Hydrostatic Environment Research Articles

Quasihydrostatic versus nonhydrostatic pressure effects on the electrical properties of NiPS3

We report combined x-ray diffraction (XRD) and electrical transport studies of the van der Waals (vdW) insulator ${\mathrm{NiPS}}_{3}$ to elucidate a pressure-induced insulator-to-metal transition (IMT). On application of quasihydrostatic pressure, two successive structural transitions occur at 10 and 29.4 GPa, as evidenced by the XRD and resistivity measurements. The concomitant IMT with a monoclinic-to-trigonal structural transition near 29.4 GPa turns out to be a common feature of the ${\mathrm{MPS}}_{3}$ family (M=transition metals). Under uniaxial-like pressure, the critical pressure for IMT is drastically reduced to $P=12.5$ GPa. These results showcase that the IMT is susceptible to strain and hydrostatic environments and that pressure offers a new venue to control a dimensional crossover in layered vdW materials.

Research on the influence of hydrostatic pressure on the sensitivity of bionic cilia MEMS vector hydrophone

Hydrophones are one of the main sensors for underwater acoustic signal detection, and their positioning accuracy is closely related to their sensitivity. However, in practice, hydrophones need to work in different depths of water environment. The ciliated MEMS vector hydrophone has a four-beam structure and has a certain anti-interference ability against hydrostatic pressure. However, due to the manufacturing process and other reasons, there may be certain errors in the production of varistors, which leads to the hydrophone's resistance to hydrostatic pressure. The resistance to the impact is reduced. Therefore, studying the influence of hydrostatic pressure environment on the sensitivity of MEMS vector hydrophones is of great significance to the application of MEMS vector hydrophones. According to the application environment of MEMS vector hydrophone, the sensitivity of MEMS vector hydrophone is studied in this paper within the range of hydrostatic pressure 1 atm ∼ 12 MPa. In this paper, the influence of hydrostatic pressure on the sound transmission loss and piezoresistor are studied to theoretically verify that the hydrostatic pressure has little effect on the sensitivity of MEMS vector hydrophone. It is verified by COMSOL5.6 software simulation that the sensitivity changes within the pressure range of 1 dB. In order to facilitate the experiment of the MEMS vector hydrophone in the hydrostatic environment, this paper proposed a method of combining an external sound source with a marine environment simulation test machine. It is concluded that within the test pressure range, the sensitivity change of the MEMS vector hydrophone fluctuates within ±1 dB.

Low-frequency broadband absorption of semi-active composite anechoic coating with subwavelength piezoelectric arrays in hydrostatic environments

Considering the influence of hydrostatic pressure on geometric parameters of a lining, this paper first proposes a complete global four-terminal acoustic theoretical prediction method based on phenomenological theory for a semi-active composite coating with subwavelength piezoelectric arrays in deep-sea environment, aiming at exploring the energy dissipation mechanisms and broadening the low-frequency sound-absorbing bandwidth. The Neo-Hookean material model is incorporated into the phenomenological theory to analyze the finite deformation of rubber layers under hydrostatic load. Then, the global acoustic model is established by combining the effective medium method, shunt damping technique, and wave propagation theory in layered media. Moreover, the degraded validations are developed by FE simulation and hydroacoustic impedance tube experiment, and the influences of submergence depth and shunt circuit on the absorption characteristics are explored theoretically. It is expected to break the lower limit frequency of low-frequency sound-absorbing from 500 Hz to 200 Hz, and to expand the upper limit frequency thanks to the multi-modal resonant energy consumption mechanism of distributed circuits.

Sedimentary Facies of the Longmaxi Formation Shale Gas Reservoir in the Weiyuan Area Based on Elemental Characteristics

