Test Tank Research Articles

Glucosyl hesperidin exhibits more potent anxiolytic activity than hesperidin accompanied by the attenuation of noradrenaline induction in a zebrafish model.

Anxiety is a symptom of various mental disorders, including depression. Severe anxiety can significantly affect the quality of life. Hesperidin (Hes), a flavonoid found in the peel of citrus fruits, reportedly has various functional properties, one of which is its ability to relieve acute and chronic stress. However, Hes is insoluble in water, resulting in a low absorption rate in the body and low bioavailability. Glucosyl hesperidin (GHes) is produced by adding one glucose molecule to hesperidin. Its water solubility is significantly higher than that of Hes, which is expected to improve its absorption into the body and enhance its effects. However, its efficacy in alleviating anxiety has not yet been investigated. Therefore, in this study, the anxiolytic effects of GHes were examined in a zebrafish model of anxiety. Long-term administration of diets supplemented with GHes did not cause any toxicity in the zebrafish. In the novel tank test, zebrafish in the control condition exhibited an anxious behavior called freezing, which was significantly suppressed in GHes-fed zebrafish. In the black-white preference test, which also induces visual stress, GHes-fed zebrafish showed significantly increased swimming time in the white side area. Furthermore, in tactile (low water-level stress) and olfactory-mediated stress (alarm substance administration test) tests, GHes suppressed anxious behavior, and these effects were stronger than those of Hes. Increased noradrenaline levels in the brain generally cause freezing; however, in zebrafish treated with GHes, the amount of noradrenaline after stress was lower than that in the control group. Activation of c-fos/ERK/Th, which is upstream of the noradrenaline synthesis pathway, was also suppressed, while activation of the CREB/BDNF system, which is vital for neuroprotective effects, was significantly increased. These results indicate that GHes has a more potent anxiolytic effect than Hes in vivo, which may have potential applications in drug discovery and functional food development.

Sparse Bayesian Relevance Vector Machine Identification Modeling and Its Application to Ship Maneuvering Motion Prediction

In order to establish a sparse and accurate ship motion prediction model, a novel Bayesian probability prediction model based on relevance vector machine (RVM) was proposed for nonparametric modeling. The sparsity, effectiveness, and generalization of RVM were verified from two aspects: (1) the processed Sinc function dataset, and (2) the tank test dataset of the KRISO container ship (KCS) model. The KCS was taken as the main research plant, and the motion prediction models of KCS were obtained. The ε-support vector regression and υ-support vector regression were taken as the compared algorithms. The sparsity, effectiveness, and generalization of the three algorithms were analyzed. According to the trained prediction models of the three algorithms, the number of relevance vectors was compared with the number of support vectors. From the prediction results of the Sinc function and tank test datasets, the highest percentage of relevance vectors in the trained sample was below 17%. The final prediction results indicated that the proposed nonparametric models had good prediction performance. They could ensure good sparsity while ensuring high prediction accuracy. Compared with the SVR, the prediction accuracy can be improved by more than 14.04%, and the time consumption was also relatively lower. A training model with good sparsity can reduce prediction time. This is essential for the online prediction of ship motion.

Effect of Lactobacillus rhamnosus and Diclofenac with Curcumin for Neuronal Restoration and Repair Against Scopolamine Induced Dementia in Zebrafish (Danio rerio)

Background: Clinical studies have already revealed the ubiquitous neuroprotective role of curcumin in neuronal deterioration, but it cannot be used alone due to its truncated bioavailability. Currently, many such approaches are functional, which overcome this issue either by increasing the solubility or absorption. These approaches carry a costlier treatment. One more tactic is present but less focused i.e., by limiting the intestine and liver enzymatic metabolism; by this approach, curcumin will be more available for its beneficial outcome. Objective: The goal of this study was to evaluate the impact of Lactobacillus rhamnosus and diclofenac on the neuroprotective effects of curcumin against scopolamine-induced dementia. Methods: Physical parameters involved a novel tank test, T maze test, whereas neurochemical parameters include brain oxidative stress and acetylcholinesterase (Ache) inhibition activity in a zebrafish dementia model. Results: Our results demonstrated that curcumin with Lactobacillus rhamnosus and diclofenac significantly (p<0.05) reduced anxiety, memory deficits, and brain oxidative stress compared to the alone curcumin- treated group. Conclusion: This result approves that curcumin with L.rhamnosus and diclofenac have superior activity compared to curcumin alone. However, further clinical studies are needed to validate these findings.

