Tank Experiments Research Articles

Phase-resolved real-time ocean wave prediction with quantified uncertainty based on variational Bayesian machine learning

Phase-resolved wave prediction is of vital importance for the real-time control of wave energy converters. In this paper, a novel wave prediction method is proposed, which, to the authors’ knowledge, achieves the real-time nonlinear wave prediction with quantified uncertainty (including both aleatory and model uncertainties) for the first time. Moreover, the proposed method achieves the prediction of the predictable zone without assuming linear sea states, while all previous works on predictable zone determination were based on linear wave theory (which produces overly conservative estimations). The proposed method is developed based on the Bayesian machine learning approach, which can take advantage of machine learning model’s ability in tackling complex nonlinear problems, while taking various forms of uncertainties into account via the Bayesian framework. A set of wave tank experiments are carried out for evaluation of the method. The results show that the wave elevations at the location of interest are predicted accurately based on the measurements at sensor location, and the prediction uncertainty and its variations across the time horizon are well captured. The comparison with other wave prediction methods shows that the proposed method outperforms them in terms of both prediction accuracy and the length of the predictable zone. Particularly, for short-term wave forecasting, the prediction error by the proposed method is as much as 55.4% and 11.7% lower than the linear wave theory and deterministic machine learning approaches, and the predictable zone is expanded by the proposed method by as much as 74.6%.

Effects of carbon-nitrogen ratio manipulation on the growth performance, body composition and immunity of stinging catfish Heteropneustes fossilis in a biofloc-based culture system

A 10-week indoor culture study was done to evaluate the effects of varying C/N ratios on growth performance, body composition, immunity, and haematology of stinging catfish Heteropneustes fossilis cultured in zero-water exchange culture tanks. Biofloc-based tanks with four levels of C/N ratio (12, 15, 18, 21) via the addition of carbohydrate referred to as ‘CN12′, ‘CN15', 'CN18' and 'CN21', and freshwater tanks operated with the facility of water exchange and without the addition of carbohydrate referred to as 'Control' (CN10). Fish (average weight 0.60 g) were stocked in 15 experimental tanks with 300 L water capacity and fed a commercial diet containing 30 % crude protein. The water quality parameters (pH, temperature, total ammonia nitrogen, nitrite nitrogen, dissolved oxygen, total suspended solids, and total dissolved solids) were monitored throughout the experiment. There was no significant (P > 0.05) difference among the treatments in the case of DO and temperature. The pH, total ammonia nitrogen, and nitrite nitrogen contents decreased with increasing C/N ratio, whereas the total dissolved solids and total suspended solids increased with gradually increasing the C/N ratio. Compared to the control, the treatment CN15 resulted in a 72 % and 34.4 % higher percent weight gain and specific growth rate, respectively. CN15 treatment resulted in improved feed utilization, as measured by feed conversion ratio (1.32 ± 0.07) and protein efficiency ratio (1.36 ± 0.10), which were 36.2 % lower and 54.5 % higher, respectively, than control. However, there were no differences in growth performance and feed utilization data between CN15 to CN21. Increasing the C/N ratio increased the body protein and ash contents and decreased the moisture and lipid contents compared to control. In the serum lysozyme test, the lysozyme value increased with a gradually increasing C/N ratio, and a better result was found in the CN15-CN21 treatments (15.58–15.74 µg ml−1) compared to the control (12.45 µg ml−1). At the end of the rearing period, fish were subjected to a challenge test with Aeromonas hydrophilla to determine the mortality rate where mortality was the lowest in CN15 treatment. Furthermore, increasing the C/N ratio from 15 to 21:1 showed better results for haemoglobin, white blood cells, red blood cells and hematocrit values. Overall, the manipulation of the C/N ratio from 15 to 21:1 revealed suitable for the feed utilization, growth performance, body composition, and immunity of stinging catfish. Therefore, maintaining a C/N ratio of 15:1 can be recommended for the culture of stinging catfish in the biofloc system.

