlGaN layers.

  5. An experimental study of the effect of magnet length on the performance of a multi-cusped field thruster

    NASA Astrophysics Data System (ADS)

    Hu, Peng; Liu, Hui; Gao, Yuanyuan; Mao, Wei; Yu, Daren

    2016-07-01

    The multi-cusped field thruster is a novel concept in electric propulsion, which employs alternating permanent polarity magnets to create a periodic magnetic field. As an important factor for the optimal design, the magnet length of a low-power thruster is designed to be changeable. The effects of the ultimate stage length (L u) and the middle stage length (L m) on the performance characteristics are studied in a series of experiments. The results show that increasing L u could prolong the axial motion range of the electrons and promote the ionization process. In addition, it can enlarge the relative distance between the ionization and the acceleration regions. Both of these aspects can help improve the thrust and the anode efficiency. With regard to he reverse trend, wefound that the longer L m leads to a reduction of the thruster’s performance for the enhanced ion loss to the wall. Overall this study can provide some optimal design ideas on the magnet length to improve the total performance of the multi-cusped field thruster.

  6. The effects of beliefs regarding drug assignment in experimental and field studies of nicotine delivery devices: a review.

    PubMed

    Dar, Reuven; Barrett, Sean P

    2014-11-01

    The placebo effect of a psychoactive drug can be defined as the effect of expecting the drug in the absence of its pharmacological actions. As nicotine is widely believed to be the primary factor driving cigarette smoking, smokers are likely to expect nicotine to alleviate craving and withdrawal. The present review examines the extent to which any observed effects of nicotine, and especially its craving- and withdrawal-reducing effects, can be attributed to placebo. We begin by reviewing studies that examined the placebo effects of nicotine in the laboratory and follow with a review of potential placebo effects that are typically not controlled in placebo-controlled studies of nicotine replacement therapy (NRT). In laboratory studies, nicotine instructions decrease tobacco smoking, craving and/or withdrawal, while nicotine-specific effects have not been consistently reported. In field trials of NRT, there is a general failure to assess smokers' beliefs regarding their drug assignment. This omission makes it difficult to unequivocally attribute findings of placebo-controlled NRT studies to the physiological effects of nicotine. In sum, our review indicates that the placebo effects of nicotine, and specifically nicotine content expectations, may account for many of the benefits associated with nicotine delivery devices in both laboratory and field studies. PMID:25253274

  7. Lethal effects of experimental warming approximating a future climate scenario on southern African quartz-field succulents: a pilot study.

    PubMed

    Musil, Charles F; Schmiedel, Ute; Midgley, Guy F

    2005-02-01

    Here we examine the response of succulents in a global biodiversity hot spot to experimental warming consistent with a future African climate scenario. Passive daytime warming (averaging 5.5 degrees C above ambient) of the natural vegetation was achieved with 18 transparent hexagonal open-top chamber arrays randomized in three different quartz-field communities. After 4-months summer treatment, the specialized-dwarf and shrubby succulents displayed between 2.1 and 4.9 times greater plant and canopy mortalities in the open-top chambers than in the control plots. Those surviving in cooler ventilated areas and shaded refuges in the chambers had lower starch concentrations and water contents; the shrubby succulents also exhibited diminished chlorophyll concentrations. It is concluded that current thermal regimes are likely to be closely proximate to tolerable extremes for many endemic succulents in the region, and that anthropogenic warming could significantly exceed their thermal thresholds. Further investigation is required to elucidate the importance of associated moisture deficits in these warming experiments, a potential consequence of supplementary (fog and dew) precipitation interception by open-top chambers and higher evaporation therein, on plant mortalities. PMID:15720664

  8. An experimental study of the flow field surrounding a subsonic jet in a cross flow. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Dennis, Robert Foster

    1993-01-01

    An experimental investigation of the flow interaction of a 5.08 cm (2.00 in.) diameter round subsonic jet exhausting perpendicularly to a flat plate in a subsonic cross flow was conducted in the NASA Ames 7x1O ft. Wind Tunnel Number One. Flat plate surface pressures were measured at 400 locations in a 30.48 cm (12.0 in.) concentric circular array surrounding the jet exit. Results from these measurements are provided in tabular and graphical form for jet-to-crossflow velocity ratios ranging from 4 to 12, and for jet exit Mach numbers ranging from 0.50 to 0.93. Laser doppler velocimeter (LDV) three component velocity measurements were made in selected regions in the developed jet plume and near the flat plate surface, at a jet Mach number of 0.50 and jet-to-crossflow velocity ratios of 6 and 8. The results of both pressure and LDV measurements are compared with the results of previous experiments. In addition, pictures of the jet plume shape at jet velocity ratios ranging from 4 to 12 were obtained using schleiren photography. The LDV measurements are consistent with previous work, but more extensive measurements will be necessary to provide a detailed picture of the flow field. The surface pressure results compare closely with previous work and provide a useful characterization of jet induced surface pressures. The results demonstrate the primary influence of jet velocity ratio and the secondary influence of jet Mach number in determining such surface pressures.

  9. Collective Experimentation: Lessons from the Field

    ERIC Educational Resources Information Center

    Misiko, M.

    2009-01-01

    The purpose of this paper is to document smallholder experiences during a participatory experimental initiative and draw useful lessons for field practitioners. The main methods used to collect data were participant observation, in-depth interviews among 40 farmers, and analyses of notes taken during participatory monitoring and evaluation. These…

  10. An Experimental Study of Continuous Plasma Flows Driven by a Confined Arc in a Transverse Magnetic Field

    NASA Technical Reports Server (NTRS)

    Barger, R. L.; Brooks, J. D.; Beasley, W. D.

    1961-01-01

    A crossed-field, continuous-flow plasma accelerator has been built and operated. The highest measured velocity of the flow, which was driven by the interaction of the electric and magnetic fields, was about 500 meters per second. Some of the problems discussed are ion slip, stability and uniformity of the discharge, effect of the magnetic field on electron emission, use of preionization, and electrode contamination.

  11. Experimental studies on power frequency breakdown voltage of CF3I/N2 mixed gas under different electric fields

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoxing; Xiao, Song; Han, Yefei; Cressault, Yann

    2016-02-01

    To verify the feasibility of replacing SF6 by CF3I/N2, we compared their power frequency breakdown performance with the influence of gas pressure, mixing ratio, and electric field utilization coefficient. Under different electric fields and mixing ratios, the power frequency breakdown voltage of CF3I/N2 increases linearly along with gas pressure. Besides, with the rise of the electric field utilization coefficient, the linear growth rate of breakdown voltage along with gas pressure gradually rises. The sensitivity of pure CF3I to electric field is particularly high and can be improved by the addition of N2. The mixture 30% CF3I/70% N2 at 0.3 MPa could replace pure SF6 in equipment requiring a low insulation, but the gas pressure or the content of CF3I need to be increased for higher insulation requirements.

  12. Effects of Experimental Learning--Outcomes of an Empirical Study in the Vocational Field of Structural Engineering

    ERIC Educational Resources Information Center

    Bünning, Frank

    2013-01-01

    Pedagogic approaches to TVET offer a limited range of teaching strategies which make use of experimental learning. Thus experiments were developed for teachers of structural engineering and timber processing technologies and were subject to empirical evaluation by a researcher at the Otto-von-Guericke-University Magdeburg and Kassel University.…

  13. Divergent effects of urban particulate air pollution on allergic airway responses in experimental asthma: a comparison of field exposure studies

    PubMed Central

    2012-01-01

    Background Increases in ambient particulate matter of aerodynamic diameter of 2.5 μm (PM2.5) are associated with asthma morbidity and mortality. The overall objective of this study was to test the hypothesis that PM2.5 derived from two distinct urban U.S. communities would induce variable responses to aggravate airway symptoms during experimental asthma. Methods We used a mobile laboratory to conduct community-based inhalation exposures to laboratory rats with ovalbumin-induced allergic airways disease. In Grand Rapids exposures were conducted within 60 m of a major roadway, whereas the Detroit was located in an industrial area more than 400 m from roadways. Immediately after nasal allergen challenge, Brown Norway rats were exposed by whole body inhalation to either concentrated air particles (CAPs) or filtered air for 8 h (7:00 AM - 3:00 PM). Both ambient and concentrated PM2.5 was assessed for mass, size fractionation, and major component analyses, and trace element content. Sixteen hours after exposures, bronchoalveolar lavage fluid (BALF) and lung lobes were collected and evaluated for airway inflammatory and mucus responses. Results Similar CAPs mass concentrations were generated in Detroit (542 μg/m3) and Grand Rapids (519 μg/m3). Exposure to CAPs at either site had no effects in lungs of non-allergic rats. In contrast, asthmatic rats had 200% increases in airway mucus and had more BALF neutrophils (250% increase), eosinophils (90%), and total protein (300%) compared to controls. Exposure to Detroit CAPs enhanced all allergic inflammatory endpoints by 30-100%, whereas inhalation of Grand Rapids CAPs suppressed all allergic responses by 50%. Detroit CAPs were characterized by high sulfate, smaller sized particles and were derived from local combustion sources. Conversely Grand Rapids CAPs were derived primarily from motor vehicle sources. Conclusions Despite inhalation exposure to the same mass concentration of urban PM2.5, disparate health

  14. Theoretical and experimental study of high-magnetic-field XMCD spectra at the L2,3 absorption edges of mixed-valence rare-earth compounds

    NASA Astrophysics Data System (ADS)

    Kotani, Akio; Matsuda, Yasuhiro H.; Nojiri, Hiroyuki

    2009-11-01

    X-ray magnetic circular dichroism(XMCD) spectra at the L2,3 edges of mixed-valence rare-earth compounds in high magnetic fields are studied both theoretically and experimentally. The theoretical study is based on a new framework proposed recently by Kotani. The Zeeman splitting of 4f states, the mixed-valence character of 4f states, and the 4f-5d exchange interaction are incorporated into a single impurity Anderson model. New XMCD experiments in high magnetic fields up to 40 T are carried out for the mixed-valence compounds EuNi2(Si0.18Ge0.82)2 and YbInCu4 by using a miniature pulsed magnet, which was developed recently by Matsuda et al. The XMCD data are taken at 5 K by transmission measurements for incident X-rays with ± helicities at BL39XU in SPring-8. After giving a survey on recent developments in the theory of XMCD spectra for mixed-valence Ce and Yb compounds, we calculate the XMCD spectra of YbInCu4 at the field-induced valence transition around 32 T by applying the recent theoretical framework and by newly introducing at 32 T a discontinuous change in the Yb 4f level and that in the hybridization strength between the Yb 4f and conduction electrons. The calculated results are compared with the experimental ones.

  15. An experimental study on the effects of tip clearance on flow field and losses in an axial flow compressor rotor

    NASA Technical Reports Server (NTRS)

    Lakshminarayana, B.; Zhang, J.; Murthy, K. N. S.

    1987-01-01

    Detailed measurement of the flow field in the tip region of a compressor rotor was carried out using a Laser Doppler Velocimeter (LDV) and a Kiel probe at two different tip clearance heights. At both clearance sizes, the relative stagnation pressure and the axial and tangential components of relative velocities were measured upstream, inside the passage and downstream of the rotor, up to about 20 percent of the blade span from the annulus wall. The velocities, outlet angles, losses, momentum thickness, and force defect thickness are compared for the two clearances. A detailed interpretation of the effect of tip clearance on the flow field is given. There are substantial differences in flow field, on momentum thickness, and performance as the clearance is varied. The losses increase linearly within the passage and their values increase in direct proportion to tip clearance height. No discernable vortex (discrete) is observed downstream of the rotor.

  16. The Impact of Global Warming on the Carbon Cycle of Arctic Permafrost: An Experimental and Field Based Study

    SciTech Connect

    Onstott, Tullis C; Pffifner, Susan M; Chourey, Karuna

    2014-11-07

    Our results to date indicate that CO2 and CH4 fluxes from organic poor, Arctic cryosols on Axel Heiberg Island are net CH4 sinks and CO2 emitters in contrast to organic-rich peat deposits at sub-Arctic latitudes. This is based upon field observations and a 1.5 year long thawing experiment performed upon one meter long intact cores. The results of the core thawing experiments are in good agreement with field measurements. Metagenomic, metatranscriptomic and metaproteomic analyses indicate that high affinity aerobic methanotrophs belong to the uncultivated USCalpha are present in <1% abundance in these cryosols are are active in the field during the summer and in the core thawing experiments. The methanotrophs are 100 times more abundant than the methanogens. As a result mineral cryosols, which comprise 87% of Arctic tundra, are net methane sinks. Their presence and activity may account for the discrepancies observed between the atmospheric methane concentrations observed in the Arctic predicted by climate models and the observed seasonal fluctuations and decadal trends. This has not been done yet.

  17. Ant-App-DB: a smart solution for monitoring arthropods activities, experimental data management and solar calculations without GPS in behavioral field studies.

    PubMed

    Ahmed, Zeeshan; Zeeshan, Saman; Fleischmann, Pauline; Rössler, Wolfgang; Dandekar, Thomas

    2014-01-01

    Field studies on arthropod ecology and behaviour require simple and robust monitoring tools, preferably with direct access to an integrated database. We have developed and here present a database tool allowing smart-phone based monitoring of arthropods. This smart phone application provides an easy solution to collect, manage and process the data in the field which has been a very difficult task for field biologists using traditional methods. To monitor our example species, the desert ant Cataglyphis fortis, we considered behavior, nest search runs, feeding habits and path segmentations including detailed information on solar position and azimuth calculation, ant orientation and time of day. For this we established a user friendly database system integrating the Ant-App-DB with a smart phone and tablet application, combining experimental data manipulation with data management and providing solar position and timing estimations without any GPS or GIS system. Moreover, the new desktop application Dataplus allows efficient data extraction and conversion from smart phone application to personal computers, for further ecological data analysis and sharing. All features, software code and database as well as Dataplus application are made available completely free of charge and sufficiently generic to be easily adapted to other field monitoring studies on arthropods or other migratory organisms. The software applications Ant-App-DB and Dataplus described here are developed using the Android SDK, Java, XML, C# and SQLite Database. PMID:25977753

  18. Ant-App-DB: a smart solution for monitoring arthropods activities, experimental data management and solar calculations without GPS in behavioral field studies

    PubMed Central

    Ahmed, Zeeshan; Zeeshan, Saman; Fleischmann, Pauline; Rössler, Wolfgang; Dandekar, Thomas

    2015-01-01

    Field studies on arthropod ecology and behaviour require simple and robust monitoring tools, preferably with direct access to an integrated database. We have developed and here present a database tool allowing smart-phone based monitoring of arthropods. This smart phone application provides an easy solution to collect, manage and process the data in the field which has been a very difficult task for field biologists using traditional methods. To monitor our example species, the desert ant Cataglyphis fortis, we considered behavior, nest search runs, feeding habits and path segmentations including detailed information on solar position and azimuth calculation, ant orientation and time of day. For this we established a user friendly database system integrating the Ant-App-DB with a smart phone and tablet application, combining experimental data manipulation with data management and providing solar position and timing estimations without any GPS or GIS system. Moreover, the new desktop application Dataplus allows efficient data extraction and conversion from smart phone application to personal computers, for further ecological data analysis and sharing. All features, software code and database as well as Dataplus application are made available completely free of charge and sufficiently generic to be easily adapted to other field monitoring studies on arthropods or other migratory organisms. The software applications Ant-App-DB and Dataplus described here are developed using the Android SDK, Java, XML, C# and SQLite Database. PMID:25977753

  19. Experimental study of the ponderomotive effects of a large amplitude microwave field on a magnetized electron beam

    SciTech Connect

    Hadjoudj, Y.; Pierre, T.; Heuraux, S.; Leclert, G.

    1995-11-01

    Charged particles propagating in an inhomogeneous large amplitude microwave field experience a nonlinear force called the ponderomotive force. This effect can be theoretically evaluated either from the single particle or the fluid theories. For magnetized particles, these two descriptions predict quite different behaviors. A previous experiment [J. Vaclavik {ital et} {ital al}., Phys. Fluids {bold 29}, 2034 (1986)] has shown results in agreement with the fluid theory. Here, an experiment with a magnetized electron beam is described, which brings out a ponderomotive deflection in agreement with the single particle theory. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  20. Experimental and numerical study of pollution process in an aquifer in relation to a garbage dump field

    NASA Astrophysics Data System (ADS)

    Changli, Liu; Feng-E, Zhang; Yun, Zhang; Shuhong, Song; Sheng, Zhang; Hao, Ye; Hongbing, Hou; Lijuan, Yang; Ming, Zhang

    2005-10-01

    The water quality of shallow aquifers that have direct relationship to human heath and ecological safety has been seriously threatened by widespread dumping of industrial solid waste, urban and rural garbage. A garbage dump field with hydrogeological, environ-geological characteristics typical of the Beijing plain was selected for investigation. A hydrogeological model was constructed and the equations used to describe pollutant transport in one-dimensional (1D) steady, uniform groundwater flow to investigate the transport/diffusion processes. In addition to the coefficients for calculation, diffusion coefficient and other coefficients of the aquifer were obtained by conducting in situ diffusion experiments and sample tests. Velocity and scope of pollutant transport/diffusion process were calculated. Accordingly, the real pollution situation in the aquifer was evaluated through in situ drilling and sample testing. Transport/diffusion processes of pollutants within the aquifer abide by the solute equation applicable to 1D steady flow. The transport and diffusion dominate in the direction of groundwater flowing at a speed of about 120 m per year. Comparably, the lateral diffusive width is much smaller. Pollution degree decreases by the law of Y=1.08 exp(33.533/ X), where Y is the distance from the garbage dump field and X is the overall pollution index.

  1. Experimental study on vertical scaling of InAs-on-insulator metal-oxide-semiconductor field-effect transistors

    SciTech Connect

    Kim, SangHyeon E-mail: sh-kim@kist.re.kr; Yokoyama, Masafumi; Nakane, Ryosho; Takenaka, Mitsuru; Takagi, Shinichi; Ichikawa, Osamu; Osada, Takenori; Hata, Masahiko

    2014-06-30

    We have investigated effects of the vertical scaling on electrical properties in extremely thin-body InAs-on-insulator (-OI) metal-oxide-semiconductor field-effect transistors (MOSFETs). It is found that the body thickness (T{sub body}) scaling provides better short channel effect (SCE) control, whereas the T{sub body} scaling also causes the reduction of the mobility limited by channel thickness fluctuation (δT{sub body}) scattering (μ{sub fluctuation}). Also, in order to achieve better SCEs control, the thickness of InAs channel layer (T{sub channel}) scaling is more favorable than the thickness of MOS interface buffer layer (T{sub buffer}) scaling from a viewpoint of a balance between SCEs control and μ{sub fluctuation} reduction. These results indicate necessity of quantum well channel structure in InAs-OI MOSFETs and these should be considered in future transistor design.

  2. An experimental and numerical study of the urban wind field at the university site Tübingen

    NASA Astrophysics Data System (ADS)

    El Bahlouli, Asmae; Bange, Jens

    2015-04-01

    This study examines the wind energy potential close to energy consumers inside cities, i.e. between buildings at the university site in the city of Tübingen. The study area is characterized by cubic shaped buildings, related to the university and located on top of a hill in an outlying district in the city of Tübingen. A majority of the buildings is higher than 20 meters with 3 of them around 50 meters. This investigation combines a full-scale experiment and a numerical study. A common technique to calculate the energy potential includes wind measurements at least for an annual cycle. For our study, the measurement campaign started in April 2014 and should last until mid of 2015. Six stations with sonic anemometers were installed. These anemometers are providing measurements of wind speed and wind direction with a high temporal resolution (10 Hz). On the one hand, the measured data are used for a determination of the inflow boundary conditions for our simulations. On the other hand, the wind data will be used to verify the numerical model inside the domain. A wide variety of numerical simulations based on Reynolds Averaged Navier-Stokes Equations (RANS) and large eddy simulation (LES) models have been conducted (cf. Tutar and Oguz (2002)). From these numerical studies it has been concluded that the LES approach seems to be more suitable for studies of airflows around buildings. Consequently we decided to conduct our calculations by means of a LES using OpenFOAM software. This study will help us to identify locations with the most qualified conditions for producing electrical energy using small building-mounted wind turbines. Tutar, M., Oguz, G. (2002). Large eddy simulation of flow around parallel buildings with varying configurations. Fluid Dynamic Research 31, p289-315.

  3. Experimental and Computational Studies of the Control of Convection of Non-Conducting Liquids During solidification by Means of a Magnetic Field Gradient

    NASA Technical Reports Server (NTRS)

    Seybert, C. D.; Evans, J. W.; Leslie, F.; Jones, W. K., Jr.

    2001-01-01

    The elimination of convection is essential in experimental investigations of diffusive transport (of heat and matter) during solidification. One classical approach to damping convection in a conducting liquid is the application of a magnetic field. The damping phenomenon is the induction, by the motion of a conductor in a magnetic field, of currents which interact with the field to produce Lorentz forces that oppose the flow. However, there are many liquids which are not sufficiently conducting to exploit this phenomenon; examples include the transparent liquids (such as succinonitrile-acetone) that are used as "model alloys" in fundamental solidification studies. There have been several investigations of the solidification of these liquids that have been carried out in orbiting laboratories to eliminate natural convection. The paper describes an investigation of an alternative approach whereby a magnetic field gradient is applied to the liquid. A magnetic body force then arises which is dependent on the susceptibility of the liquid and thereby on the temperature and or concentration. With the field gradient aligned vertically and of correct magnitude, the variation of gravitational body force due to temperature/concentration dependent density can be counterbalanced by a variation in magnetic body force. Experiments have been carried out in a super-conducting magnet at Marshall Space Flight Center to measure velocities in an aqueous manganese chloride solution. The solution was contained in a chamber with temperature controlled end walls and glass side walls. Velocities were measured by particle image velocimetry. Starting from zero current in the magnet (zero field gradient) flow driven by the temperature difference between the end walls was measured. At a critical current the flow was halted. At higher currents the normal convection was reversed. The experiments included ones where the solution was solidified and were accompanied by solution of the flow

  4. An experimental study into the influence of aquatic plant motion characteristics on the generation of a fluvial turbulent flow field

    NASA Astrophysics Data System (ADS)

    Hardy, R. J.; Marjoribanks, T.; Parsons, D. R.; Thomas, R. E.