Vasotocin expression is associated with social preference development of the medaka fish

The neurohypophysial peptide arginine vasotocin (VT) and its mammalian ortholog, arginine vasopressin, function in physiological and behavioral events. These functions have been identified in neuroendocrinological studies using adult animals; however, there is little information on whether VT is associated with social behavior development in fish. Here, we examined social preference in medaka fish of various ages and investigated how VT expression changes during development. The 1-, 2-, 4-, and 8-week post-hatching (wph) larvae, juveniles, and 5-month-old adults were individually introduced to the grouped fish of each age group, and the social preference index (SPI) was compared among ages based on the time spent in the interaction zone near the grouped fish in a test tank. The SPI was significantly higher in the 4-wph larvae, 8-wph juveniles, and adult fish than in the 1- and 2-wph larvae. VT expression increased with age from 1 to 4 wph. Similarly, the expression was high in 4-wph, 8-wph, and adult fish. Furthermore, it was also found that the SPI and the VT expression decreased in the socially isolated larva during the 4 weeks after hatching compared to the levels in the grouped 4-wph larvae. These findings suggest that social preference develops with age and that conspecifics are necessary for social development in medaka larvae. Furthermore, our results suggest that VT is associated with the development of social preferences in medaka.

Ship motions and unsteady pressures on ship hull in oblique waves estimated by potential-based solvers

The seakeeping performances in oblique wave conditions, such as ship motions and unsteady pressures on a ship hull, are getting more important, recently. These physical quantities are used for estimating loads induced by waves and evaluating the safety of a ship. Thanks to the evaluation of various incident wave angles, a rational ship design with sufficient safety and less construction cost can be realized. Therefore, the estimation by numerical schemes in those conditions is demanded for the ship design. However, schemes were usually validated through the comparison with experimental data in only heading wave conditions because few towing tanks can carry out the experiment for a ship advancing in oblique waves. The computed results in oblique waves should be validated well before the industrial usage of schemes. Although Computational Fluid Dynamics is useful to know the seakeeping performance in oblique waves thanks to the development of computer performance in these years, it takes much longer time than the schemes based on a potential theory. For this reason, three solvers based on the potential theory, the Salvesen-Tuck-Faltinsen method, the Green function method, and the Rankine panel method, are validated by comparing ship motions and unsteady pressure on the ship hull obtained from towing tank tests in oblique wave conditions.

Experimental Study on the Ice Resistance of a Naval Surface Ship with a Non-Icebreaking Bow

With the shrinking of Arctic sea ice due to global climate change, potential access to Arctic waters has increased for non-typical icebreaking or strengthened ships. Numerous studies have been conducted on hull form designs and ice resistance predictions for ships with typical icebreaking bows, but published research for ships with non-icebreaking bows in ice is still rare. The objective of this study was to investigate the ice resistance of a naval surface ship with a non-icebreaking bow through model tests in an ice tank. The naval surface combatant concept DTMB 5415 was used as the ship model. The tests were conducted under different levels of ice thicknesses and speeds. During the tests, the total resistance of the model ship was measured, accompanied by monitoring of the ice load at the stem area with a flexible tactile sensor sheet. Compared with the test results of icebreaker models in former studies, the total ice resistance, as well as the stem ice load, of the present ship was significantly higher. The ice crushing resistance component in the stem area accounted for more than 60% of the total resistance in the ice. Discussions on the applicability of a semi-empirical formula for predicting the ice resistance of the present ship are also presented. Keinonen’s formula was found to be relatively more consistent with the predictions produced by model tests, and a preliminary modification was proposed to obtain more accurate predictions.

Underwater Acoustic Intensity Analysis using Noise Assisted-MEMD with Varying Distances

With current developments, underwater communication using acoustic signals is widely used. Many things need to be prepared to support a reliable underwater communication system, such as taking measurements in a test tank to find out the correct measurement configuration. Underwater acoustic intensity measurements, which are detailed in this paper, are performed in the test tank using distance variation schemes. Measurements were made at various distances of 4, 10, 20, and 50 meters from the signal source. The hydrophone that was used has a sensitivity of -180 dB re 1V/µPa. The hydrophone was placed at a depth of 2 meters below the surface of the water in the test tank, which divided the test tank depth in half to ensure that reflections from the bottom and the surface were kept to a minimum. However, the problem is that there are noisy signals at different frequencies. This paper proposes a method using Noise Assisted - Multivariate Empirical Mode Decomposition (NA-MEMD) to decompose the signal and then calculate the sound intensity. The result shows that an increase in the distance between the transmitter and receiver, also causes a change in the intensity with an average change of 0.467 dB/meter. It is concluded that the NA-MEMD approach was shown to be successful in decomposing the intended signal from the noise to equalize the quality of the signal received at different distances, and the correlation between intensity value and change in distance is resilient, with a correlation value of 0.98, indicating a very strong correlation.

