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Approximation of dense-n/2-subgraph and table compression problems

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Science china Mathematics 2005年第9期48卷 1223-1233页

作者： xu dachuan~1 han jiye~2.& du dongle~3.1. college of applied sciences,beijing university of technology,beijing 10002.,china 2. Institute of applied Mathematics,Academy of Mathematics and Systems Science,Chinese Academy of sciences,beijing 100080,china 3. Faculty of Administration,university of New Brunswick,P.O.Box 4400,Fredericton,NB E3B 5A3,Canada college of applied sciences Beijing University of Technology Beijing 100022 China Institute of applied Mathematics Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100080 China Faculty of Administration University of New Brunswick P.O. Box 4400 Fredericton NB E3B 5A3 Canada

We develop improved approximation algorithms for two NP-hard problems: the dense-n/2-subgraph and table *** on SDP relaxation and advanced rounding techniques,we first propose 0. 5982 and 0. 5970-approximation algorithms respec- tively for the dense-n/2-subgraph problem (DSP) and the table compression problem (TCP). Then we improve these bounds to 0. 6243 and 0. 6708 respectively for DSP and TCP by adding triangle inequalities to strengthen the SDP *** results for TCP beat the 0. 5 bound of a simple greedy algorithm on this problem,and hence answer an open question of Anderson in an affirmative way.

关键词： dense-n/2-subgraph problem(DSP) table compression problem(TCP) SDP approximation ratio

Simultaneous variable selection for heteroscedastic regression models

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Science china Mathematics 2011年第3期54卷 515-530页

作者： ZhanG ZhongZhan1 & WANG DaRong2 1college of applied sciences, beijing university of technology, beijing 100124, china 2The Pilot college, beijing university of technology, beijing 101101, china 1. college of applied sciences Beijing University of Technology Beijing 100124 China2. The Pilot College Beijing University of Technology Beijing 101101 China

In this paper, we propose a new criterion, named PICa, to simultaneously select explanatory variables in the mean model and variance model in heteroscedastic linear models based on the model structure. We show that the new criterion can select the true mean model and a correct variance model with probability tending to 1 under mild conditions. Simulation studies and a real example are presented to evaluate the new criterion, and it turns out that the proposed approach performs well.

关键词： variable selection heteroscedastic regression models adjusted profile log-likelihood AIC BIC

Targeting the organelle for radiosensitization in cancer radiotherapy

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Asian Journal of Pharmaceutical sciences 2024年第2期19卷 52-71页

作者： Xiaoyan Sun Linjie Wu Lina du Wenhong xu Min han Institute of Pharmaceutics College of Pharmaceutical SciencesZhejiang UniversityHangzhou 310058China Department of Pharmaceutical sciences Beijing Institute of Radiation MedicineBeijing 100850China Department of Radiation Oncology Key Laboratory of Cancer Prevention and InterventionThe Second Afliated HospitalCollege of MedicineZhejiang UniversityHangzhou 310058China hangzhou Institute of Innovative Medicine Zhejiang UniversityHangzhou 310058China Jinhua Institute of Zhejiang university Jinhua 321299China National Key Laboratory of Advanced Drug Delivery and Release Systems Zhejiang UniversityHangzhou 310058China

Radiotherapy is a well-established cytotoxic therapy for local solid cancers, utilizing high-energy ionizing radiation to destroy cancer cells. However, this method has several limitations, including low radiation energy deposition, severe damage to surrounding normal cells, and high tumor resistance to radiation. Among various radiotherapy methods, boron neutron capture therapy (BNCT) has emerged as a principal approach to improve the therapeutic ratio of malignancies and reduce lethality to surrounding normal tissue, but it remains deficient in terms of insufficient boron accumulation as well as short retention time, which limits the curative effect. Recently, a series of radiosensitizers that can selectively accumulate in specific organelles of cancer cells have been developed to precisely target radiotherapy, thereby reducing side effects of normal tissue damage, overcoming radioresistance, and improving radiosensitivity. In this review, we mainly focus on the field of nanomedicine-based cancer radiotherapy and discuss the organelle-targeted radiosensitizers, specifically including nucleus, mitochondria, endoplasmic reticulum and lysosomes. Furthermore, the organelle-targeted boron carriers used in BNCT are particularly presented. Through demonstrating recent developments in organelle-targeted radiosensitization, we hope to provide insight into the design of organelle-targeted radiosensitizers for clinical cancer treatment.

