Height Amplitude Research Articles

Studies on the free vibrations of tether of submerged floating tunnel involving tube motion by using different mechanical models

To accurately acquire the frequency/mode of the tethers of the tether-type submerged floating tunnel (SFT), which is an innovative underwater traffic structure with great potential, the dynamic frequency (DF) and wet mode (WM) of the tether involving the tube motion are studied. The novelty lies on the proposed novel method where the analytical relation of the tether’s DF and WM with the moving boundaries and the structural parameters is directly built. The gap that the unreported premise of quasi-static treatment for the global vibratory SFT and the unmentioned principle of the top tension of the tether equaling the net buoyancy within its supporting range is filled. Firstly, four mechanical models named M1∼M4 are respectively established by equating the tether as a beam or string with moving boundaries, taking into accounts the bending stiffness, wet-weight and other geometrical/material factors. Secondly, the relationships between the band-width, upper/lower limits of the DF and the inclination angle, vertical height, buoyancy-weight-ratio (BWR), motion amplitude are founded. Thirdly, the distribution laws of the DF during the vertical periodic motion of tube, as well as the parameter sensitivity range of the WM to the span-wise effect of wet-weight and the vertical height, are studied. The results show that the tether exhibits DF under the tube motion. The band-width of DF is sensitive to the BWR, inclination angle, vertical height and motion amplitude, and its upper/lower limits exhibit varying degrees of variation patterns with the changing of these parameters. The wet-weight and the vertical height are two main influencing factors of the WM. The proposed method provides a new treatment idea for further in-depth research on the locking zone of the vortex-induced vibration (VIV) and parametric vibration for the tether of SFT.

Biogeographic Patterns in Density, Recruitment, Body Size and Zonation of Rocky Intertidal Predators Suggest Increased Population Vulnerability Near Southern Range Limits

ABSTRACTAimSurveying the demography of populations near species range edges may indicate their vulnerability to range contractions or local extinction as the climate changes. In the rocky intertidal, not only are latitudinal ranges constricted by thermal stress, but tides also create zonation or a ‘vertical range’ driven by sharp environmental gradients. By investigating demographics along the latitudinal and vertical ranges simultaneously, we can investigate whether populations may be vulnerable to a changing climate.LocationRocky intertidal habitats along west coast of the United States.TaxaOchre sea star Pisaster ochraceus, six‐armed sea star Leptasterias spp., emarginate whelks (Nucella ostrina and N. emarginata) and channeled whelk N. canaliculata.MethodsIn 2018, we surveyed the demographics of the taxa above at 33 sites spanning > 11° latitude from central Oregon to southern California, near the southern range limits of each taxon. We counted and sized individuals from the high to low intertidal zone. To understand how environmental stress changed with latitude, we evaluated intertidal temperatures in situ, as well as tidal extremes, tidal amplitude and wave exposure using offshore buoys.ResultsFor all taxa, population density, the relative proportion of smaller individuals (except for emarginate whelks) and the upper vertical limits on the shore declined from north to south as temperatures increased and high tide height, tidal amplitude and wave heights decreased. In addition, smaller individual Leptasterias spp. generally inhabited lower shore levels while smaller individual emarginate whelks inhabited higher shore levels coastwide. For N. canaliculata, smaller animals were higher on shore northward, but lower on shore southward.Main ConclusionsWhile this study is a snapshot in time and cannot assess impacts of climate change, our surveys suggest environmentally‐related demographic limitation toward southern range limits and demographically vulnerable southern populations. Therefore, a warming climate may cause local extinctions or range contractions near southern limits.

Cooling characteristics of nanofluids in a snowflake and squid fin composite bionic microchannel heat sink

To improve the heat dissipation performance of electronic components, this study proposed a novel biomimetic microchannel design inspired by snowflakes and squid fins. A numerical simulation method was employed to investigate the cooling characteristics of nanofluids at different concentrations within this biomimetic microchannel heat sink. The microchannel is shaped like a snowflake, while the base plate features a biomimetic squid fin structure. The study focused on analyzing the effects of waveform height (amplitude A = 0.1–0.4 mm) and waveform frequency (B = 0.5–2π) on heat transfer performance. The results indicated that when nanofluids flow over a base plate with a wavelength frequency of B = 0.5π, there is a significant enhancement in heat exchange while simultaneously reducing flow resistance. In the microchannel heat sink (A = 0.3 mm, B = π), the thermal conductivity of the nanofluids can be increased by up to 32.56 %, with a maximum comprehensive evaluation index of 1.68. This research provides important guidance for the application of nanofluids and biomimetic microchannels in the thermal control of electronic devices.

