Stationary Portions Research Articles

Effect of geogrid reinforcement on the load transfer in pile-supported embankment under cyclic loading

This paper investigated effects of geogrid reinforcement on the load transfer in pile-supported embankment under cyclic loading using self-moving trapdoor tests. In the self-moving trapdoor test setup, the trapdoor between two stationary portions (which were equivalent to the piles) was supported by compression springs to simulate the subsoil. Quartz sand and a biaxial geogrid were used as the test fill and reinforcement material, respectively. Tests results show that soil arching above the geogrid reinforcement and load transfer to the stationary portions (caused by the soil arching and tensioned membrane effect) experienced a process of “relatively enhancing - relatively degrading” with an increase in the number of cycles and maintained similar degrees within each complete cycle of cyclic loading. Moreover, the inclusion of geogrid reinforcement reduced the mobilization of soil arching, but increased the degree of load transfer to the stationary portions. In addition, cyclic loading with a higher frequency tended to mobilize more soil arching and induce a higher degree of load transfer to stationary portions. Also observed was that a higher frequency cyclic loading tended to decelerate the degradation of load transfer to stationary portions and caused less surface settlement, which indicating increased load-carrying capacity of pile-supported embankment.

Fatigue assessment of non-stationary random loading in the frequency domain by a quasi-stationary Gaussian approximation

The power spectral density (PSD) is a fundamental technique of random vibration fatigue providing an effective statistical characterization that can be processed by linear systems theory and load spectrum estimators. This lays the basis for a statistical-based fatigue assessment. While the PSD assembles a full stochastic characterization of stationary Gaussian loading, for loading subjected to changing operational, environmental, and excitational conditions, it provides no means of a fluctuating spectral density. Therefore, the PSD neither qualifies to characterize varying loads, nor reproduces comparable stress amplitudes to a referencing non-stationary excitation following a statistical-based stress analysis. Consequently, this paper employs the non-stationarity matrix to characterize the varying evolution of realistic loading and proposes a system of equations that decomposes this characterization into stationary Gaussian portions. The fundamental idea is to approximate realistic loading by abstracting a series of stationary segments, whose assembly in return embodies a full statistical characterization. The resulting quasi-stationary load definition better reflects the fatigue damage potential of realistic, non-stationary loading and allows to implement load spectrum estimators, ensuing computationally efficient and statistically robust structural lifetime predictions. Further, quasi-stationary load definitions are utilized to advance the concept of damage-equivalent statistical load definitions to be independent of a specific Miner exponent.

Dynamics-inspired feature extraction in semiconductor manufacturing processes

Abstract The ability to exploit data-driven process control and decision making frameworks is rapidly becoming critical to success in semiconductor manufacturing. At the same time, advances in manufacturing equipment sensors has seen dramatic increases in sampling rates in recent years, which has led to the ability to capture transients effects in signals with higher fidelity than previously possible. It is known that data-driven process control and decision making methodologies rely on the process of extraction of useful information from raw data signals. To that end, the current manuscript presents a novel methodology for extraction of information from data in the form of a feature set that faithfully and reliably depicts both the transient and stationary portions of the signals. The solution proposed is an automated dynamics-inspired approach that looks to segment a signal into steady state and transient components before summarizing each segment into a set of relevant signatures. The steady state segments are summarized through a set of statistics and each transient is reduced to a set of parameters relating to the underlying system dynamics, such as settling time, rise time, overshoots, etc. The impactful novel information content of the resulting dynamics-inspired feature set is evaluated by application to chamber matching, product defect level prediction and product quality characteristic prediction in etch and deposition processes executed in various tools across several modern 300 mm fabs.

Expanding the traditional definition of molt-migration

ABSTRACT The occurrence of molt during migration, known as “molt-migration,” has increasingly received attention across many avian taxa since first being described in waterfowl in the 1960s. However, despite the many different types of molt stages and strategies, most, if not all, uses of the term “molt-migration” apply to the definitive prebasic molt of flight feathers in post-breeding adults, whereas fewer studies address migration for body-feather molts. Here, we argue that the current definition of molt-migration, as applied, is limited in focus relative to the diverse ways in which it can manifest in avian populations. We suggest a new, broader definition of molt-migration and highlight examples of molt-migration as traditionally defined, and the many examples that have not been defined as such. We propose a new, 2-tiered typology for defining different forms of molt-migration, based on (1) its progression relative to stationary portions of the annual cycle, and (2) the stage of molt involved. In ord...

