THE APPLICATION OF ARTIFICIAL NEURAL NETWORKS TO INVESTIGATION ON THE THICKNESS OF INTERMETALLIC LAYER UNDER SOLID-LIQUID PRESSURE BONDING OF STEEL AND ALUMINIUM

Artificial neural networks (ANN), being a sophisticated type of information processing system by imitating the neural system of human brain, can be used to investigate the effects of concentration of flux solution, temperature of liquid aluminium, temperture of tools and pressure on thickness of the intermetallic layer at the interface between steel and aluminium under solid-liquid pressure bonding of steel and aluminium perfectly. The optimum thickness has been determined according to the value of the optimum shearing strength.

Sealing capacity evaluation of underground gas storage under intricate geological conditions

Evaluating underground gas storage(UGS)sealing capacity is essential for its safe construction and operational efficiency.This involves evaluating both the static sealing capacity of traps during hydrocarbon accumulation and the dynamic sealing capacity of UGS under intensive gas injection and withdrawal,and alternating loads.This study detailed the methodology developed by Sinopec.The approach merges disciplines like geology,geomechanics,and hydrodynamics,employing both dynamic-static and qualitative-quantitative analyses.Sinopec's evaluation methods,grounded in the in situ stress analysis,include mechanistic studies,laboratory tests,geological surveys,stress analysis,and fluid-solid interactions.Through tests on the static and dynamic sealing capacity of UGS,alongside investigations into sealing mechanisms and the geological and geomechanical properties of cap rocks and faults,A geomechanics-rock damage-seepage mechanics dynamic coupling analysis method has been developed to predict in situ stress variations relative to pore pressure changes during UGS operations and evaluate fault sealing capacity and cap rock integrity,thereby setting the maximum operational pressures.Utilizing this evaluation technique,Sinopec has defined performance metrics and criteria for evaluating the sealing capacity of depleted gas reservoirs,enabling preliminary sealing capacity evaluations at UGS sites.These evaluations have significantly informed the design of UGS construction schemes and the evaluation of fault sealing capacity and cap rock integrity during UGS operations.

Thickness-dependent structural stability and transition in molybdenum disulfide under hydrostatic pressure

Understanding the physical mechanism of structural stability and transition in various polytypes of layered transition metal dichalcogenides under the external stimulus is of crucial importance for their new applications.Here,we investigate the thickness-dependent structural properties of MoS2 under the condition of hydrostatic pressure in terms of bond relaxation and thermodynamics considerations.For both types of MoS2 structures,we find that the transition and metallization are significantly modulated by hydrostatic pressure and the number of layers.We establish a pressure-size phase diagram to address the transition mechanism.Our study not only provides insights into the thickness-dependent structural properties of MoS2,but also shows a theoretical guidance for the design and fabrication of MoS2-based devices.

Effect of Ilizarov external fixation combined with negative pressure sealing drainage and antibiotics in the treatment of infective tibial nonunion

Objective:Observation on the effect of Ilizarov external fixation combined with vacuum pressure sealing drainage and antibiotics in the treatment of infective tibial nonunion.Methods:79 patients with tibial infective nonunion who were treated in our hospital from August 2016 to August 2018 were divided into two groups according to random number table,with 39 patients in the control group treated with Ilizarov external fixation technology and 40 patients in the study group treated with vacuum pressure sealing drainage and antibiotics on the basis of the control group.Bone healing time and daily walking were recorded.Rasmussen score,serum intercellular adhesion molecule-1(ICAM-1)and IL-6 levels,lower limb Fugl-Meyer motor function score and lower limb BI index score were compared at different time.Results:The daily walking condition of the study group was significantly better than that of the control group(P<0.05),and the healing time of bone was significantly shorter than that of the control group(P<0.05);the Rasmussen score of the study group was higher than that of the control group at 1 month,6 months and 12 months after treatment(P<0.05);the levels of serum ICAM-1 and IL-6 in the two groups after treatment were lower than those before treatment(P<0.05),and the levels of serum ICAM-1 and IL-6 in the study group were lower than those in the control group after treatment(P<0.05).The lower limb Fugl-Meyer motor function score and lower limb BI index score of the two groups after treatment were higher than those before treatment(P<0.05),and the lower limb Fugl-Meyer motor function score and lower limb BI index score of the study group after treatment were higher than those of the control group(P<0.05).Conclusions:Ilizarov external fixation combined with vacuum pressure sealing drainage and antibiotics can promote the bone healing of patients with infective tibial nonunion,significantly improving their daily walking condition,alleviating inflammation,and recovering the knee joint function and lower limb function well.

