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Interval Estimation for Aggregate Queries on Incomplete Data

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Journal of Computer Science & Technology 2019年第6期34卷 1203-1216页

作者： An-Zhen Zhang jian-zhong Li Hong Gao School of Computer Science and Technology Harbin Institute of TechnologyHarbin 150001China

Incomplete data has been a longstanding issue in the database community, and the subject is yet poorly handled by both theories and practices. One common way to cope with missing values is to complete their imputation (filling in) as a preprocessing step before analyses. Unfortunately, not a single imputation method could impute all missing values correctly in all cases. Users could hardly trust the query result on such complete data without any confidence guarantee. In this paper, we propose to directly estimate the aggregate query result on incomplete data, rather than to impute the missing values. An interval estimation, composed of the upper and the lower bound of aggregate query results among all possible interpretations of missing values, is presented to the end users. The ground-truth aggregate result is guaranteed to be among the interval. We believe that decision support applications could benefit significantly from the estimation, since they can tolerate inexact answers, as long as there are clearly defined semantics and guarantees associated with the results. Our main techniques are parameter-free and do not assume prior knowledge about the distribution and missingness mechanisms. Experimental results are consistent with the theoretical results and suggest that the estimation is invaluable to better assess the results of aggregate queries on incomplete data.

关键词： incomplete data aggregate query interval estimation data quality

Orientation distribution of fibers and rheological property in fiber suspensions flowing in a turbulent boundary layer

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Acta Mechanica Sinica 2008年第3期24卷 243-250页

作者： jian zhong Lin Ke Sun Weifeng Zhang China Jiliang University Hangzhou 310018 China Department of Mechanics Zhejiang UniversityHangzhou 310027 China Institute of Marine and Coastal Sciences Rutgers UniversityNew Brunswick N J USA

A model relating the translational and rotational transport of orientation distribution function （ODF） of fibers to the gradient of mean ODF and the dispersion coefficients is proposed to derive the mean equation for the ODE Then the ODF of fibers is predicted by.numerically solving the mean equation for the ODF together with the equations of turbulent boundary layer flow. Finally the shear stress and first normal stress difference of fiber suspensions are obtained. The results, some of which agree with the available relevant experimental data, show that the most fibers tend to orient to the flow direction. The fiber aspect ratio and Reynolds number have significant and negligible effects on the orientation dis- tribution of fibers, respectively. The additional normal stress due to the presence of fibers is anisotropic. The shear stress of fiber suspension is larger than that of newtonian solvent, and the first normal stress difference is much less than the shear stress. Both the additional shear stress and the first normal stress difference increase with increasing the fiber concentration and decreasing fiber aspect ratio.

关键词： Turbulent fiber suspensions Fiber orientation Rheological property Boundary layer numericalsimulation

B位掺杂提升CsSnI_(3)钙钛矿结构和电荷稳定性的第一性原理研究

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原子与分子物理学报 2025年第6期42卷 144-152页

作者：赵思健葛治中杨旭东上海交通大学材料科学与工程学院上海200240

全无机CsSnI_(3)钙钛矿拥有理想的带隙宽度(1.3 eV),光电转化效率理论峰值达到33%.目前CsSnI_(3)太阳能电池的发展受制于的CsSnI_(3)的结构不稳定性和Sn^(2+)易被氧化为Sn^(4+)的问题.研究基于第一性原理,详细探讨了一系列金属元素对CsS... 详细信息

全无机CsSnI_(3)钙钛矿拥有理想的带隙宽度(1.3 eV),光电转化效率理论峰值达到33%.目前CsSnI_(3)太阳能电池的发展受制于的CsSnI_(3)的结构不稳定性和Sn^(2+)易被氧化为Sn^(4+)的问题.研究基于第一性原理,详细探讨了一系列金属元素对CsSnI_(3)进行B位掺杂改性的方案,旨在提升CsSnI_(3)结构稳定性,并抑制CsSnI_(3)中Sn^(2+)被氧化为Sn^(4+)的问题.计算结果表明,在CsSnI_(3)钙钛矿B位掺杂三价金属Sb、Bi能够阻碍CsSnI_(3)相变生成Cs_(2)SnI_6,并且抑制Sn^(2+)的氧化;尤其在晶格中存在锡空位缺陷时,Sb、Bi掺杂对于Sn^(4+)形成的抑制效果更为显著.同时,低浓度的Sb、Bi掺杂不会改变CsSnI_(3)的直接带隙特性,且带隙宽度变化较小,因此能够在维持CsSnI_(3)优良光电活性的基础上进一步提高结构和电荷的稳定性.研究结果为实现高效且稳定的CsSnI_(3)钙钛矿太阳能电池提供了重要的理论指导.

