Sliding electrical contact is a common phenomenon in electrical equipment and affects performance.In this paper,the mechanism of sliding electric contact pair transition and the moment when transition occurs are inves...Sliding electrical contact is a common phenomenon in electrical equipment and affects performance.In this paper,the mechanism of sliding electric contact pair transition and the moment when transition occurs are investigated using the railgun as an example.Transition is the phenomenon where the contact between the armature and rails changes from solid-solid contact to solid-arc-solid contact.In this paper,the finite element-boundary element coupling method(FE-BE method)is used to simulate the process of armature movement.Then,the force,thermal,and electrical parameters on the armature/rail contact surface are analyzed to explore the development of contact separation.Finally,the occurrence of the transition is judged based on the Townsend discharge model(improved by Rogowski).A Small-caliber railgun firing test was carried out to validate the methodology presented in this paper.Results show that the drop edge of the current will result in the armature/rail not being able to make full contact,and the contact gap may break down,leading to a sharp increase in contact resistance and deterioration of railgun performance.Judging the occurrence of transition based on the evolution of the contact gap and the Townsend discharge model is reliable.The research provides new ideas for studying railgun transition and sliding electric contact failure.展开更多
The anchoring eccentricity of the bolt and cable bolt is a common problem in geotechnical support engineering and affects the ability of the bolt and cable bolt to control the rock mass to a certain extent.This paper ...The anchoring eccentricity of the bolt and cable bolt is a common problem in geotechnical support engineering and affects the ability of the bolt and cable bolt to control the rock mass to a certain extent.This paper reports on numerical simulation and laboratory experiments conducted to clarify the effect of eccentricity on the anchoring quality of the bolt and cable bolt,and to establish an effective solution strategy.The results reveal that the anchoring eccentricity causes unbalanced stress distribution and the uncoordinated deformation of the resin layer,which results in higher stress and greater deformation of the resin layer at the near side of the rod body.Additionally,as the degree of anchoring eccentricity increases,the effect becomes more significant,and the resin layer of the anchoring system becomes more likely to undergo preferential failure locally,which weakens the load-bearing performance of the anchoring system.This paper develops an innovative bolt anchoring rectifying device(B-ARD)and cable bolt anchoring rectifying device(C-ARD)on the basis of the structural characteristics of the bolt and cable bolt to better ensure the anchoring effect of them.The working effects of these two devices were verified in detailed experiments and analysis.The experimental results show that the anchoring rectifying devices(ARD)improve and ensure the anchoring concentricity of the bolt and cable bolt,which will help improve the supporting performance of them.The paper provides a convenient and effective method for improving the anchoring concentricity of the bolt and cable bolt,and provides a concept and reference for technical research on improving the effect of roof bolting.展开更多
Structural deterioration in the roof in an underground mine can easily cause roof fall,and deterioration is difficult to detect.When drilling holes for roof bolts,there is a relationship between the vibration of the d...Structural deterioration in the roof in an underground mine can easily cause roof fall,and deterioration is difficult to detect.When drilling holes for roof bolts,there is a relationship between the vibration of the drill rod and the properties of the rock being drilled.This paper analyzes transverse,longitudinal,and torsional vibrations in the drill rod by using vibration theory.Characteristic indexes for three kinds of vibration are determined.Using the finite element analysis software ABAQUS,a model for drill rod vibration during the drilling of roof bolt holes was established based on the geological and mining conditions in the Guyuan Coal Mine,northern China.Results from the model determined that the transverse and the longitudinal vibration decrease as the rock hardness decreases.In descending order,sandstone,sandy mudstone,mudstone,and weak interbeds cause progressively less vibration when being drilled.The ranking for strata that cause decreasing torsional vibration is slightly different,being,in descending order,mudstone,sandstone,sandy mudstone,and weak interbeds.These results provide a theoretical basis for predicting dangerous roof conditions and the presence of weak interbeds to allow for adjusting bolt support schemes.展开更多
