检索结果-南通市图书馆

Output-only identification of the modal and physical properties of structures using free vibration response

在线全文

学校读者我要写书评

暂无评论

Earthquake Engineering and Engineering Vibration 2016年第3期15卷 575-589页

作者： Carlos A.Gaviria luis A.Montejo Civil Engineering Program Facultad de Estudios a DistanciaUniversidad Militar Nueva GranadaColombia Department of Civil Engineering and Surveying University of Puerto Rico at MayaguezMayaguezPR 00681-9000Puerto Rico) Department of Engineering Science and Materials University of Puerto Rico at MayaguezMayaguezPR 00681-9000Puerto Rico

The viability of a complete structural characterization of civil structures is explored and discussed. In particular, the identification of modal （i.e. natural frequencies, damping ratios and modal shapes） and physical properties （i.e. mass and stiffness） using only the structure＇s free decay response is studied. To accomplish this, modal analysis from flee vibration response only （MAFVRO） and mass modification （MM） methodologies are engaged along with Wavelet based techniques for optimal signal processing and modal reconstruction. The methodologies are evaluated using simulated and experimental data. The simulated data are extracted from a simple elastic model of a 5 story shear building and from a more realistic nonlinear model of a RC frame structure. The experimental data are gathered from shake table test of a 2-story scaled shear building. Guidelines for the reconstruction procedure from the data are proposed as the quality of the identified properties is shown to be governed by adequate selection of the frequency bands and optimal modal shape reconstruction. Moreover, in cases where the structure has undergone damage, the proposed identification scheme can also be applied for preliminary assessment of structural health.

关键词： mass modification method output-only modal analysis time-frequency analysis continuous waveletstransform Hilbert transform damping

Prevalence of gastroesophageal reflux disease:a population-based cross-sectional study in southern Chile

在线全文

学校读者我要写书评

暂无评论

Gastroenterology Report 2020年第4期8卷 286-292,I0001,I0002页

作者： Carlos Manterola luis Grande luis Bustos Tamara Otzen Center of Morphological and Surgical Studies Universidad de La FronteraTemucoChile Department of Surgery Universidad de La FronteraTemucoChile Department of Surgery Hospital del MarUniversitat Auto`noma de BarcelonaBarcelonaSpain Department of Public Health Universidad de La FronteraTemucoChile

Background This study assessed the prevalence of gastroesophageal reflux disease(GERD)in a general adult population from Temuco in southern *** association of GERD with demographic variables was also *** A cross-sectional study among the general population of Temuco in southern Chile was conducted in 2017,using a validated and reliable questionnaire for detecting *** urban area of Temuco,with a population of 245,317 inhabitants(2002 census),was divided into four zones,which were representative of the socioeconomic sectors of the *** sample size was estimated assuming a prevalence of 52.8%,an accuracy of 3.0%,a confidence level of 95.0%,and a design effect of *** sampling was used to build *** prevalence of GERD was determined and associated factors were studied by means of bivariate and multivariate *** A total of 1,069 subjects(47.9%women,median age 40 years)from the selected subareas were *** prevalence of GERD was 44.8%.The most frequently reported symptom was regurgitation(54.8%).One-third of subjects took medication to control symptoms and was considered‘sick’by the instrument,although>68%of them had never sought medical *** was a significant association between GERD and age(P<0.001)and female gender(P=0.001).Conclusions In this population-based study,the prevalence of GERD was high(44.8%).GERD was associated with age and female gender.

关键词： gastroesophageal reflux disease prevalence cross-sectional studies evidence-based medicine clinical epidemiology

CFD modelling:The most useful tool for developing mesoscale urban canopy parameterizations

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

Building Simulation 2021年第3期14卷 407-419页

作者： Riccardo Buccolieri Jose luis Santiago Alberto Martilli Dipartimento di Scienze e Tecnologie Biologiche edAmbientali University ofSalentoS.P.6 Lecce-MonteroniLecce 73700Italy Environment Department Research Center for EnergyEnvironment and Technology(CIEMAT)Madrid 28040Spain

1 Introduction The fact that most of the world’s population lives in cities(UN-Habitat 2016)has increased interest in urban *** models,such as the Weather Research and Forecasting(WRF)model(***/weather-research-and-forecasting-model),are used to reproduce the meteorology and climatology over cities and around them,where the complex interactions between the atmosphere and urban surfaces(buildings,vegetation,urban obstacles,etc.)induce strong heterogeneity in the flow properties within the urban canopy layer(UCL)(Di Sabatino et al.2013;Lateb et al.2016;Tominaga and Stathopoulos 2016).