The Lower Silurian Longmaxi Formation in the southern Sichuan Basin is composed of a series of dark carbonaceous shales deposited in a hydrostatic shelf reduction environment. In this study, the ratio of uranium to thorium (U/Th), the total organic carbon (TOC), and the biological silicon content (SiBio) were selected as the characteristic parameters to precisely analyze the sedimentary environment and its impact on reservoir quality. The results show that the Weiyuan area in the Early Silurian Longmaxi period experienced two transgression-regression cycles, forming two third-class sequences, SSQ1 and SSQ2, which can be divided into six sedimentary microfacies: organic-rich siliceous argillaceous shelf, organic-rich silicon-containing argillaceous shelf, organic-rich silty argillaceous shelf, deep-water silty argillaceous shelf, shallow-water silty argillaceous shelf, and shallow-water argillaceous silty shelf microfacies. The organic-rich siliceous argillaceous shelf and organic-rich silicon-containing argillaceous shelf microfacies developed in the deepest transgressive system tract (TST1), with high U/Th, high TOC, and high SiBio, which are identified as the main control facies for reservoir development. These two microfacies are located in the middle of the study area, while a transition occurs in the east affected by the Neijiang Uplift. According to the classification criteria proposed in this article, the favourable shale gas reservoirs in Weiyuan area are characterized with high U/Th (>1.25), high TOC (>3%), and high SiBio (>15%). This paper proposed an evaluation method for shale sedimentary facies based on elemental and electrical logging characteristics, avoiding the limitations of core samples, which makes the quantitative division of shale sediments and the efficient recognition of high-quality reservoirs available. It is of great significance for delineating the potential production areas in the study area and beneficial for the scaled development of shale gas reservoirs.

Photogranulation in a Hydrostatic Environment Occurs with Limitation of Iron.

Filamentous cyanobacteria are an essential element of oxygenic photogranules for granule-based wastewater treatment with photosynthetic aeration. Currently, mechanisms for the selection of this microbial group and their development in the granular structure are not well understood. Here, we studied the characteristics and fate of iron in photogranulation that proceeds in a hydrostatic environment with an activated sludge (AS) inoculum. We found that the level of Fe in bulk liquids (FeBL) sharply increased due to the decay of the inoculum but quickly diminished along with the bloom of microalgae and the advent of the oxic environment. Iron linked with extracellular polymeric substances (FeEPS) continued to decline but reached steady low values, which occurred along with the appearance of granular structure. Strong negative correlations were found between FeEPS and the pigments specific for cyanobacteria. Spectroscopies revealed the presence of amorphous ferric oxides in pellet biomass, which seemed to remain unaltered during the photogranulation process. These results suggest that the availability of FeEPS in AS inoculums-after algal bloom-selects cyanobacteria, and the limitation of this Fe pool becomes an important driver for cyanobacteria to granulate in a hydrostatic environment. We therefore propose that the availability of iron has a strong influence on the photogranulation process.

Pressure-Induced Structural Phase Transition and Metallization in Ga2Se3 Up to 40.2 GPa under Non-Hydrostatic and Hydrostatic Environments

A series of investigations on the structural, vibrational, and electrical transport characterizations for Ga2Se3 were conducted up to 40.2 GPa under different hydrostatic environments by virtue of Raman scattering, electrical conductivity, high-resolution transmission electron microscopy, and atomic force microscopy. Upon compression, Ga2Se3 underwent a phase transformation from the zinc-blende to NaCl-type structure at 10.6 GPa under non-hydrostatic conditions, which was manifested by the disappearance of an A mode and the noticeable discontinuities in the pressure-dependent Raman full width at half maximum (FWHMs) and electrical conductivity. Further increasing the pressure to 18.8 GPa, the semiconductor-to-metal phase transition occurred in Ga2Se3, which was evidenced by the high-pressure variable-temperature electrical conductivity measurements. However, the higher structural transition pressure point of 13.2 GPa was detected for Ga2Se3 under hydrostatic conditions, which was possibly related to the protective influence of the pressure medium. Upon decompression, the phase transformation and metallization were found to be reversible but existed in the large pressure hysteresis effect under different hydrostatic environments. Systematic research on the high-pressure structural and electrical transport properties for Ga2Se3 would be helpful to further explore the crystal structure evolution and electrical transport properties for other A2B3-type compounds.

Hydrogen permeation under high pressure conditions and the destruction of exposed polyethylene-property of polymeric materials for high-pressure hydrogen devices (2)-

Aiming to elucidate physical property affecting to hydrogen gas permeability of polymer materials used for liner materials of storage tanks or hoses and sealants under high-pressure environment, as model materials with different free volume fraction, five types of polyethylene were evaluated using two methods. A convenient non-steady state measurement of thermal desorption analysis (TDA), and steady-state high-pressure hydrogen gas permeation test (HPHP) were used both under up to 90 MPa of practical pressure. The limit of TDA method of evaluation for the specimens suffering fracture during decompression process after hydrogen exposure was found. Permeability coefficient decreased with the decrease of diffusion coefficient under higher pressure condition. Specific volume and degree of crystallinity under hydrostatic environment were measured. The results showed that the shrinkage in free volume caused by hydrostatic effects of the applied hydrogen gas pressure decreases diffusion coefficient, resulting in the decrease of permeability coefficient with the pressure rise.

