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Dynamic Stability Analysis of Linear Time-varying Systems via an Extended Modal Identification Approach

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Chinese Journal of Mechanical Engineering 2017年第2期30卷 459-471页

作者： Zhisai MA Li LIU Sida ZHOU Frank NAETS Ward HEYLEN Wim desmet School of Aerospace Engineering Beijing Institute of Technology Department of Mechanical Engineering KU Leuven

The problem of linear time-varying（LTV） system modal analysis is considered based on time-dependent state space representations, as classical modal analysis of linear time-invariant systems and current LTV system modal analysis under the ＂frozen-time＂ assumption are not able to determine the dynamic stability of LTV systems. Time-dependent state space representations of LTV systems are first introduced, and the corresponding modal analysis theories are subsequently presented via a stabilitypreserving state transformation. The time-varying modes of LTV systems are extended in terms of uniqueness, and are further interpreted to determine the system＇s stability. An extended modal identification is proposed to estimate the time-varying modes, consisting of the estimation of the state transition matrix via a subspace-based method and the extraction of the time-varying modes by the QR decomposition. The proposed approach is numerically validated by three numerical cases, and is experimentally validated by a coupled moving-mass simply supported beam exper- imental case. The proposed approach is capable of accurately estimating the time-varying modes, and provides anew way to determine the dynamic stability of LTV systems by using the estimated time-varying modes.

关键词： Linear time·varying systems · Extended modal identification · Dynamic stability analysis · Time·varying modes

Exploring the light-quark interaction

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Chinese Physics C 2009年第12期33卷 1189-1196页

作者：常雷 Ian C. cloЁT Bruno El-BENNICH Thomas KLHN Craig D. ROBERTS Institute of Applied Physics and Computational Mathematics Department of Physics University of Washington Seattle WA 98195 USA Physics Division Argonne National Laboratory Argonne Illinois 60439 USA Department of Physics Peking University

Two basic motivations for an upgraded JLab facility are the needs： to determine the essential nature of light-quark confinement and dynamical chiral symmetry breaking （DCSB）; and to understand nucleon structure and spectroscopy in terms of QCD＇s elementary degrees of freedom. During the next ten years a programme of experiment and theory will be conducted that can address these questions. We present a Dyson- Schwinger equation perspective on this effort with numerous illustrations, amongst them： an interpretation of string^breaking; a symmetry-preserving truncation for mesons; the nucleon＇s strangeness σ-term; and the neutron＇s charge distribution.

关键词： Bethe-Salpeter equations bound-states confinement dynamical chiral symmetry breaking,Dyson-Schwinger equations Faddeev equation nucleon electromagnetic form factors

Magnetic resonance imaging may predict deep remission in patients with perianal fistulizing Crohn's disease

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World Journal of Gastroenterology 2017年第23期23卷 4285-4292页

作者： Lucie Thomassin Laura Armengol-Debeir cloé Charpentier Valerie Bridoux Edith Koning Guillaume Savoye Céline Savoye-Collet Department of Gastroenterology Rouen University HospitalUniversity of Rouen Department of Radiology Rouen University HospitalUniversity of Rouen Department of Digestive Surgery Rouen University HospitalUniversity of Rouen

To evaluate the imaging course of Crohn’s disease (CD) patients with perianal fistulas on long-term maintenance anti-tumor necrosis factor (TNF)-α therapy and identify predictors of deep *** patients with perianal CD treated with anti-TNF-α therapy at our tertiary care center were evaluated by magnetic resonance imaging (MRI) and clinical assessment. Two MR examinations were performed: at initiation of anti-TNF-α treatment and then at least 2 years after. Clinical assessment (remission, response and non-response) was based on Present’s criteria. Rectoscopic patterns, MRI Van Assche score, and MRI fistula activity signs (T2 signal and contrast enhancement) were collected for the two MR examinations. Fistula healing was defined as the absence of T2 hyperintensity and contrast enhancement on MRI. Deep remission was defined as the association of both clinical remission, absence of anal canal ulcers and healing on MRI. Characteristics and imaging patterns of patients with and without deep remission were compared by univariate and multivariate ***-nine consecutive patients (31 females and 18 males) were included. They ranged in age from 14-70 years (mean, 33 years). MRI and clinical assessment were performed after a mean period of exposure to anti-TNF-α therapy of 40 ± 3.7 mo. Clinical remission, response and non-response were observed in 53.1%, 20.4%, and 26.5% of patients, respectively. Deep remission was observed in 32.7% of patients. Among the 26 patients in clinical remission, 10 had persisting inflammation of fistulas on MRI (T2 hyperintensity, n = 7; contrast enhancement, n = 10). Univariate analysis showed that deep remission was associated with the absence of rectal involvement and the absence of switch of anti-TNF-α treatment or surgery requirement. Multivariate analysis demonstrated that only the absence of rectal involvement (OR = 4.6; 95%CI: 1.03-20.5) was associated with deep *** remission is achieved i

