The mechanical characteristics and acoustic behavior of rock masses are greatly influenced by stochastic joints.In this study,numerical models of rock masses incorporating intermittent joints with different numbers an...The mechanical characteristics and acoustic behavior of rock masses are greatly influenced by stochastic joints.In this study,numerical models of rock masses incorporating intermittent joints with different numbers and dip angles were produced using the finite element method(FEM)with the intrinsic cohesive zone model(ICZM).Then,the uniaxial compressive and wave propagation simulations were performed.The results indicate that the joint number and dip angle can affect the mechanical and acoustic properties of the models.The uniaxial compressive strength(UCS)and wave velocity of rock masses decrease monotonically as the joint number increases.However,the wave velocity grows monotonically as the joint dip angle increases.When the joint dip angle is 45°–60°,the UCS of the rock mass is lower than that of other dip angles.The wave velocity parallel to the joints is greater than that perpendicular to the joints.When the dip angle of joints remains unchanged,the UCS and wave velocity are positively related.When the joint dip angle increases,the variation amplitude of the UCS regarding the wave velocity increases.To reveal the effect of the joint distribution on the velocity,a theoretical model was also proposed.According to the theoretical wave velocity,the change in wave velocity of models with various joint numbers and dip angles was consistent with the simulation results.Furthermore,a theoretical indicator(i.e.fabric tensor)was adopted to analyze the variation of the wave velocity and UCS.展开更多
Phlorizin(PHL)is a natural compound with strong antioxidant properties mainly found in apples.In this paper,the interaction mechanism of PHL with pepsin and trypsin was comparatively evaluated by computer simulation,f...Phlorizin(PHL)is a natural compound with strong antioxidant properties mainly found in apples.In this paper,the interaction mechanism of PHL with pepsin and trypsin was comparatively evaluated by computer simulation,fluorescence spectra,circular dichroism(CD),and Fourier transform infrared(FT-IR)spectra at a molecular level.Fluorescence spectra showed that PHL quenches the pepsin/trypsin by static quenching.Thermodynamic parameters indicated that PHL binds to pepsin mainly through hydrogen bonds and van der Waals forces,and that of trypsin was electrostatic forces.The ground state complexes PHL and protease have a moderate affinity of 105 L/mol PHL binds more strongly to trypsin than to pepsin.CD and FT-IR spectra results showed that pepsin/trypsin decreased theβ-sheet content and slightly changed its secondary structure upon PHL.These experimental results are mutually verified with the predicted computer-aid simulation results.Upon PHL and trypsin binding,the antioxidant capacity of PHL was elevated.Nevertheless,the antioxidant capacity of PHL was decreased after binding to pepsin.This work elucidates the binding of PHL binding mechanisms to pepsin/trypsin and provides useful information for the digestion of PHL to improve the application of PHL in food processing.展开更多
Electric-field control of perpendicular magnetic anisotropy(PMA) is a feasible way to manipulate perpendicular magnetization,which is of great importance for realizing energy-efficient spintronics.Here,we propose a no...Electric-field control of perpendicular magnetic anisotropy(PMA) is a feasible way to manipulate perpendicular magnetization,which is of great importance for realizing energy-efficient spintronics.Here,we propose a novel approach to accomplish this task at room temperature by resistive switching(RS) via electrochemical metallization(ECM) in a device with the stack of Si/SiO_(2)/Ta/Pt/Ag/Mn-doped ZnO(MZO)/Pt/Co/Pt/ITO.By applying certain voltages,the device could be set at high-resistance-state(HRS) and low-resistance-state(LRS),accompanied with a larger and a smaller coercivity(H_(C)),respectively,which demonstrates a nonvolatile E-field control of PMA.Based on our previous studies and the present control experiments,the electric modulation of PMA can be briefly explained as follows.At LRS,the Ag conductive filaments form and pass through the entire MZO layer and finally reach the Pt/Co/Pt sandwich,leading to weakening of PMA and reduction of H_(C).In contrast,at HRS,most of the Ag filaments dissolve and leave away from the Pt/Co/Pt sandwich,causing partial recovery of PMA and an increase of H_(C).This work provides a new clue to designing low-power spintronic devices based on PMA films.展开更多
With the construction of new power systems,the power grid has become extremely large,with an increasing proportion of new energy and AC/DC hybrid connections.The dynamic characteristics and fault patterns of the power...With the construction of new power systems,the power grid has become extremely large,with an increasing proportion of new energy and AC/DC hybrid connections.The dynamic characteristics and fault patterns of the power grid are complex;additionally,power grid control is difficult,operation risks are high,and the task of fault handling is arduous.Traditional power-grid fault handling relies primarily on human experience.The difference in and lack of knowledge reserve of control personnel restrict the accuracy and timeliness of fault handling.Therefore,this mode of operation is no longer suitable for the requirements of new systems.Based on the multi-source heterogeneous data of power grid dispatch,this paper proposes a joint entity–relationship extraction method for power-grid dispatch fault processing based on a pre-trained model,constructs a knowledge graph of power-grid dispatch fault processing and designs,and develops a fault-processing auxiliary decision-making system based on the knowledge graph.It was applied to study a provincial dispatch control center,and it effectively improved the accident processing ability and intelligent level of accident management and control of the power grid.展开更多
BACKGROUND Preoperative evaluation of frailty is limited to a few surgical procedures.However,the evaluation in Chinese elderly gastric cancer(GC)patients remains blank.AIM To validate and estimate the prognostic valu...BACKGROUND Preoperative evaluation of frailty is limited to a few surgical procedures.However,the evaluation in Chinese elderly gastric cancer(GC)patients remains blank.AIM To validate and estimate the prognostic value of the 11-index modified frailty index(mFI-11)for predicting postoperative anastomotic fistula,intensive care unit(ICU)admission,and long-term survival in elderly patients(over 65 years of age)undergoing radical GC.METHODS This study was a retrospective cohort study which included patients who underwent elective gastrectomy with D2 Lymph node dissection between April 1,2017 and April 1,2019.The primary outcome was 1-year all-cause mortality.The secondary outcomes were admission to ICU,anastomotic fistula,and 6-mo mortality.Patients were divided into two groups according to the optimal grouping cutoff of 0.27 points from previous studies:High risk of frailty marked as mFI-11High and low risk of frailty marked as mFI-11Low.Survival curves between the two groups were compared,and univariate and multivariate regression