Pressure Phase Research Articles

Environment and settlement - A multiproxy record of holocene palaeoenvironmental development from Lake Wonieść, Greater Poland

This multi-proxy approach combines results of sedimentological, pollen and diatom studies on sediments of Lake Wonieść, Greater Poland. This enables reconstruction of the natural and anthropogenic drivers of past environmental change. Several steps of lake development are recorded, from a eutrophic to an oligotrophic stage, and with increasing human influence back to a hypereutrophic one. Human influence in the form of eutrophication due to arable farming has been the main driver in the changing ecology of the lake in the second half of the Holocene. The record provides a diachronic perspective of regional “boom and bust” phases of greater or lesser human pressure on the landscape. Early evidence of cereal-type pollen indicates human occupation of areas of chernozem soil during the Linearbandkeramik (LBK) Neolithic period from 5250 cal bc onwards. A clear opening of the landscape occurred during the Trichterbecher (Funnel Beaker) period at ca. 3800 cal bc. From this time onwards, the human influence on the lake can be traced by the geochemical and diatom records. Neolithic, Bronze Age, Iron Age and medieval boom and bust phases of settlement intensity are discussed. A comparison with two other high-resolution lake records from Poland (Lakes Gościąż and Szurpiły) show a good agreement of many of the “boom and bust” phases with Lake Gościąż (“boom” at 3500 and 2150 cal bc, “bust” at 3250, 1560 and 1 bc) and a few even with both, Lake Szurpiły and Lake Gościąż (“boom” at bc and “bust” at 500 cal bc and cal ad 400). This is indicative of supra-regional changes in intensity of land use.

Influence of the high-pressure ω - Zr phase on selected properties of sintered zirconium powder materials

Most commercial zirconium alloys are obtained by melting methods and consist of α-Zr. The sintering of zirconium powders is carried out mainly by pressure methods, which is the reason for the appearance of higher stresses in the materials and the presence of the high-pressure ω-Zr phase. Sintered zirconium materials containing α-Zr, α-Zr + β–Zr + Nb and ω-Zr + α-Zr phases, with a relative density of approximately 98%, using the Spark Plasma Sintering method and the ultra-high pressure method were obtained. X-ray diffraction methods were used to determine the content of individual zirconium phases in the materials. Stresses were measured in alpha and omega zirconium phases by the sin2 ψ diffraction method for all investigated materials. Hardness, tensile strength and elongation of materials were measured. The greatest elongation of 7.1% was found for sintered materials containing ω–Zr. The presence of the ω - Zr obtained under ultra-high pressure conditions does not significantly affect the stress level in ω Zr and in the α-Zr phase of the High Pressure – High Temperature sintered material. Tribological tests were carried out using the ball-on-disk method, with alumina as counter-samples. The research showed an adverse effect on the abrasive wear of the high-pressure omega Zr phase. The zirconium oxidation process and the separation of the oxide from the wear surface plays an important role in the abrasion of all sintered zirconium materials.

Mean-Field Study of Antiferromagnetic and Antiferroquadrupolar Orderings in Tetragonal CeCoSi

We investigate the stability of the multipolar orderings in f-electron material CeCoSi based on a self-consistent mean-field calculation for the effective localized model. This material has two ordered phases in the temperature–pressure phase diagram: the antiferromagnetic phase and the nonmagnetic phase, the latter of which has been suggested to be an antiferroquadrupolar phase. Meanwhile, the origin of the antiferroquadrupolar phase has been unclear, since a quadrupole degree of freedom is present only between the ground-state level and highly separated excited-state level under a tetragonal crystalline electric field (CEF), whose energy scale is much larger than the transition temperature. To understand the sequence of the phase transition from the paramagnetic phase, antiferroquadrupolar phase, and antiferromagnetic phase when decreasing the temperature, we examine the important interaction parameters in the effective localized model. We clarify that the 3z2 − r2-type of the antiferroquadrupolar interactions can renormalize the CEF level splitting, which might assist a quadrupolar ordering even in a tetragonal system without orbital degeneracy. Moreover, the stability of the antiferroquadrupolar and antiferromagnetic states in a magnetic field and the behavior of the magnetic/quadrupolar susceptibility are also presented for the information to identify the unknown order parameter in the nonmagnetic ordered phase.

