2,723 research outputs found
The Manin-Peyre conjecture for three del Pezzo surfaces
The Manin-Peyre conjecture is established for a split singular quintic del
Pezzo surface with singularity type and two split singular
quartic del Pezzo surfaces with singularity types
and respectively. We use a unified and different slightly method
from the previous and improve their error terms. Our method is general and can
handle most of singular del Pezzo surfaces of degree .Comment: 38 pages. minor changes on Table 1. Comments welcome
Feasibility of 3D tracking and adaptation of VMAT based on VMAT-CT
Background: Local computed tomography (CT) reconstruction is achievable with portal images acquired during volumetric-modulated arc therapy (VMAT) delivery and was named as VMAT-CT. However, the application of VMAT-CT is limited because it has limited field of view and no density information. In addition, the new generation of multi-leaf collimator with faster speed and various collimator angles used in patientsā plans could cause more artifacts in VMAT-CT. The goal of this study was to extend VMAT-CT concept, generate complete three-dimensional (3D) CT images, calculate new 3D dose, track and adapt VMAT plan based on updated images and dose. Materials and methods: VMAT-CT and planning CT of phantoms were fused by rigid or deformable registration to create VMAT-CT+ images. Trackings based on planning CT, VMAT-CT+, and cone beam CT (CBCT) were compared. When prescription dose was not met for planning target volume (PTV), re-planning was demonstrated on an in-house deformable phantom. Possible uncertainties were also evaluated. Results: Tracking based on VMAT-CT+ was accurate and superior to those based on planning CT and CBCT since VMAT-CT+ can detect changes during treatment. PTV coverage in the deformable phantom decreased after deformations but went up and met the prescription goal after re-planning. The impact of uncertainties on dose was minimal. Conclusion: 3D tracking and adaptation of VMAT based on VMAT-CT are feasible. Our study has the potential to increase the confidence of beam delivery, catch and remedy errors during VMAT
Observation of Exciton-Phonon Sideband in Individual Metallic Single-Walled Carbon Nanotubes
Single-walled carbon nanotubes (SWCNTs) are quasi-one-dimensional systems
with poor Coulomb screening and enhanced electron-phonon interaction, and are
good candidates for excitons and exciton-phonon couplings in metallic state.
Here we report back scattering reflection experiments on individual metallic
SWCNTs. An exciton-phonon sideband separated by 0.19 eV from the first optical
transition peak is observed in a metallic SWCNT of chiral index (13,10), which
provides clear evidences of excitons in metallic SWCNTs. A static dielectric
constant of 10 is estimated from the reflectance spectrum.Comment: 5 pages, 3 figures; typos corrected, references updated, text
re-arrange
SMART: Robust and Efficient Fine-Tuning for Pre-trained Natural Language Models through Principled Regularized Optimization
Transfer learning has fundamentally changed the landscape of natural language
processing (NLP) research. Many existing state-of-the-art models are first
pre-trained on a large text corpus and then fine-tuned on downstream tasks.
However, due to limited data resources from downstream tasks and the extremely
large capacity of pre-trained models, aggressive fine-tuning often causes the
adapted model to overfit the data of downstream tasks and forget the knowledge
of the pre-trained model. To address the above issue in a more principled
manner, we propose a new computational framework for robust and efficient
fine-tuning for pre-trained language models. Specifically, our proposed
framework contains two important ingredients: 1. Smoothness-inducing
regularization, which effectively manages the capacity of the model; 2. Bregman
proximal point optimization, which is a class of trust-region methods and can
prevent knowledge forgetting. Our experiments demonstrate that our proposed
method achieves the state-of-the-art performance on multiple NLP benchmarks.Comment: The 58th annual meeting of the Association for Computational
Linguistics (ACL 2020
Long-term in situ observations on typhoon-triggered turbidity currents in the deep sea
This work is supported by the National Science Foundation of China (grants 91528304, 41576005, and 41530964). We thank J. Li, X. Lyu, P. Li, K. Duan, J. Ronan, Y. Wang, P. Ma, and Y. Li for cruise assistance; G. de Lange and J. Hinojosa for editing an early version of manuscript; and E. Pope and two anonymous reviewers for their reviews.Peer reviewedPublisher PD
Study on an Intelligent Optical Fibre Displacement Sensor
AbstractLaser interferometry measurements are difficult to use in industrial environments for expensive, and optical fiber sensors based on intensity are sensitive to the service voltage and thermal drifts of the surrounding medium. To help to solve these problems, an intelligent intensity optical fiber sensor based on two-circle reflective coaxial bundle is presented. The structure of the sensorĀ andĀ measurement system are designed with auto- zeroing and auto-compensation, and its sensitivity, noise level, and drift compensation are calculated to offer quantitative guidance for the design and implementation of the sensor
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