关键词： blur   contrast   quality   standard deviation   texture   wavelet  

摘要： Quantification of computed tomography (CT) noise helps in determination of radiation dosage requirements for adequate image quality. Clinical methods used include calculation of the standard deviation (SD) of a selected region of interest (ROI). In industry, wavelet decomposition has been used for image compression while removing high-frequency noise. We evaluated a cohort of 74 consecutive patients referred for coronary artery calcium scoring and quantitated noise within a 16x16 ROI in the ascending aorta using the traditional SD method and also using a two-dimensional dyadic wavelet decomposition method. Clinically, noise has been shown to be proportional to patient weight and also body mass index (BMI), which is a derived value from height and weight. Noise for both methods was plotted against patient parameters of height, weight, waist circumference and calculated BMI. A regression line was calculated and coefficient of determination (CoD) calculated for each. The CoD was better for height, weight, and waist circumference using the wavelet method as compared to the traditional SD method. The wavelet method of quantification of image noise may be an improved method as compared to the SD method. This method could help further refine an imaging system's determination of radiation dosage requirements to obtain a satisfactory quality image.

关键词： complexity of algorithms   database   table algebra  

摘要： Algorithms implementing intersection, union, and difference in table algebras are investigated. Modifications of the most widespread algorithms reducing the amount of computations are proposed. Based on the complexities evaluated in the worst case and on the average for the modified algorithms, the fastest algorithm is found for each operation. A program that experimentally confirms theoretical estimates is developed.

关键词： Robustness   Aircraft routing   Aircraft scheduling   PSO  

摘要： One of the most important airline's products is to determine the aircraft routing and scheduling and fleet assignment. The key input data of this problem is the traffic forecasting and allocation that forecasts traffic on each flight leg. The complexity of this problem is to define the connecting flights when passengers should change the aircraft to reach the final destination. Moreover, as there exists various types of uncertainties during the flights, finding a solution which is able to absorb these uncertainties is invaluable. In this paper, a new robust mixed integer mathematical model for the integrated aircraft routing and scheduling, with consideration of fleet assignment problem is proposed. Then to find good solutions for large-scale problems in a rational amount of time, a heuristic algorithm based on the Simulated Annealing (SA) is introduced. In addition, some examples are randomly generated and the proposed heuristic algorithm is validated by comparing the results with the optimum solutions. The effects of robust vs non-robust solutions are examined, and finally, a hybrid algorithm is generated which results in more effective solution in comparison with SA, and Particle Swarm Optimization (PSO). (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Scheduling   Flexible job shops   Transportation times   Mathematical models   Hybrid imperialist competitive algorithm  

摘要： After the completion of a job on a machine, it needs to be transported to the next machine, actually taking some time. However, the transportation times are commonly neglected in the literature. This paper incorporates the transportation times between the machines into the flexible job-shop scheduling problem. We mathematically formulate the problem by two mixed integer linear programming models. Since the problem is NP-hard, we propose an adaptation of the imperialist competitive algorithm hybridized by a simulated annealing-based local search to solve the problem. Various operators and parameters of the algorithm are calibrated using the Taguchi method. The presented algorithm is assessed by comparing it against two other competitive algorithms in the literature. The computational results show that this algorithm has an outstanding performance in solving the problem. (C) 2016 Elsevier Inc. All rights reserved.

