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1
Yoo, Inhwa, and Hyung-Min Yoon. "The Effect of Two Exercise Types in the 8 Week Exercise Training on the Physical Fitness of Elderly Women." Asian Journal of Kinesiology 22, no. 1 (January 31, 2020): 15–23. http://dx.doi.org/10.15758/ajk.2020.22.1.15.
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OBJECTIVES The purpose of this study was to investigate the effect of two exercise types (Gyrokinesis exercise and Elastic band exercise) in the 8 week exercise training on the physical fitness of elderly women.METHODS The subjects of this study were 57 elderly women between 65 and 80 years old, who had no abnormality in the Physical Readiness Questionnaire (PAR-Q test) and were able to do physical activity on the orthopedic standpoints. The subjects were divided into three groups: Gyrokinesis Exercise Group (GKEG: n=19), Elastic Band Exercise Group (EBEG: n=20), and Control Group (CG: n=18). The subjects performed a Gyrokinesis Exercise in GKEG and an Elastic Band Exercise in EBEG for 50 minutes a day (10 minutes for warm-up, 30 minutes for main exercise, 10 minutes for cool-down), and 3 times a week for a total of 8 weeks. The subjects of CG did not participate in any particular exercise program but only everyday life. The dependent variables were Physical Fitness: Upper Muscular Endurance, 30-Second Arm Curl. Lower Flexibility, Dynamic Balance, Endurance. one-way ANOVA with repeated measurements was used to test the hypothesis in this study. A post hoc was conducted only when there was an interaction effect between groups and measurements. The difference of the post-test between groups were analyzed through Scheffe method after one-way ANOVA. The statistical significance level of this study was α=.05.RESULTS Gyrokinesis and Elastic Band Exercises were both effective on the physical fitness of elderly women: Upper Muscular Endurance, 30-Second Arm Curl, Lower Flexibility, Dynamic Balance, and Endurance. However, there were no differences in exercise effects after 8 week exercise training between the Gyrokinesis Exercise Group and the Elastic Band Exercise Group.CONCLUSIONS It is concluded that Gyrokinesis and Elastic Band exercise programs should be encouraged to improve physical fitness of elderly women and we need a follow-up study with longer term exercise training programs to find the differences in exercise effects between Gyrokinesis Exercise and Elastic Band Exercise.
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Nouri, Reza, Klaus Michaeil Braumann, Bahareh Mahmoudieh ChamPiri, Jan Schröder, and Mahdieh Akochakian. "Cancer Related Fatigue and Upper Limb Disabilities Cannot Improve after 6 Weeks Resistance Training with Thera-Band in Breast Cancer Survivors." International Journal of Applied Exercise Physiology 7, no. 2 (June 17, 2018): 76–84. http://dx.doi.org/10.22631/ijaep.v7i2.263.
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Aim. Breast cancer and its treatments lead to cancer related fatigue and upper limb disabilities. On the other hand, resistance training has positive benefits for breast cancer survivors. Thus, the aim of present study was to clarify the effect of resistance training with Thera – Band on CRF and upper limb disabilities in breast cancer survivors. Methods. Fifty women with breast cancer aged 29-65 were divided in to 2 groups: 1) resistance training with Thera- Band group (n=25) and 2) control group (n=25). Resistance training with Thera- Band group, after 5 minutes warm up, were performed the 9 resistance training with Thera – Band, from 8 to 12 repetitions and 2 sets in the first two weeks, 8 to 12 repetitions and 3 sets in the second two weeks and 8 to 12 repetitions and 4 sets in the third two weeks. The rest between each set was started from 90 seconds in the first week and was decreased to 45 seconds in the sixth week. Control group didn’t have any supervised or regular physical activity. Cancer related fatigue (CRF) and upper limb disabilities were surveyed by Piper Fatigue Scale and DASH questionnaire, respectively. Data were analyzed using by 2-way ANOVA (p≤0.05). Statistical Results. The findings of this study demonstrated that 6 weeks resistance training by Thera – Band has no significant effect on CRF and upper limb disabilities (p≥0.05). Conclusion. It can be concluded that exercise training with Thera- Band for 6 weeks cannot improve CRF and upper limb disabilities in breast cancer survivors. Future studies with large sample size and long period of intervention is suggested.
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Wu, Bing Hui, Bao Jun Pang, and Zong Quan Deng. "Modeling and Simulation of Flexible Band Based on the Muti-Body Dynamics." Key Engineering Materials 458 (December 2010): 200–205. http://dx.doi.org/10.4028/www.scientific.net/kem.458.200.
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To provide theory and technique support for the research on dynamic properties of flexible lock-unlock technology, dynamic equation of band is built up based on the muti-body dynamics. Simulation based on modal neutral file and mixed model with rigid and flexible properties are accomplished in the software of ADAMS. The result reveals that the later one is much closed to the actual movement.
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Chen, Funan, Huili Bi, Soo-Hwang Ahn, Zhongyu Mao, Yongyao Luo, and Zhengwei Wang. "Investigation on Dynamic Stresses of Pump-Turbine Runner during Start Up in Turbine Mode." Processes 9, no. 3 (March 10, 2021): 499. http://dx.doi.org/10.3390/pr9030499.
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The startup process occurs frequently for pumped storage units. During this process, the rotating rate that changes rapidly and unsteady flow in runner cause the complex dynamic response of runner, sometimes even resonance. The sharp rise of stress and the large-amplitude dynamic stresses of runner will greatly shorten the fatigue life. Thus, the study of start-up process in turbine mode is critical to the safety operation. This paper introduced a method of coupling one dimensional (1D) pipeline calculation and three-dimensional computational dynamics (3D CFD) simulation to analyze transient unsteady flow in units and to obtain more accurate and reliable dynamic stresses results during start up process. According to the results, stress of the ring near fixed support increased quickly as rotating rate rose and became larger than at fillets of leading edge and band in the later stages of start-up. In addition, it was found that dynamic response can be caused by rotor stator interaction (RSI), but also could even be generated by the severe pressure fluctuation in clearance, which can also be a leading factor of dynamic stresses. This study will facilitate further estimation of dynamic stresses in complex flow and changing rotating rate cases, as well as fatigue analysis of runner during transient operation.
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Chen, Hong Mei, Hua Shun Yu, Guang Hui Min, and Yun Xue Jin. "Study on the Microstructure and Texture of Warm Rolled ZK60 Magnesium Alloy Sheet." Advanced Materials Research 557-559 (July 2012): 1344–48. http://dx.doi.org/10.4028/www.scientific.net/amr.557-559.1344.
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The microstructure and macrotexture of ZK60 alloy sheet were investigated through OM and XRD, which were produced by twin roll casting and sequential warm rolling. Microstructure of twin roll cast ZK60 alloy changed from dendrite structure to fibrous structure with elongated grains and high density shear bands along the rolling direction after warm rolling process at different rolling parameters. The density of shear bands increased with the decreasing of the rolling temperature, or the increasing of per pass rolling reduction. Dynamic recrystallization could be found during the warm rolling process at and above 350oC, and many fine grains could be found in the shear band area. The warm rolled ZK60 alloy sheet exhibited strong (0001) basal pole texture. The formation of the shear bands tends to cause the basal pole tilt slightly to the transverse direction after warm rolling. The intensity of (0001) pole figure increased with the decreasing of rolling temperature, or the increasing of per pass rolling reduction.
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Sasaki, Hideharu, Bunmei Taguchi, Nobumasa Komori, and Yukio Masumoto. "Influence of Local Dynamical Air–Sea Feedback Process on the Hawaiian Lee Countercurrent." Journal of Climate 26, no. 18 (September 9, 2013): 7267–79. http://dx.doi.org/10.1175/jcli-d-12-00586.1.
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Abstract Local air–sea interactions over the high sea surface temperature (SST) band along the Hawaiian Lee Countercurrent (HLCC) are examined with a focus on dynamical feedback of SST-induced wind stress to the ocean using the atmosphere–ocean coupled general circulation model (CGCM). A pair of ensemble CGCM simulations are compared to extract the air–sea interactions associated with HLCC: the control simulations and other simulations, the latter purposely eliminating influences of the high SST band on the sea surface flux computations in the CGCM. The comparison reveals that oceanic response to surface wind convergence and positive wind stress curl induced by the high SST band increases (decreases) the HLCC speed in the southern (northern) flank of the HLCC. The HLCC speed changes are driven by the Ekman suction associated with positive wind stress curl over the warm HLCC via the thermal wind balance. The HLCC speed increase is more significant than its decrease. This dynamical feedback is likely to be important to sustain the extension of the HLCC far to the west. The heat budget analysis confirms that advection of warm water from the west associated with this significant current speed increase plays a role in the southward shift of the HLCC axis. The dynamical feedback with the HLCC speed increase can potentially amplify the seasonal and interannual variations of HLCC.
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Battaglia, Alessandro, Pavlos Kollias, Ranvir Dhillon, Katia Lamer, Marat Khairoutdinov, and Daniel Watters. "Mind the gap – Part 2: Improving quantitative estimates of cloud and rain water path in oceanic warm rain using spaceborne radars." Atmospheric Measurement Techniques 13, no. 9 (September 15, 2020): 4865–83. http://dx.doi.org/10.5194/amt-13-4865-2020.
