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Dynamic mechanical characteristics of post-peak sandstone under three-dimensional cyclic impact
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作者 ZHANG Jun-wen ZHANG Yang +7 位作者 LI Shi-fang SONG Zhi-xiang DONG Xu-kai WU Shao-kang FAN Wen-bing ZHOU Yan SANG Pei-miao LI Ning 《Journal of Central South University》 2025年第8期2958-2978,共21页
At present,the surrounding rock of the deep mine roadway is prone to post-peak stress under the action of high stress,and secondary rock burst disaster is prone to occur under complex stress disturbance.According to i... At present,the surrounding rock of the deep mine roadway is prone to post-peak stress under the action of high stress,and secondary rock burst disaster is prone to occur under complex stress disturbance.According to incomplete statistics,as of 2023,80%of coal mine rock bursts accidents in China occur in mining roadway.In view of this phenomenon,the cyclic impact test of post-peak sandstone is designed,focusing on the post-peak stress state of sandstone,and exploring the post-peak dynamic response of sandstone.The post-peak sandstone specimens were prepared by a uniaxial compressor,and then cyclic impact tests were carried out on the post-peak sandstone under different coaxial pressure conditions by an improved separated Hopkinson equipment.The results show that:1)The number of impact times required for sandstone failure after peak decreased with the increase of axial pressure,indicating that the impact tendency of sandstone after peak decreased under lower axial pressure.On the contrary,the post-peak sandstone had strong impact tendency under higher axial pressure;2)The higher the axial pressure,the lower the dynamic strength of the post-peak sandstone,indicating that the axial pressure promoted the failure process of the post peak sandstone;3)It was a nonlinear evolution of a quadratic polynomial function between the dissipation-energy release rate and axial pressure;4)Shear failure occurred mainly in post-peak impact sandstone with the increased axial pressure,and the composite failure of intergranular failure and transgranular failure changed to single intergranular failure at the microscopic level.The research shows that when the roadway surrounding rock was in the post-peak stress state,reducing the static stress was the key to prevent the secondary ground pressure disaster.The research results provide a theoretical basis for the prevention and control of roadway rock burst disaster under high ground stress environment,and promote the research and exploration of post-peak mechanical properties of coal and rock. 展开更多
关键词 post-peak impact sandstone 3D cyclic impact dynamic response energy dissipation fracture mechanism
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Effect of post-weld heat treatment on microstructure and mechanical properties of welded joints of 6061-T6 aluminum alloy 被引量:14
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作者 Jie YI Guan WANG +2 位作者 Shi-kang LI Zhi-wen LIU Yan-li GONG 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2019年第10期2035-2046,共12页
6061 aluminum alloy T-joints were welded by double-pulsed MIG welding process. Then, the post-weld heat treatment was performed on the welded T-joints. The weld microstructure under different aging temperature and tim... 6061 aluminum alloy T-joints were welded by double-pulsed MIG welding process. Then, the post-weld heat treatment was performed on the welded T-joints. The weld microstructure under different aging temperature and time was investigated by transmission electron microscopy and scanning electron microscopy. The mechanical properties were examined by hardness test and tensile test. The results showed that the micro-hardness was sensitive to heat treatment temperature and time. Increasing temperature was beneficial to the shortening of peak aging time. There were a large number of dislocations and few precipitates in the welded joints. With the increase of post-weld heat treatment temperature and time, the density of dislocation decreased. Meanwhile, the strengthening phase precipitated and grew up gradually. When the post-weld heat treatment temperature increased up to 200℃, large Q' phases were observed. And they were responsible for the peak value of the micro-hardness in the welded joints. 展开更多
关键词 6061 aluminum alloy double-pulsed MIG welding post-weld heat treatment microstructure evolution mechanical property
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Numerical analysis of reasons for the CO distribution in an opposite-wall-firing furnace
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作者 Xiao-qiang XIE Jian-guo YANG +3 位作者 Chao-yang ZHU Chuan-huai LIU Hong ZHAO Zhi-hua WANG 《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》 SCIE EI CAS CSCD 2020年第3期193-208,共16页
