362 research outputs found
Study of Primary and Internal Resonance on 3D Free-Free Double-Section Beam
This work investigates the primary resonance and internal resonance of a double-section beam with cubic nonlinearities. This model can be applied in a wide range of engineering problems, such as rocket and missile structures. Even space technology has been developed for decades; several nonlinear properties deserve further study, especially, for the internal resonance. The method of multiple scales (a perturbation technique) is employed to analyze this nonlinear problem. This study focuses on finding the forcing conditions of this 3D double-section beam to trigger the often-ignored internal resonance or prime resonance in rocket structures. A primary resonance is found on a uniform free-free beam at certain flight speed. The three-to-one internal resonance of the double-section beam occurs within the first and the second modes in the diameter ratio of 1/0.75 with the length ratio of 0.33 or 0.51. The semi-analytical results are verified by the time marching numerical method
Lepton pair photoproduction in peripheral relativistic heavy-ion collisions
We study the lepton pair photoproduction in peripheral heavy-ion collisions
based on the formalism in our previous work [Phys. Rev. D 104, 056011 (2021)].
We present the numerical results for the distributions of the transverse
momentum, azimuthal angle and invariant mass for and
pairs as functions of the impact parameter and other kinematic
variables in Au+Au collisions. Our calculation incorporates the information on
the transverse momentum and polarization of photons which is essential to
describe the experimental data. We observe a broadening effect in the
transverse momentum for lepton pairs with and without smear effects. We also
observe a significant enhancement in the distribution of for
pairs. Our results provide a baseline for future studies of
other higher order corrections beyond Born approximation and medium effects in
the lepton pair production.Comment: 19 pages, 10 figure
Photoproduction of in peripheral isobar collisions
We investigate the photoproduction of di-electrons in peripheral collisions
of and
at 200 GeV. With the charge and
mass density distributions given by the calculation of the density functional
theory, we calculate the spectra of transverse momentum, invariant mass and
azimuthal angle for di-electrons at 40-80\% centrality. The ratios of these
spectra in Ru+Ru collisions over to Zr+Zr collisions are shown to be smaller
than (the ratio of for Ru and Zr) at low transverse
momentum. The deviation arises from the different mass and charge density
distributions in Ru and Zr. So the photoproduction of di-leptons in isobar
collisions may provide a new way to probe the nuclear structure.Comment: 17 pages, 6 figure
FishMOT: A Simple and Effective Method for Fish Tracking Based on IoU Matching
The tracking of various fish species plays a profoundly significant role in
understanding the behavior of individual fish and their groups. Present
tracking methods suffer from issues of low accuracy or poor robustness. In
order to address these concerns, this paper proposes a novel tracking approach,
named FishMOT (Fish Multiple Object Tracking). This method combines object
detection techniques with the IoU matching algorithm, thereby achieving
efficient, precise, and robust fish detection and tracking. Diverging from
other approaches, this method eliminates the need for multiple feature
extractions and identity assignments for each individual, instead directly
utilizing the output results of the detector for tracking, thereby
significantly reducing computational time and storage space. Furthermore, this
method imposes minimal requirements on factors such as video quality and
variations in individual appearance. As long as the detector can accurately
locate and identify fish, effective tracking can be achieved. This approach
enhances robustness and generalizability. Moreover, the algorithm employed in
this method addresses the issue of missed detections without relying on complex
feature matching or graph optimization algorithms. This contributes to improved
accuracy and reliability. Experimental trials were conducted in the open-source
video dataset provided by idtracker.ai, and comparisons were made with
state-of-the-art detector-based multi-object tracking methods. Additionally,
comparisons were made with idtracker.ai and TRex, two tools that demonstrate
exceptional performance in the field of animal tracking. The experimental
results demonstrate that the proposed method outperforms other approaches in
various evaluation metrics, exhibiting faster speed and lower memory
requirements. The source codes and pre-trained models are available at:
https://github.com/gakkistar/FishMO
New Transitional Fleas from China Highlighting Diversity of Early Cretaceous Ectoparasitic Insects
