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Strong Convergence of Euler-Type Methods for Nonlinear Fractional Stochastic Differential Equations without Singular Kernel 无奇异核的非线性分式随机微分方程欧拉型方法的强收敛性
IF 2.4 3区 数学 Q1 MATHEMATICS Pub Date : 2024-09-16 DOI: 10.3390/math12182890
Zakaria Ali, Minyahil Abera Abebe, Talat Nazir
In this paper, we first prove the existence and uniqueness of the solution to a variable-order Caputo–Fabrizio fractional stochastic differential equation driven by a multiplicative white noise, which describes random phenomena with non-local effects and non-singular kernels. The Euler–Maruyama scheme is extended to develop the Euler–Maruyama method, and the strong convergence of the proposed method is demonstrated. The main difference between our work and the existing literature is the fact that our assumptions on the nonlinear external forces are those of one-sided Lipschitz conditions on both the drift and the nonlinear intensity of the noise as well as the proofs of the higher integrability of the solution and the approximating sequence. Finally, to validate the numerical approach, current results from the numerical implementation are presented to test the efficiency of the scheme used in order to substantiate the theoretical analysis.
本文首先证明了由乘法白噪声驱动的变阶卡普托-法布里齐奥分数随机微分方程解的存在性和唯一性,该方程描述了具有非局部效应和非星核的随机现象。我们对 Euler-Maruyama 方案进行了扩展,开发出了 Euler-Maruyama 方法,并证明了所提出方法的强大收敛性。我们的工作与现有文献的主要区别在于,我们对非线性外力的假设是对漂移和噪声非线性强度的单边 Lipschitz 条件,以及对解和近似序列的高积分性的证明。最后,为了验证数值方法的有效性,介绍了当前的数值实施结果,以测试所用方案的效率,从而证实理论分析的正确性。
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引用次数: 0
Stochastic Differential Games and a Unified Forward–Backward Coupled Stochastic Partial Differential Equation with Lévy Jumps 随机微分博弈和带列维跳跃的统一前后耦合随机偏微分方程
IF 2.4 3区 数学 Q1 MATHEMATICS Pub Date : 2024-09-16 DOI: 10.3390/math12182891
Wanyang Dai
We establish a relationship between stochastic differential games (SDGs) and a unified forward–backward coupled stochastic partial differential equation (SPDE) with discontinuous Lévy Jumps. The SDGs have q players and are driven by a general-dimensional vector Lévy process. By establishing a vector-form Ito-Ventzell formula and a 4-tuple vector-field solution to the unified SPDE, we obtain a Pareto optimal Nash equilibrium policy process or a saddle point policy process to the SDG in a non-zero-sum or zero-sum sense. The unified SPDE is in both a general-dimensional vector form and forward–backward coupling manner. The partial differential operators in its drift, diffusion, and jump coefficients are in time-variable and position parameters over a domain. Since the unified SPDE is of general nonlinearity and a general high order, we extend our recent study from the existing Brownian motion (BM)-driven backward case to a general Lévy-driven forward–backward coupled case. In doing so, we construct a new topological space to support the proof of the existence and uniqueness of an adapted solution of the unified SPDE, which is in a 4-tuple strong sense. The construction of the topological space is through constructing a set of topological spaces associated with a set of exponents {γ1,γ2,…} under a set of general localized conditions, which is significantly different from the construction of the single exponent case. Furthermore, due to the coupling from the forward SPDE and the involvement of the discontinuous Lévy jumps, our study is also significantly different from the BM-driven backward case. The coupling between forward and backward SPDEs essentially corresponds to the interaction between noise encoding and noise decoding in the current hot diffusion transformer model for generative AI.