Compressive and Sealing Characteristics of PTFE under Cyclic Loading-unloading

Compressive and sealing characteristics of PTFE under cyclic loading-unloading at room temperature are studied in order to evaluate the cyclic sealing performance of control valve comprehensively. The unloading characteristics are different from the loading ones, therefore there is hysteresis between the unloading and loading curves. Compressive hysteresis is the main factor that causes sealing hysteresis. The leakage rate of PTFE complies with the power law before it enters the relatively stable region. Lastly, the effect of working pressure on the compressive and sealing characteristics is discussed. The experimental results show that the working pressure has little effect on compressive deformation but has a great influence on leakage rate.

A Molecular Description of Superconductivity of Sulfur Hydride and Related Systems under High-Pressure Conditions

It has been shown that the recently discovered sulfur trihydride (H3S) can be considered as a superconductor with a transition temperature Tc of 203 Kelvin (K) at 155 GigaPascals (GPa). This is the highest Tc value reported for any superconductor. The established superconductivity occurs via the formation of a molecular system with sulfur atoms arranged on a body-centered cubic lattice. It has been generally accepted that the high Tc value is the result of an efficient electron-phonon interaction. The responsible substance formed by H2S under high pressure, may be considered as a compound with H3S stoichiometry creating an impressive network with hydrogens. We will focus on the hydrogen bonding between sulfur and hydrogens demonstrating a symmetrical arrangement. The geometry of the individual radical compound in relation to corresponding systems will be discussed. Ab initio calculations based on a linear three-center two-, three- and four-electron type of bonding clearly visualized in combination with the dynamics of the Van’t Hoff concept, as described by us in various papers, give a good description of this exclusive network. We also discuss the superconductivity of related phosphorus hydrides and focus on the stability and geometrical differences with respect to the H3S system. These differences are significant, demonstrating the diversity in various structures in showing superconductivity.

Solid-liquid state pressure bonding of Si_3N_4 ceramics with aluminum based alloys and its mechanism

Solid liquid state pressure bonding of Si 3N 4 ceramics with aluminum based alloys, which contain a small amount of intermetallic compounds Al 3Ti or Al 3Zr, was investigated. With this new method, the heat resistant properties of the bonding zone metal are improved, and the joints’ strengths at high temperature is increased. The joints’ shear strength at room temperature and at 600 ℃ reach 126～133 MPa and 32～34 MPa, respectively, with suitable bonding pressure. The reaction between aluminum and Si 3N 4 ceramics, which produces Al Si N O type compounds is the dominant interfacial reaction, while the reactions between the second active element Ti or Zr in the aluminum based alloys and Si 3N 4 ceramics also occur to some extend. [

Quick determination of gas pressure before uncovering coal in cross-cuts and shafts

The determination of gas pressure before uncovering coal in cross-cuts and in shafts is one of the important steps in pre- dicting coal and gas outbursts. However, the time spent for testing gas pressure is, at present, very long, seriously affecting the ap- plication of outburst prediction techniques in opening coal seams in cross-cuts and shafts. In order to reduce the time needed in gas pressure tests and to improve the accuracy of tests, we analyzed the process of gas pressure tests and examined the effect of the length of boreholes in coal seams in tests. The result shows that 1) the shorter the borehole, the easier the real pressure value of gas can be obtained and 2) the main factors affecting the time spent in gas pressure tests are the length of the borehole in coal seams, the gas emission time after the borehole has been formed and the quality of the borehole-sealing. The longer the length of the bore- hole, the longer the gas emission time and the larger the pressure-relief circle formed around the borehole, the longer the time needed for pressure tests. By controlling the length of the borehole in a test case in the Huainan mining area, and adopting a quick sealing technique using a sticky liquid method, the sealing quality was clearly improved and the gas emission time as well as the amount of gas discharged greatly decreased. Before the method described, the time required for the gas pressure to increase during the pressure test process, was more than 10 days. With our new method the required time is only 5 hours. In addition, the accuracy of the gas pressure test is greatly improved.