An Idealized Physical Model for the Severe Convective Storm Environmental Sounding

AbstractThis work develops a theoretical model for steady thermodynamic and kinematic profiles for severe convective storm environments, building off the two-layer static energy framework developed in work by Agard and Emanuel. The model is phrased in terms of static energy, and it allows for independent variation of the boundary layer and free troposphere separated by a capping inversion. An algorithm is presented to apply the model to generate a sounding for numerical simulations of severe convective storms, and the model is compared and contrasted with that of Weisman and Klemp. The model is then fit to a case-study sounding associated with the 3 May 1999 tornado outbreak, and its potential utility is demonstrated via idealized numerical simulation experiments. A long-lived supercell is successfully simulated with the historical sounding but not the analogous theoretical sounding. Two types of example experiments are then performed that do simulate a long-lived supercell: 1) a semitheoretical experiment in which a portion of the theoretical sounding is modified to match the real sounding (low-level moisture); 2) a fully theoretical experiment in which a model physical parameter is modified (free-tropospheric relative humidity). Overall, the construction of this minimal model is flexible and amenable to additional modifications as needed. The model offers a novel framework that may be useful for testing how severe convective storms depend on the vertical structure of the hydrostatic environment, as well as for linking variability in these environments to the physical processes that produce them within the climate system.

Comparative Compressibility of Smectite Group under Anhydrous and Hydrous Environments.

High-pressure synchrotron X-ray powder diffraction studies of smectite group minerals (beidellite, montmorillonite, and nontronite) reveal comparative volumetric changes in the presence of different fluids, as pressure transmitting media (PTM) of silicone oil and distilled water for anhydrous and hydrous environments at room temperature. Using silicone oil PTM, all minerals show gradual contraction of unit-cell volumes and atomistic interplane distances. They, however, show abrupt collapse near 1.0 GPa under distilled water conditions due to hydrostatic to quasi-hydrostatic environmental changes of water PTM around samples concomitant with the transition from liquid to ICE-VI and ICE-VII. The degrees of volume contractions of beidellite, montmorillonite, and nontronite up to ca. 3 GPa are ca. 6.6%, 8.9%, and 7.5% with bulk moduli of ca. 38(1) GPa, 31(2) GPa, and 26(1) GPa under silicone oil pressure, whereas 13(1) GPa, 13(2) GPa, and 17(2) GPa, and 17(1) GPa, 20(1) GPa, and 21(1) GPa under hydrostatic and quasi-hydrostatic environments before and after 1.50 GPa, respectively.

Buckling, vibration, and energy solutions for underwater composite cylinders

This study presents closed-form solutions for the critical buckling pressures and characteristic frequencies of underwater composite cylinders. The analytical solutions were derived using the full stiffness definitions from composite laminate theory, making them suitable for symmetric, asymmetric, hybrid, and/or double-shell (sandwich) cylindrical composite structures. These closed-form solutions were developed for critical buckling pressures in a hydrostatic environment as well as for critical buckling energy in a dynamic environment with combined hydrostatic and transient loads. Also, the characteristic frequencies were derived for a submerged and pressurized environment to account for added fluid mass and hydrostatic pressures. Computational and experimental data were used to validate the derived analytical work. The resulting solutions for critical buckling pressures agreed with numerical and experimental results for single-shell cylindrical structures. Moreover, for double-shell cylindrical structures with foam cores (sandwich structures), the collapse pressure is shown to be proportional to the core’s transverse shear modulus. The solutions were suitable for predicting the collapse pressure for sandwich structures with relatively low-density cores. Lastly, solutions for estimating the energy emitted during an implosion event and the energy required for buckling in sub-critical pressure environments were also derived and validated with the experimental data.

Hydrostatic implosion of composite cylinders in an open-ended confining structure

The results, findings, and analytical investigation of an experimental study conducted on the hydrostatic implosion of filament wound carbon fiber epoxy composite tubes within partial confinement are presented. Implosion in geometries varying in length and diameter is initiated within a tubular confining structure with one end closed and one end open to a free-field, hydrostatic environment. Structural deformation behavior is captured and quantified using high speed cameras in conjunction with 3D digital image correlation (DIC). Water hammer pulses resulting from implosion are measured at various locations in the confining chamber and are shown to behave as a damped harmonic oscillator. Water hammer behavior is thus experimentally characterized for each geometry by determining average values of amplitude ΔPmax, frequency of oscillation f, and damping ratio ξ. It is shown that f decreases with increasing implodable volume to confinement volume ratio Vi/Vc, and is theoretically determined with excellent correlation to experimental results. Finally, amplitude of oscillation ΔPmax is theoretically determined and used in conjunction with theoretically determined f and experimentally determined ξ to fully define the hammer wave oscillations resulting from partially-confined implosion.

