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1.
Hai Huang Haichao An Wenrui Wu Lingyan Zhang Beibei Wu Weipeng Li 《Structural and Multidisciplinary Optimization》2014,50(5):883-898
According to the mission of a satellite with maneuver capability, the collaborative optimization (CO) method was introduced for the satellite system design, and the related multidisciplinary design optimization (MDO) model was established. The possessing and needed velocity increments Δv and Δv n e e d were taken as the measurement of maneuvering capability of the studied satellite, which were then combined with total mass of the satellite to form the optimization objective in the systematic level of the MDO problem. The design variables and constraints of the MDO problem dealt with disciplines or subsystems as guidance, navigation and control (GNC), power, and structure, and corresponding engineering analysis models were also built. A program system to solve the MDO problem wasdeveloped by integrating a non-nested CO method, the commercial and user-supplied codes on framework software iSIGHT. The result showed that the satellite performance could be obviously improved, which also indicates MDO technique is feasible and effective for the spacecraft design problem. The modeling and optimization procedure of the work can be referred for further research and engineering design. 相似文献
2.
This article analyzes the bias dependence of gate‐drain capacitance (Cgd) and gate‐source capacitance (Cgs) in the AlGaN/GaN high electron mobility transistors under a high drain‐to‐source voltage (Vds) from the perspective of channel shape variation, and further simplifies Cgd and Cgs to be gate‐to‐source voltage (Vgs) dependent only at high Vds. This method can significantly reduce the number of parameters to be fitted in Cgd and Cgs and therefore lower the difficulty of model development. The Angelov capacitance models are chosen for verifying the effectiveness of simplification. Good agreement between simulated and measured small‐signal S‐parameters, large‐signal power sweep, and power contours comprehensively proves the accuracy of this simplification method. 相似文献
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Sediment is an important environmental factor for aquatic ecosystem and oyster productivities of Apalachicola Bay located in Florida, USA. Based on the data analysis in this study, surface wind speed is highly correlated to the turbidity of water column, which results from sediment resuspension and transport in the Apalachicola Bay. In this paper, an application of a 3D sediment transport model to predict the wind-induced sediment transport in Apalachicola Bay is described. The sediment model is coupled with a 3D hydrodynamic module in the Environmental Fluid Dynamics Code (EFDC) model that provides information on estuarine circulation and salinity transport under normal temperature conditions. The hydrodynamic model was calibrated with field observations of water levels and salinity. The sediment transport model solves the transport equation with sources and sinks terms to describe sediment deposition and resuspension. The coupled hydrodynamic and sediment transport models were used to investigate wind-induced total suspended sediments (TSS) resuspension and transport in the bay. For the period June 1–July 30, 2005 two storm events with strong winds gave model results of TSS concentrations that compared well with the field observations. Model simulations reasonably reproduce the sudden increase of sediment concentrations during the storm events. Maximum sediment concentrations in the bay during the two storm events were 10 times or more than those in the pre-storm conditions. Spatial sediment transport from model simulations indicate active sediment resuspension and transport near areas of highly productive oyster beds. The model predictions of TSS and salinity can be used as inputs to an oyster dynamic model (Wang, H., Huang, W., Harwell, M., Edmiston, L., Johnson, E., Hsieh, P., Milla, K., Christensen, J., Stewart, J., Liu, X., 2008. Modeling eastern oyster population dynamics in response to changing environment in Apalachicola Bay, Florida. Journal of Ecological Modeling 211, 77–89) to support the ecological study of oyster growth and mortality in the aquatic ecosystem of Apalachicola Bay. 相似文献
4.
姬文瑞 《数码设计:surface》2009,(5):126-128
艺术设计教育的核心是创设性思维过程的形成和培养,其整个过程中含有的大量暗默知识如何与形式知识互动转换,产生创设性的思维是艺术设计创作和教育的难点。因此设计教育应该放在知识创造的视阈下进行思考。本文基于野中郁次郎和竹内弘高认为的"人类知识是通过暗默知识与形式知识之间的社会化相互作用而创造和扩展出来的"观点,分析探讨艺术设计创作和教育中的暗默知识与形式知识互动转换以及创设性思维过程的形成和培养。 相似文献
5.
利用基带直调信号注入锁定半导体激光器产生全光上变频信号的研究 总被引:1,自引:1,他引:1
提出了一种将低速基带信号直调产生的宽谱信号,注入至用于上变频的分布反馈式半导体激光器(DFB-LD),利用调制信号光谱中的高阶分量对从激光器进行相位锁定,从而产生光学上变频信号的方法。对直调信号注入锁定DFB-LD产生光学上变频信号的机理进行了理论分析,完成了2.5Gb/s伪随机码基带信号通过直调并注入从激光器,分别产生了30,35,40GHz副载波频率的全光上变频信号的实验,并在时域和频域上,对上变频信号的特征进行了研究。该方案结构简单,无需高速外调制器及高频本振,具有集成潜力,理论上可产生更高载频(如60GHz),对目前的光-无线混合接入提供了一种可行的解决方案。 相似文献
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针对传统电能质量扰动分类模型中扰动特征复杂、识别步骤繁琐的问题,提出了一种通过模拟退火(SA)算法与粒子群优化(PSO)算法相结合来优化卷积神经网络(CNN)的电能质量扰动分类模型。将CNN卷积层中的二维卷积核替换成一维卷积核;采用SA算法对PSO算法进行改进,规避PSO算法陷入局部最优的困境;采用改进后的PSO算法对CNN进行参数寻优;利用优化CNN提取和筛选合适的特征,根据这些特征利用分类器得到最终分类结果。通过算例分析得出,使用基于SA-PSO算法优化的CNN的电能质量扰动分类模型能精确地识别出电能质量扰动信号。 相似文献
9.
图像描述任务旨在针对一张给出的图像产生其对应描述。针对现有算法中语义信息理解不够全面的问题,提出了一个针对图像描述领域的多模态Transformer模型。该模型在注意模块中同时捕捉模态内和模态间的相互作用;更进一步使用ELMo获得包含上下文信息的文本特征,使模型获得更加丰富的语义描述输入。该模型可以对复杂的多模态信息进行更好地理解与推断并且生成更为准确的自然语言描述。该模型在Microsoft COCO数据集上进行了广泛的实验,实验结果表明,相比于使用bottom-up注意力机制以及LSTM进行图像描述的基线模型具有较大的效果提升,模型在BLEU-1、BLEU-2、BLEU-3、BLEU-4、ROUGE-L、CIDEr-D上分别有0.7、0.4、0.9、1.3、0.6、4.9个百分点的提高。 相似文献
10.
选坐落于广州的一幢1梯2户6层为特定的参照建筑,用JGJ 75—2003《夏热冬暖地区居住建筑节能设计标准》的方法,计算该建筑物外装饰材料的太阳能辐射吸收率ρ与建筑物空调年耗电量指数(ECFc)的关系。结果表明:ρ值越低,建筑物ECFc越低,越节能;当ρ≤0.65时,ECFc≤0.5,即该建筑符合JGJ 75—2003的节能设计;证明反射隔热涂料的基本要求之一就是要降低涂料的ρ值。测量涂料的太阳能总反射比(TSR)结果表明:使用铬铁黑、铬铁红等颜料,在中等深度颜色到深颜色范围内,涂料的TSR能够提高10%~20%,节约空调年耗电量10%左右。 相似文献