粤港澳大湾区经济中心对粤北地区的经济辐射作用分析——以清远市为例     

周婷 《清远职业技术学院学报》2020,(2):12-16

发挥经济中心对周边地区的经济辐射作用对一个区域的经济协同发展具有重要意义。粤北地区特别是清远市可以说是藏在粤港澳大湾区经济焦点下的盲点。借助地理距离优势,跨越发展鸿沟,使周边地区与粤港澳大湾区实现融合式互动和一体化发展,是一个具有重要研究价值的问题。可以将粤港澳大湾区及其周边地区作为一个城市群,描述和测算其基本发展现状及经济分布格局,探索经济辐射的必要性与可能的辐射路径。  相似文献   

航运技术进步与技术替代优化理论     

李玉如 《上海海事大学学报》1992,(2)

本文论述了技术进步是现代国际航运发展的根本动力。并运用等产量、等成本两曲线及其相关性质和边际理论,就技术进步要解决的生产要素替代和最佳组合问题进行了讨论。同时,还就航运活动的长期年平均单位成本的变化特征及其所要求的船舶替代,结合航运实际,从优化角度作了探讨。  相似文献   

西非—中国航线原油远洋运输方案优化     

周晓玲  王震  肖文涛  许国栋 《上海海事大学学报》2017,38(1):31-36

为满足西非—中国航线的原油远洋运输方案的时效性要求,以油船运费、滞期费和靠港费之和最低为目标函数,以供需平衡、港口水深和装卸时间为约束条件,求解一个包含船型组合、装/卸港航线组合、油种替换、批次拆分等多决策变量的大规模NP(Non-deterministic Polynomial)难问题.采用差分进化算法进行求解.为提高求解速度,采用双染色体编码、基因组压缩编码、船型与拼装变量隐式联锁、配送油种比对解码等方法,进行供需平衡约束,降低问题规模,并缩减问题的"劣质解空间",提高差分进化算法的搜索时效.利用提出的算法对中国石化某月度西非—中国航线实际原油远洋运输方案进行优化,得到优化方案平均用时约5 min,可节约运费50余万美元.  相似文献   

我国低碳航运产业价值链的结构乘数效应     

甘爱平  詹凌晨  真虹  张婕姝 《上海海事大学学报》2016,37(3):47-51

针对航运低碳投资支出巨大的问题，运用结构性乘数，对我国用于低碳航运产业价值链中的支出产生的乘数效应进行研究.由两部门计算的简单投资乘数为1.547 7，由四部门计算的投资乘数均值为1.293 1.从长期看，乘数效应反映出航运低碳产业的投资收益大于投资支出，对航运业低碳减排具有现实和经济意义.  相似文献   

A comparison of methods to determine bilateral asymmetries in vertical leg stiffness     

Sean J. Maloney  Iain M. Fletcher  Joanna Richards 《Journal of sports sciences》2016,34(9):829-835

Whilst the measurement and quantification of vertical leg stiffness (K_vert) asymmetry is of important practical relevance to athletic performance, literature investigating bilateral asymmetry in K_vert is limited. Moreover, how the type of task used to assess K_vert may affect the expression of asymmetry has not been properly determined. Twelve healthy males performed three types of performance tasks on a dual force plate system to determine K_vert asymmetries; the tasks were (a) bilateral hopping, (b) bilateral drop jumping and (c) unilateral drop jumping. Across all the three methods, K_vert was significantly different between compliant and stiff limbs (P < 0.001) with a significant interaction effect between limb and method (P = 0.005). Differences in K_vert between compliant and stiff limbs were ?5.3% (P < 0.001), ?21.8% (P = 0.007) and ?15.1% (P < 0.001) for the bilateral hopping, bilateral drop jumping and unilateral drop jumping methods, respectively. All the three methods were able to detect significant differences between compliant and stiff limbs, and could be used as a diagnostic tool to assess K_vert asymmetry. Drop jumping tasks detected larger K_vert asymmetries than hopping, suggesting that asymmetries may be expressed to a greater extent in acyclic, maximal performance tasks.  相似文献   