Study on a Detection Technique for Scholte Waves at the Seafloor.

Scholte waves at the seafloor have significant potential for underwater detection and communication, so a study about detecting Scholte waves is very meaningful in practice. In this paper, the detection of Scholte waves at the seafloor is researched theoretically and experimentally. Acoustic models with the multilayer elastic bottom are established according to the ocean environment, and a tank experiment is designed and carried out to detect Scholte waves. Different from detecting Scholte waves in the seismic wavefield, a technique for detecting Scholte waves in the sound pressure field is proposed in this paper. The experimental results show that the proposed technique can detect Scholte waves effectively, and there are no problems such as seabed coupling and the effect of wave speeds. Furthermore, the results also show that this detection technique is still effective in conditions with a sediment layer. The existence of sediment layers changes the acoustic field conditions and affects the excitation of Scholte waves.

The effects of acidification on arsenic concentration and speciation in offshore shallow water system

The effects of acidification on speciation and transportation of arsenic in shallow seawater system were investigated based on data from acidification simulation experiments in lab scale tanks, in which enhanced levels of pCO2 corresponding to pHT were processed. The results showed that: (1) the concentration of DIAs (Dissolved inorganic arsenic), As5+ and As3+ in the overlying water increased with experimental CO2 enrichment; (2) while the ratio of As5+/As3+ decreased; (3) acidification could cause more DIAs transport into the overlying water from sediments or suspended particulate matters, and would be favorable to the existence of As3+. Thus, DIAs is available to microorganisms and can be taken in effectively by microorganisms in the shallow water system, resulting in toxic effects of As on microorganisms and thus the inhibition of the growth of microorganisms.

The Influence of the Discharge Port Structure on the Infrared Characteristics of Underwater Vehicle Thermal Jets

The circulating cooling water of underwater vehicle power systems is discharged through the discharge port and is mixed with the environmental water to form a thermal jet, which diffuses, floats up in the environmental water and displays infrared characteristics on the surface of the water body. In order to explore the influence of the discharge port structure on the infrared characteristics of underwater vehicle thermal jets, this paper adopts the methods of simulation analysis and experimental verification, and it establishes an underwater vehicle motion model based on the CFD computing software platform to design elliptic discharge port structures with different radius ratios and to compare their different thermal jet infrared characteristics. The influence of the oval discharge port radius ratio on the infrared characteristics of thermal jets is verified by the reduced-scale water tank experiment, and the authenticity of the simulation calculation method and design parameters is verified. On the basis of oval discharge ports, the number and distribution position of discharge ports are further designed to suppress the infrared characteristics of thermal jets and to improve the thermal stealth performance of underwater vehicles. According to the simulation calculation and experimental results, under the condition of the same discharge flow, as the radius ratio becomes smaller, the mixing heat transfer effect of the thermal jet becomes better, and the infrared characteristics become less obvious. Moreover, increasing the number of discharge ports and adopting the symmetrical arrangement of discharge ports can further strengthen the temperature attenuation of thermal jets and reduce the surface maximum temperature.

Comparative study of three insulation materials installed on type C independent tank for offshore LNG transportation

