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The VLT LBG redshift survey – VI. Mapping H?i in the proximity of z?～?3 LBGs with X-Shooter
摘要： We present an analysis of the spatial distribution and dynamics of neutral hydrogen gas around galaxies using new X-Shooter observations of z ～ 2.5–4 quasars. Adding the X-Shooter data to our existing data set of high-resolution quasar spectroscopy, we use a total sample of 29 quasars alongside ～1700 Lyman Break Galaxies (LBGs) in the redshift range 2 (cid:2) z (cid:2) 3.5. We measure the Lyα forest auto-correlation function, finding a clustering length of s0 = 0.081 ± 0.006 h?1 Mpc, and the cross-correlation function with LBGs, finding a cross-clustering length of s0 = 0.27 ± 0.14 h?1 Mpc and power-law slope γ = 1.1 ± 0.2. Our results highlight the weakly clustered nature of neutral hydrogen systems in the Lyα forest. Building on this, we make a first analysis of the dependence of the clustering on absorber strength, finding a clear preference for stronger Lyα forest absorption features to be more strongly clustered around the galaxy population, suggesting that they trace on average higher mass haloes. Using the projected and 2-D cross-correlation functions, we constrain the dynamics of Lyα forest clouds around z ～ 3 galaxies. We find a significant detection of large-scale infall of neutral hydrogen, with a constraint on the Lyα forest infall parameter of βF = 1.02 ± 0.22.
关键词： cosmology: observations,large-scale structure of Universe,intergalactic medium,galaxies: kinematics and dynamics
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE International Conference on Environment and Electrical Engineering and 2018 IEEE Industrial and Commercial Power Systems Europe (EEEIC / I&CPS Europe) - Palermo (2018.6.12-2018.6.15)] 2018 IEEE International Conference on Environment and Electrical Engineering and 2018 IEEE Industrial and Commercial Power Systems Europe (EEEIC / I&CPS Europe) - Nonlinear Multi-Scale Dynamics Modeling of a Piezoelectric Energy Harvester
摘要： Hysteretic effects play a crucial role in the behavior of devices based on piezoelectric materials. Most of the research focuses on modeling these effects for controlling the dynamic response of piezoelectric actuators. Few studies discuss how hysteresis influences power generation and performances of energy harvesters based on such active materials. In this paper, a recently developed physics-based model of a PZT crystal is employed to assess the effects of material mesoscopic variables on the macroscopic response of a piezoelectric energy harvester modeled as a SDOF system. A multi-scale approach is adopted where, at the mesoscale, crystal domain switching - the source of hysteretic behavior - is taken into account through a probabilistic thermodynamic approach. Effects of hysteretic nonlinearities on harvesting performances of the considered device are investigated by means of simulations. A comparison between predictions of two models - with and without hysteresis - is also reported.
关键词： Piezoelectric,Hysteresis,Energy harvesting,Nonlinear Multi-scale Dynamics
更新于2025-09-23 15:22:29
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A case study of gravity wave dissipation in the polar MLT region using sodium LIDAR and radar data
摘要： This paper is primarily concerned with an event observed from 16:30 to 24:30 UT on 29 October 2010 during a very geomagnetically quiet interval (Kp ≤ 1). The sodium LIDAR observations conducted at Troms?, Norway (69.6? N, 19.2? E) captured a clearly discernible gravity wave (GW) signature. Derived vertical and horizontal wavelengths, maximum amplitude, apparent and intrinsic period, and horizontal phase velocity were about ～ 11.9 km, ～ 1.38 × 103 km, ～ 15 K, 4 h, ～ 7.7 h, and ～ 96 m s?1, respectively, between a height of 80 and 95 km. Of particular interest is a temporal development of the uppermost altitude that the GW reached. The GW disappeared around 95 km height between 16:30 and 21:00 UT, while after 21:00 UT the GW appeared to propagate to higher altitudes (above 100 km). We have evaluated three mechanisms (critical-level filtering, convective and dynamic instabilities) for dissipations using data obtained by the sodium LIDAR and a meteor radar. It is found that critical-level filtering did not occur, and the convective and dynamic instabilities occurred on some occasions. MF radar echo power showed significant enhancements between 18:30 and 21:00 UT, and an overturning feature of the sodium mixing ratio was observed between 18:30 and 21:20 UT above about 95 km. From these results, we have concluded that the GW was dissipated by wave breaking and instabilities before 21:00 UT. We have also investigated the difference of the background atmosphere for the two intervals and would suggest that a probable cause of the change in the GW propagation was due to the difference in the temperature gradient of the background atmosphere above 94 km.
