High Pressure Field Research Articles

Recent advances in physical/chemical methods as alternatives to SO2 for winemaking: Principles, challenges and perspectives

Sulphur dioxide (SO2) is commonly used in the wine industry to prevent oxidation and maintain microbial stability. However, it can harm consumer health, resulting in a growing demand for chemical-free wine. Therefore, reducing or eliminating the addition of SO2 has become a prevalent trend in the wine industry. In recent years, researchers have made significant progress in finding alternative methods to SO2. This review provides the latest research progress on innovative methods proposed to replace SO2 in winemaking. These include dimethyl dicarbonate, silver nanoparticles, lysozyme, chitosan, phenolic compounds, membrane filtration, ultrasound, ultraviolet irradiation, high pressure, and pulsed electric field. However, these individual antimicrobial methods do not possess the same comprehensive antimicrobial and antioxidant properties as SO2. In the proposed strategy, a promising alternative to SO2 could be to combine physical sterilization technologies with antimicrobial substances. In particular, gentle physical techniques such as pulsed electric field in synergy with natural grape polyphenols can maintain the microbiological stability of wine without the introduction of foreign aid substances, while enhancing the wine's antioxidant properties. In conclusion, while replacing SO2 entirely for wine production remains challenging, the combination of physical sterilization technologies and natural antimicrobial substances shows promise as a viable alternative.

Combined effects of high hydrostatic pressure and pulsed electric fields on quinoa starch: Analysis of microstructure, morphology, thermal, and pasting properties

The aim of this study was to evaluate the impact of non-thermal methods, using high hydrostatic pressure (HHP) and pulsed electric field (PEF), on the dual modification of quinoa starch and to analyze the microstructural, morphological, thermal, pasting, and texture properties. Starch was treated with HHP at 400 MPa for 10 min, while PEF was applied using voltages of 10 and 30 kV cm−1 for a total time of 90s. The modification techniques were effective in breaking down amylose molecules and amylopectin branches, where for the dual treatment, higher values of DP6–12 were found. The average diameter and gelatinization temperatures were elevated after HHP, thus forming clusters that require more energy for paste formation. The use of 30 kV cm−1 and 400 MPa (HP30) in starch facilitates the creation of new food products with better texture, stability and nutritional value, making them suitable for use in food emulsions and the cosmetics industry.

Detachable acoustofluidic droplet-sorter

BackgroundCell sorting is crucial in isolating specific cell populations. It enables detailed analysis of their functions and characteristics and plays a vital role in disease diagnosis, drug discovery, and regenerative medicine. Fluorescence-activated cell sorting (FACS) is considered the gold standard for high-speed single-cell sorting. However, its high cost, complex instrumentation, and lack of portability are significant limitations. Additionally, the high pressure and electric fields used in FACS can harm cell integrity. In this work, an acoustofluidic device was developed in combination with surface acoustic wave (SAW) and droplet microfluidics to isolate single-cell droplets with high purity while maintaining high cell viability. ResultHuman embryonic kidney cells, transfected with fluorescent reporter plasmids, were used to demonstrate the targeted droplet sorting containing single cells. The acoustofluidic sorter achieved a recovery rate of 81 % and an accuracy rate higher than 97 %. The device maintained a cell viability rate of 95 % and demonstrated repeatability over 20 consecutive trials without compromising efficiency, thus underscoring its reliability. Thermal image analysis revealed that the temperature of the interdigital transducer (IDT) during SAW operation remained within the permissible range for maintaining cell viability. SignificanceThe findings highlighted the sensitivity and effectiveness of the developed acoustofluidic device as a tool for single-cell sorting. The detachable microfluidic chip design enables the reusability of the expensive IDT, making it cost-effective and reducing the risk of cross-contamination between different biological samples. The results underscore its capability to accurately isolate individual cells on the basis of specific criteria, showcasing its potential to advance research and clinical applications requiring precise cell sorting methodologies.

