Homogenization of the wave equation with non-uniformly oscillating coefficients

The focus of our work is a dispersive, second-order effective model describing the low-frequency wave motion in heterogeneous (e.g., functionally graded) media endowed with periodic microstructure. For this class of quasi-periodic medium variations, we pursue homogenization of the scalar wave equation in [Formula: see text], [Formula: see text], within the framework of multiple scales expansion. When either [Formula: see text] or [Formula: see text], this model problem bears direct relevance to the description of (anti-plane) shear waves in elastic solids. By adopting the lengthscale of microscopic medium fluctuations as the perturbation parameter, we synthesize the germane low-frequency behavior via a fourth-order differential equation (with smoothly varying coefficients) governing the mean wave motion in the medium, where the effect of microscopic heterogeneities is upscaled by way of the so-called cell functions. In an effort to demonstrate the relevance of our analysis toward solving boundary value problems (deemed to be the ultimate goal of most homogenization studies), we also develop effective boundary conditions, up to the second order of asymptotic approximation, applicable to one-dimensional (1D) shear wave motion in a macroscopically heterogeneous solid with periodic microstructure. We illustrate the analysis numerically in one dimension by considering (i) low-frequency wave dispersion, (ii) mean-field homogenized description of the shear waves propagating in a finite domain, and (iii) full-field homogenized description thereof. In contrast to (i) where the overall wave dispersion appears to be fairly well described by the leading-order model, the results in (ii) and (iii) demonstrate the critical role that higher-order corrections may have in approximating the actual waveforms in quasi-periodic media.

Forecasting the Demand of Honey Product for Facing Panic Buying and Stockpile in Pandemics

The threat on health sector has massive impacts, and one of them is on business internal management as the main factor of producers to consider design of their products. During pandemic, honey is categorized as food supplement. In a certain phase, when the demand upon honey is high, the price tends to be unstable due to an imbalance between supply and demand. Complexities of consumer during pandemics effect on food security system. Unpreparedness of the producers in facing the phenomenon of panic buying and stockpile causes scarcity. Objective of the research was forecasting the demand of honey following the second pandemic wave and supported SMEs to create adaptive strategy to face scarcity. Method of the research used secondary data and survey in the field, which was ended by FGD to decide strategy of the producer to minimize scarcity. Data analysis used MSE (Mean Squared Error) with exponential smoothing. Results of the research showed that the method of alpha exponential 5% has minimum error, which forecast that in December 2021, the demand of propolis honey may reduce after the 2nd wave of Covid in Indonesia and approach to normal forecasting system. The accuracy with exponential method is higher and may facilitate the producers to provide products when fear contagion and panic buying take place. Contribution of analysis result toward strategy of the producers is providing estimation that maximum amount of availability increases no more than 2 times of the real demand of the consumers when panic buying occurs. The most needed strategy is setting the timeline in the projection of consumer journey. This alternative is relevant to fear contagion phenomenon because it contributes to socio-psychology of the consumers in deciding to buy supplement of honey product. Novelty of this research is examining the frequency wave of product purchase intensity of the consumer journey with Covid-19 phenomenon.

Ultra Low Frequency Wave Produced by Underwater Oscillating Sphere and Its Measurement

When an underwater target moves in viscous fluid, it may cause the periodic movement of the surrounding fluid and generate ultra-low-frequency (ULF) gravity waves. The initial domain of the gravitational surface wave propagating above the moving target is named circular wave. This article studies the ULF circular wave generated by underwater oscillating sphere, which will provide basis for underwater long-range target detection. Firstly, the circular wave caused by the sphere oscillation in a finite deep fluid is studied based on the theory of linear potential flow. Meanwhile, the multipole expansion theory is established to solve the circular wave field. Secondly, the interface wave generated by the target oscillation in a two-layer fluid are numerically analyzed by comparison with the free surface fluctuation of a single-layer fluid. The results show that the amplitude of the internal interface displacement (AIID) is smaller than that of the free surface (AFSD). When the sphere is in the lower layer, the layering effect of the fluid has significant influences on the AFSD. Finally, the results of the pool experiment verified that the wave generated by the oscillating sphere is the surface gravity wave. Furthermore, the change trend of the test result is consistent with the simulation result.

Noninvasive detection of elevated ICP using spontaneous tympanic membrane pulsation

Neurological conditions such as traumatic brain injury (TBI) and hydrocephalus may lead to intracranial pressure (ICP) elevation. Current diagnosis methods rely on direct pressure measurement, while CT, MRI and other expensive imaging may be used. However, these invasive or expensive testing methods are often delayed because symptoms of elevated ICP are non-specific. Invasive methods, such as intraventricular catheter, subdural screw, epidural sensor, lumbar puncture, are associated with an increased risk of infection and hemorrhage. On the other hand, noninvasive, low-cost, accurate methods of ICP monitoring can help avoid risks and reduce costs while expediting diagnosis and treatment. The current study proposes and evaluates a novel method for noninvasive ICP monitoring using tympanic membrane pulsation (TMp). These signals are believed to be transmitted from ICP to the auditory system through the cochlear aqueduct. Fifteen healthy subjects were recruited and TMp signals were acquired noninvasively while the subjects performed maneuvers that are known to change ICP. A custom made system utilizing a stethoscope headset and a pressure transducer was used to perform these measurements. Maneuvers included head-up-tilt, head-down-tilt and hyperventilation. When elevated ICP was induced, significant TMp waveform morphological changes were observed in each subject (p < 0.01). These changes include certain waveform slopes and high frequency wave features. The observed changes were reversed by the maneuvers that decreased ICP (p < .01). The study results suggest that TMp waveform measurement and analysis may offer an inexpensive, noninvasive, accurate tool for detection and monitoring of ICP elevations. Further studies are warranted to validate this technique in patients with pathologically elevated ICP.

OC6 Phase Ib: Floating Wind Component Experiment for Difference-Frequency Hydrodynamic Load Validation

A new validation campaign was conducted at the W2 Harold Alfond Ocean Engineering Laboratory at the University of Maine to investigate the hydrodynamic loading on floating offshore wind substructures, with a focus on the low-frequency contributions that tend to drive extreme and fatigue loading in semisubmersible designs. A component-level approach was taken to examine the hydrodynamic loads on individual parts of the semisubmersible in isolation and then in the presence of other members to assess the change in hydrodynamic loading. A variety of wave conditions were investigated, including bichromatic waves, to provide a direct assessment of difference-frequency wave loading. An assessment of the impact of wave uncertainty on the loading was performed, with the goal of enabling validation with this dataset of numerical models with different levels of fidelity. The dataset is openly available for public use and can be downloaded from the U.S. Department of Energy Data Archive and Portal.