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Search Results: 1 - 10 of 120218 matches for " WANG Zhendong "
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An anecdote on the yon Kármán vortex street and it''''s applications

WANG Zhendong,

力学与实践 , 2006,
Abstract: 根据冯·卡门的著作,阐述了卡门涡街研究的历史.讨论了卡门涡街的应用.
Notes on poets and poetries related with mechanics

WANG Zhendong,

力学与实践 , 2006,
Abstract: 常有人问笔者:你怎么会在力学的学习和研究中,想起将唐宋诗词与力学现象联系起来呢?本文叙述省悟唐宋诗词中有关力学现象和知识的经过,力学诗话文章的北大渊源, 以及40余年来多次写“野渡无人舟自横”文章过程中遇到的一些趣事
A talk on doing research work and writing research papers, specially addressed to postgraduate students

WANG Zhendong,

力学与实践 , 2006,
Abstract: 讨论了什么是好科技文章的标准,做学问应追求怎样的境界.
The spread and development of modern mechanics in China

WANG Zhendong,

力学与实践 , 2006,
Abstract: 评论介绍武际可教授2005年出版的力学史新作《近代力学在中国的传播与发展》.
pi-Electron theory of transverse optical excitons in semiconducting single-walled carbon nanotubes
Zhendong Wang,Hongbo Zhao,Sumit Mazumdar
Physics , 2007, DOI: 10.1103/PhysRevB.76.115431
Abstract: We present a quantitative theory of optical absorption polarized transverse to the tube axes in semiconducting single-walled carbon nanotubes. Transverse optical absorption in semiconducting single-walled carbon nanotubes is to an exciton state that is strongly blueshifted, relative to the two lowest longitudinal excitons, by electron-electron interactions. The binding energy of the transverse exciton is considerably smaller than those of the longitudinal excitons. Electron-electron interactions also reduce the relative oscillator strength of the transverse optical absorption. Our theoretical results are in excellent agreement with recent experimental measurements in four chiral nanotubes.
Essential optical states in $π$-conjugated polymer thin films
Zhendong Wang,Sumit Mazumdar,Alok Shukla
Physics , 2007,
Abstract: We develop a theory of the electronic structure and photophysics of interacting chains of $\pi$-conjugated polymers to understand the differences between solutions and films. While photoexcitation generates only the exciton in solutions, the optical exciton as well as weakly allowed excimers are generated in films. Photoinduced absorption in films is primarily from the lowest excimer. We are also able to explain peculiarities associated with photoluminescence, including delayed photoluminescence and its quenching by electric field.
Universality in the Photophysics of pi-Conjugated Polymers and Single-Walled Carbon Nanotubes
Sumit Mazumdar,Zhendong Wang,Hongbo Zhao
Physics , 2008,
Abstract: We describe both pi-conjugated polymers and semiconducting single-walled carbon nanotubes because of the remarkable similarities in their behavior under photoexcitation. The common themes between these two seemingly different classes of materials are pi-conjugation, quasi one-dimensionality, and strong Coulomb interactions. Theoretical understanding of both systems requires going beyond traditional band theory. We present our current understanding of the electronic structures and excited state absorptions in both systems within a common theoretical model. Our aim is to give physical interpretations of experiments that have been performed and to give guidance to future experimental work.
Photophysics of charge-transfer excitons in thin films of π-conjugated polymers
Zhendong Wang,Sumit Mazumdar,Alok Shukla
Physics , 2008, DOI: 10.1103/PhysRevB.78.235109
Abstract: We develop a theory of the electronic structure and photophysics of interacting chains of \pi- conjugated polymers to understand the differences between solutions and films. While photoexcitation generates only the intrachain exciton in solutions, the optical exciton as well as weakly allowed charge-transfer excitons are generated in films. We extend existing theories of the lowest polaronpair and charge-transfer excitons to obtain descriptions of the excited states of these interchain species, and show that a significant fraction of ultrafast photoinduced absorptions in films originate from the lowest charge-transfer exciton. Our proposed mechanism explains the simultaneous observation of polaronlike induced absorption features peculiar to films in ultrafast spectroscopy and the absence of mobile charge carriers as deduced from other experiments. We also show that there is a 1:1 correspondence between the essential states that describe the photophysics of single chains and of interacting chains that constitute thin films.
Quantitative calculations of the excitonic energy spectra of semiconducting single-walled carbon nanotubes within a $π$-electron model
Zhendong Wang,Hongbo Zhao,Sumit Mazumdar
Physics , 2006, DOI: 10.1103/PhysRevB.74.195406
Abstract: Using Coulomb correlation parameters appropriate for $\pi$-conjugated polymers (PCPs), and a nearest neighbor hopping integral that is arrived at by fitting the energy spectra of three zigzag semiconducting single-walled carbon nanotubes (S-SWCNTs), we are able to determine quantitatively the exciton energies and exciton binding energies of 29 S-SWCNTs within a semiempirical $\pi$-electron Hamiltonian that has been widely used for PCPs. Our work establishes the existence of a deep and fundamental relationship between PCPs and S-SWCNTs.
Planning Margins to CTV for Image-Guided Whole Pelvis Prostate Cancer Intensity-Modulated Radiotherapy  [PDF]
Zhendong Wang, Kelin Wang, Fritz A. Lerma, Bei Liu, Pradip Amin, Byongyong Yi, Georges Hobeika, Cedric Yu
International Journal of Medical Physics,Clinical Engineering and Radiation Oncology (IJMPCERO) , 2012, DOI: 10.4236/ijmpcero.2012.12004
Abstract: Purpose: We investigated the margin recipes with different alignment techniques in the image-guided intensity-modulated radiotherapy (IMRT) of whole pelvis prostate cancer patients. Materials and Methods: Forty-eight computed tomography (CT) scans of eight prostate cancer patients were investigated. Each patient had an initial planning CT scan and 5 consecutive serial CT scans during the course of treatment, all of which were acquired using 3 mm slice separation and 0.94 mm resolution in the axial plane at 120 kVp, on a PQ 5000 CT scanner. Three different whole pelvis planning margin recipes, ranging from 3 to 13 mm, were investigated. A unique IMRT plan was created with each PTV on the initial CT scan, and was then registered to the 5 serial CT scans, by bony alignment or by prostate gland-based alignment. The dose computed on each serial CT scans was accumulated back to the initial CT scan using deformable image registration for final dosimetric evaluation of the interplay of the margin selection and alignment methods. Results: Bony alignment and prostate gland-based alignment gave very similar result to the pelvic lymphatic nodes (PLNs), regardless of its margin around. The prostate gland-based alignment greatly enhanced the coverage to the prostate and SV, especially with small margins. Meanwhile, the soft-tissue alignment also raised the incidental dose to the rectum and reduces the dose to the bladder. With small to intermediate margins, only soft-tissue alignment gave acceptable mean coverage to SV. Margin of 13mm or more was needed for PLNs to maintain good target coverage. Conclusion: We commend prostate-based alignment along with margins less than or equal to 5mm around prostate and SV, and margins greater than or equal to 13 mm around the vascular spaces.
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