•The modeling of nonlinear aerodynamic damping of crosswind response of tall buildings is addressed.•The unique crosswind response characteristics and its extreme statistics are studied.•The method ...of equivalent nonlinear equation is applied, at the first time, to predict crosswind response.•It gives accurate analytical predictions of RMS response, peak factor and extreme value distribution.
This study addresses the analysis of crosswind response of tall buildings and flexible structures at wind speed region higher than the vortex lock-in speed, where nonlinear negative aerodynamic damping effect is significant. The modeling of nonlinear aerodynamic damping as a function of time-varying velocity and/or displacement of vibration is established based on motion-induced aerodynamic force information obtained from forced-vibration model testing in wind tunnel, referred to as harmonic balance. Response time history simulations are performed by solving the nonlinear equation of motion to explore the unique hardening non-Gaussian characteristics of crosswind response and its extreme value distribution with reduced peak factor. The response time history simulations also provide a bases for assessing the performance of analytical predictions of root-mean-square (RMS) response using crosswind loading spectrum and equivalent aerodynamic damping models. The limitations of the equivalent aerodynamic damping models as functions of RMS response derived from harmonic balance and statistical linearization with an assumption of Gaussian response are revealed. This study, at the first time, by using the method of equivalent nonlinear equation, presents complete analytical solutions of crosswind response statistics, including not only the RMS response, but also response kurtosis, response probability distribution, peak factor and extreme value distribution. The comparison of the analytical predictions with response simulation results illustrates that the method of equivalent nonlinear equation is very accurate in predicting crosswind response statistics that are influenced by the nonlinear aerodynamic damping. The narrow band feature of response is further considered in this study in the calculation of crossing rate using amplitude process, which leads to even better predictions of extreme statistics. This general framework can also be readily adopted in design codes and standards for calculating vortex-induced vibration of towers and chimneys.
•An analysis framework for crosswind fatigue of wind-excited structures is presented.•The hardening non-Gaussian response character caused by nonlinear aerodynamic damping is considered.•A correction ...factor as a function of response kurtosis is introduced for analysis of non-Gaussian fatigue.•The accuracy of proposed framework is illustrated using simulated and full-scale response data.
This study addresses crosswind fatigue analysis of wind-excited flexible structures at the vicinity of vortex lock-in speed where the nonlinear aerodynamic damping effect is significant. The nonlinear aerodynamic damping is modeled as a polynomial function of time-varying displacement or velocity of vibration. The crosswind response is a narrow-band hardening non-Gaussian process with a reduced peak factor and having a distribution of vibration amplitude different from Rayleigh distribution. Analytical solutions of cycle number and fatigue damage are derived and their accuracy is validated through comparison with rainflow cycle counting method using simulated response time histories. A correction factor as a function of response kurtosis is also introduced that facilitates the calculation of non-Gaussian fatigue damage from the Gaussian fatigue prediction. The effectiveness and accuracy of the proposed framework are illustrated by crosswind responses of a squared tall building and a two-dimensional structural section model, and by full-scale vibration measurement data of a traffic-signal-support-structure. This study provides an improved estimation of crosswind fatigue of wind-excited flexible structures with a consideration of hardening non-Gaussian response character.
•Extreme value analysis methods for non-Gaussian wind effects using short-term time history samples are investigated.•The long-term wind pressure coefficient wind tunnel data of a large-span roof are ...used as the basis for comparison.•These pressure coefficient data are featured by a variety of non-Gaussian characteristics.•New developments of the methods are presented taking into account the non-Gaussian characteristics.
This study presents a comprehensive assessment of various methods for extreme value analysis of non-Gaussian wind effects using short-term time history samples. The methods examined are peaks-over-threshold (POT) method, the average conditional exceedance rate (ACER) method, and the translation process method with various translation models. The long-term wind pressure coefficient data on a saddle-shaped large-span roof collected from wind tunnel test are used as the basis for comparison. These pressure coefficient data are featured by a variety of non-Gaussian characteristics, including mildly and strongly softening and hardening non-Gaussian processes with unique distributions. Some new developments of the methods are also presented to better predict the extreme value distribution taking into account the non-Gaussian characteristics. The declustering of process to extract independent peaks over a given threshold for POT method is discussed. The effectiveness of the ACER method is firstly examined as applied to non-Gaussian wind pressures. Regarding the translation process method, this study highlights the limitations of widely used moment-based method and the method based on three-parameter gamma distribution of the process. A mixture distribution model is introduced for better modeling the distribution tail and estimation of extreme value distribution. This mixture distribution method and the method based on curve-fitting of translation function derived from mapping of cumulative distribution functions are illustrated to be capable of capturing the upper tail of translation function, thus lead to satisfactory estimations of extreme statistics for a variety of non-Gaussian processes.
