Mechanical properties and energy evolutions of burst-prone coal samples with holes and fillings

During the mining process of impact-prone coal seams,drilling pressure relief can reduce the impact propensity of the coal seam,but it also reduces the integrity and strength of the coal mass at the side of the roadway.Therefore,studying the mechanical properties and energy evolution rules of coal samples containing holes and filled structures has certain practical significance for achieving coordinated control of coal mine rockburst disasters and the stability of roadway surrounding rocks.To achieve this aim,seven types of burst-prone coal samples were prepared and subject to uniaxial compression experiments with the aid of a TAW-3000 electro-hydraulic servo testing machine.Besides,the stress–strain curves,acoustic emission signals,DIC strain fields and other data were collected during the experiments.Furthermore,the failure modes and energy evolutions of samples with varying drilled hole sizes and filling materials were analyzed.The results show that the indexes related to burst propensity of the drilled coal samples decline to some extent compared with those of the intact one,and the decline is positively corelated to the diameter of the drilled hole.After hole filling,the strain concentration degree around the drilled hole is lowered to a certain degree,and polyurethane filling has a more remarkable effect than cement filling.Meanwhile,hole filling can enhance the strength and deformation resistance of coal.Hole drilling can accelerate the release of accumulated elastic strain energy,turning the acoustic emission events from low-frequency and high-energy ones to high-frequency and low-energy ones,whereas hole filling can reduce the intensity of energy release.The experimental results and theoretical derivation demonstrate that hole filling promotes coal deformability and strength mainly by weakening stress concentration surrounding the drilled holes.Moreover,the fillings can achieve a better filling effect if their elastic modulus and Poisson’s ratio are closer to those of the coal body.

Evolutions of sedimentary facies and palaeoenvironment and their controls on the development of source rocks in continental margin basins:A case study from the Qiongdongnan Basin,South China Sea

Hydrocarbon resources in the Qiongdongnan Basin have become an important exploration target in China.However,the development of high-quality source rocks in this basin,especially in its deep-water areas,are still not fully understood.In this study,evolutions of sedimentary facies and palaeoenvironment and their influences on the development of source rocks in diverse tectonic regions of the Qiongdongnan Basin were investigated.The results show that during the Oligocene and to Miocene periods,the sedimentary environment of this basin progressively varied from a semi-closed gulf to an open marine environment,which resulted in significant differences in palaeoenvironmental conditions of the water column for various tectonic regions of the basin.In shallow-water areas,the palaeoproductivity and reducibility successively decrease,and the hydrodynamic intensity gradually increases for the water columns of the Yacheng,Lingshui,and Sanya-Meishan strata.In deep-water areas,the water column of the Yacheng and Lingshui strata has a higher palaeoproductivity and a weaker hydrodynamic intensity than that of the Sanya-Meishan strata,while the reducibility gradually increases for the water columns of the Yacheng,Lingshui,and Sanya-Meishan strata.In general,the palaeoenvironmental conditions of the water column are the most favorable to the development of the Yacheng organic-rich source rocks.Meanwhile,the Miocene marine source rocks in the deep-water areas of the Qiongdongnan Basin may also have a certain hydrocarbon potential.The differences in the development models of source rocks in various tectonic regions of continental margin basins should be fully evaluated in the exploration and development of hydrocarbons.

Sedimentary elements,evolutions and controlling factors of the Miocene channel system:a case study of the deep-water Taranaki Basin in New Zealand

Deep-water channel systems are important petroleum reservoirs,and many have been discovered worldwide.Understanding deep-water channel sedimentary elements and evolution is helpful for deep-sea petroleum exploration and development.Based on high-resolution 3D seismic data,the Miocene channel system in the deep-water Taranaki Basin,New Zealand,was analyzed by using seismic interpretation techniques such as interlayer attribute extraction and strata slicing.The channel system was divided into five composite channels(CC-I to CC-V)according to four secondary level channel boundaries,and sedimentary elements such as channels,slump deposits,inner levees,mass transport deposits,and hemipelagic drape deposits were identified in the channel system.The morphological characteristics of several composite channels exhibited stark variances,and the overall morphology of the composite channels changed from relatively straight to highly sinuous to relatively straight.The evolution of the composite channels involved a gradual and repeated process of erosion and filling,and the composite channels could be divided into three evolutionary stages:initial erosion-filling,later erosion-filling(multistage),and channel abandonment.The middle Miocene channel system may have formed as a consequence of combined regional tectonic activity and global climatic change,and its intricate morphological alterations may have been influenced by the channel's ability to self-regulate and gravity flow properties.When studying the sedimentary evolution of a large-scale deep-water channel system in the Taranaki Basin during the Oligocene-Miocene,which transitioned from a passive margin to plate convergence,it can be understood how tectonic activity affected the channel and can also provide a theoretical reference for the evolution of the deepwater channels in areas with similar tectonic conversion environments around the world.