    2015-12-01

    Aquatic vegetation has a determining effect on flow and consequently sediment transport as it generates both skin friction and form drag. The measurement of flow above the vegetation canopy has received much attention and there is now a good process understanding of mean and turbulent flow, although, much of this research has focused on rigid vegetation with relatively simple morphology. However, vegetation immersed in a flow experiences several forces (buoyancy; drag; virtual mass; Basset; and Saffman) which are counteracted by the properties of the vegetation (flexural rigidity; modulus of elasticity; the plant area exposed to the flow and; the packing density of the stems). The ratio of these forces determines the plant motion characteristics which are generally classified as either i) erect with no movement; ii) gently swaying; iii) strong, coherent swaying or; iv) prone. Here we report on an investigation into the influence of plant motion on the turbulence structure in the mixing zone as vortices in this region have been shown to account for the majority of the momentum transport between the canopy and the open flow. We report on a series of flume experiments where flow over a canopy of surrogate aquatic vegetation was measured using PIV at a spatial resolution of ~1mm2 and at a temporal resolution of 100 Hz. This provided whole flow field measurements for all three components of flow over the vegetation canopy. Plant motion characteristics were altered by modifying the flow Reynolds number through both velocity and depth. The influences of plant stem length were also assessed. The measured flows were analysed by standard Reynolds decomposition approaches and Eulerian and Lagrangian coherent flow structure identification methods. Kelvin-Helmholtz and Görtler-type vortices were identified within the canopy shear layer that are generated close to the canopy top and evolve downstream into span-wise roller vortices, which expand with both distance and time. When

  5. Experimental Study to Produce Multiple Focal Points of Acoustic Field for Active Path Selection of Microbubbles through Multi-bifurcation

    NASA Astrophysics Data System (ADS)

    Koda, Ren; Koido, Jun; Ito, Takumi; Mochizuki, Takashi; Masuda, Kohji; Ikeda, Seiichi; Arai, Fumihito; Miyamoto, Yoshitaka; Chiba, Toshio

    2013-07-01

    We previously reported our attempt to propel microbubbles in a flow by a primary Bjerknes force, which is a physical phenomenon where an acoustic wave pushes an obstacle along its direction of propagation. However, when ultrasound was emitted from the surface of the body, controlling bubbles in an against-flow was necessary. It is unpractical to use multiple transducers to produce the same number of focal points because single-element transducers cannot produce more than two focal points. In this study, we introduced a complex artificial blood vessel according to a capillary model and a two-dimensional (2D) array transducer to produce multiple focal points for the active control of microbubbles in an against-flow. From the results, about 15% more microbubbles were led to the desired path with multiple focal points of ultrasound relative to the no-emission case.

  6. Experimental results for a hypersonic nozzle/afterbody flow field

    NASA Technical Reports Server (NTRS)

    Spaid, Frank W.; Keener, Earl R.; Hui, Frank C. L.

    1995-01-01

    This study was conducted to experimentally characterize the flow field created by the interaction of a single-expansion ramp-nozzle (SERN) flow with a hypersonic external stream. Data were obtained from a generic nozzle/afterbody model in the 3.5 Foot Hypersonic Wind Tunnel at the NASA Ames Research Center, in a cooperative experimental program involving Ames and McDonnell Douglas Aerospace. The model design and test planning were performed in close cooperation with members of the Ames computational fluid dynamics (CFD) team for the National Aerospace Plane (NASP) program. This paper presents experimental results consisting of oil-flow and shadow graph flow-visualization photographs, afterbody surface-pressure distributions, rake boundary-layer measurements, Preston-tube skin-friction measurements, and flow field surveys with five-hole and thermocouple probes. The probe data consist of impact pressure, flow direction, and total temperature profiles in the interaction flow field.

  7. Health responses to a new high-voltage power line route: design of a quasi-experimental prospective field study in the Netherlands

    PubMed Central

    2014-01-01

    Background New high-voltage power transmission lines will be introduced due to increasing demand for reliable and renewable energy supplies. Some residents associate non-specific health complaints with exposure to electromagnetic fields from nearby power lines. This study protocol describes the design and rationale of a prospective study investigating whether the introduction of a new power line triggers health responses in residents living nearby. Methods/Design The study is designed as a quasi-experimental field study with two pretests during the construction of a new power line route, and two posttests after it has been put into operation. Key outcomes are self-reported non-specific somatic and cognitive health complaints, and attribution of these health complaints to a power line. The main determinant is proximity to the new power line route. One member of every household (n = 2379) residing in close proximity (0-500 meters) to the overhead parts of a new power line route in the Netherlands is invited to participate, as well as a sample of household members (n = 2382) residing farther away (500-2000 meters). Multilevel analysis will be employed to test whether an increase in key outcome measures is related to proximity to the line. Longitudinal structural equation models will be applied to test to what extent health responses are mediated by psychosocial health mechanisms and moderated by negative oriented personality traits. Discussion This is the first study to investigate health responses to a new power line route in a prospective manner. The results will provide theoretical insight into psychosocial mechanisms operating during the introduction of an environmental health risk, and may offer suggestions to policymakers and other stakeholders for minimizing adverse health responses when introducing new high-voltage power lines. PMID:24606914

  8. Theoretical and Experimental Studies of the Transonic Flow Field and Associated Boundary Conditions near a Longitudinally-Slotted Wind-Tunnel Wall. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Everhart, Joel Lee

    1988-01-01

    A theoretical examination of the slotted-wall flow field is conducted to determine the appropriate wall pressure drop (or boundary condition) equation. This analysis improves the understanding of the fluid physics of these types of flow fields and helps in evaluating the uncertainties and limitations existing in previous mathematical developments. It is shown that the resulting slotted-wall boundary condition contains contributions from the airfoil-induced streamline curvature and the non-linear, quadratic, slot crossflow in addition to an often neglected linear term which results from viscous shearing in the slot. Existing and newly acquired experimental data are examined in the light of this formulation and theoretical developments.

  9. Numerical modeling and experimental study of motion-induced remote field current effect and its applications to online inspection and quality examination of rolling metallic strips

    NASA Astrophysics Data System (ADS)

    Sun, Yushi; Udpa, Satish S.; Lord, William; Udpa, Lalita; Ouyang, Tianhe

    2000-06-01

    Currently, rolled metallic strips and sheets are inspected off-line, which is costly, time consuming and not ideal for quality control. A well designed online diagnostic and control system for metal rolling process may largely reduce cost, improve quality, and hence enhance competitiveness of the product. The overall objective of this paper is to study a new nondestructive measurement system for on-line diagnostics and control of metallic rolling process using motion-induced remote-field eddy-current (MIRFEC) effect. The system can be used to monitor in real time the rolled metallic strips/sheets for possible anomalies, inclusions, voids, bubbles, lamination, as well as measuring variations of its properties. The potential advantages of the MIRFEC system include simplicity, robustness, low cost, high reliability, quick and accurate signal classification and characterization that can used for real-time process control, or off-line data analysis. The technique also allows operation at high temperature, large lift-off and vibration, and high rolling speed. Results of finite element modeling of the MIRFEC effect and experimental measurement data obtained from a prototype system are presented.

  10. Transient rheological behavior of natural polysaccharide xanthan gum solutions in start-up shear flow fields: An experimental study using a strain-controlled rheometer

    NASA Astrophysics Data System (ADS)

    Lee, Ji-Seok; Kim, Yong-Seok; Song, Ki-Won

    2015-08-01

    The objective of the present study is to experimentally investigate the transient rheological behavior of concentrated xanthan gum solutions in start-up shear flow fields. Using a strain-controlled rheometer, a number of constant shear rates were suddenly imposed to aqueous xanthan gum solutions with different concentrations and the resultant shear stress responses were measured with time. The main findings obtained from this study can be summarized as follows: (1) For all shear rates imposed, however low it may be, the shear stress is rapidly increased with time (stress overshoot) upon inception of steady shear flow before passing through the maximum stress value and then gradually decreased with time (stress decay) until reaching a steady state flow. (2) As the imposed shear rate is increased, a more pronounced stress overshoot takes place and the maximum stress value becomes larger, whereas both times at which the maximum stress is observed and needed to reach a steady state flow are shortened. (3) The maximum shear stress is linearly increased with shear rate in a double logarithmic scale and becomes larger with increasing concentration at equal shear rates. In addition, the time at which the maximum stress occurs exhibits a linear relationship with the inverse of shear rate in a double logarithmic scale for all xanthan gum solutions, regardless of their concentrations. (4) The shear stress is sharply increased with an increase in strain until reaching the maximum stress at small range of deformations. The maximum stress is observed at similar strain values, irrespective of the imposed shear rates lower than 10 1/s. (5) The Bird-Leider model can be successfully used with regard to quantitatively predicting the transient behavior of concentrated xanthan gum solutions. However, this model has a fatal weakness in terms of describing a decrease in shear stress (stress decay).

  11. Experimental Study on Improving Unclamped Inductive Switching Characteristics of the New Power Metal Oxide Semiconductor Field Effect Transistor Employing Deep Body Contact

    NASA Astrophysics Data System (ADS)

    Ji, In‑Hwan; Choi, Young‑Hwan; Kim, Soo‑Seong; Choi, Yearn‑Ik; Han, Min‑Koo

    2006-04-01

    A new power metal oxide semiconductor field effect transistor (MOSFET) with deep body contact (DBC), which improves the avalanche energy capability, is proposed and verified by experimental results. For the experiment, a 60 V, 1 A power MOSFET employing DBC has been fabricated using a complementary metal oxide semiconductor (CMOS) compatible deep Si trench process. Previous simulations show that DBC alters the direction of the current flow from the edge to the bottom of the p-body under unclamped inductive switching (UIS) conditions. DBC also suppresses the activation of the parasitic bipolar transistor due to the reduction of the current density beneath the n+ source. Experimental results show that the ruggedness of the proposed power MOSFET is improved without sacrificing any other electrical characteristics and increasing device area.

  12. Experimental Studies on Biosensing by SPR

    NASA Astrophysics Data System (ADS)

    Sun, Xiaochun; Shiokawa, Showko; Matsui, Yosikazu

    1989-09-01

    Biosensing using surface plasmon resonance is experimentally studied. The results obtained by detecting the bioresponse of the α-Feto protein system and cyclic experiments show that this technique has potential application in the field of biosensing. The effects of an organic layer on detecting sensitivity and restoration of sensors are also discussed.

  13. Profiling of energy deposition fields in a modular HTHR with annular core: Computational/experimental studies at the ASTRA critical facility

    SciTech Connect

    Boyarinov, V. F.; Garin, V. P.; Glushkov, E. S.; Zimin, A. A.; Kompaniets, G. V.; Nevinitsa, V. A.; Polyakov, D. N.; Ponomarev, A. S.; Ponomarev-Stepnoi, N. N.; Smirnov, O. N.; Fomichenko, P. A.; Chunyaev, E. I.; Marova, E. V.; Sukharev, Yu. P.

    2010-12-15

    The paper presents the results obtained from the computational/experimental studies of the spatial distribution of the {sup 235}U fission reaction rate in a critical assembly with an annular core and poison profiling elements inserted into the inner graphite reflector. The computational analysis was carried out with the codes intended for design computation of an HTHR-type reactor.

  14. Towards experimental quantum-field tomography with ultracold atoms

    PubMed Central

    Steffens, A.; Friesdorf, M.; Langen, T.; Rauer, B.; Schweigler, T.; Hübener, R.; Schmiedmayer, J.; Riofrío, C.A.; Eisert, J.

    2015-01-01

    The experimental realization of large-scale many-body systems in atomic-optical architectures has seen immense progress in recent years, rendering full tomography tools for state identification inefficient, especially for continuous systems. To work with these emerging physical platforms, new technologies for state identification are required. Here we present first steps towards efficient experimental quantum-field tomography. Our procedure is based on the continuous analogues of matrix-product states, ubiquitous in condensed-matter theory. These states naturally incorporate the locality present in realistic physical settings and are thus prime candidates for describing the physics of locally interacting quantum fields. To experimentally demonstrate the power of our procedure, we quench a one-dimensional Bose gas by a transversal split and use our method for a partial quantum-field reconstruction of the far-from-equilibrium states of this system. We expect our technique to play an important role in future studies of continuous quantum many-body systems. PMID:26138511

  15. Experimental Infrasound Studies in Nevada

    NASA Astrophysics Data System (ADS)

    Herrin, E. T.; Negraru, P. T.; Golden, P.; Williams, A.

    2009-12-01

    An experimental propagation study was carried out in Nevada in June 2009 on Julian days 173-177. During this field experiment we deployed 16 single channel digital infrasound recorders to monitor the munitions disposal activities near Hawthorne, NV. The sensors were deployed in a single line and placed approximately 12 km apart at distances ranging from 2 to 177 km. A four element semi-permanent infrasound array named FNIAR was installed approximately 154 km north of the detonation site in line with the individual temporary recorders. Tropospheric arrivals were observed during all days of the experiment, but during day 176 the observed arrivals had very large amplitudes. A large signal was observed at 58 km from the detonation site with amplitude as large as 4 Pascals, while at 94 km no signal was observed. At FNIAR the amplitude of the tropospheric arrival was 1 Pascal. During this day meteorological data acquired in the propagation path showed a strong jet stream to the north. On day 177 we were not able to identify tropospheric arrivals beyond 34 km, but at stations beyond 152 km we observed stratospheric arrivals. Continuous monitoring of these signals at FNIAR shows that stratospheric arrivals are the most numerous. In a two month period, from 06/15/2009 to 08/15/2009 there were 35 operational days at the Hawthorne disposal facility resulting in 212 explosions with known origin times. Based on the celerity values there were 115 explosions that have only stratospheric arrivals (celerities of 300-275 m/s), 72 explosions with both tropospheric (celerities above 330 m/s) and stratospheric arrivals, 20 explosions that were not detected and five explosions that have only tropospheric arrivals.

  16. Unraveling The Origin of Enhanced Field Emission from Irradiated FeCo-SiO2 Nanocomposites: A Combined Experimental and First-Principles Based Study.

    PubMed

    Sarker, Debalaya; Bhattacharya, Saswata; Rodriguez, Raul D; Sheremet, Evgeniya; Kabiraj, D; Avasthi, D K; Zahn, Dietrich R T; Schmidt, H; Srivastava, P; Ghosh, S

    2016-02-01

    This work is driven by the vision of engineering planar field emitters with ferromagnetic metal-insulator nanocomposite thin films, using swift heavy ion (SHI) irradiation method. FeCo nanoparticles inside SiO2 matrix, when subjected to SHI get elongated. Using this, we demonstrate here a planar field emitter with maximum current density of 550 μA/cm(2) at an applied field of 15 V/μm. The film, irradiated with 5 × 10(13) ions/cm(2) fluence (5e13) of 120 MeV Au(9+) ions, shows very high electron emitting quantum efficiency in comparison to its unirradiated counterpart. Surface enhanced Raman spectroscopy analysis of unirradiated and 5e13 films further confirms that the field emission (FE) enhancement is not only due to surface protrusions but also depends on the properties of entire matrix. We find experimental evidence of enhanced valence band density of states (VB DOS) for 5e13 film from XPS, which is verified in the electronic structure of a model FeCo cluster from first-principles based calculations combining density functional theory (DFT) and molecular dynamics (MD) simulations. The MD temperature is selected from the lattice temperature profile inside nanoparticles as deduced from thermal spike model. Increasing the irradiation fluence beyond 5e13, results in reduced VB DOS and melting of surface protrusions, thus causing reduction of FE current density. We finally conclude from theoretical analysis that change in fluence alters the co-ordination chemistry followed by the charge distribution and spin alignment, which influence the VB DOS and concurrent FE as evident from our experiment. PMID:26812580

  17. Experimental Studies in Ice Nucleation

    NASA Astrophysics Data System (ADS)

    Wright, Timothy Peter

    Ice nuclei play a critical role in the formation of precipitation in mixed phase clouds. Modification of IN concentrations can lead to changes in cloud lifetimes and precipitation size. Presented in this study are experimental investigations into ice nuclei in an ongoing effort to reduce the uncertainties that ice nuclei have on cloud processes and climate. This research presents a new version of the cold stage drop freezing assay to investigate the time-dependence of heterogeneous nucleation. The temperature range for the instrument spans from the melting point of water to the homogeneous freezing limit of ˜-38 deg C. Temperature stability for the instrument allowed for experimental operation for up to four days while interrogating the same sample. Up to a one hundred fold increase in the number of analyzed drops was accomplished through an in-house written automated drop freezing detection software package. Combined instrument design improvements allow for the analysis of IN concentrations down to ˜10-8 ice nuclei per picoliter of sample water. A new variant of the multiple-component stochastic model for heterogeneous ice nucleation was used to investigate the time dependence of heterogeneous freezing processes. This was accomplished by analyzing how the changes in the cooling rate can impact the observed nucleation rate. The model employed four material-dependent parameters to accurately capture the observed freezing of water drops containing Arizona Test Dust. The parameters were then used to accurately predict the freezing behavior of the drops in time dependent experiments. The time dependence freezing of a wide range of materials was then investigated. These materials included the minerals montmorillonite and kaolinite, the biological proxy ice nuclei contained within the product Icemax, and flame soot generated from the incomplete combustion of ethylene gas. The time dependence for ice nuclei collected from rainwater samples was also investigated. The

  18. About soil cover heterogeneity of agricultural research stations' experimental fields

    NASA Astrophysics Data System (ADS)

    Rannik, Kaire; Kõlli, Raimo; Kukk, Liia

    2013-04-01

    Depending on local pedo-ecological conditions (topography, (geo) diversity of soil parent material, meteorological conditions) the patterns of soil cover and plant cover determined by soils are very diverse. Formed in the course of soil-plant mutual relationship, the natural ecosystems are always influenced to certain extent by the other local soil forming conditions or they are site specific. The agricultural land use or the formation of agro-ecosystems depends foremost on the suitability of soils for the cultivation of feed and food crops. As a rule, the most fertile or the best soils of the area, which do not present any or present as little as possible constraints for agricultural land use, are selected for this purpose. Compared with conventional field soils, the requirements for the experimental fields' soil cover quality are much higher. Experimental area soils and soil cover composition should correspond to local pedo-ecological conditions and, in addition to that, represent the soil types dominating in the region, whereas the fields should be as homogeneous as possible. The soil cover heterogeneity of seven arable land blocks of three research stations (Jõgeva, Kuusiku and Olustvere) was studied 1) by examining the large scale (1:10 000) digital soil map (available via the internet), and 2) by field researches using the transect method. The stages of soils litho-genetic and moisture heterogeneities were estimated by using the Estonian normal soils matrix, however, the heterogeneity of top- and subsoil texture by using the soil texture matrix. The quality and variability of experimental fields' soils humus status, was studied more thoroughly from the aspect of humus concentration (g kg-1), humus cover thickness (cm) and humus stocks (Mg ha-1). The soil cover of Jõgeva experimental area, which presents an accumulative drumlin landscape (formed during the last glacial period), consist from loamy Luvisols and associated to this Cambisols. In Kuusiku area

  19. Acquisition of chemical remanent magnetization during experimental ferrihydrite-hematite conversion in Earth-like magnetic field-implications for paleomagnetic studies of red beds

    NASA Astrophysics Data System (ADS)

    Jiang, Zhaoxia; Liu, Qingsong; Dekkers, Mark J.; Tauxe, Lisa; Qin, Huafeng; Barrón, Vidal; Torrent, José

    2015-10-01

    Hematite-bearing red beds are renowned for their chemical remanent magnetization (CRM). If the CRM was acquired substantially later than the sediment was formed, this severely compromises paleomagnetic records. To improve our interpretation of the natural remanent magnetization, the intricacies of the CRM acquisition process must be understood. Here, we contribute to this issue by synthesizing hematite under controlled 'Earth-like' field conditions (≲ 100 μ T). CRM was imparted in 90 oriented samples with varying inclinations. The final synthesis product appeared to be dominated by hematite with traces of ferrimagnetic iron oxides. When the magnetic field intensity is ≳ 40 μ T, the CRM records the field direction faithfully. However, for field intensities ≲ 40 μ T, the CRM direction may deviate considerably from that of the applied field during synthesis. The CRM intensity normalized by the isothermal remanent magnetization (CRM/IRM@2.5 T) increases linearly with the intensity of growth field, implying that CRM could potentially be useful for relative paleointensity studies if hematite particles of chemical origins have consistent properties. CRM in hematite has a distributed unblocking temperature spectrum from ˜200 to ˜650 °C, while hematite with a depositional remanent magnetization (DRM) has a more confined spectrum from ˜ 600to 680 °C because it is usually coarser-grained and more stoichiometric. Therefore, the thermal decay curves of CRM with their concave shape are notably different from their DRM counterparts which are convex. These differences together are suggested to be a potential discriminator of CRM from DRM carried by hematite in natural red beds, and of significance for the interpretation of paleomagnetic studies on red beds.

  20. Microbial field pilot study

    SciTech Connect

    Knapp, R.M.; McInerney, M.J.; Menzie, D.E.; Coates, J.D.; Chisholm, J.L.

    1993-05-01

    A multi-well microbially enhanced oil recovery field pilot has been performed in the Southeast Vassar Vertz Sand Unit in Payne County, Oklahoma. The primary emphasis of the experiment was preferential plugging of high permeability zones for the purpose of improving waterflood sweep efficiency. Studies were performed to determine reservoir chemistry, ecology, and indigenous bacteria populations. Growth experiments were used to select a nutrient system compatible with the reservoir that encouraged growth of a group of indigenous nitrate-using bacteria and inhibit growth of sulfate-reducing bacteria. A specific field pilot area behind an active line drive waterflood was selected. Surface facilities were designed and installed. Injection protocols of bulk nutrient materials were prepared to facilitate uniform distribution of nutrients within the pilot area. By the end of December, 1991, 82.5 tons (75.0 tonnes) of nutrients had been injected in the field. A tracer test identified significant heterogeneity in the SEVVSU and made it necessary to monitor additional production wells in the field. The tracer tests and changes in production behavior indicate the additional production wells monitored during the field trial were also affected. Eighty two and one half barrels (13.1 m[sup 3]) of tertiary oil have been recovered. Microbial activity has increased CO[sub 2] content as indicated by increased alkalinity. A temporary rise in sulfide concentration was experienced. These indicate an active microbial community was generated in the field by the nutrient injection. Pilot area interwell pressure interference test results showed that significant permeability reduction occurred. The interwell permeabilities in the pilot area between the injector and the three pilot production wells were made more uniform which indicates a successful preferential plugging enhanced oil recovery project.

  1. Field Experimental Research on Human Crowding.

    ERIC Educational Resources Information Center

    Aiello, John R.; And Others

    Overcrowded residence halls at Rutgers University form the basis for this research study on the effects of overcrowding. Subjects were the occupants of 31 rooms (7 triple male rooms, 7 triple female rooms, 7 double male rooms, and 10 double female rooms). Two sets of measures were used to determine whether crowding caused arousal and stress. The…

  2. Microbial Field Pilot Study

    SciTech Connect

    Knapp, R.M.; McInerney, M.J.; Menzie, D.E.; Chisholm, J.L.