关键词： Cancer radiotherapy Organelle-target Radiosensitization Boron neutron capture therapy Nanomedicines

Cu(Ⅱ) Potentiation of Alzheimer Aβ1-40 Cytotoxicity and Transition on its Secondary Structure

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Acta Biochimica et Biophysica Sinica 2006年第11期38卷 765-772页

作者： xue-Ling DAI~1 Ya-xuan SUN~2 Zhao-Feng JIANG~2* 1 college of Life Science,Capital Normal university,beijing 100037,china 2 college of applied sciences and Humanities,beijing Union university,beijing 100083,china college of Life Science Capital Normal UniversityBeijing 100037 China college of applied sciences and Humanities Beijing Union UniversityBeijing 100083 China

Mounting evidence has shown that dyshomeostasis of the redox-active biometals such as Cuand Fe can lead to oxidative stress,which plays a key role in the neuropathology of Alzheimer's disease（AD）.Here we demonstrate that with the formation of Cu（Ⅱ）·Aβ1-40 complexes,copper markedly potentiatesthe neurotoxicity exhibited by β-amyloid peptide （Aβ）.A greater amount of hydrogen peroxide was releasedwhen Cu（Ⅱ）·Aβ1-40 complexes was added to the xanthine oxidase/xanthine system detected by potassiumiodide *** bound to Aβ1-40 was observed by electron paramagnetic resonance（EPR） *** dichroism （CD） studies indicated that copper chelation could cause a structuraltransition of Aβ.The addition of copper to Aβ introduced an increase on β-sheet as well as α-helix,whichmay be responsible for the aggregation of Aβ.We hypothesized that Aβ aggregation induced by copper maybe responsible for local injury in *** interaction between Cu2+and Aβ also provides a possible mechanismfor the enrichment of metal ions in amyloid plaques in the AD brain.

关键词： Alzheimer’s disease Cu(Ⅱ)·Aβ1-40 complex neuron injury Aβ secondary structure

A cross-monotonic cost sharing method for the facility location game with service installation costs

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Science china Mathematics 2009年第11期52卷 2530-2536页

作者： xu dachuan Department of applied Mathematics,beijing university of technology,beijing 100124,china 1. Department of applied Mathematics Beijing University of Technology Beijing 100124 China

In this paper,we consider the metric uncapacitated facility location game with service installation costs. Our main result is an 11-approximate cross-monotonic cost-sharing method under the assumption that the install... 详细信息

关键词： facility location game cross-monotonic cost-sharing method linear programming relaxation 90C27 91A12

Empirical likelihood confidence regions of the parameters in a partially linear single-index model

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Science china Mathematics 2005年第10期48卷 1333-1348页

作者： xuE Liugen~1 & ZHU Lixing~2 1. college of applied sciences,beijing university of technology,beijing 10002.,china 2. Department of Mathematics,Hong Kong Baptist university,Hong Kong,china 1. college of applied sciences Beijing University of Technology 100022 Beijing China 2. Department of Mathematics Hong Kong Baptist University Hong Kong China

In this paper, a partially linear single-index model is investigated, and three empirical log-likelihood ratio statistics for the unknown parameters in the model are suggested. It is proved that the proposed statistics are asymptotically standard chi-square under some suitable conditions, and hence can be used to construct the confidence regions of the parameters. Our methods can also deal with the confidence region construction for the index in the pure single-index model. A simulation study indicates that, in terms of coverage probabilities and average areas of the confidence regions, the proposed methods perform better than the least-squares method.

关键词： partially linear single-index model, empirical likelihood, confidence region, chi-square distribution, coverage probability.