Effect of melting temperature on microstructural evolutions, behavior and corrosion morphology of Hadfield austenitic manganese steel in the casting process

In this study, the effect of melting temperature on the microstructural evolutions, behavior, and corrosion morphology of Hadfield steel in the casting process is investigated. The mold was prepared by the sodium silicate/CO_2 method, using a blind riser, and then the desired molten steel was obtained using a coreless induction furnace. The casting was performed at melting temperatures of 1350, 1400, 1450, and 1500°C, and the cast blocks were immediately quenched in water. Optical microscopy was used to analyze the microstructure, and scanning electron microscopy(SEM) and X-ray diffractrometry(XRD) were used to analyze the corrosion morphology and phase formation in the microstructure, respectively. The corrosion behavior of the samples was analyzed using a potentiodynamic polarization test and electrochemical impedance spectroscopy(EIS) in 3.5 wt% NaCl. The optical microscopy observations and XRD patterns show that the increase in melting temperature led to a decrease of carbides and an increase in the austenite grain size in the Hadfield steel microstructure. The corrosion tests results show that with increasing melting temperature in the casting process, Hadfield steel shows a higher corrosion resistance. The SEM images of the corrosion morphologies show that the reduction of melting temperature in the Hadfield steel casting process induced micro-galvanic corrosion conditions.

Evolutions of flow field and heat exchange on equa-torial Pacific surface in El Nino-La Nina cycle

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Computer Simulating Calculation on the Microstructure Evolutions during Hot Strip Rolling of C-Mn Steels

The program to predict the microstructure evolutions during hot strip rolling of C-M n steels has been developed in this paper, BV using this program, the microstructure changes with the processing parameters were analysed in detail. showing not only a good agreement of prediction with the measured values, but also entirely possibility to optimize hot strip rolling precess by computer simulation

On the Lagrange Stability of Motion and Final Evolutions in the Three-Body Problem

For the three-body problem, we consider the Lagrange stability. To analyze the stability, along with integrals of energy and angular momentum, we use relations by the author from [1], which band together separately squared mutual distances between bodies (mass points) and squared distances from bodies to the barycenter of the system. In this case, we prove the Lagrange stability theorem, which allows us to define more exactly the character of hyperbolic-elliptic and parabolic-elliptic final evolutions.

The Structural Evolutions of ZL109 Alloy and 7050 Alloy in the Semisolid Squeeze Casting Process

The structure evolutions of ZL109 alloy and 7050 alloy were studied in the processes of preparing raw billets by low super heat casting, remelting the raw billets, semisolid forming and heat treating components. The thin and symmetrical structure was obtained by using low super heat casting process. The eutectic that lied in the raw billet of ZL109 alloy remelted and produced liquid phase in the process of remelting, but to the 7050 alloy, the eutectic of intergranular and the pointedness of grains was remelted to make the grains more uniform and smooth. In the process of semisolid forming, the primary α and the eutectic inside the ZL109 alloy were separated partly and the grains in the 7050 alloy was conglutinated together. After heat treatment, the eutectic α grains of ZL109 traveled to primary α and shaped the white fishing net like organization; the eutectic Si grains assembled into the black massive particles. As to 7050, after heat treatment, α particles recrystallized and thin grains pattern was obtained.

Spectrum evolutions of spontaneous and pump-depleted stimulated Brillouin scatterings in liquid media

A theoretical model for calculating spontaneous and stimulated Brillouin scattering（SBS） spectra is described. An empirical formula for the Stokes output spectral linewidth, a function of spontaneous Brillouin linewidth and the exponential gain coefficient, is obtained by the calculated data fitting. The formula holds true for two cases involving pump undepletion and depletion. The lineshape change from spontaneous to highly pump-depleted SBS spectra is also investigated. The result shows that for the pump power below the SBS threshold, the Stokes output spectral lincshape evolves from Lorentzian to approximately Gaussian as the pump power increases. For the pump power near or beyond the threshold, the SBS spectrum is in the form of a steady Gaussian profile, and the spectral linewidth comes to a certain value about 7 times narrower than the spontaneous one. The theoretical results are experimentally demonstrated by using several common liquid media.

