Large Pressure Research Articles

Empowering CO2 Eco-Refrigeration With Colossal Breathing-Caloric-Like Effects in MOF-508b.

Today, ≈20% of the electric consumption is devoted to refrigeration; while, ≈50% of the final energy is dedicated to heating applications. In this scenario, many cooling devices and heat-pumps are transitioning toward the use of CO2 as an eco-friendly refrigerant, favoring carbon circular economy. Nevertheless, CO2 still has some limitations, such as large operating pressures (70-150bar) and a critical point at 31 °C, which compromises efficiency and increases technological complexity. Very recently, an innovative breathing-caloric mechanism in the MIL-53(Al) compound is reported, which implies gas adsorption under CO2 pressurization boosted by structural transitions and which overcomes the limitations of stand-alone CO2. Here, the breathing-caloric-like effects of MOF-508b are reported, surpassing by 40% those of MIL-53(Al). Moreover, the first thermometry device operating at room temperature and under the application of only 26bar of CO2 is presented. Under those conditions, this material presents values of ΔT ≈ 30K, reaching heating temperatures of 56 °C and cooling temperatures of -10 °C, which are already useful for space heating, air-conditioning, food refrigeration, and freezing applications.

Efficient thermal management of high-power electronics via jet-enhanced HU-type manifold microchannel

To efficiently remove the increasingly higher heat fluxes from electronic chips, this numerical study presents an embedded single-phase water-cooled heat sink which consists of a microchannel layer and a jet-enhanced HU-type manifold layer. The manifold features two liquid inlet plenums symmetrically positioned on two opposite sides and some outlets arranged in the middle. In order to reduce the average thermal resistance, the fluid impinging velocity is boosted by narrowing the manifold channel inlet. However, narrower inlet also leads to flow maldistribution which increases the maximum thermal resistance. To address this problem, we demonstrate two approaches: either adding a flat plate at the manifold outlet or adjusting the manifold channel walls to form a tapered pathway. Further, the impact of the plenum and manifold channel inlet profiles on fluid flow and heat transfer is investigated. Negligible difference is found between rectangular and trapezoidal plenums. As to the manifold channel inlet, although similar heat transfer performance is obtained with different shapes, the total pressure drop can be substantially different. To reduce the large pressure drop at the inlet, a semicircular or triangular inlet profile is preferred, instead of a rectangular one. Quantitatively, we show that for a 3 × 3 mm2 heated area, our heat sink can dissipate fluxes up to 2000 W cm−2 with a maximum temperature rise of 65 K and a pressure drop below 40 kPa, which represents one of the highest performances and energy efficiencies reported to date.

(Digital Presentation) Designing New Complex Hydrides Based on Transition Metals for Hydrogen Storage Applications

