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Photoacoustic (PA) imaging is an emerging imaging technique for many clinical applications. One of the challenges posed by clinical translation is that imaging systems often rely on a finite-aperture transducer rather than a full tomography system. This results in imaging artifacts arising from an underdetermined reconstruction of the initial pressure distribution (IPD). Furthermore, clinical applications often require deep imaging, resulting in a low-signal-to-noise ratio for the acquired signal because of strong light attenuation in tissue. Conventional approaches to reconstruct the IPD, such as back projection and time-reversal, do not adequately suppress the artifacts and noise. We propose a sparsity-based optimization approach that improves the reconstruction of IPD in PA imaging with a linear array ultrasound transducer. In simulation studies, the forward model matrix was measured from k-Wave simulations, and the approach was applied to reconstruct simulated point objects and the Shepp-Logan phantom. The results were compared with the conventional back projection, time-reversal approach, frequency-domain reconstruction, and the iterative least-squares approaches. In experimental studies, the forward model of our imaging system is directly measured by scanning a graphite point source through the imaging field of view. Experimental images of graphite inclusions in tissue-mimicking phantoms are reconstructed and compared with the back projection and iterative least-squares approaches. Overall these results show that our proposed optimization approach can leverage the sparsity of the PA images to improve the reconstruction of the IPD and outperform the existing popular reconstruction approaches.

Purpose The combination of high-pressure air and TNT in shock tubes can effectively simulate real nuclear explosions and conventional weapon explosion shock waves. However, the explosion shock wave parameters are greatly affected by changes in the tube sections and the increase in the initial air pressure. Methods In this study, the propagation law of explosion shock waves in closed variable section tubes was studied first through theoretical analysis and explosion tests under five different high-pressure environments. Then, the influences of different initial pressures of 100–500 kPa on shock wave related parameters were analyzed by numerical simulation, the change curves of the shock wave overpressure peak and different initial pressures at different test points were fitted, and the change process of the pressure field in the tube was obtained. Finally, an engineering model that can attenuate the shock wave overpressure peak in high-pressure tube with variable section is established by dimensional analysis method. Results The results show that the attenuation coefficient of the shock wave decreases with an increasing cross section change rate and the related parameters of the shock wave increase with an increasing initial pressure. Compared with normal temperature and pressure, the maximum increase in the peak overpressure of the shock wave is 11.4%, the maximum increase in the arrival time is 94.2%, and the maximum increase in the impulse is 3.5%. Conclusion The conclusion of this study is that contracting the tube cross-section within the excitation tube driving section can effectively enhance the intensity of the shock wavefront. The combined high-pressure air and explosive driving method can effectively increase the energy of the driving section. Moreover, the higher the initial pressure of air, the higher the energy at the exit of the excitation tube. The results obtained can be used for simulation analysis of explosion shock waves.

The multi-stage pulse competition of pressurized pulsed water jet becomes the initial pulse at the head tip, and hydraulic parameters are the key parameters that affect the characteristics of multiple pulses. Based on the ultra-high-speed imaging system, a pressurized pulsed water jet flow field capture system was constructed, and the effects of initial pressure and driving pressure of the pressurized chamber on the characteristics of multi-stage pulses were studied. The experimental results show that as the initial pressure of the booster chamber increases, the jet changes from a discontinuous state to a continuous state, and the multi-level pulse simultaneously changes from dominant multi-pulse to implicit multi-pulse; as the driving pressure increases, the initial spacing between the first pulse and the second pulse increases, and the peak velocity of the initial pulse gradually increases. At the same time, the location of the peak velocity also shifts away from the nozzle as the driving pressure increases. In addition, the peak velocity of the initial pulse is relatively close to the theoretical velocity of the continuous jet under driving pressure conditions.

This study investigates the combustion behavior of hydrogen–air mixtures in a closed chamber at reduced initial pressure, focusing on applications in thermal energy methods (TEMs) for plastic processing. The primary goal was to develop and validate a numerical model capable of accurately predicting pressure and temperature profiles over time. By employing ANSYS Fluent 2024 R2 and the GRI-Mech 3.0 mechanism, a detailed combustion model was constructed and validated against experimental data, adhering to the standards outlined in EN 15967: 2011. Subsequent simulations under low-pressure conditions revealed consistent flame front propagation and turbulent flow patterns, crucial factors for achieving stable temperature distributions and optimal part placement. This validated model provides a valuable tool for predicting combustion effects, enhancing safety, and optimizing the performance of hydrogen-fueled TEM processes. By leveraging hydrogen as a clean and sustainable energy source, this research contributes to a more environmentally friendly approach to plastic processing. Future studies will delve into the combustion of hydrogen–air mixtures in the presence of plastic parts to further refine the efficiency and effectiveness of TEM processes.

The dip angle of coal seam in Guanyinshan coal mine is between 32° and 39° and the first mining area is X11 and X12. According to the caving degree of the immediate roof in the gob, the intensity of pressure of the main roof is analyzed, and the dynamic load coefficient of the main roof is small. The three-dimensional simulation software FLAC is used to calculate the distance of initial caving and distance of initial pressure of working face. The initial caving distance of the immediate roof at each part of the working face is about 4 m, and the initial pressure distance of main roof is about 20 m on average. This paper analyzes the caving of the main roof: when the distance of initial pressure is 20 m, the caving height of the main roof is about 4 m; when it is pushed to 30 m, the caving height of the main roof is about 10 m; with the continuous mining of the working face, the caving height of the main roof is also increasing, when it is pushed to 90 m, the caving height of the main roof reaches 18 m. Through the analysis of the regular of underground pressure in large dip angle soft roof and floor coal seam mining, it can guide the production.