Structural evolutions and electronic properties of Au_nGd(n=6–15)small clusters:A first principles study

Structural, electronic, and magnetic properties of AunGd （n = 6-15） small clusters are investigated by using first principles spin polarized calculations and combining with the ab-initio evolutionary structure simulations. The calculated binding energies indicate that after doping a Gd atom AunGd cluster is obviously more stable than a pure AUn＋l cluster. Au6Gd with the quasiplanar structure has a largest magnetic moment of 7.421 gB. The Gd-4f electrons play an important role in determining the high magnetic moments of AunGd clusters, but in Au6Gd and Aul2Gd clusters the unignorable spin polarized effects from the Au-6s and Au-5d electrons further enhance their magnetism. The HOMO-LUMO （here, HOMO and LUMO stand for the highest occupied molecular orbital, and the lowest unoccupied molecular orbital, respectively） energy gaps of munGd clusters are smaller than those of pure AUn＋l clusters, indicating that AunGd clusters have potential as new catalysts with enhanced reactivity.

Evolution of energy and metal demand driven by industrial revolutions and its trend analysis

Industrial revolutions have a profound impact on energy and metal demand.Based on technological improvement,industrial transformation,and changes of energy and metal consumption in the United States,this paper identified the evolution characteristics of energy and metal demand driven by industrial revolutions,and analyzed the trends of energy and metal demand driven by the fourth industrial revolution which is happening currently.Results indicated that fossil fuels were the major energy sources which boosted up the past three industrial revolutions,whereas their consumption increased at a slowing pace as the economy was growing continually;after the third industrial revolution,the consumption of fossil fuels decoupled gradually with the economic growth.As the industrial structure transformed as the industrial revolutions went on,more and more metals were used in the industries,and the consumption of different metals showed different trends.In recent years,a new technological revolution has surged mainly driven by the overall application of new information technologies.The technological advance in information,new energies,new materials,etc.,will speed up the industrial transformation and exert a deep effect on the demand of energy and metals.It can be inferred that the ratio of clean,non-polluting,renewable energy will rise while the ratio of fossil fuels will drop in the energy demand,and the demand of rare metals will perhaps enter a fast-growing period,while the demand of traditional bulk metals will fluctuate at mid-high levels.Following the new industrial revolution,China should adopt an energy transition strategy of developing low-carbon and free-carbon technologies simultaneously,reinforce the domestic and international metal supply system with the aim of enhancing global governance capability,strengthen the deep development of rich rare metals and broaden the overseas supply channels of scare rare metals.

Evolutions of CHCN abundance in molecular clumps

To investigate the effects of massive star evolution on surrounding molecules,we select nine massive clumps previously observed with the Atacama Pathfinder Experiment(APEX) telescope and the Submillimeter Array(SMA) telescope.Based on the observations of APEX,we obtain luminosity to mass ratios Lclump/Mclump that range from 10 to 154 L_(⊙)/M_(⊙),where some of them embedded ultra compact(UC) H Ⅱ region.Using the SMA,CH3CN(12K-11K) transitions were observed toward nine massive starforming regions.We derive the CH3CN rotational temperature and column density using the XCLASS program,and calculate its fractional abundance.We find that CH3CN temperature seems to increase with the increase of Lclump/Mclump when the ratio is between 10 to 40 L_(⊙)/M_(⊙),then decrease when L_(clump)/M_(clump)≥ 40 L_(⊙)/M_(⊙).Assuming that the CH3CN gas is heated by radiation from the central star,the effective distance of CH3CN relative to the central star is estimated.The distance ranges from - 0.003 to - 0.083 pc,which accounts for - 1/100 to - 1/1000 of clump size.The effective distance increases slightly as Lclump/Mclump increases(Reff-(L_(clump)/M_(clump))0.5±0.2).Overall,the CH3 CN abundance is found to decrease as the clumps evolve,e.g.,XCH3CN -(L_(clump)/M_(clump))-1.0±0.7.The steady decline of CH3CN abundance as the clumps evolution can be interpreted as a result of photodissociation.

Evolutions of the Ruled Surfaces via the Evolution of Their Directrix Using Quasi Frame along a Space Curve

In this paper, evolutions of ruled surfaces generated by the quasi normal and quasi binormal vector fields of space curve are presented. These evolutions of the ruled surfaces depend on the evolutions of their directrix using quasi frame along a space curve.