analyses were performed to explore the relationship between preoperative frailty and postoperative complications in elderly patients undergoing radical GC.The discrimination ability of the mFI-11,prognostic nutritional index,and tumornode-metastasis pathological stage to identify adverse postoperative outcomes was assessed by calculating the area under the receiver operating characteristic(ROC)curve.RESULTS A total of 1003 patients were included,of which 13.86%(139/1003)were defined as having mFI-11High and 86.14%(864/1003)as having mFI-11Low.By comparing the incidence of postoperative complications in the two groups of patients,it was found that mFI-11High patients had higher rates of 1-year postoperative mortality,admission to ICU,anastomotic fistula,and 6-mo mortality than the mFI-11Low group(18.0%vs 8.9%,P=0.001;31.7%vs 14.7%,P<0.001;7.9%vs 2.8%,P<0.001;and 12.2%vs 3.6%,P<0.001).Multivariate analysis revealed mFI-11 as an independent predictive indicator for postoperative outcome[1-year postoperative mortality:Adjusted odds ratio(aOR)=4.432,95%confidence interval(95%CI):2.599-6.343,P=0.003;admission to ICU:aOR=2.058,95%CI:1.188-3.563,P=0.010;anastomotic fistula:aOR=2.852,95%CI:1.357-5.994,P=0.006;6-mo mortality:aOR=2.438,95%CI:1.075-5.484,P=0.033].mFI-11 showed better prognostic efficacy in predicting 1-year postoperative mortality[area under the ROC curve(AUROC):0.731],admission to ICU(AUROC:0.776),anastomotic fistula(AUROC:0.877),and 6-mo mortality(AUROC:0.759).CONCLUSION Frailty as measured by mFI-11 could provide prognostic information for 1-year postoperative mortality,admission to ICU,anastomotic fistula,and 6-mo mortality in patients over 65 years old undergoing radical GC.展开更多
Chronic obstructive pulmonary disease </span><span style="font-family:""><span style="font-family:Verdana;">(COPD) is a major chronic respiratory disease worldwide. Inflammat...Chronic obstructive pulmonary disease </span><span style="font-family:""><span style="font-family:Verdana;">(COPD) is a major chronic respiratory disease worldwide. Inflammatory cells reflect the </span><span style="font-family:Verdana;">inflammatory situation both in peripheral blood and induced sputum. </span></span><span style="font-family:""><span style="font-family:Verdana;">Their correlation has not been reported. </span><span style="font-family:Verdana;">The correlation between neutrophils (Neu), eosinophils (Eos), and lymphocyte (Lym) in induced sputum and that in peripheral blood of COPD </span><span style="font-family:Verdana;">patients was evaluated </span><span><span style="font-family:Verdana;">to explore the </span><span style="font-family:Verdana;">consistency of inflammatory cells in peripheral blood and induced sputum. Peripheral blood and induced sputum were collected from 437 </span><span style="font-family:Verdana;">patients with acute exacerbation of COPD</span></span><span style="font-family:Verdana;"> (AECOPD) who were hospitalized in the Department of respiratory and critical care medicine, Inner Mongolia People’s Hospital. </span><span style="font-family:Verdana;">The correlation analysis was performed by Spearman correlation analysis. </span><span style="font-family:Verdana;">The r</span><span style="font-family:Verdana;">atios of Neu, Eos, and Lym in induced sputum were (79.15 ± 22.60)%, (5.23 ± 12.74)%, and (1.69 ± 2.66)%. The ratios of </span><span style="font-family:Verdana;">Neu, Eos, and Lym in </span><span style="font-family:Verdana;">peripheral blood were (63.29 ± 11.44)%, (2.99 ± 3.60)%, and (25.16 ± 10.19)%. The results showed that the ratios of Neu and Eos in induced sputum were significantly correlated with the proportion of </span><span style="font-family:Verdana;">corresponding cells in peripheral blood (P < 0.05). </span><span style="font-family:Verdana;">There was no correlation between the ratio of Lym and Leu in induced sputum and corresponding cells in </span><span style="font-family:Verdana;">peripheral blood (P > 0.05). In patients with AECOPD, the tendency of Neu and Eos in induced sputum was </span><span style="font-family:Verdana;">consistent with the corresponding cells in peripheral blood. Neu and Eos in </span><span style="font-family:Verdana;">induced sputum and peripheral blood reflected the degree of inflammation to guide the individualized medication of patients.展开更多
Oyster(Crassostrea gigas),the main ingredient of oyster sauce,has a strong umami taste.In this study,three potential umami peptides,FLNQDEEAR(FR-9),FNKEE(FE-5),and EEFLK(EK-5),were identified and screened from the alc...Oyster(Crassostrea gigas),the main ingredient of oyster sauce,has a strong umami taste.In this study,three potential umami peptides,FLNQDEEAR(FR-9),FNKEE(FE-5),and EEFLK(EK-5),were identified and screened from the alcoholic extracts of the oyster using nano-HPLC-MS/MS analysis,i Umami-Scoring Card Method(i Umami-SCM)database and molecular docking(MD).Sensory evaluation and electronic tongue analysis were further used to confirm their tastes.The threshold of the three peptides ranged from 0.38 to 0.55 mg/m L.MD with umami receptors T1R1/T1R3 indicated that the electrostatic interaction and hydrogen bond interaction were the main forces involved.Besides,the Phe592 and Gln853 of T1R3 were the primary docking site for MD and played an important role in umami intensity.Peptides with two Glu residues at the terminus had stronger umami,especially at the C-terminus.These results contribute to the understanding of umami peptides in oysters and the interaction mechanism between umami peptides and umami receptors.展开更多
This study aims to improve the performances of the high-pressure water descaling technology used in steel hot rolling processes.In particular,a 2050 mm hot rolling line is considered,and the problem is investigated by...This study aims to improve the performances of the high-pressure water descaling technology used in steel hot rolling processes.In particular,a 2050 mm hot rolling line is considered,and the problem is investigated by means of a fluid–structure interaction(FSI)method by which the descaling effect produced by rolling coils with different section sizes is examined.Assuming a flat fan-shaped nozzle at the entrance of the R1R2 roughing mill,the outflow field characteristics and the velocity distribution curve on the strike line(at a target distance of 30–120 mm)are determined.It is found that the velocity in the center region of the water jet with different target distances is higher than that in the boundary region.As the target distance increases,the velocity of the water jet in the central region decreases.Through comparison with experimental results,it is shown that the simulation model can accurately predict the impact position of the high-pressure water on the impact plate,thereby providing a computational scheme that can be used to optimize the nozzle space layout and improve the slabs’descent effect for different rolling specifications.展开更多
