Dynamic destabilization analysis based on AE experiment of deep-seated,steep-inclined and extra-thick coal seam

No. 5 coal seam in Huating Coal Mine is a deep-seated, steep-inclined extra-thick coal seam where excavation disturbance is quite frequent. The maximum and minimum principal stresses differ widely. During mining, dynamical destabilization happens frequently and induce tragedies. Based on the comparison between the acoustic emission （AE） experiment on dynamical destabilization of coal rock and the related in situ testing results, this article provides comprehensive analysis on the regular quantificational AE patterns （energy rate, total events） of coal rock destabilization in complex-variable environment. The comparison parameters include dynamic tension energy rate, deformation resistance to compression, and shear stress.

Strength criterion effect of the translator and destabilization model of gas-bearing coal seam

Coal seam destabilization inflicts damage to equipment, causes property loss and personnel casualties,and severely threatens mining safety and efficient production. To further understand this destabilization based on the basic theory of Lippmann seam destabilization, a mathematical model was introduced for gas pressure distribution by considering intermediate principal stress and support resistance.Subsequently, we established a translation model suitable for the entire roadway coal seam with rocky roof and floor by applying the unified form of yield criterion in the state of plane strain. We also obtained the analytic expressions of coal seam stress distribution on both sides of the roadway and the widths of plastic and disturbance zones. Afterward, we analyzed several typical cases with different material yield criteria, obtained the plastic zone widths of the coal seam under different gas pressures, and assessed the effects of support resistance, roadway size, and coal strength on coal seam destabilization. Results showed that: the results obtained on the basis of Wilson and Mohr–Coulomb criteria are considerably conservative, and the use of Druker–Prager criteria to evaluate the rockburst-induced coal seam destabilization is safer than the use of the two other criteria; coal seam stability is correlated with gas pressure;and high-pressure gas accelerates the coal seam destabilization.

On the mechanism of Si-promoted destabilization of TiC_(x)particles in Al alloys

TiC_(x)is an excellent composite strengthening particle and grain refiner for Al alloys.However,the stability of TiC_(x)is poor when solute Si exists in Al alloy melts,which significantly depresses its strengthening and grain refining effects.In this work,the destabilization mechanisms of the TiC_(x)particles in Al-Si alloy melt with a composition of Al-7Si-7.5TiC were explored via experiments,first-principles calculations and thermodynamic calculations.The experimental results show that Si atoms diffuse into TiC_(x)and Ti atoms are released into the Al melt to form a Ti-rich transition zone during the insulation of TiC_(x)in Al-Si melt,and the TiAlySiz and Al_(4)C_(3)phases are solidified in the Ti-rich zone and at Ti-rich zone/TiC_(x)interface,respectively.The first principles calculations show that the low formation energy of C vacancies facilitates the rapid diffusion of Si atoms in TiC_(x),while the doping of Si atoms reduces the energy barrier of diffusion of Ti atoms in TiC_(x)and promotes the formation of Ti-rich zones.The thermodynamic calculations show that the wide crystallization temperature range of the destabilized product TiAlySiz phase is the key to continuous decomposition of TiC_(x)particles.In addition,the driving force of the main destabilization reaction of TiC_(x)in the Al-Si alloys is about 44 times higher than that in the Al alloys without Si addition.This indicates that the presence of solute Si remarkably promotes the subsequent decomposition process of TiC_(x)in the Al-Si alloy melts.