关键词： meteorology urban forecasting

Assessment of wear micromechanisms on a laser textured cemented carbide tool during abrasive-like machining by FIB/FESEM

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

Friction 2021年第3期9卷 656-664页

作者： Shiqi FANG Dirk BÄHRE luis LLANES Institute of Production Engineering Saarland UniversitySaarbrücken 66123Germany CIEFMA-Department of Materials Science and Engineering EEBE-Campus Diagonal BesòsUniversitat Politècnica de CatalunyaBarcelona 08019Spain

The combined use of focused ion beam(FIB)milling and field-emission scanning electron microscopy inspection(FESEM)is a unique and successful approach for assessment of near-surface phenomena at specific and selected *** this study,a FIB/FESEM dual-beam platform was implemented to docment and analyze the wear micromechanisms on a laser-surface textured(LST)hardmetal(HM)*** particular,changes in surface and microstructural integrity of the laser-sculptured pyramids(effective cutting microfeatures)were characterized after testing the LST-HM tool against a steel workpiece in a workbench designed to simulate an external honing *** was demonstrated that:(1)laser-surface texturing does not degrade the intrinsic surface integrity and tool effectiveness of HM pyramids;and(2)there exists a correlation between the wear and loading of shaped pyramids at the local ***,the enhanced performance of the laser-textured tool should consider the pyramid geometry aspects rather than the microstructure assemblage of the HM grade used,at least for attempted abrasive applications.

关键词： focused ion beam(FIB) field-emission scanning electron microscopy inspection(FESEM) cemented carbides laser surface texturing abrasive machining processes wear

Linear viscoelastic behavior of asphalt binders and mixtures containing very high percentages of reclaimed asphalt pavement

在线全文

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2023年第8期17卷 1211-1227页

作者： Reza IMANINASAB luis LORIA-SALAZAR Alan CARTER Construction Engineering Department École de Technologie Supérieure(ÉTS)University of QuebecMontreal H3C 1K3Canada Civil Engineering Department Universidad Isaac NewtonSan José10108Costa Rica

The primary aim of this study is to correlate the impact of aggregates,if any,on the viscoelastic behavior of rejuvenated asphalt mixtures containing very high amounts of reclaimed asphalt pavement(RAP)(>50%).First,gradation of 100%RAP was rectified,using a modified Bailey method by adding virgin aggregates to achieve two coarse dense-graded and one fine dense-graded *** modulus test was then performed from−35 to+35℃and 0.01–10 *** addition to performance grade(PG)testing,extracted and recovered binders from different asphalt mixtures underwent shear complex modulus test within−8℃to high temperature PG and frequencies from 0.001 to 30 ***−Cole,Black space,complex modulus and phase angle master curves were constructed and ShiftHomothety-Shift in time-Shift(SHStS)transformation was used to compare the linear viscoelastic behavior of asphalt binders and *** influence of aggregates on the viscoelastic behavior of asphalt mixtures depends on temperature and/or *** role of asphalt binders in the behavior of asphalt mixtures is more pronounced at high temperatures and the effect of the aggregate structure increases as the temperature *** maximum difference(60%to 70%)in the viscoelastic behavior of the binder and mixture based on SHStS transformed Cole−Cole curves is within the phase angle of 15°–20°.

关键词： RAP complex modulus SHStS transformation rejuvenation behavior of asphalt binder and mixture

A renewal theory based performance and configuration framework of the IEEE 802.11ah RAW mechanism

在线全文

学校读者我要写书评

暂无评论

Digital Communications and Networks 2023年第1期9卷 236-251页

作者： Hamid Taramit luis Orozco-Barbosa Abdelkrim Haqiq Hassan First University of Settat Faculty of Sciences and TechniquesComputerNetworksMobility and Modeling Laboratory:IR2M26000 SettatMorocco Albacete Research Institute of Informatics Universidad de Castilla-La Mancha02006 AlbaceteSpain