Porous adsorption materials have been used to promote hydrate formation in the development of hydrate-based technology. In this study, the effect of ZIF-8 suspensions on the formation kinetic of methane hydrate was investigated systematically. The experimental results show that the presence of ZIF-8 suspensions can effectively reduce the induction time of methane hydrate formation, and the higher the amount of addition, the shorter the induction time. We found the transition mechanism of inhibition-promotion effect of ZIF-8. At low pressure, gas adsorption and hydrate formation compete to capture the dissolved methane, limiting the further hydrate growth. At high pressure, the gas consumption rates are determined by the hydrate formation in bulk phase at the early stage. When the mass transfer resistance is large, conversion of adsorbed gas provides additional source for hydrate formation. The promotion effect of ZIF-8 on hydrate formation emerges at the initial pressure of 6.5MPa, and the methane gas consumption increases significantly with the increase of ZIF-8 addition.

The support systems of excavations (such as underground mining openings and water tunnels) experience the time dependent induced pressure of the ground in vicinity of swellable rock. This research examines the interaction of swellable rock under different initial pressure to simulate the behavior of such rocks behind the support systems. A device was designed and constructed to model the condition in laboratory. Marlstone samples from Marash project in North West of Iran were chosen to perform the tests. The swelling pressure under different initial support pressure (ISP) was measured over time. The lowest swelling pressure was recorded under the minimum initial pressure. The swelling pressure of samples do not expose under high ISP (about 5 times of the steady swelling pressure). The differential swelling pressure (swelling pressure minus the ISP) generally increases from a minimum, at the lowest initial pressure, to a maximum, at the initial pressure equal to the steady swelling pressure. After reaching this maximum value, the differential pressure reduces back to zero where the ISP hampers the swelling phenomenon.

Based on the working principles of high-pressure pneumatic pilot-operated valve (HPPV) and compressed air ejection device, a multi-physics simulation model of the compressed air ejection device considering pneumatic, mechanical, and leakage factors was established in AMEsim. A compressed air ejection test platform was also constructed to conduct unloaded tests. The validated simulation model investigated the impact of different initial parameters on the dynamic characteristics of the HPPV during the compressed air ejection process. The results demonstrate that the multi-physics simulation model of the coupled valve opening and closing exhibits high computational accuracy. During the compressed air ejection process, the dynamic characteristics of the HPPV still meet the requirements of the compressed air ejection device, effectively preventing ineffective gas leakage. The initial pressure of the ejection gas source and the supply pressure driving the HPPV significantly influence the dynamic characteristics of the valve during the compressed air ejection process.

A carbon dioxide power device is a high-potential gas power device. In order to study the effect of carbon dioxide pressure and flow state in the phase change chamber on the change law of load motion in a gas power device, the pressure before and after the load is read by the user-defined function in the simulation software. The motion change law of the load in the gun barrel is simulated by the dynamic grid technology to the initial pressure of different phase change chambers. The motion change law of the load with time and displacement is as follows: with the increase of the pressure in the phase change chamber, the exit velocity of the load approaches a linear change and gradually approaches the theoretical simulation calculation results. Afterwards, the feasibility of the calculation method and the correctness of the calculation results are verified by comparing the experimental and simulation results. Finally, the influence of the diameter of the phase change chamber on the work capacity of carbon dioxide is analyzed.

The interplay between seismic activity and fluid flow is essential during the evolution of hydrothermal systems. Although earthquakes can trigger transient fluid flow and phase changes in dilational jogs, the temporal scale and the geologic conditions that enhance such process are poorly quantified. Here, we use numerical simulations of deformation and fluid flow to constrain the conditions that maximize adiabatic boiling—referred to as flashing—and estimate the extent and duration of such process. We show that there is an optimal geometry for a dilational jog that maximizes co‐seismic flashing within the jog. Fluid flow simulations indicate that the duration, intensity, and propagation of the flashing front are limited and highly dependent on the magnitude of the co‐seismic slip and the initial pressure‐enthalpy conditions. Our results are valuable to better understand the implications of pressure fluctuations during the seismogenic cycle, as well the mineralization processes in the Earth's crust. Plain Language Summary Earthquakes can strongly affect circulating fluids within the Earth's crust, mainly where faults bend or split into different fault segments and produce dilatant areas. In these areas, earthquakes play an important role in forming ore deposits, because the co‐seismic volume change can produce a pressure drop that drives boiling with gas exsolution and subsequent mineralization. This process, in which boiling is triggered by a pressure drop rather than a temperature rise, is called flash vapourization or flashing. Here, we used a computer code to unravel scenarios where optimal geometry and pressure‐temperature conditions maximize flash vapourization. Furthermore, we found that the duration and extension of the flashing event are limited and highly dependent on the magnitude of the triggering earthquake and the physico‐chemical conditions of the system. Such results are valuable for assessing the implications of pressure fluctuations during the seismogenic cycle and for better understanding mineralization processes in the Earth's crust. Key Points We use numerical simulations to constrain the intensity and temporal scale of co‐seismic flash vapourization or flashing triggered by earthquakes We found an optimal geometry of a dilational jog that maximizes co‐seismic flashing within the jogs Under optimal conditions, the flashing front propagates up to 1 m away from the dilational jog and persists for almost 3 hr