The traditional choice of insulation material for offshore LNG transportation with type C independent tank was polyurethane foam (PUF). However, aiming to further cut down the insulation cost and spare additional arrangement space, the requirement of searching for the alternative materials still exists. Polyisocyanurate board (PIRB) and silica aerogel blanket (SAB) are chosen as candidates in this study since these two materials have been proved to be available in other fields. Despites their advantages, the seams and joints due to the specific installation techniques for PIRB and SAB could be the causes of potential defects when transporting cryogenic liquid. In this paper, the comparative study of three materials associated with their specific installation techniques was conducted to discuss if PIRB and SAB are available for offshore LNG transportation. Therein, the insulation performances were investigated through the evaporation experiment of LN2 with a 1.5 m3 type C experimental tank. The equivalent conductive model was adopted in the numerical analysis with finite element method (FEM) to determine the temperature field of insulation and the absorbed heat from the LN2 evaporation. It is proved that three types of insulation materials are well behaved and available for transporting cryogenic liquid. In respect of the thermal resistance, the ranking of three types of insulation materials is: SAB, SPF and PIRB. Higher thermal resistance of insulation leads to thinner thickness and additional arrangement space in the cargo hold, and more ship construction cost can be cut down due to the possible scaling down of ship dimensions. However, from the perspective of insulation material cost, the cost reduction due to the insulation thickness decrease is not significant as the tank continually scales up, and it is more practical to apply SPF or PIRB on a full-scale type C independent tank.

Development of thermal resistance prediction model and measurement of thermal resistance of clothing under fully wet conditions

When clothing is immersed in water, the water will rapidly occupy the internal void of the clothing, and the air layer inside the clothing will disappear, which leads to a drastic reduction in the thermal resistance of the clothing. To calculate the thermal resistance of clothing under fully wet conditions, a novel serial method was proposed. The method is a combination of the thermal resistance of water and the thermal resistance of wet fibers. To verify the effectiveness of the new method, the thermal resistances of three typical suits under fully wet conditions were measured. Three typical suits, a summer suit (T-shirt + shorts), a spring suit (sportswear + sweatpants), and a winter suit (cotton coat + wool pants), were chosen as test objects. The thermal resistances of these suits under fully wet conditions were measured in an experimental water tank built in a chamber using a thermal manikin, “Walter.” The thermal resistance measurement in this study can eliminate the experimental error caused by the evaporation of water so as to obtain an accurate thermal resistance measurement. According to the experimental results and the model, the key factors affecting the thermal resistance under fully wet conditions were thickness ( Rpearson = 0.992), porosity ( Rpearson = 0.980), and moisture content ( Rpearson = 0.964). Compared to other thermal resistance prediction models, the prediction results by the novel method were more consistent with the measured results, with all deviations less than 10% and the correlation value R2 = 0.998.

Experimental Study of Al-Modified Zeolite with Oxygen Nanobubbles in Repairing Black Odorous Sediments in River Channels

As an extreme phenomenon of water pollution, black odorous water not only causes ecological damage, but also severely restricts urban development. Presently, the in situ remediation technology for sediment from river channels is still undeveloped, and there are many bottlenecks in the key technologies for sediment pollution control and ecological restoration. In this study, three experimental tanks were used to explore the restoration effect of Al-modified zeolite with oxygen nanobubbles on black odorous sediment from the Shichuan River. One of the tanks housed Typha orientalis and Canna indica L. (TC), another tank housed the same plants and had Al-modified zeolite with oxygen nanobubbles (TC+AMZON), and the last tank was used as a comparison test (CS). The results show that the nitrogen (N) and phosphorus (P) in the sediment are violently released into the surrounding water. However, TC+AMZON could effectively inhibit the release of P. The released amount of soluble reactive phosphorus (SRP) from the pore water in the sediment reached its maximum at 40 d, and the amounts were 122.97% and 74.32% greater in TC and CS, respectively, than in TC+AMZON. However, the released amount of total phosphorus (TP) reached its maximum at 70 d, and the amounts were 260.14% and 218.23% greater in TC and CS, respectively, than in TC+AMZON. TC+AMZON significantly increased the dissolved oxygen (DO) and the oxidation-reduction potential (ORP) of pore water in the sediment in the early stages of the test. At 0 d, the DO content in TC+AMZON reached 10.6 mg/L, which is 112.0% and 178.95% greater than in TC and CS, respectively. The change law of ORP in the sediment is consistent with the DO. TC+AMZON significantly improved the transparency and reduced the content of chlorophylla in the upper water and could slightly reduce the N and P content in overlying water. The transparency of TC+AMZON increased by 130.76% and 58.73%, and chlorophylla decreased by 55.6% and 50.0% when compared to TC and CS, respectively.