Effects of different pretreatment on the drying characteristics and pectin properties of jujube by microwave coupled with pulsed vacuum drying

AbstractThe effects of ultrasound (US), ultrahigh pressure (UP), cold plasma (CP), and high pressure and pulsed electric fields (PEF) pretreatments were evaluated for drying characteristics, bioactive components, and pectin properties of jujube slices during microwave coupled with pulsed vacuum drying (MPVD). US, CP, and PEF reduced drying time by 18.75%, while UP reduced it by 6.25%. Samples treated with US and PEF showed improved color and rehydration (345.11%, 319.24%), with SEM revealing larger pores post‐pretreatment. PEF‐treated jujube had highest phenol (16.95 mg GAE/g DW) and water‐soluble pectin(WSP) (43.71 mg/g AIR), correlating positively with rehydration (r = 0.67). CP had highest flavonoid content (17.01 mg RE/g DW) and US showed highest antioxidant activity (DPPH 80.57%, ABTS 89.65%). Chelate‐soluble pectin (CSP) Sodium carbonate‐soluble pectin (NSP) was positively correlated with hardness (r = 0.71, 0.69). These findings suggest pretreatments improve drying efficiency, nutrient retention, and pectin functionality in jujube products. Practical ApplicationsDrying for jujube (Ziziphus jujuba Mill.) is the most common method of processing and ensure the sale. Three kinds of non‐thermal processing pretreatment method (ultrasound, ultrahigh pressure, and cold plasma) combined with novel drying method, microwave coupled pulsed vacuum drying (MPVD) was studied in the application on the dehydration of jujube slice in this paper. The drying characteristics and pectin properties of winter jujube were analyzed and treated by MPVD compared with freeze drying and hot air drying, for both technological research and processing practice. The drying kinetics, bioactive compounds, antioxidant capacity, sensory attributes, and pectin properties were also used as descriptors in order to promising dehydration method for obtaining high value‐added jujube products. Moreover, the relationship between the cell wall pectin and the phenols, hardness and crispness were analyzed, which give a new insight to study the changing scheme in the nutrients and the texture during the dehydration for fruits and vegetables.

High-Pressure-Field Induced Synthesis of Ultrafine-Sized High-Entropy Compounds with Excellent Sodium-Ion Storage.

Emerging high entropy compounds (HECs) have attracted huge attention in electrochemical energy-related applications. The features of ultrafine size and carbon incorporation show great potential to boost the ion-storage kinetics of HECs. However, they are rarely reported because high-temperature calcination tends to result in larger crystallites, phase separation, and carbon reduction. Herein, using the NaCl self-assembly template method, by introducing a high-pressure field in the calcination process, the atom diffusion and phase separation are inhibited for the general formation of HECs, and the HEC aggregation is inhibited for obtaining ultrafine size. The general preparation of ultrafine-sized (<10 nm) HECs (nitrides, oxides, sulfides, and phosphates) anchored on porous carbon composites is realized. They are demonstrated by combining advanced characterization technologies with theoretical computations. Ultrafine-sized high entropy sulfides-MnFeCoCuSnMo/porous carbon (HES-MnFeCoCuSnMo/PC) as representative anodes exhibit excellent sodium-ion storage kinetics and capacities (a high rating capacity of 278 mAh g-1 at 10 A g-1 for full cell and a high cycling capacity of 281 mAh g-1 at 20 A g-1 after 6000 cycles for half cell) due to the combining advantages of high entropy effect, ultrafine size, and PC incorporation. Our work provides a new opportunity for designing and fabricating ultrafine-sized HECs.

A CALPHAD thermodynamic model for multicomponent alloys under pressure and its application in pressurized solidified Al–Si–Mg alloys

High pressure technology has been utilized as an important means to regulate phase structure and improve the properties/performance of alloys. The CALPHAD approach based on accurate databases has great advantages in efficient alloy design. However, the application of CALPHAD in high pressure field is hindered by the lack of reliable thermodynamic model/database for multicomponent alloys under pressure. In this paper, a phenomenologically thermodynamic model for multicomponent alloys under pressure is first developed by separating the contribution into two parts, one is at atmosphere pressure and the other is caused by an increase in pressure, and then successfully applied to establish the pressure-dependent thermodynamic database of ternary Al–Si–Mg system. The calculated phase equilibria/thermodynamic properties of pressure dependence in related alloys are in good agreement with the limited experimental data in the literature, validating the reliability of the obtained thermodynamic database. After that, a CALPHAD design framework for pressurized solidified alloys is proposed by integrating the present pressure-dependent thermodynamic model/database, CALPHAD-type calculations/simulations, and previously developed high-throughput calculation platform Malac-Distmas. Such a framework is finally applied to predict the pressurized solidification and high pressure heat treatment behaviors in different Al–Si–Mg alloys. The predicted microstructure, phase transitions and phase equilibria after pressurized solidification and high pressure heat treatment are consistent with the experimental data. Furthermore, the insights into effect of pressure on the thermodynamic essence of alloys are gained, which may definitely facilitate the advancement of alloy design under high pressure technology.