A Unifying Theory of Dark Energy, Dark Matter, and Baryonic Matter in the Positive-Negative Mass Universe Pair: Protogalaxy and Galaxy Evolutions

This paper modifies the Farnes’ unifying theory of dark energy and dark matter which are negative-mass, created continuously from the negative-mass universe in the positive-negative mass universe pair. The first modification explains that observed dark energy is 68.6%, greater than 50% for the symmetrical positive-negative mass universe pair. This paper starts with the proposed positive-negative-mass 11D universe pair (without kinetic energy) which is transformed into the positive-negative mass 10D universe pair and the external dual gravities as in the Randall-Sundrum model, resulting in the four equal and separate universes consisting of the positive-mass 10D universe, the positive-mass massive external gravity, the negative-mass 10D universe and the negative-mass massive external gravity. The positive-mass 10D universe is transformed into 4D universe (home universe) with kinetic energy through the inflation and the Big Bang to create positive-mass dark matter which is five times of positive-mass baryonic matter. The other three universes without kinetic energy oscillate between 10D and 10D through 4D, resulting in the hidden universes when D > 4 and dark energy when D = 4, which is created continuously to our 4D home universe with the maximum dark energy = 3/4 = 75%. In the second modification to explain dark matter in the CMB, dark matter initially is not repulsive. The condensed baryonic gas at the critical surface density induces dark matter repulsive force to transform dark matter in the region into repulsive dark matter repulsing one another. The calculated percentages of dark energy, dark matter, and baryonic matter are 68.6 (as an input from the observation), 26 and 5.2, respectively, in agreement with observed 68.6, 26.5 and 4.9, respectively, and dark energy started in 4.33 billion years ago in agreement with the observed 4.71 ± 0.98 billion years ago. In conclusion, the modified Farnes’ unifying theory reinterprets the Farnes’ equations, and is a unifying theory of dark energy, dark matter, and baryonic matter in the positive-negative mass universe pair. The unifying theory explains protogalaxy and galaxy evolutions in agreement with the observations.

Time evolutions of scalar field perturbation in Schwarzschild de-Sitter black hole from Einstein-scalar–Gauss–Bonnet theory

The scalar-free black hole could be unstable against the scalar field perturbation when it is coupled to a Gauss–Bonnet(GB)invariant in a special form.It is known that the tachyonic instability in this scenario is triggered by the sufficiently strong GB coupling.In this paper,we focus on the time domain analysis of massive scalar field perturbation around the Schwarzschild de-Sitter black hole in Einstein-scalar–Gauss–Bonnet gravity.By analyzing the scalar field propagation,we find that the scalar field will finally grow when the GB coupling is large enough.This could lead to the instability of the background black hole.Furthermore,we demonstrate how the mass of the scalar field and the GB coupling strength affect the onset of tachyonic instability.

Evaporation Characteristics and Morphological Evolutions of Fuel Droplets After Hitting Different Wettability Surfaces

To solve the wall-wetting problem in internal combustion engines,the physical and chemical etching methods are used to prepare different wettability surfaces with various microstructures.The evaporation characteristics and morphological evolution processes of diesel and n-butanol droplets after hitting the various surfaces are investigated.The results show that the surface microstructures increase the surface roughness(Ra),enhancing the oleophilic property of the oleophilic surfaces.Compared with n-butanol droplets,the same surface shows stronger oleophobicity to diesel droplets.When a droplet hits an oleophilic property surface with a lower temperature,the stronger the oleophilicity,the shorter the evaporation time.For oleophilic surfaces,larger Ra leads to a higher Leidenfrost temperature(TLeid).The low TLeid caused by enhanced oleophobicity,dense microstructures and increased convex dome height facilitates droplet rebound and promotes the evaporation of the wall-impinging droplets into the cylinder.The evaporation rate of the droplets is not only related to the characteristics of the solid surfaces and the fuel droplets but also affected by the heat transfer rate to the droplets in different boiling regimes.The spreading diameter of a droplet on an oleophobic surface varies significantly less with time than that on an oleophilic surface under the same surface temperature.