Dynamic performance of ground supported circular water tank using shaking table

One of the most important lifelines for the human population is the water tank, which needs to be able to continue operating as usual both during and after earthquakes. Due to inadequate design techniques, structures are mainly intended to support static loads. The impact of dynamic loading is not taken into account. When resonance occurs, the effect is even more severe. The main objective of this work is to perform shaking table tests and study the dynamic performance of circular water tanks resting on the ground during shaking. For this investigation, three tanks with different height-to-diameter ratios have been taken into consideration. For various combinations of frequency, amplitude and water height in the tank, the hydrodynamic pressure at various places and the height of the sloshing wave during shaking have been measured experimentally. In comparison to the static water pressure on the container, it is discovered that dynamic pressure increases by 20%–50% during shaking. Resonant frequency drops with increasing tank diameter for a given water head at constant amplitudes.

A brief history of tsunamis in the Vanuatu Arc

Abstract. The archipelagos of Vanuatu and the eastern Solomon Islands, scattered over 1500 km along the Vanuatu Arc, include dozens of inhabited volcanic islands exposed to many natural hazards that impact their populations more or less severely. Due to the location of these islands on a subduction interface known as the Vanuatu subduction zone, tsunamis triggered by earthquakes, volcanic eruptions, and landslides locally, regionally, and in the far field represent a permanent threat. If catalogues already list tsunamis that have occurred in the Vanuatu Arc, they were not exclusively focusing on this region. This study goes further in the listing of tsunamis reported and/or recorded in the Vanuatu Arc, analysing existing catalogues, historical documents, and sea-level data from the five coastal tide gauges located in Vanuatu at Port Vila (Efate), Luganville (Espiritu Santo), Litzlitz (Malekula), and Lenakel (Tanna) and in the eastern Solomon Islands province at Lata (Ndende). It allows the identification of 100 tsunamis since 1863, 15 of them showing wave amplitude and/or run-up height of more than 1 m and 8 between 0.3 and 1 m. While some tsunamis are known to have occurred in the past, information about the wave amplitude or potential run-up is sometime lost (15 events). Also, tsunamis reported in neighbouring islands like New Caledonia but not reported or recorded in the Vanuatu Arc are discussed, as well as debated events or events with no known origin(s).

LightGBM hybrid model based DEM correction for forested areas.

The accuracy of digital elevation models (DEMs) in forested areas plays a crucial role in canopy height monitoring and ecological sensitivity analysis. Despite extensive research on DEMs in recent years, significant errors still exist in forested areas due to factors such as canopy occlusion, terrain complexity, and limited penetration, posing challenges for subsequent analyses based on DEMs. Therefore, a CNN-LightGBM hybrid model is proposed in this paper, with four different types of forests (tropical rainforest, coniferous forest, mixed coniferous and broad-leaved forest, and broad-leaved forest) selected as study sites to validate the performance of the hybrid model in correcting COP30DEM in different forest area DEMs. In the hybrid model of this paper, the choice was made to use the Densenet architecture of CNN models with LightGBM as the primary model. This choice is based on LightGBM's leaf-growth strategy and histogram linking methods, which are effective in reducing the data's memory footprint and utilising more of the data without sacrificing speed. The study uses elevation values from ICESat-2 as ground truth, covering several parameters including COP30DEM, canopy height, forest coverage, slope, terrain roughness and relief amplitude. To validate the superiority of the CNN-LightGBM hybrid model in DEMs correction compared to other models, a test of LightGBM model, CNN-SVR model, and SVR model is conducted within the same sample space. To prevent issues such as overfitting or underfitting during model training, although common meta-heuristic optimisation algorithms can alleviate these problems to a certain extent, they still have some shortcomings. To overcome these shortcomings, this paper cites an improved SSA search algorithm that incorporates the ingestion strategy of the FA algorithm to increase the diversity of solutions and global search capability, the Firefly Algorithm-based Sparrow Search Optimization Algorithm (FA-SSA algorithm) is introduced. By comparing multiple models and validating the data with an airborne LiDAR reference dataset, the results show that the R2 (R-Square) of the CNN-LightGBM model improves by more than 0.05 compared to the other models, and performs better in the experiments. The FA-SSA-CNN-LightGBM model has the highest accuracy, with an RMSE of 1.09 meters, and a reduction of more than 30% of the RMSE when compared to the LightGBM and other hybrid models. Compared to other forested area DEMs (such as FABDEM and GEDI), its accuracy is improved by more than 50%, and the performance is significantly better than other commonly used DEMs in forested areas, indicating the feasibility of this method in correcting elevation errors in forested area DEMs and its significant importance in advancing global topographic mapping.

