Pressure stimulated current in progressive failure process of combined coal-rock under uniaxial compression:Response and mechanism

Effective monitoring of the structural health of combined coal-rock under complex geological conditions by pressure stimulated currents(PSCs)has great potential for the understanding of dynamic disasters in underground engineering.To reveal the effect of this way,the uniaxial compression experiments with PSC monitoring were conducted on three types of coal-rock combination samples with different strength combinations.The mechanism explanation of PSCs are investigated by resistivity test,atomic force microscopy(AFM)and computed tomography(CT)methods,and a PSC flow model based on progressive failure process is proposed.The influence of strength combinations on PSCs in the progressive failure process are emphasized.The results show the PSC responses between rock part,coal part and the two components are different,which are affected by multi-scale fracture characteristics and electrical properties.As the rock strength decreases,the progressive failure process changes obviously with the influence range of interface constraint effect decreasing,resulting in the different responses of PSC strength and direction in different parts to fracture behaviors.The PSC flow model is initially validated by the relationship between the accumulated charges of different parts.The results are expected to provide a new reference and method for mining design and roadway quality assessment.

Mechanical properties and damage characteristics of solidified body-coal combination in continuous driving and gangue backfilling

Recovery of the coal buried under buildings,railways and water bodies and the residual coal in irregularly arranged fully mechanized mining faces is a common engineering problem facing underground coal mining.In this study,a mining technology of continuous driving and gangue backfilling(CDGB)was proposed.The technology,which can not only alleviate ground subsidence and gangue discharge,but also release the above-mentioned coals,contributes to green and efficient sustainable development of mining.The stability of the system of the solidified body-reserved coal pillar combination(S-C combination)is crucial to the CDGB technology.Therefore,it is of great significance to explore the mechanical and damage characteristics of S-C combination in the synergistic bearing process.First,four sets of differentshaped S-C combination specimens were fabricated and a S-C combination bearing structure in CDGB was constructed to explore the differences in mechanical characteristics and damage modes of different-shaped S-C combination specimens during CDGB.Subsequently,their surface strain field evolutions and acoustic emission(AE)response characteristics in the load-bearing process were obtained with the aid of the digital image correlation technique and the AE signal monitoring system.Furthermore,a damage evolution model based on AE parameters and mechanical parameters was established to clarify the damage evolution law.The following results were obtained:(1)The free area of S-C combination can serve as a quantitative index to evaluate the stability of the overburden control system;(2)The concept of critical value k of the free area was first proposed.When the free area exceeds the critical value k(free area ratio greater than 1.13),the deformation resistance and the free area changes becomes negatively correlated;(3)As the free area expands,the failure of the S-C combination specimen evolves from tensile failure to shear failure.The distribution characteristics of the axial strain field also verified such a change in the failure mode;(4)When the free area expands,the peak AE count gradually changes from“double peaks”to“a single peak”.In this process,the expansion of free area shortens the time for accumulating and releasing energy during loading.Micro cracks generated in the specimen change from a phased steep growth to a continuous increase,and the process in which micro cracks develop,converge,intersect and connect to form macro cracks accelerates.The damage evolution law concluded based on AE parameters and mechanical parameters can well characterize the damage evolution process of S-C combination,providing certain reference for the study on the synergistic bearing of S-C combination during CDGB.

MECHANISM FOR THE INITIATION OF ACRYLONITRILE POLYMERIZATION BY POLYPROPYLENE-BASED POLYAMIDOXIME-THIOUREA COMBINATION

Polymerization of acrylonitrile (AN) in aqueous nitric acid initiated by polypropylene-based polyamidoxime (PPAO)-thiourea (TU) combination has been investigated. The overall rate of polymerization (R_p) under the conditions of [TU]/[PPAO]<0.5 molar ratio isThe molecular weights of the polymers were found to be inversely proportional to 3/2-power of nitric acid concentration and 1-power of thiourea concentration. In addition, it is independent with the concentrations of monomer and PPAO, and decreases with increasing temperature.On the basis of these experimental results, a coordination-proton transfer mechanism for the initiation was proposed and discussed.

