2,749 research outputs found
High-lift system of the competition model aircraft
Bakalářská práce je zaměřena na sestavení přehledu vztlakové mechanizace, a to jak na náběžných, tak i odtokových hranách, používané na modelech letadel a bezpilotních prostředcích. Stručně vysvětluje jejich princip a funkce. Popisuje postup výpočtu návrhového letového režimu pro soutěžní letoun podle specifikací soutěže Air Cargo Challenge.This Bachelor thesis is focused on compiling a summary of lift mechanization, at both the leading and the trailing edges used on plane models and unmanned means of transport. It briefly explains their principles and functions. It describes the method of calculation of the flight mode design of the competing aircraft according to the specifications of the Air Cargo Challenge competition.
Sanitation installation in historic building
Diplomová práce se zabývá zdravotně technickými instalacemi v historické budově. Teoretická část se po analýze tématu věnuje problematice odvádění odpadních vod z objektu a podzemních podlaží. Dále se jsou zpracovány teoretická řešení zdravotně technických instalací a zpracovány varianty. Vhodnější z variant je nakonec dopracována v podrobnostech prováděcího projektu.This Master’s thesis deals with sanitation installation in historic building. The theoretical part of the topic analysis deals with the issue waste water discharge from the building and ground floor. Furthermore, the theoretical solutions are processed sanitation installation and variants of it. Preferable variant is finalized the details of the implementation of the project.
Trapping of null geodesics in slowly rotating spacetimes
Extremely compact objects containing a region of trapped null geodesics could
be of astrophysical relevance due to trapping of neutrinos with consequent
impact on cooling processes or trapping of gravitational waves. These objects
have previously been studied under the assumption of spherical symmetry. In the
present paper, we consider a simple generalization by studying trapping of null
geodesics in the framework of the Hartle-Thorne slow-rotation approximation
taken to first order in the angular velocity, and considering a uniform-density
object with uniform emissivity for the null geodesics. We calculate effective
potentials and escape cones for the null geodesics and how they depend on the
parameters of the spacetimes, and also calculate the "local" and "global"
coefficients of efficiency for the trapping. We demonstrate that due to the
rotation the trapping efficiency is different for co-rotating and retrograde
null geodesics, and that trapping can occur even for , contrary to
what happens in the absence of rotation
Human extraintestinal pathogenic Escherichia coli strains differ in prevalence of virulence factors, phylogroups, and bacteriocin determinants
Table S4. Differences in the distribution of virulence factors, E. coli phylogroups, bacteriocin production, and bacteriocin determinants between subgroups of ExPEC strains and fecal strains. (XLSX 14 kb
The MRS UAV System: Pushing the Frontiers of Reproducible Research, Real-world Deployment, and Education with Autonomous Unmanned Aerial Vehicles
We present a multirotor Unmanned Aerial Vehicle control (UAV) and estimation
system for supporting replicable research through realistic simulations and
real-world experiments. We propose a unique multi-frame localization paradigm
for estimating the states of a UAV in various frames of reference using
multiple sensors simultaneously. The system enables complex missions in GNSS
and GNSS-denied environments, including outdoor-indoor transitions and the
execution of redundant estimators for backing up unreliable localization
sources. Two feedback control designs are presented: one for precise and
aggressive maneuvers, and the other for stable and smooth flight with a noisy
state estimate. The proposed control and estimation pipeline are constructed
without using the Euler/Tait-Bryan angle representation of orientation in 3D.
Instead, we rely on rotation matrices and a novel heading-based convention to
represent the one free rotational degree-of-freedom in 3D of a standard
multirotor helicopter. We provide an actively maintained and well-documented
open-source implementation, including realistic simulation of UAV, sensors, and
localization systems. The proposed system is the product of years of applied
research on multi-robot systems, aerial swarms, aerial manipulation, motion
planning, and remote sensing. All our results have been supported by real-world
system deployment that shaped the system into the form presented here. In
addition, the system was utilized during the participation of our team from the
CTU in Prague in the prestigious MBZIRC 2017 and 2020 robotics competitions,
and also in the DARPA SubT challenge. Each time, our team was able to secure
top places among the best competitors from all over the world. On each
occasion, the challenges has motivated the team to improve the system and to
gain a great amount of high-quality experience within tight deadlines.Comment: 28 pages, 20 figures, submitted to Journal of Intelligent & Robotic
Systems (JINT), for the provided open-source software see
http://github.com/ctu-mr
On the kinematic age of brown dwarfs: Radial velocities and space motions of 43 nearby L dwarfs
We present radial velocity measurements of a sample of L0-L8 dwarfs observed
with VLT/UVES and Keck/HIRES. We combine these measurements with distance and
proper motion from the literature to determine space motions for 43 of our
targets. We identify nine candidate members of young moving groups, which have
ages of 50-600 Myr according to their space motion. From the total velocity
dispersion of the 43 L dwarfs, we calculate a kinematic age of ~5 Gyr for our
sample. This age is significantly higher than the ~3 Gyr age known for late M
dwarfs in the solar neighbourhood. We find that the distributions of the U and
V velocity components of our sample are clearly non-Gaussian, placing the age
estimate inferred from the full space motion vector into question. The
W-component exhibits a distribution more consistent with a normal distribution,
and from W alone we derive an age of ~3 Gyr, which is the same age found for
late-M dwarf samples. Our brightness-limited sample is probably contaminated by
a number of outliers that predominantly bias the U and V velocity components.