The phenol and m-cresol biodegradations were studied using the mutant strain CTM 2 obtained by the He-Ne laser irradiation on wild-type Candida tropicalis.The results showed that C.tropicalis exhibited the increased c...The phenol and m-cresol biodegradations were studied using the mutant strain CTM 2 obtained by the He-Ne laser irradiation on wild-type Candida tropicalis.The results showed that C.tropicalis exhibited the increased capacity of phenolic compounds degradation after laser irradiation.It could degrade 2600 mg/L phenol and 300 mg/L m-cresol by 5% inoculum concentration,respectively.In the dual-substrate biodegradation system,0-500 mg/L phenol could accelerate m-cresol biodegradation,and 300 mg/L m-cresol could be completely utilized within 46 hr at the presence of 350 mg/L phenol.Besides,the maximum biodegradation of m-cresol could reach 350 mg/L with 80 mg/L phenol within 61 hr.Obviously,phenol,as a growth substrate,could promote CTM 2 to degrade m-cresol,and was always preferentially utilized as carbon source.Comparatively,low-concentration m-cresol could result in a great inhibition on phenol degradation.In addition,the kinetic behaviors of cell growth and substrate biodegradation were described by kinetic model proposed in our laboratory.展开更多
Objective: The recommended dose of prophylactic pegylated recombinant human granulocyte-colony stimulating factor(PEG rhG-CSF) is 100 μg/kg once per cycle for patients receiving intense-dose chemotherapy.However, few...Objective: The recommended dose of prophylactic pegylated recombinant human granulocyte-colony stimulating factor(PEG rhG-CSF) is 100 μg/kg once per cycle for patients receiving intense-dose chemotherapy.However, few data are available on the proper dose for patients receiving less-intense chemotherapy. The aim of this phase I study is to explore the proper dose and administration schedule of PEG rhG-CSF for patients receiving standard-dose chemotherapy.Methods:Eligible patients received 3-cycle chemotherapy every 3 weeks.No PEG rhG-CSF was given in the first cycle.Patients experienced grade 3 or 4 neutropenia would then enter the cycle 2 and 3.In cycle 2,patients received a single subcutaneous injection of prophylactic PEG rhG-CSF on d 3,and received half-dose subcutaneous injection in cycle 3 on d 3 and d 5,respectively.Escalating doses(30,60,100 and 200μg/kg)of PEG rhG-CSF were investigated.Results:A total of 26 patients were enrolled and received chemotherapy,in which 24 and 18 patients entered cycle 2 and cycle 3 treatment,respectively.In cycle 2,the incidence of grade 3 or 4 neutropenia for patients receiving single-dose PEG rhG-CSF of 30,60,100 and 200 μg/kg was 66.67%,33.33%,22.22% and 0,respectively,with a median duration less than 1(0–2)d.No grade 3 or higher neutropenia was noted in cycle 3 in all dose cohorts.Conclusions:The pharmacokinetic and pharmacodynamic profiles of PEG rhG-CSF used in cancer patients were similar to those reported,as well as the safety.Double half dose administration model showed better efficacy result than a single dose model in terms of grade 3 neutropenia and above.The single dose of 60 μg/kg,100 μg/kg and double half dose of 30 μg/kg were recommended to the phase Ⅱ study,hoping to find a preferable method for neutropenia treatment.展开更多
Cemented paste backfill(CPB),a mixture of tailings,binder,and water,is widely and extensively used for the recovery of mineral resources,the prevention of ground subsidence,and the management of mine waste.When instal...Cemented paste backfill(CPB),a mixture of tailings,binder,and water,is widely and extensively used for the recovery of mineral resources,the prevention of ground subsidence,and the management of mine waste.When installed,the CPB is subjected to complex environmental conditions such as water content,temperature,and power,which have a significant impact on its efficiency.Thus,this study conducts a series of laboratory programs,including investigation of moisture,temperature,stress–strain relation,and microstructure to show the effect of curing humidity on the CPB behaviors.The results obtained indicate that ambient humidity can have a dramatic effect on CPB in terms of its macro performance of internal relative humidity,temperature and strength,as well as the micro expression.Typical examples of these effects on CPB include an increase in curing humidity,which favors binder hydration,and then an increase in hydration materials,temperature and peak stress in the CPB.The results obtained will lead to a better understanding of CPB’s responses to various environmental conditions.展开更多
BACKGROUND Gastric cancer(GC)is a heavy burden in China.Nutritional support for GC patients is closely related to postoperative rehabilitation.However,the role of early oral feeding after laparoscopic radical total ga...BACKGROUND Gastric cancer(GC)is a heavy burden in China.Nutritional support for GC patients is closely related to postoperative rehabilitation.However,the role of early oral feeding after laparoscopic radical total gastrectomy in GC patients is unclear and high-quality research evidence is scarce.AIM To prospectively explore the safety,feasibility and short-term clinical outcomes of early oral feeding after laparoscopic radical total gastrectomy for GC patients.METHODS This study was a prospective cohort study conducted between January 2018 and December 2019 based in a high-volume tertiary hospital in China.A total of 206 patients who underwent laparoscopic radical total gastrectomy for GC were enrolled.Of which,105 patients were given early oral feeding(EOF group)after surgery,and the other 101 patients were given the traditional feeding strategy(control group)after surgery.Perioperative clinical data were recorded and analyzed.The primary endpoints were gastrointestinal function recovery time and postoperative complications,and the secondary endpoints were postoperative nutritional status,length of hospital stay and expenses,etc.RESULTS Compared with the control group,patients in the EOF group had a significantly shorter postoperative first exhaust time(2.48±1.17 d vs 3.37±1.42 d,P=0.001)and first defecation time(3.83±2.41 d vs 5.32±2.70 d,P=0.004).In addition,the EOF group had a significant shorter postoperative hospitalization duration(5.85±1.53 d vs 7.71±1.56 d,P<0.001)and lower postoperative hospitalization expenses(16.60±5.10 K¥vs 21.00±7.50 K¥,P=0.014).On the 5th day after surgery,serum prealbumin level(214.52±22.47 mg/L vs 204.17±20.62 mg/L,P=0.018),serum gastrin level(246.30±57.10 ng/L vs 223.60±55.70 ng/L,P=0.001)and serum motilin level(424.60±68.30 ng/L vs 409.30±61.70 ng/L,P=0.002)were higher in the EOF group.However,there was no significant difference in the incidence of total postoperative complications between the two groups(P=0.507).CONCLUSION Early oral feeding after laparoscopic radical total gastrectomy can promote the recovery of gastrointestinal function,improve postoperative nutritional status,reduce length of hospital stay and expenses while not increasing the incidence of related complications,which indicates its safety,feasibility and potential benefits for gastric cancer patients.展开更多
