首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   38篇
  免费   25篇
电工技术   2篇
综合类   2篇
化学工业   4篇
金属工艺   1篇
机械仪表   3篇
能源动力   7篇
无线电   27篇
一般工业技术   4篇
冶金工业   3篇
自动化技术   10篇
  2023年   7篇
  2022年   8篇
  2021年   6篇
  2020年   8篇
  2019年   10篇
  2018年   2篇
  2017年   4篇
  2016年   4篇
  2015年   5篇
  2014年   4篇
  2013年   2篇
  2007年   2篇
  2005年   1篇
排序方式: 共有63条查询结果,搜索用时 265 毫秒
1.
张旬  林志贤  姚剑敏  郭太良 《微电子学》2019,49(4):502-507, 517
在连续导通模式下,图腾柱无桥拓扑结构功率因数校正器(PFC)的损耗非常大,导致拓扑结构的效率降低,在输入电压过零点处电流容易发生畸变。针对此问题,提出了一种改进的过零点控制方法。将输入电压过零时段划分为两个控制阶段,即高频桥臂主开关管完成软启动,采用双极控制方法有效校正输入电流,使其跟随输入电压。搭建一台1 kW实验样机,并利用DSP开发板进行实验验证。测试结果表明,当开关频率为100 kHz时,功率因数为0.99,PFC模块效率最大可达98.5%,总谐波失真在输出功率大于200 W时小于3%。  相似文献   
2.
The Pd and PdBi nanoparticles dispersed on the reduced graphene oxide (Pd/rGO and PdBi/rGO) have been synthesized through one-pot reaction under the irradiation of microwave and the obtained composites have been characterized by transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy, and their electrocatalytic activities have also been evaluated. It is found that the PdBi0.05/rGO catalyst exhibits higher activity and better stability toward formic acid electrooxidation compared with Pd/C and Pd/rGO. The excellent electrocatalytic performance indicates that the addition of appropriate amount of Bi can greatly enhance the activity and stability of Pd catalysts for the formic acid oxidation.  相似文献   
3.
This paper presents a novel dynamic programming approach for multi-objective planning of electrical distribution systems. In this planning, the optimal feeder routes and branch conductor sizes of a distribution system are determined by simultaneous optimization of cost and reliability. The multiple planning objectives are minimization of: (i) installation and operational cost, and (ii) interruption cost. The first objective function consists of the installation cost of new feeder branches and substations, maintenance cost of the existing and new feeder branches, and the cost of energy losses. The second objective function measures the reliability of the distribution network in terms of the associated interruption costs for all the branches, which includes the cost of non-delivered energy, cost of repair, and the customer damage cost due to interruptions. A dynamic programming based planning algorithm for optimization of the feeder routes and branch conductor sizes is proposed. A set of Pareto solutions is obtained using a weighted aggregation of the two objectives with different weight settings. The proposed approach is evaluated on 21-, 54-, and 100-node distribution systems. The simulation test results are analyzed with various case studies and are compared with those of two existing planning approaches based on multi-objective evolutionary algorithm.  相似文献   
4.
施雨达  陈群超 《微电子学》2022,52(2):306-311
为了解决高精度逐次逼近型模数转换器(SAR ADC)中电容失配对精度的影响,设计了一种二阶误差反馈型失配误差整形(EFMES)16位精度、500 kS/s采样率、3.3 V工作电压的SAR ADC。采用二阶EFMES结构和动态元件匹配技术,降低了电容失配对ADC精度的影响。该EFMES SAR ADC采用SMIC 0.18 μm CMOS工艺设计。在输入信号幅度为2.6 V、采样率为500 kS/s时,该ADC的功耗为8.382 mW,SNDR为93.67 dB,ENOB为15.27位,基于SNDR的FoM为168.4 dB。  相似文献   
5.
《Materials Letters》2007,61(19-20):4173-4176
A new semi-organic nonlinear optical crystal of cobalt thiourea sulfate (CTS) has been grown by solvent evaporation solution growth method at room temperature. The unit cell parameters were evaluated by single crystal X-ray diffraction technique. The vibrational frequencies of various functional groups in the crystals have been derived from FT-IR analysis. The range and percentage of optical transmission are ascertained by recording the UV–VIS–NIR spectrum. The thermal behavior of the crystals has been investigated by DTA and TGA analyses. The mechanical property of the grown crystals has been analyzed by Vicker's microhardness method. The NLO property of the grown crystal has been confirmed by the Kurtz powder second harmonic generation (SHG) test.  相似文献   
6.