Shelf-Life Enhancement Applying Pulsed Electric Field and High-Pressure Treatments Prior to Osmotic Dehydration of Fresh-Cut Potatoes.

From a quality standpoint, it is desirable to preserve the characteristics of fresh-cut potatoes at their peak. However, due to the mechanical tissue damage during the cutting process, potatoes are susceptible to enzymatic browning. This study pertains to the selection of the appropriate osmotic dehydration (OD), high pressure (HP), and pulsed electric fields (PEF) processing conditions leading to effective quality retention of potato cuts. PEF (0.5 kV/cm, 200 pulses) or HP (400 MPa, 1 min) treatments prior to OD (35 °C, 120 min) were found to promote the retention of the overall quality (texture and color) of the samples. The incorporation of anti-browning agents (ascorbic acid and papain) into the osmotic solution improved the color retention, especially when combined with PEF or HP due to increased solid uptake (during OD) as indicated by DEI index (2.30, 1.93, and 2.10 for OD treated 120 min, non-pre-treated, HP pre-treated, and PEF pre-treated samples, respectively). PEF and HP combined with OD and anti-browning agent enrichment are sought to improve the quality and microbial stability of fresh-cut potatoes during refrigerator storage. Untreated fresh-cut potatoes were characterized by color degradation from the 2nd day of storage at 4 °C, and presented microbial growth (total viable counts: 6 log (CFU)/g) at day 6, whereas pre-treated potato samples retained their color and microbiologically stability after 6 days of cold storage (total viable counts, <4 log(CFU)/g).

Identification of Resistant and Susceptible Sources against Blast Diseases in Finger Millet [Eleusine coracana L. (Gaertn.)

The study was undertaken to evaluate the 490 finger millet (Eleusine coracana L.) genotypes (released, pre-release and breeding genotypes) including two check varieties viz., Indaf 5 (susceptible) and GPU-28 (resistant) against neck and finger blast disease at Hill Millet Research Station, Waghai, The Dangs, Gujarat during kharif, 2018 to 2022. Among all the 490 genotypes, 148 genotypes have shown resistant reaction under high disease pressure field conditions for neck and finger blast disease. However, 44 germplasm genotypes have shown consistent susceptible reaction during five years tested viz; kharif, 2018 to 2022. The genotypes viz., CFMV 2, GN-8, VL-376, PR-202 and GPU-67, showed the higher immune reaction under natural field condition. The pooled percent disease intensity of neck and finger blast diseases ranged from 2.90 to 72.4 per cent and 3.9 to 84.2 per cent respectively, in all tested genotypes including national and local checks. The resistant check variety GPU-28 exhibited resistant reaction to both neck and finger blast. In susceptible check variety Indaf-5 recorded the pooled diseases intensity of 61.74 % for neck blast and 73.6 % for finger blast. In which 72.4 and 84.2 is the highest percent pooled disease intensity of neck and finger blasts recorded in finger millet entry WN 666 which is the most highly susceptible reaction noted across five years of study in blast susceptible zone of Gujarat.

High sensitivity temperature and gas pressure sensor based on PDMS sealed tapered hollow-core fiber

We use hollow core fiber (HCF) and single mode fiber (SMF) fusion splicing to form a sensor with a “SMF-HCF-SMF” structure. To improve the sensitivity of the sensor, the HCF is tapered and stretched to a waist diameter of 10 μm. Then, in order to further improve the sensitivity of the sensor to temperature and pressure, as well as the mechanical strength of the sensor, we coated a layer of polydimethylsiloxane (PDMS) thin film on the surface of the tapered HCF. When light propagates in the sensor, an anti-resonant reflection optical waveguide (ARROW) mechanism is formed. Due to the excellent thermal sensitivity and elasticity of PDMS, the transmission spectrum of the sensor will significantly drift due to changes in environmental temperature and gas pressure, achieving temperature and pressure measurement. The experimental results show that the maximum temperature and gas pressure sensitivity of the sensor reach −3.2321 nm/℃ and −22.80 nm/MPa, respectively. In addition, the sensor also has good repeatability and stability, as well as short response time. It has certain application prospects in the field of high sensitivity temperature and gas pressure sensing measurement.