    1990-11-01

    This report covers progress made during the first year of the Microbial Field Pilot Study project. Information on reservoir ecology and characterization, facility and treatment design, core experiments, bacterial mobility, and mathematical modeling are addressed. To facilitate an understanding of the ecology of the target reservoir analyses of the fluids which support bacteriological growth and the microbiology of the reservoir were performed. A preliminary design of facilities for the operation of the field pilot test was prepared. In addition, procedures for facilities installation and for injection treatments are described. The Southeast Vassar Vertz Sand Unit (SEVVSU), the site of the proposed field pilot study, is described physically, historically, and geologically. The fields current status is presented and the ongoing reservoir simulation is discussed. Core flood experiments conducted during the last year were used to help define possible mechanisms involved in microbial enhanced oil recovery. Two possible mechanisms, relative permeability effects and changes in the capillary number, are discussed and related to four Berea core experiments' results. The experiments were conducted at reservoir temperature using SEVVSU oil, brine, and bacteria. The movement and activity of bacteria in porous media were investigated by monitoring the growth of bacteria in sandpack cores under no flow conditions. The rate of bacteria advancement through the cores was determined. A mathematical model of the MEOR process has been developed. The model is a three phase, seven species, one dimensional model. Finite difference methods are used for solution. Advection terms in balance equations are represented with a third- order upwind differencing scheme to reduce numerical dispersion and oscillations. The model is applied to a batch fermentation example. 52 refs., 26 figs., 21 tabs.

  3. An experimental study of the structure and acoustic field of a jet in a cross stream. [Ames 7-ft by 10-ft wind tunnel tests

    NASA Technical Reports Server (NTRS)

    Camelier, I.; Karamcheti, K.

    1976-01-01

    The plane of symmetry of a high speed circular jet was surveyed to measure the mean and turbulent velocity fields by using constant temperature hot wire anemometry. The intensity of the noise radiated from the jet was determined in the tunnel test section by utilizing the cross-correlation at a particular time delay between the signals of two microphones suitably located along a given direction. Experimental results indicate that the turbulent intensity inside the crossflow jet increases by a factor of (1 + 1/2) as compared to the turbulent intensity of the same jet under free conditions, with r indicating the ratio of the jet velocity by the cross stream velocity. The peak observed in the turbulence spectra obtained inside the potential core of the jet has a frequency that increases by the same factor with respect to the corresponding frequency measured in the case of the free jet. The noise radiated by the jet becomes more intense as the crossflow velocity increases. The measured acoustic intensity of the crossflow jet is higher than the value which would be expected from the increase of the turbulent intensity only.

  4. Dynamics and kinetics of molecular high Rydberg states in the presence of an electrical field: An experimental and classical computational study

    NASA Astrophysics Data System (ADS)

    Rabani, Eran; Levine, R. D.; Mühlpfordt, Annette; Even, U.

    1995-01-01

    by either a gain or a loss of enough energy. Either process occurs in a diffusive like fashion of many smaller steps, except for a fraction of trajectories where prompt ionization occurs. The results for ensembles of trajectories are examined in terms of the decay kinetics. It is found that after a short induction period, which can be identified with the sampling time of the available phase space, the kinetics of the decay depend only on the initial energy of the electron and on the magnitude of the field, but not on the other details of the excitation process. The computed kinetics of the up and down channels are shown to represent competing decay modes. A possible intramolecular mechanism for long time stability based on the sojourn in intermediate Rydberg states is discussed. The available experimental evidence does not suffice to rule out nor to substantiate this mechanism, and additional tests are proposed. The theoretical expectations are discussed in relation to observed time resolved decay kinetics of high Rydberg states of BBC (bisbenzenechromium) and of DABCO (1,4-diazabicyclo[2.2.2]octane). The experimental setup allows for the imposition of a weak (0.1-1.5 V/cm) electrical field in the excitation region. The role of the amplitude of the time delayed field, used to detect the surviving Rydberg states by ionization, is also examined. The observed decay kinetics are as previously reported for cold aromatic molecules: Most of the decay is on the sub-μs time scale with a minor (˜10%) longer time component. The decay rate of the faster component increases with the magnitude of the field. Many features in such an experiment, including the absolute time scales, are similar to those found in the classical trajectory computations, suggesting that the Hamiltonian used correctly describes the physics of the faster decay kinetics of the high Rydberg states.

  5. Microbial field pilot study

    SciTech Connect

    Knapp, R.M.; McInerney, M.J.; Menzie, D.E.; Chisholm, J.L.

    1992-03-01

    The objective of this project is to perform a microbial enhanced oil recovery field pilot in the Southeast Vassar Vertz Sand Unit (SEVVSU) in Payne County, Oklahoma. Indigenous, anaerobic, nitrate reducing bacteria will be stimulated to selectively plug flow paths which have been referentially swept by a prior waterflood. This will force future flood water to invade bypassed regions of the reservoir and increase sweep efficiency. This report covers progress made during the second year, January 1, 1990 to December 31, 1990, of the Microbial Field Pilot Study project. Information on reservoir ecology, surface facilities design, operation of the unit, core experiments, modeling of microbial processes, and reservoir characterization and simulation are presented in the report. To better understand the ecology of the target reservoir, additional analyses of the fluids which support bacteriological growth and the microbiology of the reservoir were performed. The results of the produced and injected water analysis show increasing sulfide concentrations with respect to time. In March of 1990 Mesa Limited Partnership sold their interest in the SEVVSU to Sullivan and Company. In April, Sullivan and Company assumed operation of the field. The facilities for the field operation of the pilot were refined and implementation was begun. Core flood experiments conducted during the last year were used to help define possible mechanisms involved in microbial enhanced oil recovery. The experiments were performed at SEVVSU temperature using fluids and inoculum from the unit. The model described in last year's report was further validated using results from a core flood experiment. The model was able to simulate the results of one of the core flood experiments with good quality.

  6. Microbial field pilot study

    SciTech Connect

    Knapp, R.M.; McInerney, M.J.; Menzie, D.E.; Chisholm, J.L.

    1992-03-01

    The objective of this project is to perform a microbial enhanced oil recovery field pilot in the Southeast Vassar Vertz Sand Unit (SEVVSU) in Payne County, Oklahoma. Indigenous, anaerobic, nitrate reducing bacteria will be stimulated to selectively plug flow paths which have been referentially swept by a prior waterflood. This will force future flood water to invade bypassed regions of the reservoir and increase sweep efficiency. This report covers progress made during the second year, January 1, 1990 to December 31, 1990, of the Microbial Field Pilot Study project. Information on reservoir ecology, surface facilities design, operation of the unit, core experiments, modeling of microbial processes, and reservoir characterization and simulation are presented in the report. To better understand the ecology of the target reservoir, additional analyses of the fluids which support bacteriological growth and the microbiology of the reservoir were performed. The results of the produced and injected water analysis show increasing sulfide concentrations with respect to time. In March of 1990 Mesa Limited Partnership sold their interest in the SEVVSU to Sullivan and Company. In April, Sullivan and Company assumed operation of the field. The facilities for the field operation of the pilot were refined and implementation was begun. Core flood experiments conducted during the last year were used to help define possible mechanisms involved in microbial enhanced oil recovery. The experiments were performed at SEVVSU temperature using fluids and inoculum from the unit. The model described in last year`s report was further validated using results from a core flood experiment. The model was able to simulate the results of one of the core flood experiments with good quality.

  7. Experimental study of vortex diffusers

    SciTech Connect

    Shakerin, S.; Miller, P.L.

    1995-11-01

    This report documents experimental research performed on vortex diffusers used in ventilation and air-conditioning systems. The main objectives of the research were (1) to study the flow characteristics of isothermal jets issuing from vortex diffusers, (2) to compare the vortex diffuser`s performance with that of a conventional diffuser, and (3) to prepare a report that disseminates the results to the designers of ventilation and air-conditioning systems. The researchers considered three diffusers: a conventional round ceiling diffuser and two different styles of vortex diffusers. Overall, the vortex diffusers create slightly more induction of ambient air in comparison to the conventional diffuser.

  8. Experimental studies of glass refining

    NASA Technical Reports Server (NTRS)

    Subramanian, R. S.; Cole, R.; Kondos, P.

    1984-01-01

    The basic components of the experimental apparatus were selected and acquired. Techniques were developed for the fabrication of the special crucibles necessary for the experiments. Arrangements were made for the analysis of glass and gas bubble samples for composition information. Donations of major equipment were received for this project from Owens, Illinois where a similar study had been conducted a few year ago. Decisions were made regarding the actual glass composition to be used, the gas to be used in the first experiments, and the temperatures at which the experiments should be conducted. A microcomputer was acquired, and work was begun on interfacing the video analyzer to it.

  9. The linear model and experimentally observed resonant field amplification in tokamaks and reversed field pinches

    SciTech Connect

    Pustovitov, V. D.

    2011-01-15

    A review is given of the experimentally observed effects related to the resonant field amplification (RFA) and the Resistive Wall Mode (RWM) instability in tokamaks and reversed field pinches (RFPs). This includes the feedback rotation of RWM in RFX-mod RFP, dependence of the RWM growth rate on the plasma-wall separation observed in JT-60U, appearance of the slowly growing RWM precursors in JT-60U and similar phenomena in other devices. The experimental results are compared with theoretical predictions based on the model comprising the Maxwell equations, Ohm's law for the conducting wall, the boundary conditions and assumption of linear plasma response to the external magnetic perturbations. The model describes the plasma reaction to the error field as essentially depending on two factors: the plasma proximity to the RWM stability threshold and the natural rotation frequency of the plasma mode. The linear response means that these characteristics are determined by the plasma equilibrium parameters only. It is shown that the mentioned effects in different devices under different conditions can be described on a common basis with only assumption that the plasma behaves as a linear system. To extend the range of the model validation, some predictions are derived with proposals for experimental studies of the RFA dynamics.

  10. Experimental studies with palygorskite dusts.

    PubMed

    Wagner, J C; Griffiths, D M; Munday, D E

    1987-11-01

    As the preliminary results of experimental studies on dust from the palygorskite group have led to some confusion a detailed description of the completed investigation is given for clarification. As in other experiments the biological effects have been shown to be associated with the physical characteristics of the fibres in these specimens. Samples of sepiolite and attapulgite from Spain and a single sample of palygorskite from the United Kingdom have been studied. Serious abnormalities were produced only by the palygorskite and one of the attapulgite dusts. The palygorskite is of no commercial interest and the attapulgite was from one small deposit and was used only in the preparation of drilling mud in the exploration of oil deposits. PMID:2961365

  11. Grouping of Experimental Conditions as an Approach to Evaluate Effects of Extremely Low-Frequency Magnetic Fields on Oxidative Response in in vitro Studies

    PubMed Central

    Mattsson, Mats-Olof; Simkó, Myrtill

    2014-01-01

    A large body of literature deals with biological effects of extremely low-frequency magnetic fields (ELF MFs) studied in vitro. Despite the multitude of studies, no coherent picture has evolved regarding the plausibility of effects at low-flux densities or regarding the interaction mechanisms. Here, we propose that ELF MF exposure in vitro causes changes in oxidative status as an early response. We tested this hypothesis by scrutinizing the literature and applying a grouping approach for analyzing relevant biological properties and exposure conditions. A total of 41 scientific original publications were analyzed for this purpose. The conclusion from the work is that ELF MF (modulated or unmodulated) consistently can influence the oxidative status, at or above 1 mT, in a broad range of cell types and independent of exposure duration. A response at lower flux densities is seen in certain studies, although not consistently. Further studies with stringent protocols for sham exposure, blinding, and statistical analysis as well as appropriate positive controls are needed to establish if true dose-relationships for effects on oxidative status exist. PMID:25229055

  12. Simulation and Experimental Studies on Substrate Temperature and Gas Density Field in Hfcvd Diamond Films Growth on WC-Co Drill Tools

    NASA Astrophysics Data System (ADS)

    Zhang, Jianguo; Zhang, Tao; Wang, Xinchang; Shen, Bin; Sun, Fanghong

    2013-04-01

    Uniform temperature and gas density field inside the reactor play an important role on synthesis of high-quality diamond films using hot filament chemical vapor deposition (HFCVD) method. In the present study, the finite volume method (FVM) is adopted to simulate the temperature and gas density distribution during the deposition process. Temperature-measuring experiments are conducted to verify the correctness of the simulation results. Thereafter, the deposition parameters are optimized using this model as D (filament separation) = 35 mm, H (filament-substrate distance) = -10 mm and N (number of gas inlet) = 3. Finally, experiments of depositing diamond films on WC-Co drill tools are carried out with the optimal deposition parameters. The results of the characterization by SEM and Raman spectrum exhibit that as-fabricated diamond-coated tools present a layer of high-quality diamond films with homogeneous surface and uniform thickness, further validating the accuracy of the parameter optimization using the simulation method.

  13. An experimental study of the flow of gas along synthetic faults of varying orientation to the stress field: Implications for performance assessment of radioactive waste disposal

    NASA Astrophysics Data System (ADS)

    Cuss, Robert J.; Harrington, Jon F.; Noy, David J.; Sathar, Shanvas; Norris, Simon

    2015-05-01

    Critical stress theory states that fault transmissivity is strongly dependent upon orientation with respect to the stress tensor. This paper describes an experimental study aimed at verifying critical stress theory using a bespoke angled shear rig designed to examine the relationship between gas flows along a kaolinite-filled synthetic fault as a function of fault dip. A total of 22 gas injection experiments were conducted on faults oriented 0°, 15°, 30°, and 45° to horizontal; both with and without active shear. Gas flow was seen to be complex; repeat gas injection testing showed a consistent gas entry pressure but considerably different, nonrepeatable, gas peak or breakthrough pressure. Gas flow occurred along discrete, dilatant pathways. The physics governing the pressure at which these features formed was repeatable; however, permeability was dependent on the number, distribution, and geometry of the resultant pathways. The nonrepeatable gas response suggests that the number of pathways was dependent on very subtle variations in gouge properties. No fault orientations were seen to exhibit nonflow characteristics, although critical stress theory predicted that two of the investigated fault angles should be effective seals. However, a small variation in gas entry pressure was seen with fault angle as a result of varying normal and shear stress acting on the gouge material. Shear was seen to enhance gas movement by reducing gas entry pressure and increased permeability once gas became mobile. Therefore, in kaolinite gouge-filled faults, shear is not an effective self-sealing mechanism to gas flow.

  14. Experimental Validation of Simulations Using Full-field Measurement Techniques

    SciTech Connect

    Hack, Erwin

    2010-05-28

    The calibration by reference materials of dynamic full-field measurement systems is discussed together with their use to validate numerical simulations of structural mechanics. The discussion addresses three challenges that are faced in these processes, i.e. how to calibrate a measuring instrument that (i) provides full-field data, and (ii) is dynamic; (iii) how to compare data from simulation and experimentation.

  15. Electromagnetic Field Penetration Studies

    NASA Technical Reports Server (NTRS)

    Deshpande, M.D.

    2000-01-01

    A numerical method is presented to determine electromagnetic shielding effectiveness of rectangular enclosure with apertures on its wall used for input and output connections, control panels, visual-access windows, ventilation panels, etc. Expressing EM fields in terms of cavity Green's function inside the enclosure and the free space Green's function outside the enclosure, integral equations with aperture tangential electric fields as unknown variables are obtained by enforcing the continuity of tangential electric and magnetic fields across the apertures. Using the Method of Moments, the integral equations are solved for unknown aperture fields. From these aperture fields, the EM field inside a rectangular enclosure due to external electromagnetic sources are determined. Numerical results on electric field shielding of a rectangular cavity with a thin rectangular slot obtained using the present method are compared with the results obtained using simple transmission line technique for code validation. The present technique is applied to determine field penetration inside a Boeing-757 by approximating its passenger cabin as a rectangular cavity filled with a homogeneous medium and its passenger windows by rectangular apertures. Preliminary results for, two windows, one on each side of fuselage were considered. Numerical results for Boeing-757 at frequencies 26 MHz, 171-175 MHz, and 428-432 MHz are presented.

  16. Prospective risk analysis prior to retrospective incident reporting and analysis as a means to enhance incident reporting behaviour: a quasi-experimental field study.

    PubMed

    Kessels-Habraken, Marieke; De Jonge, Jan; Van der Schaaf, Tjerk; Rutte, Christel

    2010-05-01

    Hospitals can apply prospective and retrospective methods to reduce the large number of medical errors. Retrospective methods are used to identify errors after they occur and to facilitate learning. Prospective methods aim to determine, assess and minimise risks before incidents happen. This paper questions whether the order of implementation of those two methods influences the resultant impact on incident reporting behaviour. From November 2007 until June 2008, twelve wards of two Dutch general hospitals participated in a quasi-experimental reversed-treatment non-equivalent control group design. The six units of Hospital 1 first conducted a prospective analysis, after which a sophisticated incident reporting and analysis system was implemented. On the six units of Hospital 2 the two methods were implemented in reverse order. Data from the incident reporting and analysis system and from a questionnaire were used to assess between-hospital differences regarding the number of reported incidents, the spectrum of reported incident types, and the profession of reporters. The results show that carrying out a prospective analysis first can improve incident reporting behaviour in terms of a wider spectrum of reported incident types and a larger proportion of incidents reported by doctors. However, the proposed order does not necessarily yield a larger number of reported incidents. This study fills an important gap in safety management research regarding the order of the implementation of prospective and retrospective methods, and contributes to literature on incident reporting. This research also builds on the network theory of social contagion. The results might indicate that health care employees can disseminate their risk perceptions through communication with their direct colleagues. PMID:20202731

  17. Genesis of Dune Fields Under Unidirectional Wind with Sand Input Flux Control: An Experimental Approach

    NASA Astrophysics Data System (ADS)

    Garcia, A.; Courrech du Pont, S.; Rodriguez, S.; Valance, A.; Narteau, C.; Gao, X.; Lucas, A.

    2015-05-01

    Our experimental studies with control of wind and sediment source will characterize more precisely the different modes of dune formation and long-term evolution, and constrain the physics behind the morphogenesis and dynamics of dunes fields.

  18. Numerical and Experimental Study of Levee Breach

    NASA Astrophysics Data System (ADS)

    Elalfy, E. Y.; LaRocque, L.; Riahi-Nezhad, C. K.; Chaudhry, H.

    2014-12-01

    Levees are constructed along rivers and channels for flood protection. Failure of these levees can cause loss of life and property damage. A better understanding of the flow field from a levee breach allows the decision maker to assess risks and to prepare emergency plans. For this purpose, a two-dimensional numerical model is developed to simulate the levee breach. The model solves the shallow-water equations using the MacCormack explicit, finite- difference two-step, predictor-corrector scheme. The scheme is second-order accurate in time and space. The artificial viscosity technique is used to smooth the high-frequency oscillations in the computed results. The numerical results compare satisfactorily with the experimental results. A parametric study is carried-out to investigate the effect of main channel width, breach width on the computed flow field.

  19. Experimental investigation of the critical magnetic fields of transition metal superconductors

    NASA Technical Reports Server (NTRS)

    Mcevoy, J. P.

    1973-01-01

    The isothermal magnetic transitions of a type 2 superconductor have been studied by AC susceptibility techniques as a function of the amplitude and frequency of the exciting field. The field variation of the complex susceptibility was used to determine the critical fields. The research was planned to clarify the determination (both experimentally and theoretically) of the maximum field at which the superconductive phase spontaneously nucleates in the bulk and on the surface of the metal.

  20. Horse Manure and Other Fun Projects. Field Studies and Laboratory Experiences in Environmental Biology - A Book of Experimental Ideas for Secondary School Biology Teachers.

    ERIC Educational Resources Information Center

    Brown, Robert T., Ed.; Clark, Barbara G., Ed.

    This guide contains a collection of laboratory and field inquiries designed to promote ecological awareness, sensitivity, and understanding. The activities compiled by 28 teachers are for use in teaching biology at the secondary level. They are presented in a "recipe" form to make it possible for teachers without prior experience or training to…

  1. Experimental Study of RF Pulsed Heating

    SciTech Connect

    Laurent, Lisa; Tantawi, Sami; Dolgashev, Valery; Nantista, Christopher; Higashi, Yasuo; Aicheler, Markus; Heikkinen, Samuli; Wuensch, Walter; /CERN

    2011-11-04

    Cyclic thermal stresses produced by rf pulsed heating can be the limiting factor on the attainable reliable gradients for room temperature linear accelerators. This is especially true for structures that have complicated features for wakefield damping. These limits could be pushed higher by using special types of copper, copper alloys, or other conducting metals in constructing partial or complete accelerator structures. Here we present an experimental study aimed at determining the potential of these materials for tolerating cyclic thermal fatigue due to rf magnetic fields. A special cavity that has no electric field on the surface was employed in these studies. The cavity shape concentrates the magnetic field on one flat surface where the test material is placed. The materials tested in this study have included oxygen free electronic grade copper, copper zirconium, copper chromium, hot isostatically pressed copper, single crystal copper, electroplated copper, Glidcop(reg. sign), copper silver, and silver plated copper. The samples were exposed to different machining and heat treatment processes prior to rf processing. Each sample was tested to a peak pulsed heating temperature of approximately 110 C and remained at this temperature for approximately 10 x 10{sup 6} rf pulses. In general, the results showed the possibility of pushing the gradient limits due to pulsed heating fatigue by the use of copper zirconium and copper chromium alloys.

  2. Experimental studies of transonic flow field near a longitudinally slotted wind tunnel wall. Ph.D. Thesis - George Washington Univ., 1988

    NASA Technical Reports Server (NTRS)

    Everhart, Joel L.; Bobbitt, Percy J.

    1994-01-01

    The results of detailed parametric experiments are presented for the near-wall flow field of a longitudinally slotted transonic wind tunnel. Existing data are reevaluated and new data obtained in the Langley 6- by 19-inch Transonic Wind Tunnel are presented and analyzed. In the experiments, researchers systematically investigate many pertinent wall-geometry variables such as the wall openness and the number of slots along with the free stream Mach number and model angle of attack. Flow field surveys on the plane passing through the centerline of the slot were conducted and are presented. The effects of viscosity on the slot flow are considered in the analysis. The present experiments, combined with those of previous investigations, give a more complete physical characterization of the flow near and through the slotted wall of a transonic wind tunnel.

  3. The three youngest Plinian eruptions of Mt Pelée, Martinique (P1, P2 and P3): Constraining the eruptive conditions from field and experimental studies.