Al_2O_3/R141 b + Span-80 nanorefrigerant for 0.05 wt.% to 0.4 wt.% is prepared by ultrasonic vibration to investigate the influence of nanoparticle concentrations on flow boiling heat transfer of Al_2O_3/R141 b + Span...Al_2O_3/R141 b + Span-80 nanorefrigerant for 0.05 wt.% to 0.4 wt.% is prepared by ultrasonic vibration to investigate the influence of nanoparticle concentrations on flow boiling heat transfer of Al_2O_3/R141 b + Span-80 in micro heat exchanger by direct metal laser sintering. Experimental results show that nanoparticle concentrations have significantly impact on heat transfer coefficients by homogeneity test of variances according to mathematical statistics. The heat transfer performance of Al_2O_3/R141 b+ Span-80 nanorefrigerant is enhanced after adding nanoparticles in the pure refrigerant R141 b. The heat transfer coefficients of 0.05 wt.%, 0.1 wt.%, 0.2 wt.%, 0.3 wt.%and 0.4 wt.% Al_2O_3/R141 b + Span-80 nanorefrigerant respectively increase by 55.0%, 72.0%, 53.0%, 42.3% and 39.9% compared with the pure refrigerant R141 b. The particle fluxes from viscosity gradient, non-uniform shear rate and Brownian motion cause particles to migrate in fluid especially in the process of flow boiling. This migration motion enhances heat transfer between nanoparticles and fluid. Therefore, the heat transfer performance of nanofluid is enhanced. It is important to note that the heat transfer coefficients nonlinearly increase with nanoparticle concentrations increasing. The heat transfer coefficients reach its maximum value at the mass concentration of 0.1% and then it decreases slightly. There exists an optimal mass concentration corresponding to the best heat transfer enhancement. The reason for the above phenomenon is attributed to nanoparticles deposition on the minichannel wall by Scanning Electron Microscopy observation. The channel surface wettability increases during the flow boiling experiment in the mass concentration range from 0.2 wt.% to 0.4 wt.%. The channel surface with wettability increasing needs more energy to produce a bubble. Therefore, the heat transfer coefficients decrease with nanoparticle concentrations in the range from 0.2 wt.% to 0.4 wt.%. In addition, a new correlation has been proposed by fitting the experimental data considering the influence of mass concentrations on the heat transfer performance. The new correlation can effectively predict the heat transfer coefficient.展开更多
Cold metal transfer plus pulse(C+P)arc was applied in the additive manufacturing of 4043 Al alloy parts.Parameters in the manufacturing of the parts were investigated.The properties and microstructure of the parts wer...Cold metal transfer plus pulse(C+P)arc was applied in the additive manufacturing of 4043 Al alloy parts.Parameters in the manufacturing of the parts were investigated.The properties and microstructure of the parts were also characterized.Experimental results showed that welding at a speed of 8 mm/s and a wire feeding speed of 4.0 m/min was suitable to manufacture thin-walled parts,and the reciprocating scanning method could be adopted to manufacture thick-walled parts.The thin-walled parts of the C+P mode had fewer pores than those of the cold metal transfer(CMT)mode.The thin-and thick-walled parts of the C+P mode showed maximum tensile strengths of 172 and 178 MPa,respectively.Hardness decreased at the interface and in the coarse dendrite and increased in the refined grain area.展开更多
Magnoline(1),a new isoquinoline derivative,was isolated from the leaves of Magnolia sieboldii K.Koch(Magnoliaceae).Its structure was elucidated on the basis of spectral analysis including 1D,2D NMR and HR-TOF-MS.
A stable 3DOM CeO2 with well-defined inverse opal microstructure and crystalline walls structure has been successfully synthesized by application of three-dimensional order PMMA beads as templates. Structural feature ...A stable 3DOM CeO2 with well-defined inverse opal microstructure and crystalline walls structure has been successfully synthesized by application of three-dimensional order PMMA beads as templates. Structural feature of products was characterized by using SEM, DTA-TG, XRD.展开更多
This study aimed to evaluate the effects of baicalin on ultraviolet radiation B (UVB)-mediated microRNA (miRNA) expression in mouse skin.We determined miRNA expression profiles in UVB irradiated mice,baicalin treated ...This study aimed to evaluate the effects of baicalin on ultraviolet radiation B (UVB)-mediated microRNA (miRNA) expression in mouse skin.We determined miRNA expression profiles in UVB irradiated mice,baicalin treated irradiated mice,and untreated mice,and conducted TargetScan and Gene Ontology analyses to predict miRNA targets.Three miRNAs (mmu-miR-125a-5p,mmu-miR-146a,and mmu-miR-141) were downregulated and another three (mmu-miR-188-5p,mmu-miR-223 and mmu-miR-22) were upregulated in UVB irradiated mice compared with untreated mice.Additionally,these miRNAs were predicted to be related to photocarcinogenesis,hypomethylation and apoptosis.Three miRNAs (mmu-miR-378,mmu-miR-199a-3p and mmu-miR-181b) were downregulated and one (mmu-miR-23a) was upregulated in baicalin treated mice compared with UVB irradiated mice,and they were predicted to be related to DNA repair signaling pathway.These deregulated miRNAs are potentially involved in the pathogenesis of photodamage,and may aid treatment and prevention of UVB-induced dermatoses.展开更多
Rock burst is a catastrophic dynamic disaster caused by sudden failure and instability of coal, loading paths play an important role in the failure of coal, the coal failure process is associated with charge exception...Rock burst is a catastrophic dynamic disaster caused by sudden failure and instability of coal, loading paths play an important role in the failure of coal, the coal failure process is associated with charge exception infonnation. Hence, violent coal failure mechanics and time-frequency domain distribution of charge signal such as rock burst under different loading paths should be studied in-depth. In this paper, grade and cyclic loading test were carried out for coal with impact tendency samples produced by blocks cored from 800 depth in Xiaoqing coal mine of the Tiefa coal group in northeast China. Theory discussion was carried out for the result of stress and strain, frequency-spectra analysis was conducted for the wavelet charge data, figures showing the evolution mechanism of mechanical properties and the relationship of timefrequency domain amplitude of charge signals in coal with different loading paths and stage were obtained. The failure process and characteristics of coal under different loading paths were summarized. It found that the loading path changed the manner of energy accelerate-release, there were more plastic strain generation in coal under cyclic loading than that under grade loading, the former was more likely to cause greater damage and failure, then the strength of coal under cyclic loading is generally lower than that under grade loading, an energy conversion mechanical model of stress, damage and deformation was developed and explained the effect of the loading path. Charge signal was primarily distributed in the strengthening and peak stages, where there was a high amplitude pulse at each stress drop. The charge pulse was a type of low frequency signal with a primary frequency distribution range of 1 -100Hz. Discussion on the charge generating mechanism from the perspective of friction slip, it demonstrated that the charge obtained during the coal failure process directly to stress loaded on and damage, the result verified it better. We propose that the research results in this study could be efficiently applied to daily mining activities, to provide an early warning and effectively avoid rock burst disaster.展开更多
基金financial support from the National Key R&D Program of China(Grant No.2020YFA0711802).
