排序方式: 共有8条查询结果,搜索用时 0 毫秒
1
1.
DBF天线安装后,一般不具备可机械旋转的常规测试条件。研究DBF天线方向图的间接测试问题,提出一种基于波束扫描的测试方法,给出其测试原理和测试流程。针对波束宽度、副瓣水平和波束指向等天线主要参数,用仿真比对该方法与常规方法的测试结果和误差。在DBF天线方向图正常和异常两种情况下,两种方法可得到相近的仿真测试结果,证明间接测试方法的有效性。 相似文献
2.
3.
分析了不同数据源间的数据类型转换所面临的技术问题,并重点介绍了目前主流的数据库管理系统间的数据转换途径,最后具体介绍了如何转换DBF数据的方法。 相似文献
4.
杨旭东 《兰州石化职业技术学院学报》2005,5(4):26-27
针对目前生成DBFIII数据库文件组件缺乏的现状,提出了利用组件来生成DBFIII数据库文件的方法,并给出了相应的解决方案. 相似文献
5.
对短波发射天线DBF系统进行有效的监测具有重要的意义.本文对环路校准法、中场测试法分别进行详细讨论.指出了环路较准法可将监测误差减小到最小的程度,中场测试法可消除空间干拔的影响. 相似文献
6.
7.
介绍了波束形成的原理、系统组成和实现方法。对本数字波束形成项目,提出在FPGA上建立NIOS软核来实现雷达在各种工作模式下的数字波束形成。 相似文献
8.
The study aims to investigate the effects of delivery modalities on psychometric characteristics and student performance on cognitive tests. A first study assessed the inductive reasoning ability of 715 students under the supervision of teachers. A second study examined 731 students’ performance on the application of the control-of-variables strategy in basic physics but without teacher supervision due to the COVID-19 pandemic. Rasch measurement showed that the online format fitted to the data better in the unidimensional model across two conditions. Under teacher supervision, paper-based testing was better than online testing in terms of reliability and total scores, but contradictory findings were found in turn without teacher supervision. Although measurement invariance was confirmed between two versions at item level, the differential bundle functioning analysis supported the online groups on the item bundles constructed of figure-related materials. Response time was also discussed as an advantage of technology-based assessment for test development. 相似文献
1