Investigating a deterministic yet computationally cheap combustion parameter for model predictive control of a CNG-diesel RCCI engine

This study investigates the changing deterministic features of the cycle-resolved location of maximum pressure and its correlation with combustion phasing for dynamical transitions in the combustion of a CNG-Diesel RCCI engine. The investigation is performed using nonlinear dynamical and chaotic methods such as return maps, recurrence, and cross recurrence plots. The experiments are performed on a single-cylinder automotive engine operated in RCCI mode with the aid of the development ECU. The experiments are conducted by running the engine at a fixed engine speed of 1500 rpm and a load of 3 bar BMEP. Diesel fuel is injected directly into the cylinder by following a double injection strategy using an equal amount of fuel in both the pilot and main injections. The effect of the start of main injection timing of diesel on combustion dynamics is investigated at two different masses of CNG. The predominance of deterministic periodic features is discovered in the cycle-resolved dynamics of the engine combustion during the RCCI regime. Results show that with advancement in diesel injection timing, the mode of combustion shifts from conventional dual fuel to RCCI, and this shift is coupled to the onset of noisy periodic-2 bifurcations., The periodic-2 behavior even transforms to periodic-3 and 4 with an increasing advancement in diesel injection timing for engines operating with a higher CNG mass. For most of the operating conditions, the deterministic features in the location of maximum pressure are comparable with that of combustion phasing. Recurrence and cross recurrence plots-based methodology advocates for the existence of strong correlations or at least a phase synchronization between the location of maximum pressure and combustion phasing when the engine operates in the RCCI regime, irrespective of diesel injection timing and amount of port-injected CNG fuel. The presence of similar deterministic features in the location of maximum pressure and combustion phasing and a strong relationship between these two at intermediate diesel injection timings in the RCCI regime for both the CNG masses makes this regime most suitable for using the location of maximum pressure as a feedback/controlled parameter for model predictive control of the engine.

Characterization of metastable high pressure phase transition positions and its influence on the behavior of microbial destruction

Effect of perturbation factors on phase transition metastable positions of whole milk (4% fat content) and their influence on microbial destruction characteristics of non-pathogenic Escherichia coli inoculated in milk subjected to high pressure low temperature treatment were evaluated using a specially developed high pressure (HP) cooling system. Initially, the phase transition data of milk transitioning through the metastable phases were obtained and fitted successfully using Simon-like models as done in previous studies and polynomial formulas with R2 of 0.997 & 0.996 for ice I, and 0.989 & 0.989 for ice III, respectively. The phase transition position of milk was explored with 5% and 10% sodium chloride solution as perturbation sources, respectively. Results showed that the 5% sodium chloride solution can reduce the transition pressure of milk by 43 MPa and increase the transition temperature by 4.1 °C, so that the milk can achieve phase transition at lower pressure and higher temperature. Phase transition microbial destruction was characterized by discontinuity, mutation and segmentation when the phase transition pressure interval 250– 300 MPa was carefully refined. The inactivation amount of E. coli before the phase transition (250 MPa) was 1.11 log and the phase transition process itself brought an additional 1.26 log destruction of E. coli population in milk. Industrial relevanceHigh pressure low temperature (HPLT) phase change kinetics were employed to enhance microbial destruction. HPLT was established based on a self-cooling unit positioned inside conventional HP chamber offering opportunities for scale up and commercialization. The effectiveness of HPLT phase transition for Escherichia coli destruction was demonstrated. The related research in metastable state provides a reference point for commercial application of high-pressure-low-temperature technology for microbial destruction and quality enhancement.

Characteristics of denitrification and microbial community in respect to various H2 pressures and distances to the gas supply end in H2-based MBfR.