    NASA Astrophysics Data System (ADS)

    Kueppers, Ulrich; Uhlig, Joan; Carazzo, Guillaume; Kaminski, Edouard; Perugini, Diego; Tait, Steve; Clouard, Valérie

    2015-04-01

    Mt Pelée on Martinique, French Lesser Indies, is infamous for the last big Pelean (i.e., dome forming) eruption in 1902 AD that destroyed agricultural land and the city of Saint Pierre by pyroclastic density currents. Beside such mostly valley-confined deposits, the geological record shows thick fall deposits of at least three Plinian eruptions during the past 2000 years. In an attempt to describe and understand systematic eruptive behaviours as well as the associated variability of eruptive scenarios of Plinian eruptions in Martinique, we have investigated approx. 50 outcrops belonging to the P1 (1315 AD), P2 (345 AD) and P3 (4 AD) eruptions (Traineau et al., JVGR 1989) and collected bulk samples as well as >100 mm pumiceous clasts. All samples are andesitic, contain plagioclase and pyroxene in a glassy matrix and range in porosity between 55 and 69 vol.% with individual bubbles rarely larger than 1 mm. Our approach was two-fold: 1) Loose bulk samples have been subject to dry mechanical sieving in order to quantively describe the grain-size distribution and the fractal dimension. 2) From large clasts, 60*25 mm cylinders have been drilled for fragmentation experiments following the sudden decompression of gas in the sample's pore space. The used experimental set-up allowed for precisely controllable and repeatable conditions (5, 10 and 15 MPa, 25 °C) and the complete sampling of the generated pyroclasts. These experimentally generated clasts were analysed for their grain-size distribution and fractal dimension. For both natural samples and experimental populations, we find we find that the grain-size distribution follows a power-law, with an exponent between 2,5 and 3,7. Deciphering eruption conditions from deposits alone is challenging because of the complex interplay of dynamic volcanic processes and transport-related sorting. We use the quantified values of fractal dimension for a comparison of the power law exponents among the three eruptions and the

  4. Precision improvement in dark-field microscopy imaging by using gold nanoparticles as an internal reference: a combined theoretical and experimental study.

    PubMed

    Ma, Jun; Liu, Yue; Gao, Peng Fei; Zou, Hong Yan; Huang, Cheng Zhi

    2016-04-28

    Low accuracy is a big obstacle in the dark-field microscopy imaging (iDFM) technique in practical applications. In order to reduce the deviations and fluctuations in the observed or snapped scattered light in the iDFM technique caused by unavoidable measurement errors, bare gold nanoparticles (AuNPs) were introduced as an internal reference (IR). The feasibility of using AuNPs as the IR in iDFM in theory was verified. The function of the IR in improving the precision of the acquired data through post data analysis was identified by three kinds of experiments: monitoring the oxidation process of silver nanoparticles (AgNPs) at room temperature, quantifying the level of glucose with AgNPs used as probes and quantifying the change in the light intensity of AuNPs after the plasmon resonance energy transfer (PRET) between AuNPs and tetramethylrhodamine (TAMRA). PMID:27065307

  5. Precision improvement in dark-field microscopy imaging by using gold nanoparticles as an internal reference: a combined theoretical and experimental study

    NASA Astrophysics Data System (ADS)

    Ma, Jun; Liu, Yue; Gao, Peng Fei; Zou, Hong Yan; Huang, Cheng Zhi

    2016-04-01

    Low accuracy is a big obstacle in the dark-field microscopy imaging (iDFM) technique in practical applications. In order to reduce the deviations and fluctuations in the observed or snapped scattered light in the iDFM technique caused by unavoidable measurement errors, bare gold nanoparticles (AuNPs) were introduced as an internal reference (IR). The feasibility of using AuNPs as the IR in iDFM in theory was verified. The function of the IR in improving the precision of the acquired data through post data analysis was identified by three kinds of experiments: monitoring the oxidation process of silver nanoparticles (AgNPs) at room temperature, quantifying the level of glucose with AgNPs used as probes and quantifying the change in the light intensity of AuNPs after the plasmon resonance energy transfer (PRET) between AuNPs and tetramethylrhodamine (TAMRA).Low accuracy is a big obstacle in the dark-field microscopy imaging (iDFM) technique in practical applications. In order to reduce the deviations and fluctuations in the observed or snapped scattered light in the iDFM technique caused by unavoidable measurement errors, bare gold nanoparticles (AuNPs) were introduced as an internal reference (IR). The feasibility of using AuNPs as the IR in iDFM in theory was verified. The function of the IR in improving the precision of the acquired data through post data analysis was identified by three kinds of experiments: monitoring the oxidation process of silver nanoparticles (AgNPs) at room temperature, quantifying the level of glucose with AgNPs used as probes and quantifying the change in the light intensity of AuNPs after the plasmon resonance energy transfer (PRET) between AuNPs and tetramethylrhodamine (TAMRA). Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08837b

  6. An experimental and modeling study of grain-scale uranium desorption from field-contaminated sediments and the potential influence of microporosity on mass-transfer

    NASA Astrophysics Data System (ADS)

    Stoliker, D.; Liu, C.; Kent, D. B.; Zachara, J. M.

    2012-12-01

    The aquifer below the 300-Area of the Hanford site (Richland, WA, USA) is plagued by a persistent plume of dissolved uranium (U(VI)) in excess of the Environmental Protection Agency drinking water maximum contamination level even after the removal of highly contaminated sediments. The aquifer sediments in the seasonally saturated lower vadose zone act as both a source and sink for uranium during stage changes in the nearby Columbia River. Diffusion limitation of uranium mass-transfer within these sediments has been cited as a potential cause of the plume's persistence. Equilibrium U(VI) sorption is a strong function of variable chemical conditions, especially carbonate, hydrogen, and uranyl ion activities. Field-contaminated sediments from the site require up to 1,000 hours to reach equilibrium in static batch reactors. Increases in U(VI) concentrations over longer time-scales result from changes in chemical conditions, which drive reactions with sediments that favor U(VI) desorption. Grain-scale U(VI) sorption/desorption rates are slow, likely owing to diffusion of U(VI) and other solutes through intra-granular pore domains. In order to improve understanding of the impact of intra-granular diffusion and chemical reactions controlling grain-scale U(VI) release, experiments were conducted on individual particle size fractions of a <8 mm composite of field-contaminated, lower vadose zone sediments. For each size fraction, equilibrium U(VI) sorption/desorption in static batch reactors was well-described by surface complexation models over a range of chemical conditions applicable to the field site. Desorption rates from individual size fractions in flow-through batch reactors, examined under a single set of constant chemical conditions with multiple stop-flow events, were similar for all size fractions <2 mm. Kinetic U(VI) desorption in flow-through batch reactors was modeled using a multi-rate surface complexation approach, where sorption/desorption rates were

  7. Michelson wide-field stellar interferometry: principles and experimental verification.

    PubMed

    Montilla, I; Pereira, S F; Braat, J J M

    2005-01-20

    A new interferometric technique for Michelson wide-field interferometry is presented that consists of a Michelson pupil-plane combination scheme in which a wide field of view can be achieved in one shot. This technique uses a stair-shaped mirror in the intermediate image plane of each telescope in the array, allowing for simultaneous correction of the differential delay for the on-axis and off-axis image positions. Experimental results in a laboratory setup show that it is possible to recover the fringes of on-axis and off-axis stars with an angular separation of 1 arc min simultaneously and with a similar contrast. This new technique represents a considerable extension of the field of view of an interferometer without the need for extra observation time. PMID:15717821

  8. Experimental studies of the mechanisms of seismo-geochemical precursors

    SciTech Connect

    Fong-liang, J.; Gui-ru, L.

    1981-05-01

    The following aspects of modeling experiments on seismo-geochemical precursors are described: (1) gas emission during laboratory stress loading and rupture of rocks, (2) field measurements with explosion sources, (3) aquifer mixing tests in the field, (4) experimental studies of physico-chemical processes caused by stress events.

  9. A Field Experimental Approach to the Study of Relevance Assessments in Relation to Document Searching. Final Report to the National Science Foundation. Volume II, Appendices.

    ERIC Educational Resources Information Center

    Rees, Alan M.; Schultz, Douglas G.

    This volume consists of appendices to the final report on a study of the nature and variability of relevance judgments connected with document searching. Included in these appendices are: (1) all test materials and forms used in the experiments with medical librarians, medical experts, medical scientists, and medical students who were asked to…

  10. Experimental rotor-stator cavity ingress study

    SciTech Connect

    Fox, M.; Glezer, B.

    1999-07-01

    An experimental facility has been constructed in order to study the problems of hot gas ingress and heat transfer in an engine-realistic rotor-stator cavity. This paper describes the facility, and presents detailed baseline measurements of gas ingress on the stator using a carbon-dioxide tracer method. Tests were conducted with and without a rim seal, with two axial rotor-stator spacings, and for two methods of injecting the disk cavity buffer air: axially through a central hole in the stator and through rim impingement. A cross section of the facility is shown. The data show the importance, for ingress prevention, of the detailed geometry in the region of the disk rim, as well as provides qualitative data which can be used as a guideline by the engine designer. The current data are compared, finally, to those of other researchers in the field.

  11. Experimental Characterization of Piezoelectric Radial Field Diaphragms for Fluidic Control

    NASA Technical Reports Server (NTRS)

    Bryant, R. G.; Kavli, S. E.; Thomas, R. A., Jr.; Darji, K. J.; Mossi, K. M.

    2004-01-01

    NASA has recently developed a new piezoelectric actuator, the Radial Field Diaphragm or RFD. This actuator uses a radially-directed electric field to generate concentric out-of-plane (Z-axis) motion that allows this packaged device to be used as a pump or valve diaphragm. In order to efficiently use this new active device, experimental determination of pressure, flow rate, mechanical work, power consumption and overall efficiency needs to be determined by actually building a pump. However, without an optimized pump design, it is difficult to assess the quality of the data, as these results are inherent to the actual pump. Hence, separate experiments must be conducted in order to generate independent results to help guide the design criteria and pump quality. This paper focuses on the experiments used to generate the RFD's operational parameters and then compares these results to the experimentally determined results of several types of ball pumps. Also discussed are how errors are inherently introduced into the experiments, the pump design, experimental hardware and their effects on the overall system efficiency.

  12. Theoretical and experimental studies on the foundation theoretical and experimental studies on the foundation of mesomechanics

    NASA Astrophysics Data System (ADS)

    Chudnovsky, A.; Wu, S.

    1992-06-01

    The report summarizes a closely coupled experimental and theoretical investigation of various stages of Fracture Process: (1) accumulation of 'damage' on submicroscopical and microscopical scales leading to crack initiation; (2) slow (subcritical) crack growth and an evolution of the damage zone; (3) transition to dynamic crack growth and the catastrophic failure. The experimental part of the program is focused on the observation and quantitative characterization of damage preceding and accompanying crack initiation and growth. A special experimental setup for studying the fracture process under variable stress field is reported in Chapter 2. A leading role of crack-damage interaction in fracture process is well documented. A new formalism for solution of crack-microcrack array interaction problem and its successful implementation in the evaluation of crack layer driving forces is presented in Chapter 3. A new model of the process zone, which generalizes the well-known Dagdale-Barenblatt model is presented in Chapter 4. A new measure for material toughness and the prediction of R-curve behavior illustrate the practical application of our model. Experimental examinations of our model under various test conditions are reported in Chapters 4, 5 and 6. The development of the constitutive equations for Crack Layer evolution and their experimental examinations under stress relaxation, fatigue and creep conditions are reported in Chapters 5 and 6. An accelerated test procedure and the formulation of crack layer instability criteria as a substitution for the conventional fracture toughness parameters are also discussed in Chapter 6.

  13. Experimental violation of Tsirelson's bound by Maxwell fields

    NASA Astrophysics Data System (ADS)

    Sandeau, N.; Akhouayri, H.; Matzkin, A.; Durt, T.

    2016-05-01

    In analogy with quantum optics it is possible to impose nonseparability between different degrees of freedom of an optical beam. The resulting correlations between these degrees of freedom can be investigated with correlations functions traditionally employed in quantum mechanics, such as the well-known Clauser-Horne-Shimony-Holt (CHSH) correlation function. In this paper we present results achieving a maximal violation of Tsirelson's bound on CHSH correlations between spatial and polarization degrees of freedom of classical (Maxwell) fields. We describe the theoretical method, based on the realization of a nonunitary gate, and then proceed to its experimental implementation carried out with classical optical techniques. Our approach relies on the realization at the level of classical Maxwell fields of a so-called POVM (positive operator valued measure) which is traditionally discussed in the realm of quantum physics.

  14. The impact of funding through the RF President's grants for young scientists (the field--medicine) on research productivity: a quasi-experimental study and a brief systematic review.

    PubMed

    Saygitov, Ruslan T

    2014-01-01

    The impact of grants on research productivity has been investigated by a number of retrospective studies. The results of these studies vary considerably. The objective of my study was to investigate the impact of funding through the RF President's grants for young scientists on the research productivity of awarded applicants. The study compared the number of total articles and citations for awarded and rejected applicants who in 2007 took part in competitions for young candidates of science (CoS's) and doctors of science (DoS's) in the scientific field of medicine. The bibliometric analysis was conducted for the period from 2003 to 2012 (five years before and after the competition). The source of bibliometric data is the eLIBRARY.RU database. The impact of grants on the research productivity of Russian young scientists was assessed using the meta-analytical approach based on data from quasi-experimental studies conducted in other countries. The competition featured 149 CoS's and 41 DoS's, out of which 24 (16%) and 22 (54%) applicants, respectively, obtained funding. No difference in the number of total articles and citations at baseline, as well as in 2008-2012, for awarded and rejected applicants was found. The combination of data from the Russian study and other quasi-experimental studies (6 studies, 10 competitions) revealed a small treatment effect--an increase in the total number of publications over a 4-5-year period after the competition by 1.23 (95% CI 0.48-1.97). However, the relationship between the number of total publications published by applicants before and after the competition revealed that this treatment effect is an effect of the "maturation" of scientists with a high baseline publication activity--not of grant funding. PMID:24475203

  15. Adaptive wave field synthesis for active sound field reproduction: experimental results.

    PubMed

    Gauthier, Philippe-Aubert; Berry, Alain

    2008-04-01

    Sound field reproduction has applications in music reproduction, spatial audio, sound environment reproduction, and experimental acoustics. Sound field reproduction can be used to artificially reproduce the spatial character of natural hearing. The objective is then to reproduce a sound field in a real reproduction environment. Wave field synthesis (WFS) is a known open-loop technology which assumes that the reproduction environment is anechoic. The room response thus reduces the quality of the physical sound field reproduction by WFS. In recent research papers, adaptive wave field synthesis (AWFS) was defined as a potential solution to compensate for these quality reductions from which WFS objective performance suffers. In this paper, AWFS is experimentally investigated as an active sound field reproduction system with a limited number of reproduction error sensors to compensate for the response of the listening environment. Two digital signal processing algorithms for AWFS are used for comparison purposes, one of which is based on independent radiation mode control. AWFS performed propagating sound field reproduction better than WFS in three tested reproduction spaces (hemianechoic chamber, standard laboratory space, and reverberation chamber). PMID:18397007

  16. Experimental evaluation of radiosity for room sound-field prediction.

    PubMed

    Hodgson, Murray; Nosal, Eva-Marie

    2006-08-01

    An acoustical radiosity model was evaluated for how it performs in predicting real room sound fields. This was done by comparing radiosity predictions with experimental results for three existing rooms--a squash court, a classroom, and an office. Radiosity predictions were also compared with those by ray tracing--a "reference" prediction model--for both specular and diffuse surface reflection. Comparisons were made for detailed and discretized echograms, sound-decay curves, sound-propagation curves, and the variations with frequency of four room-acoustical parameters--EDT, RT, D50, and C80. In general, radiosity and diffuse ray tracing gave very similar predictions. Predictions by specular ray tracing were often very different. Radiosity agreed well with experiment in some cases, less well in others. Definitive conclusions regarding the accuracy with which the rooms were modeled, or the accuracy of the radiosity approach, were difficult to draw. The results suggest that radiosity predicts room sound fields with some accuracy, at least as well as diffuse ray tracing and, in general, better than specular ray tracing. The predictions of detailed echograms are less accurate, those of derived room-acoustical parameters more accurate. The results underline the need to develop experimental methods for accurately characterizing the absorptive and reflective characteristics of room surfaces, possible including phase. PMID:16938969

  17. WATER TEMPERATURE DYNAMICS IN EXPERIMENTAL FIELD CHANNELS: ANALYSIS AND MODELING

    EPA Science Inventory

    This study is on water temperature dynamics in the shallow field channels of the USEPA Monticello Ecological Research Station (MERS). The hydraulic and temperature environment in the MERS channels was measured and simulated to provide some background for several biological studie...

  18. Experimental study and evaluation of radioprotective drugs

    NASA Technical Reports Server (NTRS)

    Smith, D. E.; Thomson, J. F.

    1968-01-01

    Experimental study evaluates radioprotective drugs administered before exposure either orally or intravenously. Specifically studied are the sources of radiation, choice of radiation dose, choice of animals, administration of drugs, the toxicity of protective agents and types of protective drug.

  19. Experimental Study of Olivine-rich Troctolites

    NASA Astrophysics Data System (ADS)

    Mu, S.; Faul, U.

    2014-12-01

    This experimental study is designed to complement field observations of olivine-rich troctolites in ophiolites and from mid-ocean ridges. The olivine-rich troctolites are characterized by high volume proportion of olivine with interstitial plagioclase and clinopyroxene. Typically the clinopyroxene occurs in the form of few large, poikilitic grains. The primary purpose of this study is to investigate the effects of cooling process on the geometry of the interstitial phases (clinopyroxene and plagioclase). Experiments are conducted in a piston cylinder apparatus by first annealing olivine plus a basaltic melt with a composition designed to be in equilibrium with four phases at ~ 1 GPa and 1250ºC. Initially, we anneal the olivine-basalt aggregates at 1350 °C and 0.7 GPa for one week to produce a steady state microstructure. At this temperature only olivine and minor opx are present as crystalline phases. We then cool the samples over two weeks below their solidus temperature, following different protocols. The post-run samples are sectioned, polished, and imaged at high resolution and analyzed by using a field emission SEM. Initial observations show that under certain conditions clinopyroxene nucleates distributed throughout the aggregate at many sites, forming relatively small, rounded to near euhedral grains. Under certain conditions few cpx grains nucleate and grow with a poikilitic shape, partially or fully enclosing olivine grains, as is observed in natural samples. As for partially molten aggregates quenched form the annealing temperature, the microstructure will be characterized by tracing phase boundaries on screen by using ImageJ software. The geometry of the interstitial phases will be quantified by determining the grain boundary wetness, in this case the ratio of the length of polyphase to single phase (olivine-olivine) boundaries. Compositional data will also be used to study the change in major element compositions before and after the cooling process.

  20. Experimental and theoretical studies in nonlinear aeroelasticity

    NASA Astrophysics Data System (ADS)

    Attar, Peter Joseph

    Experimental and theoretical studies are conducted in the field of nonlinear aeroelasticity. Specifically two aeroelastic configurations, a flapping flag and a delta wing, are investigated and correlations between theory and experiment are presented. Two nonlinear structural theories are used to describe the structural behavior of the two models which are studied. The delta wing structural behavior is modeled using the nonlinear plate theory of von Karman. The nonlinearity in this model is due to the coupling between the out-of-plane and in-plane deflections and the model allows for moderately large out-of-plane plate deflections. The flapping flag structural model is a nonlinear beam theory which includes nonlinearities due to both large curvature and inertia. The axial deflection in this model is related to the out-of-plane deflection using an axially inextensible theory. The aerodynamic theory used is potential flow theory, which is applicable to low speed flows. The equation which describes potential flow is the Laplace equation, which is a linear partial differential equation. The Laplace equation is solved using a vortex lattice method. Aeroelastic solutions are found using both the classic small disturbance linearized fluid-structure interface boundary condition and the exact nonlinear boundary condition. The aeroelastic model which includes the nonlinear boundary conditions also includes a free wake solution. Several reduced order methods are explored. Normal mode solutions, both for the structural and aerodynamic models, are studied along with a proper orthogonal decomposition model for the aerodynamic flow. A brief description of a parallel implementation of the aeroelastic simulation code is also given and the parallel speedup is shown to be nearly linear for a certain class of problems. Correlation between theory and experiment is presented for both the delta wing and flapping flag model. Several steady angle of attack cases were investigated for the

  1. Synchronization in coupled Ikeda delay systems. Experimental observations using Field Programmable Gate Arrays

    NASA Astrophysics Data System (ADS)

    Valli, D.; Muthuswamy, B.; Banerjee, S.; Ariffin, M. R. K.; Wahab, A. W. A.; Ganesan, K.; Subramaniam, C. K.; Kurths, J.

    2014-06-01

    In this work, we demonstrate the use of a Field Programmable Gate Array (FPGA) as a physical platform for realizing chaotic delay differential equations (DDE). Moreover, using our platform, we also experimentally study the synchronization between two time delayed systems. We illustrate two different experimental approaches - one is hardware co-simulation (using a Digilent Atlys with a Xilinx Spartan-6 FPGA) and the other is analog output (using a Terasic DE2-115 with an Altera Cyclone IV E FPGA).

  2. Experimental Study of Lift-Generated Vortices

    NASA Technical Reports Server (NTRS)

    Rossow, Vernon J.; Nixon, David (Technical Monitor)

    1998-01-01

    The flow fields of vortices, whether bouyancy-driven or lift-generated, are fascinating fluid-dynamic phenomena which often possess intense swirl velocities and complex time-dependent behavior. As part of the on-going study of vortex behavior, this paper presents a historical overview of the research conducted on the structure and modification of the vortices generated by the lifting surfaces of subsonic transport aircraft. It is pointed out that the characteristics of lift-generated vortices are related to the aerodynamic shapes that produce them and that various arrangements of surfaces can be used to produce different vortex structures. The primary purpose of the research to be described is to find a way to reduce the hazard potential of lift-generated vortices shed by subsonic transport aircraft in the vicinity of airports during landing and takeoff operations. It is stressed that lift-generated vortex wakes are so complex that progress towards a solution requires application of a combined theoretical and experimental research program because either alone often leads to incorrect conclusions. It is concluded that a satisfactory aerodynamic solution to the wake-vortex problem at airports has not yet been found but a reduction in the impact of the wake-vortex hazard on airport capacity may become available in the foreseeable future through wake-vortex avoidance concepts currently under study. The material to be presented in this overview is drawn from aerospace journals that are available publicly.

  3. EXPERIMENTAL DESIGN AND INSTRUMENTATION FOR A FIELD EXPERIMENT

    EPA Science Inventory

    This report concerns the design of a field experiment for a military setting in which the effects of carbon monoxide on neurobehavioral variables are to be studied. ield experiment is distinguished from a survey by the fact that independent variables are manipulated, just as in t...

