The recently developed SCCDS composite tube,a novel variant of the pipe-in-pipe(PIP)structure,demonstrates strong potential for subsea pipeline applications.However,theoretical research regarding its structural behavi...The recently developed SCCDS composite tube,a novel variant of the pipe-in-pipe(PIP)structure,demonstrates strong potential for subsea pipeline applications.However,theoretical research regarding its structural behavior under compression-torsion loading and bearing capacity calculations remains limited,particularly concerning the influence of dual hydraulic pressures during operation.This study examines the impact of dual hydraulic pressures on the compressive-torsional behavior of SCCDS composite tubes.A finite element(FE)model was developed and validated against experimental results,comparing failure modes,full-range loading curves,and bearing capacity to elucidate the working mechanism under dual pressures.A parametric study was then conducted to examine the effects of geometric-physical parameters.Results demonstrate that dual pressures substantially enhance the bearing capacity of sandwich concrete by increasing the normal contact stress at the interface.Increasing concrete strength(f_(c))provides minimal enhancement to torsional resistance compared to the yielding strengths of outer tube(f_(yo))and inner tube(f_(yi)).Higher diameter-to-thickness ratios of outer tube(D_(o)/t_(o))and inner tube(D_(i)/t_(i))significantly reduce torsional capacity.At 1000 m water depth,increasing the D_(o)/t_(o)ratio from 27.5 to 36.67,55,and 110 reduces bearing capacity by 11.17%,23.08%,and 36.14%respectively.Strict measures should be implemented to prevent substantial reductions in strength and ductility for SCCDS composite tubes with large hollow ratios(e.g.,χ=0.849)or high axial compression ratios(e.g.,n=0.8).The study proposes a modified calculation method for determining N-T curves that incorporates dual hydraulic pressure effects,providing guidance for performance evaluation of novel SCCDS composite tubes in deep-sea engineering.展开更多
The emergence of high-temperature superconductivity in hydrogen-rich compounds has opened up promising avenues for investigating unique hydrogen motifs that exhibit exceptional superconducting properties.Nevertheless,...The emergence of high-temperature superconductivity in hydrogen-rich compounds has opened up promising avenues for investigating unique hydrogen motifs that exhibit exceptional superconducting properties.Nevertheless,the requirement for extremely high synthesis pressures poses significant barriers to experimentally probing potential physical properties.Here,we have designed a structure wherein NH_(3)tetrahedra are intercalated into the body-centered cubic lattice of Yb,resulting in the formation of Yb(NH_(3))_(4).Our first-principles calculations reveal that metallic behavior emerges from the ionization of sp^(3)-hybridized s-bonds in NH_(3),which is enabled by electron transfer from ytterbium orbitals to NH_(3)anti-bonding s-orbitals.A distinctive feature of this structure is the Fermi surface nesting,which leads to optical phonon softening and consequently enhances electron-phonon coupling.The subsequent density-functional theory(DFT)calculations demonstrate that this I-43m phase of Yb(NH_(3))4 exhibits a superconducting critical temperature(T_(c))of 17.32 K under a modest pressure of 10 GPa.Our investigation presents perspectives on achieving phonon-mediated superconductivity at relatively low pressures,thereby opening up extensive possibilities for the attainment of high-temperature superconductivity in hydrogen-based superconducting systems with specific ionized molecular groups.展开更多
The safety of the initial support during the construction of inclined shafts in tunnels traversing through high-hydraulic-pressure surrounding rocks is paramount.This study examines a high-hydraulic-pressure inclined ...The safety of the initial support during the construction of inclined shafts in tunnels traversing through high-hydraulic-pressure surrounding rocks is paramount.This study examines a high-hydraulic-pressure inclined shaft of a tunnel in Western Sichuan Province to analyze the damage characteristics of the initial support and propose a radial drainage and decompression treatment method.Field monitoring was conducted to assess the load and deformation of the initial support structure,and on-site investigations identified the distribution of cracked areas.In addition,numerical simulations were performed to evaluate the force and deformation characteristics of the initial support structure,which were then compared with field observations for validation.The variations in the lateral pressure coefficient and water pressure were evaluated.The results revealed that damage was primarily concentrated in the shoulder,spring line,and knee areas,with the bending moment at the knee increasing by up to 66.9%.The application of the radial drainage and decompression treatment method effectively reduced water pressure loads on the initial support.Post-treatment analysis indicated significant reductions in axial force and bending moment,enhancing structural stability.These findings provide valuable insights for improving the safety and durability of initial support systems in inclined shafts of high-hydraulicpressure railroad tunnels.展开更多
Spin-orbit coupling(SOC)plays a vital role in determining the ground state and forming novel electronic states of matter where heavy elements are involved.Here,the prototypical perovskite iridate oxide SrIrO_(3)is inv...Spin-orbit coupling(SOC)plays a vital role in determining the ground state and forming novel electronic states of matter where heavy elements are involved.Here,the prototypical perovskite iridate oxide SrIrO_(3)is investigated to gain more insights into the SOC effect in the modification of electronic structure and corresponding magnetic and electrical properties.The high pressure metastable orthorhombic SrIrO_(3)is successfully stabilized by physical and chemical pressures,in which the chemical pressure is induced by Ru doping in Ir site and Mg substitution of Sr position.Detailed structural,magnetic,electrical characterizations and density functional theory(DFT)calculations reveal that the substitution of Ru for Ir renders an enhanced metallic characteristic,while the introduction of Mg into Sr site results in an insulating state with 10.1%negative magnetoresistance at 10 K under 7 T.Theoretical calculations indicate that Ru doping can weaken the SOC effect,leading to the decrease of orbital energy difference between J_(1/2)and J_(3/2),which is favorable for electron transport.On the contrary,Mg doping can enhance the SOC effect,inducing a metal-insulator-transition(MIT).The electronic phase transition is further revealed by DFT calculations,confirming that the strong SOC and electron-electron interactions can lead to the emergence of insulating state.These findings underline the intricate correlations between lattice degrees of freedom and SOC in determining the ground state,which effectively stimulate the physical pressure between like structures by chemical compression.展开更多
