Outlier-DivideConquer:近似聚集查询中离群分治取样算法

取样是一种通用有效的近似技术,利用取样技术进行近似聚集查询处理是决策支持系统和数据挖掘实现技术中的常用方法.如何正确有效地给出近似查询结果并最小化近似查询误差是近似查询处理的关键和目标.在深入研究近似聚集查询取样方法的基础上,本文提出了一个有误差确界且只需单遍扫描数据集的离群分治取样Outlier-DivideConquer算法,该算法在聚集属性内部存在高方差分布时能克服随机均匀取样局限,可显著降低近似查询误差,且执行效率优于同类算法.最后通过与传统均匀取样算法的实验比较验证了Outlier-DivideConquer算法的有效性和正确性.

Comparison of perioperative parameters in one-handed rotational phacoemulsification versus conventional phacoemulsification and femtosecond laser-assisted cataract surgery

AIM:To compare perioperative parameters of one-handed rotational phacoemulsification technique(one-handed phaco-roll)with each of other two techniques,“Divide et Conquer”and femtosecond laser-assisted cataract surgery(FLACS)METHODS:In this retrospective and comparative cohort study,eyes with uncomplicated cataract(nuclear density grade 2 to 3)treated routinely with one-handed phacoroll(n=23;Group 1)or“Divide et Conquer”(n=23;Group 2)or FLACS(n=23;Group 3)were enrolled.Intraoperative parameters including effective phaco-time(EPt),ultrasound time(USt),aspiration time,surgical time,phacoemulsification(phaco)-power,balanced salt solution(BSS)use,cumulative dissipated energy(CDE)were recorded and compared.Clinical outcomes including best corrected visual acuity(BCVA),corneal endothelial cell density(ECD),endothelial cell loss(ECL),central corneal thickness(CCT)and central macular thickness(CMT),were assessed and compared pre-operatively and at 1mo after surgery.RESULTS:Aspiration and surgical time,and BSS used were lower in Group 1(P<0.01)than other groups.EPt,phaco-power and CDE were lower in Group 1(P<0.05)than Group 2 but not significantly different from Group 3.In Group 1,USt was lower(P<0.05)than Group 2 but higher(P<0.05)than Group 3.BCVA improved in all groups without significant difference between Group 1 and the other ones.No significant differences regarding all post-operative morphologic outcomes(ECD,ECL,CCT,CMT)were reported.No clinical complications occurred.CONCLUSION:One-handed phaco-roll seems to be less time-consuming than“Divide et Conquer”and FLACS and less energy-consuming than“Divide et Conquer”.Furthermore,one-handed phaco-roll seems to have an equal safety profile compared to the other two techniques.

Composition control and temperature inferential control of dividing wall column based on model predictive control and PI strategies

The dividing wall column （DWC） is considered as a major breakthrough in distillation technology and has good prospect of industrialization. Model predictive control （MPC） is an advanced control strategy that has acquired extensive applications in various industries. In this study, MPC is applied to the process for separating ethanol, n-propanol, and n-butanol ternary mixture in a fully thermally coupled DWC. Both composition control and tem- perature inferent/al control are considered. The multiobjective genetic algor/thm function ＂gamult/obj＂ in Matlab is used for the weight tuning of MPC. Comparisons are made between the control performances of MPC and PI strategies. Simulation results show that although both MPC and PI schemes can stabilize the DWC in case of feed disturbances, MPC generally behaves better than the PI strategy for both composition control and tempera- ture inferential control, resulting in a more stable and superior performance with lower values of integral of squared error （ISE）.

23-Gauge Pars Plana Vitrectomy Alone by a Bimanual Technique for the Removal of Dense Posteriorly Dislocated Crystalline Lens

Background: We sought to verify the efficacy and safety of transconjunctival 23-gauge pars plana vitrectomy (PPV) alone by our bimanual technique for the removal of dense posteriorly dislocated crystalline lens. Methods: A retrospective, noncomparative, interventional study of 31 consecutive cases of patients who underwent 23-gauge PPV alone for the removal of dense posteriorly dislocated crystalline lens following complicated cataract surgeries using our bimanual technique was conducted. The main outcomes measured included best-corrected visual acuity (BCVA), preoperative intraocular pressure (IOP), postoperative IOP and postoperative complications. Results: In all 31 cases included in this study, those dense posteriorly dislocated crystalline lenses were successfully removed. The enrolled patients consisted of 17 males and 14 females with a mean age of (75.84 ± 6.17) years (range 59 - 90). The mean follow-up length was (7.61 ± 1.87) months with a range of 6 months to 1 year. The mean preoperative BCVA was 0.22 ± 0.11 logMAR system, and the postoperative BCVA was 0.33 ± 0.07 logMAR system after 6 months of follow-up. The mean operative time was 46.32 ± 4.80 minutes with a range of 38.00 to 57.00 minutes. All of the conjunctival incisions self-closed within the first week with no wound leakage or hemorrhage. The postoperative complications were relatively rare. Conclusions: The removal of dense posteriorly dislocated crystalline lens might be a challenge for micro-incision vitrectomy. Our bimanual technique was proved to be an effective and safe method for those particular dense lenses using 23-gauge alone.