Effects of water intrusion and loading rate on mechanical properties of and crack propagation in coal–rock combinations

Tackling the problems of underground water storage in collieries in arid regions requires knowledge of the effect of water intrusion and loading rate on the mechanical properties of and crack development in coal–rock combinations. Fifty-four coal–rock combinations were prepared and split equally into groups containing different moisture contents(dry, natural moisture and saturated) to conduct acoustic emission testing under uniaxial compression with loading rates ranging from 0.1 mm/min to 0.6 mm/min. The results show that the peak stress and strength-softening modulus, elastic modulus, strain-softening modulus, and post-peak modulus partly decrease with increasing moisture content and loading rate. In contrast, peak strain increases with increasing moisture content and fluctuates with rising loading rate. More significantly, the relationship between stiffness and stress, combined with accumulated counts of acoustic emission, can be used to precisely predict all phases of crack propagation. This is helpful in studying the impact of moisture content and loading rate on crack propagation and accurately calculating mechanical properties. We also determined that the stress thresholds of crack closure, crack initiation, and crack damage do not vary with changes of moisture content and loading rate, constituting 15.22%, 32.20%, and 80.98% of peak stress, respectively. These outcomes assist in developing approaches to water storage in coal mines, determining the necessary width of waterproof coal–rock pillars, and methods of supporting water-enriched roadways, while also advances understanding the mechanical properties of coal–rock combinations and laws of crack propagation.

Design and Experimental Research on Seedling Pick-Up Mechanism of Planetary Gear Train with Combined Non-circular Gear Transmission

Currently, transplanting mechanisms for dryland plug seedlings in China are mainly semiautomatic and have low efficiency. The rotary seedling pick-up mechanism with a planetary gear train for non-uniform intermittent transmission, and a concave and convex locking arc device, has a large rigid impact. To solve these problems, according to the design requirements for a dryland plug seedling transplanting mechanism, a rotary seedling pick-up mechanism of a planetary gear train with combined non-circular gear transmission of incomplete eccentric circular and noncircular gears was proposed. This has the characteristics of two-times greater fluctuation of the transmission ratio in a cycle, and can achieve a non-uniform continuous drive. Through analysis of the working principle of the seedling pick-up mechanism, its kinematics model was established. The human–computer interaction optimization method and self-developed computer-aided analysis and optimization software were used to obtain a set of parameters that satisfy the operation requirements of the seedling pick-up mechanism. According to the optimized parameters, the structure of the seedling pick-up mechanism was designed, a virtual prototype of the mechanism was created, and a physical prototype was manufactured. A virtual motion simulation of the mechanism was performed, high-speed photographic kinematics tests were conducted, and the kinematic properties of the physical prototype were investigated, whereby the correctness of the theoretical model and the optimized design of the mechanism were verified. Further, laboratory seedling pick-up tests were conducted. The success ratio of seedling pick-up was 93.8% when the seedling pick-up efficiency of the mechanism was 60 plants per minute per row, indicating that the mechanism has a high efficiency and success ratio for seedling pick-up and can be applied to a dryland plug seedling transplanter.

Research on system combination of machine translation based on Transformer

Influenced by its training corpus,the performance of different machine translation systems varies greatly.Aiming at achieving higher quality translations,system combination methods combine the translation results of multiple systems through statistical combination or neural network combination.This paper proposes a new multi-system translation combination method based on the Transformer architecture,which uses a multi-encoder to encode source sentences and the translation results of each system in order to realize encoder combination and decoder combination.The experimental verification on the Chinese-English translation task shows that this method has 1.2-2.35 more bilingual evaluation understudy(BLEU)points compared with the best single system results,0.71-3.12 more BLEU points compared with the statistical combination method,and 0.14-0.62 more BLEU points compared with the state-of-the-art neural network combination method.The experimental results demonstrate the effectiveness of the proposed system combination method based on Transformer.

The study on the mechanism of Sodium aescinate combined with Xuesaitong for cerebral thrombosis treatment

Objective:To observe the mechanism of Sodium aescinate combined with Xuesaitong for cerebral thrombosis treatment and offer clinical help to cerebral thrombosis treatment. Methods:A total of 92 patients with cerebral thrombosis were selected and randomly divided into groups: the observation group (46 people) and the control group (46 people).The patient in the control group were treated with conventional therapy and the patients in the observation group were treated with Sodium aescinate combined with Xuesaitong on the basis of conventional therapy. Inflammatory factors (IL-6, IL-10, TNF-α and CRP), Nerve cell factor (NSE, NGF and NTF) and blood rheology indexes (Fg, BVH, BVL and PV) were detected and analyzed before and after treatment.Results:The comparison of inflammatory factors, Nerve cell factor and blood rheology indexes in the two groups before treatment were not statistically significant. Inflammatory factors (IL-6, TNF-α and CRP), Nerve cell factor (NSE) and blood rheology indexes (Fg, BVH, BVL and PV) in both groups after treatment significantly decreased compared with that before treatment. Inflammatory factors (IL-10), Nerve cell factor (GF and NTF) in both groups after treatment significantly increased compared with that before treatment. The changes were statistically significant. Inflammatory factors (IL-6, TNF-α and CRP), Nerve cell factor (NSE) and blood rheology indexes (Fg, BVH, BVL and PV) in observation group after treatment decreased more significantly than that in control group, and inflammatory factors (IL-10), Nerve cell factor (GF and NTF) increased more significantly than that in control group. The difference between two groups was considered statistically significant.Conclusion:Sodium aescinate combined with Xuesaitong could inhibit the inflammatory reaction, improve the blood flow condition and promote rehabilitation in patients with cerebral thrombosis. So it has a very important clinical significance of the treatment to cerebral hemorrhage.

