Analysis of Damage Evolution in Concrete under Fatigue Loading by Acoustic Emission and Ultrasonic Testing

The fatigue process of concrete under compressive cyclic loading is still not completely explored. The corresponding damage processes within the material structure are especially not entirely investigated. The application of acoustic measurement methods enables a better insight into the processes of the fatigue in concrete. Normal strength concrete was investigated under compressive cyclic loading with regard to the fatigue process by using acoustic methods in combination with other nondestructive measurement methods. Acoustic emission and ultrasonic signal measurements were applied together with measurements of strains, elastic modulus, and static strength. It was possible to determine the anisotropic character of the fatigue damage caused by uniaxial loading based on the ultrasonic measurements. Furthermore, it was observed that the fatigue damage seems to consist not exclusively of load parallel oriented crack structures. Rather, crack structures perpendicular to the load as well as local compacting are likely components of the fatigue damage. Additionally, the ultrasonic velocity appears to be a good indicator for fatigue damage beside the elastic modulus. It can be concluded that acoustic methods allow an observation of the fatigue process in concrete and a better understanding, especially in combination with further measurement methods.

Estimating target strength of young chum salmon (Oncorhynchus keta)

Although chum salmon (Oncorhynchus keta) is an important fishery resource in Japan, acoustic methods cannot be applied to biomass estimation because the target strength (TS) is unknown. This study clarified the TS for each fork length (FL: 5.5–33.5 cm) of young chum salmon inhabiting the Japanese coastal area to the Bering Sea by measuring free-swimming fish. The size dependences of the TS values were TSmean = 20 log10 FL – 68.0, for both 38 and 120 kHz. This facilitated the estimation of biomass of young salmon using acoustic methods.

Низкотемпературные электрические свойства CVD графена на LiNbO-=SUB=-3-=/SUB=-: акустические исследования

Contactless acoustic methods were used to determine electrical parameters - electrical conductivity, carrier mobility and their concentration - in single-layer graphene deposited on the surface of lithium niobate.

Acoustic methods in real-time welding process monitoring: Application and future potential advancement

The rapid advancement of the welding technology has simultaneously increased the demand for the online monitoring system in order to control the process. Among the methods that could be possibly used to assess the weld condition, an air-borne acoustic method grasps the attention from scholars due to its ability to provide a simple, non-contact, and low-cost measurement system. However, it is still lack of resources involving this subject in an attempt to deeply understand the emitted sound behaviour during welding especially when dealing with a complete deviation of a process parameter, welding types, workpiece material as well as the noise from the surrounding. This paper reviews the application of the acoustic method in monitoring the welding process. Specifically, this review emphasized the source of both structure-borne and air-borne acoustic during the welding process and the significance of applying the acoustic method in more detail. By focusing on the liquid state welding process, the scope of discussion converged on the arc and laser welding process. In the last part of this review, the potential future advancement of this method is pointed out before the overall conclusion is made.

Tracking and Analysis of the Movement Behavior of European Seabass (Dicentrarchus labrax) in Aquaculture Systems

Monitoring and understanding fish behavior is crucial for achieving precision in everyday husbandry practices (i.e. for optimizing farm performance), and for improving fish welfare in aquaculture. Various intelligent monitoring and control methods, using mathematical models, acoustic methods and computer vision, have been recently developed for this reason. Here, a tracking algorithm based on computer vision that extracts short trajectories of individual European seabass in both recirculating aquaculture systems and sea cages was developed using videos from network cameras. Using this methodology, parameters such as instantaneous normalized speed, travel direction and preference for the tank surface by European seabass could be quantified. When testing the sensitivity of this algorithm for detecting fish swimming variations under different husbandry scenarios, we found that the algorithm could detect variations in all of the abovementioned parameters and could potentially be a useful tool for monitoring the behavioral state of European seabass.

