NDSMMV——A New Dynamic Selection Strategy of Materialized Views for Multi-Dimensional Data

物化视图的选择策略是数据仓库研究的重要问题之一.通过深入研究提出了一种多维数据集中物化视图动态选择的新策略——NDSMMV,包括候选视图生成算法CVGA、物化视图选择算法IGA、物化视图调整算法MAMV和物化视图动态调整算法DMAMV.CVGA基于多维数据格生成候选视图集,对候选视图数量进行压缩以减少后续算法的视图空间搜索代价和时间复杂度;IGA基于视图查询、视图维护和存储空间三元评价标准在候选视图集上进行物化视图的选择;MAMV基于物化视图选择过程已选视图的收益变化情况对物化视图进行进一步调整以提高查询的响应性能;DMAMV定时地判断查询视图类型分布是否变化来决定是否进行物化视图的动态调整,从而避免了物化视图集的"抖动".理论分析和实验结果表明该策略是有效可行的.The selection strategy of materialized view is one of the important issues of data warehouse research.Its goal is to elect a group of materialized views,which could cut down the cost of the query greatly on the basis of the limited storage space.The cost model is proposed at first.Then,a new dynamic selection strategy of materialized views for multi-dimensional data(NDSMMV)is presented,which is composed of four algorithms:CVGA(candidate view generation algorithm),IGA(improved greedy algorithm),MAMV(modulation algorithm of materialized views)and DMAMV(dynamic modulation algorithm of materialized views).CVGA generates the candidate view set based on multi-dimensional data lattice,which reduces the number of candidate views to decrease the space search cost and time consumption of the following algorithm.IGA selects materialized views taking account of view query,view maintenance and space constraint.MAMV modulate the materialized views according to the change of the materialized view profit,which improves the capability of querying materialized views.DMAMV uses the sample space to judge whether it is necessary to change the view set which can avoid sharp dither.The comparative experiment indicates that NDSMMV operates more effectively than BPUS and FPUS in the respect that CVGA reduces the amount of views beforehand.IGA selects the materialized views quickly,MAMV modulates the materialized views accurately,and the query expense decreases further with the modulation of the DMAMV on line,which validates the efficiency of NDSMMV.国家自然科学基金项目(50604012);; 福建省高新技术研究计划重点项目(2003H043)~

专题:中国非正规经济(下)

李明欢以非正规雇佣为主要内涵的非正规经济之所以能够在跨国领域大行其道,根源之一在于全球化正如同由跨国资本把握方向盘的巨型“压路机“,力图突破一切不利于其扩张之国境边界,朝着政治和

Approaches for Selecting Views to Materialize Based on Multi-Maintenance Strategy

物化视图是数据仓库环境中提高 OLAP 查询效率的重要手段,因此,物化视图的选择是数据仓库设计中重要的决策之一。本文提出的物化视图选择方法目标是选择合适的视图进行物化,使得查询处理的总代价和物化视图的维护代价最低,提出了物化视图收益模型,并在此基础上基于视图的多维护策略提出了物化视图选择的方法:基于增量和重计算的物化视图选择算法 IRMVS、基于增量策略的物化视图选择算法 IMVS 和基于重计算策略的物化视图选择算法 RMVS 和基于增量策略的物化后代视图选择算法 IMDVS,理论分析和实验表明这些算法是有效可行的。A data warehouse stores materialized views,with the purpose of efficiently implementing OLAP queries or decision-support.Hence,selecting views to materialize is one of the most important decisions in designing a data ware- house.In this paper,we present a framework for analyzing the issues ,which goal is to select an appropriate set of views so that the sum cost of processing queries and maintaining the materialized views is minimized.Based on the proposed benefit model,we proposed two approaches.The target of first approach is to solve the problem considering both multi- query optimization and the maintenance process optimization.In this approach,we present three algorithms:IRMVS, IMVS and RMVS.The second approach uses a simple search strategy that can cut down the time complexity to a line- ar.The comparative experiment indicates that these algorithms are efficient and feasible.国家自然科学基金项目(50474033);; 福建省自然科学基金项目(A0310008);; 福建省高新技术研究开放计划重点项目(2003H043)