Bridging Digital Divide for English Learners at Chinese Secondary Schools

This article reviews the concept of digital divide and particularly discusses the digital divide among K-12 students in rural and urban China,as well as the e-learning strategies initiated by the Chinese government that were designed to minimize this digital divide in China.This article concludes by explaining the issue of skills on effective e-learning and correspondingly making suggestions for English teachers in K-12 schools in China.

Optimal constrained multi-degree reduction of Bézier curves with explicit expressions based on divide and conquer

We decompose the problem of the optimal multi-degree reduction of Bézier curves with corners constraint into two simpler subproblems, namely making high order interpolations at the two endpoints without degree reduction, and doing optimal degree reduction without making high order interpolations at the two endpoints. Further, we convert the second subproblem into multi-degree reduction of Jacobi polynomials. Then, we can easily derive the optimal solution using orthonormality of Jacobi polynomials and the least square method of unequally accurate measurement. This method of 'divide and conquer' has several advantages including maintaining high continuity at the two endpoints of the curve, doing multi-degree reduction only once, using explicit approximation expressions, estimating error in advance, low time cost, and high precision. More importantly, it is not only deduced simply and directly, but also can be easily extended to the degree reduction of surfaces. Finally, we present two examples to demonstrate the effectiveness of our algorithm.

Performance Prediction Model for Parallel Computing on Network of Workstation

In order to effectively program Parallel Computing on NOW (Network of workstation),users must be able to evaluate how well the system performs for a given application.In this paper,we present an framework that can be used to evaluate tree structured computing on NOW.Based on this framework,we derive a model for the famous parallel programming paradigm divide and conquer.We discuss how this model can be used to evaluate performance and how it can be used to restructure the application to improve performance.

An Optimal Parallel Algorithm for the Knapsack Problem Based on EREW

A new parallel algorithm is proposed for the knapsack problem where the method of divide and conquer is adopted. Based on an EREW-SIMD machine with shared memory, the proposed algorithm utilizes O(2 n/4 ) 1-ε processors, 0≤ ε ≤1, and O(2 n/2 ) memory to find a solution for the n -element knapsack problem in time O(2 n/4 (2 n/4 ) ε) . The cost of the proposed parallel algorithm is O(2 n/2 ) , which is an optimal method for solving the knapsack problem without memory conflicts and an improved result over the past researches.

A Divide-and-Conquer Strategy for Embedding a Distance-Net Point Set Into E^n and Its Application

A divide-and-conquer strategy is given for embedding a distance-net point set into Euclidean space En, and the problem of embedding a bounded distance-net point set into E3 and its application to the macromolecular conformation with Nuclear Magnetic Resonance data are discussed.

Ensemble Neural Network in Classifying Handwritten Arabic Numerals

A method has been proposed to classify handwritten Arabic numerals in its compressed form using partitioning approach, Leader algorithm and Neural network. Handwritten numerals are represented in a matrix form. Compressing the matrix representation by merging adjacent pair of rows using logical OR operation reduces its size in half. Considering each row as a partitioned portion, clusters are formed for same partition of same digit separately. Leaders of clusters of partitions are used to recognize the patterns by Divide and Conquer approach using proposed ensemble neural network. Experimental results show that the proposed method recognize the patterns accurately.

灌溉机器人全覆盖路径规划方法

灌溉机器人全覆盖行动的各个任务具有较为明显的空间并行性,随着全覆盖范围扩大,在对覆盖区域进行分解阶段,需要充分考虑将整个区域空间分解为哪些区域。但是,灌溉机器人受到视觉感知区域限制,准确匹配和衔接路块间最近端点的难度较大,导致局部路点的连通和线路衔接出现差错,难以有效全覆盖。为了有效解决这一问题,提出一种灌溉机器人全覆盖路径规划方法。通过快速搜索随机算法展开需要覆盖区域的边界检测,考虑视觉传感器的感知范围受限因素,采用灰度质心法展开区域视图边界提取,根据提取结果建立地图。在地图上建立线段序列,通过曼哈顿最小距离原则连接地图上的部分路径线段,形成多个弓形线路块。使用分治算法匹配和衔接各个弓形线路块间最近端点对,引入改进A*算法对全局以及局部路点的连通和线路衔接,实现灌溉机器人的全覆盖路径规划。实验结果表明:针对简单灌溉区域,该方法的路径重复率为0.041%,灌溉覆盖率为98.90%;针对复杂灌溉区域,该方法的路径重复率为0.017%,灌溉覆盖率为99.87%。这说明针对不同的灌溉环境,该方法均可以实现理想的路径规划,不仅可以最大限度地实现全覆盖,并有效地减少路径冗余程度,可以获取理想的灌溉机器人全覆盖路径规划方案。