Autonomous Underwater Vehicle Depth and Pitch Trajectory Tracking Using Fiber-Reinforced Elastomer Bladders for Buoyancy Control

This article presents a variable buoyancy system that uses cephalopod-inspired, fiber-reinforced elastomer membranes as bladders to enable model-based depth and pitch control of an autonomous underwater vehicle. The fiber reinforcement allows for a single measurement of each membrane to fully define the geometry of the membrane, regardless of the membrane’s orientation or level of inflation. This allows for precise control of each bladder’s enclosed water mass and center of mass by adjusting the differential pressure between the inside of the bladder and the vehicle’s cabin using water from the environment as the working fluid. Positioning bladders at the fore and aft of the vehicle enables control of both the vehicle’s density and center of mass while minimizing center of mass disturbances due to sloshing in and gravitational loads on the membranes. A nonlinear, adaptive, backstepping, trajectory-tracking controller is presented and proven to be asymptotically stable with Lyapunov stability analysis. The advantages of the proposed variable buoyancy system and controller are demonstrated through simulation and validated with 2 degree of freedom depth and pitch step and trajectory-tracking experiments in a large water tank. We evaluate the performance of the bladders and controller on the CephaloBot, an autonomous underwater vehicle designed and built by our group.

Updated parameterization of internal tidal mixing in the deep ocean based on laboratory rotating tank experiments

The Coriolis effect plays an important role in the generation and dissipation of internal tides. In this study, the effects of the Coriolis parameter on internal tides generated by tidal current flowing over rough subsurface topography were investigated in the laboratory. The results show that the variation in the internal tidal local dissipation rate with variation in the Coriolis parameter in the deep layer follows a Gaussian distribution. The strongest dissipation occurs near the critical latitude where the local Coriolis parameter is half of the tidal frequency. A modified internal tidal mixing parameterization was developed by introducing a correction function related to the Coriolis effect on internal tidal local dissipation in the deep ocean, based on the original version developed by St. Laurent et al. (2002). The new parameterization was then implemented in a parallel ocean model. The results indicate that the deep global meridional overturning circulation (GMOC) is strengthened in the low and middle latitudes and the Southern Ocean by the change, compared with the original parameterization.

Effective roughness on the sea surface for determining variability characteristics of reflected sound waves

In sound wave propagation in the sea, it is important to evaluate the characteristics of sound reflection from the sea surface. The amplitude and phase of reflected sound waves fluctuate because of the changing sea surface with waves. In this study, using the finite difference time domain method and experiments in a water tank, we evaluated the variability characteristics of reflected sound waves on the sea surface generated by the Bretschneider-Mitsuyasu spectrum observed on the deep offshore coast of Japan. We introduced the concept of effective roughness of the sea surface and evaluated the variability characteristics of reflected sound waves on the sea surface. We confirmed the Rice distribution could express the amplitude variability, and the energy ratio γ is determined by the Rayleigh roughness parameter defined by the effective roughness

Validation of the resistance of a plate moving through mud: CFD modelling and towing tank experiments

When investigating the effect of muddy seabeds on marine vessels using Computational Fluid Dynamics (CFD) software, one challenge is to adequately describe the complex non-Newtonian fluid behaviour of mud. Although a number of rheological models have been proposed in the past, mud sediments are often simply regarded either as highly viscous Newtonian fluids or as Bingham fluids in many engineering applications. In this study, we investigate the accuracy of the Bingham model for numerical predictions of the viscous forces on a plate moving through fluid mud in laminar regime. In this context, a plate could be regarded as the flat bottom of a ship hull. The aim is to provide CFD practitioners with information about the accuracy of the Bingham model for the prediction of the frictional resistance of a ship sailing through fluid mud. This work presents a comparison of experimental and numerical data on the resistance of a plate moving through fluid mud from the Europoort area (Netherlands). Results suggest that the regularised Bingham model can be a reasonable compromise between simplicity and accuracy for CFD simulations to investigate the effect of muddy seabeds on marine vessels. A comparison between CFD data and analytical formulas is also presented.