文摘The mechanical characteristics and acoustic behavior of rock masses are greatly influenced by stochastic joints.In this study,numerical models of rock masses incorporating intermittent joints with different numbers and dip angles were produced using the finite element method(FEM)with the intrinsic cohesive zone model(ICZM).Then,the uniaxial compressive and wave propagation simulations were performed.The results indicate that the joint number and dip angle can affect the mechanical and acoustic properties of the models.The uniaxial compressive strength(UCS)and wave velocity of rock masses decrease monotonically as the joint number increases.However,the wave velocity grows monotonically as the joint dip angle increases.When the joint dip angle is 45°–60°,the UCS of the rock mass is lower than that of other dip angles.The wave velocity parallel to the joints is greater than that perpendicular to the joints.When the dip angle of joints remains unchanged,the UCS and wave velocity are positively related.When the joint dip angle increases,the variation amplitude of the UCS regarding the wave velocity increases.To reveal the effect of the joint distribution on the velocity,a theoretical model was also proposed.According to the theoretical wave velocity,the change in wave velocity of models with various joint numbers and dip angles was consistent with the simulation results.Furthermore,a theoretical indicator(i.e.fabric tensor)was adopted to analyze the variation of the wave velocity and UCS.
基金supported by the National Natural Science Foundation of China(21808020)the Applied Basic Research Program of Science&Technology Department of Sichuan Province(2018JY0151)。
文摘Phlorizin(PHL)is a natural compound with strong antioxidant properties mainly found in apples.In this paper,the interaction mechanism of PHL with pepsin and trypsin was comparatively evaluated by computer simulation,fluorescence spectra,circular dichroism(CD),and Fourier transform infrared(FT-IR)spectra at a molecular level.Fluorescence spectra showed that PHL quenches the pepsin/trypsin by static quenching.Thermodynamic parameters indicated that PHL binds to pepsin mainly through hydrogen bonds and van der Waals forces,and that of trypsin was electrostatic forces.The ground state complexes PHL and protease have a moderate affinity of 105 L/mol PHL binds more strongly to trypsin than to pepsin.CD and FT-IR spectra results showed that pepsin/trypsin decreased theβ-sheet content and slightly changed its secondary structure upon PHL.These experimental results are mutually verified with the predicted computer-aid simulation results.Upon PHL and trypsin binding,the antioxidant capacity of PHL was elevated.Nevertheless,the antioxidant capacity of PHL was decreased after binding to pepsin.This work elucidates the binding of PHL binding mechanisms to pepsin/trypsin and provides useful information for the digestion of PHL to improve the application of PHL in food processing.
基金Project supported by the National Key Research and Development Program of China (Grant No. 2022YFA1403602)the National Natural Science Foundation of China (Grant Nos. 51971109, 52025012, and 52001169)。
文摘Electric-field control of perpendicular magnetic anisotropy(PMA) is a feasible way to manipulate perpendicular magnetization,which is of great importance for realizing energy-efficient spintronics.Here,we propose a novel approach to accomplish this task at room temperature by resistive switching(RS) via electrochemical metallization(ECM) in a device with the stack of Si/SiO_(2)/Ta/Pt/Ag/Mn-doped ZnO(MZO)/Pt/Co/Pt/ITO.By applying certain voltages,the device could be set at high-resistance-state(HRS) and low-resistance-state(LRS),accompanied with a larger and a smaller coercivity(H_(C)),respectively,which demonstrates a nonvolatile E-field control of PMA.Based on our previous studies and the present control experiments,the electric modulation of PMA can be briefly explained as follows.At LRS,the Ag conductive filaments form and pass through the entire MZO layer and finally reach the Pt/Co/Pt sandwich,leading to weakening of PMA and reduction of H_(C).In contrast,at HRS,most of the Ag filaments dissolve and leave away from the Pt/Co/Pt sandwich,causing partial recovery of PMA and an increase of H_(C).This work provides a new clue to designing low-power spintronic devices based on PMA films.
基金supported by the Science and Technology Project of the State Grid Corporation“Research on Key Technologies of Power Artificial Intelligence Open Platform”(5700-202155260A-0-0-00).
文摘With the construction of new power systems,the power grid has become extremely large,with an increasing proportion of new energy and AC/DC hybrid connections.The dynamic characteristics and fault patterns of the power grid are complex;additionally,power grid control is difficult,operation risks are high,and the task of fault handling is arduous.Traditional power-grid fault handling relies primarily on human experience.The difference in and lack of knowledge reserve of control personnel restrict the accuracy and timeliness of fault handling.Therefore,this mode of operation is no longer suitable for the requirements of new systems.Based on the multi-source heterogeneous data of power grid dispatch,this paper proposes a joint entity–relationship extraction method for power-grid dispatch fault processing based on a pre-trained model,constructs a knowledge graph of power-grid dispatch fault processing and designs,and develops a fault-processing auxiliary decision-making system based on the knowledge graph.It was applied to study a provincial dispatch control center,and it effectively improved the accident processing ability and intelligent level of accident management and control of the power grid.