关键词： Meteorology and atmospheric dynamics (waves and tides)
更新于2025-09-23 15:22:29
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Side chain dynamics in semiconducting polymer MEH‐PPV
摘要： The characteristic nanoscale dynamics of the alkyl side groups in the light-emitting polymer poly[2-methoxy-5-(20-ethyl-hexyloxy)-1,4-phenylene vinylene] have been investigated using quasi-elastic neutron scattering (QENS). The measurements were taken below the polymer’s glass transition (T ≤ Tg ’ 353 K), where the main backbone is in a rigid state and does not contribute to the broadening of the QENS signal. An analytical diffusion model consisting of a static term and two dynamical components, characterizing the flexible side groups, provide an excellent fit to the experimental data. The two observed dynamical processes are all localized in character, with no meaningful dependence on temperature. The faster process, with characteristic timescale of (cid:2)18 ps at room temperature (RT), can be linked to the average mobility of the terminal protons of the alkyl chain, while the slower process, with characteristic timescale of (cid:2)170 ps at RT, to those protons at the other end of the alkyl chain, closest to the backbone. While the fraction of mobile protons contributing to the QENS signal increases with increasing temperature, the characteristic timescale and confining volume within which the protons are able to move locally depend chiefly on the polymer conformational state. ? 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47394.
关键词： quasi-elastic neutron scattering,semi-conducting polymer,optical and photovoltaic applications,polymer dynamics,spectroscopy
更新于2025-09-23 15:22:29
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A study of surface diffusion of ternary (Cu-Ag-Zr) adatoms clusters for applications in thin film formation
摘要： This study presents the diffusion of heterogeneous ternary (Cu‐Ag‐Zr) adatoms clusters on Ag(111) using molecular dynamics techniques which could be important for the surface phenomena's and helpful for the ternary cluster's growth and formation of ternary alloy‐based thin films. The mechanism of nanoscale surface diffusion is investigated for 1Cu‐1Ag‐1Zr, 2Cu‐2Ag‐2Zr, 3Cu‐3Ag‐3Zr, and 4Cu‐4Ag‐4Zr clusters at temperatures 300, 500, and 700 K. The diffusion mechanism displays that the diffusion of trimer cluster exhibits hopping, sliding, and shearing at 300 K, whereas for hexamer, nonamer, and decamer, the diffusion rate is low; however, breathing, anchoring, and concentrated motion dominates. At 500 K, trimer and hexamer show the process of atomic exchange; however, the atomic exchange is not observed in the case of nonamer and decamer diffusion. The atomic exchange mechanism of Cu and Zr adatoms dominates at 700 K for all size clusters, except Ag adatoms, where Zr adatoms show a relatively more tendency. Separation and rejoining of the one and two adatoms (likely Zr adatom) are also witnessed at high temperature. The pop‐up of Ag adatoms also occurs in very short intervals over the remaining adatoms of clusters. Interestingly, during trimer diffusion, the adsorption of the Zr‐ or Cu‐adatom among the trimer cluster into the substitutional site is found. At 700 K, vacancy generation, filling of vacancies, and migration of vacancy, in the neighborhood of the adatoms cluster, also observed. Moreover, the rate of diffusion decreases with the size increase of the clusters and increases with the increase in temperature.
关键词： molecular dynamics,adatoms clusters,vacancy diffusion,surface diffusion
更新于2025-09-23 15:22:29
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Enhancement of linear and nonlinear optical absorption coefficients in spherical dome semiconductor nanoshells by surface plasmon resonances
摘要： Grandparents can play critical roles in the lives of children with intellectual and developmental disabilities and their families. However, current research and understanding around grandparent roles and experiences is limited. The purpose of this qualitative study was to examine the roles and experiences of grandparents supporting children with disabilities. In this article, the voices of grandparents with diverse experiences are presented. Key themes that emerged were the role of the grandparent, boundaries in roles and space, navigating family dynamics, and the general experiences of grandparenting. These findings have implications for the types of supports provided to grandparents and for practitioners working with families who have actively involved grandparents.
关键词： boundaries,grandparent,roles,family dynamics,experience
更新于2025-09-23 15:22:29
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Hot Carrier and Surface Recombination Dynamics in Layered InSe Crystals
摘要： Layered indium selenide (InSe) is a van der Waals solid that has emerged as a promising material for high-performance ultrathin solar cells. The optoelectronic parameters that are critical to photoconversion efficiencies, such as hot carrier lifetime and surface recombination velocity, are however largely unexplored in InSe. Here, these key photophysical properties of layered InSe are measured with femtosecond transient reflection spectroscopy. The hot carrier cooling process is found to occur through phonon scattering. The surface recombination velocity and ambipolar diffusion coefficient are extracted from fits to the pump energy-dependent transient reflection kinetics using a free carrier diffusion model. The extracted surface recombination velocity is approximately an order of magnitude larger than that for methylammonium lead-iodide perovskites, suggesting that surface recombination is a principal source of photocarrier loss in InSe. The extracted ambipolar diffusion coefficient is consistent with previously reported values of InSe carrier mobility.