共同富裕背景下数字基础设施建设对居民收入水平与地区收入差距的影响

“宽带中国”试点政策有助于扩大农村劳动力就业。数字基础设施建设是推动共同富裕和缩小地区收入差距的重要路径。基于2005-2022年292个地级市(未含我国香港地区、澳门地区、台湾地区)的数据,使用双重差分法分析数字基础设施建设对居民收入水平和地区收入差距的影响及其机制,可以发现:数字基础设施建设能显著提高居民收入水平并缩减地区收入差距,这一结论在考虑交叠DID偏误、替换被解释变量、替换解释变量后依然成立。数字基础设施建设能通过促进技术创新、产业结构升级对共同富裕产生积极影响。在城镇化率高的地区与城镇化率低的地区,数字基础设施建设均能缩减地区收入差距,但是数字基础设施建设对城镇化率低的地区的居民收入水平的促进作用小于其对城镇化率高的地区的居民收入水平的促进作用。数字基础设施建设对周边城市的居民收入水平具有显著的正向影响,数字基础设施建设还能降低周边地区的地区收入差距。为进一步发挥数字基础设施建设对共同富裕的促进作用,政府应加大对数字基础设施建设和宽带网络覆盖的投资力度,给予企业在数字基础设施建设中的税收减免,加强对数字基础设施建设的监管,加大对数字技术人才的培养力度。

基于改进算法YOLOv5+的混凝土轨枕裂纹检测

基于既有研究成果在对混凝土轨枕裂纹检测效率不足的基础上,提出一种改进算法YOLOv5+,主要以YOLOv5网络模型为基础,对混凝土轨枕裂纹进行高效检测。首先,采用分治标签的策略来增大裂纹在标签中的实际占比,从而解决混凝土轨枕裂纹尺度变化大的问题,使网络更利于提取有效特征;其次,将YOLOv5网络结构中SPP模块的最大池化层改为平均池化层,减少裂纹漏检的现象;同时,在YOLOv5骨干网络中嵌入SE注意力模块(Squeeze and Excitation,SE)提高对细小裂纹的检测能力;最后,结合新的检测尺度与特征融合网络,降低微小裂纹的漏检现象。实验结果表明,以YOLOv5网络模型为基础的改进算法YOLOv5+,除了召回率Recall变化不大外,精确率Precision提高6.5%,平均精度均值mAP提升8%,帧率FPS也有所提升,能够满足实时性的检测需求。

元宇宙应用引发的人文风险与应对策略

通过深入探究元宇宙应用带来的人文风险,为元宇宙的数字治理准则阐发提供崭新视角和有效方法。从元宇宙关键技术出发,详细论述了元宇宙带来的主要包括自由风险、平等风险、公正风险和法治风险在内的群体风险,以及主要包括主体性弱化风险、个体能力损伤风险、权利遭侵犯风险和身心健康风险在内的个体风险,重点阐述了元宇宙技术的全周期中包括技术研发、技术应用和技术分配的三个关键阶段,并基于我国现有的元宇宙治理方案,针对这三个技术维度的风险特征提出多样多元的风险防控策略。

基于优先级辅助分治策略的多星多站测控资源分配方法

随着商业测控的不断发展和在轨运行的商业卫星数量增多,针对商业地面测控资源有限,以及各种临时的任务需求导致的中低轨卫星测控资源紧张的问题,文章提出了一种基于优先级辅助分治策略的多星多站测控资源分配方法。经仿真分析,结果表明:该方法能够简单灵活的以较少的计算量和内存开销实现分配方案求解,该求解方案能够保证在优先级较高的卫星和任务优先获得调度资源的前提下,最大限度的为卫星和任务提供测控资源,可为测控资源调度系统建设提供参考。

基于误差分治的神经网络验证

随着神经网络技术的快速发展,其在自动驾驶、智能制造、医疗诊断等安全攸关领域得到了广泛应用,神经网络的可信保障变得至关重要.然而,由于神经网络具有脆弱性,轻微的扰动经常会导致错误的结果,因此采用形式化验证的手段来保障神经网络安全可信是非常重要的.目前神经网络的验证方法主要关注分析的精度,而易忽略运行效率.在验证一些复杂网络的安全性质时,较大规模的状态空间可能会导致验证方法不可行或者无法求解等问题.为了减少神经网络的状态空间,提高验证效率,提出一种基于过近似误差分治的神经网络形式化验证方法.该方法利用可达性分析技术计算非线性节点的上下界,并采用一种改进的符号线性松弛方法减少了非线性节点边界计算过程中的过近似误差.通过计算节点过近似误差的直接和间接影响,将节点的约束进行细化,从而将原始验证问题划分为一组子问题,其混合整数规划(MILP)公式具有较少的约束数量.所提方法已实现为工具NNVerifier,并通过实验在经典的3个数据集上训练的4个基于ReLU的全连接基准网络进行性质验证和评估.实验结果表明,NNVerifier的验证效率比现有的完备验证技术提高了37.18%.