Complementary Acoustic Metamaterial for Penetrating Aberration Layers.

Impedance-matched acoustic materials were developed to improve ultrasound penetration through the aberration layer. The traditional ultrasound layer matching material is called a couplant, which can only enhance ultrasound transmission to soft biological media such as the cartilage and muscle but cannot penetrate hard media such as the bone. Here, we propose a phase-modulated complementary acoustic metamaterial based on the principle of impedance matching, which enables ultrasound to penetrate the bone, and use the equivalent parameter technology of acoustic metamaterials for parameter design. Ultrasonic layer adjustment is performed through 3D printing and corrects bone aberrations. Several configurations were investigated through numerical simulations and experiments in non-reflecting tanks. Specifically, the bone matching layer can be optimally designed for a specific bone thickness and a specific operating frequency of the ultrasound probe, thereby amplifying the ultrasound to penetrate the matching layer and bone. The experimental and simulation results show that the proposed acoustic metamaterial can improve the transmission efficiency of ultrasound through the aberration layer.

Open-source, low-cost, in-situ turbidity sensor for river network monitoring

Fine sediment transport in rivers is important for catchment nutrient fluxes, global biogeochemical cycles, water quality and pollution in riverine, coastal and marine ecosystems. Monitoring of suspended sediment in rivers with current sensors is challenging and expensive and most monitoring setups are restricted to few single site measurements. To better understand the spatial heterogeneity of fine sediment sources and transport in river networks there is a need for new smart water turbidity sensing that is multi-site, accurate and affordable. In this work, we have created such a sensor, which detects scattered light from an LED source using two detectors in a control volume, and can be placed in a river. We compare several replicates of our sensor to different commercial turbidity probes in a mixing tank experiment using two sediment types over a wide range of typical concentrations observed in rivers. Our results show that we can achieve precise and reproducible turbidity measurements in the 0–4000 NTU or 0–16g/L range. Our sensor can also be used directly as a suspended sediment sensor and bypass an unnecessary calibration to Formazin. The developed turbidity sensor is much cheaper than existing options of comparable quality and is especially intended for distributed sensing across river networks.

Proof of concept study for in-situ burn application using conventional containment booms – Design of Burning Tongue

In situ burning (ISB) hasn’t been widely used for offshore oil spill response for various reasons. We present a feasibility study for a new ISB method – the Burning Tongue (BT) concept. We conducted scaled experiments in the Ohmsett wave tank to demonstrate its feasibility. We produced a 35-m long “tongue” of burnable oil (average oil thickness 4.2 mm – above the thickness needed for ISB) by towing a conventional boom (with a 12″ (0.3 m) deep skirt) partially filled with crude oil and then released the oil through a 6″ (0.15 m) wide opening at the apex. We found that the boom movement produced a convergence zone just downstream that kept released oil thick and also pulled oil that entrained under the boom skirt into the thick “tongue” of oil. CFD modeling was performed to explain the flow hydrodynamics and the formation of the convergence zone, which indicates the phenomenon is universal. We used small harbor boom only partially filled with oil for this study and believe that a full-scale marine boom filled with oil would achieve an even thicker “burning tongue.” The BT concept could make ISB more widely used for oil spill response in offshore areas.