The widespread implementation of the hydrogen economy demands access to materials with a high weight percentage of hydrogen. Mg-based hydrogen storage alloys have become a research hot-spot in recent years owing to their high hydrogen storage capacity, good reversibility of hydrogen absorption/desorption, low cost, and abundant resources. However, high decomposition temperature of Mg-based hydrideslimits their practical usage. Hydrogen is lightest of all elements, typically it need large volumes or high pressures to store appreciable amount of hydrogen.To overcome these challenges research activities are currently going on metal hydrides and complex hydrides based on transition metal. The main challenges come when endothermic decomposition enthalpy is considered. It becomes difficult to release the hydrogen at ambient thermodynamic conditions. On the other hand, the meta-stable hydrides are characterized by a low reaction enthalpy and a decomposition reaction that is thermodynamically favourable under the ambient conditions. The good kinetics along with evolution of hydrogen around the room temperature possessed by these materials offer much promise for underground storage and it can be used as a grid energy.The present research specifically focus on transition metal based complex hydrides such as NaMgMnH6 and NaMgFeH6 for hydrogen storage and especially predicted the crystal structure of the same using VASP simulation package. ABCX6 and AB2X6 were taken as reference composition A,B,C and X were substituted with Na, Mg, transition metals(Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu) and H, respectively.From the ICSD database search the corresponding structural variants were considered as trial structure to predict the ground state structure of these newly designed compounds. using the predicted ground state structure for these compounds, important properties like formation energy, hydrogen site energy, partial density of states(pDOS), electron density(ED), Mulliken effective charge(MEC), Bader electron charge(BEC), Born effective charge, ELF and COHP were calculated. the calculated properties of these compounds were compared with the well known reference compounds. We found that both NaMgMnH6 and NaMgFeH6 are stable with negative formation energy and als othey are semiconductors with the band gap value of 0.51eV and 1.01 eV, respectively. from the calculated electronic structure we found that both these materials are having indirect band behaviour. Analysing the electronic density of states, charge density and various charges mentioned above the chemical bonding behaviour was established as iono-covalent in nature. from the force as well as stress minimisation considering 53 structural variants as input the ground state structure, its space group, equilibrium lattice parameters and atom positions are listed. Also from the energy vs. volume curve for the ground state structure, the equilibrium volume, bulk modulus and pressure derivatives were found out. Among NaMgMnH6 and NaMgFeH6 our spin polarised calculation show that NaMgMnH6 is possesing spontaneous magnetic polarisation with substantial magnetic moment at the Mn site. Among the considered paramagnetic, ferromagnetic, as well as A-, C-,and G- antiferromagnetic configurations the G type antiferromagnetic configuration is found to be the ground state for NaMgMnH6.

(Battery Division Early Career Award Sponsored by Neware Technology Limited) Understanding Interfacial Mechanisms that Govern Performance in Solid-State Batteries

Solid-state batteries offer the promise of improved energy density and safety compared to lithium-ion batteries. Here, I will present our emerging understanding of the key differences between how high-capacity anode materials behave in solid-state batteries compared to in conventional liquid-electrolyte batteries. The electro-chemo-mechanical evolution of materials at solid-solid electrochemical interfaces is different than at solid/liquid interfaces, and contact evolution in particular plays a critical role in determining the behavior of solid-state batteries. I will focus on mechanisms governing lithium metal anodes (including lithium in the “anode-free” configuration) and alloy anodes. Lithium metal anodes in solid-state batteries are intrinsically limited by void formation during stripping and dendrite growth during plating. Anode-free solid-state batteries, in which there is no initial lithium metal at the anode interface, offer extremely high energy density, but there is a lack of understanding of how their behavior differs from excess-lithium electrodes. Using X-ray tomography, cryo-FIB, and finite-element modeling, we show that anode-free solid-state batteries are intrinsically limited by current concentrations at the end of stripping due to localized lithium depletion. This causes accelerated short circuiting compared to lithium-excess cells. Based on these results, the beneficial influence of metal alloy interfacial layers on controlling lithium evolution and mitigating contact loss from localized lithium depletion, including at low stack pressures, will be discussed. X-ray tomography is further shown to be particularly useful in observing the dynamic evolution of lithium metal, including void formation and filament growth. The second part of the talk focuses on alloy anodes. Alloy anodes typically exhibit fast capacity decay in lithium-ion batteries because of excessive solid-electrolyte interphase growth. We show that alloy anodes in solid-state batteries can exhibit improved interfacial stability and enhanced cyclability. Furthermore, in situ measurement of stack pressure evolution during cycling shows that the volume changes of alloy anodes can lead to large pressure swings within the cell, giving insight into electrode composite evolution. Based on these insights, we present a new design for dense foil alloy anodes. This design offers a paradigm that does away with slurry coating, potentially reducing manufacturing costs. Taken together, these findings show the importance of controlling chemo-mechanics and interfaces in solid-state batteries for improved energy storage capabilities.

