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Energy cascades in the upper ocean

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Chinese Journal of Oceanology and Limnology 2006年第3期24卷 225-235页

作者： Ray q.lin Scott Chubb Hydromechanics Directorate David Taylor Research Center Carderock Division West Bethesda MD 20817-5700 USA Remote Sensing Division Naval Research Laboratory Washington DC 20375-5351 USA

Wave-wave interactions cause energy cascades. These are the most important processes in the upper ocean because they govern wave-growth and dissipation. Through indirect cascades, wave en- ergy is transferred from higher frequencies to lower frequencies, leading to wave growth. In direct cas- cades, energy is transferred from lower frequencies to the higher frequencies, which causes waves to break, and dissipation of wave energy. However, the evolution and origin of energy cascade processes are still not fully understood. In particular, for example, results from a recent theory (Kalmykov, 1998) sug- gest that the class I wave-wave interactions (defined by situations involving 4-, 6-, 8-, etc, even numbers of resonantly interacting waves) cause indirect cascades, and Class II wave-wave interactions (involving, 5-, 7-, 9-, etc, .., odd numbers of waves) cause direct cascades. In contrast to this theory, our model results indicate the 4-wave interactions can cause significant transfer of wave energy through both direct and in- direct cascades. In most situations, 4-wave interactions provide the major source of energy transfer for both direct cascades and indirect cascades, except when the wave steepness is larger than 0.28. Our model results agree well with wave measurements, obtained using field buoy data (for example, lin and lin, 2002). In particular, in these observations, asymmetrical wave-wave interactions were studied. They found that direct and indirect cascades both are mainly due to the 4-wave interactions when wave steep- ness is less than 0.3.

关键词： upper ocean processes nonlinear dynamics modeling

THERMODYNAMIC PARAMETERS IN THE NUCLEATION OF LIqUID IRON

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Acta Metallurgica Sinica(English Letters) 2003年第6期16卷 519-523页

作者： C.Huang B.Song J.H.Mao q.lin P.Zhao UniversityofScienceandTechnologyBeijing Beijing100083China CentralIronandSteelResearchInstitute Beijing100081China

By using of electrolytic pure iron, the specimens containing different oxide content were made in a Mo wire furnace. The DTA method was employed to measure the undercooling of liquid iron during solidification. The relations between the cleanness of liquid iron and undercooling, thermodynamic driving force of nucleation, the nucleus forming energy, as well as the critical radius of nucleus have been investigated. The results showed that with the increase of cleanness of liquid iron the undercooling and thermodynamic driving force increased, while the nucleus forming energy and critical radius of nucleus decreased.

关键词： pure iron cleanness undercooling thermodynamic parameter

Estimating Transient Stability Regions of Large-scale Power Systems Part Ⅱ: Reduced-order Stability Region with Computational Efficiency

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CSEE Journal of Power and Energy Systems 2025年第1期11卷 38-50页

作者： Yuqing lin Tianhao Wen Lei Chen Yang Liu q. H. Wu School of Electric Power Engineering South China University of TechnologyGuangzhou510640China

Part Ⅱ of this paper presents a reduced-order stability region (ROSR) based method to estimate the full-order stability region (FOSR) of a large-scale power system. First, we introduce the definitions of FOSR and ROSR, followed by a comprehensive theory that reveals the relationships between them. Since the full-order system can be rewritten as a standard two timescale model and the reduced-order system is regarded as the slow subsystem of it, the proposed theory is derived based on the idea of singular perturbation. With rigorous mathematical proof, the properties of FOSR and ROSR are revealed. Moreover, a modified Energy Augmented Dynamic (EAD) algorithm and a constrained equidistant projection (CEP) approach are employed to estimate the ROSR and FOSR, respectively. The modified EAD algorithm and CEP form a so-called reduced-order stability region mapping (ROSRM) method. Finally, the proposed ROSRM method is applied to the IEEE 10-machine-39-bus power system, and simulation studies confirm its superiority to the traditional energy function method in terms of computational speed and reliability of results.

关键词： Large-scale power system singular perturbation theory stability region sum of squares transient stability

Estimating Transient Stability Regions of Large-Scale Power Systems Part I: Koopman Operator and Reduced-Order Model

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CSEE Journal of Power and Energy Systems 2025年第1期11卷 24-37页

作者： Yuqing lin Tianhao Wen Lei Chen q. H. Wu Yang Liu School of Electric Power Engineering South China University of Technology Guangzhou China

This paper presents an estimation of transient stability regions for large-scale power systems. In Part I, a Koopman operator based model reduction (KOMR) method is proposed to derive a low-order dynamical model with reasonable accuracy for transient stability analysis of large-scale power systems. Unlike traditional reduction methods based on linearized models, the proposed method does not require linearization, but captures dominant modes of the original nonlinear dynamics by employing a Koopman operator defined in an infinite-dimensional observable space. Combined with the Galerkin projection, the obtained dominant Koopman eigenvalues and modes produce a reduced-order nonlinear model. To approximate the Koopman operator with sufficient accuracy, we introduce a Polynomial-based Multi-trajectory Kernel Dynamic Mode Decomposition (PMK-DMD) algorithm, which outperforms traditional DMD in various scenarios. In the end, the proposed method is applied to the IEEE 10-machine-39-bus power system and IEEE 16-machine-68-bus power system, which demonstrates that our method is significantly superior to the modal analysis method in both qualitative and quantitative aspects.