Electroretinographic changes in the inner and outer retinal layers before and after intravenous chemotherapy for retinoblastoma.

To study the inner and outer retinal functions using a full-field electroretinogram (ERG) before and after intravenous chemotherapy (IVC) in children with retinoblastoma (RB). Of the 11 eyes, seven had RB and four were normal. All children were examined under anesthesia using a handheld ERG machine with a standard protocol - light-adapted single-flash ERG (fERG), photopic single-flash 3.0- and 30-Hz flickers, and photopic negative response (PhNR) amplitudes at 72 ms (P72). The amplitudes and peak times were compared before and after IVC. Post-chemotherapy tumor regressed in all seven eyes. Of the seven eyes, the fERG peak time (a-wave) was delayed in two eyes (29%), whereas the b-wave was delayed in six eyes (86%). The fERG amplitude height for a- and b-waves decreased in five eyes (71%) and six eyes (86%), respectively. In addition, photopic flicker 30-Hz b-wave peak time delayed in five eyes (71%), whereas the b-wave amplitude height decreased in six eyes (86%). Simultaneously, the P72 amplitude height decreased in six eyes (86%), whereas the P-ratio increased in all seven eyes (100%). In comparison, the ERG responses improved in three of the four contralateral normal eyes. Overall, the cone function improved in two eyes (29%), whereas cone bipolar cell and retinal ganglion cell (RGC) function improved in one eye (14%) each. Comparison of light-adapted ERG changes before and after IVC showed reduced amplitudes and delayed peak times for both a and b waveforms, as well as reduced PhNR amplitude attributable to bipolar and RGC injury.

Analyzing the impact of sinusoidal wavy rib geometric parameters on turbine blade thermal and fluid dynamics

The wavy rib is a spoiler structure designed to improve flow and heat transfer within turbine blade cooling channels, offering valuable insights for efficient cooling design in aerospace applications. This study employs a blend of experimental validation and detailed numerical simulations to investigate how rib height, amplitude, and discontinuity size collectively impact heat transfer enhancement and flow resistance in wavy ribs. By integrating TSP temperature field measurements with SST k-ω numerical calculations across 8 rib heights, 7 amplitudes, and 9 discontinuities at Reynolds numbers ranging from 10000 to 40000, the research reveals intricate relationships between these parameters. Studies have shown that there is a strong interaction between amplitude and rib height, as well as amplitude and discontinuity. Under small amplitude, Nu/Nu0 increases monotonously with the increase of rib height, but increases first and then decreases under large amplitude. When the discontinuity is small, the dimensionless Nusselt number (Nu/Nu0) of the ribbed wall increases first and then decreases with the increase of rib height, while it increases monotonously when the discontinuity is large. In contrast, the interaction between amplitude and discontinuity is weak. The ribbed wall with the greatest heat transfer improvement has Nu/Nu0 nearly 80 % higher than the reference wavy rib scheme, but it also has the highest corresponding pressure loss. The best overall thermal performance is 20 % higher than the reference structure, and the ribbed wall Nu/Nu0 is also increased by 24 %. The change of Reynolds number at the inlet of the channel has little effect on the wall Nu/Nu0 and pressure loss of the wavy rib channel.

