清江来水对葛洲坝水电站调度策略影响研究

葛洲坝水电站调度难点主要在于下游水位变化的不确定性,下游水位极易受到清江来水的顶托影响。为探索清江来水的顶托作用对葛洲坝水电站调度策略的影响,利用实测水文数据统计分析清江来水对宜昌水文站的顶托影响量,并据此分析水电站的损失出力。结果表明：清江来水对宜昌站的顶托作用随着清江来水的增大而增大、随着宜昌站流量的增大而减小,电站损失出力随着清江来水的增大而增大、随着出库流量的增大而先增大后减小,当出库流量为满发流量时达到最大损失出力值。研究成果可为葛洲坝电站调度策略提供参考,实际调度还需要结合三峡水库联合调度,优化水位控制,综合制定调度决策。     

叶片数对超低比转速斜流式水轮机的影响

叶片数是影响超低比转速斜流式水轮机水力性能的因素之一。文章利用Fluent 16.0软件,研究分析了不同叶片数模型在不同流量工况下,外特性曲线以及内部流场分布图。结果表明:不同叶片数时,流量从最高效率点向小流量变化时效率下降的速度要比从最高效率点向大流量变化时的快。对于具体参数组合的超低比转速斜流式水轮机,存在最优的叶片数使得其水力性能最优。     

Layout Optimization for Greenhouse WSN Based on Path Loss Analysis

When wireless sensor networks (WSN) are deployed in the vegetable greenhouse with dynamic connectivity and interference environment, it is necessary to increase the node transmit power to ensure the communication quality, which leads to serious network interference. To offset the negative impact, the transmit power of other nodes must also be increased. The result is that the network becomes worse and worse, and node energy is wasted a lot. Taking into account the irregular connection range in the cucumber greenhouse WSN, we measured the transmission characteristics of wireless signals under the 2.4 Ghz operating frequency. For improving network layout in the greenhouse, a semi-empirical prediction model of signal loss is then studied based on the measured data. Compared with other models, the average relative error of this semi-empirical signal loss model is only 2.3%. Finally, by combining the improved network topology algorithm and tabu search, this paper studies a greenhouse WSN layout that can reduce path loss, save energy, and ensure communication quality. Given the limitation of node-degree constraint in traditional network layout algorithms, the improved algorithm applies the forwarding constraint to balance network energy consumption and constructs asymmetric network communication links. Experimental results show that this research can realize the energy consumption optimization of WSN layout in the greenhouse.     

Cross lingual speech emotion recognition via triple attentive asymmetric convolutional neural network

The application of cross‐corpus for speech emotion recognition (SER) via domain adaptation methods have gain high acknowledgment for developing good robust emotion recognition systems using different corpora or datasets. However, the issue of cross‐lingual still remains a challenge in SER and needs more attention to resolve the scenario of applying different language types in both training and testing. In this paper, we propose a triple attentive asymmetric convolutional neural network to address the recognition of emotions for cross‐lingual and cross‐corpus speech in an unsupervised approach. The proposed method adopts the joint supervision of softmax loss and center loss to learn high power discriminative feature representations for target domain via the use of high quality pseudo‐labels. The proposed model uses three attentive convolutional neural networks asymmetrically, where two of the networks are used to artificially label unlabeled target samples as a result of their predictions from training on source labeled samples and the other network is used to obtain salient target discriminative features from the pseudo‐labeled target samples. We evaluate our proposed method on three different language types (i.e., English, German, and Italian) data sets. The experimental results indicate that, our proposed method achieves higher prediction accuracy over other state‐of‐the‐art methods.     

基于注意力机制和卷积神经网络的异步电动机三相电压不平衡损耗研究

配电网中三相电压不平衡对异步电动机损耗会造成较大影响。运用等效电路公式分析三相电压不平衡影响下电动机损耗存在精度不稳定、需要参数过多且数学模型过于复杂等问题。针对以上问题,提出一种基于注意力机制和卷积神经网络(CNN)的异步电动机损耗评估方法。该方法将实测电机数据作为输入,引入注意力机制为输入特征赋予不同权重;采用卷积层和全连接层组成的CNN构架对异步电动机实测数据进行学习,最后完成损耗评估。以现场试验得到的电机损耗数据作为实际算例,该方法评估损耗与实测损耗平均误差仅为0.717%和0.549%,并与其他典型机器学习算法进行对比,结果表明所提方法具有更好的损耗评估性能。     

