检索结果-南通市图书馆

Implementation and validation of a bonded particle model to predict rheological properties of viscoelastic materials

引用

Particuology 2024年第6期89卷 198-210页

作者： Michael Mascara Arno Mayrhofer Stefan Radl Christoph Kloss Institute of Process and Particle Engineering Graz University of TechnologyInffeldgasse 13Graz8010Austria DCS Computing GmbH Industriezeile 35Linz4020Austria

This work focuses on implementing a particle-based method able to characterize viscoelastic materials whose rheological properties,such as storage modulus G′and loss modulus G″,are known.It is based on the bonded particle model,with the elastic constitutive relation here substituted with a viscoelastic one to capture time-scale effects.The Burgers model,vastly used in literature to model viscoelastic systems,is discretized and implemented.The test case used for calibration comprises of a cubic lattice,sheared with a periodic motion,to mimic the effect of a shear rheometer.After appropriate filtering of the stress response,the rheological properties are obtained,highlighting the effect of the lattice geometry,as well as the particle size,on the accuracy of the model.Moreover,the Burgers parameters are calibrated by analytically fitting the experimental dataset,showing the limitation of the Burgers model.The micro-contact parameters are obtained from the macro parameters through appropriate scaling.After completing a frequency sweep,the simulated G′and G″show a relatively large error,around 25%for G’for example.For this reason,a more robust model,namely the generalized Maxwell model,has been implemented.The calibration procedure is performed in the same fashion as for the Burgers model.Moreover,the tangential micro-contact parameters are scaled w.***.t.the normal ones.This scaling parameter,calledα,is calibrated by minimizing the root mean square error between simulation and experimental data,giving errors below 10%in both G′and G″for a large dataset.Additionally,a full ring plate-plate rheometer setup is simulated,and the simulation is compared with the given experimental dataset,again finding a good agreement.

关键词： DEM Rheology Numerical modeling Viscoelasticity

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Testing and modelling of transient adhesion phenomena in rolling-sliding contacts

引用

Friction 2024年第5期12卷 1016-1027页

作者： Daniel KVARDA Alexander MEIERHOFER Klaus SIX Faculty of Mechanical Engineering Brno University of TechnologyBrno61669Czech Republic Virtual Vehicle Research GmbH Graz8010Austria

Transient adhesion effects in rolling–sliding contacts influence all aspects of train–track interaction.This is of high importance specifically when these effects result in critically low adhesion,which poses a risk to traction and braking of railway vehicles.This study presents a model that can replicate the transient changes of the coefficient of adhesion with tested water and solid particle mix.The experimental data for the model are measured using a commercial ball-on-disc tribometer.The experimental results showed a liquid reservoir in front of the contact area that slowly reduces in size.This observation was used in the modelling approach to divide the calculation into two stages where the reservoir is present and when it disappears.The model was able to reproduce the occurrence of low adhesion region seen in experimental results with different particle concentrations.

关键词： coefficient of adhesion tribology transient effects wheel-rail contact

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Identity of Urban Spaces: Assessment and Evaluation

引用

Journal of Civil Engineering and Architecture 2024年第5期18卷 254-259页

作者： Elham Madadi-Kandjani Institute of Urbanism Graz University of TechnologyGraz 8010Austria

As a major symbol of civilization,the city was built by man for his security and comfort.It is not only a settlement,but also an urban development which has been identified with the spirit that has been breathed into the community.Urban identity which is also known as collective identity,has gained meaning through the content of objective manifestation and the creation of flashbacks,citizens’memories and mental associations.That is what makes urban dwellers become citizens.Although the identity of the city is a result of civic culture,it still has an influence on the process of citizenship and can also be a reason for developing criteria related to the participation and assessment of its inhabitants.According to the view that identity is a set of traits and characteristics that distinguishes the dignity of a person and a society from other individuals and communities,a city becomes characterized and independent by adhering to these criteria.Despite the importance of identity as one of the richest qualitative aspects of urban life that gives meaning and fulfilment to the human quiddity,this complicated and expanded concept has still not been seriously considered,especially in relation to urban spaces.In fact,identity in architecture and urban spaces has recently diminished,since the main focus lies on building spaces for optimized profit and not for high quality living areas.In this research paper,parameters affecting urban identity are evaluated,and strategies and guidelines to promote these parameters are finally presented.