The hydrogen-based hollow fiber membrane biofilm reactor (H2-based MBfR) has shown to be a promising technology for nitrate (NO3––N) reduction. Hollow fiber membranes (HFM) operating in a closed mode in an H2-based MBfR often suffer from reverse gas diffusion, taking up space for the effective gas substrate and resulting in a reduction in the HFM diffusion efficiency, which in turn affects denitrification performance. In this work, we developed a laboratory-scale H2-based MBfR, which operated in a closed mode to investigate the dynamics of denitrification performance and biofilm microbial community analysis at different H2 supply pressures. A faster formation of biofilm on the HFM and a shorter start-up period were found for a higher H2 supply pressure. An increase in the H2 pressure under 0.08 MPa could significantly promote denitrification, while a minor increase in denitrification was observed once the H2 pressure was over 0.08 MPa. Sequencing analysis of the biofilm concluded that (i) the dominant phylum-level bacteria in the reactor during the regulated hydrogen pressure phase were Gammaproteobacteria and Alphaproteobacteria; (ii) when the hydrogen pressure was 0.04–0.06 MPa, the dominant bacteria in the MBfR were mainly enriched on the hollow fiber membrane near the upper location (Gas inlet). With a gradual increase in the hydrogen pressure, the enrichment area of the dominant bacteria in MBfR gradually changed from the upper location to the distal end of the inlet. When the hydrogen pressure was 0.10 MPa, the dominant bacteria were mainly enriched on the hollow fiber membrane in the down location of the MBfR.

Impact of self-tonometry on glaucoma treatment decision.

The aim of this study was to examine the impact of self-tonometry on clinicians' decision in glaucoma treatment. Medical records of 133 patients who had performed self-tonometry using iCare® Home between January and December 2019 were retrospectively reviewed. Inclusion criteria were as follows: age over 18 years, all types of glaucoma, as well as ocular hypertension and glaucoma suspect, compliance with tonometer manufacturer's recommendations and monitoring over at least 2 days. The data consisted of age, gender, diagnosis, visual field index, rate of progression and type of treatment pre- and post-intraocular pressure (IOP) phasing. The following IOP measurements were used to calculate the mean and maximum IOP, and range over each day and consecutive days: Goldmann applanation tonometry (GAT) measurements from referral and training visits and iCare® Home measurements made by the trainers and the patients themselves. A total of 90 patients were included. Clinicians were satisfied with the actual treatment in 54.4% of the cases. There was a statistically significant difference between the clinicians' decision to maintain same treatment or to escalate therapy for all the mean and maximum IOPs measured on each single day and over a 2- or 3-day period (p< 0.002). Our results suggest that the presence of high IOP values obtained with self-tonometry supports an intensification of glaucoma treatment. Self-tonometry provides clinicians with an important complement for clinical decision-making, and under- or over-treatment may be avoided for the benefit of patients.

Four-Dimension Seismic Analysis in Carbonate: A Closed Loop Study

Four-dimensional seismic analysis is an effective reservoir surveillance tool to track the changes of fluid and pressure phases in the oil and gas reservoirs over time of the baseline and monitoring seismic acquisition. In practice, the 4D seismic signal associated with such changes may be negligible, especially in heterogeneous carbonate reservoirs. Therefore, 4D seismic analysis is a model for integrating various disciplines in the oil and gas industry, such as seismic, petrophysics, reservoir engineering, and production engineering. In this study, we started the 4D seismic workflow with a 1D well-based 4D feasibility study to detect the likelihood of 4D signals before performing 4D seismic co-processing of the baseline and monitoring surveys starting from the seismic field data of both datasets. As part of a full 4D seismic co-processing of the baseline and monitor surveys, 4D seismic metric attributes were analyzed over the survey area to measure the improvement in seismic acquisition repeatability for the scarce 1994 baseline seismic and the 2014 monitor seismic survey. For the monitor survey, a 4D time-trace shift was performed using the baseline survey as a reference to measure the time shifts between the baseline and monitor surveys at 20-year intervals. The 4DFour-dimensional dynamic trace warping was followed by a 4D seismic inversion to compare the 4D difference in the seismic inverted data with the difference in seismic amplitude. The seismic inversion helped overcome noise, multiple contaminations, and differences in dynamic amplitude range between the baseline and monitor seismic surveys. We then examined the relationship between well logs and seismic volumes by predicting a volume of log properties at the well locations of the seismic volume. In this method, we computed a possibly nonlinear operator that can predict well logs based on the properties of adjacent seismic data. We then tested a Deep Feed Forward Neural Network (DFNN) on six wells to adequately train and validate the machine learning approach using the baseline and monitoring seismic inverted data. The objective of trying such a deep machine learning approach was to predict the density and porosity of both the baseline and the monitoring seismic data to validate the accuracy of the 4D seismic inversion and evaluate the changes in reservoir properties over a time-lapse of 20 years of production from 1994 to 2014. Finally, we matched the 4D seismic signal with changes in reservoir production properties, investigating the mechanism underlying the observed 4D signal. It was found that the detectability of 4D signals is primarily related to changes in fluid saturation and pressure changes in the reservoir, which increased from 1994 to 2014. This innovative closed-loop research proved that the low repeatability of seismic acquisition can be compensated by optimal 4D seismic co-processing with a complete integration workflow to assess the reliability of the 4D seismic observed signal.

