共查询到20条相似文献,搜索用时 906 毫秒
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尺寸效应的研究在评估节理/裂隙岩体力学性质方面具有重要意义,通过离散元数值方法研究尺寸效应。引入Voronoi图模拟随机节理,以相对标准差为标准,衡量试验结果的稳定性和可靠度,进行了足够次数不同尺寸的单轴压缩数值试验。进而采用统计方法分析Eeq(等效弹性模量)和1/Eeq(等效柔量)的尺寸效应。研究表明:相对标准差值为5%对应的变形REV(representative elementary volume)尺寸约为4倍Voronoi多边形平均边长;样本Eeq的均值随着尺寸的增大显著降低,而样本1/Eeq的均值随尺寸变化很小。对结论的适用性进行了分析,实际工程中多采用样本Eeq的均值估算岩体的整体等效弹性模量,建议同时采用1/Eeq均值的倒数估算其下限。并将此方法应用于白鹤滩水电站节理岩体原位变形试验成果的分析。 相似文献
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我国第一部《室内空气质量标准》(GB/T1 8883 - 2 0 0 2 )从今年 3月 1日起实施 ,该《标准》的主要控制指标见下表 :序号参数及单位标准值备注1温度 (℃ ) 2 2~ 2 81 6~ 2 4夏季空调冬季采暖2相对湿度 (% ) 4 0~ 8030~ 60夏季空调冬季采暖3空气流速 (m/s) 0 30 2夏季空调冬季采暖4新风量 (m3/hp) 305 二氧化硫 (mg/m3) 0 50 1h均值6二氧化氮 (mg/m3) 0 2 4 1h均值7一氧化碳 (mg/m3) 1 0 1h均值8二氧化碳 (% ) 0 1 0日平均值序号参数及单位标准值备注9氨 (mg/m3) 0 2 0 1h均值1 0 臭氧 (mg/m3) 0 1 6 1h均值1 1 甲醛 (mg/m3) 0 … 相似文献
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《高分子材料科学与工程》2017,(4)
选用价廉无毒的碳酸氢钠(NaHCO_3)作为发泡剂,利用反溶剂重结晶法进行细化,成功地制备出超细NaHCO_3粒子。最佳制备条件为:使用10%质量分数的NaHCO_3,蒸馏水与无水乙醇体积比1∶14,搅拌速度1100 r/min,制备温度-5℃,入料速度1 m L/min。纳米粒度分析仪测试表明NaHCO_3平均尺寸为143.2 nm,尺寸分布非常窄。将超细NaHCO_3添加到聚丙烯(PP)中进行微孔发泡,使用扫描电镜观察并使用Nano Measurer分析泡孔尺寸,表明当NaHCO_3用量为4.5 phr时,其泡孔平均尺寸低至0.47μm,泡孔尺寸标准方差仅为0.16μm,低于任何文献报道值。力学性能较优,其中拉伸强度下降了9.6%,而冲击强度提高了47.8%,弯曲强度提高了20.2%。这种使用普通注塑机获得高质量低成本的微孔发泡材料,对微孔材料的制备和应用有一定的意义。 相似文献
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研究了HCSA膨胀剂3种掺量(0%、3%、6%)下常温养护型超高性能混凝土(Ultra high performance concrete,UHPC)的圆环约束收缩性能,包括:(1)UHPC轴拉应力应变曲线测试;(2)根据GB/T50082的UHPC自由收缩实验;(3)根据ASTM C1581的UHPC圆环约束实验。结果表明,3种UHPC的极限拉伸应变均高于3 000με,28d总收缩值分别为1 005.6με、600.0με、462.2με,并且在圆环约束作用下转化为残余应变、弹性拉应变和塑性拉应变,其中塑性拉应变分别为700.4με、437.9με、389.9με。3种UHPC在拉伸应变达到1 000με时及圆环约束实验中均未发现0.01mm以上的可检测裂缝。基于拉伸实验和声发射损伤分析方法对UHPC进行应变分析,可知具有应变强化段的3种UHPC在圆环约束实验中的塑性变形以小于0.01mm的多点分布微裂纹形式存在。通过添加HCSA膨胀剂对常温养护型UHPC进行收缩补偿,可有效地降低UHPC自身的拉应力以及对原有结构的影响。 相似文献
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针对目前铝型材表面缺陷检测存在的准确率、检测效率较低等问题,提出了一种基于改进的YOLOv3铝型材表面缺陷检测方法。首先通过k-均值聚类算法对采集到的数据集进行聚类分析,选取尺寸最优的目标候选框;考虑到铝型材表面缺陷较大,对YOLOv3的网络层级结构进行调整,并将目标检测层之前的6个CBL单元改成4个,再补充2个残差单元,以提高特征的复用。将提出方法用于铝型材表面缺陷检测,并与经典的卷积网络Faster-RCNN和SSD方法进行比较,实验结果表明,采用提出的算法准确率达到97%,检测速度达到47帧/s,明显优于经典的卷积网络Faster-RCNN和SSD,适于在有高精度快速性要求的铝型材表面缺陷检测中推广应用。 相似文献
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通过对单个R0CCO圆环的静力试验和理论分析,推导了圆环等效半径的计算方法。建立了两种组合形式环形网的计算模型:第一种组合形式(模型1)中1个R0CCO圆环与4个R0CCO圆环相连接;第二种组合形式(模型2)中1个R0CCO圆环与6个R0CCO圆环相连接,采用数值分析方法对模型1、2的静动力耗能性能进行了研究。结果表明:①当采用相同的ROCCO圆环组成模型1、2时,模型2中单个ROCCO圆环的耗能能力高于模型1;②当采用相等的材料组成模型1、2时,在相同动能的落石冲击作用下,模型2的变形距离低于模型1,且模型1受到的落石冲击荷载开始时低于模型2,随着落石直径的增大,逐渐高于模型2;③模型1、模型2在落石冲击作用下的极限耗能能力随着落石直径的增大而逐渐增大,且模型1的极限耗能能力开始时高于模型2,当落石直径达到一定程度后,模型2的耗能能力逐渐高于模型1。因此,当实际工程中需要考虑防护系统变形距离时,选择第二种组合形式的环形网可以节约工程造价,而当需要考虑系统极限耗能能力时,可以根据落石特征选择经济合理的环形网结构形式。 相似文献