Online Electrochemical Mass Spectrometry on Large-Format Li-Ion Cells

Significant progress has been made in real-time analysis methodologies for batteries, particularly with regards to the development of Operando Electrochemical Mass Spectrometry (OEMS) [1]. OEMS provides unprecedented selectivity and sensitivity in analysing the release of volatile species, enabling the detection of side reactions during battery cycling which can provide crucial information about the Solid Electrolyte Interface (SEI) and processes that limit battery life. However, most research thus far has been conducted on model battery systems (~1 mAh) that do not accurately reflect conditions within large-format commercial cells (~10,000 mAh) particularly in terms of electrode areas, electrolyte volumes, and stack pressures. Additionally, the atmosphere within the cell is altered through either continuous flow [2] [3] (in the open approach) or purging [4] (in the semi-closed approach [5]). In both cases, gas is being withdrawn from the cell (10% of cell volume/measurement point) during operation and replaced with a carrier gas (usually Ar). This dilutes the existing environment and prevents further reactions, making it difficult to compare the results to real-life situations.In this work, the development and validation of an entirely closed OEMS system that can be interfaced with large-format commercially available batteries is showcased. Instead of replacing the removed gas, a small amount (0.2 % of cell volume/measurement point) is periodically removed, causing a gradual pressure drop in the cell. Experiments are limited by a minimum internal cell pressure of 700 mbar due to the sensitivity of the pressure sensor and vapour pressures of the electrolyte. Apart from this pressure drop, the internal cell environment is therefore relatively constant allowing us to observe side reaction products that have occurred within a realistic cell environment.We additionally provide a detailed description of an adapter design for interfacing large format prismatic cells with our intermittently closed OEMS (ICEMS) setup. The adapter is placed over a hole in the cell (produced with a drill) and can be easily scaled for different cell geometries. Using this ICEMS setup, we provide operando pressure and gassing data from a calendared BAK PHEV2 cell. The pressure within the cell changes depending on the level of lithiation in the cathode (NMC) and anode (graphite), revealing the multiple phase transitions that occur in both materials during cycling. These transitions can be divided into four regions of interest, where graphite dominates regions I and III (with large pressure increases during charge) and NMC dominates regions II and IV (with pressure decreases during charge). By analysing the gas produced during these transitions, it is clear that structural changes within both electrodes result in side reactions. When graphite undergoes large volume changes (from 1L to 2L and 2 to 1, regions I and III), H2 and C2H4 are released as SEI reformation products, while the c lattice collapse in NMC (during the H2 to H3 transition, region IV) results in CO2 evolution (through O2 release that subsequently reacts with the electrolyte). In addition, we suggest that Lewis bases formed on the graphite through the reduction of electrolyte species ring open EC, forming CO2 [6]. The results of this study suggest that the internal chemistry of commercially available prismatic rechargeable batteries can be studied effectively using ICEMS without significantly altering the battery's chemistry.[1] A. M. Tripathi, W. N. Su, and B. J. Hwang, “In situ analytical techniques for battery interface analysis,” Chem. Soc. Rev., vol. 47, no. 3, pp. 736–751, 2018, doi: 10.1039/c7cs00180k.[2] P. Novák et al., “Advanced in situ characterization methods applied to carbonaceous materials,” J. Power Sources, vol. 146, no. 1–2, pp. 15–20, 2005, doi: 10.1016/j.jpowsour.2005.03.129.[3] N. Tsiouvaras, S. Meini, I. Buchberger, and H. A. Gasteiger, “ A Novel On-Line Mass Spectrometer Design for the Study of Multiple Charging Cycles of a Li-O 2 Battery ,” J. Electrochem. Soc., vol. 160, no. 3, pp. A471–A477, 2013, doi: 10.1149/2.042303jes.[4] R. Lundström and E. J. Berg, “Design and validation of an online partial and total pressure measurement system for Li-ion cells,” J. Power Sources, vol. 485, no. December 2020, 2021, doi: 10.1016/j.jpowsour.2020.229347.[5] L. A. Kaufman and B. D. McCloskey, “Surface Lithium Carbonate Influences Electrolyte Degradation via Reactive Oxygen Attack in Lithium-Excess Cathode Materials,” Chem. Mater., pp. 1–7, 2021, doi: 10.1021/acs.chemmater.1c00935.[6] N. Gogoi et al., “Silyl-Functionalized Electrolyte Additives and Their Reactivity toward Lewis Bases in Li-Ion Cells,” Chem. Mater., vol. 34, no. 8, pp. 3831–3838, 2022, doi: 10.1021/acs.chemmater.2c00345.