Three hundred and twenty endophytic actinobacterial strains were isolated from psammophytes collected from Taklamakan Desert and identified. Among them, three strains already had been identified as new species of two ...Three hundred and twenty endophytic actinobacterial strains were isolated from psammophytes collected from Taklamakan Desert and identified. Among them, three strains already had been identified as new species of two genera and sixteen isolates showed relatively low 16 S rRNA similarities < 98.6% to validly described species. Seventy-five of the isolates were selected as representative strains to screen antibacterial activity and mechanism. Forty-seven strains showed antagonistic activity against at least one of the indicator bacteria. Two Streptomyces strains produced bioactive compounds inducing DNA damage, and two Streptomyces strains produced bioactive compounds with inhibitory activity on protein biosynthesis. Notably, the strain Streptomyces sp. 8P21H-1 that demonstrated both strong antibacterial activity and inhibitory activity on protein biosynthesis was prioritized for exploring new antibiotics.Under the strategy of integrating genetics-based discovery program and MS/MS-based molecular networking, two new streptogramin-type antibiotics, i.e., acetyl-griseoviridin and desulphurizing griseoviridin, along with known griseoviridin, were isolated from the culture broth of strain 8P21H-1. Their chemical structures were determined by HR-MS, and 1D and 2D NMR. Desulphurizing griseoviridin and griseoviridin exhibited antibacterial activities by inhibiting translation.展开更多
Grouting is an important method to reinforce soft coal roadway,and the presence of primary cracks in the coal body has an important influence on the grouting effect.With the discrete element simulation method,the grou...Grouting is an important method to reinforce soft coal roadway,and the presence of primary cracks in the coal body has an important influence on the grouting effect.With the discrete element simulation method,the grouting process of the soft coal seam was simulated.The mechanism of primary cracks on grouting was revealed,while the influence of fracture characteristics and grouting pressure on the grouting effect was analyzed.The results demonstrated that grouting in the soft coal seam involves the stages of seepage,rapid splitting,slow splitting,and stability.Due to the presence of primary cracks,the grouting diffusion radius increased significantly.Under the slurry pressure,the tensile stress concentration was formed at the crack tip,and the slurry split the coal once the splitting pressure was reached.In addition,the distribution characteristics of fractures are found to have a great influence on the grouting effect.It is observed that smaller fracture spacing is associated with a larger slurry diffusion radius and thus easier penetration of the primary crack tips.The fracture angle affects the direction of fracture propagation.The secondary fracture formed by splitting is a tensile fracture,which is more likely to extend along the direction parallel to the maximum principal stress.Overall,these simulation results have guiding significance for the setting of reasonable spacing of grouting holes in the practice of grouting engineering.展开更多
In this paper, a novel solution mitigating the radio blackout problem is proposed, which improves existing traveling magnetic field(TMF)-based methods. The most significant advance lies in replacing the external injec...In this paper, a novel solution mitigating the radio blackout problem is proposed, which improves existing traveling magnetic field(TMF)-based methods. The most significant advance lies in replacing the external injection with self-induced current, which does not require electrodes. The improved analytical model is derived to evaluate the electron density reduction taking into consideration the self-induced current for various TMF velocities. The plasma reduction performance is analyzed for several conditions including the total absence of injected current. The results show that the velocity may be used to trade off the injected current and, when sufficiently large, eliminates the need for an injected current while mitigating radio blackout. The effectiveness of this solution to the blackout problem is demonstrated in commonly used aerospace communication bands. With a field strength of less than 0.15 T, increasing the velocity from40 m s^-1 to 3100 m s^-1 is all that is required to obviate the need for an injected current. Moreover,typical reduction ratios for electronic density tolerance(2, 1.9, 1.75 and 3 times for the L-, S-, Cand X-bands, respectively, at an altitude of 40 km) remain unchanged. Increasing the velocity of the TMF is much easier than injecting current via a metal electrode into a high-temperature flow field. The TMF method appears practical in regard to possible future applications.展开更多
Selenium(Se)plays an important role in the development and treatment of lung cancer,yet its specific mechanisms remain elusive.Lower Se level in serum was noted in lung cancer patients compared to normal controls.Ther...Selenium(Se)plays an important role in the development and treatment of lung cancer,yet its specific mechanisms remain elusive.Lower Se level in serum was noted in lung cancer patients compared to normal controls.Therefore,developing effective therapeutic adjuvants containing Se might benefit the treatment of lung cancer patients.This study aimed to investigate the association between Se and the chemotherapeutic efficacy of lung cancer.Lentinan-modified selenium nanoparticles(LET-Se NPs)were created to develop and verify the effectiveness of Se containing adjuvant applied with pemetrexed on lung cancer cells.A synergistic effect was observed between LET-Se NPs and pemetrexed in vitro.The combination of LET-Se NPs and pemetrexed could induce reactive oxygen species overproduction,mitochondrial dysfunction and DNA damage,ultimately leading to cancer cell apoptosis.It is implied that LET-Se NPs might be a promising sensitizer to pemetrexed chemotherapy and could potentially enhance chemotherapy efficiency in non-small cell lung cancer.展开更多
