AbstractPerformance-based seismic design aims to dictate the structural performance in a predetermined fashion given the possible seismic hazard scenarios the structure is likely to experience. ...Identifying and assessing the probable performance is an integral part of performance-based design. Before implementation, accurate and practical definitions of different performance levels and corresponding limit states must be determined. This study aims to develop performance-based damage states for shape memory alloy (SMA)–reinforced concrete (RC) bridge piers considering different types of SMAs and seismic hazard scenarios. Using incremental dynamic analysis (IDA), this study develops quantitative damage states corresponding to different performance levels (cracking, yielding, and strength degradation) and specific probabilistic distributions for RC bridge piers reinforced with different types of SMAs. Based on an extensive numerical study, this study also proposes residual drift–based damage states for SMA-RC piers. Finally, an analytical expression is proposed to estimate the residual drift of SMA-reinforced concrete elements as a function of the expected maximum drift and superelastic strain of SMA. Comparison with experimental results revealed that the proposed equation could very well predict the residual drift obtained from the experimental results.
The induction of antibodies specific for the influenza HA protein stalk domain is being pursued as a universal strategy against influenza virus infections. However, little work has been done looking ...at natural or induced antigenic variability in this domain and the effects on viral fitness. We analyzed human H1 HA head and stalk domain sequences and found substantial variability in both, although variability was highest in the head region. Furthermore, using human immune sera from pandemic A/California/04/2009 immune subjects and mAbs specific for the stalk domain, viruses were selected in vitro containing mutations in both domains that partially contributed to immune evasion. Recombinant viruses encoding amino acid changes in the HA stalk domain replicated well in vitro, and viruses incorporating two of the stalk mutations retained pathogenicity in vivo. These findings demonstrate that the HA protein stalk domain can undergo limited drift under immune pressure and the viruses can retain fitness and virulence in vivo, findings which are important to consider in the context of vaccination targeting this domain.
The objective of the present paper is to propose a mathematical model for the frequency distribution of ice drift velocity. Measured data of the ice drift speed are employed as a basis for this ...model. The time series of ice drift were collected in the Beaufort Sea during the time interval 2006–2017. For this purpose, acoustic Doppler current profilers (ADCP) were applied. Wind is the main influencing factor for ice drifting in the oceans. The Nansen number, which typically describes the relationship between the wind speed and the ice drift speed as a percentage, is applied to quantify the degree of association. The frequency distribution of the ice drift velocity can accordingly be expected to be closely related to the downscaled wind turbulence spectrum. In the present study, the Fourier transforms of the time series of wind speed and ice drift speed are applied to investigate the properties of the frequency spectrum. The wind velocity has a strong influence on ice drift behavior, especially during the winter season. The Nansen number is found to be approximately 2.5 % within the study area. Accordingly, the Kaimal and Harris standard turbulence spectral density models can be adopted to represent the ice drift spectral density for the winter season. However, for the summer season, the ice drift spectral density exhibits a different decay in the high-frequency range. The proposed generalized mathematical model of the ice drift spectrum contains more parameters than the Kaimal and Harris turbulence spectral density models and is hence more flexible in fitting the ice drift behavior during both the winter and summer seasons. The proposed ice drift spectrum is accordingly found to provide an improved fitting of the empirical spectra estimated from the ADCP measurements compared to the Kaimal and Harris turbulence spectral density models.
•The downscaled wind spectrum is investigated and compared with the ice drift spectrum.•The Harris and Kaimal wind turbulence spectra fit the empirically estimated ice drift spectrum well for the winter season but less adequately for the summer season.•A generalized ice drift velocity spectrum is introduced to fit the empirical spectrum obtained from ADCP measurements for both seasons.•The statistical properties of the parameters of the proposed mathematical model are investigated based on measurement records from the Beaufort Sea.
Marine debris is one of the leading threats to the ocean and the Great East Japan Earthquake and tsunami on March 11, 2011 washed away an estimated 5million tons of debris in a single, tragic event. ...Here we used shoreline surveys, disaster debris reports and ocean drift models to investigate the temporal and spatial trends in the arrival of tsunami marine debris. The increase in debris influx to surveyed North American and Hawaiian shorelines was substantial and significant, representing a 10 time increase over the baseline in northern Washington State where a long term dataset was available. The tsunami event brought different types of debris along the coast, with high-windage items dominant in Alaska and British Columbia and large, medium-windage items in Washington State and Oregon. Recorded cumulative debris landings to North America were close to 100,000 items in the four year study period. The temporal peaks in measured shoreline debris and debris reports match the ocean drift model solutions. Mitigation and monitoring activities, such as shoreline surveys, provide crucial data and monitoring for potential impacts should be continued in the future.