Numerical investigation of a Wave-Powered Vertical Profiler

The wave-power vertical profiler harvests surface wave energy through a buoy, and the converts the wave energy into a kinetic energy of a vehicle (underwater vehicle with sensors for profiling) via a mooring cable. The vehicle is aided by a unidirectional motion mechanism to submerge and surface in water. In this paper, a numerical simulation method is proposed to analyze the motion characteristics of the wave-power vertical profiler and reconstruct the entire moving process.Firstly, numerical work is conducted using Ansys Fluent software to investigate the response of the buoy to Stokes waves of different heights. Secondly, the relationship between the underwater vehicle's motion velocity and fluid resistance are studied. Finally, the numerical simulation results are combined using Matlab software to reconstruct the motion process and draw corresponding curves. Compared with the results from the water tank tests, our method can effectively reconstruct the vehicle's motion, with an accuracy rate of 96.5% in simulating the velocity values during the surfacing phase and a good match with the experimental results under natural sea conditions. We found that wave height is the determining factor for the vehicle's sinking time; the weight of the counterweight affects the vehicle's maximum sinking speed; the vehicle's net buoyancy and drag coefficient determine its surfacing speed, while the weight of the buoy can be ignored. Based on these conclusions, we recommend a counterweight weight of 100 N when the wave height is less than 0.6 m and an increase in weight when it exceeds 0.6 m. The recommended net buoyancy value for the vehicle is between 10 and 40 N, and the recommended buoy weight is 65 kg. We hope that these findings will be helpful for the design of wave energy buoys.

Neurotoxicity of aluminium chloride and okadaic acid in zebrafish: Insights into Alzheimer's disease models through anxiety and locomotion testing, and acute toxicity assessment with Litsea garciae bark's methanolic extract

Alzheimer's disease (AD) is a complicated neurodegenerative disorder that presents significant challenges for the development of effective therapeutic interventions. Understanding disease mechanisms and exploring potential treatments require the use of animal models that accurately replicate the pathology of AD. In this study, we investigated the potential of two neurotoxin inducers, aluminium chloride (AlCl3) and okadaic acid (OKA), to validate the zebrafish as a model organism for AD. AD can impact locomotor activity and induce anxiety-like behaviors. To assess these behaviors, a 6-minute novel tank test was conducted. Zebrafish were administered with low, medium, or high doses of neurotoxic agent (AlCl3 or OKA) intraperitoneally twice weekly for 21 days. Behavioral activities were recorded at three time points: day 7 (short duration), day 14 (moderate duration), and day 21 (extended duration). The behavioral task required the evaluation of four endpoints. Methanolic extract of Litsea garciae bark was selected as a potential plant for the treatment of AD in this study, based on its previously demonstrated antioxidant effect. However, the acute toxicity of this plant has not been previously assessed. Therefore, this research was aimed to investigate the acute toxicity of the L. garciae bark’s methanolic extract in adult zebrafish. The extract was immersed in a static system following OECD Test Guideline No. 203, and the acute toxicity test involved monitoring the adult zebrafish for 96 h for any deaths or apparent abnormalities. Regarding the behavioural task, the groups induced with 100 nM of OKA demonstrated significant differences in all measured parameters compared to the control group at the 21-day time point. In contrast, none of the parameters were significantly different between the AlCl3-induced groups and the control group at any of the three time points (7, 14, or 21 days). Regarding acute toxicity, neither the test group (100 mg/L) nor the control group recorded any deaths or abnormalities. Therefore, no LC50 value could be determined. These findings confirm the acceptance of OKA as an inducer in the zebrafish model of AD and highlight the significance of the safe and non-toxic nature of L. garciae bark's methanolic extract for future ethnopharmacological investigations.