  4. A far-field radio-frequency experimental exposure system with unrestrained mice.

    PubMed

    Hansen, Jared W; Asif, Sajid; Singelmann, Lauren; Khan, Muhammad Saeed; Ghosh, Sumit; Gustad, Tom; Doetkott, Curt; Braaten, Benjamin D; Ewert, Daniel L

    2015-01-01

    Many studies have been performed on exploring the effects of radio-frequency (RF) energy on biological function in vivo. In particular, gene expression results have been inconclusive due, in part, to a lack of a standardized experimental procedure. This research describes a new far field RF exposure system for unrestrained murine models that reduces experimental error. The experimental procedure includes the materials used, the creation of a patch antenna, the uncertainty analysis of the equipment, characterization of the test room, experimental equipment used and setup, power density and specific absorption rate experiment, and discussion. The result of this research is an experimental exposure system to be applied to future biological studies. PMID:26558172

  5. Experimental and simulation studies of alignment marks

    NASA Astrophysics Data System (ADS)

    Wong, Alfred K. K.; Doi, Takeshi; Dunn, Diana D.; Neureuther, Andrew R.

    1991-07-01

    The roles of alignment mark structure, geometry, film materials and scanned illumination image on dark-field alignment signal quality are investigated through simulation interpreted experiments. The illumination of the alignment system consists of a low numerical aperture 1.0 micrometers image of a slit at 488.0 and 514.5 nm which is scanned across the alignment mark. The light scattered into a dark-band protected cone is collected. The structures consist of 0.5 to 1.2 micrometers wide features including trenches in silicon coated with 1.34 micrometers of photoresist, and trenches in nitride coated silicon with 1.00 micrometers of photoresist. For simulation, the illumination image is calculated using SAMPLE and input to a massively parallel finite-difference time-domain scattering analysis program called TEMPEST at various lateral shifts to simulate scanning. The diffracted orders output from TEMPEST are used to calculate total diffracted energy in various angular bands and to view dark field instantaneous images. Studied of depth, width, thin-film stack and coating thickness are used to identify key phenomena such as the role of interference between reflection from the alignment mark and substrate surfaces. Simulations are used to interpret the experimental observations and provide guidelines for topography control, and illumination and collection optics. The alignment signal is shown to be a strong function of trench depth, and only a weak function of trench width. An order of magnitude signal strength reduction occurs when the effective optical depth of the trench is a multiple of (lambda) resist/2 compared to the surrounding area.

  6. Experimental Modeling of Proliferative Vitreoretinopathy. An Experimental Morphological Study.

    PubMed

    Khoroshilova-Maslova, I P; Leparskaya, N L; Nabieva, M M; Andreeva, L D

    2015-05-01

    A model of proliferative vitreoretinopathy induced by simultaneous intravitreal injection of recombinant IL-1β and platelet concentrate is created and its main morphological manifestations are studied on Chinchilla rabbits. The model reflects pathogenesis of proliferative vitreoretinopathy: epiretinal membrane with the formation of retinal plication, traction detachment of the retina; moderate inflammatory reaction in the uveal tract, in the optic nerve infundibulum, in the vitreous body; intact structural elements of the retina, dissociation of the retinal pigmented epithelium cells with their subsequent migration. The model is adequate to the clinical picture of proliferative vitreoretinopathy in humans, which recommends it for experimental studies of the efficiency of drug therapy and prevention of this disease. PMID:26033599

  7. Experimental analysis of a new retarding field energy analyzer

    NASA Astrophysics Data System (ADS)

    Wei, Yu-Xiang; Liu, Shu-Qing; Li, Xian-Xia; Shen, Hong-Li; Huang, Ming-Guang; Liu, Pu-Kun

    2015-06-01

    In this paper, a new compact retarding field energy analyzer (RFEA) is designed for diagnosing electron beams of a K-band space travelling-wave tube (TWT). This analyzer has an aperture plate to sample electron beams and a cylindrical electrode to overcome the defocusing effects. The front end of the analyzer constructed as a multistage depression collector (MDC) structure is intended to shape the field to prevent electrons from being accelerated to escape. The direct-current (DC) beams of the K-band space TWTs with the removing MDC can be investigated on the beam measurement system. The current density distribution of DC beams is determined by the analyzer, while the anode voltage and helix voltage of the TWTs are 7000 V and 6850 V, respectively. The current curve's slope effect due to the reflection of secondary electrons on the copper collector of the analyzer is discussed. The experimental analysis shows this RFEA has a good energy resolution to satisfy the requirement of beam measurement.

  8. Experimental studies of gravity with slow neutrons

    NASA Astrophysics Data System (ADS)

    Kitaguchi, Masaaki; Ichikawa, Go; Hirota, Katsuya; Shimizu, Hirohiko; Sumi, Naoyuki; Matsumoto, Satoru; Yoshioka, Tamaki; Shima, Tatsushi; Mishima, Kenji; Ino, Takashi; Seki, Yoshichika

    2014-09-01

    Neutron is a chargeless massive particle with the lifetime in the macroscopic range, which is suitable for precision measurement of the small influence of new physics including gravity. We have started the experimental studies of the gravity with slow neutrons in order to search non-Newtonian effect at the short range which is lead by the existence of extra-dimension of the space. Combination of the pulsed neutrons provided by J-PARC and the advanced optical devices enables us to perform new types of high precision measurements. Neutron scattering with noble gas target enables us to measure the interaction at the range of the order of 1 nm. The apparatus was installed into beamline NOP and commissioning has been started. Neutron interferometer has the advantage to measure the gravitational potential precisely. We are developing the large-scale interferometer using long-wavelength neutrons, which is realized by using multilayer mirrors. Ultra-cold neutrons in a small cavity can be bound to the discrete energy eigenstates by Earth's gravitational field. We are discussing the direct measurement of the spatial localization of the neutrons with high resolution detectors, for example, CCD and nuclear emulation.

  9. Experimental study and modeling of a novel magnetorheological elastomer isolator

    NASA Astrophysics Data System (ADS)

    Yang, Jian; Du, Haiping; Li, Weihua; Li, Yancheng; Li, Jianchun; Sun, Shuaishuai; Deng, H. X.

    2013-11-01

    This paper reports an experimental setup aiming at evaluating the performance of a newly designed magnetorheological elastomer (MRE) seismic isolator. As a further effort to explore the field-dependent stiffness/damping properties of the MRE isolator, a series of experimental testing were conducted. Based upon the analysis of the experimental responses and the characteristics of the MRE isolator, a new model that is capable of reproducing the unique MRE isolator dynamics behaviors is proposed. The validation results verify the model’s effectiveness to portray the MRE isolator. A study on the field-dependent parameters is then provided to make the model valid with fluctuating magnetic fields. To fully explore the mechanism of the proposed model, an investigation relating the dependence of the proposed model on every parameter is carried out.

  10. Experimental Investigation of Pool Boiling Heat Transfer Enhancement in Microgravity in the Presence of Electric Fields

    NASA Technical Reports Server (NTRS)

    Herman, C.

    2000-01-01

    The research carried out in the Heat Transfer Laboratory of the Johns Hopkins University was motivated by previous studies indicating that in terrestrial applications nucleate boiling heat transfer can be increased by a factor of 50 when compared to values obtained for the same system without electric fields. Imposing an external electric field holds the promise to improve pool boiling heat transfer in low gravity, since a phase separation force other than gravity is introduced. The influence of electric fields on bubble formation has been investigated both experimentally and theoretically.

  11. Experimental design of a waste glass study

    SciTech Connect

    Piepel, G.F.; Redgate, P.E.; Hrma, P.

    1995-04-01

    A Composition Variation Study (CVS) is being performed to support a future high-level waste glass plant at Hanford. A total of 147 glasses, covering a broad region of compositions melting at approximately 1150{degrees}C, were tested in five statistically designed experimental phases. This paper focuses on the goals, strategies, and techniques used in designing the five phases. The overall strategy was to investigate glass compositions on the boundary and interior of an experimental region defined by single- component, multiple-component, and property constraints. Statistical optimal experimental design techniques were used to cover various subregions of the experimental region in each phase. Empirical mixture models for glass properties (as functions of glass composition) from previous phases wee used in designing subsequent CVS phases.

  12. Experimental Investigation on Sandstone Rock Permeability of Pakistan Gas Fields

    NASA Astrophysics Data System (ADS)

    Raza, Arshad; Bing, Chua Han; Nagarajan, Ramasamy; Hamid, Mohamed Ali

    2015-04-01

    Permeability is the ability of formation to produce hydrocarbon which is affected by compaction, pore size, sorting, cementation, layering and clay swelling. The effect of texture on permeability in term of grain size, sorting, sphericity, degree of cementing has been reported in literature. Also, the effect of permeability on capillary pressure, irreducible water saturation, displacement pressure and pore geometry constant has been studied separately. This preliminary study presents the experimental results of eight samples to understand the effect of similar factors of texture on permeability. With the knowledge of the results, it can be said that the effect of grain size, cementation, texture material, sphericity, and porosity can't be observed on permeability except sorting when less than ten samples are considered from different depositional environment. The results also show the impact of permeability on capillary pressure, irreducible water saturation, and displacement pressure and pore geometry index as similar as published in the literature.

  13. [Experimental and clinical studies of flomoxef in the field of obstetrics and gynecology. Representative Committee Members of the Research Team for Infections in the Field of Obstetrics and Gynecology].

    PubMed

    Matsuda, S; Okada, H; Ninomiya, K; Shimizu, T; Noda, K; Deguchi, K

    1988-12-01

    Flomoxef (FMOX) has a broad antibacterial spectrum against Gram-positive and Gram-negative bacteria; especially its potent antibacterial activity against Staphylococcus aureus is a significant advantage that may not be found with other cephem compounds. In our determination of its antibacterial potency against various clinical isolates obtained from clinical materials (amniotic fluid, intrauterine secretions, exudates of the pelvic dead space) of patients with various infections, we obtained results representing specific features of this drug. From the results, the drug may be expected to produce an excellent effect in the treatment of various infections. Our study on drug concentrations in body fluids and genital tissues demonstrated a good transfer of this drug into various tissues; in every tissue examined, the drug administered by the usual method in the usual dose yielded a concentration exceeding MIC for principal pathogens, thus promising a good clinical response. Indeed a high clinical efficacy rate of 90.1% (good to very good responses) was obtained in a clinical trial involving 222 cases. Administration of the drug in 2 g quantity daily produced a high response rate of 92.8%. It was especially noteworthy that a good response was obtained in 30 of 32 cases (93.8%) in which other cephem compounds had failed. In evaluation of the bacteriological effect, furthermore, the drug showed an excellent rate of bacterial elimination. In conclusion, this drug is expected to be greatly useful in the light of its good transfer into genital tissues and its strong antibacterial activities against Gram-positive cocci, Gram-negative bacteria and anaerobes as well as against multiple bacterial infections predominating among women with genital infections. PMID:3074181

  14. (Studies in quantum field theory)

    SciTech Connect

    Not Available

    1990-01-01

    During the period 4/1/89--3/31/90 the theoretical physics group supported by Department of Energy Contract No. AC02-78ER04915.A015 and consisting of Professors Bender and Shrauner, Associate Professor Papanicolaou, Assistant Professor Ogilvie, and Senior Research Associate Visser has made progress in many areas of theoretical and mathematical physics. Professors Bender and Shrauner, Associate Professor Papanicolaou, Assistant Professor Ogilvie, and Research Associate Visser are currently conducting research in many areas of high energy theoretical and mathematical physics. These areas include: strong-coupling approximation; classical solutions of non-Abelian gauge theories; mean-field approximation in quantum field theory; path integral and coherent state representations in quantum field theory; lattice gauge calculations; the nature of perturbation theory in large order; quark condensation in QCD; chiral symmetry breaking; the 1/N expansion in quantum field theory; effective potential and action in quantum field theories, including OCD; studies of the early universe and inflation, and quantum gravity.

  15. Field experimental observations of highly graded sediment plumes.

    PubMed

    Jensen, Jacob Hjelmager; Saremi, Sina; Jimenez, Carlos; Hadjioannou, Louis

    2015-06-15

    A field experiment in the waters off the south-eastern coast of Cyprus was carried out to study near-field formation of sediment plumes from dumping. Different loads of sediment were poured into calm and limpid waters one at the time from just above the sea surface. The associated plumes, gravitating towards the seafloor, were filmed simultaneously by four divers situated at different depths in the water column, and facing the plume at different angles. The processes were captured using GoPro-Hero-series cameras. The high-quality underwater footage from near-surface, mid-depth and near-bed positions gives unique insight into the dynamics of the descending plume and near-field dispersion processes, and enables good understanding of flow and sediment transport processes involved from-release-to-deposition of the load in a non-scaled environment. The high resolution images and footages are available through the link provided herein. Observations support the development of a detailed multi-fractional sediment plume model. PMID:25935811

  16. Experimental and Modeling Studies of Massif Anorthosites

    NASA Technical Reports Server (NTRS)

    Longhi, John

    1999-01-01

    This termination report covers the latter part of a single research effort spanning several grant cycles. During this time there was a single title, "Experimental and Modeling Studies of Massif Anorthosites", but there were several contract numbers as the mode and location of NASA contract administration changed. Initially, the project was funded as an increment to the PI's other grant, "Early Differentiation of the Moon: Experimental and Modeling Studies", but subsequently it became an independent grant. Table 1 contains a brief summary of the dates and contract numbers.

  17. Theoretical and experimental studies of elementary physics

    SciTech Connect

    Bodek, A.; Ferbel, T.; Melissinos, A.C.; Olsen, S.; Slattery, P.; Tipton, P.; Das, A.; Hagen, C.R.; Rajeev, S.G.; Okubo, S.

    1992-04-30

    The experimental high energy physics program is directed toward the execution of experiments that probe the basic constituents of matter and the forces between them. These experiments are carried out at national and international accelerator facilities. At the current time, we are primarily concentrating on the following projects: Direct photon production in hadronic reactions (Fermilab E706); Production of hybrid mesons in the nuclear Coulomb field; The D-Zero experiment at the Tevatron collider; Deep inelastic neutrino- and electron-nucleon scattering at FNAL and SLAC; Nonlinear QED at critical field strengths at SLAC; The Experiments at KEK (AMY, 17keV neutrino); The CDF experiment at the Tevatron collider; and SSC-related detector R D on scintillating tile- and diamond-based calorimetry and microstrip tracking detectors.

  18. Experimental Approaches to Studying Biological Electron Transfer.

    ERIC Educational Resources Information Center

    Scott, Robert A.; And Others

    1985-01-01

    Provides an overview on biological electron-transfer reactions, summarizing what is known about how distance, spatial organization, medium, and other factors affect electron transfer. Experimental approaches, including studies of bimolecular electron transfer reactions (electrostatic effects and precursor complexes), are considered. (JN)

  19. Experimental and computational study of thaumasite structure

    SciTech Connect

    Scholtzová, Eva; Kucková, Lenka; Kožíšek, Jozef; Pálková, Helena; Tunega, Daniel

    2014-05-01

    The structure of thaumasite has been studied experimentally by means of a single crystal X-ray diffraction and FTIR methods, and theoretically using density functional theory (DFT) method. Very good agreement was achieved between calculated and experimental structural parameters. In addition, calculations offered the refinement of the positions of the hydrogen atoms. The detailed analysis of the hydrogen bonds existing in the thaumasite structure has been performed. Several types of hydrogen bonds have been classified. The water molecules coordinating Ca{sup 2+} cation act as proton donors in moderate O-H···O hydrogen bonds formed with CO₃⁻²and SO₄⁻² anions. The multiple O-H···O hydrogen bonds exist among water molecules themselves. Finally, relatively weak hydrogen bonds form water molecules with the OH groups from the coordination sphere of the Si(OH)₆⁻² anion. Further, calculated vibrational spectrum allowed complete assignment of all vibrational modes which are not available from the experimental spectrum that has a complex structure with overlapped bands, especially below 1500 cm⁻¹. Highlights: • The thaumasite structure was studied experimentally and using DFT method. • We used DFT method for the refinement of the positions of hydrogen atoms. • A detailed analysis of the hydrogen bonds was done. • A complete assignment of all bands to particular types of vibrations was done.

  20. Experimental Visualization of Bubble Formation from an Orifice In Microgravity in the Presence of Electric Fields

    NASA Technical Reports Server (NTRS)

    Herman, C.; Iacona, E.; Foldes, I. B.; Suner, G.; Milburn, C.

    2002-01-01

    The formation of air bubbles injected into a stagnant, isothermal liquid in microgravity through an orifice was studied. The bubbles grew very large in microgravity. They attained a nearly spherical shape and showed pronounced affinity towards coalescence in the absence of electric fields and other perturbations. Under the influence of electric fields, periodic detachment was observed, with bubble sizes larger than in terrestrial conditions. The bubble shape was elongated. After detachment, the bubbles moved away from the electrode at which they formed without coalescing with other bubbles. Experimental data on bubble shape and size at detachment showed good agreement with models.

  1. Experimental Investigation of Effectiveness of Magnetic Field on Food Freezing Process

    NASA Astrophysics Data System (ADS)

    Suzuki, Toru; Takeuchi, Yuri; Masuda, Kazunori; Watanabe, Manabu; Shirakashi, Ryo; Fukuda, Yutaka; Tsuruta, Takaharu; Yamamoto, Kazutaka; Koga, Nobumitsu; Hiruma, Naoya; Ichioka, Jun; Takai, Kiyoshi

    Recently, several food refrigeration equipments that utilize magnetic field have attracted much attention from food production companies, consumers and mass media. However, the effectiveness of the freezers is not scientifically examined. Therefore, the effectiveness should be clarified by experiments or theoretical considerations. In this study, the effect of weak magnetic field (about 0.0005 T) on freezing process of several kinds of foods was investigated by using a specially designed freezer facilitated with magnetic field generator. The investigation included the comparison of freezing curves, drip amount, physicochemical evaluations on color and texture, observation of microstructure, and sensory evaluation. From the results of the control experiments, it can be concluded that weak magnetic field around 0.0005 T provided no significant difference on temperature history during freezing and on the qualities of frozen foods, within our experimental conditions.

  2. A Combined Molecular Dynamics and Experimental Study of Doped Polypyrrole.

    PubMed

    Fonner, John M; Schmidt, Christine E; Ren, Pengyu

    2010-10-01

    Polypyrrole (PPy) is a biocompatible, electrically conductive polymer that has great potential for battery, sensor, and neural implant applications. Its amorphous structure and insolubility, however, limit the experimental techniques available to study its structure and properties at the atomic level. Previous theoretical studies of PPy in bulk are also scarce. Using ab initio calculations, we have constructed a molecular mechanics force field of chloride-doped PPy (PPyCl) and undoped PPy. This model has been designed to integrate into the OPLS force field, and parameters are available for the Gromacs and TINKER software packages. Molecular dynamics (MD) simulations of bulk PPy and PPyCl have been performed using this force field, and the effects of chain packing and electrostatic scaling on the bulk polymer density have been investigated. The density of flotation of PPyCl films has been measured experimentally. Amorphous X-ray diffraction of PPyCl was obtained and correlated with atomic structures sampled from MD simulations. The force field reported here is foundational for bridging the gap between experimental measurements and theoretical calculations for PPy based materials. PMID:21052521

  3. A Combined Molecular Dynamics and Experimental Study of Doped Polypyrrole

    PubMed Central

    Fonner, John M.; Schmidt, Christine E.; Ren, Pengyu

    2010-01-01

    Polypyrrole (PPy) is a biocompatible, electrically conductive polymer that has great potential for battery, sensor, and neural implant applications. Its amorphous structure and insolubility, however, limit the experimental techniques available to study its structure and properties at the atomic level. Previous theoretical studies of PPy in bulk are also scarce. Using ab initio calculations, we have constructed a molecular mechanics force field of chloride-doped PPy (PPyCl) and undoped PPy. This model has been designed to integrate into the OPLS force field, and parameters are available for the Gromacs and TINKER software packages. Molecular dynamics (MD) simulations of bulk PPy and PPyCl have been performed using this force field, and the effects of chain packing and electrostatic scaling on the bulk polymer density have been investigated. The density of flotation of PPyCl films has been measured experimentally. Amorphous X-ray diffraction of PPyCl was obtained and correlated with atomic structures sampled from MD simulations. The force field reported here is foundational for bridging the gap between experimental measurements and theoretical calculations for PPy based materials. PMID:21052521

  4. The importance of accurate experimental data to marginal field development

    SciTech Connect

    Overa, S.J.; Lingelem, M.N.

    1997-12-31

    Since exploration started in the Norwegian North Sea in 1965 a total of 196 fields have been discovered. Less than one-third of these fields have been developed. The marginal fields can not be developed economically with current technology even though some of those fields have significant reserves. The total cost to develop one of those large installations is estimated to be 2--5 billion US dollars. Therefore new technology is needed to lower the designed and installed costs of each unit. The need for new physical property data is shown. The value of valid operating data from present units is also pointed out.

  5. Experimental evidence for seismoelectric observations at field scale

    NASA Astrophysics Data System (ADS)

    Holzhauer, Julia; Yaramanci, Ugur

    2010-05-01

    In the past decades, seismoelectric has concentrated a growing interest as a promising tool for hydrogeophysical studies. Resulting from an electrokinetic coupling in porous saturated media traversed by an acoustic wave, this method could ultimately offer a direct access to various hydraulic parameters ranging from porosity to permeability or fluids conductivity. In some other aspects it also occasionally showed some ability to thin-layer resolution. Within the development of the new test-site Schillerslage with typical north-German geology, consisting of two shallow quaternary aquifers separated by a till layer over cretaceous marl, we tested the observability of the seismoelectric signal along with various conventional (seismic, georadar, geoelectric) and unconventional (magnetic resonance sounding -MRS, spectral induced polarisation -SIP) geophysical methods as well as boreholes analysis. The special focus was on the converted seismoelectric signal, an electromagnetic wave acting as a vertical dipole which should theoretically display on the seismoelectrogram as a horizontal arrival. This converted wave appears when the incident acoustic wave meets a hydraulic discontinuity affecting the pore space in any geometrical or chemical manner. This electromagnetic signal fades out rapidly, due to its dipole nature and its weakness, so that its relevance is restricted to the near surface characterisation. In the given setting, such a wave could either initiate at the water table or originate from an abrupt transition from sand to till. Decision was made to record both seismic and seismoelectric signal concomitantly. To allow the detection of the later signal, the field layout was gradually adjusted. Considering the source, hammer-seismic was chosen for its precision in near surface application and automatic trigger-techniques producing major disturbances in the first 10 ms of the seismoelectrogram were abandoned in favour of manual triggering. To avoid any further noise

  6. An experimental study of the glottal jet

    NASA Astrophysics Data System (ADS)

    Jasikova, Darina; Sidlof, Petr; Kotek, Michal; Kopecky, Vaclav

    2016-03-01

    The paper presents results of the flow field analysis in a static scaled model of human larynx. Here we are focused on the effect of the nozzle gap parameter and the incoming flow velocity. The study is performed in the aerodynamic channel using the PIV technique.