关键词： Identity urban spaces quality of life urban development strategies

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Changes in children’s cardiorespiratory fitness and body mass index over the course of the COVID‑19 pandemic:a 34‑month longitudinal study of 331 primary school children

引用

World Journal of Pediatrics 2024年第2期20卷 185-188页

作者： Gerald Jarnig Reinhold Kerbl Mireille N.M.van Poppel Institute of Human Movement Science Sport and HealthUniversity of GrazMozartgasse 148010 GrazAustria Department of Pediatrics and Adolescent Medicine LKH Hochsteiermark8700 LeobenAustria

In late 2019,heavy restrictions were enforced on public activities worldwide to diminish the spread of the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)virus[1].These restrictions,which included school closures and strictly limited sports and leisure opportunities,particularly impacted children and adolescents[2].Lifestyle changes in children and adolescents led to reduced physical activity levels[2,3],increased sedentary behavior[3,4],changes in eating habits,and changes in sleep habits[3].

关键词： respiratory acute children

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Multi-layer perceptron-based data-driven multiscale modelling of granular materials with a novel Frobenius norm-based internal variable

引用

Journal of Rock Mechanics and Geotechnical Engineering 2024年第6期16卷 2198-2218页

作者： Mengqi Wang Y.T.Feng Shaoheng Guan Tongming Qu Zienkiewicz Centre for Computational Engineering Faculty of Science and EngineeringSwansea UniversitySwanseaWalesSA18EPUK Institute of Theoretical and Computational Physics Graz University of TechnologyGraz8010Austria Department of Civil and Environmental Engineering Hong Kong University of Science and TechnologyClearwater BayKowloonHong KongChina

One objective of developing machine learning(ML)-based material models is to integrate them with well-established numerical methods to solve boundary value problems(BVPs).In the family of ML models,recurrent neural networks(RNNs)have been extensively applied to capture history-dependent constitutive responses of granular materials,but these multiple-step-based neural networks are neither sufficiently efficient nor aligned with the standard finite element method(FEM).Single-step-based neural networks like the multi-layer perceptron(MLP)are an alternative to bypass the above issues but have to introduce some internal variables to encode complex loading histories.In this work,one novel Frobenius norm-based internal variable,together with the Fourier layer and residual architectureenhanced MLP model,is crafted to replicate the history-dependent constitutive features of representative volume element(RVE)for granular materials.The obtained ML models are then seamlessly embedded into the FEM to solve the BVP of a biaxial compression case and a rigid strip footing case.The obtained solutions are comparable to results from the FEM-DEM multiscale modelling but achieve significantly improved efficiency.The results demonstrate the applicability of the proposed internal variable in enabling MLP to capture highly nonlinear constitutive responses of granular materials.

关键词： Granular materials History-dependence Multi-layer perceptron(MLP) Discrete element method FEM-DEM Machine learning

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Mechanical upper bowel obstruction caused by a large trichobezoar in a young woman: A very unusual case report

引用

World Journal of Clinical Cases 2024年第4期12卷 777-781页

作者： Magdalena Scherrer Peter Kornprat Robert Sucher Johanna Muehlsteiner Doris Wagner Department of Surgery Division for GeneralVisceral and Transplantation SurgeryMedical University of GrazGraz 8036Austria Department of Surgery Clinic RohrbachRohrbach 4150Austria

BACKGROUND Bezoars usually compile human fibers and debris.A special form of bezoar in case of psychologically altered individuals is the trichobezoar.It consists of voluntarily swallowed hair bulks and is normally removed via gastroscopy.Trichobezoars leading to ileus have rarely been reported.CASE SUMMARY A 24-year-old female patient presented to the emergency room with abdominal pain,nausea,and vomiting for 3 d.Her previous medical and psychiatric history was unremarkable.Laboratory analysis showed iron deficiency anemia,leukocytosis,and elevated liver enzymes.An abdominal CT scan revealed a dense structure in the patients’stomach which turned out to be a huge trichobezoar completely obstructing the pylorus.The trichobezoar had to be removed surgi-cally.During her postoperative course,a subcutaneous seroma formed.After a single puncture,the rest of the recovery process was unremarkable,and the patient recovered fully.CONCLUSION A mechanical bowel obstruction is a potentially life-threatening event for every patient.In our case a young female was suffering from severe symptoms of an obstruction which might have resulted in serious harm without successful surgical management.