Sealing Performance and Optimization of a Subsea Pipeline Mechanical Connector

Researchers seldom study the optimum design of a mechanical connector for subsea oil-gas pipeline based upon the sealing performance. An optimal design method of a novel subsea pipeline mechanical connector is presented. By analyzing the static metal sealing mechanism, the critical condition of the sealing performance is established for this connector and the formulation method of the contact pressure on the sealing surface is created. By the method the minimum mean contact pressure of the 8.625 inch connector is calculated as 361 MPa, which is the constraint condition in the optimum design of connector.The finite element model is created in ANSYS Parametric Design Language(APDL) and the structure is optimized by the zero-order method, with variance of contact pressure as the objective function, and mean contact pressures and plastic strains as constraint variables. The optimization shows that variances of contact pressure on two sealing surfaces decrease by 72.41% and 89.33%, respectively, and mean contact pressures increase by 31.18% and 52.84%, respectively. The comparison of the optimal connectors and non-optimal connectors in the water pressure experiments and bending experiments shows that the sealing ability of optimized connectors is much higher than the rated pressure of 4.5 MPa, and the optimal connectors don’t leak under the bending moment of 52.2 kN·m.This research provides the formulation to solve contact pressure on the sealing surface and a structure optimization method to design the connectors with various dimensions.

In vitro study of nonthermal atmospheric pressure plasma in improving the durability of the dentin–adhesive interface with an etch-and-rinse system

In this study, we employed a nonthermal atmospheric pressure plasma(NTAPP) jet to evaluate the effect of plasma treatment on the durability of resin–dentin bonding under a thermocycling challenge. Furthermore, we assessed the degradation resistance of plasma-treated collagen under a sodium hypochlorite(NaClO) challenge. We assessed the beneficial effect of NTAPP treatment on the acid-etched dentin–bonding interface by testing the micro-tensile bond strength and examining the morphology. We found that the immediate bonding strength of the dentin significantly increased after NTAPP treatment. Compared with the control group, NTAPP resulted in a more prominent effect on the bonding durability of the dentin–adhesive interface after treatment for 5 or 10 s. Simultaneously, the mechanical strength of dentin collagen under the NaClO challenge was improved. Our results indicate that, in optimal conditions, NTAPP could be a promising method to protect dentin collagen and to improve the bonding durability between dentin and etch-and-rinse adhesives.

Experimental and Simulation Studies on Cold Welding Sealing Process of Heat Pipes

Sealing quality strongly affects heat pipe performance, but few studies focus on the process of heat pipe sealing. Cold welding sealing technology based on a stamping process is applied for heat pipe sealing. The bonding mechanism of the cold welding sealing process （CWSP） is investigated and compared with the experimental results obtained from the bonding interface analysis. An orthogonal experiment is conducted to observe the effects of various parameters, including the sealing gap, sealing length, sealing diameter, and sealing velocity on bonding strength. A method with the utilization of saturated vapor pressure inside a copper tube is proposed to evaluate bonding strength. A corresponding finite element model is developed to investigate the effects of sealing gap and sealing velocity on plastic deformation during the cold welding process. Effects of various parameters on the bonding strength are determined and it is found that the sealing gap is the most critical factor and that the sealing velocity contributes the least effect. The best parameter combination （AIB3CID3, with a 0.5 mm sealing gap, 6 mm sealing length, 3.8 mm sealing diameter, and 50 mm/s sealing velocity） is derived within the experimental parameters. Plastic deformation results derived from the finite element model are consistent with those from the experiment. The instruction for the CWSP of heat pipes and the design of sealing dies of heat pipes are provided.

3D TRANSIENT COUPLED THERMOELASTIC-PLASTIC CONTACT SEALING ANALYSIS OF REACTOR PRESSURE VESSEL

Sealing analysis of sealing system in reactor pressure vessels is relevant with multiple nonlinear coupled-field effects, so even large-scale commercial finite element software cannot finish the complicated analysis. A finite element method of 3D transient coupled thermo-elastic-plastic contact sealing analysis for reactor pressure vessels is presented, in which the surface nonlinearity, material nonlinearity, transient heat transfer nonlinearity and multiple coupled effect are taken into account and the sealing equation is coupling solved in iterative procedure. At the same time, a computational analysis program is developed, which is applied in the sealing analysis of experimental reactor pressure vessel, and the numerical results are in good coincidence with the experimental resuits. This program is also successful in analyzing the practical problem in engineering.

B-C Bond in Diamond Single Crystal Synthesized with h-BN Additive at High Pressure and High Temperature

The synthesis of diamond single crystal in the Fe64Ni36-C system with h-BN additive is investigated at pressure 6.5 GPa and temperature range of 1300-1400℃. The color of the obtained diamond crystals translates from yellow to dark green with increasing the h-BN addition. Fourier-transform infrared （FTIR） results indicate that sp2 hybridization B-N-B and B-N structures generate when the additive content reaches a certain value in the system. The two peaks are located at 745 and 1425cm-1, respectively. Fhrthermore, the FTIR characteristic peak resulting from nitrogen pairs is noticed and it tends to vanish when the h-BN addition reaches 1.1 wt%. Furthermore, Raman peak of the synthesized diamond shifts down to a lower wavenumber with increasing the h-BN ~ddition content in the synthesis system.

