检索结果-南通市图书馆

one-step estimation for varying coefficient models

在线全文

学校读者我要写书评

暂无评论

Science China Mathematics 2005年第2期48卷 198-213页

作者： TANG Qingguo & WANG Jinde Department of Mathematics, Nanjing University, Nanjing 210093, China Institute of Sciences, PLA University of Science and Technology, Nanjing 210007, China 1. Department of Mathematics Nanjing University 210093 Nanjing China 2. Institute of Sciences PLA University of Science and Technology 210007 Nanjing China

A one-step method is proposed to estimate the unknown functions in the varying coefficient models, in which the unknown functions admit different degrees of smoothness. In this method polynomials of different orders are used to approximate unknown functions with different degrees of smoothness. As only one minimization operation is employed, the required computation burden is much less than that required by the existing two-step estimation method. It is shown that the one-step estimators also achieve the optimal convergence rate. Moreover this property is obtained under conditions milder than that imposed in the two-step estimation method. More importantly, as only one minimization operation is employed, the full asymptotic properties, not only the asymptotic bias and variance, but also the asymptotic distributions of the estimators can be derived. The asymptotic distribution results will play a key role for making statistical inference.

关键词： varying coefficient model, one-step estimation, asymptotic distribution, optimal convergence rate.

Preparation of CdSe/ZnSe Core-shell Nanocrystal in one-step Reaction

在线全文

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2005年第6期21卷 728-733页

作者： FEI Xiao-fang SHAN Gui-ye KONG Xiang-gui WANG Xin ZENG Qing-hui ZHANG You-lin Key Laboratory of Excited State Physics Process Changchun Institute of Optic Fine Mechanics and Physics Chinese Academy of Sciences Changchun 130033 P. R. China College of Life Sciences Jilin University Changchun 130021 P. R. China Center for Advanced Optoelectronic Functional Material Research Northeast Normal University Changchun 130024 P. R. China

High-quality Zn-doped CdSe core-shell nanocrystals were successfully prepared by incorporating a stoichiometric amount of Zn precursor into the CdSe reaction system, in which the Se precursor was excess and an Se-rich surface was formed. By injecting different amounts of Zn precursor, the core-shell nanocrystals demonstrated by the emission spectra were formed. The obtained Zn-doped CdSe nanocrystals exhibit a photoluminescence efficiency from 30% to 85%, which is comparable to those for the reported CdSe/ZnS, CdSe/CdS in the literature. In particular, a shell ZnSe layer with different thicknesses of ZnSe can be formed in this experiment by only changing the amount of Zn precursor added, which is simple and effective.

关键词： CdSe/ZnSe Core-shell one-step Photoluminescence

one-step straightfoward solid synthesis of high yield white fluorescent carbon dots for white light emitting diodes

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2021年第2期32卷 591-593页

作者： Bingyan Han Jingmei Jiang Qifang Yan Ze Xina Qin Yan State Key Laboratory of Fine Chemicals Dalian University of TechnologyDalian 116023China School of Chemical Engineering Dalian University of TechnologyPanjin 124221China

Herein,we directly prepared white fluorescent CDs(W-CDs) using 1,6-dihydroxynaphthalene(1,6-DHN)and L-asparagine(L-Asn) as carbon sources through a simple solvent-free ***-prepared W-CDs can be obtained in high yield(95%).A relative pure white LEDs(WLEDs) were fabricated with Commission Internationale de Eclairage(CIE) coordinates of(0.32,0.31).As-prepared W-CDs will have promising future for a wide range of optoelectronic devices.