The Design and manufacturing of a noble piezoresistive pressure sensor(PS) for subtle pressures(<1 kPa) were presented. Meanwhile, in the studies conducted in the field of pressure sensors, the measurement of subtl...The Design and manufacturing of a noble piezoresistive pressure sensor(PS) for subtle pressures(<1 kPa) were presented. Meanwhile, in the studies conducted in the field of pressure sensors, the measurement of subtle pressures has received less attention. The limitations in the inherent gauge factor in silicon, have led to the development of polymer and composite resistive sensitive elements. However,in the development of resistance sensing elements, the structure of composite elements with reinforcement core has not been used. The proposed PS had a composite sandwich structure consisting of a nanocomposite graphene layer covered by layers of PDMS at the bottom and on the top coupled with a polyimide(PI) core. Various tests were performed to analyze the PS. The primary design target was improved sensitivity, with a finite-element method(FEM) utilized to simulate the stress profile over piezoresistive elements and membrane deflection at various pressures. The PS manufacturing process is based on Laser-engraved graphene(LEG) technology and PDMS casting. Experimental data indicated that the manufactured PS exhibits a sensitivity of 67.28 mV/kPa for a pressure range of 30-300 Pa in ambient temperature.展开更多
Aviation kerosene RP-3 is extensively used in China.This paper details the measurement of the density of Chinese aviation kerosene RP-3 employing the flow method under high-pressure and high-temperature conditions.The...Aviation kerosene RP-3 is extensively used in China.This paper details the measurement of the density of Chinese aviation kerosene RP-3 employing the flow method under high-pressure and high-temperature conditions.The methodology utilizes circular tubes with two different diameters.The density of aviation kerosene RP-3 was experimentally measured for the first time within a pressure range from 6 MPa to 8 MPa and a temperature range from 323 K to 783 K,with a maximum relative uncertainty of 0.35%.The experimental setup used n-decane for calibration,achieving an average calibration error of 0.91%.The data indicate that the density of RP-3 ranges from 764 kg/m^(3)to 247 kg/m^(3)under the tested conditions.The results show that the density of kerosene RP-3 decreases with an increase in temperature at a constant pressure,and at a given temperature,a higher pressure results in a higher density.Polynomial fitting was applied to the data,resulting in the average absolute deviation of 1.09%,0.80%,and 0.76%at different pressures of 6,7,and 8 MPa,respectively.展开更多
In this paper,we study the properties of the scaled packing topological pressures for a topological dynamical system(X,G),where G is a countable discrete infinite amenable group.We show that the scaled packing topolog...In this paper,we study the properties of the scaled packing topological pressures for a topological dynamical system(X,G),where G is a countable discrete infinite amenable group.We show that the scaled packing topological pressures can be determined by the scaled Bowen topological pressures.We obtain Billingsley’s Theorem for the scaled packing pressures with a G-action.Then we get a variational principle between the scaled packing pressures and the scaled measure-theoretic upper local pressures.Finally,we give some restrictions on the scaled sequence b,then in the case of the set Xμof generic points,we prove thatP^(P)(X_(μ),{F_(n)},f,b)=h_(μ)(X)+∫_(X)∫dμ,if(F(n))is tempered andμis a G-invariant ergodic Borel probability measure.展开更多
This paper experimentally investigates the wave pressure and pore pressure within a sandy seabed around two pipelines under the action of random waves(currents).The experiments revealed that when the random wave plus ...This paper experimentally investigates the wave pressure and pore pressure within a sandy seabed around two pipelines under the action of random waves(currents).The experiments revealed that when the random wave plus current cases are compared with the random wave-only case,the forward current promotes wave propagation,whereas the reversed backward current inhibits wave propagation.Furthermore,the wave pressure on the downstream pipeline decreases as the relative spacing ratio increases and increases as the diameter increases.However,alterations in the relative spacing ratio or dimensions of the downstream pipeline exert a negligible influence on the wave pressure of the upstream pipeline.Moreover,the relative spacing ratio between the pipelines and the dimensions of the pipelines considerably influence the pore pressure in the sand bed.When the relative spacing ratio remains constant,increasing the downstream pipeline diameter will increase the pore-water pressure of the soil below the downstream pipeline.展开更多
Background:Within the tumor microenvironment,survival pressures are prevalent with potent drivers of tumor progression,angiogenesis,and therapeutic resistance.N6-methyladenosine(m6 A)methylation has been recognized as...Background:Within the tumor microenvironment,survival pressures are prevalent with potent drivers of tumor progression,angiogenesis,and therapeutic resistance.N6-methyladenosine(m6 A)methylation has been recognized as a critical post-transcriptional mechanism regulating various aspects of mRNA metabolism.Understanding the intricate interplay between survival pressures and m6 A modification pro-vides new insights into the molecular mechanisms underlying hepatocellular carcinoma(HCC)progres-sion and highlights the potential for targeting the survival pressures-m6 A axis in HCC diagnosis and treat-ment.Data sources:A literature search was conducted in PubMed,MEDLINE,and Web of Science for relevant articles published up to April 2024.The keywords used for the search included hepatocellular carcinoma,cellular survival,survival pressure,N6-methyladenosine,tumor microenvironment,stress response,and hypoxia.Results:This review delves into the multifaceted roles of survival pressures and m6 A RNA methylation in HCC,highlighting how survival pressures modulate the m6 A landscape,the impact of m6 A modifica-tion on survival pressure-responsive gene expression,and the consequent effects on HCC cell survival,proliferation,metastasis,and resistance to treatment.Furthermore,we explored the therapeutic potential of targeting this crosstalk,proposing strategies that leverage the understanding of survival pressures and m6 A RNA methylation mechanisms to develop novel,and more effective treatments for HCC.Conclusions:The interplay between survival pressures and m6 A RNA methylation emerges as a complex regulatory network that influences HCC pathogenesis and progression.展开更多
An equation of state(EOS)was obtained that accurately describes the thermodynamics of the system H_(2)O–CO_(2) at temperatures of 50–350°C and pressures of 0.2–3.5 kbar.The equation is based on experimental da...An equation of state(EOS)was obtained that accurately describes the thermodynamics of the system H_(2)O–CO_(2) at temperatures of 50–350°C and pressures of 0.2–3.5 kbar.The equation is based on experimental data on the compositions of the coexisting liquid and gas phases and the Van Laar model,within which the values of the Van Laar parameters A12 and A21 were found for each experimental P-T point.For the resulting sets A12(P,T),A21(P,T),approximation formulas describing the dependences of these quantities on temperature and pressure were found and the parameters contained in the formulas were fitted.This two-stage approach made it possible to obtain an adequate thermodynamic description of the system,which allows,in addition to determining the phase state of the system(homogeneous or heterogeneous),to calculate the excess free energy of mixing of H_(2)O and CO_(2),the activities of H_(2)O and CO_(2),and other thermodynamic characteristics of the system.The possibility of such calculations creates the basis for using the obtained EOS in thermodynamic models of more complicated fluid systems in P-T conditions of the middle and upper crust.These fluids play an important role in many geological processes including the transport of ore matter and forming hydrothermal ore deposits,in particular,the most of the world’s gold deposits.The knowledge of thermodynamics of these fluids is important in the technology of drilling oil and gas wells.In particular,this concerns the prevention of precipitation of solid salts in the well.展开更多