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Abstract. The intrinsic small spatial scales and low-reflectivity structure of oceanic warm precipitating clouds suggest that millimeter spaceborne radars are best suited to providing quantitative estimates of cloud and rain liquid water paths (LWPs). This assertion is based on their smaller horizontal footprint; high sensitivities; and a wide dynamic range of path-integrated attenuations associated with warm-rain cells across the millimeter wavelength spectrum, with diverse spectral responses to rain and cloud partitioning. State-of-the-art single-frequency radar profiling algorithms of warm rain seem to be inadequate because of their dependence on uncertain assumptions about the rain–cloud partitioning and because of the rain microphysics. Here, high-resolution cloud-resolving model simulations for the Rain in Cumulus over the Ocean field study and a spaceborne forward radar simulator are exploited to assess the potential of existing and future spaceborne radar systems for quantitative warm-rain microphysical retrievals. Specifically, the detrimental effects of nonuniform beam filling on estimates of path-integrated attenuation (PIA), the added value of brightness temperature (TB) derived adopting radiometric radar modes, and the performances of multifrequency PIA and/or TB combinations when retrieving liquid water paths partitioned into cloud (c-LWPs) and rain (r-LWPs) are assessed. Results show that (1) Ka- and W-band TB values add useful constraints and are effective at lower LWPs than the same-frequency PIAs; (2) matched-beam combined TB values and PIAs from single-frequency or multifrequency radars can significantly narrow down uncertainties in retrieved cloud and rain liquid water paths; and (3) the configuration including PIAs, TB values and near-surface reflectivities for the Ka-band–W-band pairs in our synthetic retrieval can achieve an RMSE of better than 30 % for c-LWPs and r-LWPs exceeding 100 g m−2.
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Fujii, Y., W. E. Tobler, E. M. Clausing, T. W. Megli, and M. Haghgooie. "Application of dynamic band brake model for enhanced drivetrain simulation." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 216, no. 11 (November 1, 2002): 873–81. http://dx.doi.org/10.1243/095440702321031423.
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In a modern vehicle design process, analytical tools are widely employed to complement experimental approaches for design evaluation. When effectively utilized, they lead to a reduced development time with improved vehicle performance. The development process of an automatic transmission (AT) system can benefit from an analytical representation which accurately captures AT shifting behaviours. In a typical AT system, friction components such as wet clutches and band brakes are utilized to alter planetary gear configurations for automatic shifting. Thus, an accurate representation of friction component dynamics is critical in predicting AT shifting behaviour. Engagement characteristics of friction components vary widely under different operating conditions. Although the basic engagement physics was identified in the 1970s, it is relatively recently that a predictive, yet computationally efficient model became available. This paper describes the first attempt to utilize a dynamic friction component model in drivetrain simulations. Specifically, a dynamic band brake model is implemented to predict the up-shift behaviour of a four-speed AT system under various operating conditions. Simulation results are qualitatively validated with experimental data obtained from a dynamometer test stand. The dynamic band brake model enhances the shift predictability of a drivetrain model and potentially allows analytical evaluation of shift quality and control strategy.
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Vazza, F., S. Ettori, M. Roncarelli, M. Angelinelli, M. Brüggen, and C. Gheller. "Detecting shocked intergalactic gas with X-ray and radio observations." Astronomy & Astrophysics 627 (June 25, 2019): A5. http://dx.doi.org/10.1051/0004-6361/201935439.
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Detecting the thermal and non-thermal emission from the shocked cosmic gas surrounding large-scale structures represents a challenge for observations, as well as a unique window into the physics of the warm-hot intergalactic medium. In this work, we present synthetic radio and X-ray surveys of large cosmological simulations in order to assess the chances of jointly detecting the cosmic web in both frequency ranges. We then propose best observing strategies tailored for existing (LOFAR, MWA, and XMM) or future instruments (SKA-LOW and SKA-MID, Athena, and eROSITA). We find that the most promising targets are the extreme peripheries of galaxy clusters in an early merging stage, where the merger causes the fast compression of warm-hot gas onto the virial region. By taking advantage of a detection in the radio band, future deep X-ray observations will probe this gas in emission, and help us to study plasma conditions in the dynamic warm-hot intergalactic medium with unprecedented detail.
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Wojtowicz, Sebastian, Anna Daniluk, Karolina Wiaderna, Aneta Bugalska, Anna Hadamus, Marta Grabowicz, and Darius Bialoszewski. "ASSESSMENT OF IMPACT OF ACTIVATION OF HIP JOINT ABDUCTORS AND EXTERNAL ROTATORS ON GAIT AND RUNNNING PARAMETERS IN HEALTHY PEOPLE - PILOT STUDY." Acta kinesiologica, N1 2021 (2021): 120–26. http://dx.doi.org/10.51371/issn.1840-2976.2021.15.1.14.
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Many physiotherapists and motor preparation coaches recommend including resistance exercises for the hip joint abductors and external rotators in a warm-up. Muscle activation with resistance band exercises is believed to improve positional control of the pelvis and the lower limbs, thus reducing the risk of musculoskeletal injury during rehabilitation or training proper. The aim of this study was to assess the impact of a single session of activation of hip joint abductors and external rotators on gait and running parameters in healthy people. The study involved 54 healthy individuals aged 19-21 years. An experimental group (Group 1) performed a set of 6 resistance exercises with Thera rubber bands, intended to activate the hip joint abductors and external rotators. A control group (Group 2) performed the same set of exercises but without external resistance. A walking and running gait examination was performed on a Zebris FDM treadmill in both groups before and after the exercises. Both variants of exercises produced changes in selected gait parameters (p<0.05). An examination of running gait in Group 1 revealed an increase in step length in the dominant limb (p<0.05) and stride length (p<0.05) and step time in the dominant limb (p<0.05), stride length (p<0.05) and cadence (p<0.05). Heel pressure also decreased in both limbs, and heel pressure force decreased in the non-dominant limb (p<0.05). A running gait examination in Group 2 revealed increased midfoot pressure force in both limbs (p<0.05). Thus, a single session of exercises with resistance banding to activate the hip joint abductors and external rotators exerted an effect on running parameters, which may improve running economy.
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Kingsmill, David E., Paul J. Neiman, F. Martin Ralph, and Allen B. White. "Synoptic and Topographic Variability of Northern California Precipitation Characteristics in Landfalling Winter Storms Observed during CALJET." Monthly Weather Review 134, no. 8 (August 1, 2006): 2072–94. http://dx.doi.org/10.1175/mwr3166.1.
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Abstract Observations from northern California during the California Landfalling Jets (CALJET) experiment are used to examine the mean characteristics of precipitation and their variances as functions of synoptic and topographic regimes. Ten cases involving the landfall of extratropical cyclones are analyzed with radar and rain gauge data collected at two sites: one in the coastal mountains north of San Francisco (CZD) and the other in the Central Valley just west of Sacramento (KDAX). Aside from the melting-layer bright band, the most striking feature in the 10-case composite vertical profile of radar reflectivity at CZD was a distinct change in slope about 2.5 km above the bright band. This “shoulder” is thought to represent a change in the growth rate of hydrometeors. Although the bright band was quite distinct, about one-third of the profiles in the composite did not exhibit this feature. These nonbrightband (NBB) profiles had a low-level slope where reflectivity increased with decreasing altitude, a structure suggesting that collision–coalescence was the primary growth process. The relationship between surface rainfall rate and low-level radar reflectivity implies that all profiles were composed of larger numbers of small drops than expected from a Marshall–Palmer drop size distribution, a trend that was especially apparent for NBB profiles. Synoptic variability of precipitation characteristics at CZD were examined by identifying five distinct regimes (cold sector, warm front, warm sector, cold front, and cool sector) based on a simplified conceptual model. The shoulder remained approximately 2.5 km above the bright band in each regime. Rainfall intensity was highest during the cold-frontal regime and NBB rainfall was most common during the warm-frontal, warm-sector, and cool-sector regimes. Topographic variability of precipitation characteristics was investigated by comparing results at CZD and KDAX. A shoulder structure located about 2.5 km above the bright band was also evident in the KDAX profiles, suggesting that this feature is related to large-scale dynamic, thermodynamic, and microphysical processes rather than orographic effects. The relationship between surface rainfall rate and low-level radar reflectivity near KDAX closely followed a trend expected for a Marshall–Palmer drop size distribution, implying the presence of relatively larger raindrops than observed at CZD and indicating that NBB rainfall occurs less frequently near KDAX.
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McPhee, M. G. "Analysis and Prediction of Short-Term Ice Drift." Journal of Offshore Mechanics and Arctic Engineering 110, no. 1 (February 1, 1988): 94–100. http://dx.doi.org/10.1115/1.3257130.
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Techniques for kinematic analysis and dynamic, “free-drift” ice modeling are described and applied to interpretation of ice-drift data from recent marginal ice zone (MIZ) experiments. Kinematic description is based on a complex demodulation algorithm that separates inertial and tidal components from lower frequency, “synoptic” drift. Complex demodulation produces the time series of phasors (complex numbers describing phase and amplitude of the oscillating components), useful for separating the physical processes active in the upper ocean/ice system. Free-drift ice motion modeling utilizes a similarity theory for planetary-boundary-layer dynamics that includes the effect of buoyancy, both from rapid melting at the ice/ocean interface, and/or from a pre-existing density gradient (pycnocline) within the boundary layer. Two examples are considered: one in which a band of ice in the Bering Sea drifted rapidly away from the rest of the pack when it encountered warm water at the ice edge; and a second in which drift in the Greenland Sea was apparently affected by both a shallow pycnocline and a period of rapid melt.