Synoptic, dynamical and microphysical properties for splitting and non-splitting hailstorms

Understanding storm splitting is of great importance for improving severe weather prediction and risk management. To further understand the mechanisms that cause hailstorm splitting, synoptic, dynamical and microphysical properties for a splitting hailstorm occurred on 19 June 2017 and a non-splitting hailstorm on 16 July 2014 in Beijing in the middle latitudes are investigated and compared based on synoptic maps, radar and sounding observations, as well as a three-dimensional cloud model with hail-bin microphysics. The results indicate that both hailstorms occurred under conditions with quite similar synoptic patterns, a tilting westerly trough at 500 hPa and a cold vertex at 700 hPa, and a clockwise-curved hodograph. However, the intensities of the westerly trough and low-level vertical wind shear were much stronger for the splitting hailstorm case than those for the non-splitting hailstorm case, so that the interactions between dynamical and microphysical processes in the splitting storm are also much stronger. It is found that for the splitting storm case the strong low-level vertical wind shear can cause large asymmetric pressure perturbation, pressure gradient forces and selective development in the storm and induce an obvious main updraft core splitting in the developing stage. The descending of high graupel/hail loading in the stable tropopause and lower stratospheric layer can excite strong downward propagating gravity waves (GWs) that induce a rapid storm splitting in the mature and decaying stages. In contrast, for the non-splitting storm, the relevant processes in the developing stage and the GWs excited by the descending of graupel/hail in the mature and decaying stages are too weak to cause an obvious splitting in the storm.

Metallurgical Analysis in the Outer Tube Fault Area

In the automotive manufacturing industry, product failures are still found. In this study, one of the automotive components, namely the outer tube of the motorcycle front fork, was cracked. The outer tube is part of the shock absorber component which is also connected to the motorcycle steering system. Failure analysis aims to obtain some data or facts that can indicate the root cause of the failure or failure. Sample preparation which includes the process of selecting the cut area, cleaning and cutting for the fractography process. As for metallography, sample preparation is continued with the process of mounting, sanding, polishing and etching. Fractographic test showed that the fracture occurred in a brittle fracture mode, with no traces of plastic deformation. The morphology of the fracture surface also shows the presence of gas trapped in large quantities. In the metallographic test, the overall microstructure shows an eutectic phase with a uniform dendrite structure pattern, this indicates that metal solidification occurs quite quickly and can cause a lot of gas to be trapped in the metal characterized by the presence of multiple porosities. This can provide an indication of the relationship between the microstructure and the fracture surface morphology. Cracking and brittle fracture can be caused by the stress that occurs in the metal that exceeds the yield and plastic limits due to the large pressure of gas trapped in the metal.

The “green” use of fluorocarbons in Cherenkov detectors and silicon tracker cooling systems: challenges and opportunities in an unfolding era of alternatives