To explore pharmaceutical actinobacteria from salty environments in Siberia,8 soil samples were collected from different depths of Gudzhirganskoe saline lake,the Republic of Buryatia,Russia.Totally,635 actinobacterial...To explore pharmaceutical actinobacteria from salty environments in Siberia,8 soil samples were collected from different depths of Gudzhirganskoe saline lake,the Republic of Buryatia,Russia.Totally,635 actinobacterial strains affiliated with 21 genera in 12 families of 7 orders were obtained by culture-dependent approaches.The predominant genus was Streptomyces(74.5%),followed by Microbacterium(4.9%),Agromyces(3.5%),Nocardiopsis(3.0%),and Kitasatospora(2.5%).Seven strains showed relatively low 16 S rRNA similarities(<98.65%)with validly described species.Seventy-seven strains were selected as representatives to evaluate their antimicrobial activities and underlying mechanisms by paper-disk diffusion method and a double fluorescent protein reporter system(pDualrep 2),respectively.Streptomyces sp.S 6 b 3-1 was highlighted due to its strong inhibitory activities against Gram-positive bacteria and underlying antibacterial mechanism by inducing the SOS response in the reporter system.LG-1,(R)-6-[1-(benzoyloxy)ethyl]-phenazine-1-carboxylic acid,an analogue of saphenamycin was finally isolated from the culture broth of Streptomyces strain.This study preliminarily explored the actinobacterial diversity of soil samples collected in the highly alkaline and saline lake Gudzhirganskoe by culture-dependent approach and their capacity to produce antibiotics for the first time,which revealed that it deserves to make more efforts to discover new actinobacterial species and potential new antibiotics from the saline lake in Eastern Siberia.展开更多
文摘Sliding electrical contact is a common phenomenon in electrical equipment and affects performance.In this paper,the mechanism of sliding electric contact pair transition and the moment when transition occurs are investigated using the railgun as an example.Transition is the phenomenon where the contact between the armature and rails changes from solid-solid contact to solid-arc-solid contact.In this paper,the finite element-boundary element coupling method(FE-BE method)is used to simulate the process of armature movement.Then,the force,thermal,and electrical parameters on the armature/rail contact surface are analyzed to explore the development of contact separation.Finally,the occurrence of the transition is judged based on the Townsend discharge model(improved by Rogowski).A Small-caliber railgun firing test was carried out to validate the methodology presented in this paper.Results show that the drop edge of the current will result in the armature/rail not being able to make full contact,and the contact gap may break down,leading to a sharp increase in contact resistance and deterioration of railgun performance.Judging the occurrence of transition based on the evolution of the contact gap and the Townsend discharge model is reliable.The research provides new ideas for studying railgun transition and sliding electric contact failure.
基金This study was supported by the National Natural Science Foundation of China(No.52074102)Foundation for Distinguished Young Talents in Higher Education of Henan(No.212300410006)+1 种基金Foundation for the Science and Technology Innovation Talents Project of Universities in Henan(No.22HASTIT010)Special Funds for Fundamental Scientific Research Expenses of Universities in Henan(No.NSFRF210202).
文摘The anchoring eccentricity of the bolt and cable bolt is a common problem in geotechnical support engineering and affects the ability of the bolt and cable bolt to control the rock mass to a certain extent.This paper reports on numerical simulation and laboratory experiments conducted to clarify the effect of eccentricity on the anchoring quality of the bolt and cable bolt,and to establish an effective solution strategy.The results reveal that the anchoring eccentricity causes unbalanced stress distribution and the uncoordinated deformation of the resin layer,which results in higher stress and greater deformation of the resin layer at the near side of the rod body.Additionally,as the degree of anchoring eccentricity increases,the effect becomes more significant,and the resin layer of the anchoring system becomes more likely to undergo preferential failure locally,which weakens the load-bearing performance of the anchoring system.This paper develops an innovative bolt anchoring rectifying device(B-ARD)and cable bolt anchoring rectifying device(C-ARD)on the basis of the structural characteristics of the bolt and cable bolt to better ensure the anchoring effect of them.The working effects of these two devices were verified in detailed experiments and analysis.The experimental results show that the anchoring rectifying devices(ARD)improve and ensure the anchoring concentricity of the bolt and cable bolt,which will help improve the supporting performance of them.The paper provides a convenient and effective method for improving the anchoring concentricity of the bolt and cable bolt,and provides a concept and reference for technical research on improving the effect of roof bolting.
