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Anisotropic plastic deformation behavior of as-extruded ZK60 magnesium alloy at room temperature

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Science China(Technological Sciences) 2009年第1期52卷 161-165页

作者： hans J R Department of Materials Science and Engineering Norwegian University of Science and Technology

The anisotropic plastic deformation behavior of as-extruded ZK60 magnesium alloy at room tempera-ture (RT) was investigated by compressive and tensile testing in different directions, i.e. the loading axis oriented at 0°, 45° and 90° to the extrusion direction. The relationship between texture and plastic deformation behavior were examined. The results show that the extruded ZK60 alloy exhibits a strong ring fiber texture. The mechanical properties are strongly orientation dependent. In tension testing, the 0° specimen exhibited higher yield strength and lower elongation. In compression testing, however, ZK60 alloy exhibited almost the same yield strength in three directions. The anisotropic plastic defor-mation behavior is due to strong fiber texture and the lower symmetry of the hexagonal close packed (hcp) structure of ZK60 alloy. The correlation between texture and mechanical behaviour offers the possibility to improve the mechanical properties of magnesium alloy by optimization of the material production process.

关键词： anisotropic plastic deformation behavior ZK60 Mg alloy texture mechanical property

Robust Control of a Bevel-Tip Needle for Medical Interventional Procedures

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IEEE/CAA Journal of Automatica Sinica 2020年第1期7卷 244-256页

作者： Surender hans Felix Orlando Maria Joseph Department of Electrical Engineering Indian Institute of Technology RoorkeeRoorkeeUttarakhand 247667India

In minimally invasive surgery, one of the main objectives is to ensure safety and target reaching accuracy during needle steering inside the target organ. In this research work, the needle steering approach is determined using a robust control algorithm namely the integral sliding mode control(ISMC) strategy to eliminate the chattering problem associated with the general clinical scenario. In general, the discontinuity component of feedback control input is not appropriate for the needle steering methodology due to the practical limitations of the driving actuators. Thus in ISMC, we have incorporated the replacement of the discontinuous component using a super twisting control(STC)input due to its unique features of chattering elimination and disturbance observation characteristics. In our study, the kinematic model of an asymmetric flexible bevel-tip needle in a soft-tissue phantom is used to evaluate stability analysis. A comparative study based on the analysis of chattering elimination is executed to determine the performance of the proposed control strategy in real-time needle steering with conventional sliding mode control using vision feedback through simulation and experimental results. This validates the efficacy of the proposed control strategy for clinical needle steering.

关键词： Minimal invasive surgery needle steering nonholonomic system robust control sliding mode control

A comprehensive benchmark dataset for the validation of building component heat,air,and moisture(HAM)models

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Building Simulation 2024年第11期17卷 1893-1907页

作者： Xinyuan Dang hans Janssen Staf Roels KU Leuven Department of Civil EngineeringLeuven 3001Belgium

Numerical heat,air and moisture(HAM)modeling allows predicting hygrothermal responses of building components with higher efficiency and less effort than laboratory experiments and field ***,inaccuracy and/or incorrectness may appear in the predictions for the same case through different HAM models,primarily due to limitations or deviations in the description of physical phenomena and/or the implementation of mathematical *** preferences,biases,and/or mistakes with respect to implementing material properties,boundary conditions and other factors may also yield *** a correct implementation of the numerical models is typically verified by the developers,the validity of the HAM models may remain questionable without the confrontation with experimental ***,well-determined criteria and well-documented datasets for establishing the correct prediction of the transient hygrothermal responses of building components by HAM models remain very *** address this issue,a dedicated benchmark experiment was conducted in the hot box-cold box(HB-CB)setup at KU Leuven,Belgium,on four wall assemblies composed of calcium silicate board,mineral wool,wood fiber board,and vapour barrier in different ***,relative humidity,heat fluxes and moisture masses,as hygrothermal responses,were monitored under quasi-steady state boundary ***-scale characterization of the materials from the same batch was performed,along with a determination of the surface transport coefficients within the HB-CB *** comprehensive dataset allows a proper model validation by incorporating experimental datasets of material properties and surface transport coefficients and by confronting simulated hygrothermal responses with experimental *** addition,sensitivity analysis can be performed to obtain insights into the impact of uncertainties in characterizing material properties on hygrothermal simulation predictions.

关键词： heat,air,and moisture(HAM) hygrothermal response dataset model simulation validation

Micromechanical investigation of granular ratcheting using a discrete model of polygonal particles

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Particuology 2008年第6期6卷 390-403页

作者： Fernando Alonso-Marroquín hans B. Mhlhaus hans J. Herrmann Earth Systems Science Computational Centre & School of Physical Sciences The University of Queensland Earth Systems Science Computational Centre The University of Queensland Institut fr Baustoffe ETH-HenggerbergZrich

We use a two-dimensional model of polygonal particles to investigate granular ratcheting. Ratcheting is a long-term response of granular materials under cyclic loading, where the same amount of permanent deformation is accumulated after each cycle. We report on ratcheting for low frequencies and extremely small loading amplitudes. The evolution of the sub-network of sliding contacts allows us to understand the micromechanics of ratcheting. We show that the contact network evolves almost periodically under cyclic loading as the sub-network of the sliding contacts reaches different stages of anisotropy in each cycle. Sliding contacts lead to a monotonic accumulation of permanent deformation per cycle in each particle. The distribution of these deformations appears to be correlated in form of vortices inside the granular assembly.