In order to obtain related brain electrical components and neural bases of physiology assessment of icon elements in a digital human-computer interface the modified sample-delay matching task experimental paradigm is ...In order to obtain related brain electrical components and neural bases of physiology assessment of icon elements in a digital human-computer interface the modified sample-delay matching task experimental paradigm is used under different time pressures 4 000 and 2 000 ms and different icon quantities three five and ten icons on icon memory based on event-related potential ERP technology.Experimental results demonstrate that P300 has significant volatility changes and the maximum amplitude around the middle line of the parietal area PZ and P200 has obvious volatility changes around the middle line of the frontal and central area FCZ during icon cognition.P300 and P200 amplitudes increase as tasks become more difficult.Thus P300 latency is positively correlated with task difficulty. ERP research on the characteristics of icon memory will be an important reference standard in guiding user neurocognitive behavior and physiology assessment on interface usability.展开更多
The corrosion behaviors of X65 steel in the artificial seawater at different hydrostatic pressures are investigated by potentiodynamic polarization measurements, electrochemical impedance spectroscopy measurements and...The corrosion behaviors of X65 steel in the artificial seawater at different hydrostatic pressures are investigated by potentiodynamic polarization measurements, electrochemical impedance spectroscopy measurements and weight loss measurements.The corroded morphologies and the corrosion products are also investigated by scanning electron microscopy, X-ray diffraction analysis and Raman analysis.The results show that the corrosion current increases as the hydrostatic pressure increases.The charge transfer resistance decreases as the hydrostatic pressure increases.The corrosion products are mainly composed of γ-FeOOH and Fe3O4 at the atmospheric pressure, while the main components are γ-FeOOH, Fe3O4, and γ-Fe2O3 at the high pressure.The hydrostatic pressure accelerates the corrosion of X65 steel due to its effect on the chemical and physical properties of corrosion products, including the promoted reduction of γ-FeOOH and the wider and deeper cracks on the corrosion products layer.展开更多
In recent years, there has been an increase of interest in the flow of gases at relatively high pressures and high temperatures. Hydrodynamic calculation of the energy losses in the flow of gases in conduits, as well ...In recent years, there has been an increase of interest in the flow of gases at relatively high pressures and high temperatures. Hydrodynamic calculation of the energy losses in the flow of gases in conduits, as well as through the porous media constituting natural petroleum reservoirs, requires knowledge of the viscosity of the fluid at the pressure and temperature involved. Although there are numerous publications concerning the viscosity of methane at atmospheric pressure, there appears to be little information available relating to the effect of pressure and temperature upon the viscosity. A survey of the literature reveals that the disagreements between published data on the viscosity of methane are common and that most investigations have been conducted over restricted temperature and pressure ranges. Experimental viscosity data for methane are presented for temperatures from 320 to 400 K and pressures from 3000 to 140000 kPa by using falling body viscometer. A summary is given to evaluate the available data for methane, and a comparison is presented for that data common to the experimental range reported in this paper. A new and reliable correlation for methane gas viscosity is presented. Predicted values are given for temperatures up to 400 K and pressures up to 140000 kPa with Average Absolute Percent Relative Error （EABS） of 0.794.展开更多
A critical first step in establishing biosphere reserves--under the Man and Biosphere Programme of UNESCO--is to generate baseline information for future courses of action. The present study aims to assess the structu...A critical first step in establishing biosphere reserves--under the Man and Biosphere Programme of UNESCO--is to generate baseline information for future courses of action. The present study aims to assess the structure and composition of forests--along with anthro- pogenic pressures mounting on these forests in the buffer zone of one such biosphere reserves--the Pachmarhi bio- sphere reserve of India. The quadrat method was employed for sampling vegetation, and information on anthropogenic pressures was collected by conducting interviews with local people and forest officials and collecting it from secondary sources. A total of 39 tree species were sampled in 82 quadrats; of these 26 tree species were in standing stage, 25 in sapling, and 35 in seedling. Chloroxylon swi- etenia emerged as the most dominant tree species having highest importance value index, followed by Tectona grandis, Terminalia tomentosa, and Hardwickia binata. Nine tree species and their saplings, including Sterculia urens and Terminalia arjuna, were exploited so badly that they were only found in the seedlings stage. The unavail- ability of standing trees of 12 important tree species including Aegle marmelos and Phyllanthus emblicaindicates the intensity and gravity of anthropogenic pres- sures on these important tree species. If the present anthropogenic pressure continues, which has inhibited the regeneration of several tree species, then substantial neg- ative ecological and societal consequences can be expected.展开更多
The laser induced plasma dynamics of graphite material are investigated by optical emission spectroscopy. Abla- tion and excitation of the graphite material is performed by using an 1064nm Nd：YAG laser in different a...The laser induced plasma dynamics of graphite material are investigated by optical emission spectroscopy. Abla- tion and excitation of the graphite material is performed by using an 1064nm Nd：YAG laser in different ambient pressures. Characteristics of graphite spectra as line intensity variations and signal-to-noise ratio are presented with a main focus on the influence of the ambient pressure on the interaction of laser-induced graphite plasma with an ambient environment. Atomic emission lines are utilized to investigate the dynamical behavior of plasma, such as the excitation temperature and electron density, to describe emission differences under different ambient conditions. The excitation temperature and plasma electron density are the primary factors which contribute to the differences among the atomic carbon emission at different ambient pressures. Reactions between the plasma species and ambient gas, and the total molecular number are the main factors influencing molecular carbon emis- sion. The influence of laser energy on the plasma interaction with environment is also investigated to demonstrate the dynamical behavior of carbon species so that it can be utilized to optimize plasma fluctuations.展开更多