我们建立了随机微分博弈(SDGs)与具有不连续莱维跳跃的统一前后耦合随机偏微分方程(SPDE)之间的关系。SDGs 有 q 个参与者,由一般维度的向量 Lévy 过程驱动。通过建立向量形式的伊托-文采公式和统一 SPDE 的 4 元组向量场解,我们得到了帕累托最优纳什均衡政策过程或非零和或零和意义上的 SDG 鞍点政策过程。统一的 SPDE 既有通维向量形式,也有前后耦合方式。其漂移、扩散和跃迁系数中的偏微分算子是域上的时变参数和位置参数。由于统一 SPDE 具有一般非线性和一般高阶,我们将最近的研究从现有的布朗运动(BM)驱动的后向情况扩展到一般的莱维驱动的前向后向耦合情况。在此过程中,我们构建了一个新的拓扑空间,以支持证明统一 SPDE 的适应解的存在性和唯一性,该解在 4 元组强意义上。拓扑空间的构建是通过在一组一般局部条件下构建一组与一组指数{γ1,γ2,...}相关联的拓扑空间,这与单指数情况下的构建有显著不同。此外,由于前向 SPDE 的耦合和不连续 Lévy 跳变的参与,我们的研究也与 BM 驱动的后向情况有显著不同。前向 SPDE 与后向 SPDE 之间的耦合基本上对应于当前生成式人工智能热扩散变压器模型中噪声编码与噪声解码之间的相互作用。
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引用次数: 0
Rayleigh Waves in a Thermoelastic Half-Space Coated by a Maxwell–Cattaneo Thermoelastic Layer 由 Maxwell-Cattaneo 热弹性层包裹的热弹性半空间中的瑞利波
IF 2.4 3区 数学 Q1 MATHEMATICS Pub Date : 2024-09-16 DOI: 10.3390/math12182885
Stan Chiriţă, Ciro D’Apice
This paper investigates the propagation of in-plane surface waves in a coated thermoelastic half-space. First, it investigates a special case where the surface layer is described by the Maxwell–Cattaneo thermoelastic approach, while the half-space is filled by a thermoelastic material described by the classical Fourier law for the heat flux. The contact between the layer and the half-space is assumed to be welded, i.e., the displacements and the temperature, as well as the stresses and the heat flux are continuous through the interface of the layer and the half-space. The boundary and continuity conditions of the problem are formulated and then the exact dispersion relation of the surface waves is established. An illustrative numerical simulation is presented for the case of an aluminum thermoelastic layer coating a thermoelastic copper half-space, highlighting important aspects regarding the propagation of Rayleigh waves in such structures. The exact effective boundary conditions at the interface are also established replacing the entire effect of the layer on the half-space. The general case of the problem is also investigated when both the surface layer and the half-space are described by the Maxwell–Cattaneo thermoelasticity theory. This study helps to further understand the propagation characteristics of elastic waves in layered structures with thermal effects described by the Maxwell–Cattaneo approach.
本文研究了平面内表面波在有涂层的热弹性半空间中的传播。首先,本文研究了一种特殊情况,即表面层由 Maxwell-Cattaneo 热弹性方法描述,而半空间由热弹性材料填充,热通量由经典傅里叶定律描述。假设层与半空间之间的接触是焊接的,即通过层与半空间的界面,位移、温度、应力和热通量是连续的。首先制定了问题的边界和连续性条件,然后建立了表面波的精确频散关系。针对铝热弹性层包裹热弹性铜半空间的情况,进行了示例性数值模拟,强调了雷利波在此类结构中传播的重要方面。此外,还确定了界面处的精确有效边界条件,以取代该层对半空间的全部影响。当表面层和半空间都用 Maxwell-Cattaneo 热弹性理论描述时,还研究了问题的一般情况。这项研究有助于进一步理解用 Maxwell-Cattaneo 方法描述热效应的层状结构中弹性波的传播特性。
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引用次数: 0
HyperCLR: A Personalized Sequential Recommendation Algorithm Based on Hypergraph and Contrastive Learning HyperCLR:基于超图和对比学习的个性化序列推荐算法
IF 2.4 3区 数学 Q1 MATHEMATICS Pub Date : 2024-09-16 DOI: 10.3390/math12182887
Ruiqi Zhang, Haitao Wang, Jianfeng He
Sequential recommendations aim to predict users’ next interactions by modeling their interaction sequences. Most existing work concentrates on user preferences within these sequences, overlooking the complex item relationships across sequences. Additionally, these studies often fail to address the diversity of user interests, thus not capturing their varied latent preferences effectively. To tackle these problems, this paper develops a novel recommendation algorithm based on hypergraphs and contrastive learning named HyperCLR. It dynamically incorporates the time and location embeddings of items to model high-order relationships in user preferences. Moreover, we developed a graph construction approach named IFDG, which utilizes global item visit frequencies and spatial distances to discern item relevancy. By sampling subgraphs from IFDG, HyperCLR can align the representations of identical interaction sequences closely while distinguishing them from the broader global context on IFDG. This approach enhances the accuracy of sequential recommendations. Furthermore, a gating mechanism is designed to tailor the global context information to individual user preferences. Extensive experiments on Taobao, Books and Games datasets have shown that HyperCLR consistently surpasses baselines, demonstrating the effectiveness of the method. In particular, in comparison to the best baseline methods, HyperCLR demonstrated a 29.1% improvement in performance on the Taobao dataset.