Saturated fluorocarbons (SFCs) of form CnF(2n+2) are chosen for their optical properties as Cherenkov radiators, with C4F10 and CF4 currently used at CERN in the COMPASS and LHCb ring imaging Cherenkov detectors. Their non-conductivity, non-flammability and radiation-resistance also make SFCs ideal coolants: C6F14 liquid cooling is used in all LHC experiments, while C3F8 is used for the evaporative cooling of TOTEM and the ATLAS silicon tracker. These fluids, however, have high global warming potentials (5000–10000*GWPCO2), and represented around 36% of CERN’s CO2-equivalent emissions in 2018. There is thus an impetus to reduce their use, losses in purification and wastage through leaks, through improved monitoring and closed circulation system design. Newer spur-oxygenated fluoro-ketones, for example from the 3 M NOVEC® range, with CnF2nO structures, can offer similar performance to SFCs with but with very low, or zero GWP. Although these fluids do not yet exist in large quantities over the full CnF2 “matrix” the radiation tolerance and thermal performance of NOVEC 649 (C6F12O) was sufficiently promising for it to be chosen as a C6F14 replacement for cooling silicon photomultipliers. Additionally, subject to optical testing, NOVEC 5110 (C5F10O) could (if blended with nitrogen) replace both C4F10 and CF4 in Cherenkov detectors. Lighter molecules (for example C2F4O, with similar thermodynamics to C2F6)—if and when available in industrial quantities—might allow lower temperature operation than evaporative CO2 in future silicon trackers operated at very high luminosity. Ultrasonic gas mixture analysis is very sensitive to concentration changes of a heavy vapour in a light carrier, and is used—in the only such fluorocarbon coolant leak monitoring system operating at LHC—for real-time monitoring of C3F8 coolant leaks from the ATLAS pixel and SCT silicon trackers into their nitrogen-flushed environmental volumes. A typical C3F8 sensitivity of better than 10−5 is achieved. Advanced new ultrasonic algorithms allow measurement of the concentrations of a pair of gases of particular interest on top of a varying known baseline of other gases. The technique is thus of considerable value in leak monitoring and could be used to blend fluoro-ketones with nitrogen or argon to reduce the GWP “load” of large volume atmospheric pressure gas Cherenkov radiators without the recourse to higher-pressure noble gas approaches. This paper outlines an approach to GWP reduction with fluoro-ketone fluids and the blending of heritage SFCs or fluoro-ketones with lighter gases using ultrasonic monitoring and control. Possible avenues for the use of fluoro-ketones in liquid phase and evaporative cooling of silicon trackers are discussed.

A forward-curved blade centrifugal compressor for anode recirculation in proton exchange membrane fuel cells

Anode recirculation is crucial for the stable and efficient operation of automotive proton exchange membrane fuel cells (PEMFCs). The circulation is commonly driven by ejectors or positive displacement compressors, rather than centrifugal compressors, which have difficulty overcoming large pressure drops at low flow rates despite their promising attributes such as stable control and smooth operation. To address this gap, the present work proposes a novel design of a magnetically levitated centrifugal compressor featuring forward-curved blades. The comprehensive design process of this compressor is described, incorporating a novel design methodology, numerical simulations, and experimental validation. The compressor operates stably within the low-power range of typical automotive PEMFCs. At the design point, it achieves a static-to-static pressure ratio of 1.10 with an isentropic efficiency of 50 % and a system efficiency of 41 %. The test results demonstrate that the forward-curved blade centrifugal compressor is a viable option for anode recirculation in PEMFCs.

Investigation of angular deformation control for T-joint rib using multi-point constraint method

The circular rib is a crucial component of large pressure vessels, and its cross-section is primarily a T-joint structure. The double-sided arc welding (DSAW) process is an advanced technology for T-joint connection. However, during the T-joint welding process, harmful deformation still occurs in the form of angular deformation, including web and flange angular deformation. This paper proposes an innovative multi-point array constraint method to control the angular deformation of the rib based on the DSAW process for circular ribs. The welding deformation of the T-joint rib under multi-point constraints is studied using both numerical and experimental methods. The results of the numerical and experimental are consistent, with a relative error of no more than 12%. The multi-point constraint method is found to control angular deformation effectively, with the maximum angular deformation of the web not exceeding 1.77 mm and that of the flange not exceeding 0.45 mm after welding and releasing the constraint. The deformation control is significantly better than that of the rigid jig. Moreover, the coupling deformation of the web and flange caused by double-sided heat source and multi-point constraint forms an overall bending deformation. The deformation trend of each welding process is the same, with the main deformation occurring in the stage of releasing the constraint.