关键词： Fluorescent carbon dots Solid synthesis High yield White LEDs one-step

Variable bandwidth and one-step local M-estimator

在线全文

学校读者我要写书评

暂无评论

Science China Mathematics 2000年第1期43卷 65-81页

作者：范剑青蒋建成 University of North Carolina at Chapel Hill and Chinese University of Hong Kong Hong Kong China Department of Probability & Statistics Peking University Beijing 100871 China

A robust version of local linear regression smoothers augmented with variable bandwidth is studied. The proposed method inherits the advantages of local polynomial regression and overcomes the shortcoming of lack of robustness of leastsquares techniques. The use of variable bandwidth enhances the flexibility of the resulting local M-estimators and makes them possible to cope well with spatially inhomogeneous curves, heteroscedastic errors and nonuniform design densities. Under appropriate regularity conditions, it is shown that the proposed estimators exist and are asymptotically normal. Based on the robust estimation equation, one-step local M-estimators are introduced to reduce computational burden. It is demonstrated that the one-step local M-estimators share the same asymptotic distributions as the fully iterative M-estimators, as long as the initial estimators are good enough. In other words, the onestep local M-estimators reduce significantly the computation cost of the fully iterative M-estimators without deteriorating their performance. This fact is also illustrated via simulations.

关键词： local regression M-estimator nonparametric estimation one-step robustness variable bandwidth.

one-step quadratic convergence of noninterior continuation method for NCP

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 1999年第20期44卷 1858-1862页

作者： XIU NaihuaDepartment of Mathematics , Northern Jiaotong University , Beijing 100044, China Department of Mathematics Northern Jiaotong University Beijing China

A noninterior continuation method is presented, with only the certering step used at each iteration, for nonlinear complementarity problem. It is shown that the algorithm is globally linearly and locally quadratically... 详细信息

关键词： nonlinear complementarity problem noninterior continuation method one-step quadratic convergence.

one-step disposal of Cr (Ⅵ)-bearing wastewater by natural pyrrhotite

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2000年第17期45卷 1614-1616页

作者： LU Anhuai, CHEN Jie, SHI Junxian, LU Xiaoying, TANG Junli & GUO Min1. Departmenl of Geology, Peking University, Beijing 100871, China 2. National Laboratory of Mineral and Rock Materials, China University of Geosciences, Beijing 100083, China (e-mail: luanhuai Department of Geology Peking University Beijing China National Laboratory of Mineral and Rock Materials China University of Geosciences Beijing China

Cr(Ⅵ)-bearing wastewater can be treated by natural pyrrhotite which is used for reductant to reduce Cr(Ⅵ) and precipitant to precipitate Cr(Ⅲ) simultaneously. The disposal products can be divided into three parts in the beakers, namely supernatant in the upper part, the yellowish colloidal precipitates in the middle part and the pyrrhotite in the lower part. The content of total Cr=Cr(Ⅵ)+Cr(Ⅲ) in the supernatant liquid is 0.06 mg/L, which is lower than 1.5 mg/L of the discharge standard of China and near to 0.05 mg/L of the standard of potable water. This one-step disposal composing of both reduction and precipitation which is traditionally divided into two independent steps called reducing technology and precipitating technology respectively. The new method is of obvious economic advantage and favourable to decreasing surplus mud derived from adding Ca(OH)2 to precipitate Cr(Ⅲ) traditionally so as to avoid recontamination. In fact, sodium sulfite (Na2SO3) used in disposal of Cr(Ⅵ) was

关键词： natural pyrrhotite Cr(Ⅵ)-bearing wastewater reduction Cr(Ⅵ) precipitation Cr(Ⅲ) one-step disposal rational use of mineral resources.

Exploring facile strategies for high-oxidation-state metal nitride synthesis: carbonate-assisted one-step synthesis of Ta_3N_5 films for solar water splitting

在线全文

学校读者我要写书评

暂无评论

Science Bulletin 2018年第21期63卷 1404-1410页

作者： Tao Fang Huiting Huang Jianyong Feng Yingfei Hu Yongsheng Guo Shiying Zhang Zhaosheng Li Zhigang Zou Collaborative Innovation Center of Advanced Microstructures National Laboratory of Solid State Microstructures Department of Physics Nanjing University College of Engineering and Applied Sciences Nanjing University Hunan Key Laboratory of Applied Environmental Photocatalysis Changsha University

