Nonlinearity

非线性
  • 文章类型: Journal Article
    用于监测复杂结构的技术的迅速发展需要对损伤检测方法的精度进行主要关注。早期检测结构的任何类型的劣化或退化对于避免突然的灾难性故障至关重要。它警告用户有关系统即将出现的状态。在裂纹或其他系统故障开始时,在环境振动下,系统可能会产生随时间变化的裂纹状态。它代表了裂纹的非线性呼吸现象。对这种非线性程度的评估可用于检测,本地化,以及呼吸裂缝的量化。因此,需要对此类裂纹进行适当的建模,以捕获独特的非线性特征。认识到这一重要性,回顾了过去用于呼吸裂纹检测的各种建模和非线性系统识别方法。本研究还探讨了一些可用的振动以及基于声学的损伤识别技术,按时间顺序连接他们的进化。它总结了检查潜在未来应用的方法的优点和局限性。从这篇评论中得出的未来范围被强调为裂纹非线性特征的广泛应用铺平道路。
    Swift development of technology for monitoring complex structures demands major attention on the precision of damage detection methods. The early detection of any type of deterioration or degradation of structures is of paramount importance to avoid sudden catastrophic failure. It warns users about the impending state of the system. At the initiation of a crack or some other system faults, the system may generate a time-varying state of crack under ambient vibration. It represents the nonlinear breathing phenomena of crack. An assessment of this degree of nonlinearity can be utilized for the detection, localization, and quantification of breathing cracks. Appropriate modeling of such cracks is thus necessary to capture distinctive nonlinear features. Recognizing this importance, various methods of modeling and nonlinear system identification which have been employed in the past for the detection of breathing crack are reviewed. The present study also explores some of the available vibration as well as acoustic-based damage identification techniques, chronologically connecting their evolutions. It summarizes the advantages and limitations of the methods to inspect potential future applications. The future scopes drawn from this review are highlighted to pave the path of wide-spread applications of nonlinear features of crack.
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  • 文章类型: Journal Article
    动态系统理论和复杂性理论(DST/CT)是一个框架,解释了复杂系统如何随时间变化和适应。在心理治疗中,DST/CT可用于了解一个人的心理和情绪状态在治疗过程中如何变化,包括更高的复杂性。本研究旨在系统回顾DST/CT方法在心理治疗研究中的变异性。
    在EBSCO和WebofKnowledge数据库中进行了初步研究搜索,提取有关分析的DST/CT现象的信息,采用数学方法来研究这些现象,指定动态模型的描述,心理治疗现象,以及其他有关具有经验数据的研究的信息(例如,测量粒度)。
    在筛选了38,216篇摘要和4,194篇全文后,确定了1990年至2021年发表的N=41项研究。所采用的方法通常包括动态复杂性或混沌性的度量。计算和模拟研究通常采用一阶常微分方程,通常侧重于描述客户-治疗师二元影响的时间演变。具有经验数据的合格研究通常基于案例研究,并专注于会议内动态的高时间强度数据。
    这篇综述提供了心理疗法研究领域中DST/CT方法增殖的现状的描述性综合。
    UNASSIGNED: Dynamic systems theory and complexity theory (DST/CT) is a framework explaining how complex systems change and adapt over time. In psychotherapy, DST/CT can be used to understand how a person\'s mental and emotional state changes during therapy incorporating higher levels of complexity. This study aimed to systematically review the variability of DST/CT methods applied in psychotherapy research.
    UNASSIGNED: A primary studies search was conducted in the EBSCO and Web of Knowledge databases, extracting information about the analyzed DST/CT phenomena, employed mathematical methods to investigate these phenomena, descriptions of specified dynamic models, psychotherapy phenomena, and other information regarding studies with empirical data (e.g., measurement granularity).
    UNASSIGNED: After screening 38,216 abstracts and 4,194 full texts, N = 41 studies published from 1990 to 2021 were identified. The employed methods typically included measures of dynamic complexity or chaoticity. Computational and simulation studies most often employed first-order ordinary differential equations and typically focused on describing the time evolution of client-therapist dyadic influences. Eligible studies with empirical data were usually based on case studies and focused on data with high time intensity of within-session dynamics.
    UNASSIGNED: This review provides a descriptive synthesis of the current state of the proliferation of DST/CT methods in the psychotherapy research field.
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  • 文章类型: Journal Article
    教育质量是联合国2030年可持续发展议程中的17个目标之一,前提是对学习进行仔细的规划和评估。体育教育中的传统计划(无论是在培训还是在学校环境中)主要采用预先确定的学习顺序和时间里程碑,理论上,加强学习过程。然而,学习是一个依赖于上下文的过程,具有相当大的个体内部和个体间变异性的非线性过程,因此,规划和评估也应该是非线性的。在这篇叙述性评论中,主要研究结果表明,具体的教学或培训内容及其相对(即排序或排序)和绝对定时(即,预期某些学习或适应的特定时间点)应根据学习者和上下文而有所不同。从面向过程的角度来看,这需要灵活的规划,并在规划和评估之间建立持续的双向联系。在这个框架中,评估应该是灵活的,不断发展,和日常教学工具,而不是一套正式的检查站。我们进一步探讨了如何将计划和评估联系起来,以提供一个持续的反馈循环,尊重每个学习者的个性及其背景,因此,希望这项审查有助于改变当前体育教育的规划和评估范式。
    Quality in education is one of the 17 goals in the United Nations\' sustainable agenda for 2030, presupposing careful planning and assessment of learning. Traditional planning in sports education (either in training or school settings) largely adopts pre-determined learning sequences and temporal milestones that, in theory, enhance the learning process. However, learning is a context-dependent, non-linear process with considerable intra- and interindividual variability, whereby planning and assessment should also be non-linear. In this narrative review, the main findings suggest that the specific teaching or training contents and their relative (i.e., ordering or sequencing) and absolute timing (i.e., the specific time point where certain learning or adaptations are expected) should vary depending on the learners and the context. In a process-oriented perspective, this requires flexible planning and the establishment of ongoing bidirectional links between planning and assessment. In this framework, assessment should be a flexible, evolving, and daily pedagogical tool instead of a set of formal checkpoints. We further explored how planning and assessment could be linked to provide an ongoing feedback loop that respects the individuality of each learner and its context, and therefore hope this review helps bring about a change in current planning and assessment paradigms in sports education.