SummaryFleas are a group of highly specialized blood-feeding ectoparasites whose early evolutionary history is poorly known [1, 2]. Although several recent discoveries have shed new light on the origin of the group [3, 4], a considerable gap exists between stem fleas and crown fleas. Here we report a new transitional flea, Saurophthirus exquisitus sp. nov., assigned to a new family Saurophthiridae fam. nov., from the Lower Cretaceous Yixian Formation of northeastern China. Saurophthirids are more similar to crown fleas than other stem fleas in having a relatively small body size, relatively short and slender piercing-sucking stylet mouthparts, comparably short and compact antennae, rows of short and stiff bristles on the thorax, and highly elongated legs. The new finding greatly improves our understanding of the morphological transition to the highly specialized body plan of extant fleas. However, saurophthirids also display several features unknown in other fleas, and some of these features are suggestive of a possible ectoparasitic relationship to contemporaneous pterosaurs, though other possibilities exist. The new fossils, in conjunction with previous discoveries, highlight a broad diversity of ectoparasitic insects in the mid-Mesozoic
API : an index for quantifying a scholar's academic potential
In the context of big scholarly data, various metrics and indicators have been widely applied to evaluate the impact of scholars from different perspectives, such as publication counts, citations, -index, and their variants. However, these indicators have limited capacity in characterizing prospective impacts or achievements of scholars. To solve this problem, we propose the Academic Potential Index (API) to quantify scholar's academic potential. Furthermore, an algorithm is devised to calculate the value of API. It should be noted that API is a dynamic index throughout scholar's academic career. By applying API to rank scholars, we can identify scholars who show their academic potentials during the early academic careers. With extensive experiments conducted based on the Microsoft Academic Graph dataset, it can be found that the proposed index evaluates scholars' academic potentials effectively and captures the variation tendency of their academic impacts. Besides, we also apply this index to identify rising stars in academia. Experimental results show that the proposed API can achieve superior performance in identifying potential scholars compared with three baseline methods. © 2019 IEEE
Enhancement of thermoelectric figure-of-merit at low temperatures by titanium substitution for hafnium in n-type half-Heuslers Hf0.75−xTixZr0.25NiSn0.99Sb0.01
The effect of titanium (Ti) substitution for hafnium (Hf) on thermoelectric properties of (Hf, Zr)-based n-type half-Heuslers: Hf[subscript 0.75−x]Ti[subscript x]Zr[subscript 0.25]NiSn[subscript 0.99]Sb[subscript 0.01], has been studied. The samples are made by arc melting followed by ball milling and hot pressing via the nanostructuring approach. A peak thermoelectric figure-of-merit (ZT) of ∼1.0 is achieved at 500 °C in samples with a composition of Hf[subscript 0.5]Zr[subscript 0.25]Ti[subscript 0.25]NiSn[subscript 0.99]Sb[subscript 0.01] due to a slight increase in carrier concentration and also a lower thermal conductivity caused by Ti. The ZT values below 500 °C of hot pressed Hf[subscript 0.5]Zr[subscript 0.25]Ti[subscript 0.25]NiSn[subscript 0.99]Sb[subscript 0.01] samples are significantly higher than those of the same way prepared Hf[subscript 0.75]Zr[subscript 0.25]NiSn[subscript 0.99]Sb[subscript 0.01] samples at each temperature, which are very much desired for mid-range temperature applications such as waste heat recovery in automobiles.United States. Department of Energy. Office of Science. Solid-State Solar Thermal Energy Conversion Center (Award DE-SC0001299/DE-FG02–09ER46577
Applications of ionic liquids in starch chemistry : a review
Recently, the utilization of starch to replace synthetic polymers for the manufacture of green materials has gained extensive interest, due to its renewability, biodegradability, abundance and low cost. On the other hand, ionic liquids (ILs) have been widely recognized as promising “green solvents” to replace volatile organic solvents for polysaccharide processing. Over the past few years, ILs have been increasingly demonstrated to serve as excellent media for the dissolution, plasticization and derivatization of starch. This allows the synthesis of chemically modified starches with high degree of substitution (DS) and the development of various starch-based materials such as thermoplastic starch, composite films, solid polymer electrolytes, nanoparticles and drug carriers. The main objective of this review is to present an overview of the roles of ILs in starch dissolution, gelatinization, modification and plasticization, and their industrial applications. Moreover, this review is intended to provide a comprehensive understanding of the mechanisms behind the IL-processing of starch and to provide insights into the rational development of novel starch-based materials with ILs
A new perspective of hypothalamic disease: Shapiro's syndrome
Shapiro's syndrome (SS) is characterized by spontaneous periodic hypothermia. It occurs to patients regardless of age or sex. To date, <60 cases have been reported worldwide. Current knowledge of the disease is limited to clinical feature since the pathogenesis and etiology are still controversial. In this review, the clinical characteristics, pathological mechanism, and possible etiology of the syndrome were reviewed to improve the clinical understanding of the disease
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