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•The influx of marine debris after the tsunami event was 10 times higher than baseline.•Debris influx differed by coastline, with higher-windage debris in higher latitudes.•Recorded cumulative debris landings to North America was close to 100,000 items in four years.•Peaks in measured debris landings align with ocean drift model solutions.
The ability to capture joint kinematics in outside-laboratory environments is clinically relevant. In order to estimate kinematics, inertial measurement units can be attached to body segments and ...their absolute orientations can be estimated. However, the heading part of such orientation estimates is known to drift over time, resulting in drifting joint kinematics. This study proposes a novel joint kinematic estimation method that tightly incorporates the connection between adjacent segments within a sensor fusion algorithm, to obtain drift-free joint kinematics. Drift in the joint kinematics is eliminated solely by utilizing common information in the accelerometer and gyroscope measurements of sensors placed on connecting segments. Both an optimization-based smoothing and a filtering approach were implemented. Validity was assessed on a robotic manipulator under varying measurement durations and movement excitations. Standard deviations of the estimated relative sensor orientations were below 0.89° in an optimization-based smoothing implementation for all robot trials. The filtering implementation yielded similar results after convergence. The method is proven to be applicable in biomechanics, with a prolonged gait trial of 7 minutes on 11 healthy subjects. Three-dimensional knee joint angles were estimated, with mean RMS errors of 2.14°, 1.85°, 3.66° in an optimization-based smoothing implementation and mean RMS errors of 3.08°, 2.42°, 4.47° in a filtering implementation, with respect to a golden standard optical motion capture reference system.
Understanding the mechanisms controlling community diversity, functions, succession, and biogeography is a central, but poorly understood, topic in ecology, particularly in microbial ecology. ...Although stochastic processes are believed to play nonnegligible roles in shaping community structure, their importance relative to deterministic processes is hotly debated. The importance of ecological stochasticity in shaping microbial community structure is far less appreciated. Some of the main reasons for such heavy debates are the difficulty in defining stochasticity and the diverse methods used for delineating stochasticity. Here, we provide a critical review and synthesis of data from the most recent studies on stochastic community assembly in microbial ecology. We then describe both stochastic and deterministic components embedded in various ecological processes, including selection, dispersal, diversification, and drift. We also describe different approaches for inferring stochasticity from observational diversity patterns and highlight experimental approaches for delineating ecological stochasticity in microbial communities. In addition, we highlight research challenges, gaps, and future directions for microbial community assembly research.
Number of connected devices is steadily increasing and this trend is expected to continue in the near future. Connected devices continuously generate data streams and the data streams may often be ...high dimensional and contain concept drift. Clustering is one of the most suitable methods for real‐time data stream processing, since clustering can be applied with less prior information about the data. Also, data embedding makes the visualization of high dimensional data possible and may simplify clustering process. There exist several data stream clustering algorithms in the literature; however, no data stream embedding method exists. Uniform Manifold Approximation and Projection (UMAP) is a data embedding algorithm that is suitable to be applied on stationary (stable) data streams, though it cannot adapt concept drift. In this study, we describe a novel method EmCStream, to apply UMAP on evolving (nonstationary) data streams, to detect and adapt concept drift and to cluster embedded data instances using a distance or partitioning‐based clustering algorithm. We have evaluated EmCStream against the state‐of‐the‐art stream clustering algorithms using both synthetic and real data streams containing concept drift. EmCStream outperforms DenStream and CluStream, in terms of clustering quality, on both synthetic and real evolving data streams. Datasets and code of this study are available online at
https://gitlab.com/alaettinzubaroglu/emcstream.
Abstract
Dust growth and its associated dynamics play key roles in the first phase of planet formation in young stellar objects. Observations have detected signs of dust growth in very young ...protoplanetary disks. Furthermore, signs of planet formation, gaps in the disk at a distance of several tens of au from the central protostar, are also reported. From a theoretical point of view, however, planet formation in the outer regions is difficult due to the rapid inward drift of dust, called the radial drift barrier. Here, on the basis of three-dimensional magnetohydrodynamical simulations of disk evolution with dust growth, we propose a mechanism called the “ashfall” phenomenon, induced by a powerful molecular outflow driven by a magnetic field that may circumvent the radial drift barrier. We find that the large dust that grows to a size of about a centimeter in the inner region of a disk is entrained by an outflow from the disk. Then, large dust decoupled from gas is ejected from the outflow due to centrifugal force, enriching the grown dust in the envelope and eventually falls onto the outer edge of the disk. The overall process is similar to the behavior of ashfall from volcanic eruptions. In the ashfall phenomenon, the Stokes number of dust increases by reaccreting to the less dense disk outer edge. This may allow the dust grains to overcome the radial drift barrier. Consequently, the ashfall phenomenon can provide a crucial assist for making the formation of the planetesimals in outer regions of the disk possible, and hence the formation of wide-orbit planets and gaps.
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