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101.
现有的协同仿真方法与支撑平台在仿真模型分布性、建模与仿真的松耦合性,以及仿真运行快速构建等方面还存在许多不足.为此,提出了广域网环境下的协同建模仿真平台框架.通过服务封装组件和联邦运行组件来实现协同仿真系统的模块化设计与快速组建.分析了两种组件的运行管理和优化机制,以组件概念模型空间与支持结构对象空间的映射方法,实现组件的生成和重用.开发了广域网环境下基于组件的多学科协同建模仿真平台,运行了协同仿真工程实例.实验结果表明,组件方法支持快速的仿真系统组建和模型重用,广域网下的协同仿真平台具有良好的仿真分析效果. 相似文献
102.
沙沱水电站泄洪消能建筑物设计 总被引：4，自引：0，他引：4
乌江沙沱水电站的泄洪流量已超过3万m^3／s，总泄洪能量最高达13100Mw、单宽能量最高达125MW，其泄洪消能建筑物具有流量大、尾水深、低佛氏数和堰上水头高、单宽流量大等特点，是保障枢纽工程安全运行的关键性建筑物。为此，对沙沱水电站泄水建筑物的泄洪、消能布置进行了精心的研究，并通过水工模型试验作了验证，从而较好地解决了该电站泄洪消能建筑物的设计问题。 相似文献
103.
为研究宽垄沟灌时灌水前后且有覆膜条件下水分在垄沟间的运移及再分布,采用对比试验方法,在大棚内模拟宽垄沟灌垄上栽培条件和灌水方案,采用中子仪进行水分观测。试验数据显示,采用垄上覆膜,灌水后垄沟水分的侧向入渗,表现出明显的侧向运移变化。垄背剖面两观测点表层,在灌水后144 h（6 d）,覆膜条件下分别达到田间持水量的80%... 相似文献
104.
黄河下游宽河道治理因河道宽浅散乱、河势游荡多变、人水矛盾突出而一直是黄河治理的焦点和难点。人工干预来水来沙措施的采用、来水总量的减少以及社会发展为其有效治理带来了机遇,宽河固堤、窄河弱防、整治小水河槽是治理黄河河南段宽河道的有效途径。黄河下游宽河道治理应采取的具体措施是:①强力推进标准化堤防建设;②修筑黄河滩区堤防,保障漫滩安全;③整治小水河槽。 相似文献
105.
The photodiode is a promising architecture for photodetection because of its fast response and high external quantum efficiency (EQE). The photodiode requires high detectivity, responsivity, and low dark current for various applications. Here, a new structure of quantum‐dots (QD) photodiode is reported for ultraviolet (UV), blue, green, and red light sensing using a red QD layer between p‐type and n‐type metal‐oxide semiconductors. CdZnSeS/ZnS QD is used for photoabsorption with p‐type Cu2SnS3–Ga2O3 and n‐type Li doped ZnO (LZO) for carrier collection. The QD photodiode has a low dark current density of 2.08 nA cm−2 at −1 V leading to high rectification ratio of ≈105. The QD photodiode shows superior properties with responsivity of 0.258 A W−1 and detectivity of 1.00 × 1013 Jones at −1 V under green illumination. The rise and fall times of QD photodiode are 2.1 and 2.6 ms, respectively. The QD photodiode on a flexible polyimide (PI) substrate is also demonstrated, exhibiting stable characteristics under bending test of 20 000 cycles at a bending radius of 0.32 mm. 相似文献
106.
This article presents design and analysis of three wide band zeroth‐order resonance antennas (antennas I, II, and III) using composite right and left‐handed transmission line (CRLH‐TL) approach. Coplanar waveguide technology, single layer via‐less structures are used to have the design flexibility. The bandwidth characteristics are analyzed by using lumped parameters of CRLH‐TL. By introducing a simple slot in the ground plane of antenna I both bandwidth enhancement and circularly polarization characteristics are achieved in antenna II. Another quarter wave L‐shaped slot has been introduced in the ground plane of antenna II to introduce a notch band in the frequency response of antenna III. Achieved measured 10 dB return loss bandwidth of antenna I and antenna II are 960 (3.3‐4.26 GHz) and 2890 MHz (2.77‐5.66 GHz), respectively. Antenna III offers measured 10 dB return loss bandwidth of 3220 MHz (2.32‐5.54 GHz) with a band notch from 2.39 to 2.99 GHz that isolates the 2.4 GHz WLAN and 3.5 GHz WiMAX band. Antenna II and antenna III have circular polarization property with measured axial ratio bandwidth of 440 MHz. The measured peak realized gain of antennas II and III is around 1.53‐2.9 dBi. 相似文献
107.