In-situ study for the elastic structure evolutions of threedimensional Ir-O framework during the oxygen evolution reaction in acid

Understanding the dynamic structural and chemical evolutions at the catalyst-electrolyte interfaces is crucial for the development of active and stable electrocatalysts.In this work,β-Li_(2)IrO_(3)is employed as a model catalyst for the oxygen evolution reaction(OER).Its elastic three-dimensional Ir-O framework enables us to investigate the Li^(+)cation dissolution-induced structure evolutions and the formation mechanism of amorphous IrO_(x)species.Electrochemical measurements by rotating ring disk electrode(RRDE)reveal that up to 60%of the measured OER current can be ascribed to catalyst degradation.A series of in-situ X-ray diffraction spectroscopy(XRD),X-ray absorption spectroscopy(XAS),and Raman spectroscopy are conducted.Structure vibration is observed with oxidation states of Ir being reduced abnormally during OER at high potentials.It’s hypothesized that the reversible proton intercalations are responsible for the Ir turn-over mechanism.Results of this work demonstrate a stable and elastic iridate structure and reveal the initial catalyst degradation behaviors during OER in acid media.

Evolutions of Microstructure and Mechanical Properties in Mg-5Li-1Zn-0.5Ag-0.5Zr-xGd Alloy

The evolution of the microstructure and mechanical properties of alloy system with nominally composition Mg-5Li-1Zn-0.5Ag-0.5Zr-xGd(x=0,1.2,2.4,3.6,4.8,6)is evaluated based on computational phase diagram and corresponding experimental studies.The results show that grains are significantly refined with the increase of Gd content.The main phases of as-cast alloys areα-Mg,β-Li,AgLi_(2)Mg,and Mg_(3)Gd.With the increase of Gd content,the amounts of Mg_(3)Gd phase andβ-Li phase have been increased.When the Gd content exceeds 3.6 wt%,Mg_(3)Gd phase precipitates in a form of the network at the grain boundaries.The precipitation ofβ-Li can be attributed to the competitive dissolution of Zn,Gd,and Li in Mg.Meanwhile,γ″is formed after the addition of Gd,which grows and transforms intoγ′with the increase of Gd content.In solidification process,stacking faults are formed by solid transformation of partialα-Mg and Mg_(3)Gd.Eventually,with the synergistic effect of Mg_(3)Gd,β-Li,andγ″(orγ′),as the Gd content increasing,the tensile strength of the alloy first increases,then decreases,and the elongation decreases.When the content of Gd is 4.8 wt%,the ultimate tensile strength and yield strength reach the maximum values of 227 MPa and 139 MPa,and the elongation is 18.1%,respectively.

Deformable Catalytic Material Derived from Mechanical Flexibility for Hydrogen Evolution Reaction

Deformable catalytic material with excellent flexible structure is a new type of catalyst that has been applied in various chemical reactions,especially electrocatalytic hydrogen evolution reaction(HER).In recent years,deformable catalysts for HER have made great progress and would become a research hotspot.The catalytic activities of deformable catalysts could be adjustable by the strain engineering and surface reconfiguration.The surface curvature of flexible catalytic materials is closely related to the electrocatalytic HER properties.Here,firstly,we systematically summarized self-adaptive catalytic performance of deformable catalysts and various micro–nanostructures evolution in catalytic HER process.Secondly,a series of strategies to design highly active catalysts based on the mechanical flexibility of lowdimensional nanomaterials were summarized.Last but not least,we presented the challenges and prospects of the study of flexible and deformable micro–nanostructures of electrocatalysts,which would further deepen the understanding of catalytic mechanisms of deformable HER catalyst.

Experimental study on the effect of water absorption level on rockburst occurrence of sandstone

To investigate the mechanism of rockburst prevention by spraying water onto the surrounding rocks,15 experiments are performed considering different water absorption levels on a single face.High-speed photography and acoustic emission(AE)system are used to monitor the rockburst process.The effect of water on sandstone rockburst and the prevention mechanism of water on sandstone rockburst are analyzed from the perspective of energy and failure mode.The results show that the higher the ab-sorption degree,the lower the intensity of the rockburst after absorbing water on single side of sand-stone.This is reflected in the fact that with the increase in the water absorption level,the ejection velocity of rockburst fragments is smaller,the depth of the rockburst pit is shallower,and the AE energy is smaller.Under the water absorption level of 100%,the magnitude of rockburst intensity changes from medium to slight.The prevention mechanism of water on sandstone rockburst is that water reduces the capacity of sandstone to store strain energy and accelerates the expansion of shear cracks,which is not conducive to the occurrence of plate cracking before rockburst,and destroys the conditions for rockburst incubation.