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Diba, Ibrahima, Moctar Camara, and Arona Diedhiou. "Investigating West African Monsoon Features in Warm Years Using the Regional Climate Model RegCM4." Atmosphere 10, no. 1 (January 10, 2019): 23. http://dx.doi.org/10.3390/atmos10010023.
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This study investigates the changes in West African monsoon features during warm years using the Regional Climate Model version 4.5 (RegCM4.5). The analysis uses 30 years of datasets of rainfall, surface temperature and wind parameters (from 1980 to 2009). We performed a simulation at a spatial resolution of 50 km with the RegCM4.5 model driven by ERA-Interim reanalysis. The rainfall amount is weaker over the Sahel (western and central) and the Guinea region for the warmest years compared to the coldest ones. The analysis of heat fluxes show that the sensible (latent) heat flux is stronger (weaker) during the warmest (coldest) years. When considering the rainfall events, there is a decrease of the number of rainy days over the Guinea Coast (in the South of Cote d’Ivoire, of Ghana and of Benin) and the western and eastern Sahel during warm years. The maximum length of consecutive wet days decreases over the western and eastern Sahel, while the consecutive dry days increase mainly over the Sahel band during the warm years. The percentage of very warm days and warm nights increase mainly over the Sahel domain and the Guinea region. The model also simulates an increase of the warm spell duration index in the whole Sahel domain and over the Guinea Coast in warm years. The analysis of the wind dynamic exhibits during warm years a weakening of the monsoon flow in the lower levels, a strengthening in the magnitude of the African Easterly Jet (AEJ) in the mid-troposphere and a slight increase of the Tropical Easterly Jet (TEJ) in the upper levels of the atmosphere during warm years.
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Teshiba, M., H. Hashiguchi, S. Fukao, and Y. Shibagaki. "Typhoon 9707 observations with the MU radar and L-band boundary layer radar." Annales Geophysicae 19, no. 8 (August 31, 2001): 925–31. http://dx.doi.org/10.5194/angeo-19-925-2001.
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Abstract. Typhoon 9707 (Opal) was observed with the VHF-band Middle and Upper atmosphere (MU) radar, an L-band boundary layer radar (BLR), and a vertical-pointing C-band meteorological radar at the Shigaraki MU Observatory in Shiga prefecture, Japan on 20 June 1997. The typhoon center passed about 80 km southeast from the radar site. Mesoscale precipitating clouds developed due to warm-moist airmass transport from the typhoon, and passed over the MU radar site with easterly or southeasterly winds. We primarily present the wind behaviour including the vertical component which a conventional meteorological Doppler radar cannot directly observe, and discuss the relationship between the wind behaviour of the typhoon and the precipitating system. To investigate the dynamic structure of the typhoon, the observed wind was divided into radial and tangential wind components under the assumption that the typhoon had an axi-symmetric structure. Altitude range of outflow ascended from 1–3 km to 2–10 km with increasing distance (within 80–260 km range) from the typhoon center, and in-flow was observed above and below the outflow. Outflow and inflow were associated with updraft and downdraft, respectively. In the tangential wind, the maximum speed of counterclockwise winds was confirmed at 1–2 km altitudes. Based on the vertical velocity and the reflectivity obtained with the MU radar and the C-band meteorological radar, respectively, precipitating clouds, accompanied by the wind behaviour of the typhoon, were classified into stratiform and convective precipitating clouds. In the stratiform precipitating clouds, a vertical shear of radial wind and the maximum speed of counterclockwise wind were observed. There was a strong reflectivity layer called a ‘bright band’ around the 4.2 km altitude. We confirmed strong updrafts and down-drafts below and above it, respectively, and the existence of a relatively dry layer around the bright band level from radiosonde soundings. In the convective precipitating clouds, the regions of strong and weak reflectivities were well associated with those of updraft and downdraft, respectively.Key words. Meteorology and atmospheric dynamics (mesoscale meteorology; precipitation) Radio science (remote sensing)
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Hsu, Hsiao-ming, Mitchell W. Moncrieff, Wen-wen Tung, and Changhai Liu. "Multiscale Temporal Variability of Warm-Season Precipitation over North America: Statistical Analysis of Radar Measurements." Journal of the Atmospheric Sciences 63, no. 9 (September 1, 2006): 2355–68. http://dx.doi.org/10.1175/jas3752.1.
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Abstract Directionally averaged time series of precipitation rates for eight warm seasons (1996–2003) over the continental United States derived from Next Generation Weather Radar (NEXRAD) measurements are analyzed using spectral decomposition methods. For the latitudinally averaged data, in addition to previously identified diurnal and semidiurnal cycles, the temporal spectra show cross-scale self-similarity and periodicity. This property is revealed by a power-law scaling with an exponent of −4/3 for the frequency band higher than semidiurnal and −3/4 for the 1–3-day band. For the longitudinally averaged series the scaling exponent for the frequency band higher than semidiurnal changes from −4/3 to −5/3 revealing anisotropic properties. The dominant periods and propagation speeds display temporal variability on about 1/2, 1, 4, 11, and 25 days. Composite patterns describing periods of <5 days display the eastward propagation characteristic of classical mesoscale convective organization. The lower-frequency (>5 days) patterns propagate westward suggesting the influence of large-scale waves, and both dominant periods and propagation speeds show marked interannual variability. The implied dependence between propagation and mean-flow for <5 days is consistent with the macrophysics of warm-season convective organization, and extends known dynamical mechanisms to a statistical framework.
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Vliegenthart, Gerard A., Arvind Ravichandran, Marisol Ripoll, Thorsten Auth, and Gerhard Gompper. "Filamentous active matter: Band formation, bending, buckling, and defects." Science Advances 6, no. 30 (July 2020): eaaw9975. http://dx.doi.org/10.1126/sciadv.aaw9975.
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Motor proteins drive persistent motion and self-organization of cytoskeletal filaments. However, state-of-the-art microscopy techniques and continuum modeling approaches focus on large length and time scales. Here, we perform component-based computer simulations of polar filaments and molecular motors linking microscopic interactions and activity to self-organization and dynamics from the filament level up to the mesoscopic domain level. Dynamic filament cross-linking and sliding and excluded-volume interactions promote formation of bundles at small densities and of active polar nematics at high densities. A buckling-type instability sets the size of polar domains and the density of topological defects. We predict a universal scaling of the active diffusion coefficient and the domain size with activity, and its dependence on parameters like motor concentration and filament persistence length. Our results provide a microscopic understanding of cytoplasmic streaming in cells and help to develop design strategies for novel engineered active materials.
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Tikhomirov, S. A. "Ultrafast dynamics and mechanisms of non-stationary absorption in thin gallium selenide samples." Proceedings of the National Academy of Sciences of Belarus. Physics and Mathematics Series 57, no. 1 (April 2, 2021): 99–107. http://dx.doi.org/10.29235/1561-2430-2021-57-1-99-107.
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Herein, the dynamics and mechanisms of induced absorption in thin samples of gallium selenide under various excitation conditions are studied using femtosecond kinetic spectroscopy. We have registered several types of induced changes including induced absorption on free charge carriers (“hot” and thermalized electrons), bleaching and absorption due to the population of near-edge trap or exciton states, as well as rapid changes in the absorption of probing radiation in the region of the overlap of the exciting and probing pulses due to two-quantum two-frequency interband transitions. The time ranges of the relaxation processes are estimated. It is shown that when using relatively low-intensity long-wave excitation (790 nm), the resonant excitation of the near-edge states occurs mainly due to two-quantum two-frequency transitions followed by the formation of the dynamic equilibrium between bound and free electrons in the time range up to 5 ps. When electrons are excited deeply into the conduction band with the formation of hot free electrons and their subsequent thermalization to the bottom of the conduction band in the time range up to 1 ps, the population of the near-edge states and the establishment of the dynamic equilibrium between bound and free electrons is realized in the same time range (5 ps) as when they are excited “from below”.
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Cveticanin, L., and I. Kovacic. "On the Dynamics of Bodies With Continual Mass Variation." Journal of Applied Mechanics 74, no. 4 (September 29, 2006): 810–15. http://dx.doi.org/10.1115/1.2711231.
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In this paper the differential equations of the general motion of the rigid body with continual mass variation are considered. The impact force and the impact torque that occur due to addition or separation of the body with velocity and angular velocity which differs from the velocity of mass center and angular velocity of the existing body are introduced. The theoretical consideration is applied for solving a real technical problem when the band winds up on the drum. The plane motion of the drum on which the band winds up is considered. The influence of the velocity of the band on the angular velocity of the drum and the motion of the drum mass center is obtained.
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Eklund, Henrik, Sven Wedemeyer, Mikolaj Szydlarski, Shahin Jafarzadeh, and Juan Camilo Guevara Gómez. "The Sun at millimeter wavelengths." Astronomy & Astrophysics 644 (December 2020): A152. http://dx.doi.org/10.1051/0004-6361/202038250.