Effect of Internal Structure of Circular Dimples on Hydrodynamic Lubrication Characteristics of Thrust Bearings

In this study, the effects of three types of dimples with different internal structures on the fluid lubrication characteristics of seal-like thrust bearings were experimentally and numerically investigated. In the experiments, the load-carrying capacity and the frictional torque were measured. The measurements were performed with a fixed constant film thickness. The behaviors of cavitation bubbles occurred within the dimples were observed through the rotating glass plate. Three types of internal structures of dimples were tested: cylindrical, spherical and conical. The measurement results were simulated by using the Reynolds equation. In addition, applying the periodic condition, a single dimple was analyzed. As the results, in three types of dimples, the load-carrying capacity increased as the rotational speed increased. The cylindrical internal structure built up the largest pressure at the trailing edge of dimples, and consequently the largest load-carrying capacity. The frictional torque also increased with increasing the rotational speed in the dimpled bearings. However, the effect of the internal structure on the frictional torque was not significant. Analytical results showed that the pressure reached the maximum value at the trailing edge of the cylindrical internal structure. The conical and sphere internal structure had the maximum value slightly inside the trailing edge.

Summary to the article ”Complications that arise when sidetracking at the Gunashli field and ways to solve them”

As it is not economically feasible to construct gravity based fixed offshore platform (FOP) for drilling new wells in the “Guneshli” field, the sidetracking using the wells that have stopped producing is important. In this regard, it is necessary to examine the well stock at the field, select unproductive wells, and when using their bores, it is important to continue and increase with sidetracking. For a faster and easier result, first of all it is necessary to choose wells, the production casing which are equipped with diameters of 168 or 178 mm. In such wells, it will be possible to reach the design horizon with a smaller drilling passage by performing cutting operations at lower intervals. As a result, such wells are cheaper and more economically efficient. When performing cutting work on casing with 178 mm diameter, it is possible to drill and expand wells with a relatively large diameter, that is, with a diameter of 127 mm. This, in turn, made it possible to carry out major workover and well remedial work in the future. To eliminate failures and complications that arose during the drilling process, specific conclusions were drawn and it was proposed that when choosing an interval for opening a window, it was necessary to clarify the well configuration.The window opening should be smooth, and after cutting the casings, the cut part should be smoothed out by processing several times. Considering the limited productivity and large pressure losses when drilling small-diameter wells, drilling should be carried out not using a downhole drilling motor, but using a Rotor control system (RCS), one of the latest achievements of new technology. In order to prevent possible absorption and contamination of the well layers, wells should be drilled with solutions based on hydrocarbons or polymer potassium with the addition of necessary materials. If intensive absorption often occurs during drilling, the effectiveness of the measures taken is unsatisfactory, only in such cases should drilling be carried out with a bit with a diameter of 142.9 mm with the addition of materials that prevent absorption, without expanding the wellbore.

Assessment of Ecosystem Services at Different Scales

Natural and semi-natural ecosystems are under large anthropogenic pressure and degrading at an alarming speed [...]

CO2-Responsive Low Molecular Weight Polymer with High Osmotic Pressure as a Draw Solute for Forward Osmosis.

A key challenge in the development of forward osmosis (FO) technology is to identify a suitable draw solute that can generate a large osmotic pressure with favorable water flux while being easy to recover after the FO process with a minimum of energy expenditure. While the CO2- and thermo-responsive linear poly(N,N-dimethylallylamine) polymer (l-PDMAAm) has been reported as a promising draw agent for forward osmosis desalination, the draw solutions sufficiently concentrated to have high osmotic pressure were too viscous to be usable in industrial operations. We now compare the viscosities and osmotic pressures of solutions of these polymers at low and high molecular weights and with/without branching. The best combination of high osmotic pressures with low viscosity can be obtained by using low molecular weights rather than branching. Aqueous solutions of the synthesized polymer showed a high osmotic pressure of 170 bar under CO2 (πCO2) at 50 wt% loading, generating a high water flux against NaCl feed solutions in the FO process. Under air, however, the same polymer showed a low osmotic pressure and a cloud point between 26 and 33 °C (depending on concentration), which facilitates the recovery of the polymer after it has been used as a draw agent in the FO process upon removal of CO2 from the system.