Because ring-stiffened cylindrical shell structures have many merits, they are widely used in many areas. However, as the strength of steel increase continuously, ensuring of the structure stability is becoming more a...Because ring-stiffened cylindrical shell structures have many merits, they are widely used in many areas. However, as the strength of steel increase continuously, ensuring of the structure stability is becoming more and more important. Therefore, it is necessary to carry on a more particular analysis. Based on the understanding and analysis of the characteristics of stability for a ring-stiffened cylindrical shell under uniform external pressure and under external single pressure, the characteristics under different cross uniform external pressures are analyzed, and the regularity of it is also gotten. The curve of stability given various geometrical parameters under different cross uniform external pressures is protracted by the analysis of the theory. The conclusion not only improves the theory structural mechanics, it also was important effects on engineering calculation and design.展开更多
BACKGROUND Hemodialysis machine-generated circuit pressures and clearance profiles are potential predictors of quality assurances. In our practice, we previously we observed that elevated static access pressures were ...BACKGROUND Hemodialysis machine-generated circuit pressures and clearance profiles are potential predictors of quality assurances. In our practice, we previously we observed that elevated static access pressures were associated with abnormal Kt/V values, high access recirculation and deviation of the Kt/V profile (Abnormal Kt/V profile) from normally expected values (Normal Kt/V profile). AIM To hypothesize that static or derived access pressures would correlate with direct intra-access blood flow rates and that clearance (Kt/V) profiles would correlate with measured Kt/V values. METHODS Static access pressures, real-time adequacy of dialysis and intra-access blood flow were investigated in end stage renal disease patients undergoing hemodialysis. Wilcoxon-Mann-Whitney test, chi-square test or Fisher’s exact test was used to investigate differences between the groups;Spearman’s rank correlation test to investigate relationships between static pressures, direct intra-access pressures and Kt/V profiles;and multinomial logistic regression models to identify the independent effect of selected variables on Kt/V profiles. Odds ratio were calculated to measure the association between the variables and Kt/V profiles. RESULTS One hundred and seven patients were included for analysis. There were no significant differences between genders, and types of vascular access between the normal vs. abnormal clearance (Kt/V) profile groups. No significant correlation could be demonstrated between static access pressures and Kt/V profiles, static access pressures and intra-access blood flow, intra-access blood flow and Kt/V profiles, measured Kt/V and Kt/V profiles or recirculation and Kt/V profiles. CONCLUSION In this study utilizing measured versus estimated data, we could not validate that dialysis machine generated elevated static pressures predict intra-access blood flow disturbances or that abnormal Kt/V profiles predict access recirculation or inadequate dialysis. These parameters, though useful estimates, cannot be accepted as quality assurance for dialysis adequacy or access function without further evidences.展开更多
Objective:To analyze the efficacy of hyperbaric oxygen at different pressures in the treatment of sudden deafness.Methods:Eighty-two patients with sudden deafness treated in the Affiliated Hospital of Hebei University...Objective:To analyze the efficacy of hyperbaric oxygen at different pressures in the treatment of sudden deafness.Methods:Eighty-two patients with sudden deafness treated in the Affiliated Hospital of Hebei University from September 2019 to September 2021 were selected as the research subjects.The patients were randomly divided into study group 1 and study group 2,and they were treated with hyperbaric oxygen on the basis of routine treatment,in which the pressure used was 1.8 ATA and 2.2 ATA,respectively.Oxygen was delivered via the pressure stabilizing mask for 60 minutes.The patients received two courses of treatment,each lasting 10 days.The changes in hearing(pure tone audiometry)and the clinical efficacy of both the groups were compared before and after treatment.The data obtained were statistically analyzed using SPSS 19.0.Results:The total effective rate of study group 1 was 90.00%,while that of study group 2 was 76.19%.The differences between the two groups were statistically significant(p<0.05).Conclusion:For patients with sudden deafness treated with hyperbaric oxygen,the clinical efficacy of 1.8 ATA is more significant than that of 2.2 ATA.展开更多
The title problem is systematically analyzed by the differential quadrature (DQ) method. Estimates of the critical buckling loads are obtained for combinations of various boundary conditions, internal and/or external ...The title problem is systematically analyzed by the differential quadrature (DQ) method. Estimates of the critical buckling loads are obtained for combinations of various boundary conditions, internal and/or external Pressures, hole sizes,and rigidity ratios. A comparison is made with existing results for certain cases. Numerical investigation has been carried out with regard to the convergence of the solutions. It is found that accurate results are obtained with only nine or eleven grid points.展开更多
The striation plasmas are usually generated within a positive column of glow discharge,where rich and complex physical interactions are involved,especially,in the medium or high pressures.Along these lines,our work ai...The striation plasmas are usually generated within a positive column of glow discharge,where rich and complex physical interactions are involved,especially,in the medium or high pressures.Along these lines,our work aims to thoroughly investigate the formation and destruction of helium striation plasmas at kPa level pressures.The characteristics of the helium striation plasmas,and especially the optical emission properties are explored.The emission lines of 706.52 nm and391.44 nm related to the energetic electrons and the high-energy metastable helium atoms respectively,were focused on in this work.The formation of striation plasmas in a helium glow discharge,is mainly associated with the instability originating from the stepwise ionization of high-energy metastable state atoms,Maxwellization of the electron distribution functions and gas heating.Additionally,the destruction effect of helium striation plasmas is of great significance when a small amount of nitrogen or oxygen is mixed into the discharge plasmas.The reduction of the mean electron energy and the consumption of the high-energy metastable helium atoms are considered as the underlying reasons for the destruction of striation plasmas.展开更多
基金supported by the High-level Talent Research Startup Fund(Grant No.1608722024)of Xi’an University of Archit-ectureTechnology and the Shaanxi Province High-level Youth Talents Program(Grant No.Z20240589).