The wave energy converter control competition (WECCCOMP): Wave energy control algorithms compared in both simulation and tank testing

The wave energy control competition established a benchmark problem which was offered as an open challenge to the wave energy system control community. The competition had two stages: In the first stage, competitors used a standard wave energy simulation platform (WEC-Sim) to evaluate their controllers while, in the second stage, competitors were invited to test their controllers in a real-time implementation on a prototype system in a wave tank. The performance function used was based on converted energy across a range of standard sea states, but also included aspects related to economic performance, such as peak/average power, peak force, etc. This paper compares simulated and experimental results and, in particular, examines if the results obtained in a linear system simulation are borne out in reality. Overall, within the scope of the device tested, the range of sea states employed, and the performance metric used, the conclusion is that high-performance WEC controllers work well in practice, with good carry-over from simulation to experimentation. However, the availability of a good WEC mathematical model is deemed to be crucial.

The investigation of flocculation and deposition of heavy components in the crude oil tank based on experiment and molecular simulation

With the implementation of the “3060” carbon neutrality policy, the cancellation of external insulation has led to the increasingly serious deposition of heavy components in petroleum storage tanks. However, there are few studies on the flocculation and deposition behavior of industrial complex crude oil systems during the entire storage period in tanks. This study used an equivalent crude oil tank system to systematically investigate the flocculation and deposition behavior of industrial crude oil systems during storage. Static settling experiments were conducted for the entire storage period (32 days) to measure changes in oil parameters such as density, wax appearance temperature (WAT), gel point, and particle size at different heights in the tank. In addition, a full-component molecular system for crude oil was constructed, and molecular dynamics (MD) simulation was used to reveal the flocculation and aggregation mechanisms of heavy components in crude oil systems for the first time. The result showed that the maximum density difference between the upper and lower of the test tank is 14 kg/m3 and the marked stable time of sedimentation is 163 h. The maximum increment of the WAT appears at the bottom of the tank with the value increasing from 38.17 °C to 45.75 °C. The microscopic observations are consistent with the changes in macroscopic parameters. The wax is very prone to aggregation and wax crystals show a face-to-face sticking state. As for asphaltenes, the degree of aggregation is weaker than that of wax molecules, and the aggregation state mainly shows two manners: T-shape sticking and face-to-face sticking. This study can provide the theoretical basis for tackling the tank bottom sediment.

Zebra fish behavioral assessment by using Calycophyllum Spruceanum bark methanolic extract

In neurobehavioral research, animal model has played a crucial role in yielding experimental data as well as, in the development of new insights. Researchers are always trying to develop novel animal models to understand fundamental features of physiological, behavioral and psychological disorders. Zebra fish (Danio rerio) is now considered globally as a new and useful model in biomedical research. The objective of the present study was to assess behavioral changes in adult zebra fish after acute exposure to different pharmacological and herbal compound. Adult zebra fish of 4-5-months-old were exposed to different concentrations of unknown test drug with the standard for 5 min. The test was conducted separately for each drug concentration as well as control. Behavioral activity parameters viz. novel tank test and light and dark transition test were recorded for each animal during the exposure period. Results: Zebra fish exposed to Test drug (Calycophyllum Spruceanum) showed change in behavioral activity with significant to the standard drug caffeine. In view of the above findings, these results suggested that exposure of adult zebra fish with drug produce the expected changes in the behavior like stress and anxiety; therefore, adult zebra fish can be used an alternative approach for the assessment of new chemical entities for their effect on behavioral activity.Dark Transition Test.

Numerical study of hydrodynamic forces and dynamic response for barge type floating platform by computational fluid dynamics and engineering model

The hydrodynamic coefficients are evaluated by fully nonlinear Navier-Stokes forced oscillation simulations using the volume of fluid method. Richardson extrapolation is employed to obtain the grid-independent solution. The predicted hydrodynamic coefficients are validated by the water tank tests. The applicability of the drag coefficient models as the function of Keulegan-Carpenter numbers in the surge and heave directions are investigated for the barge-type floater by comparing with the numerically predicted drag coefficients. The dynamic response analyses are then conducted using the engineering model with the validated drag coefficient models. The predicted mean values of surge and mooring tension without considering drag forces underestimate the measurements in the high wave height condition, where those with considering drag forces show good agreement, which is analytically explained by the mean drag force being inversely proportional to the square of wave period and proportional to the cube of wave height. Dynamic responses of floater predicted without considering drag forces cause overestimation at the natural frequencies in the heave and pitch directions, while those considering drag forces show good agreement with the measurements.