Mechanisms of eutectic lamellar destabilization upon rapid solidification of an undercooled Ag-39.9 at.% Cu eutectic alloy

The eutectic Ag-Cu alloys exhibiting fine Ag-Cu lamellar eutectic structure formed upon rapid solidification have great potentials being used in various engineering fields.However,the desired fine primary lamellar eutectic structure(PLES)is usually replaced by a coarse anomalous eutectic structure(AES)when the undercooling prior to solidification exceeds a certain value.The forming mechanism of AES in the undercooled eutectic Ag-Cu alloy has been a controversial issue.In this work,the undercooled Ag-39.9 at.% Cu eutectic alloy is solidified under different cooling conditions by using techniques of melt fluxing and copper mold casting.The results show that the coupled eutectic growth of this alloy undergoes a transition from a slow eutectic-cellular growth(ECG)to a rapid eutectic-dendritic growth(EDG)above a undercooling of 72 K,accompanying with an abrupt change of the distribution and amount of AES in as-solidified microstructures.Two kinds of primary lamellar eutectic structures are formed by ECG and EDG during recalescence,respectively.The destabilization of PLES that causes the formation of AES is ascribed to two different mechanisms based on the microstructural examination and theoretical calculations.Below 72 K,the destabilization of PLES formed by slow ECG is caused by the mechanism of"termination migration"driven by interfacial energy.While above 72 K,the destabilization of PLES formed by rapid EDG is attributed to the unstable perturbation of interface driven by interfacial energy and solute supersaturation.

Ultrasonic irradiation and solvent effects on destabilization of colloidal suspensions of platinum nanoparticles

In this work,ultrasonic irradiation and destabilizer solvent were used for destabilizing colloidal platinum dispersions.The stabilized platinum nanoparticles were prepared in w/o microemulsion systems composed of sodium bis-（2-ethylhexyl） sulfosuccinate（AOT） and four different solvents,namely,cyclohexane,n-hexane,n-heptane,and n-nonane.The recovery process of Pt nanoparticles from the colloidal systems was performed by exposing the colloidal samples to ultrasonic irradiation and applying various destabilizing solvents.Analysis of UV-visible spectra confirms that the quantity of Pt nanoparticles removed from the suspension depends on the length of time of the ultrasonic irradiation and the nature of the microemulsion oil phase.A critical time for the ultrasonic irradiation has been introduced for the phase separation of colloidal systems.To perform the solvent study,four destabilizer solvents,namely,dioxane,ethyl acetate,diethyl ether,and tetrahydrofuran,were used for breaking the colloidal suspension of platinum nanoparticles.Based on the ’good solvent’ and ’poor solvent’ idea,it is verified that the effect of the destabilizer solvents on the aggregation process follows the following order：tetrahydrofuran 〉 ethyl acetate 〉dioxane〉 diethyl ether.

Inclusion of CoTiO_(3) to ameliorate the re/dehydrogenation properties of the Mg–Na–Al system

For the first time,the MgH_(2)–NaAlH_(4)(ratio 4:1)destabilized system with CoTiO_(3) addition has been explored.The CoTiO_(3)-doped MgH_(2)–NaAlH_(4) sample begins to dehydrogenate at 130℃,which is declined by 40℃ compared to the undoped MgH_(2)–NaAlH_(4).Moreover,the de/rehydrogenation kinetics characteristics of the CoTiO_(3)-doped MgH_(2)–NaAlH_(4) were greatly ameliorated.With the inclusion of CoTiO_(3),the MgH_(2)–NaAlH_(4) composite absorbed 5.2 wt.%H_(2),higher than undoped MgH_(2)–NaAlH_(4).In the context of dehydrogenation,the CoTiO_(3)-doped MgH_(2)–NaAlH_(4) sample desorbed 2.6 wt.%H_(2),almost doubled compared to the amount of hydrogen desorbed from the undoped MgH_(2)–NaAlH_(4) sample.The activation energy obtained by the Kissinger analysis for MgH_(2) decomposition was significantly lower by 35.9 kJ/mol than the undoped MgH_(2)–NaAlH_(4) sample.The reaction mechanism demonstrated that new phases of MgCo and AlTi_(3) were generated in situ during the heating process and are likely to play a substantial catalytic function and be useful in ameliorating the de/rehydrogenation properties of the destabilized MgH_(2)–NaAlH_(4) system with the inclusion of CoTiO_(3).