The origin of the outliers remain unclear, but we suggest that these brown
dwarfs may have gained their high velocities by means of ejection from multiple
systems during their formation.Comment: 8 pages, accepted for publication in A&
Dynamical Mass Constraints on Low-Mass Pre-Main-Sequence Stellar Evolutionary Tracks: An Eclipsing Binary in Orion with a 1.0 Msun Primary and an 0.7 Msun Secondary
We report the discovery of a double-lined, spectroscopic, eclipsing binary in
the Orion star-forming region. We analyze the system spectroscopically and
photometrically to empirically determine precise, distance-independent masses,
radii, effective temperatures, and luminosities for both components. The
measured masses for the primary and secondary, accurate to ~1%, are 1.01 Msun
and 0.73 Msun, respectively; thus the primary is a definitive pre-main-sequence
solar analog, and the secondary is the lowest-mass star yet discovered among
pre-main-sequence eclipsing binary systems. We use these fundamental
measurements to test the predictions of pre-main-sequence stellar evolutionary
tracks. None of the models we examined correctly predict the masses of the two
components simultaneously, and we implicate differences between the theoretical
and empirical effective temperature scales for this failing. All of the models
predict the observed slope of the mass-radius relationship reasonably well,
though the observations tend to favor models with low convection efficiencies.
Indeed, considering our newly determined mass measurements together with other
dynamical mass measurements of pre-main-sequence stars in the literature, as
well as measurements of Li abundances in these stars, we show that the data
strongly favor evolutionary models with inefficient convection in the stellar
interior, even though such models cannot reproduce the properties of the
present-day Sun.Comment: Accepted by Ap
New H2 collision-induced absorption and NH3 opacity and the spectra of the coolest brown dwarfs
We present new cloudy and cloudless model atmospheres for brown dwarfs using
recent ab initio calculations of the line list of ammonia (NH3) and of the
collision-induced absorption of molecular hydrogen (H2). We compare the new
synthetic spectra with models based on an earlier description of the H2 and NH3
opacities. We find a significant improvement in fitting the nearly complete
spectral energy distribution of the T7p dwarf Gliese 570D and in near infrared
color-magnitude diagrams of field brown dwarfs. We apply these new models to
the identification of NH3 absorption in the H band peak of very late T dwarfs
and the new Y dwarfs and discuss the observed trend in the NH3-H spectral
index. The new NH3 line list also allows a detailed study of the medium
resolution spectrum of the T9/T10 dwarf UGPS J072227.51-054031.2 where we
identify several specific features caused by NH3.Comment: 37 pages, 13 figures. Accepted for publication in the Astrophysical
MRS Drone: A Modular Platform for Real-World Deployment of Aerial Multi-Robot Systems
This paper presents a modular autonomous Unmanned Aerial Vehicle (UAV)
platform called the Multi-robot Systems (MRS) Drone that can be used in a large
range of indoor and outdoor applications. The MRS Drone features unique
modularity with respect to changes in actuators, frames, and sensory
configuration. As the name suggests, the platform is specially tailored for
deployment within a MRS group. The MRS Drone contributes to the
state-of-the-art of UAV platforms by allowing smooth real-world deployment of
multiple aerial robots, as well as by outperforming other platforms with its
modularity. For real-world multi-robot deployment in various applications, the
platform is easy to both assemble and modify. Moreover, it is accompanied by a
realistic simulator to enable safe pre-flight testing and a smooth transition
to complex real-world experiments. In this manuscript, we present mechanical
and electrical designs, software architecture, and technical specifications to
build a fully autonomous multi UAV system. Finally, we demonstrate the full
capabilities and the unique modularity of the MRS Drone in various real-world
applications that required a diverse range of platform configurations.Comment: 49 pages, 39 figures, accepted for publication to the Journal of
Intelligent & Robotic System
Interactions between visual and semantic processing during object recognition revealed by modulatory effects of age of acquisition
The age of acquisition (AoA) of objects and their names is a powerful determinant of processing speed in adulthood, with early-acquired objects being recognized and named faster than late-acquired objects. Previous research using fMRI (Ellis et al., 2006. Traces of vocabulary acquisition in the brain: evidence from covert object naming. NeuroImage 33, 958–968) found that AoA modulated the strength of BOLD responses in both occipital and left anterior temporal cortex during object naming. We used magnetoencephalography (MEG) to explore in more detail the nature of the influence of AoA on activity in those two regions. Covert object naming recruited a network within the left hemisphere that is familiar from previous research, including visual, left occipito-temporal, anterior temporal and inferior frontal regions. Region of interest (ROI) analyses found that occipital cortex generated a rapid evoked response (~ 75–200 ms at 0–40 Hz) that peaked at 95 ms but was not modulated by AoA. That response was followed by a complex of later occipital responses that extended from ~ 300 to 850 ms and were stronger to early- than late-acquired items from ~ 325 to 675 ms at 10–20 Hz in the induced rather than the evoked component. Left anterior temporal cortex showed an evoked response that occurred significantly later than the first occipital response (~ 100–400 ms at 0–10 Hz with a peak at 191 ms) and was stronger to early- than late-acquired items from ~ 100 to 300 ms at 2–12 Hz. A later anterior temporal response from ~ 550 to 1050 ms at 5–20 Hz was not modulated by AoA. The results indicate that the initial analysis of object forms in visual cortex is not influenced by AoA. A fastforward sweep of activation from occipital and left anterior temporal cortex then results in stronger activation of semantic representations for early- than late-acquired objects. Top-down re-activation of occipital cortex by semantic representations is then greater for early than late acquired objects resulting in delayed modulation of the visual response
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