Study on Interfacial Bonding State of Ag-Cu in Cold Pressure Welding

The interfacial bonding of Ag-Cu (they are limited soluble) formed by the technology of cold pressure welding was discussed from the point of metallurgic view in this paper. Meanwhile, tensile test and microscopic test were adopted for studying the state of interfacial bonding, suggesting that the joint of Ag-Cu has not only strong welding joint but also atomic diffusion on the interface. For Ag-Cu, the interaction of dislocation caused by plastic deformation will cause the strain and the vibration of microconstructer defects, accompanied by emitting energy. The energy increases the atomic action and the amplitude of atomic vibration, and the result is that the atom can diffuse to several lattice parameters deep from interface to inner metals. Therefore, under the condition of chemical potential gradient, the special technique, cold pressure welding rather than basic requirements of diffusion should be taken into account. During the cold pressure welding, plastic deformation plays an important role for it causes the metals′ displacement, crystal defects, further activates the surface atoms. Finally, the fracture of atomic bonding leads to the atomic exchange and diffusion between the new metals′ surfaces.In other words the metals Ag,Cu can achieve solidate bonding by cold pressure welding accompanied by the atomic diffusion. Moreover, theoretical analysis and calculation on the basis of thermodynamics, crystallogy, so- lid physics,etc, have been applied to calculate the amount of atomic diffusion, which has further proved the testing results that joint Ag-Cu has strong bonding strength through the mechanism of atomic diffusion.

Formation of overpressure system and its relationship with the distribution of large gas fields in typical foreland basins in central and western China

Based on the data of measured formation pressure, drilling fluid density of key exploration wells and calculated pressure by well logging, combined with the analysis of natural gas geological conditions, the characteristics and formation mechanisms of formation fluid overpressure systems in different foreland basins and the relationship between overpressure systems and large-scale gas accumulation are discussed.(1) The formation mechanisms of formation overpressure in different foreland basins are different. The formation mechanism of overpressure in the Kuqa foreland basin is mainly the overpressure sealing of plastic salt gypsum layer and hydrocarbon generation pressurization in deep–ultra-deep layers, that in the southern Junggar foreland basin is mainly hydrocarbon generation pressurization and under-compaction sealing, and that in the western Sichuan foreland basin is mainly hydrocarbon generation pressurization and paleo-fluid overpressure residual.(2) There are three common characteristics in foreland basins, i.e. superimposed development of multi-type overpressure and multi-layer overpressure, strong–extremely strong overpressure developed in a closed foreland thrust belt, and strong–extremely strong overpressure developed in a deep foreland uplift area.(3) There are four regional overpressure sealing and storage mechanisms, which play an important role in controlling large gas fields, such as the overpressure of plastic salt gypsum layer, the overpressure formed by hydrocarbon generation pressurization, the residual overpressure after Himalayan uplift and denudation, and the under-compaction overpressure.(4) Regional overpressure is an important guarantee for forming large gas fields, the sufficient gas source, large-scale reservoir and trap development in overpressure system are the basic conditions for forming large gas fields, and the overpressure system is conducive to forming deep to ultra-deep large gas fields.

Mechanism and numerical simulation of pressure stagnation during water jetting perforation

When perforating with an abrasive water jet, it is possible that the pressure in the hole （perforation） will be higher than that in the annulus because of water jet blasting against the hole wall, which also is the theoretical basis for the technology of hydro-jet fracturing. This paper analyzes the mechanism of generating pressure stagnation in water jet hole, and puts forward a new concept of hydroseal. Then, the distribution of pressure in the hole was simulated with the finite element method. The simulation results showed that the pressure in the hole was higher than that in the annulus. Also, the lower the annular pressure （confining pressure） and the higher the blasting pressure, the greater the pressure difference. An experiment indicated that the cement sample was lifted up under the pressure stagnation in the hole, which proved the finite element simulation results obviously.