Dynamics Analysis of Square Unit and its Combined Mechanism with Joint Clearance

The deployable mechanisms consisting of square units are widely applied in aeronautics and astronautics,biomedicine, architecture and other fields, and joint clearance in such a mechanism is unavoidable. This study is carried out to accurately investigate the dynamic property of the mechanism.Firstly,a dynamics model was built by considering the motion characteristics between elements of joint with clearances. Secondly,based on Floures contact force model and LuGre friction force model,the tangential and normal contact force of revolute pair element with clearance were calculated respectively. Finally,square combined mechanisms' dynamic analytical method considering joint clearance was investigated, and constraint renege problem was resolved by adopting Baumgarte stable constraint method in integration process.Analytical result indicates that the impact of joint clearance on dynamic property of square combined mechanism should not be neglected.

Effects of scandium and zirconium combination alloying on as-cast microstructure and mechanical properties of Al-4Cu-1.5Mg alloy

The influences of minor scandium and zirconium combination alloying on the as-cast microstructure and mechanical properties of Al-4Cu-1.5Mg alloy have been experimentally investigated.The experimental results show that when the minor elements of scandium and zirconium are simultaneously added into the Al-4Cu-1.5Mg alloy,the as-cast microstructure of the alloy is effectively modified and the grains of the alloy are greatly refined.The coarse dendrites in the microstructure of the alloy without Sc and Zr additions are refined to the uniform and fine equiaxed grains.As the additions of Sc and Zr are 0.4% and 0.2%,respectively,the tensile strength,yield strength and elongation of the alloy are relatively better,which are 275.0 MPa,176.0 MPa and 8.0% respectively.The tensile strength is increased by 55.3%,and the elongation is nearly raised three times,compared with those of the alloy without Sc and Zr additions.

A combined moving mechanism with independent movement in longitudinal direction and transverse direction

To make the detecting robot move on the surface of the finned tubes, a novel combined moving mechanism is developed. The combined moving mechanism is composed of sprocket wheel and drum-like small wheel installed on the chain. It can make the robot move independently in the direction parallel to the tubes and in the direction perpendicular to the tubes. This paper made a detailed discussion on the composition of the combined moving mechanism, the design method of the conjugate outline curve and the circular-arc outline curve of the drum-like small wheel that meshes with the tubes. The error of the circular-arc outline curve is also analyzed.

Research on Cam-linkage Mechanism of Automatic Piecing Device

The principle of an automatic piecing device is presented, and the mathematic model of a specific combined mechanism of the automatic piecing device is analysed. The kinematics and dynamics equation of the combined mechanism is established on the basis of the mathematic model. By the virtual prototype technology, the motion of this mechanism is simulated, whose result is post-processed by ADAMS. To improve the output motion, according to the simulation output and automatic piecing device's practical working condition, the optimisation of the cam mechanism is carried out by finite difference method. The simulation result of this combined mechanism turns out in accordance with its theoretical analysis of virtual prototype in this research, which, therefore, lays a principle basis for the further study of automatic piecing device.

Research on mechanism of Jin-Shui-Liu-Jun-Jian and Acupoint Application combined therapy for chronic bronchitis