基金the National Natural Science Foundation of China(Nos.51104055,51274087,51604094 and 51674098)
文摘Structural deterioration in the roof in an underground mine can easily cause roof fall,and deterioration is difficult to detect.When drilling holes for roof bolts,there is a relationship between the vibration of the drill rod and the properties of the rock being drilled.This paper analyzes transverse,longitudinal,and torsional vibrations in the drill rod by using vibration theory.Characteristic indexes for three kinds of vibration are determined.Using the finite element analysis software ABAQUS,a model for drill rod vibration during the drilling of roof bolt holes was established based on the geological and mining conditions in the Guyuan Coal Mine,northern China.Results from the model determined that the transverse and the longitudinal vibration decrease as the rock hardness decreases.In descending order,sandstone,sandy mudstone,mudstone,and weak interbeds cause progressively less vibration when being drilled.The ranking for strata that cause decreasing torsional vibration is slightly different,being,in descending order,mudstone,sandstone,sandy mudstone,and weak interbeds.These results provide a theoretical basis for predicting dangerous roof conditions and the presence of weak interbeds to allow for adjusting bolt support schemes.
基金supported by CAMS Innovation Fund for Medical Sciences (Grant Nos. CAMS 2017-I2M-B&R-08 and 2017I2M-1-012)the PUMC Doctoral Innovation Fund Project (Grant No. 2018-1007-16)+2 种基金the Drug Innovation Major Project of China (Grant No. 2018ZX09711001-007-002)the Russian Foundation for Basic Research (Grant No. 20-54-53014)the National Natural Science Foundation of China (Grant No. 82011530051)。
文摘Three hundred and twenty endophytic actinobacterial strains were isolated from psammophytes collected from Taklamakan Desert and identified. Among them, three strains already had been identified as new species of two genera and sixteen isolates showed relatively low 16 S rRNA similarities < 98.6% to validly described species. Seventy-five of the isolates were selected as representative strains to screen antibacterial activity and mechanism. Forty-seven strains showed antagonistic activity against at least one of the indicator bacteria. Two Streptomyces strains produced bioactive compounds inducing DNA damage, and two Streptomyces strains produced bioactive compounds with inhibitory activity on protein biosynthesis. Notably, the strain Streptomyces sp. 8P21H-1 that demonstrated both strong antibacterial activity and inhibitory activity on protein biosynthesis was prioritized for exploring new antibiotics.Under the strategy of integrating genetics-based discovery program and MS/MS-based molecular networking, two new streptogramin-type antibiotics, i.e., acetyl-griseoviridin and desulphurizing griseoviridin, along with known griseoviridin, were isolated from the culture broth of strain 8P21H-1. Their chemical structures were determined by HR-MS, and 1D and 2D NMR. Desulphurizing griseoviridin and griseoviridin exhibited antibacterial activities by inhibiting translation.
基金The authors acknowledge the financial support provided by the National Natural Science Foundation of China(No.51604094 and 51674098)the Shandong Provincial Natural Science Foundation(No.ZR2020QE118).
文摘Grouting is an important method to reinforce soft coal roadway,and the presence of primary cracks in the coal body has an important influence on the grouting effect.With the discrete element simulation method,the grouting process of the soft coal seam was simulated.The mechanism of primary cracks on grouting was revealed,while the influence of fracture characteristics and grouting pressure on the grouting effect was analyzed.The results demonstrated that grouting in the soft coal seam involves the stages of seepage,rapid splitting,slow splitting,and stability.Due to the presence of primary cracks,the grouting diffusion radius increased significantly.Under the slurry pressure,the tensile stress concentration was formed at the crack tip,and the slurry split the coal once the splitting pressure was reached.In addition,the distribution characteristics of fractures are found to have a great influence on the grouting effect.It is observed that smaller fracture spacing is associated with a larger slurry diffusion radius and thus easier penetration of the primary crack tips.The fracture angle affects the direction of fracture propagation.The secondary fracture formed by splitting is a tensile fracture,which is more likely to extend along the direction parallel to the maximum principal stress.Overall,these simulation results have guiding significance for the setting of reasonable spacing of grouting holes in the practice of grouting engineering.