Recent developments in stretchable and flexible tactile sensors towards piezoresistive systems: A review

AbstractStretchable and flexible piezoresistive sensors (SFPSs) can detect mechanical stimuli in terms of electrical response and provide adaptability to use with complex surfaces, whether stationary or moving. Its stretchable and flexible nature makes it ideal for detecting large strains, localized pressure, bending, and twisting. SFPSs can detect pressure and strain in a broad range. SFPSs have ease of manufacturing, high sensitivity, better durability, easy processing, and economic development. These qualities of SFPSs can open a wide range of application possibilities, such as healthcare, human motion detection, a safe environment to interact with robots, automation, and soft robotics. The discussion in this article starts from the sensing mechanism, design development over the years, a variety of materials used for substrates and to provide conductivity to the sensors, fabrication processes explored and developed, enhancement in the performance characteristics, to have future directions. Over the last decades, exponential development has occurred in SFPSs systems based on design mechanisms, materials used, and fabrication techniques, even though several technological and design challenges remain undetermined and bear decisive interdisciplinary intervention to address them.

Sequential-Crosslinking Fibrin Glue for Rapid and Reinforced Hemostasis.

Achieving hemostasis effectively is essential for surgical success and excellent patient outcomes. However, it is challenging to develop hemostatic adhesives that are fast-acting, strongly adherent, long-lasting, and biocompatible for treating hemorrhage. In this study, a sequential crosslinking fibrin glue (SCFG) is developed, of which the first network of the fibrin glue forms in situ within 2s to act as an initial physical barrier and locks the gelatin methacryloyl precursor for tight construction of the second network to enhance wet adhesion and durability for tissues covered with blood. The sequential crosslinking glue can provide large pressures (≈280mmHg of burst pressure), makes strong (38kPa of shear strength) and tough (≈60Jm-2 of interfacial toughness) interfaces with wet tissues, and outperforms commercial hemostatic agents and gelatin methacryloyl. SCFG are demonstrated as an effective and safe sealant to enhance the treatment outcomes of bleeding tissues in rat, rabbit, and pig models. The ultrafast gelation, strong adhesion and durability, excellent compatibility, and easy manufacture of SCFG make it a promising hemostatic adhesive for clinical applications.

Aerodynamic noise from a high-speed train bogie with complex geometry under a leading car

Among the various aerodynamic noise sources associated with high-speed trains, the bogie regions, and particularly the leading bogie, contribute most to the overall noise. To control this noise, insight into the noise generation mechanisms is imperative but relevant studies are limited due to the difficulties of simulating the flow in regions with complex geometry. An investigation is presented of the aerodynamic noise from a bogie under the leading car of a high-speed train using Delayed Detached Eddy Simulation method. A hybrid grid system is utilized to simulate the flow field, which provides input for the far-field noise calculations based on the Ffowcs Williams and Hawkings equation. Analysis shows that the outer bogie components experience large pressure fluctuations as they are immersed in the shear layer detached from upstream, which is therefore identified as playing a critical role in the noise generation. The resulting noise spectra are broadband and dominated by low frequencies. Compared with the bogie, the bogie cavity and train nose emit 5 dB greater sound power for the current geometry. This study improves understanding of the mechanisms behind the generation of aerodynamic noise in train bogies and lays the foundations for future studies of train bogie noise reduction.