Theoretical study on the pressure expansion mechanism of diffused self-pumping hydrodynamic mechanical seal

The pressure expansion performance is the key and basis for the diffused self-pumping hydrodynamic mechanical seal to achieve its good cooling performance, self-cleaning performance, and sealing performance. Using the moment of momentum theorem and Stodola's formula, the pressurization effect of the spiral groove on the fluid was analyzed, and the energy head equation of the work done by the spiral groove on the fluid is established. According to the principle of conservation of energy, the energy equation and Bernoulli equation of the work done by the spiral groove on the fluid are derived, the mathematical expression of the conversion of fluid kinetic energy into hydrostatic pressure in the diffuser groove was established, the energy change and energy distribution problems of the fluid after the work of the spiral groove are clarified, and the pressure expansion mechanism is revealed. Through numerical simulation, the relationship between the fluid pressure at the sealing interface, the position and size of the high-pressure field, the opening force, and the leakage rate under different rotational speeds and the structural parameters of the diffuser groove were explored. Finally, the pressure expansion performance of the ordinary self-pumping hydrodynamic mechanical seal and diffused self-pumping hydrodynamic mechanical seal is compared. The results show that the diffuser groove can effectively convert part of the fluid kinetic energy into pressure energy, improve the opening force of the sealing interface, and have a good pressurization effect on the sealing end face. With the widening of the diffuser groove, the pressure peak of the sealing interface increases, the high-pressure field area continues to expand and tends to expand toward the outer diameter of the seal ring, and the opening force also increases significantly; increasing the depth of the diffuser groove will cause the pressure peak of the sealing interface to become smaller, and the area of the high-pressure field will also decrease rapidly, which is not conducive to improving the opening force of the sealing end face.

Producing a High Level Harmonic Acoustic Pressure Field with Harmonic Acoustic Pneumatic Source (HAPS): Experimental Validation of the Harmonic Distortion Reduction

Applications such as active control of fane noise, require high Sound Pressure Levels (SPL). Pneumatic acoustic sources are usually used for that purpose (e.g. the WAS 3000 and the Mark VI and VII). The harmonic acoustic pneumatic sources (HAPS) - which use the chopping of an airflow to generate an acoustic pressure field - are being studied for applications requiring high-level harmonic acoustic pressure fields. A recent study has shown that the amplitude, phase, and frequency generated by HAPS are accurately controllable, and can reach 120 dBSPL. However, higher harmonics are also generated at high SPL and this could be detrimental to the intended applications (e.g. active control of tonal noise). An experimental campaign dedicated to understanding the harmonic distortion of HAPS has been conducted on a single HAPS in a semi-anechoic chamber. Measurements with quarter-wave tube at the output of the HAPS were also carried out to reduce this distortion. Levels of 120 to 130 dBSPL for the fundamental were reached, with a difference of 10 dB between the fundamental and the second harmonic (H1/H2 distorsion). Adding a quarter-wave tube increased the acoustic pressure level from 4 to 6 dBSPL, and the H1/H2 distorsion from 2 to 8 dBSPL.

