Carbon Fibre Reinforced Polymer (CFRP) composites are extensively used in the Automotive industries due to their excellent structural and mechanical properties. However, the occurrence of porosity within these materials can significantly affect their performance and durability. Porosity, defined as void inclusion, often occurs during the manufacturing process for these materials. Even for small amounts of porosity, this defect can alter the composite’s mechanical properties by reducing its inter-laminar shear strength. It is therefore important to characterise and accurately map this defect, characterising the porosity distribution within CFRP layers. In this work, a Finite Element method that accounts for circular cross-section pores subjected to an ultrasound excitation is developed. This simulated data is then used to apply a Machine Learning (ML) technique such as Convolutional Neural Networks (CNN) to characterise the porosity within the CFRP sample. This technique leverages the capabilities of ML algorithms to analyse and interpret ultrasound data for porosity detection. By training the ML model on a dataset of ultrasound images and corresponding porosity measurements, the model can learn patterns and features indicative of porosity. Results obtained for the simulation data are presented and discussed. The application of CNN in processing ultrasound data has shown exceptional potentials in identifying and quantifying porosity. Results obtained after applying this technique to real ultrasound data measured with an immersion tank are also presented. CNN technique shows interesting capabilities for extracting defects such as porosity from complex ultrasound data. This work contributes to a vast project that aims at underpinning the design of more efficient composite structures.

There is an increasing interest in the use of 3D woven composites in applications that require improved strength-to-weight ratios. In addition, the use of these structures helps to reduce CO2 emissions. Woven composites offer many benefits including many possible architectures with high ratios of strain to failure. Woven composites are structures made by interlacing some continuous fibres (known as wefts) in one direction and other continuous fibres (known as warps) in a perpendicular direction. In the case of 3D woven composites, the third direction is reinforced by other continuous fibres known as binder. This study deals with the development of ultrasound inversion methods to characterize features in 3D woven composite materials. The study focuses on orthogonal weave-type only. Both theoretical (simulated) and measured data are analysed and used to calculate features such as the warps, wefts, and binder locations. The analytical-signal response, including the definition of three instantaneous parameters, is analysed and their capabilities to calculate the warp, weft and binder locations are demonstrated. These instantaneous parameters are the instantaneous amplitude, phase and frequency. The simulated data is obtained from a 3D time domain Finite Element model whereas the measured data is acquired from scanning a built specimen using an ultrasound immersion tank. The inversion techniques developed in this study can be extended to other 3D woven weave-types.

In 2014, we first noticed on high resolution seismic profiles acquired by a Teledyne high-resolution Chirp III subbottom profiler in the well-documented Stone Age settlement of Atlit-Yam, located off Israel’s Carmel coast irregular disturbances in the water column and we named it “haystacks”. We speculated if these disturbances could be related to the flint debitage (blades) documented at the flint workshop in the survey area. The ChirpIII instrument sweeps the frequency interval 2 kHz – 20 kHz and operate in two bands 2-8 and 8-20 KHz. Acoustic experiments in laboratory had previously shown that flint blades could exhibit resonance when exposed to certain frequencies (3–23 kHz, with the main area being 7–12 kHz). Acoustic modeling confirmed this and modelling showed that even flint debitage buried below 2 m of sand could resonance. In Demark practical ChirpIII (that sweep the frequency interval 2 kHz – 20 kHz) used on flint debitage and natural cracked flint placed at the seafloor showed that flint debitage produced “haystacks” on seismic profiles whereas the natural cracked flint did not. Test of buried debitage showed that it created resonance and produced “haystacks”. In the dredged part of the Svanemøllen Harbour, Copenhagen we by coincidence located “haystacks” while testing instrumentation setting. In the following three years, we recorded data on three days to outline the area where “haystacks” are present and to confirm that the “haystacks” were a permanent phenomenon. The interpretation of the seismic data reveal that the haystacks are related sub bottom areas characterized by shallow basins and rivers in a near coastal setting and that the “haystacks” are located at the rim of the basins or in the basins. In order to test if there was a correspondence between the “haystacks” and possible debitage 11 shallow vibrocores, with a max length of 1 m, were drilled below locations of “haystacks”. Based on the cores we found up to 36 cm of silt below the dredged seafloor before we reached a sandy cover of up to 80 cm representing part of the basin configuration. The sandy interval is underlain by till clay. Two cores centrally placed in the surveyed area confirmed the presence of man knapped flint at a depth of 80-90 cm below the sea floor. The Svanemøllen Harbour site is a hitherto unknown buried Stone Age settlement and this is the first time that such a site has been acoustically detected (Teledyne Chirp III) and verified by drilling. Acoustic modelling of the retrieved pieces of man knapped flint is carried out to confirm that the debitage can be brought to resonance. Due to the relative sea level rise a significant part of the submerged Stone Age sites must worldwide be expected to be buried in the seafloor sediments. This paper underlines the importance of the development of cost-effective methods for detecting such buried cultural deposits.