文摘BACKGROUND Preoperative evaluation of frailty is limited to a few surgical procedures.However,the evaluation in Chinese elderly gastric cancer(GC)patients remains blank.AIM To validate and estimate the prognostic value of the 11-index modified frailty index(mFI-11)for predicting postoperative anastomotic fistula,intensive care unit(ICU)admission,and long-term survival in elderly patients(over 65 years of age)undergoing radical GC.METHODS This study was a retrospective cohort study which included patients who underwent elective gastrectomy with D2 Lymph node dissection between April 1,2017 and April 1,2019.The primary outcome was 1-year all-cause mortality.The secondary outcomes were admission to ICU,anastomotic fistula,and 6-mo mortality.Patients were divided into two groups according to the optimal grouping cutoff of 0.27 points from previous studies:High risk of frailty marked as mFI-11High and low risk of frailty marked as mFI-11Low.Survival curves between the two groups were compared,and univariate and multivariate regression analyses were performed to explore the relationship between preoperative frailty and postoperative complications in elderly patients undergoing radical GC.The discrimination ability of the mFI-11,prognostic nutritional index,and tumornode-metastasis pathological stage to identify adverse postoperative outcomes was assessed by calculating the area under the receiver operating characteristic(ROC)curve.RESULTS A total of 1003 patients were included,of which 13.86%(139/1003)were defined as having mFI-11High and 86.14%(864/1003)as having mFI-11Low.By comparing the incidence of postoperative complications in the two groups of patients,it was found that mFI-11High patients had higher rates of 1-year postoperative mortality,admission to ICU,anastomotic fistula,and 6-mo mortality than the mFI-11Low group(18.0%vs 8.9%,P=0.001;31.7%vs 14.7%,P<0.001;7.9%vs 2.8%,P<0.001;and 12.2%vs 3.6%,P<0.001).Multivariate analysis revealed mFI-11 as an independent predictive indicator for postoperative outcome[1-year postoperative mortality:Adjusted odds ratio(aOR)=4.432,95%confidence interval(95%CI):2.599-6.343,P=0.003;admission to ICU:aOR=2.058,95%CI:1.188-3.563,P=0.010;anastomotic fistula:aOR=2.852,95%CI:1.357-5.994,P=0.006;6-mo mortality:aOR=2.438,95%CI:1.075-5.484,P=0.033].mFI-11 showed better prognostic efficacy in predicting 1-year postoperative mortality[area under the ROC curve(AUROC):0.731],admission to ICU(AUROC:0.776),anastomotic fistula(AUROC:0.877),and 6-mo mortality(AUROC:0.759).CONCLUSION Frailty as measured by mFI-11 could provide prognostic information for 1-year postoperative mortality,admission to ICU,anastomotic fistula,and 6-mo mortality in patients over 65 years old undergoing radical GC.
文摘Chronic obstructive pulmonary disease </span><span style="font-family:""><span style="font-family:Verdana;">(COPD) is a major chronic respiratory disease worldwide. Inflammatory cells reflect the </span><span style="font-family:Verdana;">inflammatory situation both in peripheral blood and induced sputum. </span></span><span style="font-family:""><span style="font-family:Verdana;">Their correlation has not been reported. </span><span style="font-family:Verdana;">The correlation between neutrophils (Neu), eosinophils (Eos), and lymphocyte (Lym) in induced sputum and that in peripheral blood of COPD </span><span style="font-family:Verdana;">patients was evaluated </span><span><span style="font-family:Verdana;">to explore the </span><span style="font-family:Verdana;">consistency of inflammatory cells in peripheral blood and induced sputum. Peripheral blood and induced sputum were collected from 437 </span><span style="font-family:Verdana;">patients with acute exacerbation of COPD</span></span><span style="font-family:Verdana;"> (AECOPD) who were hospitalized in the Department of respiratory and critical care medicine, Inner Mongolia People’s Hospital. </span><span style="font-family:Verdana;">The correlation analysis was performed by Spearman correlation analysis. </span><span style="font-family:Verdana;">The r</span><span style="font-family:Verdana;">atios of Neu, Eos, and Lym in induced sputum were (79.15 ± 22.60)%, (5.23 ± 12.74)%, and (1.69 ± 2.66)%. The ratios of </span><span style="font-family:Verdana;">Neu, Eos, and Lym in </span><span style="font-family:Verdana;">peripheral blood were (63.29 ± 11.44)%, (2.99 ± 3.60)%, and (25.16 ± 10.19)%. The results showed that the ratios of Neu and Eos in induced sputum were significantly correlated with the proportion of </span><span style="font-family:Verdana;">corresponding cells in peripheral blood (P < 0.05). </span><span style="font-family:Verdana;">There was no correlation between the ratio of Lym and Leu in induced sputum and corresponding cells in </span><span style="font-family:Verdana;">peripheral blood (P > 0.05). In patients with AECOPD, the tendency of Neu and Eos in induced sputum was </span><span style="font-family:Verdana;">consistent with the corresponding cells in peripheral blood. Neu and Eos in </span><span style="font-family:Verdana;">induced sputum and peripheral blood reflected the degree of inflammation to guide the individualized medication of patients.
基金supported by the National Key Research and Development Program of China:Investigate the mechanism of formation and control technologies of Chinese traditional and ethnic food quality(2021YFD2100100)。
文摘Oyster(Crassostrea gigas),the main ingredient of oyster sauce,has a strong umami taste.In this study,three potential umami peptides,FLNQDEEAR(FR-9),FNKEE(FE-5),and EEFLK(EK-5),were identified and screened from the alcoholic extracts of the oyster using nano-HPLC-MS/MS analysis,i Umami-Scoring Card Method(i Umami-SCM)database and molecular docking(MD).Sensory evaluation and electronic tongue analysis were further used to confirm their tastes.The threshold of the three peptides ranged from 0.38 to 0.55 mg/m L.MD with umami receptors T1R1/T1R3 indicated that the electrostatic interaction and hydrogen bond interaction were the main forces involved.Besides,the Phe592 and Gln853 of T1R3 were the primary docking site for MD and played an important role in umami intensity.Peptides with two Glu residues at the terminus had stronger umami,especially at the C-terminus.These results contribute to the understanding of umami peptides in oysters and the interaction mechanism between umami peptides and umami receptors.
基金The research was funded by Science and Technology Project of Hebei Education Department(Project Number:QN2022198).Y.C.received the grant.
文摘This study aims to improve the performances of the high-pressure water descaling technology used in steel hot rolling processes.In particular,a 2050 mm hot rolling line is considered,and the problem is investigated by means of a fluid–structure interaction(FSI)method by which the descaling effect produced by rolling coils with different section sizes is examined.Assuming a flat fan-shaped nozzle at the entrance of the R1R2 roughing mill,the outflow field characteristics and the velocity distribution curve on the strike line(at a target distance of 30–120 mm)are determined.It is found that the velocity in the center region of the water jet with different target distances is higher than that in the boundary region.As the target distance increases,the velocity of the water jet in the central region decreases.Through comparison with experimental results,it is shown that the simulation model can accurately predict the impact position of the high-pressure water on the impact plate,thereby providing a computational scheme that can be used to optimize the nozzle space layout and improve the slabs’descent effect for different rolling specifications.
