共查询到19条相似文献，搜索用时 133 毫秒
1.
邓锋 《商丘职业技术学院学报》2008,7(2):71-73
基于单片机和EDA相结合的技术,用于产生各种频率的正弦波、方波和三角波,其幅值0-5V可调,幅值步进为0．039V,频率步进为1Hz．波形发生器以单片机（MCS8031）为中心控制单元,由键盘输入模块、数码管显示模块、D／A波形发生模块、幅值调整模块组成．采用DDFS技术,先将要求的波形数据存储于EEPROM中,保证掉电以后波形数据不丢失．采用FPGA实现波形的发生,通过DDFS技术、VHDL语言和单片机汇编语言编程技术的完美结合,实现了对正弦波、方波和三角波三种波形的频率、幅值的设置和发生． 相似文献
2.
文章首先分析了传统多周期同步测频原理及误差,然后对全同步和准全同步两种频率测量的改进方法做了讨论,分析了其原理与特点,最后,在此基础上提出了一种新的改进方法,该方法通过对标准频率计数值的修正,在不提高系统时钟频率和延长闸门时间的前提下,实现了测量精度的提高,并详细分析了其测量误差。 相似文献
3.
黄磊 《淮北职业技术学院学报》2006,5(5):72-72
多周期同步测量是实现频率等精度测量的一种有效的方法.本文提出了用单片机实现频率的多周期同步测量的原理,并对该方法的测量精度进行了分析. 相似文献
4.
本文基于矩量法（MOM）中阻抗矩阵与入射角度的不相关性,提出将压缩传感（CS）技术引入电磁散射问题的方法,以达到在不降低计算精度的前提下减少计算时间的目的.该方法结合了压缩感知和计算统一设备架构（CUDA）技术,通过利用图形处理器（GPU）的并行计算解决了宽角度的电磁散射问题.数值计算结果表明,该方法与传统计算方法相比,在保持精度的同时,大大降低了计算所需的时间. 相似文献
5.
采用基于DDS模块的硬件实现方法设计基带信号发生器,在FPGA内部用DDS模块进行频率合成和叠加,利用EDA技术和FPGA实现直接数字频率综合器DDS的设计.可以完成快速的频率切换,并且在改变时能够保持相位的连续,很容易实现频率、相位和幅度的数控调制.实验结果表明该信号发生器达到了一个比较好的设计精度. 相似文献
6.
陈兵清 《商情·科学教育家》2013,(38)
本文主要论述了利用FPGA (Field Programmable Gate Array,现场可编程门阵列)进行测频计数,单片机实施控制实现频率计的设计过程.该频率计利用等精度的设计方法,克服了基于传统测频原理的频率计的测量精度随被测信号频率的下降而降低的缺点.等精度的测量方法不但具有较高的测量精度,而且在整个频率区域保持恒定的测试精度. 相似文献
7.
微弱信号的频率检测是微弱信号处理的一个重要内容,也是判定微弱信号幅度和相位的重要前提.文章提出一种方法,将AD采样数据先用结构函数算法粗略判定信号频率,然后进行数字预滤波,最后再次使用结构函数算法准确测定频率.该方法完全数字化,在带AD采样和存储器的微处理器系统上均可实现,编程简单,且不要求实时性,很容易在本科生的微弱信号检测实验中实施.实验证明,该算法对于信噪比为-20 dB以上的信号都具有很好的频率检测精度.在实验中提高采样AD的位数、采样频率、采样点数可进一步提高检测精度. 相似文献
8.
为提高捷联惯导姿态圆锥算法的机动性能,提出一种新的圆锥补偿结构,该结构通过在传统结构中增加一个子样获得.在给出经典圆锥运动定义的基础上,推导了基于新的圆锥补偿结构的圆锥补偿残余误差通式,并采用频率泰勒方法设计了新的圆锥补偿结构系数,从而获得一类新的圆锥补偿算法.定义了2种圆锥算法误差模型,分别用于圆锥环境和机动环境下的圆锥算法性能评估.仿真结果表明:新的四子样圆锥算法的机动精度比传统四子样圆锥算法的机动精度提高约1倍;与传统的压缩圆锥算法相比,新的圆锥算法在保持圆锥性能的同时具有更好的机动性能. 相似文献
9.
叙述了基于DDS原理,用存储器附加必要的控制和转换电路可产生正弦波的原理和实现方法.该方法实现简单,输出波形频率可调范围宽、稳定度较好、精度较高. 相似文献
10.
《西安文理学院学报》2021,(2)
压缩感知理论突破了香农采样定律中对信号采样频率的限制.测量矩阵的构造是压缩感知理论中一个重要的部分.减小传感矩阵的互相干系数,选择性能较好的测量矩阵,能够提高重构质量.设计了EigGrd算法,Gram矩阵是由测量矩阵和稀疏变换矩阵乘积构成,使用特征值分解对Gram矩阵进行初始化,在稀疏变换矩阵固定的情况下,利用梯度下降法迭代优化传感矩阵,使得传感矩阵互不相干系数达到最大,从而优化了测量矩阵.在仿真实验中,将该方法与已知的测量矩阵比较,用优化的测量矩阵在图像重建中有着较高的峰值信噪比.表明了该方法优化的测量矩阵在图像重构精度上有着一定的优势. 相似文献
11.