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Context. Solar observations with the Atacama Large Millimeter/sub-millimeter Array (ALMA) facilitate studies of the atmosphere of the Sun at chromospheric heights at high spatial and temporal resolution at millimeter wavelengths. Aims. ALMA intensity data at millimeter(mm)-wavelengths are used for a first detailed systematic assessment of the occurrence and properties of small-scale dynamical features in the quiet Sun. Methods. We analyzed ALMA Band 3 data (∼3 mm/100 GHz) with a spatial resolution of ∼1.4–2.1 arcsec and a duration of ∼40 min together with SDO/HMI magnetograms. The temporal evolution of the mm maps is studied to detect pronounced dynamical features, which then are connected to dynamical events via a k-means clustering algorithm. We studied the physical properties of the resulting events and explored whether or not they show properties consistent with propagating shock waves. For this purpose, we calculated observable shock wave signatures at mm wavelengths from one- and three-dimensional model atmospheres. Results. We detect 552 dynamical events with an excess in brightness temperature (ΔTb) of at least ≥400 K. The events show a large variety in size up to ∼9″, amplitude ΔTb up to ∼1200 K with typical values in the range ∼450–750 K, and lifetime at full width at half maximum of ΔTb of between ∼43 and 360 s, with typical values between ∼55 and 125 s. Furthermore, many of the events show signature properties suggesting that they are likely produced by propagating shock waves. Conclusions. There are a lot of small-scale dynamic structures detected in the Band 3 data, even though the spatial resolution sets limitations on the size of events that can be detected. The number of dynamic signatures in the ALMA mm data is very low in areas with photospheric footpoints with stronger magnetic fields, which is consistent with the expectation for propagating shock waves.
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Kepert, Jeffrey D. "The Boundary Layer Dynamics of Tropical Cyclone Rainbands." Journal of the Atmospheric Sciences 75, no. 11 (September 28, 2018): 3777–95. http://dx.doi.org/10.1175/jas-d-18-0133.1.
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Abstract Spiral bands are ubiquitous features in tropical cyclones and significantly affect boundary layer thermodynamics, yet knowledge of their boundary layer dynamics is lacking. Prompted by recent work that has shown that relatively weak axisymmetric vorticity perturbations outside of the radius of maximum winds in tropical cyclones can produce remarkably strong frictional convergence, and by the observation that most secondary eyewalls appear to form by the “wrapping up” of a spiral rainband, the effect of asymmetric vorticity features that mimic spiral bands is studied. The mass field corresponding to an axisymmetric vortex with added spiral vorticity band is constructed using the nonlinear balance equation, and supplied to a three-dimensional boundary layer model. The resulting flow has strong low-level convergence and a marked updraft extending along the vorticity band and some distance downwind. There is a marked along-band wind maximum in the upper boundary layer, similar to observations, which is up to about 20% stronger than the balanced flow. A marked gradient in the inflow-layer depth exists across the band and there is an increase in the surface wind factor (the ratio of surface wind speed to nonlinear-balanced wind speed) near the band. The boundary layer dynamics near a rainband therefore form a continuum with the flow near a secondary eyewall. None of these features are due to convective momentum transports, which are absent from the model. The sensitivities of the flow to band length, width, location, crossing angle, and amplitude are examined, and the possible contribution of boundary layer dynamics to the formation of the tropical cyclone rainbands discussed.
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Vannière, Benoît, Arnaud Czaja, Helen Dacre, and Tim Woollings. "A “Cold Path” for the Gulf Stream–Troposphere Connection." Journal of Climate 30, no. 4 (February 2, 2017): 1363–79. http://dx.doi.org/10.1175/jcli-d-15-0749.1.
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Abstract The mechanism by which the Gulf Stream sea surface temperature (SST) front anchors a band of precipitation on its warm edge is still a matter of debate, and little is known about how synoptic activity contributes to the mean state. In the present study, the influence of the SST front on precipitation is investigated during the course of a single extratropical cyclone using a regional configuration of the Met Office Unified Model. The comparison of a control run with a simulation in which SST gradients were smoothed brought the following conclusions: a band of precipitation is reproduced for a single extratropical cyclone, and the response to the SST gradient is dominated by a change of convective precipitation in the cold sector of the storm. Several climatological features described by previous studies, such as surface wind convergence on the warm edge or a meridional circulation cell across the SST front, are also reproduced at synoptic time scales in the cold sector. Based on these results, a simple boundary layer model is proposed to explain the convective and dynamical response to the SST gradient in the cold sector. In this model, cold and dry air parcels acquire more buoyancy over a sharp SST gradient and become more convectively unstable. The convection sets a pressure anomaly over the entire depth of the boundary layer that drives wind convergence. This case study offers a new pathway by which the SST gradient can anchor a climatological band of precipitation.
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Lee, Hansoo, Shannon D. Thomas, Sharath Paravastu, Tracie Barber, and Ramon L. Varcoe. "Dynamic Banding (DYBAND) Technique for Symptomatic High-Flow Fistulae." Vascular and Endovascular Surgery 54, no. 1 (September 10, 2019): 5–11. http://dx.doi.org/10.1177/1538574419874934.
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Introduction: High flow rates may develop in arteriovenous fistula (AVF), resulting in clinical syndromes of steal, aneurysmal fistula, or high-output cardiac failure. Various techniques with varying success have been advocated to treat this difficult problem. We present a hemodynamically validated novel banding technique. Methods: We designed a computational fluid dynamic (CFD) model of the native high-flow AVF and tested various juxta-anastomotic venous diameters to determine the effect on AVF blood flow and pressure. We translated this principle in our banding technique, wherein adjustable banding was performed in conjunction with ultrasound-guided brachial artery flow measurement to determine the optimal band diameter. Polyurethane patch was used to fashion the adjustable band. Patient demographics, AVF flow parameters pre- and postintervention, operative intervention, and ultrasound follow-up data were collected prospectively. Results: Our CFD testing demonstrated that the band diameter needed to achieve optimal distal blood pressure and preserve AVF flow depending on blood pressure, end capillary pressure, venous pressure, and vascular diameters. Five patients subsequently underwent dynamic banding of symptomatic high-flow AVF. Mean brachial artery blood flow rates pre- and postbanding were 2964 mL/min (confidence interval [CI]: 1487-4440 mL/min) and 1099 mL/min (CI: 571.7-1627 mL/min), respectively ( P = .01). All patients had symptomatic improvement, and at a mean follow-up of 1 year, this benefit was sustained with no AVF thrombosis or loss. Conclusion: Adjustable dynamic band using ultrasound-guided brachial artery flow shows promising results in producing accurate AVF blood flow reduction with sustained efficacy in the short term for patients with symptomatic high-flow AVF.
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Halliday, C., D. Carter, Z. C. Jackson, T. J. Bridges, N. W. Evans, and M. I. Wilkinson. "Dynamics of the Halo of the Andromeda Galaxy M31." Symposium - International Astronomical Union 209 (2003): 629–32. http://dx.doi.org/10.1017/s0074180900209893.
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We present an investigation of the halo dynamics of M31 using planetary nebulae velocities. We have performed on-band [OIII] and off-band continuum imaging for a 3.6 square degree area centred on M31 and follow-up spectroscopy for over 600 planetary nebulae candidates. In the future the halo mass will be measured and the mass distribution and velocity anisotropy will be constrained as a function of radius.
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Gurbatov, Sergey, and Efim Pelinovsky. "Probabilistic characteristics of narrow-band long-wave run-up onshore." Natural Hazards and Earth System Sciences 19, no. 9 (September 2, 2019): 1925–35. http://dx.doi.org/10.5194/nhess-19-1925-2019.
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Abstract. The run-up of random long-wave ensemble (swell, storm surge, and tsunami) on the constant-slope beach is studied in the framework of the nonlinear shallow-water theory in the approximation of non-breaking waves. If the incident wave approaches the shore from the deepest water, run-up characteristics can be found in two stages: in the first stage, linear equations are solved and the wave characteristics at the fixed (undisturbed) shoreline are found, and in the second stage the nonlinear dynamics of the moving shoreline is studied by means of the Riemann (nonlinear) transformation of linear solutions. In this paper, detailed results are obtained for quasi-harmonic (narrow-band) waves with random amplitude and phase. It is shown that the probabilistic characteristics of the run-up extremes can be found from the linear theory, while the same ones of the moving shoreline are from the nonlinear theory. The role of wave-breaking due to large-amplitude outliers is discussed, so that it becomes necessary to consider wave ensembles with non-Gaussian statistics within the framework of the analytical theory of non-breaking waves. The basic formulas for calculating the probabilistic characteristics of the moving shoreline and its velocity through the incident wave characteristics are given. They can be used for estimates of the flooding zone characteristics in marine natural hazards.
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Leon, David C., Jeffrey R. French, Sonia Lasher-Trapp, Alan M. Blyth, Steven J. Abel, Susan Ballard, Andrew Barrett, et al. "The Convective Precipitation Experiment (COPE): Investigating the Origins of Heavy Precipitation in the Southwestern United Kingdom." Bulletin of the American Meteorological Society 97, no. 6 (June 1, 2016): 1003–20. http://dx.doi.org/10.1175/bams-d-14-00157.1.
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Abstract The Convective Precipitation Experiment (COPE) was a joint U.K.–U.S. field campaign held during the summer of 2013 in the southwest peninsula of England, designed to study convective clouds that produce heavy rain leading to flash floods. The clouds form along convergence lines that develop regularly as a result of the topography. Major flash floods have occurred in the past, most famously at Boscastle in 2004. It has been suggested that much of the rain was produced by warm rain processes, similar to some flash floods that have occurred in the United States. The overarching goal of COPE is to improve quantitative convective precipitation forecasting by understanding the interactions of the cloud microphysics and dynamics and thereby to improve numerical weather prediction (NWP) model skill for forecasts of flash floods. Two research aircraft, the University of Wyoming King Air and the U.K. BAe 146, obtained detailed in situ and remote sensing measurements in, around, and below storms on several days. A new fast-scanning X-band dual-polarization Doppler radar made 360° volume scans over 10 elevation angles approximately every 5 min and was augmented by two Met Office C-band radars and the Chilbolton S-band radar. Detailed aerosol measurements were made on the aircraft and on the ground. This paper i) provides an overview of the COPE field campaign and the resulting dataset, ii) presents examples of heavy convective rainfall in clouds containing ice and also in relatively shallow clouds through the warm rain process alone, and iii) explains how COPE data will be used to improve high-resolution NWP models for operational use.