关键词： 形式化方法   递推技术   组合数学   算法设计  

摘要： 算法设计是计算机科学研究的重要领域之一。目前计算机科学处理的大部分数据都是离散的数据,而组合数学是研究离散数据的科学,因此研究以组合数学为基础的算法的可靠性、正确性和生产效率就成为算法设计领域中的关键问题。对于求解组合数学相关的问题,目前存在多种算法设计方法,形式化开发方法是其中之一。形式化方法的本质是基于数学的方法来描述、开发和验证目标软件系统的一种技术,使用形式化方法开发算法程序能有效提高算法程序设计的规范化、自动化程度以及算法的可靠性和正确性。基于递推技术的算法形式化方法在部分形式化或者是完全形式化描述问题程序规约的基础上,通过对问题的程序规约进行数学变换,得到问题求解的递推关系,在此基础上得到最终的算法程序。由于求解问题的递推关系建立在严格数学变换的基础上,因而递推关系的正确性得到了保证,从而也有效确保最终的算法程序的正确性;另外,使用该方法开发算法程序,均是以寻找问题求解序列的递推关系为出发点,先得到较小的子问题的解,再在之前已获得的较小子问题解的基础上直接或间接得到较大问题的解,这样可以避免很多不必要的重复计算,从而有效提高算法程序的效率,并为算法程序的开发提供一条较为统一的途径。本文重点研究了基于递推关系的算法形式化方法在三类典型组合数学问题求解中的应用。本文分析了当前形式化开发方法的需求以及发展状况;介绍了基于递推技术的形式化开发方法的开发语言、开发步骤以及关键技术等,同时研究了它在组合数学问题开发上的有效性;接着,本文针对组合数学问题进行分类研究,使用基于递推技术的形式化方法开发了三类有代表性的组合数学问题:整除问题、排列组合问题以及NP完全问题中的0-1背包变形问题,同时在分析每一类问题形式化开发过程共性的基础上提炼得到了求解该类问题的统一策略,并将其推广到相似问题的求解;最后对基于递推关系的形式化开发方法在组合数学上的应用进行了总结。研究表明,基于递推技术的算法形式化开发方法有效保证了算法程序的正确性,提高了算法程序的执行效率。

关键词： 高中数学   新课程   算法思想  

摘要： 本文主要以算法思想概述作为出发点,并从两方面探讨了算法思想的当代价值。以期为广大高中生形成科学正确的算法思想提供一些参考和意见。

关键词： 数学算法   计算机编程   优化  

摘要： 在社会的进步中,科学技术飞速发展,在计算机领域,则是发展的重心,自第三次工业革命爆发以来,计算机就扮演着举足轻重的角色,而在现今的计算机领域,许多的计算机软件都要靠着编程来实现,计算机编程的好坏也会直接影响计算机软件的工作效率。数学算法,是我国古代数学学科之中的一种精华的内容,它可以将许多的问题汇总归类进行解决,而计算机技术最基础的应用就是数学算法,数学算法的合理运用可以实现对计算机编程的创新和突破,本文旨在讨论数学算法对计算机编程的优化作用。

关键词： 高中数学   算法初步   策略  

摘要： 随着我国信息技术的不断发展,算法引入到了高中数学课程中,并且成为了学生学习的重要内容,对于算法的学习,可以培养学生的逻辑思维能力、理解运算能力.因此本文主要探讨了高中数学算法初步,希望高中生能够学好这部分的内容.

关键词： 教学片断  

摘要： "数学画"教学缘起于低年级数学教学:受认知发展水平影响,低年级儿童对数学文本的认读和数学概念的理解比较困难,借助画图可以帮助儿童学习数学,并能使其爱上数学、探究数学,很好地发展数学思维。"数学画"的表现形式是图画,低年级学生乐于绘画,"画数学"比"写作业"对他们更具吸引力。随着学习的推进和展评课的引导,"数学画"中"非数学"成分逐渐减少,教师应有意识地引导学生在创作中运用箭头、省略

关键词： 三教   数学素养   算法教学   实验研究  

摘要： 全球信息化是21世纪最明显社会特征,算法影响着现代信息技术飞速发展,算法思想对培养学生数学素养就有重要作用。为了培养学生的数学素养,提高数学课堂教学效率,本文采用"教思考"、"教体验"、"教表达"(简称"三教")对"算法初步"教学实验研究。实验结果表明,使用"三教"理念教学效果优于传统教学,进而对提高高中数学算法课堂教学效率具有一定的参考和借鉴作用。