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Dirichlet Process Clustering-based Radio SLAM with Arbitrarily-Shaped Reflectors
No full textThis paper proposes a Dirichlet process (DP)-based radio simultaneous localization and mapping (SLAM) algorithm enabling mapping arbitrary structures (ASs) as well as the standard point landmarks. The ASs cannot be characterized by a low-dimensional state, in contrast to the standard point landmarks, leading to incorrect mapping results in the existing radio SLAM methods. To tackle the incorrect mapping issue, we develop a DP-based data association method, where the landmarks are maintained by the clusters, and each birth point by the measurement is assigned to the existing or a new cluster. Compared to the well-known state-of-the-art method, we evaluate the performance of the proposed algorithm under the scenario with multiple landmarks deployed. This validation represents that radio SLAM is possible in an environment where objects of ASs exist through the proposed method
Discrete spectrum of zero order pseudodifferential operators.
Full text linkWe study the rate of convergence of eigenvalues to the endpoints of essential spectrum for zero order pseudodifferential operators on a compact manifold
A rich hydrocarbon chemistry and high C to O ratio in the inner disk around a very low-mass star
No full textCarbon is an essential element for life but how much can be delivered to young planets is still an open question. The chemical characterization of planet-forming disks is a crucial step in our understanding of the diversity and habitability of exoplanets. Very low-mass stars (less than 0.2 M ⊙) are interesting targets because they host a rich population of terrestrial planets. Here we present the James Webb Space Telescope detection of abundant hydrocarbons in the disk of a very low-mass star obtained as part of the Mid-InfraRed Instrument mid-INfrared Disk Survey (MINDS). In addition to very strong and broad emission from C2H2 and its 13C12CH2 isotopologue, C4H2, benzene and possibly CH4 are identified, but water, polycyclic aromatic hydrocarbons and silicate features are weak or absent. The lack of small silicate grains indicates that we can look deep down into this disk. These detections testify to an active warm hydrocarbon chemistry with a high C/O ratio larger than unity in the inner 0.1 astronomical units (AU) of this disk, perhaps due to destruction of carbonaceous grains. The exceptionally high C2H2/CO2 and C2H2/H2O column density ratios indicate that oxygen is locked up in icy pebbles and planetesimals outside the water iceline. This, in turn, will have important consequences for the composition of forming exoplanets
Ascending Aortic Endograft and Thoracic Aortic Deformation After Ascending Thoracic Endovascular Aortic Repair
No full textPurpose: We aim to quantify multiaxial cardiac pulsatility-induced deformation of the thoracic aorta after ascending thoracic endovascular aortic repair (TEVAR) as a part of the GORE ARISE Early Feasibility Study. Materials and Methods: Fifteen patients (7 females and 8 males, age 73\ub19 years) with ascending TEVAR underwent computed tomography angiography with retrospective cardiac gating. Geometric modeling of the thoracic aorta was performed; geometric features including axial length, effective diameter, and centerline, inner surface, and outer surface curvatures were quantified for systole and diastole; and pulsatile deformations were calculated for the ascending aorta, arch, and descending aorta. Results: From diastole to systole, the ascending endograft exhibited straightening of the centerline (0.224\ub10.039 to 0.217\ub10.039 cm−1, p<0.05) and outer surface (0.181\ub10.028 to 0.177\ub10.029 cm−1, p<0.05) curvatures. No significant changes were observed for inner surface curvature, diameter, or axial length in the ascending endograft. The aortic arch did not exhibit any significant deformation in axial length, diameter, or curvature. The descending aorta exhibited small but significant expansion of effective diameter from 2.59\ub10.46 to 2.63\ub10.44 cm (p<0.05). Conclusion: Compared with the native ascending aorta (from prior literature), ascending TEVAR damps axial and bending pulsatile deformations of the ascending aorta similar to how descending TEVAR damps descending aortic deformations, while diametric deformations are damped to a greater extent. Downstream diametric and bending pulsatility of the native descending aorta was muted compared with that in patients without ascending TEVAR (from prior literature). Deformation data from this study can be used to evaluate the mechanical durability of ascending aortic devices and inform physicians about the downstream effects of ascending TEVAR to help predict remodeling and guide future interventional strategies. Clinical Impact: This study quantified local deformations of both stented ascending and native descending aortas to reveal the biomechanical impact of ascending TEVAR on the entire thoracic aorta, and reported that the ascending TEVAR muted cardiac-induced deformation of the stented ascending aorta and native descending aorta. Understanding of in vivo deformations of the stented ascending aorta, aortic arch and descending aorta can inform physicians about the downstream effects of ascending TEVAR. Notable reduction of compliance may lead to cardiac remodeling and long-term systemic complications. This is the first report which included dedicated deformation data regarding ascending aortic endograft from clinical trial