Metal nitrides are widely studied due to their outstanding physical properties, including high hardness,high thermal and chemical stability, low electrical resistivity etc. Generally, metal nitrides can be obtained from the direct reaction of metal and ammonia/nitrogen. However, some of the metal nitrides,such as Ta_3N_5, cannot be synthesized by direct nitridation of metals. To achieve Ta_3N_5, high-oxidationstate Ta precursors like Ta_2O_5, NaTaO_3, TaS_3, K_6Ta_(10.8)O_(30), Ta(N(CH_3)_2)_5 and TaCl_5 have to be employed,which is a time-consuming and laborious process with the possibility of introducing undesirable impurities. Here taking Ta_3N_5 as an example, a facile carbonate-assisted one-step nitridation method is proposed, which enables the direct synthesis of high-oxidation-state metal nitride films from metal precursors under ammonia flow. The mechanism of the nitridation process has been studied, which carbon dioxide released from carbonates decomposition reacts with metallic Ta and assists the one-step conversion of metallic Ta to Ta_3N_5. The as-prepared Ta_3N_5 film, after modified with NiFe layered double hydroxide, exhibits promising water splitting performance and stability. This method avoids the preoxidation process of metal precursors in high-oxidation-state metal nitride synthesis, and may facilitate the direct fabrication of other important metal nitrides besides Ta_3N_5.

关键词： Metal nitrides Carbonate-assisted one-step conversion Ta3N5 films Photoelectrochemical Solar water splitting

ICG@ZIF-8:one-step encapsulation of indocyanine green in ZIF-8 and use as a therapeutic nanoplatform

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2018年第9期29卷 1421-1424页

作者： Chao Yang Jing Xu Dandan Yang Xiaoxiao Wang Bin Liu Nongyue He Zhifei Wang School of Chemistry and Chemical Engineering Southeast University Department of Biomedical Engineering Nanjing Medical University School of Biological Science and Medical Engineering Southeast University

How to fabricate zeolitic imidazole framework-8 （ZIF-8） based therapeutic nanoplatform will be of significance in biomedicine considering its good biocompatibility. Herein, we report a one-step encapsulation of indocyanine green （ICG） in ZlF-8 nanoparticles （NPs）. The as-prepared ICG@ZIF-8 NPs possess an absorption band in the near infrared region and have the good photothermal conversion efficiency. The in vivo and in vitro studies show that, after loading chemotherapy agent hydrophobic doxorubicin （DOX）, ICG@ZIF-8-DOX NPs exhibit the chem-and photothermal synergistic therapy for tumor. In addition, it is found that the embedded ICG molecules in ICG@ZlF-8 NPs can be disassociated and released into the solution upon the 808 nm laser irradiation, demonstrating that as-prepared ICG@ZIF-8 NPs can also be used as the optical imaging probe to trace the degradability behavior of resulting NPs in future

关键词： ZIF Therapeutics nanoplatform Chemo-photothermal treatment Indocyanine Green one-step

A GENERAL CLASS OF one-step APPROXIMATION FOR INDEX-1 STOCHASTIC DELAY-DIFFERENTIAL-ALGEBRAIC *EQUATIONS

在线全文

学校读者我要写书评

暂无评论

Journal of Computational Mathematics 2019年第2期37卷 151-169页

作者： Tingting Qin Chengjian Zhang School of Mathematics and Statistics Huazhong University of Science and Technology. Wuhan 430074 China Hubei Key Laboratory of Engineering Modeling and Scientific Computing Huazhong University of Science and Technology Wuhan 430074 China

This paper develops a class of general one-step discretization methods for solving the index-1 stochastic delay differential-algebraic equations. The existence and uniqueness theorem of strong solutions of index-1 equations is given. A strong convergence criterion of the methods is derived, which is applicable to a series of one-step stochastic numerical methods. Some specific numerical methods, such as the Euler-Maruyama method, stochastic ^-methods, split-step ^-methods are proposed, and their strong convergence results are given. Numerical experiments further illustrate the theoretical results.

关键词： Stochastic delay differential-algebraic equations one-step discretization schemes Strong convergence