关键词： Crohn’s disease Anal fistula Magnetic resonance imaging Anus disease/diagnosis Biotherapy

RMA-CNN:A Residual Mixed Domain Attention CNN for Bearings Fault Diagnosis and Its Time-Frequency Domain Interpretability

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Journal of Dynamics, Monitoring and Diagnostics 2023年第2期2卷 115-132页

作者： Dandan Peng Huan Wang Wim desmet Konstantinos Gryllias Department of Mechanical Engineering Faculty of Engineering ScienceKU LeuvenLeuvenBelgium Flanders Make@KU Leuven Celestijnenlaan 300BOX 24203001 LeuvenBelgium Department of Industrial Engineering Tsinghua UniversityBeijing 100084China Leuven.AI–KU Leuven Institute for AI B-3000LeuvenBelgium

Early fault diagnosis of bearings is crucial for ensuring safe and reliable *** neural networks(CNNs)have achieved significant breakthroughs in machinery fault ***,complex and varying working conditions can lead to inter-class similarity and intra-class variability in datasets,making it more challenging for CNNs to learn discriminative ***,CNNs are often considered“black boxes”and lack sufficient interpretability in the fault diagnosis *** address these issues,this paper introduces a residual mixed domain attention CNN method,referred to as *** method comprises multiple residual mixed domain attention modules(RMAMs),each employing one attention mechanism to emphasize meaningful features in both time and channel *** significantly enhances the network’s ability to learn fault-related ***,we conduct an in-depth analysis of the inherent feature learning mechanism of the attention module RMAM to improve the interpretability of CNNs in fault diagnosis *** conducted on two datasets—a high-speed aeronautical bearing dataset and a motor bearing dataset—demonstrate that the RMA-CNN achieves remarkable results in diagnostic tasks.

关键词： attention interpretability CNN fault diagnosis rolling element bearings

Kinetic performance comparison of fully and superfcially porous particles with sizes ranging between 2.7 lm and 5 lm: Intrinsic evaluation and application to a pharmaceutical test compound

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Journal of Pharmaceutical Analysis 2013年第5期3卷 313-323页

作者： K.Broeckhoven D.Cabooter G.desmet Vrije Universiteit Brussel Department of Chemical Engineering KU Leuven Department of Pharmaceutical Sciences

The reintroduction of superficially porous particles has resulted in a leap forward for the separation performance in liquid chromatography. The underlying reasons for the higher efficiency of columns packed with these particles are discussed. The performance of the newly introduced 5 p.m superficially porous particles is evaluated and compared to 2.7 pm superficially porous and 3.5 and 5 p.m fully porous columns using typical test compounds （alkylphenones） and a relevant pharmaceutical compound （impurity of amoxicillin）. The 5 *** superficially porous particles provide a superior kinetic performance compared to both the 3.5 and 5 Ixm fully porous particles over the entire relevant range of separation conditions. The performance of the superficially porous particles, however, appears to depend strongly on retention and analyte properties, emphasizing the importance of comparing different columns under realistic conditions （high enough k） and using the compound of interest.

关键词： Kinetic plot Superfcially porous particles 5 μm Permeability Amoxicillin impurity Alkylphenones

Impact of the Future Changing Climate on the Southern Africa Biomes, and the Importance of Geology

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Journal of Geoscience and Environment Protection 2017年第7期5卷 1-9页

作者： Danni Guo Philip G. desmet Leslie W. Powrie South African National Biodiversity Institute Kirstenbosch Research Center Cape Town Republic of South Africa Department of Zoology Nelson Mandela Metropolitan University Port Elizabeth Republic of South Africa

The Southern African biomes are complex biotic communities, with its distinctive plant and animal species, and are maintained under the suitable climatic conditions of the region. It includes the Fynbos Biome and the Succulent Karoo Biome, which forms the smallest of the world’s six Floristic Kingdoms, and they are of conservation concern. The other six biomes are Albany Thicket, Desert, Grassland, Indian Ocean Coastal belt, Nama-Karoo, Savanna. The biomes are not only threatened by agricultural expansion, overgrazing, and mining;but also by future climate changes and droughts. This study investigates the how to best model the possible vulnerable biome areas, under future climate changes, and how Southern African geology plays a huge role in the restriction of the biome shifts. It provides evidence regarding the importance of the study to understanding the climate change impacts and the geological variables on the Southern African biomes, in terms of possible future biome habitat loss.