序列推荐旨在通过对用户的交互序列建模来预测用户的下一次交互。现有的大多数工作都集中在这些序列中的用户偏好上,而忽略了序列间复杂的项目关系。此外,这些研究往往未能解决用户兴趣的多样性问题,因此无法有效捕捉用户的各种潜在偏好。为了解决这些问题,本文开发了一种基于超图和对比学习的新型推荐算法,命名为 HyperCLR。它动态地结合了项目的时间和地点嵌入,为用户偏好中的高阶关系建模。此外,我们还开发了一种名为 IFDG 的图构建方法,它利用全局项目访问频率和空间距离来判别项目相关性。通过从 IFDG 中抽取子图,HyperCLR 可以使相同交互序列的表示紧密一致,同时将它们与 IFDG 上更广泛的全局上下文区分开来。这种方法提高了顺序推荐的准确性。此外,HyperCLR 还设计了一种门控机制,可根据用户的个人偏好定制全局上下文信息。在淘宝、图书和游戏数据集上进行的大量实验表明,HyperCLR 始终超越基线,证明了该方法的有效性。特别是,与最佳基准方法相比,HyperCLR 在淘宝数据集上的性能提高了 29.1%。
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引用次数: 0
On Properties of the Hyperbolic Distribution 论双曲线分布的性质
IF 2.4 3区 数学 Q1 MATHEMATICS Pub Date : 2024-09-16 DOI: 10.3390/math12182888
Roman V. Ivanov
This paper is set to analytically describe properties of the hyperbolic distribution. This law, along with the variance-gamma distribution, is one of the most popular normal mean–variance mixtures from the point of view of various applications. We have found closed form expressions for the cumulative distribution and partial-moment-generating functions of the hyperbolic distribution. The obtained formulas use the values of the Humbert confluent hypergeometric and Whittaker special functions. The results are applied to the problem of European option pricing in the related Lévy model of financial market. The research demonstrates that the discussed normal mean–variance mixture is analytically tractable.
本文旨在分析描述双曲线分布的特性。从各种应用的角度来看,该定律与方差-伽马分布是最常用的正态均方差混合物之一。我们找到了双曲线分布的累积分布和部分动量生成函数的封闭式表达式。所获得的公式使用了亨伯特汇合双曲函数和惠特克特殊函数的值。研究结果被应用于金融市场相关莱维模型中的欧式期权定价问题。研究表明,所讨论的正态均值-方差混合物在分析上是可行的。
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引用次数: 0
C-Semigroups and Their Induced Order C 族半群及其诱导有序
IF 2.4 3区 数学 Q1 MATHEMATICS Pub Date : 2024-09-16 DOI: 10.3390/math12182889
Daniel Marín-Aragón, Raquel Tapia-Ramos
Let C⊂Np be an integer polyhedral cone. An affine semigroup S⊂C is a C-semigroup if |C∖S|<+∞. This structure has always been studied using a monomial order. The main issue is that the choice of these orders is arbitrary. In the present work, we choose the order given by the semigroup itself, which is a more natural order. This allows us to generalise some of the definitions and results known from numerical semigroup theory to C-semigroups.