Experimental Data-Analysis Methods Analyze Multiphase-Flow Data Sets

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 32170, “Performance Mapping of Multiphase-Flow Model—Connecting the Dots From Experimental Data,” by Auzan A. Soedarmo, SPE, Eduardo Pereyra, SPE, and Cem Sarica, SPE, The University of Tulsa. The paper has not been peer reviewed. Copyright 2023 Offshore Technology Conference. Reproduced by permission. _ In the complete paper, the authors present exploratory data analyses to evaluate comprehensively the performance of a steady-state multiphase-flow point model in predicting high-pressure, near-horizontal data from independent experiments. This effort provides wide-ranging insight that can reflect the current state of the art of multiphase-flow modeling and pinpoint areas where improvements are needed. Much of the complete paper is devoted to the literature relating to the authors’ work; these specific citations are not included in this synopsis. Introduction The emergence of “big data” has encouraged the use of data from various sources to enhance the decision-making process. The authors write that, unfortunately, multiphase-flow studies often are performed in theoretical silos, within which specific experiments were performed and upon which certain model improvements were proposed. Therefore, it is easy to lose sight of the larger context in terms of current understanding and modeling capability. This disconnected approach also has produced an ever-growing, potentially unmanageable list of closure relationships, which can be counterproductive for model development. Experimental Data-Analysis Methodology For their study, the authors collected near-horizontal (–5° to +5°) gas/liquid data from literature with a gas density of 5 kg/m3 or greater. Atmospheric data were excluded because gas and air at such conditions are typically very compressible, meaning that superficial gas velocity can vary considerably along the pipe. One also can argue that high-gas-density cases are more relevant to typical high-pressure field applications. The authors collected more than 2,000 data points for pressure drop, holdup, and flow patterns. This accumulated data set by no means can be categorized as “big data” in a traditional sense; however, the authors write that it is sufficient for demonstrating how exploratory data analysis may extract actionable insights from data sets from various independent sources. This data set is henceforth called the “HP data set.” No high-viscosity liquid (10 cP or higher) is included in the HP data set. When comparing experimental data collected under different conditions, it is helpful to reduce the problem’s dimensionality (down from 10 dimensions in two-phase gas/liquid flow, excluding the gravitational acceleration constant). A traditional approach would be to use dimensionless numbers such as Reynolds and Froude numbers. A single dimensionless number, however, can only account for limited parameters. For example, the Reynolds number only considers the inertia and viscous effects, while the Froude number only considers the inertia and gravity effects. Therefore, a mechanistic multiphase-flow model is used in this study that accounts for all dimensions of the multiphase-flow problems and reduces them into one dimension, namely the discrepancy between the predicted value and experimental data.

Analysis of the eastern Adriatic sea level extremes

Aim: To examine the frequency, strength, and driving mech-anisms of the eastern Adriatic sea level extremes.Methods: In 2017, a tide-gauge station, and a meteorological station have been installed at Stari Grad (Hvar Island, east-ern middle Adriatic Sea). Three years of sea level and at-mospheric measurements were analysed. Ten strongest ep-isodes of the following extreme types were extracted from sea level data: positive long-period (T &amp;gt;210 min) extremes; negative long-period (T &amp;gt;210 min) extremes; short-period (T &amp;lt; 210) extremes. Long-period extremes were defined as situations when sea level surpasses (is lower than) 99.7 (i.e., 2) percentile of residual long-period sea level height, and short-period extremes as situations when 2.5-h variance of short-period sea level oscillations is higher than 99.4 per-centile of total variance of short-period series. Types of sea level extremes were subsequently associated to characteris-tic atmospheric situations.Results: Positive long-period extremes commonly appeared during the presence of low-pressure atmospheric systems over the Adriatic – such system were accompanied with strong SE winds. Negative long-period extremes were as-sociated with presence of high atmospheric pressure fields over the Adriatic Sea, either with strong NE winds, or calm weather. Appearance of short-period sea level extremes corresponded to either low atmospheric pressure fields and strong SE wind, or normal/high pressure fields and calm weather/no winds over the Adriatic. A strong seasonal sig-nal was detected, with the positive long-period extremes occurring mostly during November to February, and the negative long-period extremes occurring during January to February. The short-period extremes appeared throughout the year, but strongest events appeared during May to July.Conclusion: Results show that Stari Grad is a flood-prone lo-cation, both when it comes to positive long-period extremes and to short-period extremes. Furthermore, long-period and short-period extremes occasionally occur simultane-ously in Stari Grad, pointing to a previously unknown added hazard level

Synthesis of hard magnetic α-MnBi phase by high pressure torsion and field assisted annealing