文摘The recently developed SCCDS composite tube,a novel variant of the pipe-in-pipe(PIP)structure,demonstrates strong potential for subsea pipeline applications.However,theoretical research regarding its structural behavior under compression-torsion loading and bearing capacity calculations remains limited,particularly concerning the influence of dual hydraulic pressures during operation.This study examines the impact of dual hydraulic pressures on the compressive-torsional behavior of SCCDS composite tubes.A finite element(FE)model was developed and validated against experimental results,comparing failure modes,full-range loading curves,and bearing capacity to elucidate the working mechanism under dual pressures.A parametric study was then conducted to examine the effects of geometric-physical parameters.Results demonstrate that dual pressures substantially enhance the bearing capacity of sandwich concrete by increasing the normal contact stress at the interface.Increasing concrete strength(f_(c))provides minimal enhancement to torsional resistance compared to the yielding strengths of outer tube(f_(yo))and inner tube(f_(yi)).Higher diameter-to-thickness ratios of outer tube(D_(o)/t_(o))and inner tube(D_(i)/t_(i))significantly reduce torsional capacity.At 1000 m water depth,increasing the D_(o)/t_(o)ratio from 27.5 to 36.67,55,and 110 reduces bearing capacity by 11.17%,23.08%,and 36.14%respectively.Strict measures should be implemented to prevent substantial reductions in strength and ductility for SCCDS composite tubes with large hollow ratios(e.g.,χ=0.849)or high axial compression ratios(e.g.,n=0.8).The study proposes a modified calculation method for determining N-T curves that incorporates dual hydraulic pressure effects,providing guidance for performance evaluation of novel SCCDS composite tubes in deep-sea engineering.
基金work was supported by the National Key Research and Development Program of China(Grant Nos.2023YFA1406200 and 2022YFA1405500)the National Natural Science Foundation of China(Grant Nos.12304021 and 52072188)+4 种基金Zhejiang Provincial Natural Science Foundation of China(Grant No.LQ23A040004)Program for Science and Technology Innovation Team in Zhejiang(Grant No.2021R01004)the Natural Science Foundation of Ningbo(Grant No.2022J091)the Program for Changjiang Scholars and Innovative Research Team in University(Grant No.IRT 15R23)Parts of calculations were performed at the Supercomputer Center of Ningbo University.
文摘The emergence of high-temperature superconductivity in hydrogen-rich compounds has opened up promising avenues for investigating unique hydrogen motifs that exhibit exceptional superconducting properties.Nevertheless,the requirement for extremely high synthesis pressures poses significant barriers to experimentally probing potential physical properties.Here,we have designed a structure wherein NH_(3)tetrahedra are intercalated into the body-centered cubic lattice of Yb,resulting in the formation of Yb(NH_(3))_(4).Our first-principles calculations reveal that metallic behavior emerges from the ionization of sp^(3)-hybridized s-bonds in NH_(3),which is enabled by electron transfer from ytterbium orbitals to NH_(3)anti-bonding s-orbitals.A distinctive feature of this structure is the Fermi surface nesting,which leads to optical phonon softening and consequently enhances electron-phonon coupling.The subsequent density-functional theory(DFT)calculations demonstrate that this I-43m phase of Yb(NH_(3))4 exhibits a superconducting critical temperature(T_(c))of 17.32 K under a modest pressure of 10 GPa.Our investigation presents perspectives on achieving phonon-mediated superconductivity at relatively low pressures,thereby opening up extensive possibilities for the attainment of high-temperature superconductivity in hydrogen-based superconducting systems with specific ionized molecular groups.
基金supported by the National Natural Science Foundation of China(Grant Nos.42277165,41920104007)the Hubei Natural Science Foundation(Grant No.2023AFD217).
文摘The safety of the initial support during the construction of inclined shafts in tunnels traversing through high-hydraulic-pressure surrounding rocks is paramount.This study examines a high-hydraulic-pressure inclined shaft of a tunnel in Western Sichuan Province to analyze the damage characteristics of the initial support and propose a radial drainage and decompression treatment method.Field monitoring was conducted to assess the load and deformation of the initial support structure,and on-site investigations identified the distribution of cracked areas.In addition,numerical simulations were performed to evaluate the force and deformation characteristics of the initial support structure,which were then compared with field observations for validation.The variations in the lateral pressure coefficient and water pressure were evaluated.The results revealed that damage was primarily concentrated in the shoulder,spring line,and knee areas,with the bending moment at the knee increasing by up to 66.9%.The application of the radial drainage and decompression treatment method effectively reduced water pressure loads on the initial support.Post-treatment analysis indicated significant reductions in axial force and bending moment,enhancing structural stability.These findings provide valuable insights for improving the safety and durability of initial support systems in inclined shafts of high-hydraulicpressure railroad tunnels.
基金supported by the National Natural Science Foundation of China(NSFC,No.22090041)the Guangdong Basic and Applied Basic Research Foundation(No.2022B1515120014)。
文摘Spin-orbit coupling(SOC)plays a vital role in determining the ground state and forming novel electronic states of matter where heavy elements are involved.Here,the prototypical perovskite iridate oxide SrIrO_(3)is investigated to gain more insights into the SOC effect in the modification of electronic structure and corresponding magnetic and electrical properties.The high pressure metastable orthorhombic SrIrO_(3)is successfully stabilized by physical and chemical pressures,in which the chemical pressure is induced by Ru doping in Ir site and Mg substitution of Sr position.Detailed structural,magnetic,electrical characterizations and density functional theory(DFT)calculations reveal that the substitution of Ru for Ir renders an enhanced metallic characteristic,while the introduction of Mg into Sr site results in an insulating state with 10.1%negative magnetoresistance at 10 K under 7 T.Theoretical calculations indicate that Ru doping can weaken the SOC effect,leading to the decrease of orbital energy difference between J_(1/2)and J_(3/2),which is favorable for electron transport.On the contrary,Mg doping can enhance the SOC effect,inducing a metal-insulator-transition(MIT).The electronic phase transition is further revealed by DFT calculations,confirming that the strong SOC and electron-electron interactions can lead to the emergence of insulating state.These findings underline the intricate correlations between lattice degrees of freedom and SOC in determining the ground state,which effectively stimulate the physical pressure between like structures by chemical compression.
