检索结果-南通市图书馆

Measuring the Distance of VX Sagittarii with SiO Maser Proper Motions

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Astronomy and Astrophysics 2007年第4期7卷 531-538页

作者： Xi Chen zhi-Qiang shen Ye Xu Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 Department of Earth Sciences National Taiwan Normal University 88 Sec. 4 Ting-Chou Rd. Taipei 116 Taiwan

We report on 43 GHz v=1, J=1-0 SiO maser proper motions in the circumstellar envelope of the M-type semi-regular variable star VX Sgr, observed by Very Long Baseline Array （VLBA） at 3 epochs during 1999 April-May. Applying the statistical parallax analysis to these proper motions, we estimated a distance of VX Sgr of 1.57±0.27kpc, which is consistent with that based on the proper motions of H20 masers, or on the assumption that VX Sgr belongs to the Sgr OB1 association. At this distance, VX Sgr can be classified as a red supergiant. Comparing the statistical parallax method with those of model fitting and annual parallax, we think that the statistical parallax method may be a good way of estimating SiO maser distances at present.

关键词： methods: statistical - masers -stars: individual (VX Sgr)- stars: distances

Investigation of rheo-diecasting mold filling of semi-solid A380 aluminum alloy slurry

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2017年第6期24卷 691-700页

作者： zhi-yong Liu Wei-min Mao Wei-pan Wang zhi-kai Zheng Rui Yue School of Materials Science and Engineering Tsinghua University Beijing 100084 China School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China Beijing Nanshan Institute of Aeronautical Materials Beijing 100048 China National Engineering Research Center of Light Alloy Net Forming Shanghai Jiao Tong University Shanghai 200240 China

The rheo-diecasting mold filling capacity and the microstructure of the semi-solid A380 aluminum alloy slurry were investigated. The results show that the mold filling capacity was strengthened with increasing pouring temperature or increasing injection pressure. Under certain process parameters, the mold cavity was fully filled. However, the mold filling capacity decreased with increasing holding time. The mold filling capacity was improved with increasing shape factor of primary α(Al) grains; however, the solid fraction and the grain size significantly increased at the same time. In addition, the microstructures along the route of the spiral samples obviously differed. The grain size decreased gradually from the near-end to the far-end, whereas the shape factor increased gradually.

关键词： aluminum alloys semi-solid slurry rheo-diecasting mold filling microstructure

The Conservation and Convergence of Two Finite Difference Schemes for KdV Equations with Initial and Boundary Value Conditions

在线全文

学校读者我要写书评

暂无评论

Numerical Mathematics(Theory,Methods and Applications) 2020年第1期13卷 253-280页

作者： Jinye shen Xuping Wang zhi-zhong Sun School of Mathematics Southeast UniversityNanjing 210096JiangsuChina

Korteweg-de Vries equation is a nonlinear evolutionary partial differential equation that is of third order in *** the approximation to this equation with the initial and boundary value conditions using the finite difference method,the difficulty is how to construct matched finite difference schemes at all the inner grid *** this paper,two finite difference schemes are constructed for the *** accuracy is second-order in time and first-order in *** first scheme is a two-level nonlinear implicit finite difference scheme and the second one is a three-level linearized finite difference *** Browder fixed point theorem is used to prove the existence of the nonlinear implicit finite difference *** con-servation,boundedness,stability,convergence of these schemes are discussed and analyzed by the energy method together with other *** two-level non-linear finite difference scheme is proved to be unconditionally convergent and the three-level linearized one is proved to be conditionally *** numerical examples illustrate the efficiency of the proposed finite difference schemes.