Bright and efficient violet quantum dot (QD) based light-emitting diodes (QD-LEDs) with heavy-metal-free ZnSe/ZnS have been demonstrated by choosing different hole transport layers, including poly(4-butyl-phenyl-diphenyl-amine) (poly-TPD), poly[9,9-dioctylfluorene-co-N-[4-(3-methylpropyl)]-diphenylamine] (TFB), and poly-N-vinylcarbazole (PVK). Violet QD-LEDs with maximum luminance of about 930 cd/m2, the maximum current efficiency of 0.18 cd/A, and the peak EQE of 1.02% when poly-TPD was used as HTL. Higher brightness and low turn-on voltage (3.8 V) violet QD-LEDs could be fabricated when TFB was used as hole transport material. Although the maximum luminance could reach up to 2691 cd/m2, the devices exhibited only low current efficiency (∼0.51 cd/A) and EQE (∼2.88%). If PVK is used as hole transport material, highly efficient violet QD-LEDs can be fabricated with lower maximum luminance and higher turn-on voltages compared with counterpart using TFB. Therefore, TFB and PVK mixture in a certain proportion has been used as HTL, turn-on voltage, brightness, and efficiency all have been improved greatly. The QD-LEDs is fabricated with 7.39% of EQE and 2856 cd/m2 of maximum brightness with narrow FWHM less than 21 nm. These results represent significant improvements in the performance of heavy-metal-free violet QD-LEDs in terms of efficiency, brightness, and color purity.  相似文献   
7.
It has proved difficult to visualize the iridescent colors of objects coated with multilayer films in ray-based tracers. A physical-based full spectrum scattering model is proposed in this paper; this model applies the multi-beam interference equations to explain the multiple reflection and refraction of light inside the thin films in order to simulate the phase and amplitude variations of light related to iridescent colors. The Fresnel coefficients for the metallic and dielectric films are introduced respectively to photo-realistically render the wave properties of multilayer films. The solution is further extended to take into account the geometry of rough surfaces instead of a smooth averaging surface where the anisotropic and isotropic scattering characteristics are well explained. We demonstrate the validity of the proposed model by visualizing wave effects for diverse metallic or dielectric multilayer film structures and a Morpho butterfly.  相似文献   
8.
黄继伟  康健 《微电子学》2019,49(5):708-712
为了减少分段式电容阵列ADC中分段电容引起的电容失配效应对转换精度的影响,采用最小均方根(LMS)迭代方法,实现了一种基于扰动的逐次逼近型(SAR)ADC数字前台校准算法。对同一个模拟输入信号先后加入作为扰动的模拟失调电压+Δd和-Δd,依次进行量化。使用LMS对两次量化结果进行加权迭代,得到最佳权重,实现了对ADC的校准。针对电容失配效应、寄生电容效应的影响,搭建了14位SAR ADC数模混合仿真验证系统。仿真结果表明,该校准算法将系统的无杂散动态范围(SFDR)从62.6 dB提升到87.7 dB。  相似文献   
9.
Computer-based learning environments (CBLEs) are a promising means to support language minority (LMi) students in acquiring knowledge and skills through the integration of authentic support in their home language. This study aimed to determine the use of scientific bilingual content offered to fourth-grade students (n = 250) in the CBLE E-Validiv and to identify both student and classroom characteristics related to this use. All the content in E-Validiv is accessible in the language of instruction and one of six other languages. For LMi students, the other language is set to their home language. Multilevel hierarchical regression analyses show that especially LMi students who assess themselves as highly proficient in their home language use the content more in the other language than language majority students. However, even LMi students focus mainly on content in the language of instruction, which indicates that they particularly apply their home language to support their learning process in the language of instruction. Additionally, students who perform higher on science subjects access content more in the language of instruction. The presence of linguistic diversity in the classroom and the positive use of linguistic diversity by the teacher do not seem to matter. The theoretical and practical implications are discussed.  相似文献   
10.
周维  钱慧  江浩 《微电子学》2017,47(3):347-350, 354
在分析基本FIR滤波器原理的基础上,设计了基于微程序的FIR滤波系统的硬件架构,并采用自顶向下的设计方法,利用硬件描述语言Verilog HDL实现了该系统,最后在Xilinx软件开发工具vivado2016.1上进行了仿真,并在Matlab软件中进行了验证。结果表明,设计的基于微程序的FIR滤波系统硬件架构可行,软件可靠,并具有阶数可扩展、可重构、可移植、占有资源少、功耗低的优点。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号