关键词：全无机锡基钙钛矿第一性原理 B位掺杂相稳定性电子结构

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Prediction of nuclear charge density distribution with feedback neural network

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nuclear Science and Techniques 2022年第12期33卷 24-35页

作者： Tian‑Shuai Shang jian Li zhong‑Ming niu College of Physics Jilin UniversityChangchun 130012China School of Physics and Optoelectronic Engineering Anhui UniversityHefei 230601China

nuclear charge density distribution plays an important role in both nuclear and atomic physics,for which the two-parameter Fermi(2pF)model has been widely applied as one of the most frequently used ***,the feedforward neural network has been employed to study the available 2pF model parameters for 86 nuclei,and the accuracy and precision of the parameter-learning effect are improved by introducing A^(1∕3)into the input parameter of the neural ***,the average result of multiple predictions is more reliable than the best result of a single prediction and there is no significant difference between the average result of the density and parameter values for the average charge density *** addition,the 2pF parameters of 284(near)stable nuclei are predicted in this study,which provides a reference for the experiment.

关键词： Charge density distribution Two-parameter Fermi model Feedforward neural network approach

Optimal Technology Investment under Emission Trading Policy

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Journal of Systems Science and Systems Engineering 2020年第2期29卷 143-162页

作者： Shuo Huang zhong Wen jian Chen ning Cui School of Economics and Management Tsinghua UniversityBeijing 100084China Beijing Foreign Studies University China Southern Asset Management Co. Ltd.

Low-carbon economy is gaining growing attention nowadays as global warming *** a market-based policy,emission trading policy is widely considered an effective means to achieve the doublewin of economic development and environmental *** such circumstances,carbon trading markets are developing rapidly in many countries and regions,demanding more attention to compliance strategy issues for emission-intensive *** this study,we build a dynamic programming model in search of the optimal emission trading and technology investment decisions for a make-to-order company faced with a stochastic demand under emission trading *** a comprehensive analysis of the proposed model,we find that an optimal emission permit level,which increases in carbon penalty and decreases in carbon price,exists in each *** for the abatement technology investment decision,the firm should invest only ff the investment cost per unit of abatement effort is less than a certain threshold,which increases in carbon penalty and carbon *** the basis of a two-period dynamic programming model,we further explore the problem of investment *** show how optimal investment decisions are influenced by the speed of technology progress under different *** findings are important for firms to choose the time of investment depending on specific situations.

关键词： Low-carbon emission trading compliance strategy investment-timing

Improved Identification Method and Fault Current Limiting Strategy for Commutation Failure in LCC-HVDC

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Journal of Modern Power Systems and Clean Energy 2022年第6期10卷 1761-1772页

作者： jian Liu Sheng Lin Wenliang zhong Lei Liu School of Electrical Engineering Southwest Jiaotong UniversityChengdu 610031China State Grid Sichuan Electric Power Research Institute Chengdu 610072China

Line-commutated converter based high-voltage direct-current(LCC-HVDC)transmission systems are prone to subsequent commutation failure(SCF),which consequently leads to the forced blocking of HVDC links,affecting the operation of the power *** accurate commutation failure(CF)identification is fairly vital to the prevention of ***,the existing CF identification methods cause CF misjudge or detection lag,which can limit the effect of SCF mitigation *** addition,earlier approaches to suppress SCF do not clarify the key factor that determines the evolution of extinction angle during system recovery and neglect the ***,this paper firstly analyzes the normal commutation process and CF feature based on the evolution topology of converter valve conduction in ***,the energy in the leakage inductance of converter transformer is presented to characterize the commutation state of the *** a CF identification method is proposed utilizing the leakage inductance ***,taking the key variable which is crucial to the tendency of extinction angle during the recovery process into account,a fault current limiting strategy for SCF mitigation is put *** with the original methods,the proposed methods have a better performance in CF identification and mitigation in terms of detection accuracy and mitigation ***,case study on PSCAD/EMTDC validates the proposed methods.