•An approach based on crossing rate analysis is proposed.•It is for estimating extreme statistics of narrow band non-Gaussian crosswind response.•Its accuracy is confirmed by simulated response and ...full-scale vibration data.•It is very effective when the number of response time histories is very limited.
This paper presents an approach based on response crossing rate analysis for estimating extreme value distribution of crosswind response of wind-excited structures with significant nonlinear aeroelastic effect. The crossing rates at various thresholds are calculated from response time histories, and are then curve-fitted by a prescribed parametric model. The influence of narrow band characteristic of response is accounted by using envelope process with two-state description of crossings and a further consideration of mean clump size. The curve-fitting and extrapolation of crossing rate permit estimation of extreme value distribution using Poisson distribution of crossings. The effectiveness and accuracy of the approach are examined using simulated crosswind responses covering a wide range of non-Gaussian characteristics, and also using full-scale vibration measurement data of a wind-excited traffic-signal-support structure. The results illustrated that the approach can produce robust estimations of extreme value distributions of hardening non-Gaussian crosswind responses. The narrow band characteristic of response process has very limited effect on the extremes of hardening non-Gaussian responses. The approach presented is especially effective in practice, where the number of available response time histories is often very limited, and a direct use of extreme samples fails to provide accurate estimation of extreme statistics.
Infrared and optical spectroscopy represents one of the most informative methods in advanced materials research. As an important branch of modern optical techniques that has blossomed in the past ...decade, scattering‐type scanning near‐field optical microscopy (s‐SNOM) promises deterministic characterization of optical properties over a broad spectral range at the nanoscale. It allows ultrabroadband optical (0.5–3000 µm) nanoimaging, and nanospectroscopy with fine spatial (<10 nm), spectral (<1 cm−1), and temporal (<10 fs) resolution. The history of s‐SNOM is briefly introduced and recent advances which broaden the horizons of this technique in novel material research are summarized. In particular, this includes the pioneering efforts to study the nanoscale electrodynamic properties of plasmonic metamaterials, strongly correlated quantum materials, and polaritonic systems at room or cryogenic temperatures. Technical details, theoretical modeling, and new experimental methods are also discussed extensively, aiming to identify clear technology trends and unsolved challenges in this exciting field of research.
Scattering‐type scanning near‐field optical microscopy (s‐SNOM) allows ultrabroadband optical (0.5–3000 µm) nanoimaging and nanospectroscopy with fine spatial (<10 nm), spectral (<1 cm−1), and temporal (<10 fs) resolution. Recent progress in the s‐SNOM technique and its application in material research at room and cryogenic temperatures is summarized.
Transient nonstationary extreme winds such as thunderstorm downbursts are responsible for significant structural damage and failures. This study deals with the frequency domain analysis of alongwind ...tall building response to transient nonstationary winds based on nonstationary random vibration theory. The transient wind fluctuations and associated wind loads are modeled as the sum of deterministic time varying mean and evolutionary random fluctuating components. The alongwind loads on buildings are determined through the approaching winds by using strip theory and taking into account the unsteady force characteristics in terms of aerodynamic admittance and joint acceptance functions. An analysis framework is developed to quantify the time varying mean, evolutionary spectrum, and time varying root-mean-square values of building response. The traditional analysis framework concerning stationary boundary layer winds serves as a special case of this novel framework. Applications of this general framework are addressed to the cases where the mean wind speed is characterized by a time-invariant vertical profile and a single time varying function that also serves as the modulation function for the wind fluctuations. The influence of time varying mean wind speed, mean wind speed vertical profile, and spatial correlation of wind fluctuations on building response is discussed using tall building examples.
Sensory perception and emotional disorders are disproportionally represented in men and women and are thus thought to be modulated by different sex hormones in various conditions. Among the most ...important hormones perceived to affect sensory processing and transduction is estrogen. Numerous previous researchers have endeavored to demonstrate that estrogen is capable of modulating the activity of sensory neurons in peripheral and central sites in female, male, or castrated animals. However, the underlying mechanisms of its modulation of neuronal activity are somewhat unclear. In the present review, we discuss the possible cellular and molecular mechanisms involved in the modulation of nociception by estrogen.