Bulk composites using powder blends of Mn and Bi with equal atomic ratios are consolidated and severely deformed by high-pressure torsion (HPT). Subsequent annealing treatments lead to the formation of the ferromagnetic and rare-earth free hard magnetic α-MnBi phase. The initial phase formation is studied by in-situ high-energy XRD annealing experiments showing a beneficial influence of HPT-deformation on the amount of α-MnBi. The nucleation sites are strongly increased, thus the volumetric α-MnBi phase content exceeds 50 vol%. A lower HPT-pressure of 2 GPa is found to be preferred over 5 GPa to obtain high α-MnBi contents. Annealing is done with or without applying an external magnetic field. Additionally, influences of the HPT-induced shear deformation are discussed and correlated with preferred diffusion path ways fostering the formation of anisotropic α-MnBi phase.

Design of PDMS/CNT flexible pressure sensor based on double structure with the regulation of electrical properties

Introducing microstructure on the surface or porous structure inside of dielectric layer can improve the sensitivity and monitoring range of the flexible pressure sensor. However, developing pressure sensors with high sensitivity in the high-pressure range is challenging because of the trade-off between sensitivity and linearity of pressure. Here, we report a design approach based on the collaboration of double structure and electrical characteristics that can improve sensor sensitivity at high pressure. The surface microstructural and internal porous structure of the dielectric layer provide a more comprehensive deformation range for the sensor from a mechanical perspective. The effects of the conductive carbon nanotube (CNT) content between two structures on the overall electromechanical characteristics of the sensor were studied. This collaborative (structure and component) design can effectively increase the monitoring range of the sensor and accomplish “gear shifting” of the sensitivity by the non-uniform distribution of CNT in the structure. The optimized capacitive pressure sensor exhibits outstanding sensitivity over a wide monitoring range (1.17 kPa−1 in the 0−100 kPa, 0.49 kPa−1 in the 100−350 kPa, and 0.23 kPa−1 in the 350−1000 kPa), and fast response capability (30 ms). The pressure sensor has excellent integrated sensing performance in rubber wheels' static/dynamic pressure monitoring, demonstrating application potential in high-pressure fields.

A review on bioactive peptides derived from meat and by-products: Extraction methods, biological activities, applications and limitations

Meat and its by-products offer a rich source of bioactive compounds which have potential applications in both the food and pharmaceutical industries. In this review, we present several extraction methods and report the identification and properties of bioactive peptides. We also examine the challenges and limitations associated with their use in food applications. Enzymatic hydrolysis and fermentation using starts cultures are common methods for generating bioactive peptides from meat proteins. Additionally, natural gastrointestinal digestion can also produce bioactive peptides. However, emerging technologies like high hydrostatic pressure, subcritical extraction and pulsed electric fields can improve hydrolysis and increase the yield of bioactive peptides. Online bioinformatics applications have emerged as an established method for identifying potentially bioactive peptides. These tools reduce the cost and time required for traditional methods of research. Finally, incorporating bioactive peptides into diets for specific purposes such as supporting vulnerable populations like children and the elderly ensures safety and efficacy.

Combining high pressure and electric fields towards Nannochloropsis oculata eicosapentaenoic acid-rich extracts

Nannochloropsis oculata is naturally rich in eicosapentaenoic acid (EPA). To turn this microalga into an economically viable source for commercial applications, extraction efficiency must be achieved. Pursuing this goal, emerging technologies such as high hydrostatic pressure (HHP) and moderate electric fields (MEF) were tested, aiming to increase EPA accessibility and subsequent extraction yields. The innovative approach used in this study combined these technologies and associated tailored, less hazardous different solvent mixtures (SM) with distinct polarity indexes. Although the classical Folch SM with chloroform: methanol (PI 4.4) provided the highest yield concerning total lipids (166.4 mglipid/gbiomass), diethyl ether: ethanol (PI 3.6) presented statistically higher values in terms of EPA per biomass, corresponding to 1.3-fold increase. When SM were used in HHP and MEF, neither technology independently improved EPA extraction yields, although the sequential combination of technologies did result in 62% increment in EPA extraction. Overall, the SM and extraction methodologies tested (HHP—200 MPa, 21 °C, 15 min, followed by MEF processing at 40 °C, 15 min) enabled increased EPA extraction yields from wet N. oculata biomass. These findings are of high relevance for the food and pharmaceutical industries, providing viable alternatives to the “classical” extraction methodologies and solvents, with increased yields and lower environmental impact.Key points• Et2O: EtOH is a less toxic and more efficient alternative to Folch solvent mixture• HHP or MEF per se was not able to significantly increase EPA extraction yield• Combinations of HHP and MEF technologies increased both lipids and EPA yieldsGraphical abstract