Anisotropic charge transport at the metallic edge contact of ReS2 field effect transistors

The in-plane anisotropy of electrical conductance in two-dimensional materials has garnered significant attention due to its potential in emerging device applications, offering an additional dimension to control carrier transport in 2D devices. However, previous research has primarily focused on the anisotropy within electrical channel, neglecting the significant impact of anisotropic electrical contacts of 2D materials. Here, we investigate anisotropic charge transport at the metal contacts of hBN-encapsulated ReS2 using edge-contacted Field Effect Transistors. We observed the marked difference in contact resistance between the cross-b and b directions, suggesting that charge transport from the metal to ReS2 is more efficient along the b direction. This difference in efficiency results in a substantial contact anisotropy, reaching ~70 at 77 K. Our findings indicate that the measured Schottky Barrier Height along the b direction is ~35 meV, which is smaller than along the cross-b direction. Moreover, the tunneling probability along the b direction is two times larger than along the cross-b direction. Our results indicate that both Schottky Barrier Height and tunneling amplitude are the primary contributors to the high contact anisotropy of ReS2. This work provides a valuable guideline for understanding how in-plane orientation influences charge transport at metallic contacts in 2D devices.

Analysis of internal wave in the Buru Island coastal waters, Banda Sea, Indonesia

The Indonesian throughflow (ITF) in the eastern part of Indonesia passes through the Maluku, Taliabu, Sula, and Buru Islands to the Banda Sea. The average depth of the Buru and Sula Islands is between 1000 m and 5000 m, with a narrow gap (sill) located to the north and south at a depth of 165 m on the sea map. This topography makes for interesting research on the western waters of Buru Island. Therefore, this study aimed to obtain salinity, temperature, and density values as water column stratification associated with the internal wave (IW), thermocline area, and current patterns at specific depths in the waters of Buru Island, Banda Sea. Data were collected from initial observations of Sentinel 1 satellite imagery of Buru Island to obtain an image of the waves in the water area. Furthermore, a single beam echosounder (SBES), conductivity temperature depth (CTD), and Copernicus Marine were analysed at the same position and time. The research found a non-linear IW Mode 2 at depths of 440–540 m with an estimated amplitude length is 40 km and an amplitude height of 100 m. Based on SBES echogram imaging, CTD data analysis, and modelling, there was an increase in IW density, a 35.25 PSU increase in salinity value at depths of 50∼200 m, a temperature decrease of 27.5 °C to 10 °C at depths of 50∼300 m, and a density stratification of 23.5 kg/m³ to 27 kg/m³ at depths of 50∼300 m.

Alterations in paraffin wax crystal networks induced by asphaltenes and pour point depressants, investigated by atomic force microscopy

Wax crystallization in pipelines in cold environments is a key factor affecting flow assurance during crude oil production. Polar crude oil components, such as asphaltenes, and polymeric pour point depressants (PPDs) have been demonstrated to interact with wax during gelation and crystallization through complex formation during nucleation or crystal growth alteration which leads to co-crystallization. This study introduces a methodology based on atomic force microscopy (AFM) to characterize features of solid surfaces precipitated from model wax, wax-PPD, wax-asphaltene and asphaltene systems. Height data collected from AFM measurements enabled the quantification of modifications in crystal sizes and shapes induced by the presence of asphaltenes and PPDs. The 2D Fourier transform of the height was used to generate statistics for the frequency of height amplitude, revealing information about the pore size and the height patterns. A stiffness/elasticity analysis was used to calculate the Young Modulus of the upper layers. In wax and wax-asphaltene systems, two nano-scale layers with different Young Modulus profiles emerged. The nano-scale layer on the top was softer and corresponded to more amorphous wax crystal networks with trapped dissolved wax. The nano-scale layer on the bottom was stiffer, comprising of more crystalline structures, corresponding to wax crystals with lower deviations from full crystallinity, with properties independent of asphaltene concentration. A bilayer did not form in the presence of PPD, which prevented the formation of amorphous phases with trapped dissolved wax or gel. After a methodology for model systems was established, the focus moved to systems based on production wax i.e. recovered from deposits. This was complemented by a comparison between model precipitation conditions and precipitation by cold finger, resembling industrial processes. Results highlighted the effect of change in chemical composition on topography, elasticity and adhesion of the surface. AFM provided new insights into wax crystallization patterns in the presence of inhibitors, which can be used to quantify the extent of wax-inhibitor interactions and project it on production systems. The method could be used to explain macro-scale rheological properties of oils during flow assurance in the future.