Compositional and Hollow Engineering of Silicon Carbide/Carbon Microspheres as High-Performance Microwave Absorbing Materials with Good Environmental Tolerance

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Nano-Micro Letters 2024年第9期16卷 128-146页

作者： Lixue Gai Yahui Wang Pan Wan Shuping Yu Yongzheng Chen Xijiang han Ping xu Yunchen du MIIT Key Laboratory of Critical Materials technology for New Energy Conversion and Storage School of Chemistry and Chemical EngineeringHarbin Institute of TechnologyHarbin 150001People’s Republic of China Anhui Provincial Laboratory of Advanced Laser technology College of Electronic EngineeringNational University of Defense TechnologyHefei 230037People’s Republic of China

Microwave absorbing materials(MAMs)characterized by high absorption efficiency and good environmental tolerance are highly desirable in practical *** silicon carbide and carbon are considered as stable MAMs under some rigorous conditions,while their composites still fail to produce satisfactory microwave absorption performance regardless of the improvements as compared with the ***,we have successfully implemented compositional and structural engineering to fabricate hollow Si C/C microspheres with controllable *** simultaneous modulation on dielectric properties and impedance matching can be easily achieved as the change in the composition of these *** formation of hollow structure not only favors lightweight feature,but also generates considerable contribution to microwave attenuation *** the synergistic effect of composition and structure,the optimized SiC/C composite exhibits excellent performance,whose the strongest reflection loss intensity and broadest effective absorption reach-60.8 dB and 5.1 GHz,respectively,and its microwave absorption properties are actually superior to those of most SiC/C composites in previous *** addition,the stability tests of microwave absorption capacity after exposure to harsh conditions and Radar Cross Section simulation data demonstrate that hollow SiC/C microspheres from compositional and structural optimization have a bright prospect in practical applications.

关键词： SiC/C composites Compositional engineering Hollow engineering Microwave absorption Environmental tolerance

Empirical likelihood-based inference in a partially linear model for longitudinal data

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Science china Mathematics 2008年第1期51卷 115-130页

作者： xuE LiuGen~(1+) & ZHU LiXing~2 1 college of applied sciences, beijing university of technology, beijing 10002., china 2 Department of Mathematics, Hong Kong Baptist university, Hong Kong, china college of applied sciences Beijing University of Technology Beijing 100022 China Department of Mathematics Hong Kong Baptist University Hong Kong China

A partially linear model with longitudinal data is considered, empirical likelihood to infer- ence for the regression coefficients and the baseline function is investigated, the empirical log-likelihood ratios is proven to be asymptotically chi-squared, and the corresponding confidence regions for the pa- rameters of interest are then constructed. Also by the empirical likelihood ratio functions, we can obtain the maximum empirical likelihood estimates of the regression coefficients and the baseline function, and prove the asymptotic normality. The numerical results are conducted to compare the performance of the empirical likelihood and the normal approximation-based method, and a real example is analysed.

关键词： partially linear model empirical likelihood confidence region longitudinal data 62G05 62G15 62G20

A new DNA algorithm to solve graph coloring problem

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Progress in Natural Science:Materials International 2007年第6期17卷 733-738页

作者： Jiang Xingpeng1, Li Yin2, Meng Ya3 and Meng Dazhi2(1. National Laboratory of Pattern Recognition,Institute of Automation, Chinese Academy of sciences, beijing 100080, china 2. college of applied sciences, beijing university of technology, beijing 10002., china 3. School of Science, beijing Institute of technology, beijing 100081, china) National Laboratory of Pattern Recognition Institute of Automation Chinese Academy of Sciences Beijing 100080 China college of applied sciences Beijing University of Technology Beijing 100022 China School of Science Beijing Institute of Technology Beijing 100081 China

Using a small quantity of DNA molecules and little experimental time to solve complex problems successfully is a goal of DNA computing. Some NP-hard problems have been solved by DNA computing with lower time complexity than conventional computing. However, this advantage often brings higher space complexity and needs a large number of DNA encoding molecules. One example is graph coloring problem. Current DNA algorithms need exponentially increasing DNA encoding strands with the growing of problem size. Here we propose a new DNA algorithm of graph coloring problem based on the proof of four-color theorem. This algorithm has good properties of needing a relatively small number of operations in polynomial time and needing a small number of DNA encoding molecules (we need only 6R DNA encoding molecules if the number of regions in a graph is R).

关键词： DNA computing NP-hard problem graph coloring problem.