On probabilistic-physical and entropy approaches to combustion processes and determination of fire hazard

Introduction. The article provides an overview of the existing approaches to solving the problem of combustion of substances and materials, for their adequacy in determining their fire hazard of products and objects. The relevance of the work is due to the need to move from latent forms in determining the fire hazard of materials and products made from them (degrees of fire resistance, flammability groups, groups of the effectiveness of fire retardant coatings, etc.) to analytical forms describing the processes in the combustion theory. Problem statement. The task of the research is to determine the relationship between the theory of combustion of substances and materials and to assess their fire hazard in natural and man-made systems. Theoretical part. The system analysis of solutions to the combustion theory problems is performed. Its results became the basis of probabilistic-physical and entropy approaches, as well as proposals for changing standards designed to provide protection from fires. Conclusions. The results of the study showed the need to revise empirical approaches in assessing the fire hazard of materials and products made from them, which includes using thermoanalytic and acoustic methods and means.

Occurrence of the birds of the Middle Volga Region (South-East of the European part of Russia)

Birds are the most numerous and widespread group of higher vertebrates. Due to the peculiarities of their biology, birds play an important role in nature and in human life. Ornithological studies described in this publication were conducted in seven regions of the Middle Volga Region (Chuvashia, Mordovia, Tatarstan, Samara, Nizhny Novgorod, Ulyanovsk and Penza Regions) from 1978 to 2021. Visual and acoustic methods were used to study the species composition during field studies. In total, 5065 birdoccurrences belonging to 157 species, 48 families and 19 orders were registered. All occurrences have a geographical reference. The large volume of data collected, the wide geographical coverage and the long-term nature of the observations determined the value of their inclusion in the GBIF and the need for publication in the Biodiversity Data Journal. We are publishing our original data on the coordinates of bird occurrences in the Middle Volga Region for the first time. Most of the original information about bird occurrences was contained in field diaries and was not available to a wide range of researchers. All 5065 occurrences are new to GBIF.

Acoustic deterrents influence foraging activity, flight and echolocation behaviour of free-flying bats

Acoustic deterrents have shown potential as a viable mitigation measure to reduce human impacts on bats, however, the mechanisms underpinning acoustic deterrence of bats have yet to be explored. Bats avoid ambient ultrasound in their environment and alter their echolocation calls in response to masking noise. Using stereo thermal videogrammetry and acoustic methods, we tested predictions that i) bats would avoid acoustic deterrents and forage and social call less in a ‘treated airspace’; ii) deterrents would cause bats to fly with more direct flight paths akin to commuting behaviour and in line with a reduction in foraging activity, resulting in increased flight speed and decreased flight tortuosity; iii) bats would alter their echolocation call structure in response to the masking deterrent sound. As predicted, overall bat activity was reduced by 30% and we recorded a significant reduction in counts of Pipistrellus pygmaeus (27%), Myotis spp. (probably M. daubentonii) (26%) and Nyctalus and Eptesicus spp. (68%) passes. P. pygmaeus feeding buzzes were also reduced by the deterrent in relation to general activity (by 38%), however social calls were not (only 23% reduction). Bats also increased their flight speed and reduced the tortuosity of their flight paths and P. pygmaeus reduced echolocation call bandwidth and start frequency of calls in response to deterrent playback, probably due to the masking effect of the sound. Deterrence could therefore be used to remove bats from areas where they forage, for example wind turbines and roads, where they may be under threat from direct mortality.

Distribution of the Pearl Oyster Pinctada maxima off Eighty Mile Beach, Western Australia

The silver-lipped pearl oyster, Pinctada maxima, is the primary species used for the culture of pearls in the Indo-Pacific region. The Western Australian fishery relies on wild-caught animals, and as such, knowledge of the status and distribution of P. maxima underpins sustainable management of the fishery. Eighty Mile Beach, in tropical Western Australia, is the key harvest area for P. maxima, with oysters collected by divers to depths of ∼35 m, although there are anecdotal accounts of oysters beyond diving depths. Image-based, and acoustic methods were used to elucidate distribution patterns of P. maxima off Eighty Mile Beach, including data from 862 km2 of multibeam survey and 119 towed video transects spanning an area from the 20 to 100 m contour lines. We quantified habitat characters including depth, substrate, and benthic community composition associated with pearl oyster distribution. Multibeam sonar data was also coupled with towed video data to produce predictive statistical models of P. maxima habitat. We found P. maxima to depths of 76 m, although more than 90% of individuals occurred shallower than 40 m and less than 2% were found deeper than 50 m. Oysters occupied flat, sandy habitats with neighbouring benthic communities of filter feeders (>98% of observations). These results show P. maxima predominantly occurs in depths <40 m, with no evidence that extensive populations extend into deep water in the region.