文摘The Design and manufacturing of a noble piezoresistive pressure sensor(PS) for subtle pressures(<1 kPa) were presented. Meanwhile, in the studies conducted in the field of pressure sensors, the measurement of subtle pressures has received less attention. The limitations in the inherent gauge factor in silicon, have led to the development of polymer and composite resistive sensitive elements. However,in the development of resistance sensing elements, the structure of composite elements with reinforcement core has not been used. The proposed PS had a composite sandwich structure consisting of a nanocomposite graphene layer covered by layers of PDMS at the bottom and on the top coupled with a polyimide(PI) core. Various tests were performed to analyze the PS. The primary design target was improved sensitivity, with a finite-element method(FEM) utilized to simulate the stress profile over piezoresistive elements and membrane deflection at various pressures. The PS manufacturing process is based on Laser-engraved graphene(LEG) technology and PDMS casting. Experimental data indicated that the manufactured PS exhibits a sensitivity of 67.28 mV/kPa for a pressure range of 30-300 Pa in ambient temperature.
基金supported by the Science Center for Gas Turbine Project,China(No.P2022-C-II-005-001)。
文摘Aviation kerosene RP-3 is extensively used in China.This paper details the measurement of the density of Chinese aviation kerosene RP-3 employing the flow method under high-pressure and high-temperature conditions.The methodology utilizes circular tubes with two different diameters.The density of aviation kerosene RP-3 was experimentally measured for the first time within a pressure range from 6 MPa to 8 MPa and a temperature range from 323 K to 783 K,with a maximum relative uncertainty of 0.35%.The experimental setup used n-decane for calibration,achieving an average calibration error of 0.91%.The data indicate that the density of RP-3 ranges from 764 kg/m^(3)to 247 kg/m^(3)under the tested conditions.The results show that the density of kerosene RP-3 decreases with an increase in temperature at a constant pressure,and at a given temperature,a higher pressure results in a higher density.Polynomial fitting was applied to the data,resulting in the average absolute deviation of 1.09%,0.80%,and 0.76%at different pressures of 6,7,and 8 MPa,respectively.
基金supported by the NNSF of China(12201120)the visiting fellowships supported by Fujian Alliance of Mathematics while visiting Xiamen University in the winter of 2023。
文摘In this paper,we study the properties of the scaled packing topological pressures for a topological dynamical system(X,G),where G is a countable discrete infinite amenable group.We show that the scaled packing topological pressures can be determined by the scaled Bowen topological pressures.We obtain Billingsley’s Theorem for the scaled packing pressures with a G-action.Then we get a variational principle between the scaled packing pressures and the scaled measure-theoretic upper local pressures.Finally,we give some restrictions on the scaled sequence b,then in the case of the set Xμof generic points,we prove thatP^(P)(X_(μ),{F_(n)},f,b)=h_(μ)(X)+∫_(X)∫dμ,if(F(n))is tempered andμis a G-invariant ergodic Borel probability measure.
基金supported by the National Natural Science Foundation of China(Grant No.52271281)Shandong Provincial High-Level Talent Workstation,Shandong Province Natural Science Foundation Youth project(Grant No.ZR2023QE190)an Open funding project from the Key Laboratory of Ministry of Education for Coastal Disaster and Protection,Hohai University,China(Grant No.202206).
文摘This paper experimentally investigates the wave pressure and pore pressure within a sandy seabed around two pipelines under the action of random waves(currents).The experiments revealed that when the random wave plus current cases are compared with the random wave-only case,the forward current promotes wave propagation,whereas the reversed backward current inhibits wave propagation.Furthermore,the wave pressure on the downstream pipeline decreases as the relative spacing ratio increases and increases as the diameter increases.However,alterations in the relative spacing ratio or dimensions of the downstream pipeline exert a negligible influence on the wave pressure of the upstream pipeline.Moreover,the relative spacing ratio between the pipelines and the dimensions of the pipelines considerably influence the pore pressure in the sand bed.When the relative spacing ratio remains constant,increasing the downstream pipeline diameter will increase the pore-water pressure of the soil below the downstream pipeline.
基金supported by grants from Research Founda-tion of Guangzhou Women and Children’s Medical Center for Clinical Doctor (1600110)Science and Technology Projects in Guangzhou (202201011371)+1 种基金Guangzhou Municipalcience and Tech-nology Bureau Foundation (2023A03J0917)Guangdong Basic and Applied Basic Research Foundation (2023A1515220076 and 2022A1515110283)。
文摘Background:Within the tumor microenvironment,survival pressures are prevalent with potent drivers of tumor progression,angiogenesis,and therapeutic resistance.N6-methyladenosine(m6 A)methylation has been recognized as a critical post-transcriptional mechanism regulating various aspects of mRNA metabolism.Understanding the intricate interplay between survival pressures and m6 A modification pro-vides new insights into the molecular mechanisms underlying hepatocellular carcinoma(HCC)progres-sion and highlights the potential for targeting the survival pressures-m6 A axis in HCC diagnosis and treat-ment.Data sources:A literature search was conducted in PubMed,MEDLINE,and Web of Science for relevant articles published up to April 2024.The keywords used for the search included hepatocellular carcinoma,cellular survival,survival pressure,N6-methyladenosine,tumor microenvironment,stress response,and hypoxia.Results:This review delves into the multifaceted roles of survival pressures and m6 A RNA methylation in HCC,highlighting how survival pressures modulate the m6 A landscape,the impact of m6 A modifica-tion on survival pressure-responsive gene expression,and the consequent effects on HCC cell survival,proliferation,metastasis,and resistance to treatment.Furthermore,we explored the therapeutic potential of targeting this crosstalk,proposing strategies that leverage the understanding of survival pressures and m6 A RNA methylation mechanisms to develop novel,and more effective treatments for HCC.Conclusions:The interplay between survival pressures and m6 A RNA methylation emerges as a complex regulatory network that influences HCC pathogenesis and progression.