Parallel divide and conquer bio-sequence comparison based on Smith-Waterman algorithm

Tools for pair-wise bio-sequence alignment have for long played a central role in computation biology. Several algorithms for bio-sequence alignment have been developed. The Smith-Waterman algorithm, based on dynamic programming, is considered the most fundamental alignment algorithm in bioinformatics. However the existing parallel Smith-Waterman algorithm needs large memory space, and this disadvantage limits the size of a sequence to be handled. As the data of biological sequences expand rapidly, the memory requirement of the existing parallel Smith- Waterman algorithm has become a critical problem. For solving this problem, we develop a new parallel bio-sequence alignment algorithm, using the strategy of divide and conquer, named PSW-DC algorithm. In our algorithm, first, we partition the query sequence into several subsequences and distribute them to every processor respectively, then compare each subsequence with the whole subject sequence in parallel, using the Smith-Waterman algorithm, and get an interim result, finally obtain the optimal alignment between the query sequence and subject sequence, through the special combination and extension method. Memory space required in our algorithm is reduced significantly in comparison with existing ones. We also develop a key technique of combination and extension, named the C&E method, to manipulate the interim results and obtain the final sequences alignment. We implement the new parallel bio-sequences alignment algorithm, the PSW-DC, in a cluster parallel system.

大数据序贯检验方法及其应用

分布的一致性检验在很多领域中得到了广泛的应用,它是统计学在众多应用中的一个基本主题。然而,随着大数据时代的到来,各个科学领域收集存储了丰富的数据。这些数据规模庞大、类型多样、结构复杂、更新速度快,传统的分布一致性检验方法受数据规模和存储方式的影响在处理和分析这类数据时面临着巨大的挑战。目前,分治策略是解决这类问题的主要方法,其核心思想是采用分布式框架对每个节点数据的计算结果进行集成以获取最终的结果。在处理大规模分布一致性检验问题时,这种对所有节点的检验结果进行集成的方式并不高效,特别是在数据分布存在明显差异时这种方式往往会增加检验的成本。因此,基于序贯检验的思想通过合理设置检验问题的“误差区域”对已有的分治策略进行优化,提出了一种分布式序贯检验方法。该方法在检验过程中不集成所有的节点数据,而是根据当前收集到的节点数据实时调整后续的决策,通过这种方式能够实现在不使用全部节点数据的前提下,做出正确的检验结果。模拟实验和实例分析结果表明:相比于已有的分治策略检验方法,所提出的分布式序贯检验方法能够在保证检验水平与功效的同时,提高分布式检验的计算效率,为解决临床试验、工业检验等领域中大规模数据检验成本高的问题提供了方法支撑。

基于三阶段优化的大无人机辅助小无人机物流配送方法

无人机包裹配送是近年来获得广泛关注的新配送方式,相比于基于地面车辆的配送方式,多无人机配送具有高效率、强时效性和灵活机动等优势.因此,本文提出了一种全新的异构多无人机物流配送模式,即单架大无人机辅助多架小无人机进行的包裹配送.该配送模式的新特点是:大无人机携带多架小无人机到配送区域放飞,多架小无人机分别配送所指派区域的包裹,每架无人机在一次航行中可配送多个包裹,多架小无人机同时进行配送.为了高效的求解这个新配送问题,文章设计了一种基于分而治之三阶段的迭代优化算法,第1阶段采用聚类方法对客户点聚类并生成初始解;第2阶段提出一种改进的变邻域搜索算法优化大无人机路径;第3阶段使用动态规划方法优化小无人机路径.这3个阶段不断迭代优化直至满足停止准则.为了验证所提出算法的有效性,在大量算例上进行了实验测试,实验结果展示了所提出算法的求解效率和目标函数值显著优于其他对比算法.文章所提出的新的异构多无人机配送模式及其求解方法,为解决现代物流配送的痛点问题提供了一种全新方式与决策依据.

四针汉诺塔问题的算法设计

对传统三针汉诺塔问题的递归求解算法进行简要分析和研究,在此基础上对四针汉诺塔问题进行深入研究,给出四针汉诺塔最优移动次数的算法,并通过穷举法分析提炼出最优参数的取值。