Multiscale modeling reveals aluminum nitride as an efficient propane dehydrogenation catalyst
No full textNonoxidative propane dehydrogenation (PDH) is a promising route to meet the steadily increasing demand for propylene, an important building block in the chemical industry. Wurtzite group-IIIA metal nitrides are potential catalysts for PDH with high chemical, thermal, and mechanical stability alongside inherent Lewis acid-base properties that can activate the C-H bond of alkanes. Herein, we investigate the catalytic behavior of pristine (AlN) and gallium-doped (Ga/AlN) aluminum nitride for PDH via concerted and various stepwise mechanisms using density functional theory (DFT) calculations and microkinetic modeling (MKM). The reaction profiles investigated with DFT calculations are used in MKM, which reveals that the stepwise mechanisms produce >99% of propylene on both AlN and Ga/AlN. AlN has approximately one order of magnitude higher activity than Ga/AlN due to lower barriers along the dominant PDH reaction pathway. In summary, we propose the potential application of AlN as an efficient dehydrogenation catalyst for the conversion of light alkanes into valuable olefins. In addition, we show that multiscale simulations are essential to evaluate the catalytic behavior of complex alkane conversion reaction networks and obtain activity trends for dehydrogenation catalysts
Value creation and destruction involving multiple public service organizations: a focus on frontline employees
Full text linkUsing six focus groups with frontline employees within the Swedish sick-leave service, this article explores the co-creation/destruction of value. The article both adheres to and questions the public service logic by utilizing an empirical case in which frontline staff represents not one, but multiple, public service organizations. Moreover, as value creation/destruction is not restricted to one beneficiary, and several beneficiaries can be tied to one single service, the research builds upon this notion and distinguishes between four levels of value creation/destruction
Increasing the Ionization Energy Offset to Increase the Quantum Efficiency in Non-Fullerene Acceptor-Based Organic Solar Cells: How Far Can We Go?
No full textMolecular engineering of organic semiconductors provides a virtually unlimited number of possible structures, yet only a handful of combinations lead to state-of-the-art efficiencies in photovoltaic applications. Thus, design rules that guide material development are needed. One such design principle is that in a bulk heterojunction consisting of an electron donor and lower bandgap acceptor an offset (Delta IE) of at least 0.45 eV is required between both materials ionization energies to overcome energy level bending at the donor-acceptor interface, in turn maximizing the charge separation yield and the cell\u27s internal quantum efficiency. The present work studies energy losses associated with Delta IE and, based on 24 blends, finds that losses are minimal up to a Delta IE of 0.6 eV. Electroluminescence spectroscopy shows that low energy losses are achieved when the charge transfer state energy (E-CT) is similar to the acceptor\u27s optical bandgap (E-g(A)). Further Delta IE increase lowers E-CT with respect to E-g(A), thus decreasing V-OC. Within that 0.45-0.6 eV Delta IE sweet range, the fill factor FF, hence the power conversion efficiency, increases only marginally as the FF is often already close to maximal for Delta IE = 0.45 eV. The results are extended to 76 binary and ternary blends
The extended predicative Mahlo universe in Martin-Lof type theory
Full text linkThis paper addresses the long-standing question of the predicativity of the Mahlo universe. A solution, called the extended predicative Mahlo universe, has been proposed by Kahle and Setzer in the context of explicit mathematics. It makes use of the collection of untyped terms (denoting partial functions) which are directly available in explicit mathematics but not in Martin-Lof type theory. In this paper, we overcome the obstacle of not having direct access to untyped terms in Martin-Lof type theory by formalizing explicit mathematics with an extended predicative Mahlo universe in Martin-Lof type theory with certain indexed inductive-recursive definitions. In this way, we can relate the predicativity question to the fundamental