基金funded by the Research program FMUW-2021-0002 of the IPGG RAS.
文摘An equation of state(EOS)was obtained that accurately describes the thermodynamics of the system H_(2)O–CO_(2) at temperatures of 50–350°C and pressures of 0.2–3.5 kbar.The equation is based on experimental data on the compositions of the coexisting liquid and gas phases and the Van Laar model,within which the values of the Van Laar parameters A12 and A21 were found for each experimental P-T point.For the resulting sets A12(P,T),A21(P,T),approximation formulas describing the dependences of these quantities on temperature and pressure were found and the parameters contained in the formulas were fitted.This two-stage approach made it possible to obtain an adequate thermodynamic description of the system,which allows,in addition to determining the phase state of the system(homogeneous or heterogeneous),to calculate the excess free energy of mixing of H_(2)O and CO_(2),the activities of H_(2)O and CO_(2),and other thermodynamic characteristics of the system.The possibility of such calculations creates the basis for using the obtained EOS in thermodynamic models of more complicated fluid systems in P-T conditions of the middle and upper crust.These fluids play an important role in many geological processes including the transport of ore matter and forming hydrothermal ore deposits,in particular,the most of the world’s gold deposits.The knowledge of thermodynamics of these fluids is important in the technology of drilling oil and gas wells.In particular,this concerns the prevention of precipitation of solid salts in the well.
基金The National Natural Science Foundation of China(No.71271053,71071032)the Scientific Innovation Research of College Graduates in Jiangsu Province(No.CXZZ12_0093)
文摘In order to obtain related brain electrical components and neural bases of physiology assessment of icon elements in a digital human-computer interface the modified sample-delay matching task experimental paradigm is used under different time pressures 4 000 and 2 000 ms and different icon quantities three five and ten icons on icon memory based on event-related potential ERP technology.Experimental results demonstrate that P300 has significant volatility changes and the maximum amplitude around the middle line of the parietal area PZ and P200 has obvious volatility changes around the middle line of the frontal and central area FCZ during icon cognition.P300 and P200 amplitudes increase as tasks become more difficult.Thus P300 latency is positively correlated with task difficulty. ERP research on the characteristics of icon memory will be an important reference standard in guiding user neurocognitive behavior and physiology assessment on interface usability.
基金supported by National Basic Research Program of China (2014CB046801)National Natural Science Foundation of China (51471117)Key Project of Tianjin Natural Science Foundation (13JCZDJC29500)
文摘The corrosion behaviors of X65 steel in the artificial seawater at different hydrostatic pressures are investigated by potentiodynamic polarization measurements, electrochemical impedance spectroscopy measurements and weight loss measurements.The corroded morphologies and the corrosion products are also investigated by scanning electron microscopy, X-ray diffraction analysis and Raman analysis.The results show that the corrosion current increases as the hydrostatic pressure increases.The charge transfer resistance decreases as the hydrostatic pressure increases.The corrosion products are mainly composed of γ-FeOOH and Fe3O4 at the atmospheric pressure, while the main components are γ-FeOOH, Fe3O4, and γ-Fe2O3 at the high pressure.The hydrostatic pressure accelerates the corrosion of X65 steel due to its effect on the chemical and physical properties of corrosion products, including the promoted reduction of γ-FeOOH and the wider and deeper cracks on the corrosion products layer.
基金supported by the Research Institute of Petroleum Industry-Kermanshah Campus.
文摘In recent years, there has been an increase of interest in the flow of gases at relatively high pressures and high temperatures. Hydrodynamic calculation of the energy losses in the flow of gases in conduits, as well as through the porous media constituting natural petroleum reservoirs, requires knowledge of the viscosity of the fluid at the pressure and temperature involved. Although there are numerous publications concerning the viscosity of methane at atmospheric pressure, there appears to be little information available relating to the effect of pressure and temperature upon the viscosity. A survey of the literature reveals that the disagreements between published data on the viscosity of methane are common and that most investigations have been conducted over restricted temperature and pressure ranges. Experimental viscosity data for methane are presented for temperatures from 320 to 400 K and pressures from 3000 to 140000 kPa by using falling body viscometer. A summary is given to evaluate the available data for methane, and a comparison is presented for that data common to the experimental range reported in this paper. A new and reliable correlation for methane gas viscosity is presented. Predicted values are given for temperatures up to 400 K and pressures up to 140000 kPa with Average Absolute Percent Relative Error （EABS） of 0.794.
基金funded under the grant IIFM/RP-Int./CPK/2009-11/04
文摘A critical first step in establishing biosphere reserves--under the Man and Biosphere Programme of UNESCO--is to generate baseline information for future courses of action. The present study aims to assess the structure and composition of forests--along with anthro- pogenic pressures mounting on these forests in the buffer zone of one such biosphere reserves--the Pachmarhi bio- sphere reserve of India. The quadrat method was employed for sampling vegetation, and information on anthropogenic pressures was collected by conducting interviews with local people and forest officials and collecting it from secondary sources. A total of 39 tree species were sampled in 82 quadrats; of these 26 tree species were in standing stage, 25 in sapling, and 35 in seedling. Chloroxylon swi- etenia emerged as the most dominant tree species having highest importance value index, followed by Tectona grandis, Terminalia tomentosa, and Hardwickia binata. Nine tree species and their saplings, including Sterculia urens and Terminalia arjuna, were exploited so badly that they were only found in the seedlings stage. The unavail- ability of standing trees of 12 important tree species including Aegle marmelos and Phyllanthus emblicaindicates the intensity and gravity of anthropogenic pres- sures on these important tree species. If the present anthropogenic pressure continues, which has inhibited the regeneration of several tree species, then substantial neg- ative ecological and societal consequences can be expected.