Assessing the exploratory profile of two zebrafish populations: Influence of anxiety-like phenotypes and independent trials on homebase-related parameters and exploration

Anxiety is a protective behavior when animals face aversive conditions. The open field test (OFT) is used to assess the spatio-temporal dynamics of exploration, in which both homebase formation and recognition of environmental cues may reflect habituation to unfamiliar conditions. Because emotional- and affective-like states influence exploration patterns and mnemonic aspects, we aimed to verify whether the exploratory behaviors of two zebrafish populations showing distinct baselines of anxiety differ in two OFT sessions. Firstly, we assessed the baseline anxiety-like responses of short fin (SF) and leopard (LEO) populations using the novel tank test (NTT) and light-dark test (LDT) in 6-min trials. Fish were later tested in two consecutive days in the OFT, where the spatial occupancy and exploratory profile were analyzed for 30 min. In general, LEO showed pronounced diving behavior and scototaxis in the NTT and LDT, respectively, in which an “anxiety index” corroborated their exacerbated anxiety-like behavior. In the OFT, the SF population spent less time to establish the homebase in the 1st trial, while only LEO showed a markedly reduction in the latency to homebase formation in the 2nd trial. Both locomotion and homebase-related activities were decreased in the 2nd trial, in which animals also revealed increased occupancy in the center area of the apparatus. Moreover, we verified a significant percentage of homebase conservation for both populations, while only SF showed reduced the number of trips and increased the average length of trips. Principal component analyses revealed that distinct factors accounted for total variances between trials for each population tested. While homebase exploration was reduced in the 2nd trial for SF, an increased occupancy in the center area and hypolocomotion were the main factors that contribute to the effects observed in LEO during re-exposure to the OFT. In conclusion, our novel data support the homebase conservation in zebrafish subjected to independent OFT sessions, as well as corroborate a population-dependent effect on specific behavioral parameters related to exploration.

Modelling and Control Tank Testing Validation for Attenuator Type Wave Energy Converter - Part II: Linear Noncausal Optimal Control and Deterministic Sea Wave Prediction Tank Testing

Tank testing results from applying Linear non-causal optimal control (LNOC) to the Mocean M100 wave energy converter (WEC) are presented in this paper. Based on the two state-space models derived from Part I, two LNOC algorithms designed to increase power capture of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1/20$</tex-math></inline-formula> scaled M100 WEC prototype are tested separately in real-time under various irregular wave conditions. The deterministic sea wave prediction (DSWP) algorithm is employed to provide the required wave elevation/excitation force predictions for the LNOC using real-time wave measurements. Experimental data shows that the DSWP can predict the incoming waves with sufficiently high accuracy in various sea states. Compared with a well-tuned passive damper, LNOC based on a hydrodynamic model increases the power capture by up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$128\%$</tex-math></inline-formula> while LNOC based on a system identification (SysID) model increases the power capture by up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$323\%$</tex-math></inline-formula> . The technologies are transferrable. The testing procedure and the results also provide informative guidance for the tank testing of other advanced optimal controllers and their implementations on other types of WECs.

Modelling and Control Tank Testing Validation for Attenuator Type Wave Energy Converter - Part I: Experiment Setup and Control-Oriented Modelling

Advanced non-causal optimal control strategies have been demonstrated to significantly improve the energy output of a scale physical model of an attenuator type wave energy converter (WEC) by tank testing experiments using FloWave tank facilities in Edinburgh supported by Wave Energy Scotland's control project. The results are reported in a series of three papers, summarizing the tank testing setup, dynamic modelling, and validation of both linear non-causal optimal control (LNOC) and model predictive control (MPC) in regular and irregular waves. Compared with an optimally tuned passive damping control, both LNOC and MPC can significantly improve the energy output, by between 10% to 460%, using irregular waves with low to medium magnitude and peak periods ranging from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1.7~\mathrm{s}$</tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2.8~\mathrm{s}$</tex-math></inline-formula> at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1/20^{th}$</tex-math></inline-formula> scale, as shown in Part II and Part III papers. These controllers also show robust performance in spread waves and side waves which are normally encountered in real sea conditions. Furthermore, the control technologies can be transferred to other types of WECs. The results pave the way for the sea trial testing and full control system validation involving the electricity generation stage and power conditioning stage. This Part I paper will focus on the tank testing setup, the passive damping control experimental results, and the control-oriented models for the WEC. Two state-space models derived respectively from the hydrodynamic model and system identification of experimental data, are validated and compared for use on the controller designs to be presented in Part II and Part III.