Adaptive reinforcement learning with active state-specific exploration for engagement maximization during simulated child-robot interaction

AbstractUsing assistive robots for educational applications requires robots to be able to adapt their behavior specifically for each child with whom they interact.Among relevant signals, non-verbal cues such as the child’s gaze can provide the robot with important information about the child’s current engagement in the task, and whether the robot should continue its current behavior or not. Here we propose a reinforcement learning algorithm extended with active state-specific exploration and show its applicability to child engagement maximization as well as more classical tasks such as maze navigation. We first demonstrate its adaptive nature on a continuous maze problem as an enhancement of the classic grid world. There, parameterized actions enable the agent to learn single moves until the end of a corridor, similarly to “options” but without explicit hierarchical representations.We then apply the algorithm to a series of simulated scenarios, such as an extended Tower of Hanoi where the robot should find the appropriate speed of movement for the interacting child, and to a pointing task where the robot should find the child-specific appropriate level of expressivity of action. We show that the algorithm enables to cope with both global and local non-stationarities in the state space while preserving a stable behavior in other stationary portions of the state space. Altogether, these results suggest a promising way to enable robot learning based on non-verbal cues and the high degree of non-stationarities that can occur during interaction with children.

Turbulence Resolving Flow Simulations of a Francis Turbine in Part Load using Highly Parallel CFD Simulations

The operation of Francis turbines in part load conditions causes high fluctuations and dynamic loads in the turbine and especially in the draft tube. At the hub of the runner outlet a rotating vortex rope within a low pressure zone arises and propagates into the draft tube cone. The investigated part load operating point is at about 72% discharge of best efficiency. To reduce the possible influence of boundary conditions on the solution, a flow simulation of a complete Francis turbine is conducted consisting of spiral case, stay and guide vanes, runner and draft tube. As the flow has a strong swirling component for the chosen operating point, it is very challenging to accurately predict the flow and in particular the flow losses in the diffusor. The goal of this study is to reach significantly better numerical prediction of this flow type. This is achieved by an improved resolution of small turbulent structures. Therefore, the Scale Adaptive Simulation SAS-SST turbulence model - a scale resolving turbulence model - is applied and compared to the widely used RANS-SST turbulence model. The largest mesh contains 300 million elements, which achieves LES-like resolution throughout much of the computational domain. The simulations are evaluated in terms of the hydraulic losses in the machine, evaluation of the velocity field, pressure oscillations in the draft tube and visual comparisons of turbulent flow structures. A pre-release version of ANSYS CFX 17.0 is used in this paper, as this CFD solver has a parallel performance up to several thousands of cores for this application which includes a transient rotor-stator interface to support the relative motion between the runner and the stationary portions of the water turbine.

Fatigue assessment of non-stationary random vibrations by using decomposition in Gaussian portions

This paper presents a method for determining the decomposition of a non-stationary, random vibration with a non-Gaussian distribution into several stationary portions with Gaussian distributions. The fatigue load of the initial non-stationary signal, and the summarized fatigue loads of the derived Gaussian portions are identical in both a direct comparison and in a comparison of the vibration responses caused by these signals on an arbitrary linear dynamical system. As stationary Gaussian signals can be described by power spectral densities (PSD), the analysis of the dynamical response with its corresponding fatigue load can be switched from time domain to frequency domain with an enormous performance gain regarding numerical computations. Especially, a combination of a realistic non-stationary signal with a large duration (from measurements), together with huge structural dynamics models is hard to analyze numerically in time domain because of enormous computation times. The proposed PSD-based method enables a very efficient numerical analysis in frequency domain. For the estimation of load spectra in frequency domain, well established PSD-based methods can be used, corresponding to Rainflow counting in time domain. This paper gives a detailed introduction to the procedure outlined with associated equations necessary for a numerical solution. The correct modeling of the fatigue damage load is proven by applying the fatigue damage spectrum concept.

Respiratory Sounds Compression

Recently, with the advances in digital signal processing, compression of biomedical signals has received great attention for telemedicine applications. In this paper, an adaptive transform coding-based method for compression of respiratory and swallowing sounds is proposed. Using special characteristics of respiratory sounds, the recorded signals are divided into stationary and nonstationary portions, and two different bit allocation methods (BAMs) are designed for each portion. The method was applied to the data of 12 subjects and its performance in terms of overall signal-to-noise ratio (SNR) values was calculated at different bit rates. The performance of different quantizers was also considered and the sensitivity of the quantizers to initial conditions has been alleviated. In addition, the fuzzy clustering method was examined for classifying the signal into different numbers of clusters and investigating the performance of the adaptive BAM with increasing the number of classes. Furthermore, the effects of assigning different numbers of bits for encoding stationary and nonstationary portions of the signal were studied. The adaptive BAM with variable number of bits was found to improve the SNR values of the fixed BAM by 5 dB. Last, the possibility of removing the training part for finding the parameters of adaptive BAMs for each individual was investigated. The results indicate that it is possible to use a predefined set of BAMs for all subjects and remove the training part completely. Moreover, the method is fast enough to be implemented for real-time application.