Soft Coiled Pneumatic Actuator with Integrated Length-Sensing Function for Feedback Control

SPIRA Coil actuators are formed from thin sheets of PET plastic laminated into a coil shape that unfurls like a “party horn” when inflated, while many soft actuators require large pressures to create only modest strains, SPIRA Coils can easily be designed and fabricated to extend over dramatic distances with relatively low working pressures. Internal metalized PET strips separate in the extended portion of the actuator, creating an electrical circuit with a resistance that corresponds to the actuator length. This paper presents and experimentally validates easy-to-use design models for the actuators’ self-retracting spring stiffness, its pneumatic extension force, and its internal length-sensing electrical resistance. Testing of the self-sensing capabilities demonstrates that the embedded sensor can be used to determine the actuator length with virtually no hysteresis. Feedback control with the resistance-based sensing resulted in length-control errors within 5% of the extended actuator length (i.e., 3 cm of 60 cm).

Multidisciplinary optimization of automotive mega-castings merging classical structural optimization with response-surface-based optimization enhanced by machine learning

Large high pressure die castings (HPDC), recently referred to as mega-castings, can replace plenty of steel metal sheets usually employed for body-in-white (BIW) structures. They can save manufacturing expense and unleash additional lightweight potential thanks to additional design freedom and material properties. The BIW plays a major role in automotive design since it must fulfill numerous structural targets ranging from stiffness for vehicle dynamics, dynamic responses for NVH (noise, vibration, harshness), driving comfort standards and several passive safety requirements. The use of mega-casting structures leads to additional requirements with respect to castability and material quality. Achieving a lightweight design considering requirements related to crash or castability is a challenge on its own, due to the high computational cost of related simulation techniques. Considering multiple requirements simultaneously, therefore often leads to non-weight-optimal structures. To exploit the full lightweight potential, we present a generative multidisciplinary optimization pipeline for the structural design of automotive mega-casting parts in this paper. The approach combines established methods in automotive industry such as topology optimization and response-surface-based (RSM) optimization and enhances the latter by machine learning (ML) based clustering and classification. In a first step topology optimization is employed to derive optimal load-paths for multidisciplinary loading conditions. For this purpose, casting manufacturing constraints as well as more than hundred linearized loads are used to incorporate NVH and passive safety requirements. In a next step the optimal thickness distribution and rib orientation of the structure is achieved using RSM optimization algorithms for the computationally expensive nonlinear crash and casting simulations. Performance indicators are treated by unsupervised learning based on clustering. This enables classification constraints based on simulation field results from hundreds of samples to be included into RSM optimization. It resolves a typical risk of pure scalar, regression-type targets, where supposed optimal results fail when domain experts examine the full field result of the corresponding simulation. It is shown how this approach is superior in achieving a weight-optimal design and turnaround time compared to a design workflow classically used for BIW structures.

Study on physical explosion equivalent of large diameter and high pressure natural gas pipeline

High pressure natural gas pipelines are prone to material failure and explosion due to various reasons. Over the years, scholars have done in-depth research on the process of chemical explosion. In this paper, the energy components of high-pressure trunk natural gas pipeline under normal operation state were derived. Based on the assumption of adiabatic non isentropic, the pressure distribution in the pipeline within a period of time after the pipeline cracks was derived, and the energy released by the physical explosion of the pipeline was further derived. To verify the theoretical results, an original size pipe explosion experiment was organized, and the pressure distribution obtained from the experiment was found to be in good agreement with the theoretical calculation results. Through the crack propagation time and the duration of ground motion obtained from the experiment, the range of the duration of the pipeline burst crack impact was obtained, and the equivalent range of the pipeline explosion was further calculated. At the same time, through the regression analysis of ground motion, the equivalent of the pipe explosion in this experiment was about 177 kg TNT, which was consistent with the theoretical results. Further, the theoretical model and experimental results were verified by numerical simulation, and deeply studied the influence factors of buried depth on the explosion equivalent, as well as the relationship between the environment of the pipeline and the explosion damage mode and hazard range of the pipeline. The research results of this paper give the calculation method and magnitude range of physical explosion equivalent of high-pressure trunk natural gas pipeline. It provides a reference for the formulation of safety standards for high-pressure trunk natural gas pipelines and inert gas pressure vessels.