基金supported by the Youth Academic Cadreman Project of Heilongjiang Provincial Education Department (No.1152G068)the Natural Science Foundation of Heilongjiang Provincial (No.B200819)the 41st Science Fund of China Postdoctor (No.20070410268)
文摘The phenol and m-cresol biodegradations were studied using the mutant strain CTM 2 obtained by the He-Ne laser irradiation on wild-type Candida tropicalis.The results showed that C.tropicalis exhibited the increased capacity of phenolic compounds degradation after laser irradiation.It could degrade 2600 mg/L phenol and 300 mg/L m-cresol by 5% inoculum concentration,respectively.In the dual-substrate biodegradation system,0-500 mg/L phenol could accelerate m-cresol biodegradation,and 300 mg/L m-cresol could be completely utilized within 46 hr at the presence of 350 mg/L phenol.Besides,the maximum biodegradation of m-cresol could reach 350 mg/L with 80 mg/L phenol within 61 hr.Obviously,phenol,as a growth substrate,could promote CTM 2 to degrade m-cresol,and was always preferentially utilized as carbon source.Comparatively,low-concentration m-cresol could result in a great inhibition on phenol degradation.In addition,the kinetic behaviors of cell growth and substrate biodegradation were described by kinetic model proposed in our laboratory.
基金supported by Hangzhou Jiuyuan Gene Engineering Co., Ltdpartly funded by the Chinese National Science and Technology Major Project on Key New Drug Creation (2012ZX09303-012)Beijing Municipal Science & Technology Commission Major Project for New Drug Innovation (Z111102071011001), China
文摘Objective: The recommended dose of prophylactic pegylated recombinant human granulocyte-colony stimulating factor(PEG rhG-CSF) is 100 μg/kg once per cycle for patients receiving intense-dose chemotherapy.However, few data are available on the proper dose for patients receiving less-intense chemotherapy. The aim of this phase I study is to explore the proper dose and administration schedule of PEG rhG-CSF for patients receiving standard-dose chemotherapy.Methods:Eligible patients received 3-cycle chemotherapy every 3 weeks.No PEG rhG-CSF was given in the first cycle.Patients experienced grade 3 or 4 neutropenia would then enter the cycle 2 and 3.In cycle 2,patients received a single subcutaneous injection of prophylactic PEG rhG-CSF on d 3,and received half-dose subcutaneous injection in cycle 3 on d 3 and d 5,respectively.Escalating doses(30,60,100 and 200μg/kg)of PEG rhG-CSF were investigated.Results:A total of 26 patients were enrolled and received chemotherapy,in which 24 and 18 patients entered cycle 2 and cycle 3 treatment,respectively.In cycle 2,the incidence of grade 3 or 4 neutropenia for patients receiving single-dose PEG rhG-CSF of 30,60,100 and 200 μg/kg was 66.67%,33.33%,22.22% and 0,respectively,with a median duration less than 1(0–2)d.No grade 3 or higher neutropenia was noted in cycle 3 in all dose cohorts.Conclusions:The pharmacokinetic and pharmacodynamic profiles of PEG rhG-CSF used in cancer patients were similar to those reported,as well as the safety.Double half dose administration model showed better efficacy result than a single dose model in terms of grade 3 neutropenia and above.The single dose of 60 μg/kg,100 μg/kg and double half dose of 30 μg/kg were recommended to the phase Ⅱ study,hoping to find a preferable method for neutropenia treatment.
基金The financial support from Yue Qi Young Scholar Project,China University of Mining and Technology-BeijingChina Scholarship CouncilBGRIMM Technology Group。
文摘Cemented paste backfill(CPB),a mixture of tailings,binder,and water,is widely and extensively used for the recovery of mineral resources,the prevention of ground subsidence,and the management of mine waste.When installed,the CPB is subjected to complex environmental conditions such as water content,temperature,and power,which have a significant impact on its efficiency.Thus,this study conducts a series of laboratory programs,including investigation of moisture,temperature,stress–strain relation,and microstructure to show the effect of curing humidity on the CPB behaviors.The results obtained indicate that ambient humidity can have a dramatic effect on CPB in terms of its macro performance of internal relative humidity,temperature and strength,as well as the micro expression.Typical examples of these effects on CPB include an increase in curing humidity,which favors binder hydration,and then an increase in hydration materials,temperature and peak stress in the CPB.The results obtained will lead to a better understanding of CPB’s responses to various environmental conditions.
文摘BACKGROUND Gastric cancer(GC)is a heavy burden in China.Nutritional support for GC patients is closely related to postoperative rehabilitation.However,the role of early oral feeding after laparoscopic radical total gastrectomy in GC patients is unclear and high-quality research evidence is scarce.AIM To prospectively explore the safety,feasibility and short-term clinical outcomes of early oral feeding after laparoscopic radical total gastrectomy for GC patients.METHODS This study was a prospective cohort study conducted between January 2018 and December 2019 based in a high-volume tertiary hospital in China.A total of 206 patients who underwent laparoscopic radical total gastrectomy for GC were enrolled.Of which,105 patients were given early oral feeding(EOF group)after surgery,and the other 101 patients were given the traditional feeding strategy(control group)after surgery.Perioperative clinical data were recorded and analyzed.The primary endpoints were gastrointestinal function recovery time and postoperative complications,and the secondary endpoints were postoperative nutritional status,length of hospital stay and expenses,etc.RESULTS Compared with the control group,patients in the EOF group had a significantly shorter postoperative first exhaust time(2.48±1.17 d vs 3.37±1.42 d,P=0.001)and first defecation time(3.83±2.41 d vs 5.32±2.70 d,P=0.004).In addition,the EOF group had a significant shorter postoperative hospitalization duration(5.85±1.53 d vs 7.71±1.56 d,P<0.001)and lower postoperative hospitalization expenses(16.60±5.10 K¥vs 21.00±7.50 K¥,P=0.014).On the 5th day after surgery,serum prealbumin level(214.52±22.47 mg/L vs 204.17±20.62 mg/L,P=0.018),serum gastrin level(246.30±57.10 ng/L vs 223.60±55.70 ng/L,P=0.001)and serum motilin level(424.60±68.30 ng/L vs 409.30±61.70 ng/L,P=0.002)were higher in the EOF group.However,there was no significant difference in the incidence of total postoperative complications between the two groups(P=0.507).CONCLUSION Early oral feeding after laparoscopic radical total gastrectomy can promote the recovery of gastrointestinal function,improve postoperative nutritional status,reduce length of hospital stay and expenses while not increasing the incidence of related complications,which indicates its safety,feasibility and potential benefits for gastric cancer patients.