Raman Studies of Two-Dimensional Group-VI Transition Metal Dichalcogenides under Extreme Conditions

In the past decade, two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted increasing attention because of their striking physical properties and extensive applicability. Meanwhile, Raman spectroscopy has been demonstrated to be a feasible tool and is extensively employed in research on 2D TMDs. In recent years, the deployment of Raman spectroscopy under extreme conditions has elucidated the physical properties of TMDs. In this review, we focus on the extreme-condition Raman spectroscopy of typical group-VI TMDs, which are classified and discussed under the three extreme conditions of low temperature, high pressure and high magnetic field. The conclusion presents the most pressing challenges and attractive future opportunities in this rapidly developing research field.

Synergistic depolymerisation of alginate and chitosan by high hydrostatic pressure (HHP) and pulsed electric fields (PEF) treatment in the presence of H2O2

Physically-induced depolymerisation procedures are often preferred for obtaining alginate and chitosan oligosaccharides as they either do not use or make minimal use of additional chemicals; therefore, separation of the final products is facile. In this work, solutions of three types of alginate with different mannuronic and guluronic acid residues ratio (M/G ratio) and molecular weights (Mw) and one type of chitosan were non-thermally processed by applying high hydrostatic pressures (HHP) up to 500 MPa (20 min) or pulsed electric fields (PEF) up to 25 kV cm−1 (4000 μm) in the absence or presence of 3 % hydrogen peroxide (H2O2). The impact on the physicochemical properties of alginate and chitosan was investigated by rheology, GPC, XRD, FTIR, and 1H NMR. In the rheological investigations, the apparent viscosities of all samples decreased with increasing shear rate, indicating a non-Newtonian shear-thinning behaviour. GPC results reported Mw reductions that ranged between 8 and 96 % for all treatments. NMR results revealed that HHP and PEF treatment predominantly reduced the M/G ratio of alginate and the degree of deacetylation (DDA) of chitosan, whilst H2O2 promoted an increase in the M/G ratio in alginate and DDA of chitosan. Overall, the present investigation has demonstrated the feasibility of HHP and PEF for rapidly producing alginate and chitosan oligosaccharides.

Flow–Solid Coupling Analysis of Ice–Concrete Collision Nonlinear Problems in the Yellow River Basin

Yellow River ice is the most prominent and significant natural disaster in winter and spring in China. During the drift ice period, water transmission tunnels located in this area tend to be hit by water–drift ice coupling. Thus, it is an important issue to reduce water transmission tunnel damage by drift ice, ensure the safety of operation and maintenance, and prevent engineering failure. In this paper, a numerical simulation of the collision process between ice and the tunnel is carried out by using the fluid structure coupling method and ANSYS/LS-DYNA finite element software. In addition, a model test with a geometric scale of 1:10 is carried out to verify the numerical simulation results, and the mechanical properties and damage mechanism of drift ice impacting the tunnel concrete lining in water medium are studied. The results show the following: the experimental values of maximum equivalent stress and X-directional displacement of the flow ice on the water transfer tunnel have the same trend as the simulated values, both of which show an increasing trend with an increase in flow ice velocity. It is shown that the ice material model parameters, ALE algorithm, and grid size used in this paper are able to simulate the impact of drift ice on the water transfer tunnel more accurately. With an increase in drift ice collision angle and drift ice size, the fitted curves of equivalent stress and peak displacement in X-direction all show relationships of exponential function. The peak value of displacement in the X-direction and maximum equivalent stress decrease with an increase in the curvature of the tunnel structure. It is also shown that the influence of change in drift ice size on the tunnel lining is greater than that of a change in tunnel section form. It is found that a high-pressure field will be formed due to extrusion of flowing ice, which should be fully considered in the numerical simulation. The research method and results can provide technical reference and theoretical support for prevention and control of ice jam disasters in the Yellow River Basin.