Perception of suprathreshold amplitude modulation and intensity increments: Weber’s law revisited

The perceived strength of intensity fluctuations evoked by suprathreshold sinusoidal amplitude modulation (AM) and the perceived size of intensity increments were compared across levels of a wideband noise and a 1-kHz tone. For the 1-kHz tone, the comparisons were made in quiet and in a high-pass noise. The data indicate that suprathreshold modulation depths and intensity increments, perceived as equivalent across levels, follow a pattern resembling Weber's law for noise and the "near miss" to Weber's law for a tone. The effect of a high-pass noise was largely consistent with that observed for AM and increment detection. The data suggest that Weber's law is not a direct consequence of the dependence of internal noise on stimulus level, as suggested by multiplicative internal noise models. Equal loudness ratios and equal loudness differences (computed using loudness for the stationary portions before and after the increment) accounted for the increment-matching data for noise and for the tone, respectively, but neither measure predicted the results for both types of stimuli. Predictions based on log-transformed excitation patterns and predictions using an equal number of intensity just-noticeable differences were in qualitative, but not quantitative, agreement with the data.

Bi-objective facility expansion and relayout considering monuments

In this paper, the unequal area facility expansion and relayout problem is studied. The facility relayout problem is important since both manufacturing and service entities must modify their layouts over time when their operational characteristics change. A bi-objective approach is proposed to solve the relayout problem for cases of both a fixed facility area and an expanded facility area. Material handling costs and relayout costs are minimized using a tabu search meta-heuristic optimizer. This heuristic randomly alternates the objective function between the two objectives of the problem in each step and, by doing so, eliminates the difficulty of weighting and scaling the two objectives. The approach is flexible in handling various aspects of the problem such as stationary portions of departments (i.e., monuments), addition of new departments, and changes in existing department and facility areas. Computational experiments show that the bi-objective tabu search approach is effective and tractable. The use of the Pareto front of designs is demonstrated by showing a few approaches to analyzing the trade-offs between initial costs (relayout cost) and ongoing expenses (material handling costs).

Compression of Patient Monitoring Video Using Motion Segmentation Technique

The volume of patient monitoring video acquired in hospitals is very huge and hence there is a need for better compression of the same for effective storage and transmission. This paper presents a new motion segmentation technique, which improves the compression of patient monitoring video. The proposed motion segmentation technique makes use of a binary mask, which is obtained by thresholding the standard deviation values of the pixels along the temporal axis. Two compression methods, which make use of the proposed motion segmentation technique, are presented. The first method uses MPEG-4 coder and 9/7-biorthogonal wavelet for compressing the moving and stationary portions of the video respectively. The second method uses 5/3-biorthogonal wavelet for compressing both the moving and the stationary portions of the video. The performances of these compression algorithms are evaluated in terms of PSNR and bitrate. From the experimental results, it is found that the proposed motion technique improves the performance of the MPEG-4 coder. Among the two compression methods presented, the MPEG-4 based method performs better for bitrates less than 767 Kbps whereas for bitrates above 767 Kbps the performance of the wavelet based method is found superior.

Three-dimensional free-radical copolymerization of methyl methacrylate with diunsaturated monomers in the presence of an aromatic polyimide

The three-dimensional free-radical copolymerization of MMA with diunsaturated comonomers of various natures in the absence and in the presence of 4 wt % aromatic polyimide (ηinh = 0.38−1.02 dl/g) has been studied by isothermal calorimetry. It has been shown that, depending on the chemical nature of spacers separating double bonds of the comonomers, the kinetic curves of copolymerization may be divided into two groups, one of which is characterized by an almost complete absence of stationary portions. It has been demonstrated that the effects of the polyimide on the initial rate of copolymerization and on the parameters of the gel effect depend on the nature of diunsaturated comonomers and the molecular mass of the aromatic polyimide. The swelling of the polymer systems under study in toluene has been investigated, and the parameters of their network structure have been estimated. The irreversible flow deformation of the MMA copolymers with diunsaturated comonomers does not manifest itself up to a temperature corresponding to the onset of degradation of the copolymers. The incorporation of polyimide units improves the thermal stability of the copolymers.