关键词： Climate Change Biomes Geology Southern Africa Albany Thicket Desert Fynbos Grassland Indian Ocean Coastal Belt Nama-Karoo Savanna Succulent Karoo

Fabrication of patterned graphitized carbon wires using low voltage near-field electrospinning, pyrolysis, electrodeposition, and chemical vapor deposition

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Microsystems & Nanoengineering 2020年第1期6卷 1341-1352页

作者： Derosh George Adrian Garcia Quang Pham Mario Ramos Perez Jufeng Deng Michelle Trang Nguyen Tuo Zhou Sergio OMartinez-Chapa Yoonjin Won Chong Liu Roger clo Regina Ragan Marc Madou Mechanical and Aerospace Engineering University of CaliforniaIrvineUSA Chemical Engineering and Materials Science University of CaliforniaIrvineUSA Materials and Manufacturing Technology University of CaliforniaIrvineUSA School of Engineering and Sciences Tecnologico de MonterreyMonterreyMexico Mechanical Engineering Dalian University of TechnologyDalianChina Chemical Engineering California State UniversityLong BeachUSA Present address:Mechanical Engineering Centro de Ensenanza Tecnica y Superior UniversidadMexicaliMexico

We herein report a high-resolution nanopatterning method using low voltage electromechanical spinning with a rotating collector to obtain aligned graphitized micro and nanowires for carbon nanomanufacturing.A small wire diameter and a small inter-wire spacing were obtained by controlling the electric field,the spinneret-to-collector distance,the pyrolysis parameters,the linear speed of the spinneret,the rotational speed of the *** a simple scaling analysis,we show how the straightness and the diameter of the wires can be controlled by the electric field and the distance of the spinneret to the collector.A small inter-wire spacing,as predicted by a simple model,was achieved by simultaneously controlling the linear speed of the spinneret and the rotational speed of the *** drying of the polymer nanowires enabled the facile fabrication of suspended wires over various *** polyacrylonitrile wires were carbonized using standard stabilization and pyrolysis to obtain carbon *** carbon nanowires with a diameter of<50 nm were *** also established a method for making patterned,highly graphitized structures by using the aforementioned carbon wire structures as a template for chemical vapor deposition of *** patterning technique offers high throughput for nano writing,which outperforms other existing nanopatterning techniques,making it a potential candidate for large-scale carbon nanomanufacturing.

关键词： nanowires carbon field

Climate Change Impacts on Dwarf Succulents in Namibia as a Result of Changes in Fog and Relative Humidity

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Climate Change Impacts on Dwarf Succulents in Namibia as a R...

作者： Danni Guo Andrew J.Young Philip G.desmet Guy F.Midgley South African National Biodiversity Institute School of Natural Sciences and Psychology Liverpool John Moores University Department of Zoology Nelson Mandela Metropolitan University Department of Botany and Zoology Stellenbosch University

The Succulent Karoo is well known for being rich in species with approximately 5,000 vascular plant species,and has a high floral *** this study,we investigate the current status of the dwarf succulents of Namibia,as represented by two genera in the Aizoaceae: Conophytum(restricted distribution) and Lithops(wider distribution) and examine possible climate change impacts on these genera by studying the effects on non-rainfall moisture availability(number fog days and relative humidity).Both genera show a contraction and loss of habitat,despite their drought resistant nature and adaptation to the current arid *** study demonstrates that climate-change induced alterations to the number of fog days in Namibia results insignificant changes in the distribution of the dwarf succulents,and shows the Atlantic coast and Orange River areas as potential refuge areas for dwarf succulents such as Conophytum and Lithops.

关键词： Climate Change Conophytum Lithops Dwarf Succulents Fog Relative Humidity Succulent Karoo Namibia

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商学院 2010年第12期 70-72页

作者： Aaron desmet Monica McGurk Elizabeth Schwartz

Jarod在一家大型零售企业负责培训工作。“我们企业拥有好几家大型卖场，两年多以来，我们一直想通过对员工的培训来提高客户的关注度，但是收效却微乎其微。”JarodB的企业投资数百万，向员工传授一种五步销售流程，监测客户的反馈，... 详细信息

Jarod在一家大型零售企业负责培训工作。“我们企业拥有好几家大型卖场，两年多以来，我们一直想通过对员工的培训来提高客户的关注度，但是收效却微乎其微。”JarodB的企业投资数百万，向员工传授一种五步销售流程，监测客户的反馈，并推出了电子学习计划，以提高其员工对所销售产品的知识。“销售人员通过了每种规定的认证考试，但仍然无法在销售现场使用学到的新技能，客户反馈和商店业绩依然不见起色。”

关键词：培训收益企业负责销售流程大型卖场企业投资学习计划销售产品