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Zheng, Zhang, Liu, Liu, and Che. "A Study of Vertical Structures and Microphysical Characteristics of Different Convective Cloud–Precipitation Types Using Ka-Band Millimeter Wave Radar Measurements." Remote Sensing 11, no. 15 (August 1, 2019): 1810. http://dx.doi.org/10.3390/rs11151810.
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Millimeter wave cloud radar (MMCR) is one of the primary instruments employed to observe cloud–precipitation. With appropriate data processing, measurements of the Doppler spectra, spectral moments, and retrievals can be used to study the physical processes of cloud–precipitation. This study mainly analyzed the vertical structures and microphysical characteristics of different kinds of convective cloud–precipitation in South China during the pre-flood season using a vertical pointing Ka-band MMCR. Four kinds of convection, namely, multi-cell, isolated-cell, convective–stratiform mixed, and warm-cell convection, are discussed herein. The results show that the multi-cell and convective–stratiform mixed convections had similar vertical structures, and experienced nearly the same microphysical processes in terms of particle phase change, particle size distribution, hydrometeor growth, and breaking. A forward pattern was proposed to specifically characterize the vertical structure and provide radar spectra models reflecting the different microphysical and dynamic features and variations in different parts of the cloud body. Vertical air motion played key roles in the microphysical processes of the isolated- and warm-cell convections, and deeply affected the ground rainfall properties. Stronger, thicker, and slanted updrafts caused heavier showers with stronger rain rates and groups of larger raindrops. The microphysical parameters for the warm-cell cloud–precipitation were retrieved from the radar data and further compared with the ground-measured results from a disdrometer. The comparisons indicated that the radar retrievals were basically reliable; however, the radar signal weakening caused biases to some extent, especially for the particle number concentration. Note that the differences in sensitivity and detectable height of the two instruments also contributed to the compared deviation.
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Dacre, H. F., O. Martínez-Alvarado, and C. O. Mbengue. "Linking Atmospheric Rivers and Warm Conveyor Belt Airflows." Journal of Hydrometeorology 20, no. 6 (June 1, 2019): 1183–96. http://dx.doi.org/10.1175/jhm-d-18-0175.1.
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Abstract Extreme precipitation associated with extratropical cyclones can lead to flooding if cyclones track over land. However, the dynamical mechanisms by which moist air is transported into cyclones is poorly understood. In this paper we analyze airflows within a climatology of cyclones in order to understand how cyclones redistribute moisture stored in the atmosphere. This analysis shows that within a cyclone’s warm sector the cyclone-relative airflow is rearwards relative to the cyclone propagation direction. This low-level airflow (termed the feeder airstream) slows down when it reaches the cold front, resulting in moisture flux convergence and the formation of a band of high moisture content. One branch of the feeder airstream turns toward the cyclone center, supplying moisture to the base of the warm conveyor belt where it ascends and precipitation forms. The other branch turns away from the cyclone center exporting moisture from the cyclone. As the cyclone travels, this export results in a filament of high moisture content marking the track of the cyclone (often used to identify atmospheric rivers). We find that both cyclone precipitation and water vapor transport increase when moisture in the feeder airstream increases, thus explaining the link between atmospheric rivers and the precipitation associated with warm conveyor belt ascent. Atmospheric moisture budgets calculated as cyclones pass over fixed domains relative to the cyclone tracks show that continuous evaporation of moisture in the precyclone environment moistens the feeder airstream. Evaporation behind the cold front acts to moisten the atmosphere in the wake of the cyclone passage, potentially preconditioning the environment for subsequent cyclone development.
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Sampe, Takeaki, and Shang-Ping Xie. "Large-Scale Dynamics of the Meiyu-Baiu Rainband: Environmental Forcing by the Westerly Jet*." Journal of Climate 23, no. 1 (January 1, 2010): 113–34. http://dx.doi.org/10.1175/2009jcli3128.1.
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Abstract Meiyu-baiu is the major rainy season from central China to Japan brought by a zonally elongated rainband from June to mid-July. Large-scale characteristics and environmental forcing of this important phenomenon are investigated based on a reanalysis dataset. The meiyu-baiu rainband is accompanied by a trough of sea level pressure, horizontal shears, and sharp moisture gradients near the surface, a westerly jet tilted northward with height, and large northeastward moisture transport from the south. The analysis here reveals the westerly jet as an important culprit for meiyu-baiu. Along the rainband, mean ascending motion corresponds well with a band of warm horizontal temperature advection in the midtroposphere throughout summer. This adiabatic induction of upward motion originates from the advection of warm air by the westerlies from the eastern flank of the Tibetan Plateau. The ascending motion both induces convection and is enhanced by the resultant condensational heating. The westerly jet anchors the meiyu-baiu rainband also by steering transient eddies, creating periods conducive to convection through convective instability and adiabatic updrafts. Indeed, in meiyu-baiu, the probability distribution of convective instability shows large spreads and is strongly skewed, with a sharp cutoff on the unstable side resulting from the effective removal of instability by convection. Thus, active weather disturbances in the westerly waveguide explain a paradox that convection is active in the meiyu-baiu rainband while mean convective instability is significantly higher to the south over the subtropical North Pacific warm pool. In addition to the westerly jet, low-level southerly winds over eastern China between the heat low over Asia and the subtropical high pressure belt over the Pacific are another important environmental forcing for meiyu-baiu by supplying moisture. A conceptual model for meiyu-baiu is presented, and its implications for seasonal and interannual variations are discussed.
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Padmalatha, Pournami, and Susy Thomas. "Discrete time reaching law based variable structure control for fast reaching with reduced chattering." IAES International Journal of Robotics and Automation (IJRA) 9, no. 1 (March 1, 2020): 51. http://dx.doi.org/10.11591/ijra.v9i1.pp51-61.
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In this paper, a variable structure control law is proposed for discrete time sliding mode control so as to reduce both reaching time and quasi sliding mode band reduction. This new law is composed of two different sliding variable dynamics; one to achieve fast reaching and the other to counter its effect on widening the quasi sliding mode band. This is accomplished<br />by introducing a boundary layer around the sliding surface about which the transformation of the sliding variable dynamics takes place. This provides the flexibility to choose the initial dynamics in such a way as to speed up the reaching phase and then at the boundary transform this dynamics to one that reduces the quasi sliding mode band. Thus, the law effectively<br />coalesces the advantageous traits of hitherto proposed reaching laws that succeed in either the reduction of reaching phase or the elimination of quasi sliding mode band. The effectiveness of the proposed reaching law is validated through simulations.<br /><br />
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Marcisz, J., W. Burian, R. Rozmus, and J. Janiszewski. "Microstructural Changes of the Nanostructured Bainitic Steel Induced by Quasi-Static and Dynamic Deformation." Archives of Metallurgy and Materials 62, no. 4 (December 1, 2017): 2317–29. http://dx.doi.org/10.1515/amm-2017-0341.
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AbstractChanges in the microstructure of nanostructured bainitic steel induced by quasi-static and dynamic deformation have been shown in the article. The method of deformation and strain rate have important impact on the microstructure changes especially due to strain localization. Microstructure of nanostructured steel Fe-0.6%C-1.9Mn-1.8Si-1.3Cr-0.7Mo consists of nanometer size carbide-free bainite laths and 20-30% volume fraction of retained austenite. Quasi-static and dynamic (strain rate up to 2×102s−1) compression tests were realized using Gleeble simulator. Dynamic deformation at the strain rate up to 9×103s−1was realized by the Split Hopkinson Pressure Bar method (SHPB). Moreover high energy firing tests of plates made of the nanostructured bainitic steel were carried out to produce dynamically deformed material for investigation. Adiabatic shear bands were found as a result of localization of deformation in dynamic compression tests and in firing tests. Microstructure of the bands was examined and hardness changes in the vicinity of the bands were determined. The TEM examination of the ASBs showed the change from the internal shear band structure to the matrix structure to be gradual. This study clearly resolved that the interior (core) of the band has an extremely fine grained structure with grain diameter ranging from 100 nm to 200 nm. Martensitic twins were found within the grains. No austenite and carbide reflections were detected in the diffraction patterns taken from the core of the band. Hardness of the core of the ASBs for examined variants of isothermal heat treatment was higher about 300 HV referring to steel matrix hardness.
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Bou, Jordi, Antònia Caritat, and Lluís Vilar. "Litterfall and growth dynamics relationship with the meteorological variability in three forests in the Montseny natural park." Folia Forestalia Polonica 57, no. 3 (September 1, 2015): 145–59. http://dx.doi.org/10.1515/ffp-2015-0015.