Tailoring of thermal expansion and phase transition temperature of ZrW2O8 with phosphorus and enhancement of negative thermal expansion of ZrW1.5P0.5O7.75

ZrW2O8 is a typical isotropic negative thermal expansion material with cubic structure. However, quenching preparation, pressure phase transition and metastable structure influence its practical applications. Adopting P to part-substitute W for ZrW2−x P x O8–0.5x has decreased the sintering temperature and avoided the quenching process. When x = 0.1, ZrW1.9P0.1O7.95 with a stable cubic structure can be obtained at 1150 °C. The thermal expansion coefficient is tailored with the P content, and phase transition temperature is lowered. When x = 0.5, thermal expansion coefficient attains −13.6 × 10−6 °C−1, ZrW1.5P0.5O7.75 exhibits enhance negative thermal expansion property. The difference of electronegativity leads to the decrease of phase transition temperature with the increase of P content. The different radii of ions lead to new structure of materials when P substitutes more. The results suggest that the P atom plays the stabilization role in the crystal structure of ZrW2−x P x O8–0.5x .

Calibration of sound intensity instruments based on the double coupler technology

The calibration of sound intensity instruments—in particular, with respect to instruments’ sensitivity to both sound intensity and particle velocity in the rated frequency range—is challenging for laboratories worldwide. The commonly used approach is to measure the pressure sensitivity and phase difference of a pair of microphones, and electrically test the analyzer. The intensity instrument cannot be fully calibrated if only the components of the intensity measurement system are calibrated. Ideally, the sound intensity instrument should be calibrated as a system, along with all its parameters being compared with traceability to recognized standards; this will increase the confidence in the validity of measurement results. Currently, calibration below 50 Hz is still not feasible. To meet this requirement, the Beijing Aerospace Institute of Metrology and Measurement Technology has developed a double coupler calibration system capable of generating an intensity or particle velocity level of known amplitude and direction traceable to recognized standards. This paper covers the principle of the double coupler technique, design of the system, and generation of the reference intensity signal. The calibration results are in good agreement with the theoretical calculation results.

Comprehensive application analyses of elastic models and viscoelastic models in transient flows in polymeric pipelines

Abstract Based on the MOC (Method of Characteristics), the applicabilities of both the elastic models of the SF (Steady Friction), the CB-UF (Convolution-Based Unsteady Friction) and the MIAB-UF (Modified Instantaneous Acceleration-Based UF), and the viscoelastic models of the SF-VE (SF-Viscoelasticity), the CB-UF-VE (Convolution-Based Unsteady Friction-Viscoelasticity) and the MIAB-UF-VE (Modified Instantaneous Acceleration-Based UF-Viscoelasticity), are investigated for hydraulic transients induced by a downstream rapid valve closure in a polymeric pipeline. The predicted results by the elastic models are very different from the experimental data, whereas the predicted pressure peaks and phases by the viscoelastic models agree well with the experimental data because considering the pipe–wall creep effect, the CB-UF-VE and the MIAB-UF-VE generate better results than the SF-VE. The creep effects near the first pressure peak are captured well by the viscoelastic models. The analyses of the contributions of different factors to pressure attenuation show that for transient flows in polymeric pipelines, the effect of VE is greater than that of the CB-UF and MIAB-UF. The spectrum analyses show that the pressure amplitudes and harmonic frequencies by the elastic models match badly with the experimental data, whereas those by the viscoelastic models match well with the experimental data. The harmonic frequencies by the MIAB-UF-VE are the best, followed by the CB-UF-VE, and are worst by the SF-VE.