  7. [Experimental study of pinostrobine oxime biotransformation].

    PubMed

    Sariev, A K; Abaimov, D A; Tankevich, M V; Prokhorov, D I; Adekenov, S M; Arystan, L I; Seĭfulla, R D

    2014-01-01

    We have experimentally studied pathways of elimination of an oximized derivative of phytoflavonoid pinostrobine by HPLC/mass spectrometry. Four potential metabolites of pinostrobine oxime have been found and there was an attempt to determine their molecular structures on the basis of their fragmentation under positive electrospray ionization conditions. It is established that pinostrobine oxime is removed from the organism mainly unchanged and also in the form of glucuronated derivative. PMID:25335390

  8. Real versus Simulated Mobile Phone Exposures in Experimental Studies

    PubMed Central

    Panagopoulos, Dimitris J.; Johansson, Olle; Carlo, George L.

    2015-01-01

    We examined whether exposures to mobile phone radiation in biological/clinical experiments should be performed with real-life Electromagnetic Fields (EMFs) emitted by commercially available mobile phone handsets, instead of simulated EMFs emitted by generators or test phones. Real mobile phone emissions are constantly and unpredictably varying and thus are very different from simulated emissions which employ fixed parameters and no variability. This variability is an important parameter that makes real emissions more bioactive. Living organisms seem to have decreased defense against environmental stressors of high variability. While experimental studies employing simulated EMF-emissions present a strong inconsistency among their results with less than 50% of them reporting effects, studies employing real mobile phone exposures demonstrate an almost 100% consistency in showing adverse effects. This consistency is in agreement with studies showing association with brain tumors, symptoms of unwellness, and declines in animal populations. Average dosimetry in studies with real emissions can be reliable with increased number of field measurements, and variation in experimental outcomes due to exposure variability becomes less significant with increased number of experimental replications. We conclude that, in order for experimental findings to reflect reality, it is crucially important that exposures be performed by commercially available mobile phone handsets. PMID:26346766

  9. Experimental Evaluation of Field Trips on Instruction in Vocational Agriculture.

    ERIC Educational Resources Information Center

    McCaslin, Norval L.

    To determine the effect of field trips on student achievement in each of four subject matter areas in vocational agriculture, 12 schools offering approved programs were randomly selected and divided into a treatment group and a control group. Uniform teaching outlines and reference materials were provided to each group. While no field trips were…

  10. Feasibility study of the AOSTA experimental campaign

    NASA Astrophysics Data System (ADS)

    Carta, M.; Blaise, P.; Bethaz, C.; Boccia, F.; Fabrizio, V.; Geslot, B.; Grossi, A.; Gruel, A.

    2016-03-01

    The reduction of the nuclear waste is one of the most important nuclear issues. The high radiotoxicity of the spent fuel is due to plutonium and some minor actinides (MAs) such as neptunium, americium and curium, above all. One way to reduce their hazard is to destroy by fission MAs in appropriate nuclear reactors. To allow the MAs destruction an important effort have been done on the nuclear data due to the poor knowledge in this field. In the framework of one of the NEA Expert Group on Integral Experiments for Minor Actinide Management an analysis of the feasibility of MAs irradiation campaign in the TAPIRO fast research reactor is carried out. This paper provides preliminary results obtained by calculations modelling the irradiation, in different TAPIRO irradiation channels, of some CEA samples coming from the French experimental campaign OSMOSE, loaded with different contents of MAs, in order to access, through particular peak spectrometry, to their capture cross section. On the basis of neutron transport calculation results, obtained by both deterministic and Monte Carlo methods, an estimate of the irradiated samples counting levels from the AOSTA (Activation of OSMOSE Samples in TAPIRO) experimental campaign is provided.

  11. Theoretical and experimental studies of reentry plasmas

    NASA Technical Reports Server (NTRS)

    Dunn, M. G.; Kang, S.

    1973-01-01

    A viscous shock-layer analysis was developed and used to calculate nonequilibrium-flow species distributions in the plasma layer of the RAM vehicle. The theoretical electron-density results obtained are in good agreement with those measured in flight. A circular-aperture flush-mounted antenna was used to obtain a comparison between theoretical and experimental antenna admittance in the presence of ionized boundary layers of low collision frequency. The electron-temperature and electron-density distributions in the boundary layer were independently measured. The antenna admittance was measured using a four-probe microwave reflectometer and these measured values were found to be in good agreement with those predicted. Measurements were also performed with another type of circular-aperture antenna and good agreement was obtained between the calculations and the experimental results. A theoretical analysis has been completed which permits calculation of the nonequilibrium, viscous shock-layer flow field for a sphere-cone body. Results are presented for two different bodies at several different altitudes illustrating the influences of bluntness and chemical nonequilibrium on several gas dynamic parameters of interest. Plane-wave transmission coefficients were calculated for an approximate space-shuttle body using a typical trajectory.

  12. Field emission study of carbon nanostructures

    NASA Astrophysics Data System (ADS)

    Zhao, Xin

    Recently, carbon nanosheets (CNS), a novel nanostructure, were developed in our laboratory as a field emission source for high emission current. To characterize, understand and improve the field emission properties of CNS, a ultra-high vacuum surface analysis system was customized to conduct relevant experimental research in four distinct areas. The system includes Auger electron spectroscopy (AES), field emission energy spectroscopy (FEES), field emission I-V testing, and thermal desorption spectroscopy (TDS). Firstly, commercial Mo single tips were studied to calibrate the customized system. AES and FEES experiments indicate that a pyramidal nanotip of Ca and O elements formed on the Mo tip surface by field induced surface diffusion. Secondly, field emission I-V testing on CNS indicates that the field emission properties of pristine nanosheets are impacted by adsorbates. For instance, in pristine samples, field emission sources can be built up instantaneously and be characterized by prominent noise levels and significant current variations. However, when CNS are processed via conditioning (run at high current), their emission properties are greatly improved and stabilized. Furthermore, only H2 desorbed from the conditioned CNS, which indicates that only H adsorbates affect emission. Thirdly, the TDS study on nanosheets revealed that the predominant locations of H residing in CNS are sp2 hybridized C on surface and bulk. Fourthly, a fabricating process was developed to coat low work function ZrC on nanosheets for field emission enhancement. The carbide triple-peak in the AES spectra indicated that Zr carbide formed, but oxygen was not completely removed. The Zr(CxOy) coating was dispersed as nanobeads on the CNS surface. Although the work function was reduced, the coated CNS emission properties were not improved due to an increased beta factor. Further analysis suggest that for low emission current (<1 uA), the H adsorbates affect emission by altering the work

  13. Plant Taxonomy as a Field Study

    ERIC Educational Resources Information Center

    Dalby, D. H.

    1970-01-01

    Suggests methods of teaching plant identification and taxonomic theory using keys, statistical analyses, and biometrics. Population variation, genotype- environment interaction and experimental taxonomy are used in laboratory and field. (AL)

  14. Experimental study of the chaotic waterwheel

    NASA Astrophysics Data System (ADS)

    Rutherford, George; Erxleben, Amy; Rosa, Epaminondas, Jr.

    2007-03-01

    The chaotic waterwheel is often given as an example of a mechanical system that can exhibit chaotic behavior. Its early demonstration by Malkus and the realization that it can be modeled by the Lorenz equations has secured it a prominent place in almost every general presentation of chaos. It seems quite surprising, then, that no experimental investigations of this textbook system have ever been published. To fill this historic gap, and to initiate an experimental study of this incredibly rich dynamic system, our lab has constructed a research-grade waterwheel consisting of a vacuum-formed polycarbonate frame in which 36 cylindrical cells are mounted on an 18 inch diameter. The wheel and its axis can be tilted, and water is fed into the top of the wheel and drains out through thin tubes at the bottom of each cell. An aluminum skirt at the wheel's periphery passes through a variable gap magnet to provide magnetic braking. Angular time series data are collected with an absolute rotary encoder. The data are smoothed and angular velocity and acceleration are calculated via fast fourier transforms. The data show quasi-uniform rotation as well as periodic and chaotic motion and agree fairly well with computer simulations of the idealized wheel equations. We will discuss differences between the experimental data and the simulation predictions as well as plans for future studies.

  15. Experimental Study of Athermal Elastic Network Mechanics

    NASA Astrophysics Data System (ADS)

    Michel, Jonathan; Yunker, Peter

    Recently, significant theoretical effort has been directed towards understanding the mechanics of networks. Elastic networks are of inherent fundamental interest and serve as useful analogs for describing other physical systems. Recent applications include modeling of collagen and descriptions of jamming in granular media and glass formation. I propose to discuss ongoing experimental efforts to study mechanical properties of elastic networks, such as Young's modulus and ultimate strength, in the athermal limit. I will begin with the simple case of regular, isostatic crystalline lattices and proceed to studies of random, connected elastic networks of varying bond number for a given number of lattice sites, including both isostatic and sub-isostatic networks.

  16. Experimental realization of a silicon spin field-effect transistor

    NASA Astrophysics Data System (ADS)

    Huang, Biqin; Monsma, Douwe J.; Appelbaum, Ian

    2007-08-01

    A longitudinal electric field is used to control the transit time (through an undoped silicon vertical channel) of spin-polarized electrons precessing in a perpendicular magnetic field. Since an applied voltage determines the final spin direction at the spin detector and hence the output collector current, this comprises a spin field-effect transistor. An improved hot-electron spin injector providing ≈115% magnetocurrent, corresponding to at least ≈37% electron current spin polarization after transport through 10μm undoped single-crystal silicon, is used for maximum current modulation.

  17. Experimental study of curved guide tubes for pellet injection

    SciTech Connect

    Combs, S.K.; Baylor, L.R.; Foust, C.R.; Gouge, M.J.; Jernigan, T.C.; Milora, S.L.

    1997-12-01

    The use of curved guide tubes for transporting frozen hydrogen pellets offers great flexibility for pellet injection into plasma devices. While this technique has been previously employed, an increased interest in its applicability has been generated with the recent ASDEX Upgrade experimental data for magnetic high-field side (HFS) pellet injection. In these innovative experiments, the pellet penetration appeared to be significantly deeper than for the standard magnetic low-field side injection scheme, along with corresponding greater fueling efficiencies. Thus, some of the major experimental fusion devices are planning experiments with HFS pellet injection. Because of the complex geometries of experimental fusion devices, installations with multiple curved guide tube sections will be required for HFS pellet injection. To more thoroughly understand and document the capability of curved guide tubes, an experimental study is under way at the Oak Ridge National Laboratory (ORNL). In particular, configurations and pellet parameters applicable for the DIII-D tokamak and the International Thermonuclear Experimental Reactor (ITER) were simulated in laboratory experiments. Initial test results with nominal 2.7- and 10-mm-diam deuterium pellets are presented and discussed.

  18. Determining Pressure and Velocity Fields from Experimental Schlieren Data

    NASA Astrophysics Data System (ADS)

    Lee, Frank M.; Allshouse, Michael R.; Morrison, P. J.; Swinney, Harry L.

    2015-11-01

    Internal gravity waves generated by tidal flow over bottom topography in the ocean are important because they contribute significantly to the energy composition of the ocean. Determination of the instantaneous internal wave energy flux requires knowledge of the pressure and velocity fields, each of which is difficult to measure in the ocean or the laboratory. However, the density perturbation field can be measured using a laboratory technique known as ``synthetic schlieren.'' We present an analytical method for deducing both the pressure and velocity fields from the density perturbation field. This yields the instantaneous energy flux of linear internal waves. Our method is verified in tests with data from a Navier-Stokes direct numerical simulation. The method is then applied to laboratory schlieren data obtained for the conditions in the numerical simulations. MRA and HLS were supported by ONR. FML and PJM supported by DOE contract DE-FG02-04ER-54742.

  19. Continuous game dynamics: an experimental study.

    SciTech Connect

    Patelli, P.; Sato, Yuzuru

    2004-01-01

    In this paper we study an experiment with human agents strategically interacting in a game characterized by continuous time and continuous strategy space. The research is focused in studying the agents interaction dynamic under different experimental settings. The agents play a two person game that is an extension of the classic Cournot duopoly. Having agents making decision continuously allows us to track the temporal structure of strategy evolution very precisely. We can follow the agents continuous behavior evolution avoiding the data under-sampling. To our knowledge this is the first attempt to approach experimentally the continuous time decision making. We also emphasize that the focus of our work is not the Cournot model but rather the more general problem of studying the agents strategic interaction dynamic in continuous space time. Flaming the problem as the well studied Cournot Duopoly would be a good starting point. In economics dynamics studies the oligopoly model literature in both discrete and continuous time is one of the richest. There is also a vast literature in experimental economics about repeated games in general and more specifically in duopoly/oligopoly models. Cox and Walker studied whether subjects can learn to play the Cournot Duopoly strategies comparing the experimental results with the theoretical prediction of learning models. The Cox Walker experiment differs from our settings because it is in discrete time and is an evolutionary dynamics framework through a random matching mechanism of the experimental subjects. From the theoretical perspective many works have been focused in studying the Cournot model in a dynamical settings. Okuguchi and Szidarovsky formulated a continuous time version of the Cournot Oligopoly with multiproduct firms. They analyzed the stability of the equilibrium and proved that it is stable, under certain conditions, independently from the value of the adjustments. Chiarella and Khomin extended this analysis to

  20. Experimental and computational investigation of the patient-specific abdominal aortic aneurysm pressure field.

    PubMed

    Antón, R; Chen, C-Y; Hung, M-Y; Finol, E A; Pekkan, K

    2015-07-01

    The objective of the present manuscript is three-fold: (i) to study the detailed pressure field inside a patient-specific abdominal aortic aneurysm (AAA) model experimentally and numerically and discuss its clinical relevance, (ii) to validate a number of possible numerical model options and their ability to predict the experimental pressure field and (iii) to compare the spatial pressure drop in the AAA before and after the formation of intraluminal thrombus (ILT) for a late disease development timeline. A finite volume method was used to solve the governing equations of fluid flow to simulate the flow dynamics in a numerical model of the AAA. Following our patient-specific anatomical rapid prototyping technique, physical models of the aneurysm were created with seven ports for pressure measurement along the blood flow path. A flow loop operating with a blood analogue fluid was used to replicate the patient-specific flow conditions, acquired with phase-contrast magnetic resonance imaging, and measure pressure in the flow model. The Navier-Stokes equations and two turbulent models were implemented numerically to compare the pressure estimations with experimental measurements. The relative pressure difference from experiments obtained with the best performing model (unsteady laminar simulation) was ∼1.1% for the AAA model without ILT and ∼15.4% for the AAA model with ILT (using Reynolds Stress Model). Future investigations should include validation of the 3D velocity field and wall shear stresses within the AAA sac predicted by the three numerical models. PMID:24460046

  1. Experimental study of low frequency drift instability

    SciTech Connect

    Ioffe, M.S.; Kanaev, B.I.; Pastukhov, V.P.

    1994-05-01

    Experimental studies of nondissipative low frequency drift instability are reported; the plasma of a long mirror trap with edge casp anchors was investigated. The instability growth was found to take place only in a limited number of operation modes even in the case of all the growth requirements being satisfied. Furthermore, the instability development is rather moderate, and the associated anomalous losses appear to be small compared to the classical Coulomb losses. Possible factors accounting for the {open_quotes}soft{close_quotes} instability evolution are discussed. 13 refs., 6 figs.

  2. The experimental study on heat rejection equipment

    NASA Astrophysics Data System (ADS)

    Nakagawa, Toshihiko; Atsumi, Masahiro; Tokue, Rinzo

    1992-07-01

    This paper describes the concept study and the experimental work for development of the advanced style expendable heat rejection device. Emphasis is laid on minimizing the hardware weight and using innocuous coolant. Empirical heat transfer characteristics of water spray cooling were obtained and applied to the mathematical model to evaluate the performance. Besides the development of spray nozzle, prototype model of 4 kW class evaporator was fabricated and tested. Heat rejection rate of 3.2-4.5 kW was attained at both (high/low altitude) modes of operation, and feasibility of this heat rejection device was assured.

  3. Experimental Study of Nucleon Structure and QCD

    SciTech Connect

    Jian-Ping Chen

    2012-03-01

    Overview of Experimental Study of Nucleon Structure and QCD, with focus on the spin structure. Nucleon (spin) Structure provides valuable information on QCD dynamics. A decade of experiments from JLab yields these exciting results: (1) valence spin structure, duality; (2) spin sum rules and polarizabilities; (3) precision measurements of g{sub 2} - high-twist; and (4) first neutron transverse spin results - Collins/Sivers/A{sub LT}. There is a bright future as the 12 GeV Upgrade will greatly enhance our capability: (1) Precision determination of the valence quark spin structure flavor separation; and (2) Precision extraction of transversity/tensor charge/TMDs.

  4. Experimental Studying of Dust Particles Charging by Electron Beam

    SciTech Connect

    Gavrikov, A. V.; Fortov, V. E.; Petrov, O. F.; Vorona, N. A.; Vasiliev, M. N.

    2008-09-07

    The studying of the dusty plasma properties under electron beam action are of great interest because it gives the unique opportunities for experimental investigation of strongly coupled systems as well as for developing the new dusty plasma technologies of creating the new composite materials. Highly charged dust particle generates electrostatic field that can accelerate positive ions to high power. It gives the unique possibilities of using these macroparticles (for deeply ions implantation, as catalysts for increasing rate of reactions with the high energy barrier, in the new ionic engines etc.). Presented work deals with the experimental investigation of dust particles charging under direct influence of electron beam. On the basis of experimental data the average velocities of dust particles were obtained and the charge of macroparticle was estimated.

  5. Final Report: Experimental Investigation of Nonlinear Plasma Wake-Fields

    SciTech Connect

    Rosenzweig, J.

    1997-10-31

    We discuss the exploration of the newly proposed blowout regime of the plasma wakefield accelerator and advanced photoinjector technology for linear collider applications. The plasma wakefield experiment at ANL produced several ground-breaking results in the physics of the blowout regime. The photoinjector R and D effort produced breakthroughs in theoretical, computational, and experimental methods in high brightness beam physics. Results have been published.

  6. Field-structured composite studies.

    SciTech Connect

    Martin, James Ellis; Williamson, Rodney L.

    2004-04-01

    Field-structured composites (FSCs) were produced by hosting micron-sized gold-coated nickel particles in a pre-polymer and allowing the mixture to cure in a magnetic field environment. The feasibility of controlling a composite's electrical conductivity using feedback control applied to the field coils was investigated. It was discovered that conductivity in FSCs is primarily determined by stresses in the polymer host matrix due to cure shrinkage. Thus, in cases where the structuring field was uniform and unidirectional so as to produce chainlike structures in the composite, no electrical conductivity was measured until well after the structuring field was turned off at the gel point. In situations where complex, rotating fields were used to generate complex, three-dimensional structures in a composite, very small, but measurable, conductivity was observed prior to the gel point. Responsive, sensitive prototype chemical sensors were developed based on this technology with initial tests showing very promising results.

  7. Computational and experimental analysis of TMS-induced electric field vectors critical to neuronal activation

    NASA Astrophysics Data System (ADS)

    Krieg, Todd D.; Salinas, Felipe S.; Narayana, Shalini; Fox, Peter T.; Mogul, David J.

    2015-08-01

    Objective. Transcranial magnetic stimulation (TMS) represents a powerful technique to noninvasively modulate cortical neurophysiology in the brain. However, the relationship between the magnetic fields created by TMS coils and neuronal activation in the cortex is still not well-understood, making predictable cortical activation by TMS difficult to achieve. Our goal in this study was to investigate the relationship between induced electric fields and cortical activation measured by blood flow response. Particularly, we sought to discover the E-field characteristics that lead to cortical activation. Approach. Subject-specific finite element models (FEMs) of the head and brain were constructed for each of six subjects using magnetic resonance image scans. Positron emission tomography (PET) measured each subject’s cortical response to image-guided robotically-positioned TMS to the primary motor cortex. FEM models that employed the given coil position, orientation, and stimulus intensity in experimental applications of TMS were used to calculate the electric field (E-field) vectors within a region of interest for each subject. TMS-induced E-fields were analyzed to better understand what vector components led to regional cerebral blood flow (CBF) responses recorded by PET. Main results. This study found that decomposing the E-field into orthogonal vector components based on the cortical surface geometry (and hence, cortical neuron directions) led to significant differences between the regions of cortex that were active and nonactive. Specifically, active regions had significantly higher E-field components in the normal inward direction (i.e., parallel to pyramidal neurons in the dendrite-to-axon orientation) and in the tangential direction (i.e., parallel to interneurons) at high gradient. In contrast, nonactive regions had higher E-field vectors in the outward normal direction suggesting inhibitory responses. Significance. These results provide critical new

  8. Experimental study of turbulent flame kernel propagation

    SciTech Connect

    Mansour, Mohy; Peters, Norbert; Schrader, Lars-Uve

    2008-07-15

    Flame kernels in spark ignited combustion systems dominate the flame propagation and combustion stability and performance. They are likely controlled by the spark energy, flow field and mixing field. The aim of the present work is to experimentally investigate the structure and propagation of the flame kernel in turbulent premixed methane flow using advanced laser-based techniques. The spark is generated using pulsed Nd:YAG laser with 20 mJ pulse energy in order to avoid the effect of the electrodes on the flame kernel structure and the variation of spark energy from shot-to-shot. Four flames have been investigated at equivalence ratios, {phi}{sub j}, of 0.8 and 1.0 and jet velocities, U{sub j}, of 6 and 12 m/s. A combined two-dimensional Rayleigh and LIPF-OH technique has been applied. The flame kernel structure has been collected at several time intervals from the laser ignition between 10 {mu}s and 2 ms. The data show that the flame kernel structure starts with spherical shape and changes gradually to peanut-like, then to mushroom-like and finally disturbed by the turbulence. The mushroom-like structure lasts longer in the stoichiometric and slower jet velocity. The growth rate of the average flame kernel radius is divided into two linear relations; the first one during the first 100 {mu}s is almost three times faster than that at the later stage between 100 and 2000 {mu}s. The flame propagation is slightly faster in leaner flames. The trends of the flame propagation, flame radius, flame cross-sectional area and mean flame temperature are related to the jet velocity and equivalence ratio. The relations obtained in the present work allow the prediction of any of these parameters at different conditions. (author)

  9. An experimental Lagrangian study of inhomgeneous turbulence

    NASA Astrophysics Data System (ADS)

    Stelzenmuller, Nickolas; Mordant, Nicolas

    2015-11-01

    We investigate experimentally the Lagrangian properties of inhomogeneous turbulence in the general scope of dispersion studies in natural and industrial flows. Lagrangian studies of homogeneous turbulence are becoming common, but very little Lagrangian experimental data exists for inhomogeneous turbulence despite the vast range of applications. Particle tracking velocimetry using a very high speed camera in a fully developed turbulent channel flow in water is achieved at ReH = 33 , 000 . This technique provides Lagrangian velocity and acceleration statistics fully resolved at the smallest turbulent scales near the wall. These statistics, conditioned by the distance to the wall, allow the the investigation of the inhomogeneity of the statistical properties of this flow. Autocorrelations of velocity and acceleration show increasing Lagrangian turbulent scales as distance from the wall increases, as well as decreasing anisotropy. PDF's and moments of Lagrangian quantities are presented by showing the evolution of structure functions across the boundary layer. These results are compared to direct numerical simulation results from a similar flow, and their implications for stochastic models of inhomogeneous flows are discussed.