关键词： Rapunzel syndrome Hair ingestion Gastroscopy Bezoar Case report

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chronic effects of stretching on range of motion with consideration of potential moderating variables:A systematic review with meta-analysis

引用

Journal of Sport and Health Science 2024年第2期13卷 186-194页

作者： Andreas Konrad Shahab Alizadeh Abdolhamid Daneshjoo Saman Hadjizadeh Anvar Andrew Graham Ali Zahiri Reza Goudini Chris Edwards Carina Scharf David George Behm Institute of Human Movement Science Sport and HealthGraz UniversityGraz A-8010Austria School of Human Kinetics and Recreation Memorial University of NewfoundlandSt.John’sNL A1C 5S7Canada Department of Sport Injuries and Corrective Exercises Faculty of Sport SciencesShahid Bahonar University of KermanKerman 76169-13439Iran

Background:It is well known that stretch training can induce prolonged increases in joint range of motion(ROM).However,to date more information is needed regarding which training variables might have greater influence on improvements in flexibility.Thus,the purpose of this metaanalysis was to investigate the effects of stretch training on ROM in healthy participants by considering potential moderating variables,such as stretching technique,intensity,duration,frequency,and muscles stretched,as well as sex-specific,age-specific,and/or trained state-specific adaptations to stretch training.Methods:We searched through PubMed,Scopus,Web of Science,and SportDiscus to find eligible studies and,finally,assessed the results from 77 studies and 186 effect sizes by applying a random-effect meta-analysis.Moreover,by applying a mixed-effect model,we performed the respective subgroup analyses.To find potential relationships between stretch duration or age and effect sizes,we performed a meta-regression.Results:We found a significant overall effect,indicating that stretch training can increase ROM with a moderate effect compared to the controls(effect size=-1.002;Z=-12.074;95%confidence interval:-1.165 to-0.840;p<0.001;I^(2)=74.97).Subgroup analysis showed a significant difference between the stretching techniques(p=0.01)indicating that proprioceptive neuromuscular facilitation and static stretching produced greater ROM than did ballistic/dynamic stretching.Moreover,there was a significant effect between the sexes(p=0.04),indicating that females showed higher gains in ROM compared to males.However,further moderating analysis showed no significant relation or difference.Conclusion:When the goal is to maximize ROM in the long term,proprioceptive neuromuscular facilitation or static stretching,rather than ballistic/dynamic stretching,should be applied.Something to consider in future research as well as sports practice is that neither volume,intensity,nor frequency of stretching were found to play a significant role in ROM yields.

关键词： Flexibility Long-term stretching Stretch training

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Phytochemical analysis, antioxidant, acetylcholinesterase, and α-amylase inhibitors from Hippeastrum hybridum extract

引用

Journal of Traditional Chinese Medicine 2024年第3期44卷 496-504页

作者： Naila Sher Mushtaq Ahmed Nadia Mushtaq Department of Biotechnology University of Science and Technology Department of Botany University of Science and Technology

OBJECTIVE:To investigate the effects of Hippeastrum hybridum（HH） as a free radical scavenger,and an inhibitor of the two enzymes i-e Alpha-amylase（α-amylase） and acetylcholinesterase（AChE）.METHODS:In this study,HH plant was preliminary analyzed for phytochemical screening and then tested for its antioxidant,anti-α-amylase,and anti-AChE efficiency via standard procedures.RESULTS:Phytochemical analysis shows the existence of different compounds;while Coumarins and quinones were absent.The total phenolic,flavonoid,and tannins content were found to be（78.52±0.69） mg GAE/g,（2.01±0.04） mg RUE/g,and（58.12±0.23） mg TAE/g of plant extract respectively.28.02%±0.02% alkaloid and 2.02%±0.05% saponins were present in the HH extract.The HH extract showed the anti-oxidant property with IC50（50%inhibition） of（151.01±0.13）(HH),（79.01±0.04）(Ascorbic acid) for ferric reducing,（91.48±0.13）(HH),（48.02±0.11）(Ascorbic acid) against Ammonium molybdenum,（156.02±0.31）(HH),（52.38±0.21）(Ascorbic acid) against DPPH,136.01±0.21（HH）,52.02±0.31（Ascorbic acid） against H2O2,and 154.12±0.03（HH）,（40.05±0.15）(Ascorbic acid)μg/mL against ABTS respectively.Statistical analysis indicated that HH caused a competitive type of inhibition of α-amylase(Vmaxremained constant and Km increases from 10.65 to84.37%) while Glucophage caused the un-competitive type of inhibition i-e both Km and Vmaxdecreased from40.49 to 69.15%and 38.86 to 69.61%respectively.The Ki,（inhibition constant）;KI,（dissociation constant）,Km,（Michaelis-Menten constant）,and IC50 were found to be62,364,68.1,and 38.08±0.22 for HH and 12,101.05,195,34.01±0.21 for Glucophage.Similarly,HH causes an anon-competitive type of inhibition of AChE i-e Km remains constant while Vmaxdecreases from 60.5%to74.1%.The calculated Ki,KI,Km,and IC50 were found to be 32,36.2,0.05,and 18.117±0.018.CONCLUSION:From the current results,it is concluded that HH extract contains bioactive compounds,and could be a good alternative to controlling oxidants,Alzheimer‘s and Type-Ⅱ diabetic diseases.