Theoretical investigation of compressed hexagonal and rock-salt structures of molybdenum and chromium carbides

This research paper reports the structural, electronic, elastic anisotropy, and thermodynamic characteristics of Molybdenum and Chromium Carbides (MoC and CrC) at zero and under high pressures. We consider both hexagonal tungsten carbide phase (WC) and rock-salt (NaCl) structures. Our investigation is performed using the first-principles pseudo-potential plane waves method. The fundamental ground state is the hexagonal (WC) phase for MoC and CrC compounds. MoC is relatively more ionic than CrC. The investigated materials are brittle in the WC phase and ductile in the RS phase for pressures below 30 GPa. MoC and CrC are hard materials and anisotropic in sound velocity. Phonon spectra are reported for both compounds in a WC and NaCl at zero-pressure and high pressures. Ideal stoichiometric WC crystals of MoC and CrC are predicted to be dynamically stable. The pressure and temperature dependence of various macroscopic thermodynamic parameters of MoC and CrC compounds are also discussed.

Phase transitions and suppression of magnetoresistance in WTeSe x system

X-ray diffraction, Raman spectroscopy, and electrical resistivity measurements on polycrystalline WTeSe x () reveal a T d - structural phase transition and suppression of magnetoresistance at x = 0.2. These phenomena are consistent with the pressure phase diagram of WTe2. However, chemical pressure due to substitution of smaller Se ion cannot generate pressure required for the phase transition. Strain induced by sample inhomogeneity is believed to be a trigger to the behaviors. In agreement with previous predictions and reports, a mixed phase of and 2H structures was also detected in Se-rich samples. Coincidentally at x = 0.2, electrical resistivity analysis suggests a phase transition from a metallic phase to a nonmetallic phase that is possibly a topological-insulating phase.

Stress State Change and Fault-Slip Tendency Assessment Associated with Gas Injection and Extraction in the Hutubi (China) Underground Gas Storage

Summary The Hutubi (HTB) gas reservoir in northwest China was active in production from 1998 to 2012; beginning in 2013, it was used for gas storage. Several earthquakes occurred during the early operation of the Hutubi underground gas storage (HTB-UGS) project, so it is important to explore their relationship with gas injection and extraction from the viewpoint of stress state change and faulting susceptibility. We study the evolution of the stress state and slip tendency associated with the operation of the HTB-UGS to understand the relationship between pore pressure variation and induced seismicity. We constrain the stress state in the reservoir at the time of cessation of production in 2012 using image-logged wellbore breakouts. We then estimate stress state variation over time as a result of pore pressure changes, based on the assumption of poroelastic coupling between horizontal elastic stresses and pore pressure. The maximum principal stress in the reservoir region before the HTB-UGS operation is oriented N23°±6°E, which is consistent with that of the prevailing tectonic stress derived from earthquake focal mechanisms. Our results show that the vertical stress (Sv) and the minimum horizontal principal stress (Shmin) were initially similar in magnitude before petroleum production; the magnitude of Shmin gradually decreased during petroleum production. Gas injection, initiated in 2013, raised the Shmin magnitude, returning it to approximately that of Sv. We use the estimated variations in the reservoir stress state over time to calculate temporal changes in slip tendency of the main faults in the reservoir. The fault-slip tendency decreased continuously with petroleum production and then increased with gas injection. The first earthquake swarm associated with gas injection occurred approximately 2 months after the start of injection, possibly due to the slow pore pressure diffusion. Thereafter, earthquakes were induced whenever gas was injected. Our assessment of slip tendency suggests that earthquake swarms were induced during increasing pore pressure phases when slip tendency reached a value of 0.43 ± 0.04. The maximum allowable pore pressure for avoiding earthquakes (ML &amp;gt; 1.5) is 29.0 ± 4.5 MPa, which might increase through stress adjustments and a newly attained balance. This study provides a possible method for induced earthquake analysis associated with gas injection and extraction from the perspective of stress state change and faulting susceptibility.