The Impact of Different Mining and Releasing Ratios on the Over-Support Pressure of Header Working Face

Through the theoretical analysis of overburden destabilization mechanism, FLAC 3D simplified plane numerical simulation method and field measurement method, we compared the relationship of overburden support pressure at 35 m of workface recovery, and the peak overburden support pressure decreased from 13.85 Mpa to 11.97 Mpa from 1:1 to 1:3. With the increase of mining ratio, the peak over-supporting pressure decreases: with the increase of top coal recovery thickness, the peak over-supporting pressure and the influence range will be further expanded, and the distance between the peak over-supporting pressure and the coal wall of the working face will be further increased and the high stress zone of the peak area will be expanded simultaneously.

The Impact of Different Mining and Releasing Ratios on the Over-Support Pressure of Header Working Face

Through the theoretical analysis of overburden destabilization mechanism, FLAC 3D simplified plane numerical simulation method and field measurement method, we compared the relationship of overburden support pressure at 35 m of workface recovery, and the peak overburden support pressure decreased from 13.85 Mpa to 11.97 Mpa from 1:1 to 1:3. With the increase of mining ratio, the peak over-supporting pressure decreases: with the increase of top coal recovery thickness, the peak over-supporting pressure and the influence range will be further expanded, and the distance between the peak over-supporting pressure and the coal wall of the working face will be further increased and the high stress zone of the peak area will be expanded simultaneously.

A new mutually destabilized reactive hydride system:LiBH4–Mg2NiH4

In this work,the hydrogen sorption properties of the LiBH4-Mg2NiH4 composite system with the molar ratio 2:2.5 were thoroughly investigated as a function of the applied temperature and hydrogen pressure.To the best of our knowledge,it has been possible to prove experimentally the mutual destabilization between LiBH4 and Mg2NiH4.A detailed account of the kinetic and thermodynamic features of the dehydrogenation process is reported here.

Dissipation-induced instabilities and symmetry

The paradox of destabilization of a conservative or non-conservative system by small dissipation,or Ziegler’s paradox（1952）,has stimulated a growing interest in the sensitivity of reversible and Hamiltonian systems with respect to dissipative perturbations.Since the last decade it has been widely accepted that dissipation-induced instabilities are closely related to singularities arising on the stability boundary,associated with Whitney’s umbrella.The first explanation of Ziegler’s paradox was given（much earlier）by Oene Bottema in 1956.The aspects of the mechanics and geometry of dissipation-induced instabilities with an application to rotor dynamics are discussed.

Seismicity modulation by external stress perturbations in plate boundary vs.stable plate interior

Characterization of critically stressed seismogenic fault systems in diverse tectonic settings can be used to explore the stress/frictional condition of faults,along with its sensitivity for seismicity modulation by periodic stress perturbation.However,the process of seismicity modulation in response to external stress perturbation remains debated.In this paper,the characteristic difference in the seismicity modulation due to resonance destabilization phenomenon governed by rate-and-state friction is presented and val-idated with the globally reported cases of seismicity modulation in diverse tectonic settings.The rela-tively faster-moving plate boundary regions are equally susceptible for both shorter-period(e.g.,semi-diurnal,diurnal,and other small tidal constituents)and long-period(e.g.,semi-annual,annual,pole tide and pole wobble)seismicity modulation processes in response to stress perturbations from natural har-monic forcing,including tidal,semi-annual,annual,or multi-annual time scales.In contrast,slowly deforming stable plate interior regions and diffuse deformation zones appear to be more sensitive for long-period seismicity modulation of semi-annual,annual,or even multi-annual time scales but less sen-sitive for short-period seismicity modulation.This finding is also supported by the theoretical model pre-dictions from the resonance destabilization process and worldwide documented natural observations of seismicity modulation in diverse types of tectonic settings.