In order to mitigate greenhouse effect and promote carbon neutrality, Oxy-Fuel Combustion (OFC) technology implemented in the Internal Combustion Engine (ICE) has been an effective and promising approach to reduce or even eliminate CO2 emissions from the transportation sector. This research contributes novel insights into the effects of compression ratio (𝛿𝐶𝑅) and initial flame kernel radius (𝑅𝐹𝐾) on combustion characteristics and fuel economy of a Dual-Fuel Spark Ignition (DFSI) engine under OFC mode by a numerical method. The research results show that by increasing 𝛿𝐶𝑅 from 8.6 to 13.6, an apparent reduction can be seen in equivalent Brake Specific Fuel Consumption (BSFCE). The corresponding ignition delay (𝜃𝐹) has a reduction of 10 degrees, while combustion duration (𝜃𝐶) are relatively stable. Moreover, the maximum cylinder pressure (𝑃𝑚𝑎𝑥) has a rise of 8 bar and 20 bar at low load and mid-high load, respectively. By increasing 𝑅𝐹𝐾 from 0.2 mm to 1.2 mm, 𝑃𝑚𝑎𝑥 and 𝜑𝑃𝑚𝑎𝑥 each presents a monotonic trend of growth and advancement, respectively. The reduction of 𝜃𝐹 at low load and mid-high load is each 28.5 degrees and 34.9 degrees. In the meantime, both BSFCE and in-cylinder temperature show a low level of sensitivity. The research findings could provide valuable insights for enhancing the combustion performance and economy of DFSI engines under OFC mode to mitigate the greenhouse effect.

This paper addresses the observer-based controller design problem for nonlinear time-delayed systems under input saturation. The nonlinearities are supposed to satisfy the quasi-onesided Lipschitz condition, which is less conservative than the one-sided Lipschitz condition. Based on the nonlinear matrix inequalities, control law for nonlinear systems subject to input saturation, time delays, and unavailable states, some sufficient conditions have been developed for an augmented system containing the system state vector and the error vector to ensure the convergence of all states to zero. The paper used a decoupling approach to reduce the complexity of the corresponding observer and controller gain computations. Finally, the effectiveness of the developed results is validated using suitable examples.

Adiabatic Compressed Air Energy Storage (ACAES) is an energy storage technology that has the potential to play an important role in the transition to a predominantly renewables-driven net-zero energy system. However, it has not yet achieved the performance necessary to be widely deployed. In this paper, we undertake an exergy analysis of isobaric and isochoric ACAES systems, tracking lost work through the components and exploring the influences of different design choices. We model three different configurations: (1) 3 compression and 3 expansion stages; (2) 4 compression and 2 expansion stages; (3) 2 compression and 4 expansion stages. Our results illustrate that isobaric systems are likely to have higher round trip efficiency and significantly higher energy density, at the cost of achieving isobaric storage. Exergy analysis reveals that most of the losses arise in the compressors, compressor aftercoolers and expanders. Losses in aftercoolers are exaggerated when compressors operate with high pressure ratios, emphasizing that choice of TES is a key system variable. With pressurised water as the coolant and TES fluid, it seems likely that the best system will have more compression than expansion stages. Increasing the number of compression stages decreases the off-design penalty when the system is isochoric.

Recent theoretical studies have predicted that adiabatic compressed air energy storage (ACAES) can be an effective energy storage option in the future. However, major experimental projects and commercial ventures have so far failed to yield any viable prototypes. Here we explore the underlying reasons behind this failure. By developing an analytical idealized model of a typical ACAES design, we derive a design-dependent efficiency limit for a system with hypothetical, perfect components. This previously overlooked limit, equal to 93.6% under continuous cycling for a typical design, arises from irreversibility associated with the transient pressure in the system. Although the exact value is design dependent, the methodology we present for finding the limit is applicable for a wide range of designs. Turning to real systems, the limit alone does not fully explain the failure of practical ACAES research. However, reviewing the available evidence alongside our analytical model, we reason that underestimation of th

This study deals with the sound absorption for Micro-Perforated Panels (MPP) as an effective solution for sound reduction. Single and multiple MPPs backed by an air cavity are presented, analysed, and both their behaviour and response are modelled and measured. The experimental setup relies on the use of an impedance tube. Three MPP samples were fabricated for this study: two MPP samples are made of Aluminium and one sample is polymer-made to analyse the contribution of the panel vibration to the overall sound absorption. To support the analysis, two models are presented: a model based on the acoustic propagation in short and narrow tubes and a model based on the equivalent fluid. Both models are compared to the experimental data and discussed. The theory considers no interactions between the holes. It is particularly showed that the sound absorption in the low-frequency ranges can be enhanced by using the combined effects of multiple MPPs and their vibrational effects. Relatively good agreement is also obser

This chapter explores the critical role of thermal energy storage in the context of solar, geothermal, and hydrogen energy. It emphasizes the imperative of sustainable development and environmental preservation by harnessing renewable resources. Renewable energy sources, including solar, geothermal, and hydrogen energy, are investigated for their potential to reduce greenhouse gas emissions, bolster energy security, and stimulate economic growth. This chapter underscores the substantial growth observed in renewable energy utilization, particularly in 2020, signifying a global shift toward cleaner energy alternatives. Technological advancements in energy capture and storage, together with the increasing global adoption of Net Zero strategies, have significantly expanded renewable and green energy production. These advances span from small-scale solar panel installations to vast offshore wind farms, innovative geothermal applications, and electricity generation through hydrogen.

Due to their high strength-to-weight ratio, composite materials are now in use in many high-stress applications, particularly where light weight is also a requirement. In these situations, the detrimental knock-down in mechanical strength due to an out-of-plane wrinkle defect can have serious consequences and is the reason for a requirement to rapidly detect any such wrinkles at manufacture. Unfortunately, current ultrasonic inspection techniques used for quality control at manufacture are not sensitive enough to detect these wrinkles above coherent structural noise variations. This paper exploits the ply resonance that is a characteristic of multi-layer structures to generate two new metrics for both detection and classification of out-of-plane wrinkles, due to their perturbations of the ply spacing. These can be measured at every location on a structure using the instantaneous frequency, which is the rate of change of phase in the pulse-echo ultrasonic response. The proposed two new metrics for detection an