Analysis and optimization of nitrile butadiene rubber sealing mechanism of ball valve

An approach for analyzing and optimizing sealing mechanism of ball valve made of nitrile butadiene rubber(NBR) with finite element method was presented. The Mooney-Rivlin hyperelastic material model was chosen to characterize NBR sealing, as it has been recommended in the similar applications. That is, NBR sealing was modeled as incompressible hyperelasticity, as well as the assumption of isotropic flow. The results illustrate the structural pressure and contact pressure on the contact surface, which shows that the NBR sealing mechanism is very suitable for sealing after dimension optimization.

Gas Film Disturbance Characteristics Analysis of High-Speed and High-Pressure Dry Gas Seal

The dry gas seal（DGS） has been widely used in high parameters centrifugal compressor, but the intense vibrations of shafting, especially in high-speed condition, usually result in DGS＇s failure. So the DGS＇s ability of resisting outside interference has become a determining factor of the further development of centrifugal compressor. However, the systematic researches of which about gas film disturbance characteristics of high parameters DGS are very little. In order to study gas film disturbance characteristics of high-speed and high-pressure spiral groove dry gas seal（S-DGS） with a flexibly mounted stator, rotor axial runout and misalignment are taken into consideration, and the finite difference method and analytical method are used to analyze the influence of gas film thickness disturbance on sealing performance parameters, what＇s more, the effects of many key factors on gas film thickness disturbance are systematically investigated. The results show that, when sealed pressure is 10.1MPa and seal face average linear velocity is 107.3 m/s, gas film thickness disturbance has a significant effect on leakage rate, but has relatively litter effect on open force; Excessively large excitation amplitude or excessively high excitation frequency can lead to severe gas film thickness disturbance; And it is beneficial to assure a smaller gas film thickness disturbance when the stator material density is between 3.1 g/cm3 to 8.4 g/cm3; Ensuring sealing performance while minimizing support axial stiffness and support axial damping can help to improve dynamic tracking property of dry gas seal. The proposed research provides the instruction to optimize dynamic tracking property of the DGS.

Study on "fracturing-sealing" integration technology based on high-energy gas fracturing in single seam with high gas and low air permeability

To improve the gas extraction efficiency of single seam with high gas and low air permeability,we developed the"fracturing-sealing"integration technology,and carried out the engineering experiment in the3305 Tunliu mine.In the experiment,coal seams can achieve the aim of antireflection effect through the following process:First,project main cracks with the high energy pulse jet.Second,break the coal body by delaying the propellant blasting.Next,destroy the dense structure of the hard coal body,and form loose slit rings around the holes.Finally,seal the boreholes with the"strong-weak-strong"pressurized sealing technology.The results are as follows:The average concentration of gas extraction increases from8.3%to 39.5%.The average discharge of gas extraction increases from 0.02 to 0.10 m^3/min.The tunneling speeds up from 49.5 to 130 m/month.And the permeability of coal seams improves nearly tenfold.Under the same conditions,the technology is much more efficient in depressurization and antireflection than common methods.In other words,it will provide a more effective way for the gas extraction of single seam with high gas and low air permeability.

Experimental Verification and Research for the Distortion in the Integrated Frequency Responses of the High-Pressure Sealed Cabin and Magnetic Field Sensor

Although magnetotelluric sounding method applied to the land is advanced, there are many difficulties when it is applied to marine environment, one of which is how to lay magnetic field sensors down to the seafloor to complete measurements. To protect the magnetic field sensors from intense erosion and high pressure, suitable high-pressure sealed cabins must be designed to load them. For the consideration of magnetic measurement and marine operation, the sealed pressure cabin should be nonmagnetic and transportable. Among all optional materials, LC4 super.hard aluminum alloy has the highest performance of price/quality ratio to make the sealed pressure cabin. However, it does not mean that the high-pressure sealed cabin made using LC4 will be perfect in performance. In fact, because of its weak magnetism, the pressure cabin made using LC4 has distorting effect on frequency responses of the magnetic field sensors sealed in it. This distorting effect does not affect the use of the magnetic field sensor, but if we want to eliminate its effect, we should study it by experimental measurements. In our experiment tests, frequency sweep magnetic field as excitation signal was used, and then responses of the magnetic field sensor before and after being loaded into the high-pressure sealed cabin were measured. Finally, normalized abnormal curves for the frequency responses were obtained, through which we could show how the high-pressure sealed cabin produces effects on the responses of the magnetic field sensor. Experimental results suggest that the response distortion induced by the sealed pressure cabin appears on mid- and high-frequency areas. Using experimental results as standardization data, the frequency responses collected from seafloor magnetotelluric measurements can be corrected to restore real information about the seafloor field source.