A CO2 and H2O Gas Analyzer with Reduced Error due to Platform Motion

Abstract One long-standing technical problem affecting the accuracy of eddy correlation air–sea CO2 flux estimates has been motion contamination of the CO2 mixing-ratio measurement. This sensor-related problem is well known but its source remains unresolved. This report details an attempt to identify and reduce motion-induced error and to improve the infrared gas analyzer (IRGA) design. The key finding is that a large fraction of the motion sensitivity is associated with the detection approach common to most closed- and open-path IRGA employed today for CO2 and H2O measurements. A new prototype sensor was developed to both investigate and remedy the issue. Results in laboratory and deep-water tank tests show marked improvement. The prototype shows a factor of 4–10 reduction in CO2 error under typical at-sea buoy pitch and roll tilts in comparison with an off-the-shelf IRGA system. A similar noise reduction factor of 2–8 is observed in water vapor measurements. The range of platform tilt motion testing also helps to document motion-induced error characteristics of standard analyzers. Study implications are discussed including findings relevant to past field measurements and the promise for improved future flux measurements using similarly modified IRGA on moving ocean observing and aircraft platforms.

Fast Model Predictive Control System for Wave Energy Converters With Wave Tank Tests

At present, the mainstream solution for the control of wave energy converters (WECs), the model predictive control (MPC)-like method, faces a gap between simulation-based research and practical application. Two of the major difficulties are the online computation burden and the requirement of real-time wave information. In this study, a fast solving strategy is proposed at the level of quadratic programming (QP), where a tailored warm-start algorithm is designed and combined with an early stop technique. Simulations show that only one iteration of interior-point method (IPM) suffices to reach over 95% efficiency of the exact MPC, which significantly speeds up the computation. The fast strategy is then deployed on the real-time controller of a prototype WEC platform. During this implementation, the instantaneous wave force is estimated by a Kalman filter entirely based on the basic feedback signals: position, velocity, and the generator current, while future wave forces are predicted by an autoregressive model. The wave tank test confirms that the proposed fast MPC is capable of being executed at a high frequency, achieving stable operations within constraints, and reaching satisfactory energy efficiency under real wave-body interactions.

Modelling and Control Tank Testing Validation for Attenuator Type Wave Energy Converter – Part III: Model Predictive Control and Robustness Validation

Following the tank testing results of linear passive damping control and linear non-causal optimal control (LNOC) in the Part I and Part II papers, this paper presents further tank testing results focusing on two aspects: Firstly, a model predictive controller (MPC) is designed based on the model developed by system identification in Part I to optimally handle actuator saturation limits. The MPC control is demonstrated to significantly improve the energy output by 9.86% up to 463.42% compared with a well-tuned passive damper and can also outperform the LNOC presented in Part II in a range of irregular unidirectional waves. Secondly, the robustness of the MPC controller and the LNOC controller is validated in more realistic sea conditions when directional spreading waves and side waves are superimposed onto the dominant directional waves. The test results show that both MPC and LNOC can still significantly outperform the passive damping controller in all the sea conditions. These tank testing results pave a solid way for future sea trial testing of these advanced non-causal optimal control strategies developed for wave energy converters in sea trials.

Laboratory and modelling investigation on chemically stabilized native expansive soil as a CNS material

Expansive soils challenge the stability of several civil engineering structures. Because of the presence of Montmorillonite clay mineral, they have the inherent property of swelling and shrinking upon wetting and drying. Researchers proposed several ground improvement and foundation techniques to enchase the properties of these soils. Cushion materials, particularly Cohesive Non– Swelling (CNS) cushions, attracted the attention of civil engineers due to their simplicity and long-term stability. To avoid the problem of the non-availability of required soil, a technique is presented in this study to convert local expansive soils into suitable CNS materials via chemical stabilisation. The study uses clayey sand from the Tirupati region of Andhra Pradesh. Admixtures such as fly ash and lime chemically modify native soils into CNS materials. The effectiveness of these prepared CNS materials in reducing expansive soil heave is investigated using model test tanks. SEM and XRD analyses are also used to determine changes in soil microstructure. According to the findings, 5% lime and 20% fly ash are optimal for preparing CNS material. The microstructure of the stabilised soil revealed the formation of cementation compounds, which improved the strength of the native soil stabilization using fly ash.