基金Supported by the National Natural Science Foundation of China[21276090]
文摘Al_2O_3/R141 b + Span-80 nanorefrigerant for 0.05 wt.% to 0.4 wt.% is prepared by ultrasonic vibration to investigate the influence of nanoparticle concentrations on flow boiling heat transfer of Al_2O_3/R141 b + Span-80 in micro heat exchanger by direct metal laser sintering. Experimental results show that nanoparticle concentrations have significantly impact on heat transfer coefficients by homogeneity test of variances according to mathematical statistics. The heat transfer performance of Al_2O_3/R141 b+ Span-80 nanorefrigerant is enhanced after adding nanoparticles in the pure refrigerant R141 b. The heat transfer coefficients of 0.05 wt.%, 0.1 wt.%, 0.2 wt.%, 0.3 wt.%and 0.4 wt.% Al_2O_3/R141 b + Span-80 nanorefrigerant respectively increase by 55.0%, 72.0%, 53.0%, 42.3% and 39.9% compared with the pure refrigerant R141 b. The particle fluxes from viscosity gradient, non-uniform shear rate and Brownian motion cause particles to migrate in fluid especially in the process of flow boiling. This migration motion enhances heat transfer between nanoparticles and fluid. Therefore, the heat transfer performance of nanofluid is enhanced. It is important to note that the heat transfer coefficients nonlinearly increase with nanoparticle concentrations increasing. The heat transfer coefficients reach its maximum value at the mass concentration of 0.1% and then it decreases slightly. There exists an optimal mass concentration corresponding to the best heat transfer enhancement. The reason for the above phenomenon is attributed to nanoparticles deposition on the minichannel wall by Scanning Electron Microscopy observation. The channel surface wettability increases during the flow boiling experiment in the mass concentration range from 0.2 wt.% to 0.4 wt.%. The channel surface with wettability increasing needs more energy to produce a bubble. Therefore, the heat transfer coefficients decrease with nanoparticle concentrations in the range from 0.2 wt.% to 0.4 wt.%. In addition, a new correlation has been proposed by fitting the experimental data considering the influence of mass concentrations on the heat transfer performance. The new correlation can effectively predict the heat transfer coefficient.
基金the National Natural Science Foundation of China(Nos.51605276 and51905333)Shanghai Sailing Program(No.19YF1418100)+2 种基金Shanghai Science and Technology Committee Innovation Grant(Nos.17JC1400600 and 17JC1400601)Karamay Science and Technology Major Project(No.2018ZD002B)Aid for Xinjiang Science and Technology Project(No2019E0235)。
文摘Cold metal transfer plus pulse(C+P)arc was applied in the additive manufacturing of 4043 Al alloy parts.Parameters in the manufacturing of the parts were investigated.The properties and microstructure of the parts were also characterized.Experimental results showed that welding at a speed of 8 mm/s and a wire feeding speed of 4.0 m/min was suitable to manufacture thin-walled parts,and the reciprocating scanning method could be adopted to manufacture thick-walled parts.The thin-walled parts of the C+P mode had fewer pores than those of the cold metal transfer(CMT)mode.The thin-and thick-walled parts of the C+P mode showed maximum tensile strengths of 172 and 178 MPa,respectively.Hardness decreased at the interface and in the coarse dendrite and increased in the refined grain area.
文摘Magnoline(1),a new isoquinoline derivative,was isolated from the leaves of Magnolia sieboldii K.Koch(Magnoliaceae).Its structure was elucidated on the basis of spectral analysis including 1D,2D NMR and HR-TOF-MS.
基金The financial supports from The National Natural Science Foundation of China(20163002)Natural Science Foundation of Yunnan Province(2003E0005Z)are gratefully acknowledged.
文摘A stable 3DOM CeO2 with well-defined inverse opal microstructure and crystalline walls structure has been successfully synthesized by application of three-dimensional order PMMA beads as templates. Structural feature of products was characterized by using SEM, DTA-TG, XRD.
基金supported by the National Natural Science Foundation of China (No 30771946)
文摘This study aimed to evaluate the effects of baicalin on ultraviolet radiation B (UVB)-mediated microRNA (miRNA) expression in mouse skin.We determined miRNA expression profiles in UVB irradiated mice,baicalin treated irradiated mice,and untreated mice,and conducted TargetScan and Gene Ontology analyses to predict miRNA targets.Three miRNAs (mmu-miR-125a-5p,mmu-miR-146a,and mmu-miR-141) were downregulated and another three (mmu-miR-188-5p,mmu-miR-223 and mmu-miR-22) were upregulated in UVB irradiated mice compared with untreated mice.Additionally,these miRNAs were predicted to be related to photocarcinogenesis,hypomethylation and apoptosis.Three miRNAs (mmu-miR-378,mmu-miR-199a-3p and mmu-miR-181b) were downregulated and one (mmu-miR-23a) was upregulated in baicalin treated mice compared with UVB irradiated mice,and they were predicted to be related to DNA repair signaling pathway.These deregulated miRNAs are potentially involved in the pathogenesis of photodamage,and may aid treatment and prevention of UVB-induced dermatoses.
基金the National Key Research & Development Program of China (2017YFC0804208)the National Nature Science Foundation of China (Grant Nos. 51774122. 5177404& 51504122)Scientific Research Foundation of State Key Lab. of Coal Mine Disaster Dynamics and Control (2011DA105287-FW 201605).
文摘Rock burst is a catastrophic dynamic disaster caused by sudden failure and instability of coal, loading paths play an important role in the failure of coal, the coal failure process is associated with charge exception infonnation. Hence, violent coal failure mechanics and time-frequency domain distribution of charge signal such as rock burst under different loading paths should be studied in-depth. In this paper, grade and cyclic loading test were carried out for coal with impact tendency samples produced by blocks cored from 800 depth in Xiaoqing coal mine of the Tiefa coal group in northeast China. Theory discussion was carried out for the result of stress and strain, frequency-spectra analysis was conducted for the wavelet charge data, figures showing the evolution mechanism of mechanical properties and the relationship of timefrequency domain amplitude of charge signals in coal with different loading paths and stage were obtained. The failure process and characteristics of coal under different loading paths were summarized. It found that the loading path changed the manner of energy accelerate-release, there were more plastic strain generation in coal under cyclic loading than that under grade loading, the former was more likely to cause greater damage and failure, then the strength of coal under cyclic loading is generally lower than that under grade loading, an energy conversion mechanical model of stress, damage and deformation was developed and explained the effect of the loading path. Charge signal was primarily distributed in the strengthening and peak stages, where there was a high amplitude pulse at each stress drop. The charge pulse was a type of low frequency signal with a primary frequency distribution range of 1 -100Hz. Discussion on the charge generating mechanism from the perspective of friction slip, it demonstrated that the charge obtained during the coal failure process directly to stress loaded on and damage, the result verified it better. We propose that the research results in this study could be efficiently applied to daily mining activities, to provide an early warning and effectively avoid rock burst disaster.