On the efficiency of classical RASTA filtering for continuous speech recognition: Keeping the balance between acoustic pre-processing and acoustic modelling

The efficiency of classical RASTA filtering for channel normalisation was investigated for continuous speech recognition based on context-independent and context-dependent hidden Markov models. For a medium and a large vocabulary continuous speech recognition task, recognition performance was established for classical RASTA filtering and compared to using no channel normalisation, cepstrum mean normalisation, and phase-corrected RASTA. Phase-corrected RASTA is a technique that consists of classical RASTA filtering followed by a phase correction operation. In this manner, channel bias is as effectively removed as with classical RASTA. However, for phase-corrected RASTA, amplitude drift towards zero in stationary signal portions is diminished compared to classical RASTA. The results show that application of classical RASTA filtering resulted in decreased recognition performance when compared to using no channel normalisation for all conditions studied, although the decrease appeared to be smaller for context-dependent models than for context-independent models. However, for all conditions, recognition performance was significantly and substantially improved when phase-corrected RASTA was used and reached the same performance level as obtained for cepstrum mean normalisation in some cases. It is concluded that classical RASTA filtering can only be effective for channel robustness, if the impact of the amplitude drift towards zero can be kept as limited as possible.

Motions caused by the growth of Bacillus subtilis macrofibres in fluid medium result in new forms of movement of the multicellular structures over solid surfaces.

Bacillus subtilis macrofibres, highly ordered multicellular structures, undergo twisting and writhing motions when they grow in fluid medium as a result of forces generated by the elongation of individual cells. Macrofibres are denser than the fluid medium in which they are cultured, consequently they settle to the bottom of the growth chamber and grow in contact with it. The ramifications of growth on plastic and glass surfaces were examined. Macrofibres were observed to rotate about a vertical axis near the centre of their length in a chiral-specific direction. Right-handed fibres rotated clockwise on plastic surfaces at approximately 4 degrees min(-1), left-handed structures of lower twist rotate anti-clockwise at about half that rate. Very large ball structures produced late in macrofibre formation perched on many small protruding fibres but rotated only when driven by large fibres attached to their periphery. Closer examination showed that fibres made contact with surfaces at only a few points along their length (between 1 and 6 on glass). The regions in contact with the surface changed periodically as a result of rotation of the fibre shaft caused by growth. Every time the weight of a fibre transferred from one contact point to another, each section of the fibre took a small step approximately proportional to its distance from the fibre mid-point. The net result was a rolling of each section over the surface so that the fibre rotation about a vertical axis was produced. Macrofibres also took large steps when part of the structure rose off the floor, swept through an arc in the fluid and then returned to the floor at a new location. The rate of movement during a large step, measured as the change of angle between the moving and stationary portions of the fibre, was 5 degrees s(-1). These observations reveal that the forces derived from helical growth that lead to macrofibre formation also cause characteristic macrofibre motion that differs from classical motility.

New three-phase model for micellar liquid chromatography

The amount of sodium dodecyl sulfate (SDS) adsorbed on a reversed-phase octadecylsilica (ODS) stationary phase in micellar liquid chromatographic (MLC) separation has been measured. It was found that the weight percentage of SDS on the stationary phase (16.5%) was similar to the percentage ratio of C/Si (C/Si = 17.1%) of the original ODS stationary phase. This indicated that the octadecyl groups of the ODS packing were largely covered by adsorbed surfactants and the stationary phase in the MLC system could be considered to be the adsorbed surfactant. Accordingly, a new three-phase equilibrium model in which the adsorbed surfactant was assumed to be the stationary phase was proposed to illustrate the behaviour of analyte partitioning in MLC. The negative impact of the adsorbed surfactant on the efficiency of MLC was discussed in terms of this new model. With the three-phase model, the equilibrium constant (K3) for direct transfer of the analyte from the surfactant in the mobile phase to the surfactant on the stationary phase could be calculated. The results obtained for K3 using two model analytes showed that the mobile phase and stationary phase portions of the surfactant in MLC had similar but not identical abilities for binding the analyte. The effects and limitations of the use of organic modifiers in MLC are also discussed.