基金Supported by the FRGS under Grant No R.J130000.7809.4F519
文摘The laser induced plasma dynamics of graphite material are investigated by optical emission spectroscopy. Abla- tion and excitation of the graphite material is performed by using an 1064nm Nd：YAG laser in different ambient pressures. Characteristics of graphite spectra as line intensity variations and signal-to-noise ratio are presented with a main focus on the influence of the ambient pressure on the interaction of laser-induced graphite plasma with an ambient environment. Atomic emission lines are utilized to investigate the dynamical behavior of plasma, such as the excitation temperature and electron density, to describe emission differences under different ambient conditions. The excitation temperature and plasma electron density are the primary factors which contribute to the differences among the atomic carbon emission at different ambient pressures. Reactions between the plasma species and ambient gas, and the total molecular number are the main factors influencing molecular carbon emis- sion. The influence of laser energy on the plasma interaction with environment is also investigated to demonstrate the dynamical behavior of carbon species so that it can be utilized to optimize plasma fluctuations.
文摘Because ring-stiffened cylindrical shell structures have many merits, they are widely used in many areas. However, as the strength of steel increase continuously, ensuring of the structure stability is becoming more and more important. Therefore, it is necessary to carry on a more particular analysis. Based on the understanding and analysis of the characteristics of stability for a ring-stiffened cylindrical shell under uniform external pressure and under external single pressure, the characteristics under different cross uniform external pressures are analyzed, and the regularity of it is also gotten. The curve of stability given various geometrical parameters under different cross uniform external pressures is protracted by the analysis of the theory. The conclusion not only improves the theory structural mechanics, it also was important effects on engineering calculation and design.
基金the Gatorade Trust through funds distributed by the University of Florida,Division of Nephrology,Hypertension,and Renal Transplantation,Gainesville,FL [Awarded to Abhilash Koratala(Principal investigator)Abutaleb A Ejaz(Mentor)]
文摘BACKGROUND Hemodialysis machine-generated circuit pressures and clearance profiles are potential predictors of quality assurances. In our practice, we previously we observed that elevated static access pressures were associated with abnormal Kt/V values, high access recirculation and deviation of the Kt/V profile (Abnormal Kt/V profile) from normally expected values (Normal Kt/V profile). AIM To hypothesize that static or derived access pressures would correlate with direct intra-access blood flow rates and that clearance (Kt/V) profiles would correlate with measured Kt/V values. METHODS Static access pressures, real-time adequacy of dialysis and intra-access blood flow were investigated in end stage renal disease patients undergoing hemodialysis. Wilcoxon-Mann-Whitney test, chi-square test or Fisher’s exact test was used to investigate differences between the groups;Spearman’s rank correlation test to investigate relationships between static pressures, direct intra-access pressures and Kt/V profiles;and multinomial logistic regression models to identify the independent effect of selected variables on Kt/V profiles. Odds ratio were calculated to measure the association between the variables and Kt/V profiles. RESULTS One hundred and seven patients were included for analysis. There were no significant differences between genders, and types of vascular access between the normal vs. abnormal clearance (Kt/V) profile groups. No significant correlation could be demonstrated between static access pressures and Kt/V profiles, static access pressures and intra-access blood flow, intra-access blood flow and Kt/V profiles, measured Kt/V and Kt/V profiles or recirculation and Kt/V profiles. CONCLUSION In this study utilizing measured versus estimated data, we could not validate that dialysis machine generated elevated static pressures predict intra-access blood flow disturbances or that abnormal Kt/V profiles predict access recirculation or inadequate dialysis. These parameters, though useful estimates, cannot be accepted as quality assurance for dialysis adequacy or access function without further evidences.
基金The Youth Scientific Research Fund of the Affiliated Hospital of Hebei University“Observation on the Efficacy of Different Pressure Hyperbaric Oxygen in the Treatment of Sudden Deafness”(Grant Number:2021Q040).
文摘Objective:To analyze the efficacy of hyperbaric oxygen at different pressures in the treatment of sudden deafness.Methods:Eighty-two patients with sudden deafness treated in the Affiliated Hospital of Hebei University from September 2019 to September 2021 were selected as the research subjects.The patients were randomly divided into study group 1 and study group 2,and they were treated with hyperbaric oxygen on the basis of routine treatment,in which the pressure used was 1.8 ATA and 2.2 ATA,respectively.Oxygen was delivered via the pressure stabilizing mask for 60 minutes.The patients received two courses of treatment,each lasting 10 days.The changes in hearing(pure tone audiometry)and the clinical efficacy of both the groups were compared before and after treatment.The data obtained were statistically analyzed using SPSS 19.0.Results:The total effective rate of study group 1 was 90.00%,while that of study group 2 was 76.19%.The differences between the two groups were statistically significant(p<0.05).Conclusion:For patients with sudden deafness treated with hyperbaric oxygen,the clinical efficacy of 1.8 ATA is more significant than that of 2.2 ATA.
文摘The title problem is systematically analyzed by the differential quadrature (DQ) method. Estimates of the critical buckling loads are obtained for combinations of various boundary conditions, internal and/or external Pressures, hole sizes,and rigidity ratios. A comparison is made with existing results for certain cases. Numerical investigation has been carried out with regard to the convergence of the solutions. It is found that accurate results are obtained with only nine or eleven grid points.
基金supported by National Natural Science Foundation of China(No.11875039)。
文摘The striation plasmas are usually generated within a positive column of glow discharge,where rich and complex physical interactions are involved,especially,in the medium or high pressures.Along these lines,our work aims to thoroughly investigate the formation and destruction of helium striation plasmas at kPa level pressures.The characteristics of the helium striation plasmas,and especially the optical emission properties are explored.The emission lines of 706.52 nm and391.44 nm related to the energetic electrons and the high-energy metastable helium atoms respectively,were focused on in this work.The formation of striation plasmas in a helium glow discharge,is mainly associated with the instability originating from the stepwise ionization of high-energy metastable state atoms,Maxwellization of the electron distribution functions and gas heating.Additionally,the destruction effect of helium striation plasmas is of great significance when a small amount of nitrogen or oxygen is mixed into the discharge plasmas.The reduction of the mean electron energy and the consumption of the high-energy metastable helium atoms are considered as the underlying reasons for the destruction of striation plasmas.