Assessment of WRF-CO2 simulated vertical profiles of CO2 over Delhi region using aircraft and global model data

High-resolution regional model simulation of CO2 may be more beneficial to reduce the uncertainty in estimation of CO2 source and sink via inverse modeling. However, the study of atmospheric CO2 transport with regional models is rare over India. Here, weather research and forecasting chemistry model adjusted for CO2 (WRF-CO2) is used for simulating vertical profile of CO2 and its assessment is performed over Delhi, India (27.4–28.6° N and 77–96° E) by comparing aircraft observations (CONTRAIL) and a global model (ACTM) data. During August and September, the positive vertical gradient (~ 13.4 ppm) within ~ 2.5 km height is observed due to strong CO2 uptake by newly growing vegetation. A similar pattern (~ 4 ppm) is noticed in February due to photosynthesis by newly growing winter crops. The WRF-CO2 does not show such steep increasing slope (capture up to 5%) during August and September but same for February is estimated ~ 1.7 ppm. Generally, CO2 is quite well mixed between ~ 2.5 and ~ 8 km height above ground which is well simulated by the WRF-CO2 model. During stubble burning period of 2010, the highest gradient within 2.5 km height above ground was recorded in October (− 9.3 ppm), followed by November (− 7.6 ppm). The WRF-CO2 and ACTM models partially capture these gradients (October − 3.3 and − 2.7 ppm and November − 3.8 and − 4.3 ppm respectively). A study of the seasonal variability of CO2 indicates seasonal amplitudes decrease with increasing height (amplitude is ~ 21 ppm at the near ground and ~ 6 ppm at 6–8 km altitude bin). Correlation coefficients (CC) between the WRF-CO2 model and observation are noted to be greater than 0.59 for all the altitude bins. In contrast to simulated fossil CO2, the biospheric CO2 is in phase with observed seasonality, having about 80% at the lowest level and gradually declines with height due to mixing processes, reaching around 60% at the highest level. The model simulation reveals that meteorology plays a significant role of the horizontal and vertical gradient of CO2 over the region.

The impact of climate change on the taxonomic composition of the Zagatala State Nature Reserve

Zagatala State Nature Reserve is one of the first reserves created in the South Caucasus. The territory of this reserve, organized in 1929, is 47349 ha. The fact that the Zagatala Reserve is bordered by the Lagodekhi Reserve (Georgia) and the Tiyarta Ban (Russia) further increases its natural conservation importance. The main four factors that influence the climate of the reserve are geographical latitude, the protection of the area from the north by mountain ranges, the presence of a strongly fragmented relief and the height amplitude of the area to be high (up to 360-3600 m). Because the soil is rich and the relief is complex, the flora and vegetation are also diverse. Only 1.6% of its area covered by forest is mainly coniferous Pinus hamata (Steven) Sosn., Taxus baccata L., Juniperus oblonga M.B. species. Pinus hamata (Steven) Sosn., which grows naturally only in Balakenchay basin in Azerbaijan it is sparsely distributed in the not very high mountain range up to 1000 m in height between Balakenchay and Filizchay, at an altitude of 1200 m above sea level. In the Zagatala State Nature Reserve, the main composition of the flora is petrophytes, i.e., rock plants consisting of stony soil.

Characterization of the Maximum Height of a Surface Texture.