关键词： Hippeastrum hybridum acetylcholinesterase alpha-amylase antioxidant phytochemicals

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Statistical study of magnetic holes in the upstream region of Mercury’s bow shock

引用

Earth and Planetary Physics 2024年第2期8卷 326-337页

作者： GuoQiang Wang SuDong Xiao MingYu Wu YuanQiang Chen TieLong Zhang Institute of Space Science and Applied technology Harbin Institute of TechnologyShenzhen 518055China Shenzhen Key Laboratory of Numerical Prediction for Space Storm Harbin Institute of TechnologyShenzhen 518055China Mengcheng National Geophysical Observatory University of Science and Technology of ChinaHefei 230026China Chinese Academy of Sciences Center for Excellence in Comparative Planetology Hefei 230026China Space Research Institute Austrian Academy of SciencesGrazAustria

Magnetic holes are magnetic depression structures that exist widely in many plasma environments.The magnetic holes with durations of>1 s in the solar wind at Mercury’s orbit have drawn much attention,but the properties of the magnetic holes with shorter durations are still unclear.Here,we investigate the magnetic holes with durations of 0.1-100 s in the upstream region of Mercury’s bow shock based on observations by the MESSENGER(MErcury Surface,Space ENvironment,GEochemistry,and Ranging)spacecraft.They can be divided into two groups according to the distribution of their duration:small-duration magnetic holes(SDMHs,0.6 s).The duration of each group approximately obeys a log-normal distribution with a median of~0.25 s and 3 s,respectively.Approximately 1.7%(32.6%)of the SDMHs(LDMHs)reduce the magnetic field strength by more than 50%.For both groups,some structures have a linear or quasi-linear polarization,whereas others have an elliptical polarization.The magnetic hole events in both groups tend to have a higher rate of occurrence when the interplanetary magnetic field strength is weaker.Their occurrence rates are also affected by Mercury’s foreshock,which can increase(decrease)the occurrence rate of the SDMHs(LDMHs).This finding suggests that Mercury’s foreshock might be one source of the SDMHs and that the foreshock can destroy some LDMHs.These observations suggest that a new group of magnetic holes with durations of<0.6 s exist in the upstream region of Mercury’s bow shock.

关键词： magnetic hole solar wind Mercury foreshock

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

An underwater vest containing an antioxidant MXene hydrogel for sensitive recognition of fish locomotion

引用

Microsystems & Nanoengineering 2024年第2期10卷 115-131页

作者： Chengxiu Yang Jiafei Hu Lihui Liu Shaowei Wu Mengchun Pan Yan Liu Haomiao Wang Peisen Li Qi Zhang Weicheng Qiu Huihui Luo College of Intelligence Science and technology National University of Defense TechnologyChangsha410073China

The perception of fish locomotion is important for understanding their adaptive behaviors and ethological characteristics.However,the main strategy used for extracting fish attitudes involves the use of a vision-based monitoring system,which is limited in its range of observation and cannot perform tracking for long times.Here,we report the use of a wearable tagging electronic device,referred to as an underwater vest,to capture the surrounding flow field disturbances triggered by swimming or momentary postural changes.All of these goals were achieved by integrating a pair of pseudocapacitive pressure-sensing units and a flexible circuit board.Notably,additional conditions,such as variable hydraulic pressures and minimal changes in fish posture,require high stability and sensitivity of the sensing units.Thus,hybrid hydrogel electrodes were developed through cross-linking MXene with holey-reduced graphene oxide nanosheets and further modification with 1-ethyl-3-methylimidazolium dicyanamide ionic liquids,which increased the interfacial capacitance and long-term interfacial activity of the MXene.Consequently,the sensing unit exhibited ultrahigh sensitivity(S_(max)~136,207 kPa^(−1))in an aquatic environment for 60 days and superior high-pressure resolution(10 Pa)within a wide working range of 1 MPa.Ultimately,an underwater vest integrated with such sensing units clearly distinguished and recorded fish locomotion.We believe that the designed device may open avenues in flow field monitoring and ocean current detection and provide new insights into the development of sensitive underwater tagging.

关键词： underwater fish linking

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：