A statistical feedforward/fedback buffer control for the transmission of digital video signals compressed by DCT-based intrafield coding

A new buffer-control policy for intrafield coding of video signals is presented. This method employs two statistical bit rate predictors-feedback and feedforward. It uses a feedback predictor in stationary portions of an image sequence and a feedforward predictor at scene changes. It is shown that this buffer-control policy is reasonably simple to implement and can effectively control output bit rate even at scene changes.

Microscopic mapping of subnanometric motion

The sensitivity of a microscope-based holographic system designed for mapping the motion of components of a living cell is calibrated by means of a simple procedure. Bubbles of air are allowed to drift with known velocity in a nearly horizontal, glycerine-filled capillary observed through the microscope. The ultrafine motion of the bubbles is captured interferometrically by subtractive superposition of a pair of holograms recorded a few milliseconds apart. Stationary portions of the field of view are rendered dimly in images reconstructed from the interferogram, while the brightness of moving portions varies monotonically with their displacement. Displacements as small as 1.1 nm were betrayed in the images. Analysis of the experimental conditions suggests that bubble displacements as small as 0.7 nm will become detectable once minor improvements are made in the apparatus.

The perception of plosive consonants by hearing‐impaired listeners

The reduced speech perception by hearing‐impaired subjects has often been studied. In order to investigate the role of coarticulation we did some experiments on a group of 20 hearing‐impaired and 10 normal‐hearing subjects. From 45 embedded CVCVC words we deleted either the plosive bursts, or the vocalic CV or VC transitions, or the stationary vowel portions, or any combination of these four. The listeners were asked to identify the three plosive consonants in the resulting stimuli. The results for the normal‐hearing subjects agree with results of Schouten and Pols [Proc. 10th ICPS, Utrecht (1983), p. 464]: identification is affected more by deletion of plosive bursts than of vocalic transitions, and in medial consonants the CV transition contains more information about the consonant than does the VC transition. For the hearing‐impaired listeners the vocalic transitions play a more important role: identification with the plosive bursts only results in guessing; in contrast with the results for the normal‐hearing subjects more errors occur for the final consonant than for the initial or the medial consonant. We also found some relations with other auditory functions measured. [Work supported by ZWO.]

A Quantitative Model for the Adhesive Locomotion of The Terrestrial Slug, Ariolimax Columbianus

ABSTRACT The foot of pulmonate gastropods adheres to the surface upon which the animal crawls, the adhesive being a thin layer of pedal mucus. The power for locomotion in these animals is provided by rhythmic muscular contractions (pedal waves) on the ventral surface of the foot, and the force due to these waves is coupled to the substratum by the pedal mucus. Movement of the animal is consequently a result of a balance of forces: if the reactive force provided by the adhesive beneath the stationary portions of the foot is sufficient to offset the frictional force caused by portions of the foot moving forward, the animal is able to crawl. Mechanisms previously proposed to explain this adhesive crawling require that the frictional resistance to forward movement be minimized by the foot being lifted during the passage of a pedal wave. This lifting, however, cannot be reconciled with the properties of the pedal mucus and epithelium, and the terrestrial slug, Ariolimax columbianus, is shown to not lift its foot when crawling. A new mechanism is proposed which does not require lifting of the foot and explains several difficulties inherent in previous studies. Based on this mechanism and the mechanical properties of pedal mucus, a quantitative model is constructed which predicts the frictional and reactive forces, and these predictions are tested against force measurements made under crawling slugs. The model accurately predicts the magnitude of forces under slugs crawling horizontally, but is less accurate in predicting forces under slugs crawling vertically.

Tranformation of long reticulofugal spike trains by interneurons connected monosynaptically with the reticulospinal tract

Characteristics of transmission of activity evoked by stimulation of the reticular formation through interneurons located in the ventromedial zones of the gray matter of the lumbar division of the spinal cord and connected monosynaptically with reticulospinal fibers were investigated in cats. Responses of the neurons to relatively low-frequency (not exceeding 80–100/sec) stimulation consisted mainly of stationary discharges; with a further increase in frequency the response became nonstationary (the initial, relatively high-frequency discharge was followed by partial or complete suppression of the discharge). The maximal frequency of the initial phase of the response to high (over 400/sec) frequencies of stimulation was 180–230 spikes/sec. The "transmission factor" (ratio between the frequency of spikes in the response to the frequency of stimulation), calculated for stationary discharges, reached 0.7–0.8 at low frequencies of stimulation, and then decreased significantly. On the basis of the statistical characteristics of the stationary portions of the evoked activity and analysis of these data by the use of a mathematical model, indirect estimates were obtained of the parameters of processes lying at the basis of the transforming properties of this cell population.