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  • 文章类型: Journal Article
    时间不可逆性的评估,即,在时间反转操作下,系统的统计特性缺乏不变性,是一个在研究界稳步获得关注的话题。在许多现实世界的系统中已经发现了不可逆的动力学,与改变有关,例如,人脑的病理,心脏和步态,或金融市场效率低下。评估时间序列的不可逆性并非易事,由于它的许多病因和它在数据中表现的不同方式。因此,在过去的几十年中提出了几种数值方法并不奇怪,基于不同的原则和不同的应用。在本文中,我们回顾了为测试时间序列的不可逆性而提出的最重要的算法解决方案,他们潜在的假设,计算和实际限制,和他们的比较表现。我们还提供了一个开源软件库,其中包括这里考虑的所有测试。作为最后一点,我们表明\“一个尺寸不适合所有\”,由于测试结果是互补的,有时对问题的观点相互矛盾;并讨论一些未来的研究途径。
    The assessment of time irreversibility, i.e., of the lack of invariance of the statistical properties of a system under the operation of time reversal, is a topic steadily gaining attention within the research community. Irreversible dynamics have been found in many real-world systems, with alterations being connected to, for instance, pathologies in the human brain, heart and gait, or to inefficiencies in financial markets. Assessing irreversibility in time series is not an easy task, due to its many aetiologies and to the different ways it manifests in data. It is thus not surprising that several numerical methods have been proposed in the last decades, based on different principles and with different applications in mind. In this contribution we review the most important algorithmic solutions that have been proposed to test the irreversibility of time series, their underlying hypotheses, computational and practical limitations, and their comparative performance. We further provide an open-source software library that includes all tests here considered. As a final point, we show that \"one size does not fit all\", as tests yield complementary, and sometimes conflicting views to the problem; and discuss some future research avenues.
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  • 文章类型: Journal Article
    Lake water-level fluctuation is a complex and dynamic process, characterized by high stochasticity and nonlinearity, and difficult to model and forecast. In recent years, applications of machine learning (ML) models have yielded substantial progress in forecasting lake water-level fluctuations. This paper presents a comprehensive review of the applications of ML models for modeling water-level dynamics in lakes. Among the many existing ML models, seven popular ML model types are reviewed: (1) artificial neural network (ANN); (2) support vector machine (SVM); (3) artificial neuro-fuzzy inference system (ANFIS); (4) hybrid models, such as hybrid wavelet-artificial neural network (WA-ANN) model, hybrid wavelet-artificial neuro-fuzzy inference system (WA-ANFIS) model, and hybrid wavelet-support vector machine (WA-SVM) model; (5) evolutionary models, such as gene expression programming (GEP) and genetic programming (GP); (6) extreme learning machine (ELM); and (7) deep learning (DL). Model inputs, data split, model performance criteria, and model inter-comparison as well as the associated issues are discussed. The advantages and limitations of the established ML models are also discussed. Some specific directions for future research are also offered. This review provides a new vision for hydrologists and water resources planners for sustainable management of lakes.
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  • 文章类型: Journal Article
    The relationship between BMI and mortality has been extensively investigated in the general population; however, it is less clear in people with type 2 diabetes. We aimed to assess the association of BMI with all-cause and cardiovascular mortality in individuals with type 2 diabetes mellitus.
    We searched electronic databases up to 1 March 2016 for prospective studies reporting associations for three or more BMI groups with all-cause and cardiovascular mortality in individuals with type 2 diabetes mellitus. Study-specific associations between BMI and the most-adjusted RR were estimated using restricted cubic splines and a generalised least squares method before pooling study estimates with a multivariate random-effects meta-analysis.
    We included 21 studies including 24 cohorts, 414,587 participants, 61,889 all-cause and 4470 cardiovascular incident deaths; follow-up ranged from 2.7 to 15.9 years. There was a strong nonlinear relationship between BMI and all-cause mortality in both men and women, with the lowest estimated risk from 31-35 kg/m2 and 28-31 kg/m2 (p value for nonlinearity <0.001) respectively. The risk of mortality at higher BMI values increased significantly only in women, whilst lower values were associated with higher mortality in both sexes. Limited data for cardiovascular mortality were available, with a possible inverse linear association with BMI (higher risk for BMI <27 kg/m2).
    In type 2 diabetes, BMI is nonlinearly associated with all-cause mortality with lowest risk in the overweight group in both men and women. Further research is needed to clarify the relationship with cardiovascular mortality and assess causality and sex differences.
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