Dietary effects of supplementation of cattle stick Carpolobia lutea leaf on growth and reproductive indices of male and female Clarias gariepinus broodstock

Males and females broodstock of Clarias gariepinus (mean weight, 884.00±2.83g) were subjected to dietary supplementation of Cattle Stick (Carpolobia lutea) Leaf (CSL) at different inclusion levels of 0 (control), 0.5, 1.0 and 2.0% to evaluate the efficacy of the plant for growth performance and fertility enhancer. Clarias gariepinus broodstock (96) were allocated into 12 experimental fibre tanks at 8 fish per tank (4 males and 4 females) fed 40% crude protein at 3% body weight twice daily for 56 days. Each treatment was done in triplicate. Biological evaluation and reproductive indices were measured. There was significant difference (P0.05) in weight gained by fish fed experimental diets. Fish fed experimental diets containing CSL showed significantly higher (P 0.05) reproductive indices compared to the control diet. 0.5% inclusion level of CSL showed better performance in term of growth performance and reproductive indices and may be considered to be the best tolerance inclusion level for growth performance and fertility enhancer. The results of the study indicate that incorporating Cattle stick leaf diets in fish feed at 0.5% may have the potential for growth performance and fertility-enhancing agent in male and female C. gariepinus broodstock.Keywords: Clarias gariepinus, Carpolobia lutea leaf Growth, Reproductive indices, Broodstock

Effects of black soldier fly (Hermetia illucens) pre-pupae meal on the growth, stress, and immune responses of juvenile rainbow trout (Oncorhynchus mykiss) reared at different stocking densities

The present study investigated the effects of black soldier fly (Hermetia illucens) pre-pupae meal (BM) as a feed ingredient on the growth performance and health status (stress and immune response) of rainbow trout (Oncorhynchus mykiss) reared at different stocking densities. BM was used to replace 5 % of soybean meal in the control diet (CON). Juvenile rainbow trout (4.9 ± 0.2 g) were acclimated and placed in experimental tanks, at stocking densities of 4.9 (low density, LD) and 9.8 (high density, HD) kg/m3. Trout were assigned to four treatments (CON/LD, CON/HD, BM/LD, and BM/HD) in triplicates and reared for 6 weeks. After the feeding trial, fish reared in low-density tanks showed significantly higher weight gain regardless of diet (P < 0.05). In HD groups (CON/HD and BM/HD), however, fish fed the BM diet showed a significantly higher weight gain than those fed the CON diet. The lauric acid (12:0) content of BM groups (BM/LD and BM/HD), in the whole-body, was closely correlated with diets and significantly higher than that of the CON groups (P < 0.05). Fish from the BM/LD group showed significantly higher expression of interleukin 1β (IL-1β), interleukin 8 (IL-8), and immunoglobulin M (IgM) genes compared to the CON groups (P < 0.05). Although no statistical difference was detected, the overall response patterns of liver tissue in antioxidant and immune parameters, including superoxide dismutase (SOD), lysozyme activity (Lyz), IL-1β, and IgM, followed the expression of immune-related genes in response to the different diets and stocking density. In a challenge test with Aeromonas salmonicida for 10 days, fish fed the BM diet showed a significantly higher cumulative survival rate than those fed the CON diet (P < 0.05). These results suggest that BM could be a beneficial feed ingredient for juvenile rainbow trout, but that high stocking densities can negatively influence the growth and immune responses.

Dietary protein requirement for captive juvenile green turtles (Chelonia mydas).

Head-starting programs are extremely important for restoring the population of sea turtles in wild whereas husbandry conditions and feeding regimens of captive turtles are still limited. In the current study, the optimal dietary protein requirement for green turtle (Chelonia mydas) was investigated to support rearing in head-starting programs. Twenty-five-day-old turtles (44.5-46.2 g body weight, n = 45) were randomly distributed into 15 experimental plastic tanks, comprising three treatment replications of 3 turtles each. They were fed fishmeal-based feeds containing different levels of protein (30%, 35%, 40%, 45%, and 50%) for 8 weeks. At the end of feeding trial, growth performance (specific growth rate = 1.86% body weight/day) and feed utilization (protein efficiency ratio = 3.30 g gain/g protein) were highest in turtles fed with 40% protein in feed (p < .05). These nutritional responses were significantly supported by specific activities of fecal digestive enzymes, especially trypsin, chymotrypsin, amylase, and the amylase/trypsin ratio. Also, this dietary level improved the deposition of calcium and phosphorus in carapace, supporting a hard carapace and strong healthy bones. There were no negative effects in general health status of reared turtles, as indicated by hematological parameters. Based on a broken-line analysis between dietary protein levels and specific growth rate, the optimal protein level for green turtles was estimated as 40.6%. Findings from the current study support the use of artificial diets of specific protein levels to rear captive green turtle before release to natural habitats.