Superelastic behavior and stabilization of stress-induced martensite in Cu-13.4Al-4.0Ni single crystals

By applying tensile stress along 〈100〉 of β phase, the superelastic behavior and stabilization of stress induced martensite (SIM) of Cu 13.4Al 4.0Ni(mass fraction, %) single crystals were studied. The results show that the pseudo yield stress decreases with the increase of cycling number, and keeping load isothermally has an effect on stabilization of SIM. Previous thermal cycling between ( M s-20 ℃) and ( A f+20 ℃) promotes the superelasticity and the stabilization of SIM as well; the pre thermal cycling also reduces the pseudo yield stress. However, once the stabilization of SIM is produced, it can be destabilized by either the afterwards thermal cooling heating cycling or load and immediately unload cycling in ( A f～ M d). Isothermal treatment in ( A f～ M d) brings restabilization of SIM. The maximum superelastic value from β → β ′ 1(18 R ) is 9% for the studied single crystal. When test temperature is in A f～( A f+50 ℃) and stress is in 0～350 MPa, the superelastic behavior exist. [

Geological Context and Statistical Assessment of the Impacts of Sugarloaf Twin Disasters, in Western Sierra Leone

In the event of natural disasters, Sierra Leone like any other country loses lives as well as properties and natural resources. Despite notable occurrences of small disasters in the country, only on August 14th sugarloaf landslide and the resulting flash flood (twin disasters) which affected Regent and other communities in 2017 have captured both national and international attention due to their alarming impacts. To obtain a better knowledge on the nature of the disasters, this research considered the geological context of the landslide and focused on statistical analysis of the impacts of the twin disasters using Statistical Package for Social Sciences (SPSS). Geological field-based approach and self-administered questionnaires of both closed and open-ended questions, personal interviews and observations were adopted as research techniques. Descriptive statistics and qualitative analysis were used to analyze the data of the research. Relevant literature from books, journals, and newspapers was also consulted, including Radio, Television discussions and the internet. Slope destabilization that caused the Landslide was linked to the geology of sub-surface formation (highly weathered olivine gabbro), lineaments and the rate of weathering. Study showed remarkable economic, social and political impacts as a consequence of the twin disasters. Study also revealed that families assisted the most in both financial and non-financial ways to the victims, and renowned misappropriation of donated disaster funds. All variables tested using student t-distribution and chi-square test of independence accepted the hypothesis. Information obtained from this work could be fundamental for policy makers and development practitioners (Osuteye & Leck, 2017).

Ice-Cream Production from Lactose-Free UHT Milk

In this research,the samples of ice-cream made from control and lactose-free UHT milk were investigated in terms of their physical,chemical and organoleptic properties.The pH of samples varied between 6.28 and 6.36.The pH values of samples of cocoa were higher than that of plain samples.The overrun ratio of samples varied between 21.06%and 32.68%.The overrun ratio of lactose-free samples was lower than that of control samples.The melting ratio of samples varied from 0.45 g/min to 0.61 g/min.The fat destabilization index of samples was around 41.06%and 58.01%.The fat destabilization index of plain samples was higher than that of cocoa adding samples.The viscosity of ice cream samples was between 23.21 Pa·s-26.42 Pa·s.The viscosity of lactose-free ice-cream samples was higher than that of control ice-cream samples.The glucose ratio of samples was between 1.20%and 1.60%.The sucrose ratio of lactose-free samples was higher than that of control samples.As the lactose amount of samples of lactose-free plain and cocoa ice-cream were found 0.11%and 0.16%,respectively,the control samples contained lactose at high level as 1.11%and 1.04%.Panelists preferred the cocoa ice-cream to samples of plain ice-cream.

THE SOLUTION TO THE DESTABILIZING CRITICAL LOAD OF CIRCULAR DOUBLE ARTICULATED ARCH UNDER GOING VERTICAL DISTRIBUTIVE LOAD g_0/cos^2θ

In this paper, after taking th e effect of axis force on bending into consideration, the general potential ener gy for the circular double articulated arch is established undergoing vertical d istributive load g 0/ cos 2θ . With sufficient engineering precision, the fourth approximations to the destabilizing critical load of the arch under t his load are obtained by Ritz method. The approximations to the critical load ta ble are listed for various center angles of arch, and are contrasted with the cr itical load circular arch undergoing radial uniform load. Some reference results have been obtained.