关键词： Power system stability Reduced order systems Nonlinear dynamical systems Eigenvalues and eigenfunctions Power system dynamics Kernel Transient analysis Analytical models Accuracy Modal analysis

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增强CT影像组学模型预测急性胰腺炎复发

国际医学放射学杂志 2019年第5期 631-631页

作者： Y.Chen T.Chen C.Wu q.lin R.Hu C.Xie 张泽伟 Sichuan Key Laboratory of Medical Imaging and Department of Radiology Affiliated Hospital of North Sichuan Medical College

摘要目的通过构建急性胰腺炎(AP)首次发作时增强CT(CECT)影像组学模型来预测AP复发。方法本研究回顾性纳入了来自3个三级转诊中心共389例AP首次发作的病

关键词：急性胰腺炎影像组学 CT 模型预测

68Ga-FAPI和18F-FDG在胃、十二指肠和结直肠癌摄取的比较研究

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国际医学放射学杂志 2021年第2期44卷 235-235页

作者： Y.Z.Pang L.Zhao Z.M.Luo B.Hao H.Wu q.lin 盛洁

摘要准确的临床分期对治疗胃肠道肿瘤至关重要,但F-FDG PET/CT对此尚存在局限性。靶向成纤维细胞激活蛋白是一种较新的肿瘤基质可视化诊断方法,而Ga标记的成

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Channel pruning on frequency response

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Science China(Information Sciences) 2025年第1期68卷 159-170页

作者： Hang lin Yifan PENG lin BIE Chenggang YAN Xibin ZHAO Yue GAO School of Software Tsinghua University School of Automation Hangzhou Dianzi University

Network pruning has a significant role in reducing network parameters and accelerating the inference time of the network. Some existing methods prune the network based on the frequency of the data, and finally obtain a sub-network with high accuracy. However, according to our experimental analysis, different frequencies of information in the data contribute differently to the accuracy of the model, and using this information directly for pruning without making a selection will lead to incorrect results. We believe that pruning should retain the convolutional kernels in the network that process important information, while those kernels that process unimportant information should be removed. In this paper, we first investigate the meaning of each frequency band information in the spectrum and their contribution to the prediction accuracy of the network,and according to these results, we propose a new pruning method based on frequency response(PFR). Our PFR finds and removes the convolutional kernels in the network that specialize in processing unimportant information, resulting in a compact neural network model. PFR obtains significant experimental results on different datasets, for example, a 56.0% raduction of float points operations(FLOPs) on Res Net-50 and only 0.37% of Top-1 accuracy degradation on the Image Net dataset.

关键词： deep learning model compression filter pruning channel pruning frequency response

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New progresses of fine-grained sediment gravity-flow deposits and their importance for unconventional shale oil and gas plays

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Petroleum Science 2025年第1期22卷 1-15页

作者： Tian Yang Ying-lin Liu State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Chengdu University of Technology) Institute of Sedimentary Geology Key Laboratory of Deep-time Geography and Environment Reconstruction and Applications of Ministry of Natural Resources Chengdu University of Technology

Fine-grained sediments are widely distributed and constitute the most abundant component in sedimentary systems, thus the research on their genesis and distribution is of great significance. In recent years, fine-grained sediment gravity-flows(FGSGF) have been recognized as an important transportation and depositional mechanism for accumulating thick successions of fine-grained sediments. Through a comprehensive review and synthesis of global research on FGSGF deposition, the characteristics,depositional mechanisms, and distribution patterns of fine-grained sediment gravity-flow deposits(FGSGFD) are discussed, and future research prospects are clarified. In addition to the traditionally recognized low-density turbidity current and muddy debris flow, wave-enhanced gravity flow, lowdensity muddy hyperpycnal flow, and hypopycnal plumes can all form widely distributed FGSGFD. At the same time, the evolution of FGSGF during transportation can result in transitional and hybrid gravityflow deposits. The combination of multiple triggering mechanisms promotes the widespread development of FGSGFD, without temporal and spatial limitations. Different types and concentrations of clay minerals, organic matters, and organo-clay complexes are the keys to controlling the flow transformation of FGSGF from low-concentration turbidity currents to high-concentration muddy debris flows. Further study is needed on the interaction mechanism of FGSGF caused by different initiations, the evolution of FGSGF with the effect of organic-inorganic synergy, and the controlling factors of the distribution patterns of FGSGFD. The study of FGSGFD can shed some new light on the formation of widely developed thin-bedded siltstones within shales. At the same time, these insights may broaden the exploration scope of shale oil and gas, which have important geological significances for unconventional shale oil and gas.

关键词： Fine-grained sediment gravity-flow Depositional mechanism Transportation and evolution Distribution pattern Shale oil and gas

Upper Bounds on the Multicolor Ramsey Numbers r_(k)(C_(4))

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Acta Mathematicae Applicatae Sinica 2025年第1期41卷 286-294页

作者： Tian-yu LI qi-zhong lin Center for Discrete Mathematics Fuzhou UniversityFuzhou 350108China

The multicolor Ramsey number r_(k)(C_(4))is the smallest integer N such that any k-edge coloring of KN contains a monochromatic C_(4).The current best upper bound of r_(k)(C_(4))was obtained by Chung(1974)and independently by Irving(1974),i.e.,r_(k)(C_(4))≤k^(2)+k+1 for all k≥*** is no progress on the upper bound since *** this paper,we improve the upper bound of r_(k)(C_(4))by showing that r_(k)(C_(4))≤k^(2)+k-1 for even k≥*** improvement is based on the upper bound of the Turan number ex(n,C4),in which we mainly use the double counting method and many novel ideas from Firke,Kosek,Nash,and Williford[***,Ser.B 103(2013),327-336].

关键词： Multicolor Ramsey number Turan number 4-cycle