Average surface height and maximum amplitude can affect surface functions. In the industry, these parameters can be obtained based on profile measurements. However, variability in maximum profile height is high. A more stable parameter can be obtained from the results of the areal surface topography measurements as the average value of the parallel profiles. The aim of this study is to establish this parameter directly from the result of the areal surface texture by correcting the maximum surface height to material ratios in the range of 0.13-99.87%. This method was tested by measuring 100 surface topographies with a stylus profilometer and a white light interferometer. It can be utilized correctly for deterministic textures and random one- and two-process surfaces for which the correlation between neighboring profile ordinates is not very high. In other cases, the method should be modified. Employing this method, the maximum profile amplitude Pt and parameters characterizing the average profile height Pq, Pa, and the ratios Pq/Pa and Pp/Pt describing the shape of the profile ordinate distribution can be correctly estimated. Pq/Pa and Pp/Pt were more stable than the kurtosis Pku and skewness Psk. The corrected maximum height S±3σ can be adopted as a parameter that characterizes the areal surface texture as more stable than the maximum surface height St. Pq/Pa and Pp/Pt were more steady than kurtosis Pku and skewness Psk.

Numerical Analysis of the Impact Parameters on the Dynamic Response of a Submerged Floating Tunnel under Coupling Waves and Flows

The Submerged Floating Tunnel (SFT) is a highly promising cross-sea transportation structure. Due to its body being suspended in water, waves and flows are the primary environmental loads it encounters. Existing numerical simulations have been based on potential flow theory, which fails to fully consider shear forces and the nonlinear characteristics of the flow field. To overcome this limitation, the Computational Fluid Dynamics (CFD) approach, relying on solving the Navier-Stokes equations, can be employed. In this study, we establish a CFD model for the SFT and analyze the impact mechanisms of wave-flow coupling on its dynamic response, considering parameters such as wave height, flow velocity, wave direction, and flow direction. With increasing wave height, the acceleration, mooring tension, and heave amplitude of the SFT significantly increase, and the nonlinear characteristics of its dynamic response become more pronounced. For example, when wave height, Hi, increases from 0.046 m to 0.138 m, the maximum value of dimensionless heave, δz/Hi, increases from 0.075 to 0.284, nearly quadrupling in magnitude. When waves and flows propagate in the same direction, the heave amplitude of the SFT increases compared to the case with waves acting alone, while sway and roll amplitudes decrease. Under conditions of higher flow velocity, the SFT displaces significantly along the direction of flow and water depth, deviating significantly from its original equilibrium position. At this point, the tunnel primarily experiences periodic forces due to vortex shedding, and the anchor chain on the downstream side remains slack. In scenarios where waves and flows propagate in opposite directions, both the maximum acceleration and mooring tension of the SFT increase significantly. For instance, the onshore tension of the cable, Fon, increases by 36%, while the offshore tension, Foff, increases by 89%.

Development of an efficiency ranking system for beef cows and effects on feed intake, ruminal fermentation, NDF turnover, and apparent total tract digestibility

Beef cows ( n = 100) were ranked for efficiency based on cow rump fat thickness at calving, calving date, and calf weaning weight (% dam BW) over 2 years. The nine most (ME) and least efficient (LE) cows were used to compare feed intake and ruminal fermentation using four 26-day periods with decreasing dietary nutrient density. There were no phenotype × diet interactions for variables of primary interest. Rump fat and calf weaning weight were greater, and the calving date was earlier for ME cows than LE cows ( P ≤ 0.032). The ME cows were lighter ( P < 0.001) but had similar DMI ( P = 0.93) to the LE cows, resulting in greater dry matter intake (DMI) %BW ( P < 0.001). Ruminal contraction amplitude height and area ( P ≤ 0.015) and ruminal digesta weight were greater for LE than ME cows ( P = 0.043). Ruminal ash-free neutral detergent fiber (aNDFom) passage was greater for ME cows than LE cows ( P = 0.047), but the rate of aNDFom degradation did not differ ( P = 0.69). Total tract digestibility did not differ. Efficient cows had greater rump fat, weaned heavier calves, ate more relative to their BW, had a smaller ruminal digesta mass, and had greater ruminal passage of aNDFom without reducing digestibility.