Influence of tip leakage flow on the aerodynamic damping of compressor blade torsional vibration

Based on harmonic balance calculation technology with a single-passage phase-lag periodic boundary, the influence of tip gap size on the aerodynamic damping characteristics of rotor for first-order torsional vibration is analyzed with energy method. This research shows that the aerodynamic damping coefficient of the blade has a parabolic distribution law of first decreasing and then increasing with the increase of the tip clearance size. There is a most dangerous clearance value of torsional flutter characteristics in the blade, and the aerodynamic damping under this clearance is 12.67 % lower than the maximum damping value. The influence of the leakage flow on the time-averaged flow field near the blade tip leads to significant differences in the local aerodynamic work. In addition, the effect of leakage flow on the amplitude and phase of the local first-order unsteady pressure also bring about a significant influence on local aerodynamic work near blade tip.

Thermal unrest of a fumarolic field tracked using VIIRS imaging bands: The case of La fossa crater (Vulcano Island, Italy)

Detecting precursory signals before an eruption is one of the main objectives of applied volcanology. Among these signals, the variation of the emitted heat flux is certainly an important indicator of a state of disequilibrium within the magmatic system. Here we report the results of a detailed analysis of VIIRS (Visible Infrared Imaging Radiometer Suite) imaging bands (at 375 m spatial resolution) focused on measuring the Volcanic Radiative Power (VRP) emitted by the fumarole field of La Fossa crater (Vulcano Island, Italy) over the past decade (2012–2022). The analysis reveals that the long-term, steady-state VRP (baseline ∼0.17 MW) was perturbed in 2020–2021 when a prolonged period of lower than normal (&amp;lt;-2σ) radiant flux preceded the major unrest phase that began in mid-September 2021. By early October the anomalous VRP had peaked at ∼1.2 MW (6–8 times the baseline) then started to gradually decline in the following months. A subsequent thermal pulse was recorded in May–July 2022 and was accompanied by a period of seawater discoloration that affected the Baia di Levante (a shallow sea bay ∼1.4 km north of La Fossa crater). The concomitance of these phenomena suggests the occurrence of a second pressurization phase driven by the arrival of deep magmatic fluids within both the central and distal degassing fumarolic zones. These results provide a complementary, important contribution to the understanding of the unrest of La Fossa crater and highlight the potential of VIIRS in detecting pre-eruptive signals at other poorly-monitored volcanoes characterized by high-temperature fumarolic activity.

Impact of log(Kow) Value on the Extraction of Antibiotics from River Sediments with Pressurized Liquid Extraction

The quantification of antibiotics (ABs) in sediments is an analytical challenge, but at the same time, it is indispensable to understand the fate of ABs in aquatic systems such as rivers. The aim of this study was to develop a comprehensive method to determine 19 ABs classified as macrolides, sulfonamides, fluoroquinolones, tetracyclines, clindamycin and trimethoprim in river sediments, using a combination of pressurized liquid extraction and solid phase extraction with the separation and detection with liquid chromatography coupled with mass spectrometry. Our results showed that the physical-chemical properties (e.g., log(Kow) value) of the analytes affected the extraction efficiency. Therefore, we propose to order ABs based on their log(Kow) values instead of traditional classification (macrolides, sulfonamides etc.) to select a suitable extraction solvent. ABs with log(Kow) values below zero (mainly fluoroquinolones and tetracyclines) were difficult to extract with all of the tested protocols compared to ABs with a log(Kow) larger than zero. After comparing different extraction protocols for ABs from solid and sediments, we concluded that recoveries in the range of 0.8 to 64.8% could be achieved for ABs with a log(Kow) value larger than zero using a mixture of acetonitrile and 50 mM phosphoric acid (50/50, v/v) in two extraction cycles at 100 °C.