基金supported by National Natural Science Foundation of China(Nos.61771370,61701381,and 11704296)。
文摘In this paper, a novel solution mitigating the radio blackout problem is proposed, which improves existing traveling magnetic field(TMF)-based methods. The most significant advance lies in replacing the external injection with self-induced current, which does not require electrodes. The improved analytical model is derived to evaluate the electron density reduction taking into consideration the self-induced current for various TMF velocities. The plasma reduction performance is analyzed for several conditions including the total absence of injected current. The results show that the velocity may be used to trade off the injected current and, when sufficiently large, eliminates the need for an injected current while mitigating radio blackout. The effectiveness of this solution to the blackout problem is demonstrated in commonly used aerospace communication bands. With a field strength of less than 0.15 T, increasing the velocity from40 m s^-1 to 3100 m s^-1 is all that is required to obviate the need for an injected current. Moreover,typical reduction ratios for electronic density tolerance(2, 1.9, 1.75 and 3 times for the L-, S-, Cand X-bands, respectively, at an altitude of 40 km) remain unchanged. Increasing the velocity of the TMF is much easier than injecting current via a metal electrode into a high-temperature flow field. The TMF method appears practical in regard to possible future applications.
基金supported by National Natural Science Foundation for Distinguished Young Scholars(No.82225025)National Natural Science Foundation of China(Nos.21877049,32171296)。
文摘Selenium(Se)plays an important role in the development and treatment of lung cancer,yet its specific mechanisms remain elusive.Lower Se level in serum was noted in lung cancer patients compared to normal controls.Therefore,developing effective therapeutic adjuvants containing Se might benefit the treatment of lung cancer patients.This study aimed to investigate the association between Se and the chemotherapeutic efficacy of lung cancer.Lentinan-modified selenium nanoparticles(LET-Se NPs)were created to develop and verify the effectiveness of Se containing adjuvant applied with pemetrexed on lung cancer cells.A synergistic effect was observed between LET-Se NPs and pemetrexed in vitro.The combination of LET-Se NPs and pemetrexed could induce reactive oxygen species overproduction,mitochondrial dysfunction and DNA damage,ultimately leading to cancer cell apoptosis.It is implied that LET-Se NPs might be a promising sensitizer to pemetrexed chemotherapy and could potentially enhance chemotherapy efficiency in non-small cell lung cancer.
基金Supported by the CAMS Innovation Fund for Medical Sciences(No.CIFMS 2021-I 2 M-1-028)the Beijing Natural Science Foundation(No.7222256)+5 种基金the National Natural Science Foundation of China(No.82011530051)the Kunlun Talented People,High-end Innovation and Entrepreneurship talents Plan,Qinghai Province,China,for Chenghang SUN,the Talent Training Project of Basic Research Fund of Heilongjiang Department of Education Item to Chunmei XUE(No.2020-KYYWF-0238)the Sino-Hungarian Bilateral S&T Cooperation Projects from 2019 to 2020(Chinese Project:8-11)partly supported by the Russian Foundation for Basic Research(Nos.NCFS-RFBR 20-54-53014,18-44-030021 r_а)the Russian Science Foundation(No.20-74-10031)partially within the framework of the State Assignment(No.121030100229-1)for Institute of General and Experimental Biology,Siberian Branch,Russian Academy of Sciences。
文摘To explore pharmaceutical actinobacteria from salty environments in Siberia,8 soil samples were collected from different depths of Gudzhirganskoe saline lake,the Republic of Buryatia,Russia.Totally,635 actinobacterial strains affiliated with 21 genera in 12 families of 7 orders were obtained by culture-dependent approaches.The predominant genus was Streptomyces(74.5%),followed by Microbacterium(4.9%),Agromyces(3.5%),Nocardiopsis(3.0%),and Kitasatospora(2.5%).Seven strains showed relatively low 16 S rRNA similarities(<98.65%)with validly described species.Seventy-seven strains were selected as representatives to evaluate their antimicrobial activities and underlying mechanisms by paper-disk diffusion method and a double fluorescent protein reporter system(pDualrep 2),respectively.Streptomyces sp.S 6 b 3-1 was highlighted due to its strong inhibitory activities against Gram-positive bacteria and underlying antibacterial mechanism by inducing the SOS response in the reporter system.LG-1,(R)-6-[1-(benzoyloxy)ethyl]-phenazine-1-carboxylic acid,an analogue of saphenamycin was finally isolated from the culture broth of Streptomyces strain.This study preliminarily explored the actinobacterial diversity of soil samples collected in the highly alkaline and saline lake Gudzhirganskoe by culture-dependent approach and their capacity to produce antibiotics for the first time,which revealed that it deserves to make more efforts to discover new actinobacterial species and potential new antibiotics from the saline lake in Eastern Siberia.