Three-dimensional stability calculation method for high and large composite slopes formed by mining stope and inner dump in adjacent open pits

The 2D limit equilibrium method is widely used for slope stability analysis.However,with the advancement of dump engineering,composite slopes often exhibit significant 3D mechanical effects.Consequently,it is of significant importance to develop an effective 3D stability calculation method for composite slopes to enhance the design and stability control of open-pit slope engineering.Using the composite slope formed by the mining stope and inner dump in Baiyinhua No.1 and No.2 open-pit coal mine as a case study,this research investigates the failure mode of composite slopes and establishes spatial shape equations for the sliding mass.By integrating the shear resistance and sliding force of each row of microstrip columns onto the bottom surface of the strip corresponding to the main sliding surface,a novel 2D equivalent physical and mechanical parameters analysis method for the strips on the main sliding surface of 3D sliding masses is proposed.Subsequently,a comprehensive 3D stability calculation method for composite slopes is developed,and the quantitative relationship between the coordinated development distance and its 3D stability coefficients is examined.The analysis reveals that the failure mode of the composite slope is characterized by cutting-bedding sliding,with the arc serving as the side interface and the weak layer as the bottom interface,while the destabilization mechanism primarily involves shear failure.The spatial form equation of the sliding mass comprises an ellipsoid and weak plane equation.The analysis revealed that when the coordinated development distance is 1500 m,the error rate between the 3D stability calculation result and the 2D stability calculation result of the composite slope is less than 8%,thereby verifying the proposed analytical method of equivalent physical and mechanical parameters and the 3D stability calculation method for composite slopes.Furthermore,the3D stability coefficient of the composite slope exhibits an exponential correlation with the coordinated development distance,with the coefficient gradually decreasing as the coordinated development distance increases.These findings provide a theoretical guideline for designing similar slope shape parameters and conducting stability analysis.

The role of host refuge and strong Allee effects in a host-parasitoid system

We propose and study a discrete host-parasitoid model of difference equations with a spatial host refuge where hosts in the refuge patch are free from parasitism but undergo a demographic strong Allee effect.If the growth rate of hosts in the non-refuge patch is less than one,a host Allee threshold is derived below which both populations become extinct.It is proven that both populations can persist indefinitely if the host growth rate in the non-refuge patch exceeds one and the maximum reproductive number of parasitoids is greater than one.Numerical simulations reveal that the host refuge can either stabilize or destabilize the host-parasitoid interactions,depending on other model parameters.A large number of parasitoid turnover from a parasitized host may be detrimental to the parasitoids due to Allee effects in the hosts within the refuge patch.Moreover,it is demonstrated numerically that if the host growth rate is not small,the population level of parasitoids may suddenly drop to a small value as some parameters are varied.

The impact of acetylation and deacetylation on the p53 pathway

The p53 tumor suppressor is a sequence-specific transcription factor that undergoes an abundance of post-translational modifications for its regulation and activation.Acetylation of p53 is an important reversible enzymatic process that occurs in response to DNA damage and genotoxic stress and is indispensible for p53 transcriptional activity.p53 was the first non-histone protein shown to be acetylated by histone acetyl transferases,and a number of more recent in vivo models have underscored the importance of this type of modification for p53 activity.Here,we review the current knowledge and recent findings of p53 acetylation and deacetylation and discuss the implications of these processes for the p53 pathway.