In this article, a coding optimized metasurface is proposed for linear polarization conversion in broadband and wide‐angle. Using an improved coding method, the geometry of the metallic structure and the size of the unit cell are encoded with a code sequence. The code sequence is optimized by genetic algorithm, considering bandwidth, efficiency, and angular stability. In this way, a coding optimized metasurface was obtained for polarization conversion in broadband and wide‐angle. It can convert linear polarized incidence to its orthogonal polarized reflection in 8 to 18.9 GHz and 0° to 45°, with the polarization conversion ratio larger than 80%. Both simulated and measured results demonstrated the effectiveness of the proposed metasurface. Hence, our method offers an effective strategy to design high‐performance polarization conversion metasurfaces. 相似文献
108.
Jun Hu Xi Wang Shaojun Li Muhammad Asif Peng Ding Yongbo Su Wuchang Ding Feng Yang Xiaojuan Chen Zhi Jin 《国际射频与微波计算机辅助工程杂志》2020,30(5)
Stacked structure is a good solution to overcome the low output voltage swing provided by a single device. When several devices are stacked, the bandwidth and output power are multiple times higher. This article analyzes the small‐signal voltage gain of the stacked structure, deriving the gain expression of the high‐frequency model and simplified model. Based on the specific device parameter, the different small‐signal voltage gains between the two models are compared and the designed stacked structure is proved to obtain a flat gain at low frequencies below about 3 GHz. To our best knowledge, this is the first article to analyze the gain flatness of stacked structure with two equivalent circuit models. To verify the stacked theory, a pseudomorphic high‐electron‐mobility transistor（PHEMT） power amplifier (PA) is implemented using 0.25 μm Gallium arsenide (GaAs) technology. The PA achieves an ultra‐high bandwidth of 30 MHz to 3 GHz and a linear gain of 21 dB ± 1.5 dB. At a 16‐V drain bias voltage, a saturated output power of higher than 2 W and a peak power‐added efficiency (PAE) of 44.1% are attained. 相似文献
109.
A design approach to a novel planar self‐balanced, wide beamwidth magnetic dipole antenna with high front‐to‐back ratio (FBR) is advanced. The principle for FBR enhancement is revealed at first. As seen, the back‐lobe level can be effectively suppressed by adjusting the unbalanced current ratio (UCR) factor: By varying the radius of the circular sector magnetic dipole antenna on the bottom layer and incorporating an arc‐shaped branch at the end of the parasitic strip, the UCR factor can be properly tuned, and the back‐lobe level can be flexibly controlled. Then, a set of closed‐form formulas is derived to provide basic design guidelines and determine the initial value of key parameters. Parametric studies on FBR are then carried out to attain the ultimate designs in a step‐by‐step manner. As numerically and experimentally verified at the 2.45‐GHz band, the FBR of a planar, air‐substrate magnetic dipole antenna is indeed increased to over 30 dB with broadened E‐/H‐plane half‐power beamwidth up to 130°/90°. Good agreement between the theoretical, numerical, and experimental results has evidently validated the proposed antenna design approach. 相似文献
110.
This article deals with the design of a broadband cavity‐backed microstrip‐fed wide‐slot antenna array for L‐band applications. For verification purpose, a sample 1 × 4‐element antenna array has been designed, manufactured and tested. Experimental results have shown satisfactory agreement with the simulation. The proposed antenna array exhibits a measured impedance bandwidth of 1.4 GHz (90%) with frequency of 0.85 to 2.25 GHz and the gain is higher than 11 dBi. The designed antenna has small size and low weight and can be fabricated using a low‐cost fabrication process for easy integration with RF circuits and microwave components. This work is useful for some radar applications and radio frequency identification systems. 相似文献