Abnormal Formation Pressure in the Sulaiman Province, Pakistan: An Insight into Factor Affecting Reservoirs in a Compressional Strike-Slip Region

Various stratigraphic strata encountered in wells drilled in the Sulaiman Depression (SD) of Pakistan are characterized by the development of abnormal formation pressures. An assessment of abnormal pressures is carried out using conventional well logging method and Daines fracture gradient (FG) model, to obtain modified pressure estimates and to get a new insight into the effect of high pressures in the future hydrocarbon exploratory activities in the region. The conventional well data were used to determine the stress environment based on the caliper log (CALI) information. The overburden gradients (OBGrads), pore pressure gradients (PPGs), and fracture gradients (FGs) were derived from studied wells, using resistivity and sonic (DT) logs, followed by Poisson’s ratio curve for various facies types. Findings from the study confirm that wells from the SD show high FGs, whereas the areas in the west (SFB) and northeast (ZA) indicate normal pressure (hydrostatic) environment. The study concludes that tectonic activities and high rates of sedimentation during the Cretaceous (145–65 million years ago) and the Paleogene (65–23 million years ago) have led to the development of overpressure by disequilibrium compaction. This study identified stress regime at deeper level of the Cretaceous and high-pressure intervals at the Paleogene, concluding three distinct rock units of the Cretaceous, Paleogene, and Neogene.

Dynamic modeling and adaptive fuzzy sliding mode control for multi-link underwater manipulators

This paper proposes a method of dynamic modeling and a modified sliding mode control algorithm applied on multi-link underwater manipulators. Firstly, combining Lagrange equation with Morison formula, we establish the dynamic model of a 3 DOF underwater manipulator in hydrostatic environment. Water resistance, additional mass force and buoyancy are calculated to discuss the influences to all joints working in underwater environment. Next, we presented an improved sliding mode control strategy for the accurate trajectory tracking control of underwater manipulator. To address the issue of chattering problem for sliding mode control and unavailable normalization factor, an adaptive fuzzy sliding mode is proposed. In order to validate the effectiveness of the presented controller, two simulations are conducted. The results are compared with other control algorithm and show that no matter in convergence rate or control accuracy, the proposed controller has better control effect.

Characterization of metallization and amorphization for GaP under different hydrostatic environments in diamond anvil cell up to 40.0 GPa.

High-pressure phase stability of gallium phosphide was explored under different hydrostatic environments up to 40.0 GPa in a diamond anvil cell. Two irreversible phase transitions from the semiconductor to metal to an amorphous state appear at 19.8 and 31.5 GPa and as well as 22.6 and 35.3 GPa under nonhydrostatic and hydrostatic environments, respectively. Furthermore, the hysteresis effect of the high-pressure phase transition of a sphalerite-structure compound under a hydrostatic environment was disclosed. All of the obtained results can provide new insight into the underlying structural evolution and electrical transport characteristics for the semiconducting compound at different hydrostatic environments.

Characterization of the pressure-induced phase transition of metallization for MoTe2 under hydrostatic and non-hydrostatic conditions

This study reported a pressure-induced metallization for molybdenum tellurium under different pressure environments up to ∼25.9 GPa through a series of experiments and first-principles theoretical calculations. This metallization was closely related to the gradual closure of bandgap rather than the structural phase transition. Under the non-hydrostatic environment, the metallization point was ∼12.5 GPa and irreversible, while it occurred at a higher pressure of ∼14.9 GPa and was reversible under the hydrostatic environment. We ascribed these discrepancies to the strong deviatoric stress, which reinforced the Te-Te interactions and caused the permanent plastic deformation of the interlayer spacing.

