共查询到20条相似文献,搜索用时 140 毫秒
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为进一步研究透平膨胀机使用不同种工质时力性能的转化问题,在自行提出的透平膨胀机性能预测方法的基础上,应用人工神经网络,建立了一种新型的透平膨胀机热力性能转化方法,经实验结果验证,该方法合理有效。 相似文献
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在自行开发的以一元流动理论为基础的透平膨胀机性能预测方法的基础上,经过推导,获得了透平膨胀机使用同种工质时的决定性相似准则,即特性比,膨胀比及叶轮进圆周马赫数中的任意两个,为组织同种工质的模化试验,也为进一步研究透平膨胀机使用不同种工质时决定性相似准则的选取奠定了基础。 相似文献
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着重介绍所开发的新型氦气体轴承透平膨胀机的主要设计参数及关键部件的结构,该氦气体轴承透平膨胀机用于空间环境模拟的氦制冷系统,在设计中,利用多目标优化程序获得了较好的热力性能及较高的失稳转速,同时还开展了不同工质的相似模化研究,以便更好地预测氦透平膨胀机的热力性能,为了测试透平膨胀机的热力性能及机械性能,进行了多次的常温空气试车及液氮级温度低温试车,试验结果及现场实际车结果表明氦气体轴承透平膨胀机具有优异的热力性能及机械性能,满足了神舟号飞船发射前的热真空试验要求。 相似文献
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应用于透平机械的相似模化方法评述 总被引:2,自引:0,他引:2
为解决氦透平膨胀机的相似模化试验问题,本文首先总结了以往选取透平机械相似准则的方法,进而对这些选取相似准则组织透平机械模化试验的各种方法进行了评论,其中重点评术透平机械中应用具有不同绝热指数的工质进行模化试验的多种方法,为研究以空气代替氦气进行氦透平膨胀机性能试验的问题奠定了基础。 相似文献
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通过透平膨胀机在天然气分离装置中的长期运转试验,介绍天然气透平膨胀机的特点及 PT501型中压小功率透平膨胀机的特性。根据试验结果分析了天然气中混入的固体微粒及液滴对透平膨胀机性能的影响。对流道侵蚀现象进行初步的探讨,并根据试验结果对带液后叶轮叶型改进提出初步的设想。 相似文献
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通过对相似理论因次分析原理的应用,具体阐述了低温透平膨胀机的性能测试及试验台的流程组织方法。包括进行性能试验时的必测参数、模拟试验时的约束条件、确定膨胀机性能的准则方程,以及各种试验方法的组成机理、适用范畴。提出对大容量透平膨胀机性能测试时,应以抽气膨胀低温试验台流程作为最佳方法,并用实例说明采用这种方法试验时的操作参数、试验气量及节约功耗值,图5参14。 相似文献
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Given the limitations of the community question answering (CQA)
answer quality prediction method in measuring the semantic information of the
answer text, this paper proposes an answer quality prediction model based on
the question-answer joint learning (ACLSTM). The attention mechanism is used
to obtain the dependency relationship between the Question-and-Answer (Q&A)
pairs. Convolutional Neural Network (CNN) and Long Short-term Memory Network (LSTM) are used to extract semantic features of Q&A pairs and calculate
their matching degree. Besides, answer semantic representation is combined with
other effective extended features as the input representation of the fully connected
layer. Compared with other quality prediction models, the ACLSTM model can
effectively improve the prediction effect of answer quality. In particular, the mediumquality answer prediction, and its prediction effect is improved after adding effective extended features. Experiments prove that after the ACLSTM model learning,
the Q&A pairs can better measure the semantic match between each other, fully
reflecting the model’s superior performance in the semantic information processing
of the answer text. 相似文献
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Iwona Paprocka 《国际生产研究杂志》2013,51(14):4480-4501
The accuracy of prediction and detection capability have a strong influence over the efficiency of the bottleneck, all equipment and the production system. The function of predictive scheduling is to obtain stable and robust schedules for a shop floor. The first objective is to present an innovative maintenance planning and production scheduling method. The approach consists of four modules: a database to collect information about failure-free times, a prediction module of failure-free times, predictive scheduling and rescheduling module, a module for evaluating the accuracy of prediction and maintenance performance. The second objective is to apply the proposed methods for a job shop scheduling problem. Usually, researchers who are concerned about maintenance scheduling do not take unexpected disturbances into account. They assume that machines are always available for processing tasks during the future-planned production time. Moreover, researches use the criteria that are not effective to deal with the situation of unpredicted failures. In this paper, a method based on probability theory is proposed for maintenance scheduling. For unpredicted failures, a rescheduling method is also proposed. The evaluation module which gives information about the degradation of each performance measure and the stability of a schedule is proposed. 相似文献
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基坑上跨开挖将会引起既有盾构隧道隆起变形,危及既有盾构隧道的服役性能。目前基坑开挖引起的盾构隧道隆起变形的解析方法,通常将盾构隧道简化为埋置于弹性地基上的连续长梁,忽略了环间接头影响。针对前人研究的不足,提出带环间接头的盾构隧道计算模型,通过非线性Pasternak地基模型来考虑地基土变形的非线性特征,通过两阶段分析法,推导得到基坑上跨开挖作用下盾构隧道隆起位移和张开量简化解答。通过MINDLIN解计算基坑开挖引起的作用于盾构隧道上的附加荷载;建立基坑卸载下盾构隧道的隆起变形微分方程。利用有限差分法求解出基坑开挖引起的邻近盾构隧道隆起变形和内力分布。收集了三个工程实测数据,并将所提方法和实测数据、既有理论方法进行对比,验证所提方法的适用性。 相似文献
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空间变异边坡可靠度计算需要进行多次重复性边坡稳定性分析,常用的边坡稳定性分析极限平衡方法(LEM)计算效率较高而有限元方法(FEM)可捕捉真实的边坡失效机制,边坡可靠度评价中如能充分利用这两者的优势将具有重要的工程价值。该文在发展考虑参数空间变异性边坡可靠度分析的一阶可靠度方法(FORM)基础上,提出基于模型修正的空间变异边坡可靠度分析方法,引入一修正系数将基于LEM的简化极限状态面逐渐修正为基于FEM的准确极限状态面,最后基于修正系数和LEM安全系数计算公式采用线抽样法计算边坡失效概率。通过一个考虑参数空间变异性的摩擦/粘性土坡算例验证提出方法的有效性,并探讨土体参数空间变异性和黏聚力与内摩擦角之间互相关性对边坡可靠度的影响。结果表明:提出方法的边坡可靠度计算精度与基于FEM子集模拟方法一致,但是计算效率远远大于后者,尤其对于低概率水平边坡可靠度问题,从而为解决考虑土体参数空间变异性的低概率水平边坡可靠度问题提供一条新的途径。 相似文献
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The objective of this paper is to develop a micromechanics model for the onset and subsequent multiplication of transverse cracks in the 90° layers of a cross-ply laminate under uniaxial tension. The micromechanics study of transverse matrix cracking is performed by a combination of finite element and analytical analyses. Based on the Griffith fracture criterion, the evolution of transverse matrix crack density is predicted. The prediction compares well with existing experimental data in the literature. Analytical expressions of the non-linear effective stress–strain curves are also obtained for a wide range of material systems. In addition, an analytical expression of the effective stiffness is derived based on the differential self-consistent method. The analytical results agree very well with the finite element calculations. 相似文献