全封闭大功率永磁牵引电机的温度场数值计算

为研究全封闭大功率永磁牵引电机额定工况下的稳态温度场,以一台额定功率为815 kW的永磁同步牵引电机为研究对象,依据成型绕组槽部导热模型,建立了整机三维温度场共轭传热计算模型。考虑旋转磁化、冲压过程和磁密高阶谐波对定子铁耗的影响,以及水套-定子铁心间接触热阻抗对电机温升的影响,采用Fluent软件对电机额定工况下的稳态流场与温度场求解,使用电阻法和埋置检温计法（ETD）测得电机在额定工况下绕组的平均温升、铁心测点和绕组端部测点局部温升,绝对误差分别为-3.7 K、-0.3 K和7.6 K。进一步分析了电机水路和内风路流场分布特性、水套-定子铁心间接触间隙对绕组平均温升的影响以及槽内绕组附近的温升分布情况,最后提出了该类电机冷却系统设计优化方向。     

Calcium carbonate and ammonium polyphosphate flame retardant additives formulated to protect ethylene vinyl acetate copolymer against fire: Hydrated or carbonated calcium?

In this study, the effect of the chemical nature of different calcium (Ca)-based minerals as flame retardant additives in combination with ammonium polyphosphate (APP), in 1:1 proportions, on the flame retardancy behavior and performance of ethylene vinyl acetate copolymer was discussed. Combining APP with partly and completely hydrated calcium oxide led to superior flame-retardant function detected in mass loss calorimeter measurements with respect to the corresponding system containing carbonated calcium. This privileged character was attributed to the higher reactivity of hydrated Ca-based fillers toward APP in comparison with Ca carbonate, which induced the formation of an intumescent residue. The difference between reactivity potential of hydrated and dry Ca was demonstrated by the newly formed thermally stable species, and further evidenced by thermogravimetric analysis performed on APP/fillers blends. Moreover, the presence of more crystalline domains in the Ca/phosphorus-based compounds was evidenced by XRD analysis of the mass loss calorimeter test residues. The results of this work highlight the role of blend additive systems on the performance of flame retardancy of polymer materials.     

预应力中空棒构件设计与力学特性

为满足装配式建筑节点接缝混凝土抗震性能的需要,以一种自平衡预应力中空棒为研究对象,研究接缝位置短杆件施加预应力的效果。根据力的平衡机理,对结构内部钢棒施加压力使结构外部钢管协调受力拉伸,达到设计预应力后由螺母锁定,将杆件埋入到装配式节点接缝混凝土,浇筑早强灌浆料,待固结达到预定强度释放反力棒,依靠外螺纹结构与混凝土的粘结力自锚实现接缝混凝土施加预应力。力学性能分析方面,研究杆件张拉阶段、静置松弛阶段应力变化及损失情况,验证了杆件张拉完成至放张前应力存储的有效性,通过分析杆件放张后应力分布、预应力损失等参数,验证了杆件应用到节点混凝土后传递应力的机理及有效性,并采用有限元方法分析预应力混凝土构件应力分布规律。研究结果表明预应力中空棒技术作用于装配式节点接缝混凝土具有较高的抗震和耗能能力,对装配式建筑节点混凝土高抗震性能的实现提供了一种新的技术手段。     

光伏发电接入对配电网低压台区线损的影响

随着可再生能源的不断开发,越来越多的光伏发电接入配电网,而光伏发电的不稳定性会对配电网的稳定造成影响。为此,针对光伏发电对配电网低压台区线损的影响,建立了电源接入模型并进行了仿真计算。     

方波激励下纳米晶体铁心损耗模型建立与验证

为了实现电力机车小型化轻量化的发展要求,国内外专家考虑通过采用提高变压器的工作频率减小变压器整体的体积和质量。铁心作为高频变压器的关键部件,可以准确计算铁心损耗,对中高频变压器的设计和优化具有重要作用。针对高频变压器铁心通常是工作在方波或脉宽调制(PWM)波等非正弦激励下的特点,对传统Steinmetz损耗计算模型进行了优化改进,给出了考虑磁密的变化率及波形系数对损耗的影响的Steinmetz改进损耗模型。同时,为了提高损耗模型在不同特征频率下的通用性,进一步对损耗模型系数的非线性进行研究,给出了模型系数随频率变化的非线性函数。最后,利用有限元计算结果同实物测量结果进行比较,证明了所提损耗模型在方波激励下对纳米晶体铁心计算的准确性。