Dribbling determinants in sub-elite youth soccer players     

Matteo Zago  Andrea Gianluca Piovan  Isabella Annoni  Daniela Ciprandi  F. Marcello Iaia 《Journal of sports sciences》2016,34(5):411-419

Dribbling speed in soccer is considered critical to the outcome of the game and can assist in the talent identification process. However, little is known about the biomechanics of this skill. By means of a motion capture system, we aimed to quantitatively investigate the determinants of effective dribbling skill in a group of 10 Under-13 sub-elite players, divided by the median-split technique according to their dribbling test time (faster and slower groups). Foot-ball contacts cadence, centre of mass (CoM), ranges of motion (RoM), velocity and acceleration, as well as stride length, cadence and variability were computed. Hip and knee joint RoMs were also considered. Faster players, as compared to slower players, showed a 30% higher foot-ball cadence (3.0 ± 0.1 vs. 2.3 ± 0.2 contacts · s^?1, P < 0.01); reduced CoM mediolateral (0.91 ± 0.05 vs. 1.14 ± 0.16 m, P < 0.05) and vertical (0.19 ± 0.01 vs. 0.25 ± 0.03 m, P < 0.05) RoMs; higher right stride cadence (+20%, P < 0.05) with lower variability (P < 0.05); reduced hip and knee flexion RoMs (P < 0.05). In conclusion, faster players are able to run with the ball through a shorter path in a more economical way. To effectively develop dribbling skill, coaches are encouraged to design specific practices where high stride frequency and narrow run trajectories are required.  相似文献   

泉州市区"城中村"邻里关系的地理学分析     

李子蓉  刘慧玲  黄婉清  王莹 《泉州师范学院学报》2007,25(2):91-96

采用面向对象分析法OOA(object-oriented analysis)对影响泉州中心市区城中村的邻里关系进行详实的社会调查和探究,通过调研试图基本了解和掌握城中村居民的信息,对邻里关系特征进行描述和分析.文章通过对泉州中心市区中典型的“城中村”进行实地考察,借鉴国内外城中村改造的相关研究,从地理学、社会学等相关学科的角度出发进行分析思考;在此基础上就构建和谐的邻里关系进行探讨.  相似文献   

平乐县城船商老街文化旅游创意开发研究     

梁福兴 《南宁职业技术学院学报》2011,(6):76-79

随着旅游向生态化、文化性和内涵式方向发展,旅游者不再局限于单纯追寻观光游览性质的风景名胜区,逐步转向追求原生态的文化意境和休闲情调,讲究文化与旅游相互交融的体验享受。广西平乐县地处大桂林山水文化旅游圈最南端,旅游资源丰富,文化类型多样,具有创新创意发展特色文化旅游的独特优势。县城船商老街是平乐县城旅游资源和旅游产业核心,合理利用千年州府、船商老街文化资源和桂林阳朔旅游市场优势,通过创意性景观环境改造、旅游功能分区和活动项目策划,可迅速盘活船商老街的文化旅游资源。  相似文献   

滚翻垫球后“再后倒”现象的讨论     

王凤玲 《石家庄学院学报》2000,(4)

对滚翻垫球后“再后倒”现象进行理论分析 ,可找出出现问题的根源 ,以便在教学中解决这一问题  相似文献   

地方农林院校物理实验教学示范中心建设实践     

戴朝卿  赵丽华  储修祥  王悦悦 《实验室研究与探索》2011,30(12):87-89,107

从转变实验教学观念、建立科学实验教学体系、规范实验室管理、改善实验环境等方面介绍了浙江农林大学省级物理实验教学示范中心建设的实践.实验教学示范中心的建设过程贯穿“高等教育生态化”理念,构建并实施了以“三层四模”为核心、“两个平台”为栽体的生态化实验教学新体系;建设了由网络教学资源平台和网络管理服务平台组成的物理实验网络信息教学平台;创建了实验中心内部环境以及内外部环境关系生态化的实验教学环境.初步实践表明,示范中心的建设提高了实验教学效益,“拉动”了实验教学水平的提高,实现了教与学的双赢.  相似文献