4,149 research outputs found
Essays on Contests Design with Stochastic Entry and Information Disclosure
Ph.DDOCTOR OF PHILOSOPH
Instantaneous Bethe-Salpeter Equation and Its Exact Solution
We present an approach to solve a Bethe-Salpeter (BS) equation exactly
without any approximation if the kernel of the BS equation exactly is
instantaneous, and take positronium as an example to illustrate the general
features of the solutions. As a middle stage, a set of coupled and
self-consistent integration equations for a few scalar functions can be
equivalently derived from the BS equation always, which are solvable
accurately. For positronium, precise corrections to those of the Schr\"odinger
equation in order (relative velocity) in eigenfunctions, in order in
eigenvalues, and the possible mixing, such as that between () and
() components in () states as well, are
determined quantitatively. Moreover, we also point out that there is a
problematic step in the classical derivation which was proposed first by E.E.
Salpeter. Finally, we emphasize that for the effective theories (such as NRQED
and NRQCD etc) we should pay great attention on the corrections indicated by
the exact solutions.Comment: 4 pages, replace for shortening the manuscrip
Association between mild thyroid dysfunction and clinical outcome in acute coronary syndrome undergoing percutaneous coronary intervention
Background: Thyroid hormones profoundly influence the cardiovascular system, but the effects of mild thyroid dysfunction on the clinical outcome of acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI) are not well defined. This study aimed to determine the effect of mild thyroid dysfunction on 12-month prognosis in ACS patients undergoing PCI.
Methods: In this prospective cohort study with a 12-month follow-up, 1560 individuals were divided into four groups based on thyroid hormone levels upon admission: euthyroidism (used as a reference group), subclinical hypothyroidism, subclinical hyperthyroidism, and low triiodothyronine syndrome (low T3 syndrome). The outcomes measured were all-cause mortality, cardiac mortality, nonfatal reinfarction, and unplanned repeat revascularization.
Results: In this study, the prevalence of mild thyroid dysfunction was 10.8%. Multivariate analysis showed that low T3 syndrome, but not subclinical hypothyroidism or subclinical hyperthyroidism, was associated with a higher rate of all-cause (HR 2.553, 95% CI 1.093–5.964, p = 0.030) and cardiac mortality (HR 2.594, 95% CI 1.026–6.559, p = 0.034), compared with the euthyroidism group.
Conclusions: Mild thyroid dysfunction was frequent in patients with ACS undergoing PCI. Low T3 syndrome was the predominant feature and was associated with 12-month adverse outcomes in these patients
Design and Control of the "TransBoat": A Transformable Unmanned Surface Vehicle for Overwater Construction
This paper presents the TransBoat, a novel omnidirectional unmanned surface
vehicle (USV) with a magnetbased docking system for overwater construction with
wave disturbances. This is the first such USV that can build overwater
structures by transporting modules. The TransBoat incorporates two features
designed to reject wave disturbances. First, the TransBoat's expandable body
structure can actively transform from a mono-hull into a multi-hull for
stabilization in turbulent environments by extending its four outrigger hulls.
Second, a real-time nonlinear model predictive control (NMPC) scheme is
proposed for all shapes of the TransBoat to enhance its maneuverability and
resist disturbance to its movement, based on a nonlinear dynamic model. An
experimental approach is proposed to identify the parameters of the dynamic
model, and a subsequent trajectory tracking test validates the dynamics, NMPC
controller and system mobility. Further, docking experiments identify improved
performance in the expanded form of the TransBoat compared with the contracted
form, including an increased success rate (of ~ 10%) and reduced docking time
(of ~ 40 s on average). Finally, a bridge construction test verifies our system
design and the NMPC control method
NuScenes-QA: A Multi-modal Visual Question Answering Benchmark for Autonomous Driving Scenario
We introduce a novel visual question answering (VQA) task in the context of
autonomous driving, aiming to answer natural language questions based on
street-view clues. Compared to traditional VQA tasks, VQA in autonomous driving
scenario presents more challenges. Firstly, the raw visual data are
multi-modal, including images and point clouds captured by camera and LiDAR,
respectively. Secondly, the data are multi-frame due to the continuous,
real-time acquisition. Thirdly, the outdoor scenes exhibit both moving
foreground and static background. Existing VQA benchmarks fail to adequately
address these complexities. To bridge this gap, we propose NuScenes-QA, the
first benchmark for VQA in the autonomous driving scenario, encompassing 34K
visual scenes and 460K question-answer pairs. Specifically, we leverage
existing 3D detection annotations to generate scene graphs and design question
templates manually. Subsequently, the question-answer pairs are generated
programmatically based on these templates. Comprehensive statistics prove that
our NuScenes-QA is a balanced large-scale benchmark with diverse question
formats. Built upon it, we develop a series of baselines that employ advanced
3D detection and VQA techniques. Our extensive experiments highlight the
challenges posed by this new task. Codes and dataset are available at
https://github.com/qiantianwen/NuScenes-QA
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