A new photonic bandgap cover for a patch antenna with a photonic bandgap substrate

INTRODUCTIONInvestigationofphotonicbandgap(PBG)materialsiscurrentlyoneofthemostactivefron-tiersinengineeringandphysics.PBGmaterialshaverecentlyemergedasanewmultidisciplinaryfieldofstudy(Kesleretal.,1996;Yablonovitch,1994;SimovskiandHe,2001).APBGstructurecanhaveabandgapwithinwhichelectromagnetic(EM)wavepropagationispreventedinalldirec-tions(Joannopoulosetal.,1997;Ozbayetal.,1994).Foratwo-dimensionalPBGmaterial,thepropagationofanEMwavewithinitsbandgapispreventedinalldirectionswithin…     

Fractions as the Coordination of Multiplicatively Related Quantities: A Cross-Sectional Study of Children's Thinking

Although equal sharing problems appear to support the development of fractions as multiplicative structures, very little work has examined how children's informal solutions reflect this possibility. The primary goal of this study was to analyze children's coordination of two quantities (number of people sharing and number of things being shared) in their solutions to equal sharing problems and to see to what extent this coordination was multiplicative. A secondary goal was to document children's solutions for equal sharing problems in which the quantities had a common factor (other than 1). Data consisted of problem-solving interviews with students in 1st, 3rd, 4th, and 5th grades (n=112). We found two major categories of strategies: (a) Parts Quantities strategies and (b) Ratio Quantities strategies. Parts quantities involved children's partitions of continuous units expressed in terms of the number of pieces that would be created. Ratio quantities involved children's creation of associated sets of discrete quantities. Within these strategies, children drew upon a range of relationships among fractions, ratio, multiplication, and division to mentally or physically manipulate quantities of sharers and things to produce exhaustive and equal partitions of the items. Additionally, we observed that problems that included number combinations with common factors elicited a wider range of whole-number knowledge and operations in children's strategies and therefore appeared to support richer interconnections than problems with relatively prime or more basic number combinations.     

互逆代换在恒等变形中的应用

互逆代换在解题过程中尽管仅是在式中加上0或乘以1,但只要运用适当,由此即可克服许多困难,使解题过程大大简化.     

电磁学解题点窍

在电磁学教学中,用具体实例将知识点窍、逻辑推理、解题过程贯穿于整个解题过程中,帮助学生克服解题困惑,提高解题能力.     

我国高等旅游教育存在的问题与对策

中国高等旅游教育已有20多年的发展历程,招生院校和招生人数不断增加,但教育质量却有待提高。本文分析了中国高等旅游教育发展中存在的一些问题,并提出了相应的对策。     

新乡旅游资源开发探究

新乡旅游资源经过开发,已形成自己的强势旅游产品,但在资源开发中还存在一些比较突出的问题。树立大旅游观念,拓展区域旅游合作空间;重点开发建设南太行山旅游区;加大农业旅游资源开发的力度;深化历史文化旅游资源;适度开发生态旅游资源是新乡开发旅游资源、发展旅游业的有效途径。     

我区中学德育工作存在的问题与对策

学校德育工作必须从讲政治的高度认清它的重要性,加强德育工作领导,注重德育队伍建设,构建完善的德育工作体系；提高学校领导干部管理学校、反分裂、反渗透和反争夺的能力,营造富有特色的德育氛围,抓好日常行为规范训练,拓宽德育渠道,进一步优化德育工作环境。     

"问题解决"与创新素质培养

“问题解决”国际数学教育界较为流行的一种教学模式。数学学科重视“问题解决”教学 ,有利于培养学生的创新意识 ,训练学生的创新思维 ,发展学生的创新个性 ,锻造学生的创新品质     

申报科技奖励中存在的问题

对优秀的科技成果给予奖励，是我国发展科学技术事业的一项基本政策，一些优秀的科技成果中倾注了科技人员的大量心血，有较高的技术含量，为什么未能获得相应等级的奖励呢？本文就申报奖励中存在的问题谈一些浅见。     

脊柱转动电测试仪的研制和应用研究

运用人机工程学原理设计了人体头颈和腰椎转动传感器,完成了脊柱转动辐度电测试仪的研制和标定。运用该仪器对青年组、老年组分别进行了头颈和腰左、右转动幅度的实测。研究结果得出,人体脊柱转动辐度与年龄呈密切负相关;运动可以改善老年人腰及头颈的柔韧性