关键词： transient reflection spectroscopy,hot carrier dynamics,Layered indium selenide,solar cell,van der Waals solid,surface recombination velocity,ambipolar diffusion coefficient
更新于2025-09-23 15:22:29
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ALMA-backed NIR high resolution integral field spectroscopy of the NUGA galaxy NGC 1433
摘要： Aims. We present the results of near-infrared (NIR) H- and K-band European Southern Observatory SINFONI integral field spectroscopy (IFS) of the Seyfert 2 galaxy NGC 1433. We investigate the central 500 pc of this nearby galaxy, concentrating on excitation conditions, morphology, and stellar content. NGC 1433 was selected from our extended NUGA(-south) sample, which was additionally observed with the Atacama Large Millimeter/submillimeter Array (ALMA). NGC 1433 is a ringed, spiral galaxy with a main stellar bar in roughly east–west direction (PA 94?) and a secondary bar in the nuclear region (PA 31?). Several dusty filaments are detected in the nuclear region with the Hubble Space Telescope. ALMA detects molecular CO emission coinciding with these filaments. The active galactic nucleus is not strong and the galaxy is also classified as a low-ionization emission-line region (LINER). Methods. The NIR is less affected by dust extinction than optical light and is sensitive to the mass-dominating stellar populations. SINFONI integral field spectroscopy combines NIR imaging and spectroscopy, allowing us to analyse several emission and absorption lines to investigate the stellar populations and ionization mechanisms over the 10'' × 10'' field of view (FOV). Results. We present emission and absorption line measurements in the central kpc of NGC 1433. We detect a narrow Balmer line and several H2 lines. We find that the stellar continuum peaks in the optical and NIR in the same position, indicating that there is no covering of the center by a nuclear dust lane. A strong velocity gradient is detected in all emission lines at that position. The position angle of this gradient is at 155? whereas the galactic rotation is at a position angle of 201?. Our measures of the molecular hydrogen lines, hydrogen recombination lines, and [Fe II] indicate that the excitation at the nucleus is caused by thermal excitation, i.e., shocks that can be associated with active galactic nuclei emission, supernovae, or outflows. The line ratios [Fe II]/Paβ and H2/Brγ show a Seyfert to LINER identification of the nucleus. We do not detect high star formation rates in our FOV. The stellar continuum is dominated by spectral signatures of red-giant M stars. The stellar line-of-sight velocity follows the galactic field whereas the light continuum follows the nuclear bar. Conclusions. The dynamical center of NGC 1433 coincides with the optical and NIR center of the galaxy and the black hole position. Within the central arcsecond, the molecular hydrogen and the 12CO(3?2) emissions – observed in the NIR and in the submillimeter with SINFONI and ALMA, respectively – are indicative for a nuclear outflow originating from the galaxy’s SMBH. A small circumnuclear disk cannot be fully excluded. Derived gravitational torques show that the nuclear bar is able to drive gas inward to scales where viscosity torques and dynamical friction become important. The black hole mass, derived using stellar velocity dispersion, is ～107 M☉.
关键词： galaxies: nuclei,galaxies: individual: NGC 1433,galaxies: active,infrared: galaxies,galaxies: ISM,galaxies: kinematics and dynamics
更新于2025-09-23 15:22:29
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Determining Crop Growth Dynamics in Sorghum Breeding Trials Through Remote and Proximal Sensing Technologies
摘要： With the advent of sophisticated spectral imaging the development of proximal and remote-sensing high-throughput field phenotyping platforms has become progressively feasible. Such platforms, combined with new innovative image-analysis and machine-learning tools, will likely become the benchmark in high-throughput plant phenotyping frameworks for determining plant responses at the leaf, plant and canopy level. At the University of Queensland, we have developed a cost-effective high-throughput phenotyping pipeline that harvests sensing data from plants utilising proximal sensors. Here, we describe the application of this software pipeline to analyse crop growth dynamics from (i) proximal sensors on-board a tractor-based phenotyping platform and (ii) cameras attached to small unmanned aerial vehicles. Specifically, we discuss the use of high-resolution characterization of time-sequence red-edge data obtained from both sensing platforms to derive estimates for dynamic growth parameters in sorghum breeding trials. Although some temporal bias existed between the two platforms the relationships at spatial peak canopy (R2 = 0.71) and plot level (R2 = 0.89) were strong. Application of these technologies across breeding plots will enhance phenotyping capabilities and hence the ability to discriminate among responses of genotypes across different environments.
关键词： growth dynamics,field-scale,genomics,phenomics,Traits
更新于2025-09-23 15:22:29
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Integral Characteristics of Wave Packets in the Problem of the Evolution of A Wave Function on A One-Dimensional Lattice
摘要： We consider the quantum dynamics of charge transfer on a lattice in the tight-binding approximation and analytically calculate the integral characteristics of the wave packet propagating along the lattice. We focus on calculating the mean and root-mean-square displacements. We also obtain expressions for higher-order moments as series for squares of Bessel functions, which might be independently interesting.
关键词： moments of distribution function,quantum dynamics,tight-binding approximation
更新于2025-09-23 15:22:29