HSP70 alleviates sepsis-induced cardiomyopathy by attenuating mitochondrial dysfunction-initiated NLRP3 inflammasome-mediated pyroptosis in cardiomyocytes

Background:Sepsis-induced cardiomyopathy(SIC)is an identified serious complication of sepsis that is associated with adverse outcomes and high mortality.Heat shock proteins(HSPs)have been implicated in suppressing septic inflammation.The aim of this study was to investigate whether HSP70 can attenuate cellular mitochondrial dysfunction,exuberated inflammation and inflammasome-mediated pyroptosis for SIC intervention.Methods:Mice with cecal ligation plus perforation(CLP)and lipopolysaccharide(LPS)-treated H9C2 cardiomyocytes were used as models of SIC.The mouse survival rate,gross profile,cardiac function,pathological changes and mitochondrial function were observed by photography,echocardiography,hematoxylin-eosin staining and transmission electron microscopy.In addition,cell proliferation and the levels of cardiac troponin I(cTnI),interleukin-1β(IL-1β)and tumor necrosis factor-α(TNF-α)were determined by Cell Counting Kit-8,crystal violet staining and enzyme-linked immunosorbent assay.Moreover,mitochondrial membrane potential was assessed by immunofluorescence staining,and dynamin-related protein 1 and pyroptosis-related molecules[nucleotide-binding domain,leucine-rich-repeat containing family pyrin domain-containing 3(NLRP3),caspase-1,gasdermin-D(GSDMD),gasdermin-D N-terminal(GSDMD-N)]were measured by western blotting,immunoprecipitation and immunoblotting.Finally,hsp70.1 knockout mice with CLP were used to verify the effects of HSP70 on SIC and the underlying mechanism.Results:Models of SIC were successfully established,as reduced consciousness and activity with liparotrichia in CLP mice were observed,and the survival rate and cardiac ejection fraction(EF)were decreased;conversely,the levels of cTnI,TNF-αand IL-1βand myocardial tissue damage were increased in CLP mice.In addition,LPS stimulation resulted in a reduction in cell viability,mitochondrial destabilization and activation of NLRP3-mediated pyroptosis molecules in vitro.HSP70 treatment improved myocardial tissue damage,survival rate and cardiac dysfunction caused by CLP.Additionally,HSP70 intervention reversed LPS-induced mitochondrial destabiliza-tion,inhibited activation of the NLRP3 inflammasome,caspase-1,GSDMD and GSDMD-N,and decreased pyroptosis.Finally,knockout of hsp70.1 mice with CLP aggravated cardiac dysfunction and upregulated NLRP3 inflammasome activity,and exogenous HSP70 significantly rescued these changes.It was further confirmed that HSP70 plays a protective role in SIC by attenuating mitochondrial dysfunction and inactivating pyroptotic molecules.Conclusions:Our study demonstrated that mitochondrial destabilization and NLRP3 inflammasome activation-mediated pyroptosis are attributed to SIC.Interestingly,HSP70 ameliorates sepsis-induced myocardial dysfunction by improving mitochondrial dysfunction and inhibiting the acti-vation of NLRP3 inflammasome-mediated pyroptosis,and such a result may provide approaches for novel therapies for SIC.

Simulating orthokinetic heterocoagulation and cluster growth in destabilizing suspensions

Using direct numerical simulation, we investigate the coagulation behavior of non-Brownian colloidal particles as exemplified by Al2O3 particles. This yields the so-called capture efficiency, for which we give an analytical expression, as well as other time-dependent variables such as the cluster growth rate. Instead of neglecting or strongly approximating the hydrodynamic interactions between particles, we include hydrodynamic and non-hydrodynamic interactions in a Stokesian dynamics approach and a comprehensive modeling of the interparticle forces. The resulting parallelized simulation framework enables us to investigate the dynamics of polydisperse particle systems composed of several hundred particles at the same high level of modeling we used for a close investigation of the coagulation behavior of two unequal particles in shear flow. Appropriate cluster detection yields all the information about large destabilizing systems, which is needed for models used in flow-sheet simulations. After non-dimensionalization, the results can be generalized and applied to other systems tending to secondary coagulation