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AbstractWe assessed the influence of some environmental conditions (temperature and rainfall) on the litterfall and BAI (basal area increment), in three close forests in the Montseny massif (NE part of the Iberian peninsula, Spain). Two of them are composed of deciduous speciesFagus sylvaticaandQuercus petraea, and the other one is a Mediterranean evergreen species,Quercus ilex. We have collected monthly data about litterfall and radial growth since 2007. For each forest there are tree plots, with litterfall traps and band dendrometers. This data has been related with the meteorological parameters of meteorological station closed to the study area. Our results show thatF. sylvaticarecorded the biggest drop in annual litterfall (6 Mg·ha−1·year−1), followed byQ. ilex(4.34 Mg·ha−1·year−1) andQuercus petraea(4.4 Mg·ha−1·year−1) and that all the values were similar to those observed in other forests and mountains with the same state of maturity. Regarding the litterfall, the investigation found a decline in the leaves fall in deciduous trees in years with hot summers. In addition, these warm summers produce a decline in theF. sylvaticaBAI, but not inQ. petraea. Concerning growth, we found thatQ. petraeaincreases the BAI on the study period whileF. sylvaticadoes not. In conclusion, we believe that in the futureQ. petraeawill be more tolerant to the warm conditions thanF. sylvatica, making the former a possible replacement of the second species.
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Oertel, Annika, Maxi Boettcher, Hanna Joos, Michael Sprenger, and Heini Wernli. "Potential vorticity structure of embedded convection in a warm conveyor belt and its relevance for large-scale dynamics." Weather and Climate Dynamics 1, no. 1 (April 9, 2020): 127–53. http://dx.doi.org/10.5194/wcd-1-127-2020.
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Abstract. Warm conveyor belts (WCBs) are important airstreams in extratropical cyclones. They can influence large-scale flow evolution by modifying the potential vorticity (PV) distribution during their cross-isentropic ascent. Although WCBs are typically described as slantwise-ascending and stratiform-cloud-producing airstreams, recent studies identified convective activity embedded within the large-scale WCB cloud band. However, the impacts of this WCB-embedded convection have not been investigated in detail. In this study, we systematically analyze the influence of embedded convection in an eastern North Atlantic WCB on the cloud and precipitation structure, on the PV distribution, and on larger-scale flow. For this reason, we apply online trajectories in a high-resolution convection-permitting simulation and perform a composite analysis to compare quasi-vertically ascending convective WCB trajectories with typical slantwise-ascending WCB trajectories. We find that the convective WCB ascent leads to substantially stronger surface precipitation and the formation of graupel in the middle to upper troposphere, which is absent for the slantwise WCB category, indicating the key role of WCB-embedded convection for precipitation extremes. Compared to the slantwise WCB trajectories, the initial equivalent potential temperature of the convective WCB trajectories is higher, and the convective WCB trajectories originate from a region of larger potential instability, which gives rise to more intense cloud diabatic heating and stronger cross-isentropic ascent. Moreover, the signature of embedded convection is distinctly imprinted in the PV structure. The diabatically generated low-level positive PV anomalies, associated with a cyclonic circulation anomaly, are substantially stronger for the convective WCB trajectories. The slantwise WCB trajectories lead to the formation of a widespread region of low-PV air (that still have weakly positive PV values) in the upper troposphere, in agreement with previous studies. In contrast, the convective WCB trajectories form mesoscale horizontal PV dipoles at upper levels, with one pole reaching negative PV values. On a larger scale, these individual mesoscale PV anomalies can aggregate to elongated PV dipole bands extending from the convective updraft region, which are associated with coherent larger-scale circulation anomalies. An illustrative example of such a convectively generated PV dipole band shows that within around 10 h the negative PV pole is advected closer to the upper-level waveguide, where it strengthens the isentropic PV gradient and contributes to the formation of a jet streak. This suggests that the mesoscale PV anomalies produced by embedded convection upstream organize and persist for several hours and therefore can influence the synoptic-scale circulation. They thus can be dynamically relevant, influence the jet stream and (potentially) the downstream flow evolution, which are highly relevant aspects for medium-range weather forecast. Finally, our results imply that a distinction between slantwise and convective WCB trajectories is meaningful because the convective WCB trajectories are characterized by distinct properties.
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Inoue, Satoru, Mitsuru Tamaki, Hiroshi Kawazoe, and Masayuki Yamane. "Estimation of the infrared absorption of ZnCl2–KBr glass by molecular dynamics." Journal of Materials Research 2, no. 3 (June 1987): 357–60. http://dx.doi.org/10.1557/jmr.1987.0357.
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Molecular dynamic calculations have been made on glasses in the ZnCl2–KBr system in order to estimate the infrared (IR) absorption of these glasses. Oxygen-free glass was estimated to be transparent up to 25 μm. Glasses containing oxygen impurities were estimated to be transparent only up to 16 μm, with a weak absorption band around 10.4 μm. This agrees with experimental results of glasses in the ZnCl2–KBr–PbBr2 system.
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Pole, Stephen J. "Application of Matlab and Simulink to a Low-Lift Sump System." Measurement and Control 25, no. 8 (October 1992): 234–39. http://dx.doi.org/10.1177/002029409202500802.
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This paper describes the application of a computer-aided control system design (CACSD) tool known as Simulink. Simulink is a modern non-linear dynamic simulation tool and forms an extension to Matlab,* adding many features specific to dynamic systems. The application of Simulink to a water treatment works pumping station is outlined. The objective is to enable a complex simulation model of the plant (block diagram descriptions), including all relevant process dynamics, to be easily built up. Using this simulation model a control strategy is designed to maintain the water level in a two well sump within a specified operating band. The level constraint has to be met irrespective of inflow transients due to filter washes, surges, etc. Having designed the controller based upon plant model simulations, the control algorithms were coded in the programmable logic controller (PLC) to be used on the plant. The PLC was interfaced to the plant model in real time to validate the performance of the controller against the simulated plant. The application of Simulink for plant modelling and analysis proved to be successful in that a controller was easily designed and implemented, and exceeded the performance specifications.
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Shiau, L. J., S. C. Clemens, M. T. Chen, M. Yamamoto, and Y. Yokoyama. "SST phases in the open-ocean and margins of the tropical Pacific; implication on tropical climate dynamics." Climate of the Past Discussions 10, no. 2 (April 28, 2014): 1857–99. http://dx.doi.org/10.5194/cpd-10-1857-2014.
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Abstract. The tropical Pacific exerts a major effect on the global climate system and might have driven large extra-tropical climate change. We present a 320 kyr high resolution UK'37-sea surface temperature (SST) record from core MD052928 (11°17.26' S, 148°51.60' E, water depth 2250 m) located off southeastern Papua New Guinea (PNG), in the western tropical Pacific. The age model of the core is based on AMS 14C dating of planktic foraminifers and correlation of benthic to the LR04 stack. The UK'37-SST ranges from 26.5 to 29 °C, showing glacial–interglacial and millennial variations. We assess the phase of the MD052928 UK'37-SST as part of a synthesis of five other SST records from the tropical Pacific at the precession, obliquity, and eccentricity bands. The SST records can be separated into two groups when considering SST phase relative to changes in orbital forcing, ice volume and greenhouse gases (GHGs). SST maxima at open-ocean sites within primary equatorial current systems occur between obliquity maxima and methane (CH4) maxima but early relative to ice volume minima and CO2 maxima at the obliquity band. In contrast, SST maxima at continental margin sites change are in phase with ice minima and CO2 maxima, likely influenced by the slow response of continental ice sheets and GHGs. At the precession band, the early group located on the Warm Pool area indicates a direct influenced by the local insolation, and with the similar phase progress as the obliquity band. These results indicate that the decreased high-low latitudes insolation gradient and increasing low latitude local insolation resulting in tropical Pacific SST rise. Higher SST would supply more moisture resulting in increased CH4 in the tropical wetlands. This promotes increasing CO2 and deglaciation leading to increase continental and continental margin surface temperatures.
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James, P. M., and D. Peters. "The Lagrangian structure of ozone mini-holes and potential vorticity anomalies in the Northern Hemisphere." Annales Geophysicae 20, no. 6 (June 30, 2002): 835–46. http://dx.doi.org/10.5194/angeo-20-835-2002.
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Abstract. An ozone mini-hole is a synoptic-scale area of strongly reduced column total ozone, which undergoes a growth-decay cycle in association with baroclinic weather systems. The tracks of mini-hole events recorded during the TOMS observation period over the Northern Hemisphere provide a database for building anomaly fields of various meteorological parameters, following each mini-hole center in a Lagrangian sense. The resulting fields provide, for the first time, a complete mean Lagrangian picture of the three-dimensional structure of typical ozone mini-holes in the Northern Hemisphere. Mini-holes are shown to be associated with anomalous warm anticyclonic flow in the upper troposphere and cold cyclonic anomalies in the middle stratosphere. Ascending air columns occur upstream and descent downstream of the mini-hole centers. Band-pass filtering is used to reveal the transient synoptic nature of mini-holes embedded within larger scale circulation anomalies. Significant correlations between ozone and Ertel’s potential vorticity on isentropes (IPV) both near the tropopause and in the middle stratosphere are shown and then utilized by reconstructing the Lagrangian analysis to follow local IPV anomalies instead of ozone minima. By using IPV as a proxy for ozone, the geopotential anomaly dipolar structure in the vertical characteristic of mini-holes is shown to result from a superposition of two largely independent dynamical components, stratospheric and tropospheric, typically operating on different time scales. Hence, ozone mini-holes may be viewed primarily as phenomena of coincidence.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; synoptic-scale meteorology)
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Yamamoto, M., H. Sai, M. T. Chen, and M. Zhao. "The East Asian winter monsoon variability in response to precession during the past 150 000 yr." Climate of the Past 9, no. 6 (December 13, 2013): 2777–88. http://dx.doi.org/10.5194/cp-9-2777-2013.
