According to the fact that the secondary users＇ delay requirements for data transmission are not unitary in cognitive radio networks, the secondary users are divided into two classes, denoted by SU1 and SU2, respecti...According to the fact that the secondary users＇ delay requirements for data transmission are not unitary in cognitive radio networks, the secondary users are divided into two classes, denoted by SU1 and SU2, respectively. It is assumed that SU1 has a higher priority to occupy the primary users＇ unutilized channels than SU2. A preemptive resume priority M/G/1 queuing network is used to model the multiple spectrum handoffs processing. By using a state transition probability matrix and a cost matrix, the average cumulative delays of SU1 and SU2 are calculated, respectively. Numerical results show that the more the primary user＇s traffic load, the more rapidly the SU2＇s cumulative handoff delay grows. Compared with the networks where secondary users are unitary, the lower the SUI＇s arrival rate, the more obviously both SUI＇s and SU2＇s handoff delays decrease. The admission access regions limited by the maximum tolerable delay can also facilitate the design of admission control rules for graded secondary users.展开更多
The challenges facing public schools are multifaceted and include: teachers dissatisfaction, non-commitment of educators, chronic absenteeism by educators, low morale, poor work ethics by educators, late coming of bot...The challenges facing public schools are multifaceted and include: teachers dissatisfaction, non-commitment of educators, chronic absenteeism by educators, low morale, poor work ethics by educators, late coming of both educators and learners, overcrowding in classes, lack of technical resources and many more. A cursory investigation of public secondary school buildings in Ado-Odo/Ota L.G.A shows its deplorable conditions of structural, aesthetical and decorative disrepair. Therefore the paper focused on examining users “perception of the present deplorable physical condition and neglect of public secondary school. The study engaged the use of quantitative method of analysis, employing the use of questionnaire administered randomly and distributed face-to-face to targeted despondences”. The result of findings revealed performance/productivity of building users depends largely on working and learning condition of building. The outcomes of the research would help policy makers, facilities maintenance experts and professionals alike to device a policy for regular maintenance of public building in other to enhance performance and increase productivity amongst users.展开更多
为了开发CATIA的用户自定义特征(User Defined Feature)来实现通用特征在不同零件文档上下文的灵活使用,首先对CATIA二次开发的各种方法做了分析比较,讨论了基于CAA(Component Application Architecture)的CATIA二次开发的基本原理,重...为了开发CATIA的用户自定义特征(User Defined Feature)来实现通用特征在不同零件文档上下文的灵活使用,首先对CATIA二次开发的各种方法做了分析比较,讨论了基于CAA(Component Application Architecture)的CATIA二次开发的基本原理,重点研究了CAA中数据模型扩展应用和用户自定义特征的创建方法,给出了具体的几何自定义特征开发实例。展开更多
基金The National Natural Science Foundation of China(No.60972026,61271207)the National Science and Technology Major Project(No.2010ZX03006-002-01)+1 种基金the Specialized Research Fund for the Doctoral Program of Higher Education(No.20090092110009)the Specialized Development Foundation for the Achievement Transformation of Jiangsu Province(No.BA2010023)
文摘According to the fact that the secondary users＇ delay requirements for data transmission are not unitary in cognitive radio networks, the secondary users are divided into two classes, denoted by SU1 and SU2, respectively. It is assumed that SU1 has a higher priority to occupy the primary users＇ unutilized channels than SU2. A preemptive resume priority M/G/1 queuing network is used to model the multiple spectrum handoffs processing. By using a state transition probability matrix and a cost matrix, the average cumulative delays of SU1 and SU2 are calculated, respectively. Numerical results show that the more the primary user＇s traffic load, the more rapidly the SU2＇s cumulative handoff delay grows. Compared with the networks where secondary users are unitary, the lower the SUI＇s arrival rate, the more obviously both SUI＇s and SU2＇s handoff delays decrease. The admission access regions limited by the maximum tolerable delay can also facilitate the design of admission control rules for graded secondary users.
文摘The challenges facing public schools are multifaceted and include: teachers dissatisfaction, non-commitment of educators, chronic absenteeism by educators, low morale, poor work ethics by educators, late coming of both educators and learners, overcrowding in classes, lack of technical resources and many more. A cursory investigation of public secondary school buildings in Ado-Odo/Ota L.G.A shows its deplorable conditions of structural, aesthetical and decorative disrepair. Therefore the paper focused on examining users “perception of the present deplorable physical condition and neglect of public secondary school. The study engaged the use of quantitative method of analysis, employing the use of questionnaire administered randomly and distributed face-to-face to targeted despondences”. The result of findings revealed performance/productivity of building users depends largely on working and learning condition of building. The outcomes of the research would help policy makers, facilities maintenance experts and professionals alike to device a policy for regular maintenance of public building in other to enhance performance and increase productivity amongst users.
文摘为了开发CATIA的用户自定义特征(User Defined Feature)来实现通用特征在不同零件文档上下文的灵活使用,首先对CATIA二次开发的各种方法做了分析比较,讨论了基于CAA(Component Application Architecture)的CATIA二次开发的基本原理,重点研究了CAA中数据模型扩展应用和用户自定义特征的创建方法,给出了具体的几何自定义特征开发实例。