In this study, nine simplified short composite columns consisting of core CFST (concrete filled steel tube) of different diameters and outer reinforced concrete were constructed to study their compressive performance under axial or eccentric compression. The failure mode is characterized by the crush of the outer concrete. The bearing capacity increases at first and then decreases with further increase of the position coefficient. It can be concluded that position coefficient is an important structural parameter that has considerable influences on the ultimate bearing capacity of the composite columns. The outer concrete, steel tubes and longitudinal reinforcement are found to work in a cooperative manner under axial or eccentric compression when the position coefficient is about 0.5. An improved bearing capacity algorithm that takes the position coefficient into account has been proposed based on the experimental and simulation results and current technical specification in China. It has been proven to be precise and safe. 相似文献
12.
Bobby Hoffman Matthew T. McCrudden Gregory Schraw Kendall Hartley 《Asia Pacific Education Review》2008,9(4):464-474
This study investigated the influence of informational complexity and working memory capacity on problem-solving efficiency.
We examined two predictions of thesituational efficiency hypothesis, which states that the efficiency of problem solving varies as a function of situational constraints. One prediction is that
informational complexity affects problem-solving efficiency. A second prediction is that working memory capacity affects problem-solving
efficiency. Students completed a working memory task and solved abstract and concrete syllogisms. Participants solved abstract
syllogisms more accurately than concrete syllogisms and spent more time solving abstract syllogisms. Thus participants demonstrated
greater problem-solving efficiency when solving concrete syllogisms. Results indicate that there is a trade-off between problem-solving
accuracy and problem-solving time when information differs with respect to informational complexity, a phenomenon we refer
to as theefficiency paradox. Working memory capacity did not affect accuracy or efficiency. The results support the conclusion that problem-solving efficiency
is situational and a function of the complexity of information. Educational implications and directions for future research
are suggested. 相似文献
13.
针对直接数字频率合成的相位截尾误差，提出了采用高速CPLD设计实时连续正弦运算模块彻底避免相位截尾误差问题，给出了几种可行的算法分析和谱纯度仿真讨论。该模块具有较好的输出信号质量，运行速度与DDFS相当，不仅可以和单片机构成两片结构的信号发生器，也可以作为信号源嵌入到各种片上电子系统设计中去，具有设计的灵活性和底层可重用性。 相似文献
14.
本文从短时记忆编码方式、容量、编码方式与容量关系及短时记忆与阅读关系的角度 ,回顾了国内外关于聋人短时记忆的研究 ,提出了今后聋人短时记忆研究的思路 相似文献
15.
A capacity theory of writing: Working memory in composition 总被引：8，自引：0，他引：8
Deborah McCutchen 《Educational Psychology Review》1996,8(3):299-325
The review examines ways in which working memory contributes to individual and particularly to developmental differences in writing skill. It begins with a brief definition of working memory and then summarizes current debates regarding working memory and capacity theories in the field of reading. It is argued that a capacity theory of writing can provide a framework within which to consider the development of writing skill, and relevant data are discussed. Effects of capacity limitations are documented in all three component writing processes: planning, translating, and reviewing. 相似文献
16.
提出一种无损的数据压缩的字典方法，称为特征码字典方法（ＣＣＤ）．该方法采用了分片管理以及变码长等技术，能较大程度上消除数据文件中的冗余，达到较好的压缩效果． 相似文献
17.
FLASH存储器容易出现单个数据位错的常见问题,本文提出了基于海明码的二次校验编码方法。相比以往的扩展海明编码方法,该方法提高了编/解码的效率和纠错能力,有利于提高FLASH存储器的数据安全性并延长了FLASH存储的使用寿命。 相似文献
18.
Bobby Hoffman 《Learning and individual differences》2010,20(3):276-283
This study investigated the role of self-efficacy beliefs, mathematics anxiety, and working memory capacity in problem-solving accuracy, response time, and efficiency (the ratio of problem-solving accuracy to response time). Pre-service teachers completed a mathematics anxiety inventory measuring cognitive and affective dispositions for mathematics, before completing an operation span task to measure working memory capacity, rating self-efficacy for mental multiplication, and then solved computer-based multiplication problems at two complexity levels. A simultaneous regression design was used to assess the unique variance associated with each variable. There were two new findings; the differential role of self-efficacy on response time and efficiency, and the potential compensatory relationship between self-efficacy and mathematics anxiety related to efficiency outcomes. Educational implications and suggestions for future research were proposed. 相似文献
19.
多媒体数据压缩技术探析 总被引：1，自引：0，他引：1
简艳英 《漯河职业技术学院学报》2008,7(2):65-66
随着互联网的普及,人们对信息的需求尤其是多媒体信息的需求日益增长。为保障大容量的多媒体数据在互联网上的有效传输,必须对多媒体数据进行压缩处理。利用有损压缩和无损压缩方法,对图像、音频、视频等多媒体数据进行压缩,形成联合图像专家组JPEG和运动图像专家组MPEG等常用压缩标准。 相似文献