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Abstract. The response of the East Asian winter monsoon variability to orbital forcing is still unclear, and hypotheses are controversial. We present a 150 000 yr record of sea surface temperature difference (ΔSST) between the South China Sea and other Western Pacific Warm Pool regions as a proxy for the intensity of the Asian winter monsoon, because the winter cooling of the South China Sea is caused by the cooling of surface water at the northern margin and the southward advection of cooled water due to winter monsoon winds. The ΔSST showed dominant precession cycles during the past 150 000 yr. The ΔSST varies at precessional band and supports the hypothesis that monsoon is regulated by insolation changes at low-latitudes (Kutzbach, 1981), but contradicts previous suggestions based on marine and loess records that eccentricity controls variability on glacial–interglacial timescales. Maximum winter monsoon intensity corresponds to the May perihelion at precessional band, which is not fully consistent with the Kutzbach model of maximum winter monsoon at the June perihelion. Variation in the East Asian winter monsoon was anti-phased with the Indian summer monsoon, suggesting a linkage of dynamics between these two monsoon systems on an orbital timescale.
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Hu, R. C., X. F. Wang, X. D. Gu, and R. H. Huan. "Nonlinear Stochastic Optimal Control of MDOF Partially Observable Linear Systems Excited by Combined Harmonic and Wide-Band Noises." International Journal of Structural Stability and Dynamics 19, no. 03 (March 2019): 1950019. http://dx.doi.org/10.1142/s0219455419500196.
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In this paper, nonlinear stochastic optimal control of multi-degree-of-freedom (MDOF) partially observable linear systems subjected to combined harmonic and wide-band random excitations is investigated. Based on the separation principle, the control problem of a partially observable system is converted into a completely observable one. The dynamic programming equation for the completely observable control problem is then set up based on the stochastic averaging method and stochastic dynamic programming principle, from which the nonlinear optimal control law is derived. To illustrate the feasibility and efficiency of the proposed control strategy, the responses of the uncontrolled and optimal controlled systems are respectively obtained by solving the associated Fokker–Planck–Kolmogorov (FPK) equation. Numerical results show the proposed control strategy can dramatically reduce the response of stochastic systems subjected to both harmonic and wide-band random excitations.
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Dabrowski, Bartosz, Paweł Flisek, Katarzyna Mikuła, Adam Froń, Christian Vocks, Jasmina Magdalenić, Andrzej Krankowski, PeiJin Zhang, Pietro Zucca, and Gottfried Mann. "Type III Radio Bursts Observations on 20th August 2017 and 9th September 2017 with LOFAR Bałdy Telescope." Remote Sensing 13, no. 1 (January 5, 2021): 148. http://dx.doi.org/10.3390/rs13010148.
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We present the observations of two type III solar radio events performed with LOFAR (LOw-Frequency ARray) station in Bałdy (PL612), Poland in single mode. The first event occurred on 20th August 2017 and the second one on 9th September 2017. Solar dynamic spectra were recorded in the 10 MHz up to 90 MHz frequency band. Together with the wide frequency bandwidth LOFAR telescope (with single station used) provides also high frequency and high sensitivity observations. Additionally to LOFAR observations, the data recorded by instruments on boards of the Interface Region Imaging Spectrograph (IRIS) and Solar Dynamics Observatory (SDO) in the UV spectral range complement observations in the radio field. Unfortunately, only the radio event from 9th September 2017 was observed by both satellites. Our study shows that the LOFAR single station observations, in combination with observations at other wavelengths can be very useful for better understanding of the environment in which the type III radio events occur.
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JOVANOVIĆ, GORAN, DARKO MITIĆ, MILE STOJČEV, and DRAGAN ANTIĆ. "SELF-TUNING BIQUAD BAND-PASS FILTER." Journal of Circuits, Systems and Computers 22, no. 03 (March 2013): 1350008. http://dx.doi.org/10.1142/s0218126613500084.
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One approach to design self-tuning gm-C biquad band-pass filter is considered in this paper. The phase control loop is introduced to force filter central frequency to be equal to input signal frequency what is achieved by adjusting the amplifier transconductance gm. Thanks to that, the filter is robust to parameter perturbations and it can be used as a selective amplifier. In the full tuning range, it has a constant maximum gain at central frequency as well as a constant bandwidth. The 0.25 μm SiGe BiCMOS technology was used during design and verification of the band-pass filter. The filter has 26 dB gain, quality factor Q = 20 and central frequency up to 150 MHz. Simulation results indicate that the total in-band noise is 59 μV rms , the output third intercept point OIP3 = 4.36 dB and the dynamic range is 35 dB. Maximal power consumption at 3 V power supply is 1.115 mW.
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Jensen, S. S., J. K. Jørgensen, L. E. Kristensen, K. Furuya, A. Coutens, E. F. van Dishoeck, D. Harsono, and M. V. Persson. "ALMA observations of water deuteration: a physical diagnostic of the formation of protostars." Astronomy & Astrophysics 631 (October 15, 2019): A25. http://dx.doi.org/10.1051/0004-6361/201936012.
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Context. How water is delivered to planetary systems is a central question in astrochemistry. The deuterium fractionation of water can serve as a tracer for the chemical and physical evolution of water during star formation and can constrain the origin of water in Solar System bodies. Aims. The aim is to determine the HDO/H2O ratio in the inner warm gas toward three low-mass Class 0 protostars selected to be in isolated cores, i.e., not associated with any cloud complexes. Previous sources for which the HDO/H2O ratio have been established were all part of larger star-forming complexes. Determining the HDO/H2O ratio toward three isolated protostars allows comparison of the water chemistry in isolated and clustered regions to determine the influence of local cloud environment. Methods. We present ALMA Band 6 observations of the HDO 31,2–22,1 and 21,1–21,2 transitions at 225.897 GHz and 241.562 GHz along with the first ALMA Band 5 observations of the H218O 31,3–22,0 transition at 203.407 GHz. The high angular resolution observations (0′′.3–1′′.3) allow the study of the inner warm envelope gas. Model-independent estimates for the HDO/H2O ratios are obtained and compared with previous determinations of the HDO/H2O ratio in the warm gas toward low-mass protostars. Results. We successfully detect the targeted water transitions toward the three sources with signal-to-noise ratio (S/N) > 5. We determine the HDO/H2O ratio toward L483, B335 and BHR71–IRS1 to be (2.2 ± 0.4) × 10−3, (1.7 ± 0.3) × 10−3, and (1.8 ± 0.4) × 10−3, respectively, assuming Tex = 124 K. The degree of water deuteration of these isolated protostars are a factor of 2–4 higher relative to Class 0 protostars that are members of known nearby clustered star-forming regions. Conclusions. The results indicate that the water deuterium fractionation is influenced by the local cloud environment. This effect can be explained by variations in either collapse timescales or temperatures, which depends on local cloud dynamics and could provide a new method to decipher the history of young stars.
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Oprea, I. C., and A. Bell. "Meteorological environment of a tornado outbreak in Southern Romania." Natural Hazards and Earth System Sciences 9, no. 2 (April 23, 2009): 609–22. http://dx.doi.org/10.5194/nhess-9-609-2009.
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Abstract. On 7 May 2005, a squall line with an embedded bow echo formed over Southern Romania causing severe wind damage. The length of the wind damage was around 150 km. Three tornadoes have been reported, two of them being recorded by video camera. One of the tornadoes occurred in Buftea (near Bucharest), the second in Ciobanu village (near Medgidia radar site) and the third in Movilita village, 40 km to the northeast of Bucharest. The site surveys confirmed wind damage associated with these tornadoes. Based on damage, the Movilita village tornado was classified as an F1 type on the Fujita scale, and the Buftea and Ciobanu village tornadoes were classified as F0. Large scale forcing was provided by a vigorous upper level trough. The squall line developed in the warm sector of a low, ahead of the cold front. The Bucharest EEC-DWSR-2500C Doppler velocity depicted cyclonically rotational structures associated with the left end of the bow echo. In two hours this squall line traversed the southern part of the country. The northern end of the line preserved the bowed structures and high reflectivity gradient in front of them. The dry air associated with the descending rear inflow jet was evident as rear inflow notches in the reflectivity field of the Bucharest C-band radar and the Medgidia S-band WSR-98 D radar. The synoptic and mesoscale environment associated with 7 May 2005 bow echo had many similarities to the "dynamic" pattern described by John and Hirt (1987). Herein are analyzed the combined effects of synoptic and mesoscale circulations, together with the data provided by C-band EEC-DWSR-2500C and S-band WSR-98D radars, and the ECMWF and ALADIN model output data. Some operational aspects of the warning process are also discussed.
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Manzhos, Sergei. "Effects of Nuclear Vibrations on the Energetics of Polythiophene: Quantized Energy Molecular Dynamics." Australian Journal of Chemistry 66, no. 9 (2013): 1021. http://dx.doi.org/10.1071/ch13112.