Objective:To investigate the influencing mechanism of Jin-Shui-Liu-Jun-Jian and Acupoint Application combined therapy on hemorheology, inflammatory factors and pulmonary functions in patients with chronic bronchitis, thus to offer relevant help for clinical therapies on patients with chronic bronchitis. Methods:120 cases of patients with chronic bronchitis treated in our hospital were selected and randomly divided to be the therapeutic group and the control group, 60 cases each. Patients in control group were provided some basic treatments, such as spasmolysis, anti-inflammation, asthma relieving, oxygen inhalation and dissolve phlegm. For therapeutic group on this basis, Jin-Shui-Liu-Jun-Jian and Acupoint Application combined therapy was provided. Hemorheology, inflammatory factors and pulmonary functions in the two groups of patients were detected before and after treatment. Results:Differences of hemorheology indexes, inflammatory factors and pulmonary function relevant indexes between the two groups of patients with chronic bronchitis before treatment showed no statistical significance (P>0.05). Compared with prior treatment, hemorheology relevant indexes [whole blood high shear viscosity (WHV), whole blood low shear viscosity (WLV), packed cell volume (PCV), plasma viscosity (PV) and red cell assembling index (RCAI)], inflammatory factors [IL-8 (interleukin-8) and TNF-α(tumor necrosis factor-α)] were significantly decreased and pulmonary function relevant indexes [forced vital capacity (FVC), forced expiratory volume in one second (FEV1.0), peak expiratory flow (PEF), maximal voluntary ventilation (MVV) and expiratory flow rate when exhale vital capacity was 0.50], inflammatory factors (IL-4, IL-2) were significantly increased in the two groups of patients with chronic bronchitis after relevant treatments;The differences between the groups showed statistical significance (P<0.05). After combined therapy provided, pulmonary function relevant indexes (FVC, FEV1.0, PEF, MVV and V0.50) and inflammatory factors (IL-4, IL-2) in therapeutic group were significantly higher than control group after basic therapy. Hemorheology relevant indexes (WHV, WLV, PV, PCV and RCAI) and inflammatory factors (IL-8 and TNF-α) in therapeutic group were significantly lower than control group;Differences between the two groups showed statistical significance (P<0.05). Conclusions: Combination of Jin-Shui-Liu-Jun-Jian and Acupoint Application significantly improved the levels of hemorheology, inflammatory factors and pulmonary functions in patients with chronic bronchitis. It has a great important clinical significance on therapies for patients with chronic bronchitis.

Mechanical performance of rock bolts under combined load conditions

Rock bolts are subjected to different loading conditions along their lengths such as axial,bending,and/or shear forces,which can cause failure at lower loads than those considered for design purposes.The common existing methodologies do not consider the actual loading of the rock bolts and assume it is only pure axial or pure shear.This study was conducted to investigate the un-grouted rock bolt performance under combined load conditions.Two loading regimes were evaluated:the effect of initial shear displacement on axial load capacity and displacement,and the effect of axial displacement on the shear load capacity.The first regime was also conducted for shear with a gap,when there is a spacing between the shear interfaces.The results of this study showed that the rock bolt can resist higher axial loads than shear under pure or combined load conditions.Under combined load conditions,the rock bolt capacity decreased significantly for both regimes.However,when applying the shear load with a gap,the rock bolt load capacity was not affected significantly.Also,the total bar deformation was improved for shear and axial.The findings of this study show the need to improve the rock bolt design considering the complex loading conditions in situ with/without a gap.

Design of Vegetable Pot Seedling Pick‑up Mechanism with Planetary Gear Train

It has been challenging to design seedling pick-up mechanism based on given key points and trajectories,because it involves dimensional synthesis and rod length optimization.In this paper,the dimensional synthesis of seedling pickup mechanism with planetary gear train was studied based on the data of given key points and the trajectory of the endpoint of seedling pick-up mechanism.Given the positions and orientations requirements of the five key points,the study first conducted a dimensional synthesis of the linkage size and center of rotation.The next steps were to select a reasonable solution and optimize the data values based on the ideal seedling trajectory.The link motion was driven by the planetary gear train of the two-stage gear.Four pitch curves of noncircular gears were obtained by calculating and distributing the transmission ratio according to the data.For the pitch curve with two convex points,the tooth profile design method of incomplete noncircular gear was applied.The seedling pick-up mechanism was tested by a virtual prototype and a physical prototype designed with the obtained parameter values.The results were consistent with the theoretical design requirements,confirming that the mechanism meets the expected requirements for picking seedlings up.This paper presents a new design method of vegetable pot seedling pick-up mechanism for an automatic vegetable transplanter.

Reagent types and action mechanisms in ilmenite flotation:A review

Ilmenite is an essential mineral for the extraction of titanium.Conventional physical separation methods have difficulty recovering fine ilmenite,and dressing plants have begun applying flotation to recover ilmenite.The interaction of reagent groups with Ti and Fe sites on the ilmenite surface dramatically influences the ilmenite flotation.However,the investigation on Fe sites has received more attention because the activity of Ti is lower than that of Fe.For the activators on ilmenite flotation,most are metal ions but typically lead ions.The metal ions of activators promote ilmenite flotation by increasing the active sites on the ilmenite surface.Combined reagents have a better selective separation of ilmenite than single reagents due to their synergistic effect.Combining the lead ion(Pb^(2+))and the benzyl hydroxamic acid(BHA)into a Pb-BHA complex has a marked effect on ilmenite flotation,which puts forward a new idea of developing combined reagents for ilmenite flotation.This review considers reagent types and action mechanisms in ilmenite flotation.On the basis of the analysis of previous research,a brief future outlook of reagent types and action mechanisms in ilmenite flotation is also proposed in this study.