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我厂生产的50米3/时制氧机分馏塔管路中,为了专供插铂热电阻温度计用而增设了三种节头,如图1所示,材料均为T2,具体尺寸见表1 相似文献
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如果一个图G的邻接矩阵A(G)的特征多项式的所有特征值全为整数,则称图G是整的.设图L2(Kp):L(s(Kp))是完全图Kp的剖分图S(Kp)的线图.在这篇文章里,我们利用图的理论给出了S(Kp)和L2(Kp)的特征多项式及其谱.对于图L2(Kp),得到了其补图、线图、线图的补图及补图的线图的特征多项式.也证明了这些图都是整图.这些整图的发现是对整图的研究的一个新贡献. 相似文献
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针对大规模图集的子图查询问题,给出了一种基于节点与决策模式映射(NDFM)的索引结构——NDFM-Index,并在此索引结构的基础上提出了一种图集的子图查询算法。NDFM-Index利用图中关键节点所携带的结构信息以及邻居的标号分布,与决策模式形成映射,从而不通过枚举直接得到查询图所包含的索引模式,得到更小的候选集。理论与实验的分析结果表明,该算法不但能避免索引筛选过程中对查询图子图的枚举过程,而且能显著地减小候选集尺寸,进而大大降低查询图与候选集之间的子图同构测试次数,提高查询效率。 相似文献
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The paper presents a formal graph representation scheme for stamping operation sequencing for sheetmetal progressive dies and a graph theoretic method for automatic determination of the stamping operation sequence. Operation relations are represented by two graphs: an operation precedence graph and an adjacency graph. The first represents precedence constraints defined by best manufacturing practices. The second represents geometric infeasibility relations between operations. Each operation is a member of both graphs. The graphs are automatically generated from a set of stamping operations, which in turn are associated with stamping features of a part. The operation precedence graph is then verified to be acyclic using a coloured Depth First Search. Based on the operation precedence graph, a modified topological sort algorithm is applied to cluster the operations into partially ordered sets. Finally, a graph-colouring algorithm is applied to the operation adjacency graph on the partially ordered operation sets. The algorithm is implemented in C++ and is fully integrated with SolidWorks computer-aided design system. A case study is presented to illustrate the algorithm. 相似文献
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Action recognition has been recognized as an activity in which individuals’ behaviour can be observed. Assembling profiles of regular activities such as activities of daily living can support identifying trends in the data during critical events. A skeleton representation of the human body has been proven to be effective for this task. The skeletons are presented in graphs form-like. However, the topology of a graph is not structured like Euclidean-based data. Therefore, a new set of methods to perform the convolution operation upon the skeleton graph is proposed. Our proposal is based on the Spatial Temporal-Graph Convolutional Network (ST-GCN) framework. In this study, we proposed an improved set of label mapping methods for the ST-GCN framework. We introduce three split techniques (full distance split, connection split, and index split) as an alternative approach for the convolution operation. The experiments presented in this study have been trained using two benchmark datasets: NTU-RGB + D and Kinetics to evaluate the performance. Our results indicate that our split techniques outperform the previous partition strategies and are more stable during training without using the edge importance weighting additional training parameter. Therefore, our proposal can provide a more realistic solution for real-time applications centred on daily living recognition systems activities for indoor environments. 相似文献
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罗马控制是一个有丰富历史背景和数学背景的典型控制问题,它与计算机科学、交通安全监管控制、企业安全生产监管控制、组合优化、监视系统和社会网络等领域密切相关,具有重要的理论意义和应用价值。图的弱罗马控制数是图的弱罗马控制函数的最小权,记为$\gamma_{r}(G)$。图 $G$ 的控制集的最小基数称为最小控制数,记为 $\gamma(G)$。若图 $G$ 满足 $\gamma_{r}(G)=2\gamma(G)$,则称图 $G$ 是弱罗马图。用构造法确定了路 $P_{3}$,星 $K_{1, t} (t\geq2)$,由星 $K_{1, t_{1}},K_{1, t_{2}},\cdots,K_{1, t_{n}}\,(t_{i}\geq3, i=1,2,\cdots,n)$ 的中心点依次连接成一条路所构成的树 $T$,或由它们的外点连接构成的树$T$ 是弱罗马图,并给出了弱罗马图和图的弱罗马控制的一些性质。 相似文献
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A knowledge graph is a structured graph in which data obtained from multiple sources are standardized to acquire and integrate human knowledge. Research is being actively conducted to cover a wide variety of knowledge, as it can be applied to applications that help humans. However, existing researches are constructing knowledge graphs without the time information that knowledge implies. Knowledge stored without time information becomes outdated over time, and in the future, the possibility of knowledge being false or meaningful changes is excluded. As a result, they can’t reflect information that changes dynamically, and they can’t accept information that has newly emerged. To solve this problem, this paper proposes Time-Aware PolarisX, an automatically extended knowledge graph including time information. Time-Aware PolarisX constructed a BERT model with a relation extractor and an ensemble NER model including a time tag with an entity extractor to extract knowledge consisting of subject, relation, and object from unstructured text. Through two application experiments, it shows that the proposed system overcomes the limitations of existing systems that do not consider time information when applied to an application such as a chatbot. Also, we verify that the accuracy of the extraction model is improved through a comparative experiment with the existing model. 相似文献