关键词： Nonlinear Korteweg-de Veries equation difference scheme existence conserva-tion boundedness convergence

Consensus Proximal Support Vector Machine for Classification Problems with Sparse Solutions

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of the Operations Research Society of China 2014年第1期2卷 57-74页

作者： Yan-Qin Bai Yan-Jun shen kai-Ji shen Department of Mathematics Shanghai UniversityShanghai 200444China

Classification problem is the central problem in machine *** vector machines(SVMs)are supervised learning models with associated learning algorithms and are used for classification in machine *** this paper,we establish two consensus proximal support vector machines(PSVMs)models,based on methods for binary *** first one is to separate the objective functions into individual convex functions by using the number of the sample points of the training *** constraints contain two types of the equations with global variables and local variables corresponding to the consensus points and sample points,*** get more sparse solutions,the second one is l1–l2 consensus PSVMs in which the objective function contains an■1-norm term and an■2-norm term which is responsible for the good classification performance while■1-norm term plays an important role in finding the sparse *** consensus PSVMs are solved by the alternating direction method of ***,they are implemented by the real-world data taken from the University of California,Irvine Machine Learning Repository(UCI Repository)and are compared with the existed models such as■1-PSVM,■p-PSVM,GEPSVM,PSVM,and *** results show that our models outperform others with the classification accuracy and the sparse solutions.

关键词： Classification problems Support vector machine Proximal support vector machine Consensus Alternating direction method of multipliers

Fully Fabric-Based Triboelectric Nanogenerators as Self-Powered Human-Machine Interactive Keyboards

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nano-Micro Letters 2021年第7期13卷 42-54页

作者： Jia Yi kai Dong shen shen Yang Jiang Xiao Peng Cuiying Ye Zhong Lin Wang School of Physical Science and Technology Guangxi UniversityNanning 530004People’s Republic of China CAS Center for Excellence in Nanoscience Beijing Key Laboratory of Micro-Nano Energy and SensorBeijing Institute of Nanoenergy and NanosystemsChinese Academy of SciencesBeijing 100083People’s Republic of China School of Nanoscience and Technology University of Chinese Academy of SciencesBeijing 100049People’s Republic of China School of Material Science and Engineering Georgia Institute of TechnologyAtlantaGA 30332-0245USA

Combination flexible and stretchable textiles with self-powered sensors bring a novel insight into wearable functional electronics and cyber security in the era of Internet of *** work presents a highly flexible and self-powered fully fabric-based triboelectric nanogenerator(F-TENG)with sandwiched structure for biomechanical energy harvesting and real-time biometric *** prepared F-TENG can power a digital watch by low-frequency motion and respond to the pressure change by the fall of leaves.A self-powered wearable keyboard(SPWK)is also fabricated by integrating large-area F-TENG sensor arrays,which not only can trace and record electrophysiological signals,but also can identify individuals’typing characteristics by means of the Haar *** on these merits,the SPWK has promising applications in the realm of wearable electronics,self-powered sensors,cyber security,and artificial intelligences.

关键词： Triboelectric nanogenerators Self-powered keyboard Human-machine interface Wearable electronics Fully fabric-based

Negatively and positively charged bacterial aerosol concentration and diversity in natural environments

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2013年第26期58卷 3169-3176页

作者： shen FangXia kai Wei YAO Maosheng State Key Joint Laboratory of Environmental Simulation and Pollution Control College of Environmental Sciences and Engineering Peking University

Bioaerosol charge information is of vital importance for their electrostatic collection. Here, electrostatic means and molecular tools were applied to studying bioaerosol charge dynamics. Positively or negatively charged bioaerosols were collected using an electrostatic sampler operated with a field strength of 1.1 kV cm 1 at a flow rate of 3 L min 1 for 40 min. Those with fewer or no charges bypassing the sampler were also collected using a filter at the downstream of the electrostatic sampler in one environment. The experiments were independently conducted three times in three different environments. The collected bacterial aerosols were cultured directly on agar plates at 26°C, and the colony forming units (CFU) were manually counted. In addition, the CFUs were washed off from the agar plates, and further subjected to polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) for culturable diversity analysis. The results revealed remarkable differences in positively and negatively charged culturable bacterial aerosol concentration and diversity among the studied environments. In the office environment, negatively charged culturable bacterial aerosols appeared to dominate (P = 0.0489), while in outdoor and hotel environments both polarities had similar concentration levels (P = 0.078, P = 0.88, respectively). DGGE patterns for positively charged culturable bacterial aerosols were shown strikingly different from those of negatively charged regardless of the sampling environments. In addition, for each of the environments positively charged culturable bacterial aerosols collected were found to have more band pattern similarity with those positively charged for respective regions of agar plates than those negatively charged, and vice versa. The information developed here is useful for developing efficient electrostatic sampling protocols for bioaerosols.