  10. Experimental Identification of Electric Field Excitation Mechanisms in a Structural Transition of Tokamak Plasmas.

    PubMed

    Kobayashi, T; Itoh, K; Ido, T; Kamiya, K; Itoh, S-I; Miura, Y; Nagashima, Y; Fujisawa, A; Inagaki, S; Ida, K; Hoshino, K

    2016-01-01

    Self-regulation between structure and turbulence, which is a fundamental process in the complex system, has been widely regarded as one of the central issues in modern physics. A typical example of that in magnetically confined plasmas is the Low confinement mode to High confinement mode (L-H) transition, which is intensely studied for more than thirty years since it provides a confinement improvement necessary for the realization of the fusion reactor. An essential issue in the L-H transition physics is the mechanism of the abrupt "radial" electric field generation in toroidal plasmas. To date, several models for the L-H transition have been proposed but the systematic experimental validation is still challenging. Here we report the systematic and quantitative model validations of the radial electric field excitation mechanism for the first time, using a data set of the turbulence and the radial electric field having a high spatiotemporal resolution. Examining time derivative of Poisson's equation, the sum of the loss-cone loss current and the neoclassical bulk viscosity current is found to behave as the experimentally observed radial current that excites the radial electric field within a few factors of magnitude. PMID:27489128

  11. Experimental Identification of Electric Field Excitation Mechanisms in a Structural Transition of Tokamak Plasmas

    PubMed Central

    Kobayashi, T.; Itoh, K.; Ido, T.; Kamiya, K.; Itoh, S.-I.; Miura, Y.; Nagashima, Y.; Fujisawa, A.; Inagaki, S.; Ida, K.; Hoshino, K.

    2016-01-01

    Self-regulation between structure and turbulence, which is a fundamental process in the complex system, has been widely regarded as one of the central issues in modern physics. A typical example of that in magnetically confined plasmas is the Low confinement mode to High confinement mode (L-H) transition, which is intensely studied for more than thirty years since it provides a confinement improvement necessary for the realization of the fusion reactor. An essential issue in the L-H transition physics is the mechanism of the abrupt “radial” electric field generation in toroidal plasmas. To date, several models for the L-H transition have been proposed but the systematic experimental validation is still challenging. Here we report the systematic and quantitative model validations of the radial electric field excitation mechanism for the first time, using a data set of the turbulence and the radial electric field having a high spatiotemporal resolution. Examining time derivative of Poisson’s equation, the sum of the loss-cone loss current and the neoclassical bulk viscosity current is found to behave as the experimentally observed radial current that excites the radial electric field within a few factors of magnitude. PMID:27489128

  12. Experimental Identification of Electric Field Excitation Mechanisms in a Structural Transition of Tokamak Plasmas

    NASA Astrophysics Data System (ADS)

    Kobayashi, T.; Itoh, K.; Ido, T.; Kamiya, K.; Itoh, S.-I.; Miura, Y.; Nagashima, Y.; Fujisawa, A.; Inagaki, S.; Ida, K.; Hoshino, K.

    2016-08-01

    Self-regulation between structure and turbulence, which is a fundamental process in the complex system, has been widely regarded as one of the central issues in modern physics. A typical example of that in magnetically confined plasmas is the Low confinement mode to High confinement mode (L-H) transition, which is intensely studied for more than thirty years since it provides a confinement improvement necessary for the realization of the fusion reactor. An essential issue in the L-H transition physics is the mechanism of the abrupt “radial” electric field generation in toroidal plasmas. To date, several models for the L-H transition have been proposed but the systematic experimental validation is still challenging. Here we report the systematic and quantitative model validations of the radial electric field excitation mechanism for the first time, using a data set of the turbulence and the radial electric field having a high spatiotemporal resolution. Examining time derivative of Poisson’s equation, the sum of the loss-cone loss current and the neoclassical bulk viscosity current is found to behave as the experimentally observed radial current that excites the radial electric field within a few factors of magnitude.

  13. Numerical and Experimental Determination of the Geometric Far Field for Round Jets

    NASA Technical Reports Server (NTRS)

    Koch, L. Danielle; Bridges, James; Brown, Cliff; Khavaran, Abbas

    2003-01-01

    To reduce ambiguity in the reporting of far field jet noise, three round jets operating at subsonic conditions have recently been studied at the NASA Glenn Research Center. The goal of the investigation was to determine the location of the geometric far field both numerically and experimentally. The combination of the WIND Reynolds-Averaged Navier-Stokes solver and the MGBK jet noise prediction code was used for the computations, and the experimental data was collected in the Aeroacoustic Propulsion Laboratory. While noise sources are distributed throughout the jet plume, at great distances from the nozzle the noise will appear to be emanating from a point source and the assumption of linear propagation is valid. Closer to the jet, nonlinear propagation may be a problem, along with the known geometric issues. By comparing sound spectra at different distances from the jet, both from computational methods that assume linear propagation, and from experiments, the contributions of geometry and nonlinearity can be separately ascertained and the required measurement distance for valid experiments can be established. It is found that while the shortest arc considered here (approx. 8D) was already in the geometric far field for the high frequency sound (St greater than 2.0), the low frequency noise due to its extended source distribution reached the geometric far field at or about 50D. It is also found that sound spectra at far downstream angles does not strictly scale on Strouhal number, an observation that current modeling does not capture.

  14. Experimental Measurement of the Flow Field of Heavy Trucks

    SciTech Connect

    Fred Browand; Charles Radovich

    2005-05-31

    Flat flaps that enclose the trailer base on the sides and top are known to reduce truck drag and reduce fuel consumption. Such flapped-truck geometries have been studied in laboratory wind tunnels and in field tests. A recent review of wind tunnel data for a variety of truck geometries and flow Reynolds numbers show roughly similar values of peak drag reduction, but differ in the determination of the optimum flap angle. Optimum angles lie in the range 12 degrees-20 degrees, and may be sensitive to Reynolds number and truck geometry. The present field test is undertaken to provide additional estimates of the magnitude of the savings to be expected on a typical truck for five flap angles 10, 13, 16, 19, and 22 degrees. The flaps are constructed from a fiberglass-epoxy-matrix material and are one-quarter of the base width in length (about 61 cm, or 2 feet). They are attached along the rear door hinge lines on either side of the trailer, so that no gap appears at the joint between the flap and the side of the trailer The flap angle is adjusted by means of two aluminum supports. The present test is performed on the NASA Crows Landing Flight Facility at the northern end of the San Joaquin valley in California. The main runway is approximately 2400 meters in length, and is aligned approximately in a north-south direction The test procedure is to make a series of runs starting at either end of the runway. All runs are initiated under computer control to accelerate the truck to a target speed of 60 mph (96 6 km/hr), to proceed at the target speed for a fixed distance, and to decelerate at the far end of the runway. During a run, the broadcast fuel rate, the engine rpm, forward speed, elapsed time--as well as several other parameters (10 in all)--are digitized at a rate of 100 digitizations per second. Various flapped-conditions are interspersed with the ''no flaps'' control, and are sequenced in a different order on different days. Approximately 310 runs are accumulated

  15. Improved field experimental designs and quantitative evaluation of aquatic ecosystems

    SciTech Connect

    McKenzie, D.H.; Thomas, J.M.

    1984-05-01

    The paired-station concept and a log transformed analysis of variance were used as methods to evaluate zooplankton density data collected during five years at an electrical generation station on Lake Michigan. To discuss the example and the field design necessary for a valid statistical analysis, considerable background is provided on the questions of selecting (1) sampling station pairs, (2) experimentwise error rates for multi-species analyses, (3) levels of Type I and II error rates, (4) procedures for conducting the field monitoring program, and (5) a discussion of the consequences of violating statistical assumptions. Details for estimating sample sizes necessary to detect changes of a specified magnitude are included. Both statistical and biological problems with monitoring programs (as now conducted) are addressed; serial correlation of successive observations in the time series obtained was identified as one principal statistical difficulty. The procedure reduces this problem to a level where statistical methods can be used confidently. 27 references, 4 figures, 2 tables.

  16. Wide-field Fizeau imaging telescope: experimental results.

    PubMed

    Kendrick, R L; Aubrun, Jean-Noel; Bell, Ray; Benson, Robert; Benson, Larry; Brace, David; Breakwell, John; Burriesci, Larry; Byler, Eric; Camp, John; Cross, Gene; Cuneo, Peter; Dean, Peter; Digumerthi, Ramji; Duncan, Alan; Farley, John; Green, Andy; Hamilton, Howard H; Herman, Bruce; Lauraitis, Kris; de Leon, Erich; Lorell, Kenneth; Martin, Rob; Matosian, Ken; Muench, Tom; Ni, Mel; Palmer, Alice; Roseman, Dennis; Russell, Sheldon; Schweiger, Paul; Sigler, Rob; Smith, John; Stone, Richard; Stubbs, David; Swietek, Gregg; Thatcher, John; Tischhauser, C; Wong, Harvey; Zarifis, Vassilis; Gleichman, Kurt; Paxman, Rick

    2006-06-20

    A nine-aperture, wide-field Fizeau imaging telescope has been built at the Lockheed-Martin Advanced Technology Center. The telescope consists of nine, 125 mm diameter collector telescopes coherently phased and combined to form a diffraction-limited image with a resolution that is consistent with the 610 mm diameter of the telescope. The phased field of view of the array is 1 murad. The measured rms wavefront error is 0.08 waves rms at 635 nm. The telescope is actively controlled to correct for tilt and phasing errors. The control sensing technique is the method known as phase diversity, which extracts wavefront information from a pair of focused and defocused images. The optical design of the telescope and typical performance results are described. PMID:16778931

  17. Experimental Study of Top Heat Mode Thermosyphon

    NASA Astrophysics Data System (ADS)

    Hirashima, Masao; Kimura, Kenichiro; Utsumi, Yoichi; Kimura, Kenichi; Negishi, Kanji

    The purpose of this study is to develop the top heat mode thermosyphon that is very attractive means, for example, to accumulate directly the summer solar energy into the underground soil for the winter season. In this case, it can exclude the complex piping and mechanical pump to circulate the hot water absorbed the solar energy through the piping system buried in the soil layer. The several ideas concerning the top heat thermosyphon had been proposed, however, there were few reports on the definite experiments. The authors have carried out the experimental study of the top heat mode thermosyphon, with a simple lifting pipe, which could draw the working liquid from the under condenser to the upper evaporator section. The improvement of the main construction parts such as evaporator, lifting pipe, liquid reservoir trap and vapour nozzle have been performed in the present experiment in order to obtain the optimum operation range.

  18. Experimental studies on coaxial vortex loops

    NASA Astrophysics Data System (ADS)

    Mariani, R.; Kontis, K.

    2010-12-01

    An experimental study has been conducted on the formation and propagation of coaxial vortex loops using a shock tube facility. The study aimed at evaluating the flow characteristics of pairs of corotating vortex rings that generate the leapfrogging phenomenon. The driver and driven gas of the shock tube were air. Three driver pressures were used (4, 8, and 12 bars) with the driven gas being at ambient conditions. The Mach numbers of the shock wave generated inside the shock tube were 1.34, 1.54, and 1.66, respectively. The sudden expansion present at the diaphragm location effectively decreased the Mach number value of the traveling shock wave. Results showed that a pair of vortex rings staggered with respect to time and with the same direction rotation lead to leapfrogging. Results also indicated that the number of leapfrogging occurrences is related to the Reynolds number of the vortex ring pairs with a decrease in leapfrogs at higher Reynolds numbers.

  19. Insights into Arbovirus Evolution and Adaptation from Experimental Studies

    PubMed Central

    Ciota, Alexander T.; Kramer, Laura D.

    2010-01-01

    Arthropod-borne viruses (arboviruses) are maintained in nature by cycling between vertebrate hosts and haematophagous invertebrate vectors. These viruses are responsible for causing a significant public health burden throughout the world, with over 100 species having the capacity to cause human disease. Arbovirus outbreaks in previously naïve environments demonstrate the potential of these pathogens for expansion and emergence, possibly exacerbated more recently by changing climates. These recent outbreaks, together with the continued devastation caused by endemic viruses, such as Dengue virus which persists in many areas, demonstrate the need to better understand the selective pressures that shape arbovirus evolution. Specifically, a comprehensive understanding of host-virus interactions and how they shape both host-specific and virus-specific evolutionary pressures is needed to fully evaluate the factors that govern the potential for host shifts and geographic expansions. One approach to advance our understanding of the factors influencing arbovirus evolution in nature is the use of experimental studies in the laboratory. Here, we review the contributions that laboratory passage and experimental infection studies have made to the field of arbovirus adaptation and evolution, and how these studies contribute to the overall field of arbovirus evolution. In particular, this review focuses on the areas of evolutionary constraints and mutant swarm dynamics; how experimental results compare to theoretical predictions; the importance of arbovirus ecology in shaping viral swarms; and how current knowledge should guide future questions relevant to understanding arbovirus evolution. PMID:21994633

  20. Studies in quantum field theory

    NASA Astrophysics Data System (ADS)

    Polmar, S. K.

    The theoretical physics group at Washington University has been devoted to the solution of problems in theoretical and mathematical physics. All of the personnel on this task have a similar approach to their research in that they apply sophisticated analytical and numerical techniques to problems primarily in quantum field theory. Specifically, this group has worked on quantum chromodynamics, classical Yang-Mills fields, chiral symmetry breaking condensates, lattice field theory, strong-coupling approximations, perturbation theory in large order, nonlinear waves, 1/N expansions, quantum solitons, phase transitions, nuclear potentials, and early universe calculations.

  1. Field enhancement factor dependence on electric field and implications on microscale gas breakdown: Theory and experimental interpretation

    NASA Astrophysics Data System (ADS)

    Alejandro Buendia, Jose; Venkattraman, Ayyaswamy

    2015-12-01

    In this letter, we obtain a better understanding of effective field enhancement factors (β eff) in the context of microscale gas breakdown with specific emphasis on its dependence on applied electric field. The theoretical dependence of β eff on electric field for various hemi-ellipsoidal asperities indicates that the value of β eff decreases with increasing electric field. The interpretation of experimental data using a typical one-dimensional modified Paschen law indicates a qualitatively similar electric field dependence even though the data could not be completely explained using a single effective asperity size. The values of β eff extracted from seven independent experimental datasets for microscale breakdown of argon and air are shown to be consistent and an empirical dependence on electric field is determined.

  2. Experimental approaches to studying cumulative cultural evolution

    PubMed Central

    Caldwell, Christine A.; Atkinson, Mark; Renner, Elizabeth

    2016-01-01

    In humans, cultural traditions often change in ways which increase efficiency and functionality. This process, widely referred to as cumulative cultural evolution, sees beneficial traits preferentially retained, and it is so pervasive that we may be inclined to take it for granted. However, directional change of this kind appears to distinguish human cultural traditions from behavioural traditions that have been documented in other animals. Cumulative culture is therefore attracting an increasing amount of attention within psychology, and researchers have begun to develop methods of studying this phenomenon under controlled conditions. These studies have now addressed a number of different questions, including which learning mechanisms may be implicated, and how the resulting behaviours may be influenced by factors such as population structure. The current article provides a synopsis of some of these studies, and highlights some of the unresolved issues in this field. PMID:27397972

  3. Experimental studies of auroral arc generators

    SciTech Connect

    Suszcynsky, D.M.; Borovsky, J.E.; Thomsen, M.F.

    1997-08-01

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). An all-sky video camera system was deployed in Eagle, Alaska at the foot of the magnetic field line that threads geosynchronous satellite 1989-046 as part of a campaign to study correlations of ground-based auroral activity with satellite-based plasma and energetic particle measurements. The overall intent of the project was to study magnetosphere-ionosphere coupling as it relates to the aurora, and, in particular, to look for signatures that may help to identify various auroral generator mechanism(s). During this study, our efforts were primarily directed towards identifying the generator mechanism(s) for pulsating aurora. Our data, though not conclusive, are found to support theories that propose a cyclotron resonance mechanism for the generation of auroral pulsations.

  4. Experimental study of fracture processes in rock

    NASA Astrophysics Data System (ADS)

    Maji, A. K.; Wang, J. L.

    1992-01-01

    The Fracture process zone in compact tension specimens of Indiana limestone was investigated to study its effect on the fracture mechanics parameters in such materials. Specimens were tested up to the peak load, and propagation of the crack from a preexisting notch was monitored. Experiments were designed to study the two features of the fracture process zone in rocks: ligament connections and microcracking. To observe this zone with high sensitivity and accuracy, laser interferometry methods were adopted. Holographic Interferometry was used to observe initial crack propagation. To obtain more quantitative measurements of the displacement field, in realtime, the recently developed technique of electronic speckle pattern interferometry was applied. This technique can provide continuous video recording of the interferometric fringe pattern, depict the evolution of the fracture process, and measure profiles of crack opening displacements. The macroscopic observations of full-field displacement by the laser techniques were supplemented by post mortem observation of the fracture region under a scanning electron microscope. Regions around the crack were studied after the test for possible presence of microcracks. An interactive finite element code was used to compute the stress intensity factors of the propagating crack-tip and displacements. Finite element computations were used to evaluate the effect of the process zone on crack propagation.

  5. Experimental and modeling study on char combustion

    SciTech Connect

    J. Yu; M.C. Zhang

    2009-05-15

    In this study, on the basis of experimental verifications with an FTIR online measurement system, theoretical calculations by using the strict continuous-film model were first compared with those by the simple single-film model that is still widely used in mathematical modeling of pulverized coal flames. The results indicated that the single-film model has some significant errors in its predictions of the ignition temperature and the combustion following ignition and hence should have some restrictions on its application. Then an improved char combustion model has been presented, taking into consideration the influence of the finite-rate heterogeneous reduction and oxidation reactions. This model gives the explicit algebraic expressions for the overall rate of combustion, the surface temperature of the particle, and the gas temperature at the flame sheet. Compared with the single-film model, predictions by the present model were in much better agreement with those predicted by the continuous-film model and the experimental data. The novel model is also much easier to be integrated into the comprehensive computing codes for industrial pulverized coal flame than the continuous-film model. 21 refs., 14 figs.

  6. [Chemoprophylaxis of secondary peritoneal hydatidosis. Experimental study].

    PubMed

    Errasti Alustiza, J; Arévalo Alonso, J M; Ortiz Tudanca, J; Rebollar Saenz, J; Martínez Blázquez, C; Vítores López, J M

    1993-09-01

    We have studied the effectiveness of pharmacologic prophylaxis of experimental peritoneal hydatidosis. Mice (n = 140, divided in ten groups) suffered intraperitoneal contamination with protoscoleces of E. granulosus from sheep. Each group received different treatment (mebendazole, praziquantel, or both), in three different schedules (during 3 days before contamination, during 7 days after contamination, or both before and after Mebendazole 150 mg/kg-day), praziquantel (25 mg/kg-day) were given in three daily doses. Mice were sacrificed six months later and the number and type of existing peritoneal cysts was recorded. Prophylaxis prior to contamination was shown ineffective. Early treatment greatly decreased the severity of the peritoneal hydatidosis. The administration of the drug before and after contamination, did not improve the results obtained when the drug was given after contamination. Both mebendazole and praziquantel were effective, though the former obtained better results. The association of both drugs does not improve the results obtained with mebendazole alone. These experimental results recommend the early use of mebendazol or praziquantel after open surgery for hydatidosis, in order to prevent the occurrence of secondary peritoneal hydatidosis. PMID:8217380

  7. Planned waveguide electric field breakdown studies

    SciTech Connect

    Wang Faya; Li Zenghai

    2012-12-21

    This paper presents an experimental setup for X-band rf breakdown studies. The setup is composed of a section of WR90 waveguide with a tapered pin located at the middle of the waveguide E-plane. Another pin is used to rf match the waveguide so it operates in a travelling wave mode. By adjusting the penetration depth of the tapered pin, different surface electric field enhancements can be obtained. The setup will be used to study the rf breakdown rate dependence on power flow in the waveguide for a constant maximum surface electric field on the pin. Two groups of pins have been designed. The Q of one group is different and very low. The other has a similar Q. With the test of the two groups of pins, we should be able to discern how the net power flow and Q affect the breakdown. Furthermore, we will apply an electron beam treatment to the pins to study its effect on breakdown. Overall, these experiments should be very helpful in understanding rf breakdown phenomena and could significantly benefit the design of high gradient accelerator structures.

  8. Experimental Demonstration of Anomalous Field Enhancement in All-Dielectric Transition Magnetic Metamaterials

    NASA Astrophysics Data System (ADS)

    Sun, Jingbo; Liu, Xiaoming; Zhou, Ji; Kudyshev, Zhaxylyk; Litchinitser, Natalia M.

    2015-11-01

    Anomalous field enhancement accompanied by resonant absorption phenomenon was originally discussed in the context of plasma physics and in applications related to radio-communications between the ground and spacecraft returning to Earth. Indeed, there is a critical period of time when all communications are lost due to the reflection/absorption of electromagnetic waves by the sheath of plasma created by a high speed vehicle re-entering the atmosphere. While detailed experimental studies of these phenomena in space are challenging, the emergence of electromagnetic metamaterials enables researchers exceptional flexibility to study them in the laboratory environment. Here, we experimentally demonstrated the strong localized field enhancement of magnetic field for an electromagnetic wave propagating in Mie-resonance-based inhomogeneous metamaterials with magnetic permeability gradually changing from positive to negative values. Although these experiments were performed in the microwave frequency range, the proposed all-dielectric approach to transition metamaterials can be extended to terahertz, infrared, and visible frequencies. We anticipate that these results, besides most basic science aspects, hold the potential for numerous applications, including low-intensity nonlinear transformation optics, topological photonics, and the broader area of surface and interface science.