设 C⊂Np 是一个整数多面体圆锥。如果 |C∖S|<+∞,则仿射半群 S⊂C 是一个 C 半群。对这种结构的研究一直使用单项式阶。主要问题在于这些阶的选择是任意的。在本研究中,我们选择半群本身给出的阶,这是一种更自然的阶。这使我们能够将数字半群理论中的一些定义和结果推广到 C 半群。
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引用次数: 0
Fixed-Point and Random Fixed-Point Theorems in Preordered Sets Equipped with a Distance Metric 配备距离度量的有序集合中的定点定理和随机定点定理
IF 2.4 3区 数学 Q1 MATHEMATICS Pub Date : 2024-09-15 DOI: 10.3390/math12182877
Himanshu Baranwal, Ravindra Kishor Bisht, Arya Kumar Bedabrata Chand, Jen-Chih Yao
This paper explores fixed points for both contractive and non-contractive mappings in traditional b-metric spaces, preordered b-metric spaces, and random b-metric spaces. Our findings provide insights into the behavior of mappings under various constraints and extend our approach to include coincidence and common fixed-point theorems in these spaces. We present new examples and graphical representations for the first time, offering novel results and enhancing several related findings in the literature, while broadening the scope of earlier works of Ran and Reurings, Nieto and Rodríguez-López, Górnicki, and others.
本文探讨了传统二元空间、有序二元空间和随机二元空间中的收缩映射和非收缩映射的定点。我们的发现让我们深入了解了各种约束条件下的映射行为,并将我们的方法扩展到这些空间中的重合和共同定点定理。我们首次提出了新的示例和图形表示,提供了新的结果,并增强了文献中的一些相关发现,同时拓宽了 Ran 和 Reurings、Nieto 和 Rodríguez-López、Górnicki 等人早期著作的范围。
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引用次数: 0
Applications of the Hahn-Banach Theorem, a Solution of the Moment Problem and the Related Approximation 哈恩-巴拿赫定理的应用、矩问题的解法及相关近似法
IF 2.4 3区 数学 Q1 MATHEMATICS Pub Date : 2024-09-15 DOI: 10.3390/math12182878
Octav Olteanu
We start by an application the of Krein–Milman theorem to the integral representation of completely monotonic functions. Elements of convex optimization are also mentioned. The paper continues with applications of Hahn–Banach-type theorems and polynomial approximation to obtain recent results on the moment problem on the unbounded closed interval . Necessary and sufficient conditions for the existence and uniqueness of the solution are pointed out. Operator-valued moment problems and a scalar-valued moment problem are solved.
我们首先将 Krein-Milman 定理应用于完全单调函数的积分表示。文中还提到了凸优化的要素。接着,论文应用哈恩-巴纳奇(Hahn-Banach)型定理和多项式逼近法,得出了无界闭合区间上矩问题的最新结果。论文指出了解的存在性和唯一性的必要条件和充分条件。解决了算子值矩问题和标量值矩问题。
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引用次数: 0
Mathematical Formulations for Predicting Pressure Drop in Solid–Liquid Slurry Flow through a Straight Pipe Using Computational Modeling 利用计算建模预测固液浆液流经直管时压降的数学公式
IF 2.4 3区 数学 Q1 MATHEMATICS Pub Date : 2024-09-15 DOI: 10.3390/math12182879
Tanuj Joshi, Abhinav Gupta, Om Parkash, Ralph Kristoffer B. Gallegos, Nay Lin Oo, Gopal Krishan
The study establishes two mathematical formulations to predict the pressure drop in a solid–liquid slurry flowing through a straight pipe. Employing the Eulerian–Eulerian RNG k-ε model, the computational investigation uses water as the carrier fluid and glass beads as solid particles. The analysis spans various particle sizes (d50 = 75–175 μm), volumetric concentrations (Cvf = 10–50%), and velocities (Vm = 1–5 m/s). The first model, developed using the MATLAB curve-fitting tool, is complemented by a second empirical equation derived through non-polynomial mathematical formulation. Results from both models are validated against existing experimental and computational data, demonstrating accurate predictions for d50 = 75–175 µm particles within a Reynolds number range of 20,000 ≤ Re ≤ 320,000.