关键词： Granular systems Dynamics and kinematics of rigid bodies Molecular dynamics methods

Suppression of mature TAU isoforms prevents Alzheimer's disease-like amyloid-beta oligomer-induced spine loss in rodent neurons

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Neural Regeneration Research 2024年第8期19卷 1655-1657页

作者： Sarah Buchholz hans Zempel Institute of Human Genetics Faculty of Medicine and University Hospital CologneUniversity of CologneCologneGermany Center for Molecular Medicine Cologne(CMMC) Faculty of Medicine and University Hospital CologneUniversity of CologneCologneGermany

Introduction:TAU isoforms as disease mediators:The microtubule-associated protein TAU is predominantly present in the axons of neurons under physiological *** Alzheimer’s disease(AD)and related tauopathies,TAU also mislocalizes("TAU missorting")to the soma and the dendrites,where it eventually forms aggregates,the so-called neurofibrillary tangles(for review see Zimmer-Bensch and Zempel,2021;Zempel,2023).

关键词： Alzheimer Zimmer tau

High-resolution Induan-Olenekian boundary sequence in Chaohu, Anhui Province

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Science China Earth Sciences 2005年第3期48卷 291-297页

作者： hans J. hansen Geological Institute Copenhagen University Oster Voldgade 10 DK-1350 Copenhage Denmark

The West Pingdingshan Section in Chaohu, Southeast China’s Anhui Province is one of the potential GSSP candidates for the Induan-Olenekian boundary. Extensive study has been done on the Induan-Olenekian boundary strata at the section to meet the requirements of defining the GSSP precisely. This paper focuses on the boundary strata at the section to present a review of the main results achieved in recent years. The Induan-Olenekian boundary strata here cover an interval of about four meters at the West Pingdingshan Section, in which the key indices of defining the boundary and the chief transitional processes of some parameters at the boundary are included. The relationship between the boundaries defined by ammonoids and by conodonts is well clarified at the section. The magnetic polarity analysis shows that the boundary interval belongs to a normal polarity zone. Both the carbonate and organic carbon isotopes com- positions experienced a significant conversion in the boundary interval.

关键词： Lower Triassic, Induan-Olenekian boundary, GSSP, candidate, Chaohu of China.

Annual temperatures during the last 2485 years in the mid-eastern Tibetan Plateau inferred from tree rings

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Science China Earth Sciences 2009年第3期52卷 348-359页

作者： hans W. LINDERHOLM Regional Climate Group Department of Earth Sciences University of Gothenburg

By combining living trees and archaeological wood, the annual mean temperatures were reconstructed based on ring-width indices of the mid-eastern Tibetan Plateau for the past 2485 years. The climate variations revealed by the reconstruction indicate that there were four periods to have average tem- peratures similar to or even higher than that mean of 1970 to 2000 AD. A particularly notable rapid shift from cold to warm, we call it the "Eastern Jin Event", occurred from 348 AD to 413 AD. Calculation re- sults show that the temperature variations over the mid-eastern Tibetan Plateau are not only repre- sentative for large parts of north-central China, but also closely correspond to those of the entire Northern Hemisphere over long time scales. During the last 2485 years, the downfall of most major dynasties in China coincides with intervals of low temperature. Compared with the temperature records in other regions of China during the last 1000 years, this reconstruction from the Tibetan Plateau shows a significant warming trend after the 1950s.

关键词： mid-eastern Tibetan Plateau tree rings temperature variations dynasty’s downfall

Microtubule affinity regulating kinase(MARK/Par1)isoforms differentially regulate Alzheimer-like TAU missorting and Aβ-mediated synapse pathology

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Neural Regeneration Research 2023年第2期18卷 335-336页

作者： Jana Chudobová hans Zempel Institute of Human Genetics Faculty of Medicine and University Hospital Cologne Center for Molecular Medicine Cologne(CMMC) University of CologneCologneGermany

Importance of TAU protein for dementia syndromes:Dementia currently affects about 55 million people worldwide,with Alzheimer's disease(AD)being the most prevalent *** one crucial pathological hallmark of AD that correlates best with loss of synapses and cognitive decline are the so-called intracellular neurofibrillary tangles composed of mislocalized/missorted and hyperphosphorylated TAU protein(Naseri et al.,2019).Many other neurodegenerative diseases,both genetic and nongenetic,are characterized by neurofibrillary ta ngles or pathological accumulation of the protein TAU and are thus termed"tauopathies".

关键词： Alzheimer diseases

A simple human cell model for TAU trafficking and tauopathy-related TAU pathology

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Neural Regeneration Research 2022年第4期17卷 770-772页

作者： Michael Bell hans Zempel Institute of Human Genetics Faculty of Medicine and University Hospital CologneUniversity of CologneCenter for Molecular Medicine Cologne(CMMC)University of CologneCologneGermany

The microtubule(MT)-associated protein TAU is highly abundant in the axon of human brain neurons,where it binds to and stabilizes MT ***,TAU regulates the dynamic(dis)assembly of MT strands and is involved in a wide range of neuronal *** Alzheimer's disease(AD)and other tauopathies,TAU is missorted into the somatodendritic *** missorting is accompanied by(or leads to)abnormal TAU phosphorylation,MT destabilization,and loss of dendritic spines and mitochondria,eventually resulting in TAU aggregation,neuronal dysfunction and cell death(Arendt et al.,2016).Strikingly,the mechanisms of TAU sorting,and the detrimental cascade upon its failure,are still not fully understood.

关键词： tau sorting eventually