Adsorption mechanism of sodium oleate and styryl phosphonic acid on rutile and amphibole surfaces

A reagent combination of sodium oleate(NaOl)and salicyl hydroximic acid was employed as the roughing and scavenging collectors,whereas styryl phosphoric acid(SPA)and octanol were employed as the cleaning collectors.Results of bench-scale flotation demonstrate that the dosage of SPA can be reduced by about 80%,and that a better flotation index can be obtained using the proposed reagent system.The results of adsorption amount and contact angle measurements indicate that the rutile surface adsorbed not only a large amount of residual NaOl but also SPA and a small amount of NaOl remained on the amphibole surface in strong acidic solution.The hydrophobic difference between rutile and amphibole surfaces was therefore amplified in cleaning,and their further separation became much easier consequently.

An Optimization Design of a Weft Insertion Mechanism for Rapier Looms

By analyzing a combined and spatial 6-bar linkage weft insertion mechanism, its practical model for optimization design is set up and the modification of penalty strategy is put forward so that the genetic algorithm can be better used in optimization design for mechanisms with non- linear constraints. The design result is discussed.

Effect of Zn^(2+)-Cu^(2+)combined heavy metal on mechanical properties and microstructure of clayey soil

The strength deterioration mechanism of soil polluted by heavy metals plays a crucial role in the research of mine site pollution.In this study,an unconfined compressive strength(UCS)test,a pH test,a scanning electron microscopy(SEM)test,a low filed nuclear magnetic resonance(NMR)test,and an X-ray diffraction(XRD)test were conducted on Zn^(2+),Cu^(2+) and the combination of Zn^(2+) and Cu^(2+) polluted soil to investigate the strength deterioration mechanism.The results show that both the UCS and pH value of soil decrease with increasing heavy metal concentration.The UCS of Zn^(2+)-Cu^(2+) combined polluted soil is between Zn^(2+) and Cu^(2+) polluted soil at the same total concentration.However,the deterioration rate of combined heavy metal polluted soil is less than the sum of deterioration rate of the two single polluted soils at the same total concentration.In addition,heavy metal cations in polluted soil cause flocculent gels of cosmids to shrink,the micropores to become smaller and the macropores to become larger.The porosity increases slightly with the increase of heavy metal concentration due to decreased pH value.The results from SEM,low field NMR,and pH could explain the dynamic evolution process of soil structure with different heavy metals and concentrations,which provides an experimental basis for mine-site polluted heavy metal treatment technology and the prediction of clayey soil strength deterioration.

Fault-sand combination modes and hydrocarbon accumulation in Binhai fault nose of Qikou Sag, Bohai Bay Basin, East China

Based on seismic and logging data,taking the downthrow fault nose of Binhai fault in Qikou Sag as the object of study,we analyzed fault characteristics,sand body distribution,fault-sand combinations and hydrocarbon accumulation to reveal the hydrocarbon enrichment law in the fault-rich area of fault depression lake basin.The results show that the Binhai Cenozoic fault nose is characterized by east-west zoning,the main part of the western fault segment is simple in structure,whereas the broom-shaped faults in the eastern segment are complex in structure,including several groups of faults.The difference of fault evolution controls the spatial distribution of sand bodies.The sand bodies are in continuous large pieces in the downthrow fault trough belt along the Gangdong Fault in the middle segment of the fault nose,forming consequent fault-sand combination;whereas the fault activity period of the eastern part of the fault nose was later,and the sand bodies controlled by paleogeomorphology are distributed in multi-phase north-south finger-shaped pattern,forming vertical fault-sand combination pattern matching with the fault.The configuration between faults and sand bodies,and oil sources and caprocks determine the vertical conductivity,plane distribution and vertical distribution of oil and gas.Two oil and gas accumulation modes,i.e.single main fault hydrocarbon supply-fault sand consequent matching-oil accumulation in multi-layers stereoscopically and fault system transportation-fault sand vertical matching-oil accumulation in banded overlapping layers occur in the middle and eastern segments of the fault nose respectively,and they control the difference of oil and gas distribution and enrichment degree in the Binhai fault nose.

An application of a combined gradient system to stabilize a mechanical system

A gradient system and a skew-gradient system can be merged into a combined gradient system. The differential equations of the combined gradient system are established and its property is studied. If a mechanical system can be represented as a combined gradient system, the stability of the mechanical system can be studied by using the property of the combined gradient system. Some examples are given to illustrate the applications of the results.