  9. Experimental Demonstration of Anomalous Field Enhancement in All-Dielectric Transition Magnetic Metamaterials

    PubMed Central

    Sun, Jingbo; Liu, Xiaoming; Zhou, Ji; Kudyshev, Zhaxylyk; Litchinitser, Natalia M.

    2015-01-01

    Anomalous field enhancement accompanied by resonant absorption phenomenon was originally discussed in the context of plasma physics and in applications related to radio-communications between the ground and spacecraft returning to Earth. Indeed, there is a critical period of time when all communications are lost due to the reflection/absorption of electromagnetic waves by the sheath of plasma created by a high speed vehicle re-entering the atmosphere. While detailed experimental studies of these phenomena in space are challenging, the emergence of electromagnetic metamaterials enables researchers exceptional flexibility to study them in the laboratory environment. Here, we experimentally demonstrated the strong localized field enhancement of magnetic field for an electromagnetic wave propagating in Mie-resonance-based inhomogeneous metamaterials with magnetic permeability gradually changing from positive to negative values. Although these experiments were performed in the microwave frequency range, the proposed all-dielectric approach to transition metamaterials can be extended to terahertz, infrared, and visible frequencies. We anticipate that these results, besides most basic science aspects, hold the potential for numerous applications, including low-intensity nonlinear transformation optics, topological photonics, and the broader area of surface and interface science. PMID:26531855

  10. Experimental Demonstration of Anomalous Field Enhancement in All-Dielectric Transition Magnetic Metamaterials.

    PubMed

    Sun, Jingbo; Liu, Xiaoming; Zhou, Ji; Kudyshev, Zhaxylyk; Litchinitser, Natalia M

    2015-01-01

    Anomalous field enhancement accompanied by resonant absorption phenomenon was originally discussed in the context of plasma physics and in applications related to radio-communications between the ground and spacecraft returning to Earth. Indeed, there is a critical period of time when all communications are lost due to the reflection/absorption of electromagnetic waves by the sheath of plasma created by a high speed vehicle re-entering the atmosphere. While detailed experimental studies of these phenomena in space are challenging, the emergence of electromagnetic metamaterials enables researchers exceptional flexibility to study them in the laboratory environment. Here, we experimentally demonstrated the strong localized field enhancement of magnetic field for an electromagnetic wave propagating in Mie-resonance-based inhomogeneous metamaterials with magnetic permeability gradually changing from positive to negative values. Although these experiments were performed in the microwave frequency range, the proposed all-dielectric approach to transition metamaterials can be extended to terahertz, infrared, and visible frequencies. We anticipate that these results, besides most basic science aspects, hold the potential for numerous applications, including low-intensity nonlinear transformation optics, topological photonics, and the broader area of surface and interface science. PMID:26531855

  11. On the proper study design applicable to experimental balneology

    NASA Astrophysics Data System (ADS)

    Varga, Csaba

    2015-11-01

    The simple message of this paper is that it is the high time to reevaluate the strategies and optimize the efforts for investigation of thermal (spa) waters. Several articles trying to clear mode of action of medicinal waters have been published up to now. Almost all studies apply the unproven hypothesis, namely the inorganic ingredients are in close connection with healing effects of bathing. Change of paradigm would be highly necessary in this field taking into consideration the presence of several biologically active organic substances in these waters. A successful design for experimental mechanistic studies is approved.

  12. On the proper study design applicable to experimental balneology.

    PubMed

    Varga, Csaba

    2016-08-01

    The simple message of this paper is that it is the high time to reevaluate the strategies and optimize the efforts for investigation of thermal (spa) waters. Several articles trying to clear mode of action of medicinal waters have been published up to now. Almost all studies apply the unproven hypothesis, namely the inorganic ingredients are in close connection with healing effects of bathing. Change of paradigm would be highly necessary in this field taking into consideration the presence of several biologically active organic substances in these waters. A successful design for experimental mechanistic studies is approved. PMID:26597677

  13. On the proper study design applicable to experimental balneology

    NASA Astrophysics Data System (ADS)

    Varga, Csaba

    2016-08-01

    The simple message of this paper is that it is the high time to reevaluate the strategies and optimize the efforts for investigation of thermal (spa) waters. Several articles trying to clear mode of action of medicinal waters have been published up to now. Almost all studies apply the unproven hypothesis, namely the inorganic ingredients are in close connection with healing effects of bathing. Change of paradigm would be highly necessary in this field taking into consideration the presence of several biologically active organic substances in these waters. A successful design for experimental mechanistic studies is approved.

  14. Experimental research in aerodynamic control with electric and electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Braun, E. M.; Lu, F. K.; Wilson, D. R.

    2009-01-01

    Fifty years ago, publications began to discuss the possibilities of electromagnetic flow control (EMFC) to improve aerodynamic performance. This led to an era of research that focused on coupling the fundamentals of magnetohydrodynamics (MHD) with propulsion, control, and power generation systems. Unfortunately, very few designs made it past an exploratory phase as, among other issues, power consumption was unreasonably high. Recent proposed advancements in technology like the MARIAH hypersonic wind tunnel and the AJAX scramjet engine concepts have led to a new phase of MHD research in the aerospace industry, with many interdisciplinary applications. Compared with propulsion systems and channel flow accelerators, EMFC concepts applied to control surface aerodynamics have not seen the same level of advancement that may eventually produce a device that can be integrated with an aircraft or missile. The purpose of this paper is to review the overall feasibility of the different electric and EMFC concepts. Emphasis is placed on EMFC with high voltage ionization sources and experimental work.

  15. Molecular simulations and experimental studies of zeolites

    NASA Astrophysics Data System (ADS)

    Moloy, Eric C.

    Zeolites are microporous aluminosilicate tetrahedral framework materials that have symmetric cages and channels with open-diameters between 0.2 and 2.0 nm. Zeolites are used extensively in the petrochemical industries for both their microporosity and their catalytic properties. The role of water is paramount to the formation, structure, and stability of these materials. Zeolites frequently have extra-framework cations, and as a result, are important ion-exchange materials. Zeolites also play important roles as molecular sieves and catalysts. For all that is known about zeolites, much remains a mystery. How, for example, can the well established metastability of these structures be explained? What is the role of water with respect to the formation, stabilization, and dynamical properties? This dissertation addresses these questions mainly from a modeling perspective, but also with some experimental work as well. The first discussion addresses a special class of zeolites: pure-silica zeolites. Experimental enthalpy of formation data are combined with molecular modeling to address zeolitic metastability. Molecular modeling is used to calculate internal surface areas, and a linear relationship between formation enthalpy and internal surface areas is clearly established, producing an internal surface energy of approximately 93 mJ/m2. Nitrate bearing sodalite and cancrinite have formed under the caustic chemical conditions of some nuclear waste processing centers in the United States. These phases have fouled expensive process equipment, and are the primary constituents of the resilient heels in the bottom of storage tanks. Molecular modeling, including molecular mechanics, molecular dynamics, and density functional theory, is used to simulate these materials with respect to structure and dynamical properties. Some new, very interesting results are extracted from the simulation of anhydrous Na6[Si6Al 6O24] sodalite---most importantly, the identification of two distinct

  16. Free will and consciousness: experimental studies.

    PubMed

    Shepherd, Joshua

    2012-06-01

    What are the folk-conceptual connections between free will and consciousness? In this paper I present results which indicate that consciousness plays central roles in folk conceptions of free will. When conscious states cause behavior, people tend to judge that the agent acted freely. And when unconscious states cause behavior, people tend to judge that the agent did not act freely. Further, these studies contribute to recent experimental work on folk philosophical affiliation, which analyzes folk responses to determine whether folk views are consistent with the view that free will and determinism are incompatible (incompatibilism) or with the opposite view (compatibilism). Conscious causation of behavior tends to elicit pro-free will judgments, even when the causation takes place deterministically. Thus, when controlling for consciousness, many folk seem to be compatibilists. However, participants who disagree with the deterministic or cognitive scientific descriptions given of human behavior tend to give incompatibilist responses. PMID:22480780

  17. [Brackets and friction in orthodontics: experimental study].

    PubMed

    Ben Rejeb Jdir, Saloua; Tobji, Samir; Turki, Wiem; Dallel, Ines; Khedher, Nedra; Ben Amor, Adel

    2015-09-01

    Many authors have been involved in developing brackets in order to improve the quality, stability, speed and efficiency of orthodontic treatment. In order to reduce friction between bracket and archwire, new therapeutic approaches have been devised based on novel technologies. Among these innovative techniques, self-ligating brackets are increasingly popular. SLBs can be classified into several categories according to their mode of action and their materials. We performed an experimental study to compare the friction forces generated during the sliding of orthodontic archwires made from various alloys through conventional and self-ligating brackets. Results show the favorable influence of SLBs, compared to conventional systems using elastomeric or metal ligatures, on the level of friction, particularly when shape-memory Ni-Ti archwires are used. PMID:26370596

  18. Experimental study of crossing angle collision

    SciTech Connect

    Chen, T.; Rice, D.; Rubin, D.; Sagan, D.; Tigner, M.

    1993-05-01

    The non-linear coupling due to the beam-beam interaction with crossing angle has been studied. The major effect of a small ({approximately}12mrad) crossing angle is to excite 5Q{sub x}{plus_minus}Q{sub s}=integer coupling resonance family on large amplitude particles, which results in bad lifetime. On the CESR, a small crossing angle ({approximately}2.4mr) was created at the IP and a reasonable beam-beam tune-shift was achieved. The decay rate of the beam is measured as a function of horizontal tune with and without crossing angle. The theoretical analysis, simulation and experimental measurements have a good agreement. The resonance strength as a function of crossing angle is also measured.

  19. Experimental Studies in Helicopter Vertical Climb Performance

    NASA Technical Reports Server (NTRS)

    McKillip, Robert M., Jr.

    1996-01-01

    Data and analysis from an experimental program to measure vertical climb performance on an eight-foot model rotor are presented. The rotor testing was performed using a unique moving-model facility capable of accurately simulating the flow conditions during axial flight, and was conducted from July 9, 1992 to July 16, 1992 at the Dynamic Model Track, or 'Long Track,' just prior to its demolition in August of 1992. Data collected during this brief test program included force and moment time histories from a sting-mounted strain gauge balance, support carriage velocity, and rotor rpm pulses. In addition, limited video footage (of marginal use) was recorded from smoke flow studies for both simulated vertical climb and descent trajectories. Analytical comparisons with these data include a series of progressively more detailed calculations ranging from simple momentum theory, a prescribed wake method, and a free-wake prediction.

  20. Experimental study of solar simulator mirror cryocontamination

    NASA Technical Reports Server (NTRS)

    Galjaev, V. L.; Makarov, A. A.; Afanassiev, N. A.

    1994-01-01

    The background and tasks formulation of the study of Solar Simulator collimation mirror cryocontamination in Large Thermal Vacuum Facility are outlined, research methods and experiment procedures are described, experimental relationships obtained are analyzed and practical recommendations are given. The accepted procedure of thermal vacuum tests as a rule defines the sequence of operations for verifying the spacecraft under test without taking into account measures for preventing Solar Simulator collimation mirror contamination and degradation. On the other hand, evacuation procedures is defined for conditions of achieving the required vacuum in the shortest possible time with using the available evacuation equipment at a regime close to the optimum one. Similarly, cryopanel cooling down cyclogram and test object preparation process are not analyzed from the viewpoint of ways of reducing environmental detrimental effects on thermal vacuum facility contamination-sensitive systems. Solar Simulator mirror contamination and its reflective characteristics change results in degradation of solar flux parameters and reduction of simulator continuous operation time. Methods of consideration of optical effects due to mirror surface contamination are actually missing. The effects themselves are not quite understood and data cited in literature as a rule, were obtained under conditions different from real thermal vacuum facility and therefore should be subjected to additional experimental verification. Only in the last few years contamination effect on optical surfaces degradation has been considered with using empirical relations. Mirror reflective properties degradation leads to the increase of Solar Simulator errors. This ultimately has an adverse effect on S/C ground development, schedule and cost of thermal vacuum tests. Besides, the mirror maintenance in operable state becomes more expensive. The present paper is dedicated to the study of Solar Simulator collimation

  1. Theoretical and experimental examination of near-field acoustic levitation.

    PubMed

    Nomura, Hideyuki; Kamakura, Tomoo; Matsuda, Kazuhisa

    2002-04-01

    A planar object can be levitated stably close to a piston sound source by making use of acoustic radiation pressure. This phenomenon is called near-field acoustic levitation [Y. Hashimoto et al., J. Acoust. Soc. Am. 100, 2057-2061 (1996)]. In the present article, the levitation distance is predicted theoretically by numerically solving basic equations in a compressible viscous fluid subject to the appropriate initial and boundary conditions. Additionally, experiments are carried out using a 19.5-kHz piston source with a 40-mm aperture and various aluminum disks of different sizes. The measured levitation distance agrees well with the theory, which is different from a conventional theory, and the levitation distance is not inversely proportional to the square root of the surface density of the levitated disk in a strict sense. PMID:12002842

  2. Experimental Study of Alluvial Fan Formation

    NASA Astrophysics Data System (ADS)

    Delorme, P.; Devauchelle, O.; Barrier, L.; Métivier, F.

    2015-12-01

    At the outlet of mountain ranges, rivers flow onto flatter lowlands. The associated change of slope causes sediment deposition. As the river is free to move laterally, it builds conical sedimentary structures called alluvial fans. Their location at the interface between erosional and depositional areas makes them valuable sedimentary archives. To decipher these sedimentary records, we need to understand the dynamics of their growth. Most natural fans are built by braided streams. However, to avoid the complexity of braided rivers, we develop a small-scale experiment in which an alluvial fan is formed by a single channel. We use a mixture of water and glycerol to produce a laminar river. The fluid is mixed with corindon sand (~ 300 μm) in a tilted channel and left free to form a fan around its outlet. The sediment and water discharges are constant during an experimental run. We record the fan progradation and the channel morphology with top-view pictures. We also generate an elevation map with an optical method based on the deformation of a moiré pattern. We observe that, to leading order, the fan remains self-affine as it grows, with a constant slope. We compare two recent studies about the formation of one-dimensionnal fan [Guerit et al. 2014] and threshold rivers [Seizilles et al. 2013] to our experimental findings. In particular, we propose a theory witch relates the fan morphology to the control parameters ( fluid and sediment discharges, grain size). Our observation accord with the predictions, suggesting that the fan is built near the threshold of sediment motion. Finally, we intend to expand our interpretation to alluvial fans build by single-thread channels ( Okavango, Bostwana; Taquari and Paraguay, Brasil; Pastaza, Peru).

  3. Effects of Fipronil Insecticide Application on Sympetrum sp. Larvae and Adults in Experimental Rice Paddy Field

    NASA Astrophysics Data System (ADS)

    Jinguji, Hiroshi; Ueda, Tetsuyuki; Tsunoda, Manami; Aihara, Shoko; Saito, Mitsuo

    The effect of on sowing and before transplanting application of the phenyl pyrazole insecticide, fipronil, on the survivorship Sympetrum spp. was investigated in plots of an experimental rice paddy field. In addition, the effect of two pesticide applications on rice weevils was investigated. A total of nine paddy plots were used in this study: three were treated with fipronil at the before transplanting application , three at the on sowing application, and the three remaining plots were left untreated for use as controls. Fipronil concentrations in paddy water at the time of application in before transplanting and on sowing treatments reached 1.45 and 1.20 μg/L, respectively. A comparison of experimental and control plots revealed a marked absence of Sympetrum frequens larvae, exuviae and adults from fipronil-treated fields. Adult density of Sympetrum sp. and members of Lestidae in paddy fields before transplanting application were considerably lower than in control plots. Our results show that before transplanting application is more effective than on sowing application for treating rice weevils, but that on sowing application may still be harm against dragonflies.

  4. Experimental Investigation on Liquid Metal Flow Distribution in Insulating Manifold under Uniform Magnetic Field

    NASA Astrophysics Data System (ADS)

    Miura, Masato; Ueki, Yoshitaka; Yokomine, Takehiko; Kunugi, Tomoaki

    2012-11-01

    Magnetohydrodynamics (MHD) problem which is caused by interaction between electrical conducting fluid flow and the magnetic field is one of the biggest problem in the liquid metal blanket of the fusion reactor. In the liquid metal blanket concept, it is necessary to distribute liquid metal flows uniformly in the manifold because imbalance of flow rates should affect the heat transfer performance directly, which leads to safety problem. While the manifold is insulated electrically as well as the flow duct, the 3D-MHD effect on the flowing liquid metal in the manifold is more apparent than that in straight duct. With reference to the flow distribution in this concept, the liquid metal flow in the electrical insulating manifold under the uniform transverse magnetic field is investigated experimentally. In this study, GaInSn is selected as working fluid. The experimental system includes the electrical magnet and the manifold test section which is made of acrylic resin for perfectly electrical insulation. The liquid metal flows in a non-symmetric 180°-turn with manifold, which consists of one upward channel and two downward channels. The flow rates in each channel are measured by electromagnetic flow meters for several combinations Reynolds number and Hartman number. The effects of magnetic field on the uniformity of flow distribution are cleared.

  5. Experimental study of ocean-atmosphere exchanges

    SciTech Connect

    Eymard, L.; Weill, A.; Planton, S.

    1994-12-31

    The SOFIA/ASTEX and SEMAPHORE campaigns were performed over open ocean, near the Azores, to study the ocean-atmosphere exchanges at the local and meso-scales, with a particular insight to the spatial variability of fluxes and related processes. In both cases, the experimental strategy involved two research aircraft and an oceanographic vessel, as well as surface buoys. SOFIA/ASTEX was more particularly devoted to the study of boundary layer and cloud properties, including microphysical and radiative aspects, in the framework of the international campaign ASTEX. SEMAPHORE was aimed at the analysis of surface fluxes and interactions with the upper ocean at the mesoscale. It included an important network of ocean circulation and thermal properties, from ships, current meter moorings, current drifters, and drifting buoys. The thermal front associated with the Azores current is an important feature of the ocean circulation and was particularly investigated. The analysis of data from meteorological satellites is also an important aspect of the two campaigns.

  6. Theoretical and Experimental Studies of Radiative Shocks

    NASA Astrophysics Data System (ADS)

    Michaut, C.; Vinci, T.; Boireau, L.; Koenig, M.; Bouquet, S.; Benuzzi-Mounaix, A.; Osaki, N.; Herpe, G.; Falize, E.; Loupias, B.; Atzeni, S.

    2007-01-01

    This paper deals with the radiative shock from both theoretical and numerical points of view. It is based on the whole experimental results obtained at Laboratoire d'Utilisation des Lasers Intenses (LULI, École Polytechnique). Radiative shocks are high-Mach number shocks with a strong coupling between radiation and hydrodynamics which leads to a structure governed by a radiative precursor. These shocks are involved in various astrophysical systems: stellar accretion shocks, pulsating stars, interaction between supernovae and the interstellar medium. In laboratory, these radiative shocks are generated using high power lasers. New diagnostics have been implemented to study the geometrical shape of the shock and the front shock density. Data were obtained varying initial conditions for different laser intensities and temperature. The modeling of these phenomena is mainly performed through numerical simulations (1D and 2D) and analytical studies. We exhibit results obtained from several radiative hydrodynamics codes. As a result, it is possible to discuss about the influence of the geometry and physical parameters introduced in the 1D and 2D models.

  7. Millimeter wave near-field study

    NASA Technical Reports Server (NTRS)

    Kefauver, Neill

    1990-01-01

    The possibility is evaluated of current technology measuring large aperture millimeter wave antennas. Included are a mathematical modeling of system errors, experimental data supporting error model, predictions of system accuracy at millimeter wavelengths, advantage of near-field measurements, and a cost estimate for a facility upgrade. The use is emphasized of software compensation and other inexpensive alternatives to develop a near optimum solution to near-field measurement problems at millimeter wavelengths.

  8. Experimental concept for examination of biological effects of magnetic field concealed by gravity.

    PubMed

    Yamashita, M; Tomita-Yokotani, K; Hashimoto, H; Takai, M; Tsushima, M; Nakamura, T

    2004-01-01

    Space is not only a place to study biological effects of gravity, but also provides unique opportunities to examine other environmental factors, where the biological actions are masked by gravity on the ground. Even the earth's magnetic field is steadily acting on living systems, and is known to influence many biological processes. A systematic survey and assessment of its action are difficult to conduct in the presence of dominant factors, such as gravity. Investigation of responses of biological systems against the combined environment of zero-gravity and zero-magnetic field might establish the baseline for the analysis of biological effects of magnetic factors. We propose, in this paper, an experimental concept in this context, together with a practical approach of the experiments, both in orbit and on the ground, with a thin magnetic shielding film. Plant epicotyl growth was taken as an exemplar index to evaluate technical and scientific feasibility of the proposed system concept. PMID:15880894

  9. Design of organic scintillators for non-standard radiation field dosimetry: experimental setup.

    PubMed

    Norman H, Machado R; Maximiliano, Trujillo T; Javier E, García G; Diana C, Narvaez G; Paula A, Marín M; Róbinson A, Torres V

    2013-01-01

    This paper describes an experimental setup designed for sensing the luminescent light coming from an organic plastic scintillator stimulated with ionizing radiation. This device is intended to be a part of a complete dosimeter system for characterization of small radiation fields which is the project of the doctoral thesis of the medical physicist at the Radiation Oncology facility of Hospital San Vicente Fundación in conjunction with the Universidad de Antioquia of Medellín Colombia. Some preliminary results predict a good performance of the unit, but further studies must be conducted in order to have a completed evaluation of the system. This is the first step in the development of an accuracy tool for measurement of non-standard fields in the Radiotherapy or Radiosurgery processes. PMID:24110369

  10. A numerical and experimental study of confined swirling jets

    NASA Technical Reports Server (NTRS)

    Nikjooy, M.; Mongia, H. C.; Samuelsen, G. S.; Mcdonell, V. G.

    1989-01-01

    A numerical and experimental study of a confined strong swirling flow is presented. Detailed velocity measurements are made using a two-component laser Doppler velocimeter (LDV) technique. Computations are performed using a differential second-moment (DSM) closure. The effect of inlet dissipation rate on calculated mean and turbulence fields is investigated. Various model constants are employed in the pressure-strain model to demonstrate their influences on the predicted results. Finally, comparison of the DSM calculations with the algebraic second-monent (ASM) closure results shows that the DSM is better suited for complex swirling flow analysis.