关键词： Line commutated converter based high-voltage direct current(LCC-HVDC)transmission commutation failure identification commutation failure mitigation HVDC transmission control

Controlling Membrane Phase Separation of Polymersomes for Programmed Drug Release

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Chinese Journal of Polymer Science 2022年第9期40卷 1006-1015页

作者： Shuai Chen Erik Jan Cornel jian-zhong Du Department of Orthopedics Shanghai Tenth People’s HospitalSchool of MedicineTongji UniversityShanghai 200072China Department of Polymeric Materials School of Materials Science and EngineeringTongji UniversityShanghai 201804China

Programmed release of small molecular drugs from polymersomes is of great importance in drug delivery.A significant challenge is to adjust the membrane permeability in a well-controlled ***,we propose a strategy for controlling membrane phase separation by photo-cross-linking of the membrane-forming blocks with different molecular *** synthesized three amphiphilic block copolymers with different membrane-forming blocks,which are poly(ethylene oxide)_(43)-b-poly((ε-caprolactone)_(45)-stat-((α-(cinnamoyloxymethyl)-1,2,3-triazol)caprolactone)_(25))(PEO_(43)-b-P(CL_(45)-stat-CTCL_(25))),PEO_(43)-b-P(CL_(108)-stat-CTCL_(16)),and PEO_(43)-b-PCTCL_(4)-b-PCL_(79).These polymers were self-assembled into polymersomes using either a solvent-switch or powder rehydration method,and the obtained polymersomes were characterized by dynamic light scattering and transmission electron *** the phase separation patterns within the polymersome membranes were investigated by mesoscopic dynamics(MesoDyn)*** further confirm the change of the membrane permeability that resulted from the phase separation within the membrane,doxorubicin,as a small molecular drug,was loaded and released from the *** to the incompatibility between membrane-forming moieties(PCTCL and PCL),phase separation occurs and the release rate can be tuned by controlling the membrane phase pattern or by ***,besides the compacting effect by formation of chemical bonds in the membrane,the cross-linking process can act as a driving force to facilitate the rearrangement and re-orientation of the phase pattern,which also influences the drug release behavior by modulating the cross-membrane distribution of the amorphous PCTCL *** this way,the strategy of focusing on the membrane phase separation for the preparation of the polymersomes with finely tunable drug release rate can be envisioned and designed accordingly,which is of great signifi

关键词： Polymersome Drug delivery Phase separation Programmed drug release

numerical solutions of a multi-class traffic flow model on an inhomogeneous highway using a high-resolution relaxed scheme

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Journal of Zhejiang University-Science C(Computers and Electronics) 2012年第1期13卷 29-36页

作者： jian-zhong CHEn zhong-ke SHI y.n-mei HU College of Automation Northwestern Polytechnical University Xi＇an 710072 China College of Science Chang ＇an University Xi ＇an 710064 China

A high-resolution relaxed scheme which requires little information of the eigenstructure is presented for the multiclass Lighthill-Whitham-Richards （LWR） model on an inhomogeneous highway. The scheme needs only an estimate of the upper boundary of the maximum of absolute eigenvalues. It is based on incorporating an improved fifth-order weighted essentially.non-oscillatory （WEnO） reconstruction with relaxation approximation. The scheme benefits from the simplicity of relaxed schemes in that it requires no exact or approximate Riemann solvers and no projection along characteristic directions. The effectiveness of our method is demonstrated in several numerical examples.

关键词： Relaxed scheme Multi-class model Weighted essentially.non-oscillatory (WEnO) reconstruction

Two new Sesquiterpenes from Ligularia Duciformis

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Chemical Research in Chinese Universities 1999年第1期15卷 72-74页

作者： GAO Kun JIA zhong-jian Department of Chemistry National Laboratory of Applied Organic ChemistryLanzhou UniversityLanzhou 730000

ＡｐｒｅｖｉｏｕｓｐｈｙｔｏｃｈｅｍｉｃａｌｓｔｕｄｙｏｆＬｉｇｕｌａｒｉａｄｕｃｉｆｏｒｍｉｓｄｅａｌｔｗｉｔｈｔｈｅｉｓｏｌａｔｉｏｎｏｆｃｏｎｉｆｅｒｙｌａｌｃｏｈｏｌｄｅｒｉｖａｔｉｖｅｓ［１，２］．Ｉｎｏｒ... 详细信息

ＡｐｒｅｖｉｏｕｓｐｈｙｔｏｃｈｅｍｉｃａｌｓｔｕｄｙｏｆＬｉｇｕｌａｒｉａｄｕｃｉｆｏｒｍｉｓｄｅａｌｔｗｉｔｈｔｈｅｉｓｏｌａｔｉｏｎｏｆｃｏｎｉｆｅｒｙｌａｌｃｏｈｏｌｄｅｒｉｖａｔｉｖｅｓ［１，２］．Ｉｎｏｒｄｅｒｔｏｆｉｎｄｓｅｓｑｕｉｔｅ...

关键词： Ligularia duciformis Roots Sesquiterpenes Liguducin A Liguducin B 2D nMR