Dietary discrimination using a dual-choice self-feeding system in seabream (Sparus aurata)

Self-feeding systems have been extensively used to study animal behaviour and food preferences in vertebrates. In this study, we used a dual-choice self-feeding system to explore feeding behaviour and dietary discrimination based on organoleptic cues. Experimental tanks were provided with 2 self-feeders activated by string sensors and connected to a computer system. In the first experiment (E1) [6 tanks, 10 animals/tank, body weight (BW) 266 g ± 19.4 g], both feeders delivered the same control standard diet to evaluate the potential preference for one feeder. E1 had 3 phases: 1st, animals were allowed to demand from both feeders; 2nd, from only one feeder and 3rd from both feeders again. The second experiment (E2) (11 tanks, 15 animals/tank, BW range 25–50 g) examined whether seabream can discriminate between 3 isoenergetic diets: the control diet; a positive/palatable diet containing high levels of fish, squid and krill meal; and a negative diet in which 1.5% quinine hydrochloride was added to the control diet. E2 had 3 phases: 1st acclimation with control diet; 2nd dual-choice; 3rd dual-choice with reversal of feeders. The third experiment (E3) (8 tanks, 10 animals/tank, BW range 25-50 g) was performed using a single self-feeder per tank, with each tank being fed either control or quinine diet, to corroborate the aversive response to quinine in the absence of dietary choice. E1 demonstrated that animals demanded significantly less when only one feeder/sensor was available. E2 shows that seabream can easily discriminate a bitter compound (quinine) in the diet, showing negative preference (P < 0.05) in both phases, 2nd and 3rd. When no choice was available (E3), seabream equally demanded control or quinine diet, presumably driven by its energy requirements. However, the presence of the bitter substance increased feed refusals, 14.3% rejection of demanded feed in quinine diet, versus 2.6% in control diet, indicating a role of sensory systems in assessing food quality. A positive conditioning with a palatable diet was not effective and no positive choices were measured over a basal diet, although results were possibly influenced by the previous familiarization with the basal diet and by the experimental conditions (fast growing juveniles at high temperature). This poor dietary selection during active feeding periods could partly explain the easy adaptation of this species to substitution diets. Finally, results suggest that food intake is conditioned by agonistic behaviour in an age-dependent manner. The information will be useful for diet and feeding strategy design in seabream.

Transmission conditions for clear depiction of thoracic spine based on difference between reflection and scattering characteristics of medical ultrasound

In epidural anesthesia, it is difficult to specify the puncture position of the anesthesia needle. We have proposed an ultrasonic method to depict the thoracic spine using the different characteristics of reflection from bone and scattering from muscle tissue. In the present paper, we investigated the transmission aperture’s width of the ultrasound probe to emphasize the differences in the reflection and scattering characteristics. First, we determined the optimum transmission aperture’s width using a simulation experiment. Next, we measured reflection and scattering signals by changing the transmission aperture’s width in a water tank experiment and confirmed that the results corresponded to the simulations. However, as the transmission aperture’s width increased, the lateral resolution at the focal point improved. Therefore, better imaging of the human thoracic vertebrae can be achieved by selecting the transmission aperture’s width, which considers the effect on lateral resolution.