semantics of Martin-Lof type theory in terms of computation to canonical form. As a result, we get the first extended predicative definition of a Mahlo universe in Martin-Lof type theory. To this end, we first define an external variant of Kahle and Setzer\u27s internal extended predicative universe in explicit mathematics. This is then formalized in Martin-Lof type theory, where it becomes an internal extended predicative Mahlo universe. Although we make use of indexed inductive-recursive definitions that go beyond the type theory of indexed inductive-recursive definitions defined in previous work by the authors, we argue that they are constructive and predicative in Martin-Lof\u27s sense. The model construction has been type-checked in the proof assistant Agda
Methane emissions from industrial activities using drones
Full text linkInnovative drone-based methods have been developed to map and quantify methane leakages from various industrial activities, such as refineries, Liquified Natural Gas (LNG) terminals, landfills, and water treatment facilities. These methods use a high-speed, high-sensitivity laser sensor and were validated through controlled gas releases. They were also compared to a ground-based infrared absorption-based technique. This initiative is supported by the Swedish Governmental Agency for Innovation Systems (Vinnova) and aligns with UN Sustainable Development Goals 9, 11, and 13. The goal is to reduce methane emissions significantly, aiding Sweden in achieving net-zero greenhouse gas emissions by 2045. Accurate measurements enable effective, targeted, and trackable measures to minimize emissions, resulting in a rapid positive climate impact. The project has led to the development of two distinct drone-based methods: the wall approach and the tracer approach. The wall approach measures gas concentrations across the entire cross-section of the plume, whereas the tracer approach measures the ratio of leaking gas to source gas. Depending on the source\u27s size, one approach may be preferred over the other, with the tracer method being more suitable for point sources and the wall approach for larger sources. The custom-designed drone in this project, provided and operated by Gerdes Solution. is equipped with a high-sensitivity laser sensor and has a flight duration of about 12 minutes while carrying a 3 kg payload. This limitation presents a challenge when conducting wall measurements, which require approximately 25 minutes of flight time for the studied sources. Due to the drone\u27s limited flight time, it necessitates landing and battery replacement, which complicates the process and limits the number of repeat measurements. In future endeavors, employing a drone with a longer flight duration would be advantageous. In total, the study detected about 220 kg/h of methane emissions and 3 kg/h of nitrous oxide emissions, equivalent to an emission rate of about 7 tons/h of carbon dioxide. The emissions were dominated by the water treatment plant and landfills, with relatively little coming from the refinery and LNG plant. However, the wall measurements in thus study serve as demonstrations of how the technique can be used and do not provide a comprehensive picture of the actual emissions from the individual sites; this would require more statistical data in terms of repeat measurements and measurement days. It is shown that drone measurements using the new high sensitivity laser is a valuable tool for mapping methane concentrations from various types of industrial sources, which are challenging to investigate today due to diffuse emissions, large dimensions, and complex geometries. The validation studies show that both the wall approach and controlled tracer releases can be used to quantify emissions, achieving an accuracy of up to 10 % for a simple, single, source. However, in the real measurement situation, the wall approach may be difficult to execute due to practical challenges like flying restrictions and the need for spatially dense data that can be interpolated to a homogenous grid and repeated measurements. In several cases, when the drone had to fly relatively close to the plumes, downwind of large buildings in complex and turbulent wind fields, the wall approach yielded large variability in the resulting flux. It is hence evident that the wall approach requires a thorough understanding of the measurement situation, and that repeated measurements are needed, at different distances from the source and in varying wind directions. The tracer approach was therefore preferred choice for obtaining emission rates in this study, although it is challenging to carry out representative tracer releases for larger sources and for cases when the measurements are performed near to the source, and in this case the wall approach is preferred. It was also shown that the drone-based tracer approach is advantageous to the ground based since it is then easier to capture the full plume