•Response characters of friction-pendulum base-isolated high-rise buildings subjected to wind load are revealed.•Three response history analysis approaches associated with frictional system are ...compared for wind-induced response.•Two statistical linearization methods are utilized to estimate STD of structural response.•Influences of important parameters associated with FPB on structural response are investigated.
Base isolation technology is widely accepted as an effective strategy for the seismic design of buildings. Although the elastomeric isolator is still extensively adopted for the base-isolation system in practice, there is a trend to use the frictional pendulum bearing (FPB) due to its high vertical bearing capacity, stable performance and good recentering capability. In this paper, the dynamic response of base-isolated high-rise buildings with FPB having a velocity-dependent friction coefficient subjected to uncoupled alongwind and crosswind loads is studied. The response characteristics calculated from response history analysis (RHA) are analyzed. Meanwhile, two statistical linearization methods are utilized to estimate the standard deviation (STD) of the structural response and to obtain the equivalent parameters of the linearized system. The time-varying mean of the base displacement under alongwind load with a non-zero mean is also discussed by the linearization method. Finally, a parameter analysis of the isolation bearing is performed to investigate the effects of the radius and friction coefficient of the sliding plate on the wind-induced vibration. This study highlights the strong nonlinear response characteristics of base-isolated high-rise buildings with FPB and offers design guidelines under strong winds.
•Non-Gaussian wind fields are simulated using translation process theory and spectral representation method.•Wind turbine responses at both operational and parked conditions to non-Gaussian wind ...fields are investigated.•The influence of non-Gaussian wind fields on response statistics and extreme value distribution is analyzed.•The non-Gaussian wind inflows can result in noticeably larger extreme responses with large mean recurrence intervals.•New insights on the determination of extreme response distribution from random process method are presented.
The wind turbulence inflows specified in current wind turbine design standards and turbine response simulation tools are usually modeled as stationary random Gaussian processes. Field measurement data, however, suggest that wind turbulence in complex terrain exhibits non-Gaussian characteristics. This study presents a comprehensive investigation on extreme response of operational and parked wind turbines to non-Gaussian wind field. The non-Gaussian wind fields with specified non-Gaussian statistics and power spectral characteristics are generated using translation process theory and spectral representation method. The wind turbine response time histories at each wind speed bin are simulated. The turbine response statistical moments influenced by the non-Gaussian wind inflow are examined. The extreme response distributions conditional on wind speeds are determined from the simulation data using global maxima method and random process model method. The overall extreme response distribution is then calculated by further integrating the distribution of mean wind speed, which is used to quantify the extreme responses with various mean recurrence intervals (MRIs). The results showed that the non-Gaussian characteristics of wind inflows can result in noticeably larger extremes of blade root edgewise and tower base fore-aft bending moments of operational turbine, and blade root flapwise bending moment of parked turbine. The responses with larger MRIs are more sensitive to the non-Gaussian characteristics of wind inflows. The responses of parked turbine are less sensitive to non-Gaussian, especially, the tower base side-to-side bending moment is almost not affected by non-Gaussian. New insights on the determination of extreme response distribution from random process method are also presented focusing on a better modeling of the response distribution tail.
Despite several attempts made to analyze students’ socialization into academic discourse in relevant reviews, we still lack a topical study providing an overview of how students are apprenticed into ...academic communities through oral activities at post-secondary institutions. This study aims at contributing to a comprehensive overview of both theoretical and empirical studies in the field of academic discourse socialization (ADS). A systematic review approach was adopted due to the qualitative and quantitative research design and connections between theory and evidence. The material search of ADS literature published between 2000 and 2022 resulted in 72 studies in total. While the synthesis of theoretical studies reveal the extant definitions, categorization of characteristics and theoretical orientations, the empirical study findings compare differences in participants and contexts, research approaches, communication events, and academic outcomes. This review also discusses major areas of research concerning ADS, mainly types of socialization agents, students’ feedback, learners’ identity construction, and assessment of consequences of ADS. With limitations concluded, the review encourages further focused investigation into micro-macro connections, application of digital technologies, a wider range of participants, disciplines and contexts, multiple types of oral activities and perspectives, learners’ linguistic production as well as correlation of oral and written texts, and joint efforts from multiple sides.
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