ОПРЕДЕЛЕНИЕ ПОПЕРЕЧНЫХ РАЗМЕРОВ ДЕФЕКТОВ РАССЛОЕНИЯ БИМЕТАЛЛИЧЕСКОЙ ПЛАСТИНЫ ПРИ АКТИВНОМ ТЕПЛОВОМ НЕРАЗРУШАЮЩЕМ КОНТРОЛЕ

Various methods of nondestructive testing, including active infrared thermography, are used to detect latent subsurface defects in the contact of layers in multilayer products. One of the main difficulties using this method consists in processing and interpreting the thermal image data. The peculiarity of investigated defects of bimetal plate layers continuity violation is that the depth of defect location is known and the main task is to determine its size. Some methods are used for this purpose including analysis of spatial temperature profiles. Aim. To analyse the use of various approaches to determining the transverse dimensions of a delamination between metals in simulating active thermal non-destructive testing of steel-aluminium plates. Materials and methods. Mathematical and computer simulating methods, numerical differentiation are used. The delamination size is determined by projections of half the height of the amplitude signal and the extremum of the derivative of the temperature signal function. Calculations and graphical constructions are performed using the mathematical package GNU Octave. Results. Numerical simulation is carried out for different values of heat flow power, heating and cooling time. The temperature signal distribution over the surface of a multilayer bimetallic plate has been plotted. The values of the defect radius according to the projections of the characteristic points are determined. Conclusion. The results of simulation allow us to conclude that using the projection of the extremum of the temperature signal derivative function allows us to accurately estimate the defect size, while in the case of the point projection cor¬responding to half of the signal amplitude height, the result is underestimated. The obtained results can be used for further experimental studies of processes of active thermal non-destructive testing of products made of multilayer bimetallic materials.

Bullwhip effect: Modelling and simulation of a sinusoidal stimulus considering food waste

Background: The current coronavirus disease 2019 (COVID-19) pandemic has stressed why a change towards resilient, robust and sustainable supply chains is more imperative than ever. This is especially true for supply chains of perishable foods, where issues such as the bullwhip effect cause not only economic but also environmental damage.Objectives: The key objectives of this study are to gain a deeper insight into correlations regarding the causes of the bullwhip effect and to see how a sinusoidal stimulus is affecting the generation of food waste.Method: A simplified beef food chain was modelled in Tecnomatix Plant Simulation®. As the bullwhip effect consists of a simplified parameterisation of an excitation duration (period length) and its height (amplitude), these two variables were used to generate a sinusoidal stimulus. The simulation results were statistically verified and checked for commonalities and differences with the already established scientific knowledge.Results: While the expected higher sensitivity of the front links of the supply chain to waste generation can be confirmed, the results of a long stimulation period suggest that the negative effects of the bullwhip effect do not increase indefinitely.Conclusion: The analysis of the results has shown that previous theories can be transferred, but that the variation of the variables entails new insights for the interdependencies of the amplitude and period length and their influence on the output variable waste.Contribution: The study contributes to a more holistic understanding of the bullwhip effect and, in particular, its implications within a perishable food supply chain.

Spectral Wave Dissipation Over a Roughness‐Varying Barrier Reef

AbstractThe present paper reports on a field experiment performed over a shallow, roughness‐varying barrier reef at Maupiti island, French Polynesia. The spectral wave energy balance is examined, outside the breaking zone and accounting for non‐linear transfers and mean current, to estimate the wave friction factor. This latter varies from 0.05 to 4, with dependence on the ratio between near‐bed orbital amplitude and roughness height well predicted by an adjusted parameterization from Madsen (1995). The present results are discussed with respect to other field data recovered on coral and rocky grounds.

Experimental generation and investigation of Peregrine breather waves in deep water

ABSTRACT The modulation instability is a prominent explanation for the occurrence of nonlinear freak waves. The modulation instability could be described by the famous nonlinear Schrödinger (NLS) equation. The Peregrine breather solution of the NLS equation is usually adopted as a prototype in freak wave simulation. The freak waves based on the Peregrine breather solution (Peregrine breather waves) are characterised by huge wave crests, large wave heights and concentrated energies. In this paper, the Peregrine breather waves are experimentally generated in deep water. The specific experimental wave-making procedure is first proposed. The measured wave elevations show great agreement with the analytical solutions. Moreover, the modulation instability scenario is observed by wavelet analysis. The effects of wave parameters on wave energy distributions are first analysed. The results indicate carrier wave amplitude and wave height determine the width of focusing energy frequency and carrier wave frequency determines the duration of focusing energy.