关键词：气溶胶浓度多样性分析办公环境正电荷细菌生物气溶胶变性梯度凝胶电泳静电收集

A sodium laser guide star coupling efficiency measurement method

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2016年第9期16卷 95-100页

作者： Lu Feng zhi-Xia shen Suijian Xue Yang-Peng Li kai Jin Angel Otarola Yong Bo Jun-Wei Zuo Qi Bian kai Wei Jing-Yao Hu Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China The Institute of Optics and Electronics Chinese Academy of Sciences Chengdu 610209 China Technical Institute of Physics and Chemistry Chinese Academy of Sciences Beijing 100190 China Thirty Meter Telescope Corporation Pasadena California USA

A large telescope＇s adaptive optics （AO） system requires one or more bright artificial laser guide stars to improve its sky coverage. The recent advent of a high power sodium laser is perfect for such application. However, besides the output power, other parameters of the laser also have a significant impact on the brightness of the generated sodium laser guide star, mostly in non-linear relationships. When tuning and optimizing these parameters it is necessary to tune based on a laser guide star generation performance metric. Although return photon fluxis widely used, variability of the atmosphere and sodium layer makes it difficult to compare results from different sites or even within a short time period for the same site. A new metric, coupling efficiency, is adopted in our field tests. In this paper, we will introduce our method for measuring the coupling efficiency of a 20W class pulse sodium laser for AO application during field tests that were conducted during 2013-2015.

关键词： instrumentation adaptive optics -- methods observational -- atmospheric effects

Environmental impact of radionuclide migration in groundwater from a low intermediate level radioactive waste repository

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2001年第2期13卷 180-184页

作者： Wang, Jin-sheng Yang, zhi-feng Li, Shu-shen Wang, zhi-ming Institute of Environmental Sciences Beijing Normal UniversityState Key Joint Laboratory of Environmental Simulation and Pollution Control Beijing 100875 China China Institute for Radiation Protection Taiyuan 030006 China

The radionuclide migration from a certain Chinese repository with low-intermediate level radioactive solid waste is studied. The migration in groundwater is analyzed and computed in detail. Under presumption of normal releasing, or the bottom of the repository has been marinated for one month with precipitation reaching 600 mm once and a 6 m aerated zone exists, a prediction for 7 radionuclides is conducted. It shows that the aerated zone is the primary barrier for migration. The migration for radionuclides 60Co, 137Cs, 90Sr, 63Ni, etc. will be retarded in it within 500 years. The concentration of 239Pu will be decreased by amount of 6 order. Only 3H and 14C can migrate through the aerated zone. The radionuclides that go through the aerated zone and enter the aquifer will exist in spring, stream and sea. Based on this, the intake dose by residents in different age group resulting from drinking contaminated spring water, eating seafood is calculated. The results showed that the impact of the repository to the key resident group is lower than the limit in national repository regulation standard. This complies with the repository management target.

关键词： intermediate level radioactive waste repository Environmental impact of radionuclide migration in groundwater from a low

Alternating Direction Method of Multipliers for l_(1)-l_(2)-Regularized Logistic Regression Model

在线全文

学校读者我要写书评

暂无评论

Journal of the Operations Research Society of China 2016年第2期4卷 243-253页

作者： Yan-Qin Bai kai-Ji shen Department of Mathematics Shanghai UniversityShanghai 200444China

Logistic regression has been proved as a promising method for machine learning,which focuses on the problem of *** this paper,we present anl_(1)-l_(2)-regularized logistic regression model,where thel1-norm is responsible for yielding a sparse logistic regression classifier and thel_(2)-norm for keeping betlter classification *** solve thel_(1)-l_(2)-regularized logistic regression model,we develop an alternating direction method of multipliers with embedding limitedlBroyden-Fletcher-Goldfarb-Shanno(L-BFGS)***,we implement our model for binary classification problems by using real data examples selected from the University of California,Irvine Machines Learning Repository(UCI Repository).We compare our numerical results with those obtained by the well-known LIBSVM and SVM-Light *** numerical results show that ourl_(1)-l_(2)-regularized logisltic regression model achieves better classification and less CPU Time.

关键词： Classification problems Logistic regression model Sparsity Alternating direction method of multipliers