医用α-半水硫酸钙粉体及硫酸钙人工骨材料的制备方法

本发明公开了一种医用α-半水硫酸钙粉体及硫酸钙人工骨材料的制备方法，属于医用生物材料领域。本发明采用在包含氯化钙、转晶剂与蒸馏水的反应液中加入与蒸馏水体积比为0.01～2的无水乙醇，使二水硫酸钙在反应液中部分脱去结晶水制得α-半水硫酸钙，由于无水乙醇的改性作用，有效地改善了α-半水硫酸钙粉体的晶粒形貌和尺寸，得到高纯度，晶体结构和粒度分布均匀，等轴或接近等轴的α-半水硫酸钙粉体，该α-半水硫酸钙粉体与固化液混合固化后制得的医用硫酸钙人工骨材料能够有效提高抗压强度、延长降解时间，并且改善生物学性能，因此是一种性能良好的医用硫酸钙人工骨材料，在医用骨移植与骨修复技术领域具有良好的应用前景

α半水硫酸钙复合功能化多壁碳纳米管骨修复材料生物相容性

旨在评价α 半水硫酸钙复合功能化多壁碳纳米管骨修复材料的生物相容性，为后期临床实验奠定基 础。分别采用兔L929 成纤维细胞与材料浸提液以及材料片剂与兔骨髓基质干细胞复合培养，在不同时段运用 倒置显微镜观察，MTT 检测，扫描电子显微镜分析等手段，观察材料对细胞的相容性；进行急性、亚急性毒 性实验，肌肉植入实验，骨植入实验等，观察材料对组织的相容性。结果表明，L929 成纤维细胞在材料浸提 液中生长良好，MTT 检测与对照组无显著差异 (P＞0.05)；扫描电子显微镜结果显示，细胞能在材料上黏附并 增殖；体内实验表明材料对机体无毒，无致敏性，组织相容性佳。α 半水硫酸钙/碳纳米管复合材料表现出的 良好生物相容性，有望在骨组织工程中得到广泛运用

Effect of organic-inorganic composite binding materials on steel structure fire retardant coating

[中文文摘]以硅酸盐类凝胶材料为主粘接剂,采用有机无机复合方法,通过聚合物和改性水玻璃对主粘接剂进行改性,使涂层兼具水泥的刚性和聚合物的柔性,提高其粘结性、耐水性和柔韧性,克服涂层高温或骤冷条件下易爆裂、脱落,常温下易粉化、受潮、附着力差等缺点;理化性能测试和高温燃烧实验表明,防火涂层具有优良的耐火性能,与基材粘接性能良好。[英文文摘]In the steel structure fire-retardant coating silicate gel materials is as primary binder,which is modified by polymer and modified sodium silicate using organic-inorganic compound method.After modification,the coating possesses stiffness of cement and flexibility of polymer at the same time.The adhesive strength of coating increases as well as resistivity against water and flexibility.The coating is not easy to burst or scale off under high temperature or shock cooling condition.It is also hard to be chalked,wetted under room temperature condition. The physicochemical properties testing and combustion experiments prove that modified fire-ret ardant coating has good fireproof performance, and high adhesive strength to protected backing .福建省科技重点项目(2007T0013,2006I0026); 厦门市科技计划项目(3502Z20073006

Prediction of Energy Resolution in the JUNO Experiment

International audienceThis paper presents the energy resolution study in the JUNO experiment, incorporating the latest knowledge acquired during the detector construction phase. The determination of neutrino mass ordering in JUNO requires an exceptional energy resolution better than 3% at 1 MeV. To achieve this ambitious goal, significant efforts have been undertaken in the design and production of the key components of the JUNO detector. Various factors affecting the detection of inverse beta decay signals have an impact on the energy resolution, extending beyond the statistical fluctuations of the detected number of photons, such as the properties of liquid scintillator, performance of photomultiplier tubes, and the energy reconstruction algorithm. To account for these effects, a full JUNO simulation and reconstruction approach is employed. This enables the modeling of all relevant effects and the evaluation of associated inputs to accurately estimate the energy resolution. The study reveals an energy resolution of 2.95% at 1 MeV. Furthermore, the study assesses the contribution of major effects to the overall energy resolution budget. This analysis serves as a reference for interpreting future measurements of energy resolution during JUNO data taking. Moreover, it provides a guideline in comprehending the energy resolution characteristics of liquid scintillator-based detectors

Measurement of integrated luminosity of data collected at 3.773 GeV by BESIII from 2021 to 2024

We present a measurement of the integrated luminosity e+e- of collision data collected by the BESIII detector at the BEPCII collider at a center-of-mass energy of Ecm = 3.773 GeV. The integrated luminosities of the datasets taken from December 2021 to June 2022, from November 2022 to June 2023, and from October 2023 to February 2024 were determined to be 4.995±0.019 fb-1, 8.157±0.031 fb-1, and 4.191±0.016 fb-1, respectively, by analyzing large angle Bhabha scattering events. The uncertainties are dominated by systematic effects, and the statistical uncertainties are negligible. Our results provide essential input for future analyses and precision measurements