Pressure-Driven Phase Transition in Two-Dimensional Perovskite MHy2PbBr4

The application of high pressure allows tuning physicochemical properties of materials by changing interatomic distances. Pressure may also induce structural phase transitions into new phases with enhanced or novel functional properties. Here, we report complementary high-pressure single-crystal X-ray diffraction, Raman spectroscopy, and optical studies of a two-dimensional (2D) perovskite, MHy2PbBr4, comprising a very small spacer cation (methylhydrazinium, MHy+). This crystal exhibits highly desired ferroelectric and extraordinary multiple linear and nonlinear optical (NLO) properties. Single-crystal X-ray diffraction shows that MHy2PbBr4 undergoes an unusual Pmn21 → P21 phase transition near 4 GPa, associated with the extrusion of some MHy+ cations from the interlayer space into voids located within the inorganic sheets, not reported for any 2D hybrid perovskite. The transport of counter cations leads to a significant increase of Pb–NH2 interactions, an unprecedented threefold increase of positive linear compressibility perpendicular to the polyanionic layers and a large negative linear compressibility of −22.39 TPa–1 within the layers. The Raman data confirm the association of the phase transition with strong distortion of the crystal structure and reorganization of the hydrogen bond network, while the absorption spectra of the compressed ambient-pressure Pmn21 phase show the band gap narrowing, followed by its widening in the high-pressure P21 phase. A similar change in the pressure dependence from a red shift to a blue shift is also observed for the free-exciton (FE) photoluminescence (PL). Furthermore, the pressure-induced phase transition leads to a giant enhancement of PL intensity, especially pronounced for the broad-band emission attributed to the self-trapped excitons (STEx). We attribute the effects, observed in absorption and PL spectra, to the shortening of Pb–Br bonds in the ambient pressure phase and increased distortion of the inorganic layers and tilts of PbBr6 octahedra in the high-pressure phase. Overall, our results for a 2D hybrid compound comprising very small spacer cations extend the understanding of the pressure effect on the properties of 2D hybrid perovskites in general and demonstrate a very different behavior under compression compared to the analogues with large organic cations. They revealed that the structure–strain mechanism can be used for engineering new high-pressure phases with unusual structural, mechanical, and optoelectronic properties.

Multi-Tone Piano Transcription Based on Visualization and Knowledge Recognition Algorithm

Scientific computing visualization is also known as visualization. In an academic sense, visualization is a way of computing. It can convert data into intuitive geometric images, making it easier to understand. Visualization is the use of computer graphics and image processing techniques. It is a technical means to convert piles of seemingly disorganized data into graphics or images through special computer methods. Recording is the process of recording sound signals on a medium. Specifically, it is the process of converting sound into electrical signals through microphones and amplifiers and recording them with different materials and techniques. Piano tuning is the adjustment of the strings so that they reach a certain high pitch. This paper aims to study the analysis and evaluation of multi-tone piano transcriptions based on scientific computing visualization and knowledge recognition algorithms. It expects to improve the quality of piano recording with the support of scientific visualization technology and knowledge recognition algorithm. This paper briefly explains the big data, and on this basis, the visual data mining technology is mentioned, and the current situation in the visual data mining is explained. A matrix calculation of the characteristic matrix of piano timbres was carried out to achieve the resynthesis of the 25th harmony in piano timbres electronically. The results of the trials in this article demonstrate that when the Gaussian number changes to 5 during the recording process, the difference that exists of the acoustic voltage intensity and the noise level phase is clearly diminished. When the Gauss figure is 10, there is an inversion of the value of the sound pressure phase.

Moisture transfer and drying stress of eucalyptus wood during supercritical CO2 (ScCO2) dewatering and ScCO2 combined oven drying

Supercritical CO2 (ScCO2) dewatering is a lumen water expulsion process, in which CO2 is cycled between atmospheric pressure and supercritical phase and results in a fast expulsion of free water. In this study, specimens of 100 mm length Eucalyptus exserta F.V. Muell. wood were dewatered using ScCO2, then the dewatered and un-dewatered wood were dried in oven at 100 °C to investigate moisture transfer and drying stress. The ScCO2 dewatering was very fast. When the moisture content (MC) was over 40%, the MC distribution and gradient after dewatering and oven drying were different. The oven drying MC showed a ring contour distribution, but the ScCO2 showed a higher MC in one side and a lower MC in the opposite; the oven drying MC gradient was great in the middle and small in the end part of wood, but the ScCO2 MC gradient was small and roughly consistent. The oven drying moisture migration rates along the fiber and transverse directions were similar; however, the ScCO2 migration rate was faster in the transverse directions. The MC distributions of the dewatered and un-dewatered wood after oven drying were similar at 30% MC. The ScCO2 dewatering reduced wood residual stress, and it affected the stress development in the subsequent oven drying.