该研究建立了两种数学公式来预测流经直管的固液浆液的压降。计算研究采用欧拉-欧拉 RNG k-ε 模型,以水为载液,玻璃珠为固体颗粒。分析跨越了各种颗粒尺寸(d50 = 75-175 μm)、体积浓度(Cvf = 10-50%)和速度(Vm = 1-5 m/s)。第一个模型是利用 MATLAB 曲线拟合工具开发的,第二个模型是通过非多项式数学公式推导出的经验方程的补充。两个模型的结果都与现有的实验和计算数据进行了验证,在雷诺数 20,000 ≤ Re ≤ 320,000 的范围内对 d50 = 75-175 µm 的颗粒进行了精确预测。
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引用次数: 0
Multi-Type Self-Attention-Based Convolutional-Neural-Network Post-Filtering for AV1 Codec 用于 AV1 编解码器的基于卷积神经网络的多类型自注意后过滤技术
IF 2.4 3区 数学 Q1 MATHEMATICS Pub Date : 2024-09-15 DOI: 10.3390/math12182874
Woowoen Gwun, Kiho Choi, Gwang Hoon Park
Over the past few years, there has been substantial interest and research activity surrounding the application of Convolutional Neural Networks (CNNs) for post-filtering in video coding. Most current research efforts have focused on using CNNs with various kernel sizes for post-filtering, primarily concentrating on High-Efficiency Video Coding/H.265 (HEVC) and Versatile Video Coding/H.266 (VVC). This narrow focus has limited the exploration and application of these techniques to other video coding standards such as AV1, developed by the Alliance for Open Media, which offers excellent compression efficiency, reducing bandwidth usage and improving video quality, making it highly attractive for modern streaming and media applications. This paper introduces a novel approach that extends beyond traditional CNN methods by integrating three different self-attention layers into the CNN framework. Applied to the AV1 codec, the proposed method significantly improves video quality by incorporating these distinct self-attention layers. This enhancement demonstrates the potential of self-attention mechanisms to revolutionize post-filtering techniques in video coding beyond the limitations of convolution-based methods. The experimental results show that the proposed network achieves an average BD-rate reduction of 10.40% for the Luma component and 19.22% and 16.52% for the Chroma components compared to the AV1 anchor. Visual quality assessments further validated the effectiveness of our approach, showcasing substantial artifact reduction and detail enhancement in videos.
在过去几年中,围绕卷积神经网络(CNN)在视频编码中用于后过滤的应用产生了浓厚的兴趣并开展了大量研究活动。目前的大部分研究工作都集中在使用具有不同内核大小的 CNN 进行后过滤,主要集中在高效视频编码/H.265 (HEVC) 和多功能视频编码/H.266 (VVC)。这种狭隘的关注点限制了这些技术对其他视频编码标准的探索和应用,如开放媒体联盟开发的 AV1,它具有出色的压缩效率,可减少带宽使用并提高视频质量,对现代流媒体和媒体应用极具吸引力。本文介绍了一种超越传统 CNN 方法的新方法,即在 CNN 框架中集成三个不同的自我关注层。在 AV1 编解码器中应用时,通过整合这些不同的自我注意层,所提出的方法显著提高了视频质量。这一改进表明,自注意机制具有超越基于卷积的方法的限制,彻底改变视频编码中的后过滤技术的潜力。实验结果表明,与 AV1 锚点相比,拟议网络的 Luma 部分平均 BD 速率降低了 10.40%,Chroma 部分降低了 19.22% 和 16.52%。视觉质量评估进一步验证了我们方法的有效性,显示了视频中人工痕迹的显著减少和细节的增强。
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