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The effects of nuclear dynamics on the energetics of polythiophene relevant for the performance of organic solar cells are studied for the first time. Nuclear motions change the expectation values of frontier orbital energies and the band gap by ~0.1 eV versus values at the equilibrium geometry, which is expected to have a significant effect on light absorption, charge separation, and donor regeneration. A new molecular dynamics algorithm that accounts for the quantum nature of vibrations is introduced. It reproduces effects of temperature and deuteration that are lost in the standard molecular dynamics. Inclusion of quantized vibrations leads to a broadening of the band gap and of energy levels by ~20 % at 300 K, while having little effect on their expectation values (which change by up to 0.03 eV). Increase in temperature from 300 to 400 K and deuteration cause an additional broadening of the spectrum by ~26 and 21 % respectively.
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Midgett, Madeline, Sevan Goenezen, and Sandra Rugonyi. "Blood flow dynamics reflect degree of outflow tract banding in Hamburger–Hamilton stage 18 chicken embryos." Journal of The Royal Society Interface 11, no. 100 (November 6, 2014): 20140643. http://dx.doi.org/10.1098/rsif.2014.0643.
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Altered blood flow during embryonic development has been shown to cause cardiac defects; however, the mechanisms by which the resulting haemodynamic forces trigger heart malformation are unclear. This study used heart outflow tract banding to alter normal haemodynamics in a chick embryo model at HH18 and characterized the immediate blood flow response versus the degree of band tightness. Optical coherence tomography was used to acquire two-dimensional longitudinal structure and Doppler velocity images from control ( n = 16) and banded ( n = 25, 6–64% measured band tightness) embryos, from which structural and velocity data were extracted to estimate haemodynamic measures. Peak blood flow velocity and wall shear rate (WSR) initially increased linearly with band tightness ( p < 0.01), but then velocity plateaued between 40% and 50% band tightness and started to decrease with constriction greater than 50%, whereas WSR continued to increase up to 60% constriction before it began decreasing with increased band tightness. Time of flow decreased with constriction greater than 20% ( p < 0.01), while stroke volume in banded embryos remained comparable to control levels over the entire range of constriction ( p > 0.1). The haemodynamic dependence on the degree of banding reveals immediate adaptations of the early embryonic cardiovascular system and could help elucidate a range of cardiac adaptations to gradually increased load.
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Mazón, J., and D. Pino. "The role of nocturnal Low-Level-Jet in nocturnal convection and rainfalls in the west Mediterranean coast: the episode of 14 December 2010 in northeast of Iberian Peninsula." Advances in Science and Research 8, no. 1 (March 19, 2012): 27–31. http://dx.doi.org/10.5194/asr-8-27-2012.
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Abstract. The night of 14 December 2010 radar images of the Spanish Weather Agency recorded a large rain band that moved offshore at the Northeast coast of the Iberian Peninsula. MM5 mesoscale model is used to study the atmospheric dynamics during that day. A Nocturnal Low Level Jet (NLLJ) generated by an inertial oscillation that brings cold air to the coast from inland has been simulated in the area. This cold air interacts with a warmer air mass some kilometers offshore. According to the MM5 mesoscale model simulation, the cold air enhances upward movements of the warm air producing condensation. Additionally, there is a return flow to the coastline at 600–900 m high. This warm air mass interacts again with the cold air moving downslope, also producing condensation inland. The simulation for the night before this episode shows large drainage winds with a NLLJ profile, but no condensation areas. The night after the 14th the simulation also shows drainage winds but without a NLLJ profile. However, an offshore convergence area was produced with a returned flow, but no condensation inland occurred. This fact is in agreement with radar observations which reported no precipitation for these two days. Consequently, NLLJ in combination with a synoptic wind over the sea could enhance condensation and eventually precipitation rates in the Mediterranean Iberian coast.
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Roundy, Paul E. "Regression Analysis of Zonally Narrow Components of the MJO." Journal of the Atmospheric Sciences 71, no. 11 (October 29, 2014): 4253–75. http://dx.doi.org/10.1175/jas-d-13-0288.1.
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Abstract Recent works have demonstrated that eastward-propagating features smaller than zonal wavenumber 3 but with spatial structures similar to those of the Madden–Julian oscillation (MJO) frequently develop over the Indo-Pacific warm pool. These signals are characterized by periods shorter than 4 weeks, but since they occur as part of a spectral peak of the MJO, they might be characterized by similar physics. These zonally narrow features occur at any phase of traditionally defined 30–60-day MJO events, but they occur most frequently in its active convective phase. This work presents a linear regression analysis based on filtering in the wavenumber–frequency domain to compare such signals with traditionally defined MJOs and 15–30 m s−1, convectively coupled Kelvin waves. Results show that the trough collocated with the easterly wind anomaly extends westward into the region of lower-tropospheric westerly wind and deep convection in the zonally narrow slow signals and MJOs. The fast Kelvin waves have a ridge anomaly collocated with the westerly wind anomaly. The zonally narrow slow signals and MJOs include a warm anomaly in the boundary layer west of the deep convection that is absent in fast Kelvin waves. Results suggest that MJO dynamics are not confined to the 30–60-day band and that time scales as short as 2 weeks could be considered in wavenumber–frequency diagnostics for the MJO.
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Taie, Shintaro, Hideki Ozawa, Tomohiro Ichinose, Takuei Nishio, Shuta Nakajima, and Yoshiro Takahashi. "Coherent driving and freezing of bosonic matter wave in an optical Lieb lattice." Science Advances 1, no. 10 (November 2015): e1500854. http://dx.doi.org/10.1126/sciadv.1500854.
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Although kinetic energy of a massive particle generally has quadratic dependence on its momentum, a flat, dispersionless energy band is realized in crystals with specific lattice structures. Such macroscopic degeneracy causes the emergence of localized eigenstates and has been a key concept in the context of itinerant ferromagnetism. We report the realization of a “Lieb lattice” configuration with an optical lattice, which has a flat energy band as the first excited state. Our optical lattice potential has various degrees of freedom in its manipulation, which enables coherent transfer of a Bose-Einstein condensate into the flat band. In addition to measuring lifetime of the flat band population for different tight-binding parameters, we investigate the inter-sublattice dynamics of the system by projecting the sublattice population onto the band population. This measurement clearly shows the formation of the localized state with the specific sublattice decoupled in the flat band, and even detects the presence of flat-band breaking perturbations, resulting in the delocalization. Our results will open up the possibilities of exploring the physics of flat bands with a highly controllable quantum system.
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Xu, Guang-Hui. "Dynamic Parameter Optimization and Experimental Study of Tuned Slab Damper on Metro Systems." Shock and Vibration 2019 (February 17, 2019): 1–14. http://dx.doi.org/10.1155/2019/1236827.
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With the increase of axle weight and speed, the interaction between vehicles and the track becomes more and more intense, and the problem of wheel-rail dynamic action is more serious. In order to reduce the low-frequency vibration caused by train operation, a three-layer elastic track damping structure is proposed. The complex method is used to optimize the dynamic parameters, structural patterns, and coupling relations of the track structure, which allows multiple elastic units to work in harmony with each other to achieve the effects of absorbing vibration energy and reducing vibration transmission. Finally, a real size model experimental platform is set up to verify the dynamic parameter optimization results. The results show that the vertical mode of the main track system of the coupling-tuned slab damper-floating slab is 26.898 Hz close to the train excitation frequency, and the corresponding equivalent mass is 6074.53 kg. The amplitude of the vibration components in the 20∼40 Hz band can be reduced to 41.8% by using the complex method. The maximum insertion loss is about 10 dB, and the vibration of low-frequency band is not amplified.
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Alves Pires, Felipe, Luca Sangiuliano, Noé Geraldo Rocha de Melo Filho, Denayer Hervé, Elke Deckers, Wim Desmet, and Claus Claeys. "Resonant metamaterial designs for a broadband mitigation of flow-induced vibrations." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, no. 3 (August 1, 2021): 3235–46. http://dx.doi.org/10.3397/in-2021-2344.
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Resonant metamaterials have recently emerged as lightweight and performant noise and vibration solutions for the hard-to-address low-frequency ranges. These engineered materials are made by an assembly of resonant elements onto a host structure. Their interaction leads to tuneable frequency ranges, known as stop bands, in which they can outperform classical noise control measures. However, these stop bands have a limited frequency range effect. To broaden the noise and vibration performance also outside the stop band, this paper presents a design approach for a finite resonant metamaterial plate. Two regularly spaced grids of resonant elements are both added to a plate. In the first grid, the resonant elements are tuned to the same nominal frequency and stop band behaviour is achieved. In the second grid, the tuned frequency of each resonant element is found through an optimisation procedure, with the goal of minimising the dynamic response of the plate outside the stop band. To speed up the optimisation, model order reduction and a dynamic sub-structuring method are employed. The performance of this finite resonant metamaterial plate design is validated by evaluating its vibration response due to a broadband grazing flow excitation and comparing it to a plate with equivalent mass additions.
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Zhao, Zi Yue, Zhi Hong Fan, Jing Jun Zhang, and Zi Qiang Xia. "Research on Ride Comfort of Nonlinear Vehicle Suspension." Advanced Materials Research 605-607 (December 2012): 443–47. http://dx.doi.org/10.4028/www.scientific.net/amr.605-607.443.
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In this paper, in order to study the effect of nonlinear suspension system, a nonlinear dynamic model considering nonlinearity of suspension is built and another model with the respective of linear suspension system is developed which is for comparison. Then the dynamic equation of the model is set up. The simulation is accomplished through MATLAB/SIMULINK. It is found that the band-limited white noise module can simulate the power spectral density of road surface well. Finally, numerical simulation results indicates that an appropriate nonlinear suspension model fits reality better than a linear one and using relative control can provide the best ride comfort.