Effect of hydrostatic pressure on protective bubble characteristic and weld quality in underwater flux-cored wire wet welding

The metal transfer and protective bubble images, real-time electric signal data and weld appearance were obtained in different simulated water depth wet flux-cored arc welding. The electric signal results showed that the high hydrostatic environment deteriorated the stability of the wet welding process. The poor weld appearances with porosity were displayed when it was welded in deep water. The weld dilution rate descended from 51% to 40% with increasing water depth from 0.5 m to 90 m because of arc shrinking and heat input reduction. The reduction of protective bubble size and duration caused by high water pressure was unable to maintain a stable burning arc. With increasing water depth, the increase of pores in welds strongly deteriorated the mechanical property of joints. The process of gas generation and its escape from the droplet during the droplet transfer were observed. The rise of pressure compressed gas pores and prevented the gas from escaping, which resulted in the increase of pores.

Correlatively Dependent Lattice and Electronic Structural Evolutions in Compressed Monolayer Tungsten Disulfide.

Transition-metal dichalcogenides (TMDs) are promising materials for optoelectronic devices. Their lattice and electronic structural evolutions under high strain conditions and their relations remain open questions. We exert pressure on WS2 monolayers on different substrates, namely, Si/SiO2 substrate and diamond anvil surface up to ∼25 GPa. Structural distortions in various degree are disclosed based on the emergence of Raman-inactive B mode. Splits of out-of-plane B and A1' modes are only observed on Si/SiO2 substrate due to extra strain imported from volume decrease in Si and corrugation of SiO2 surface, and its photoluminescence (PL) quenches quickly because of decreased K-K transition by conspicuous distortion of Brillouin zone. While diamond anvil surface provides better hydrostatic environment, combined analysis of PL and absorption proves that pressure effectively tunes PL emission energy and enhances Coulomb interactions. Knowledge of these distinct pressure tunable characteristics of monolayer WS2 improves further understanding of structural and optical properties of TMDs.

Origin of superconductivity in the Weyl semimetal WTe2 under pressure

Tungsten ditelluride (WTe2) has attracted significant attention due to its interesting electronic properties, such as the unsaturated magnetoresistance and superconductivity. Recently, it has been proposed to be a new type of Weyl semimetal, which is distinguished from other transition metal dichalcogenides (TMDs) from a topological prospective. Here, we study the structure of WTe2 under pressure with a crystal structure prediction and ab initio calculations combined with high pressure synchrotron X-ray diffraction and Raman spectroscopy measurements. We find that the ambient orthorhombic structure (Td) transforms into a monoclinic structure (1T') at around 4-5 GPa. As the transition pressure is very close to the critical point in recent high-pressure electrical transport measurements, the emergence of superconductivity in WTe2 under pressure is attributed to the Td-1T' structure phase transition, which associates with a sliding mechanism of the TMD layers and results in a shorter Te-Te interlayer distance compared to the intralayer ones. These results highlight the critical role of the interlayer stacking and chalcogen interactions on the electronic and superconducting properties of multilayered TMDs under hydrostatic strain environments.

Study of dynamic underwater implosion mechanics using digital image correlation

The physical processes associated with the implosion of cylindrical tubes in a hydrostatic underwater environment were investigated using high-speed three-dimensional digital image correlation (3D DIC). This study emphasizes visualization and understanding of the real-time deformation of the implodable volume and the associated fluid–structure interaction phenomena. Aluminium 6061-T6 cylindrical tubes were used as the implodable volumes. Dynamic tourmaline pressure transducers were placed at selected locations to capture the pressure history generated during each implosion event. A series of small-scale calibration experiments were first performed to establish the applicability of 3D DIC for measuring the deformation of submerged objects. The results of these experiments indicated that the effects of refraction due to water and the optical windows can be accounted for by evaluation of the camera's intrinsic and extrinsic parameters using a submerged calibration grid when the surface normal of the optical windows is collinear with the camera's optical axis. Each pressure history was synchronized with its respective high-speed DIC measurements. DIC results showed that the highest rate of increase in contact area correlates to the largest pressure spike during the implosion process. The results also indicated that, for a given diameter, longer implodable volumes generated higher pressure spikes.

Pressure phase diagram and quantum criticality of CePt2In7single crystals

We report the temperature-pressure (T-P) phase diagram of CePt2In7 single crystals, especially the pressure evolution of the antiferromagnetic order and the emergence of superconductivity, which have been studied by electrical resistivity and ac calorimetry under nearly hydrostatic environments. Compared with its polycrystalline counterpart, bulk superconductivity coexists with antiferromagnetism in a much narrower pressure region. The possible existence of textured superconductivity and local quantum criticality also are observed in CePt2In7, exhibiting a remarkable similarity with CeRhIn5.