IEEE 802.11ah is a new Wi-Fi standard for sub-1Ghz communications,aiming to address the challenges of the Internet of Things(IoT).Significant changes in the legacy 802.11 standards have been proposed to improve the network performance in high contention scenarios,the most important of which is the Restricted Access Window(RAW)*** mechanism promises to increase the throughput and energy efficiency by dividing stations into different *** this scheme,only the stations belonging to the same group may access the channel,which reduces the collision probability in dense ***,the standard does not define the RAW grouping *** this paper,we develop a new mathematical model based on the renewal theory,which allows for tracking the number of transmissions within the limited RAW slot contention period defined by the *** then analyze and evaluate the performance of RAW *** also introduce a grouping scheme to organize the stations and channel access time into different groups within the ***,we propose an algorithm to derive the RAW configuration parameters of a throughput maximizing grouping *** additionally explore the impact of channel errors on the contention within the time-limited RAW slot and the overall RAW optimal *** presented analytical framework can be applied to many other Wi-Fi standards that integrate periodic channel *** simulations using the MATLAB software validate the analytical model and prove the effectiveness of the proposed RAW configuration scheme.

关键词： IEEE 802.11ah Performance evaluation Renewal theory RAW mechanism Internet of things

Singular Integrals with Variable Kernels in Dyadic Settings

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2023年第8期39卷 1565-1579页

作者： Hugo AIMAR Raquel CRESCIMBENI luis NOWAK IMAL-CONICET and UNL Santa FeArgentina Departamento de Matemática FaEAUNCo.and IITCI-CONICETNeuquenArgentina

In this paper we explore conditions on variable symbols with respect to Haar systems,defining Calderón–Zygmund type operators with respect to the dyadic metrics associated to the Haar bases. We show that Petermichl’s dyadic kernel can be seen as a variable kernel singular integral and we extend it to dyadic systems built on spaces of homogeneous type.

关键词： Singular integrals spaces of homogeneous type Petermichl’s operator Haar basis

Recent advances on first-principles modeling for the design of materials in CO2 capture technologies

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2019年第7期27卷 1554-1565页

作者： Yue Yuan Huabei You luis Ricardez-Sandoval Chemical Engineering Department Tianjin UniversityTianjin 300072China Chemical Engineering Department University of Waterloo200 University Ave WWaterlooON N2L 3G1Canada

Novel technologies in consideration of industrial sustainability(IS)are in urgent need to satisfy the increasing demands from the *** realizes the production of materials while maintaining environmental and resource *** chemical materials used in CO2 capture and storage(CCS)technologies play a significant role in the disposal of greenhouse gas emissions coming from large stationary fossil-fired power plants,which breaks the principle of IS and brings severe environmental *** study aims at providing a detailed review of first-principles modeling(density functional theory,DFT)of materials in CO2 capture *** analysis provides insight into the atomic properties of the studied systems and builds an efficient guidance of the future design of the materials used in CO2 capture *** materials including oxygen carriers,metal organic frameworks,membranes,zeolites,ionic liquids and some other promising candidates are *** computational studies bring the outcomes of the adsorption behaviors,structural characteristics and accurate force fields of the studied materials in short turn-around times at low *** review can stimulate the design of novel materials with specific target of CO2 capture and promote the industrial sustainability of fossil fuel combustion technologies.

关键词： Industrial sustainability CO2 capture Density functional theory Fossil fuels

Cellular automata model for traffic flow with safe driving conditions

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2014年第5期23卷 216-226页

作者： María Elena Lárraga luis Alvarez-Icaza Instituto de Ingeniería Universidad Nacional Autónoma de México04510Coyoacán D.F.México

In this paper, a recently introduced cellular automata （CA） model is used for a statistical analysis of the inner micro-scopic structure of synchronized traffic flow. The analysis focuses on the formation and dissolution of clusters or platoons of vehicles, as the mechanism that causes the presence of this synchronized traffic state with a high flow. This platoon formation is one of the most interesting phenomena observed in traffic flows and plays an important role both in manual and automated highway systems （AHS）. Simulation results, obtained from a single-lane system under periodic boundary conditions indicate that in the density region where the synchronized state is observed, most vehicles travel together in pla- toons with approximately the same speed and small spatial distances. The examination of velocity variations and individual vehicle gaps shows that the flow corresponding to the synchronized state is stable, safe and highly correlated. Moreover, results indicate that the observed platoon formation in real traffic is reproduced in simulations by the relation between vehicle headway and velocity that is embedded in the dynamics definition of the CA model.

关键词： traffic flow models synchronized traffic cellular automata platoons formation