Symmetry-Basel最新文献_第7页

Generalized Orthopair Fuzzy Weighted Power Bonferroni Mean Operator and Its Application in Decision Making 广义矫形模糊加权幂Bonferroni均值算子及其在决策中的应用

3区综合性期刊

Symmetry-Basel Pub Date : 2023-10-31 DOI: 10.3390/sym15112007

Bowen Hou, Yongming Chen

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引用次数: 0

Effective Two-Phase Heuristic and Lower Bounds for Multi-Stage Flexible Flow Shop Scheduling Problem with Unloading Times 带卸载时间的多阶段柔性流水车间调度问题的有效两阶段启发式及下界

3区综合性期刊

Symmetry-Basel Pub Date : 2023-10-31 DOI: 10.3390/sym15112005

Lotfi Hidri

{"title":"Effective Two-Phase Heuristic and Lower Bounds for Multi-Stage Flexible Flow Shop Scheduling Problem with Unloading Times","authors":"Lotfi Hidri","doi":"10.3390/sym15112005","DOIUrl":"https://doi.org/10.3390/sym15112005","url":null,"abstract":"This paper addresses the flexible flow shop scheduling problem with unloading operations, which commonly occurs in modern manufacturing processes like sand casting. Although only a few related works have been proposed in the literature, the significance of this problem motivates the need for efficient algorithms and the exploration of new properties. One interesting property established is the symmetry of the problem, where scheduling from the first stage to the last or vice versa yields the same optimal solution. This property enhances solution quality. Considering the problem’s theoretical complexity as strongly NP-Hard, approximate solutions are preferable, especially for medium and large-scale instances. To address this, a new two-phase heuristic is proposed, consisting of a constructive phase and an improvement phase. This heuristic builds upon an existing efficient heuristic for the parallel machine-scheduling problem and extends it to incorporate unloading times efficiently. The selection of the two-phase heuristic is justified by its ability to generate high-quality schedules at each stage. Moreover, new efficient lower bounds based on estimating minimum idle time in each stage are presented, utilizing the polynomial parallel machine-scheduling problem with flow time minimization in the previous stage. These lower bounds contribute to assessing the performance of the two-phase heuristic over the relative gap performance measure. Extensive experiments are conducted on benchmark test problems, demonstrating the effectiveness of the proposed algorithms. The results indicate an average computation time of 9.92 s and a mean relative gap of only 2.80% for several jobs up to 200 and several stages up to 10.","PeriodicalId":48874,"journal":{"name":"Symmetry-Basel","volume":"108 7","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135810387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Self-Supervised Spatiotemporal Masking Strategy-Based Models for Traffic Flow Forecasting 基于自监督时空掩蔽策略的交通流量预测模型

3区综合性期刊

Symmetry-Basel Pub Date : 2023-10-31 DOI: 10.3390/sym15112002

Gang Liu, Silu He, Xing Han, Qinyao Luo, Ronghua Du, Xinsha Fu, Ling Zhao

{"title":"Self-Supervised Spatiotemporal Masking Strategy-Based Models for Traffic Flow Forecasting","authors":"Gang Liu, Silu He, Xing Han, Qinyao Luo, Ronghua Du, Xinsha Fu, Ling Zhao","doi":"10.3390/sym15112002","DOIUrl":"https://doi.org/10.3390/sym15112002","url":null,"abstract":"Traffic flow forecasting is an important function of intelligent transportation systems. With the rise of deep learning, building traffic flow prediction models based on deep neural networks has become a current research hotspot. Most of the current traffic flow prediction methods are designed from the perspective of model architectures, using only the traffic features of future moments as supervision signals to guide the models to learn the spatiotemporal dependence in traffic flow. However, traffic flow data themselves contain rich spatiotemporal features, and it is feasible to obtain additional self-supervised signals from the data to assist the model to further explore the underlying spatiotemporal dependence. Therefore, we propose a self-supervised traffic flow prediction method based on a spatiotemporal masking strategy. A framework consisting of symmetric backbone models with asymmetric task heads were applied to learn both prediction and spatiotemporal context features. Specifically, a spatiotemporal context mask reconstruction task was designed to force the model to reconstruct the masked features via spatiotemporal context information, so as to assist the model to better understand the spatiotemporal contextual associations in the data. In order to avoid the model simply making inferences based on the local smoothness in the data without truly learning the spatiotemporal dependence, we performed a temporal shift operation on the features to be reconstructed. The experimental results showed that the model based on the spatiotemporal context masking strategy achieved an average prediction performance improvement of 1.56% and a maximum of 7.72% for longer prediction horizons of more than 30 min compared with the backbone models.","PeriodicalId":48874,"journal":{"name":"Symmetry-Basel","volume":"96 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135810615","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Symmetry in the Bit-Stream Converter Design 位流转换器设计中的对称性

3区综合性期刊

Symmetry-Basel Pub Date : 2023-10-31 DOI: 10.3390/sym15112006

Olga Bureneva, Nikolay Safyannikov, Sergey Mironov

引用次数: 0

Impact of Inertial Forces on Car Occupants in a Vehicle-Fixed Barrier Front Crash 车辆固定屏障正面碰撞中惯性力对乘员的影响

3区综合性期刊

Symmetry-Basel Pub Date : 2023-10-30 DOI: 10.3390/sym15111998

Stanimir Karapetkov, Hristo Uzunov, Silvia Dechkova, Vasil Uzunov

引用次数: 0

Euclidean Jordan Algebras, Symmetric Association Schemes, Strongly Regular Graphs, and Modified Krein Parameters of a Strongly Regular Graph 欧几里得Jordan代数，对称关联方案，强正则图，以及强正则图的修正Krein参数