In practical operations,the carbon monoxide(CO)distribution in an opposite-wall-firing furnace(OWFF)is characterized by a high concentration near the side walls and a low concentration in the center,accompanied by a s... In practical operations,the carbon monoxide(CO)distribution in an opposite-wall-firing furnace(OWFF)is characterized by a high concentration near the side walls and a low concentration in the center,accompanied by a series of combustionrelated issues.To find the reasons for the CO distribution,a numerical study was conducted on a 660 MWe OWFF.The CO concentration profiles,distribution coefficients of coal and air,mixing coefficients,and the aerodynamic characteristics were extracted for analysis.The CO distribution within the furnace greatly depends on the mixing of coal and air.A mismatch between the aerodynamic behaviors of coal and air causes the non-uniform distribution of CO.Taking into consideration that distinctive flow patterns exist within the different regions,the formation mechanisms of the CO distribution can be divided into two components:(1)In the burner region,the collision of opposite flows leads to the migration of gas and particles toward the side wall which,together with the vortexes formed at furnace corners,is responsible for unburned particles concentrated and oxygenized from the furnace center to the side wall.Thus,high CO concentrations appear in these areas.(2)As the over-fire air(OFA)jet is injected into the furnace,it occupies the central region of furnace and pushes the gas from the burner region outward to the side wall,which is disadvantageous for the mixing effect in the side wall region.As a consequence,a U-shaped distribution of CO concentration is formed.Our results contribute to a theoretical basis for facilitating the control of variation in CO concentration within the furnace. 展开更多
关键词 Opposite-wall-firing furnace(OWFF) Carbon monoxide(CO)distribution Distributions of coal and air Gas/particle flow Corner vortex Over-fire air(OFA)
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Experimental Investigation on Low-Velocity Impact Response and Residual Compressive Bearing Capacity of Composite Stringers
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作者 CHEN Fang YAO Weixing WU Fuqiang 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI CSCD 2020年第4期655-662,共8页
Three types of composite stringers were impacted from two different directions.Relationships between impact energy and visible defect length were found.The critical impact energy corresponding to barely visible impact... Three types of composite stringers were impacted from two different directions.Relationships between impact energy and visible defect length were found.The critical impact energy corresponding to barely visible impact damage(BVID)of each stringer was determined.Specimens with BVID were then compressed to obtain the residual strength.Experimental results showed that for all types of stringers,the critical energy of in-plane impact is always much lower than out-plane ones.In-plane impact causes much more decrement of stringers'bearing capacity than outplane impact.For both impact directions,I-stringers own the highest defect detectability,T-stringers come second.Meanwhile,I-stringers own the better residual strength ratio than I-stringers and I-stringers.Synthetic considering impact defect detectability and residual bearing capacity after impact,T-stringers own the best compression-afterimpact(CAI)behaviors. 展开更多
关键词 composite stringer low-velocity impact defect compression after impact residual bearing capacity
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以太网中冲突问题探析
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作者 袁芳文 王超杰 《科技信息》 2006年第01X期14-14,10,共2页
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SEVERAL CRYPTOGRAPHIC APPLICATIONS OF ∑-PROTOCOL
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作者 Chunming TANG Zheng-an YAO 《Journal of Systems Science & Complexity》 SCIE EI CSCD 2009年第2期260-279,共20页
∑-protocol has been proved to be a very powerful cryptographic tool and widely used in nnmerous important cryptographic applications. In this paper, the authors make use of ∑-protocol as a main tool to resolve the f... ∑-protocol has been proved to be a very powerful cryptographic tool and widely used in nnmerous important cryptographic applications. In this paper, the authors make use of ∑-protocol as a main tool to resolve the following difficult problems 1-3 and to construct three ettlcient cryptographic protocols 4 6:1) How to construct a protocol for proving a secret integer to be a Blum integer with form PQ, where P, Q are two different primes and both -- 3(mod 4);2) How to construct a protocol for proving a secret polynomial with exact degree t - 1 iil a (t, n)- threshold secret sharing scheme:3) How to construct witness indistinguishable and witness hiding protocol not from zero-knowledge proof;4) A publicly verifiable secret sharing scheme with information-theoretic security;5) A delegateable signature scheme under the existence of one-way permutations;6) Non-interactive universal designated verifier signature schemes. 展开更多
关键词 ∑-protocol Blum integer delegateable signature secret sharing witness hiding protocol witness indistinguishable protocol universal designated verifier signature.
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Carboniferous slab-retreating subduction of backarc oceans:the final large-scale lateral accretion of the southern Central Asian Orogenic Belt 被引量:2
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作者 Hai Zhou Guochun Zhao +6 位作者 Yigui Han Donghai Zhang Meng Wang Xianzhi Pei Narantsetseg Tserendash Qian Zhao Enkh-Orshikh Orsoo 《Science Bulletin》 SCIE EI CSCD 2022年第13期1388-1398,M0004,共12页
During Carboniferous time,tremendous juvenile arc crust was formed in the southern Central Asian Orogenic Belt(CAOB),although its origin remains unclear.Herein,we presented zircon U-Pb-Hf and whole-rock geochemical an... During Carboniferous time,tremendous juvenile arc crust was formed in the southern Central Asian Orogenic Belt(CAOB),although its origin remains unclear.Herein,we presented zircon U-Pb-Hf and whole-rock geochemical and Sr-Nd isotopic data for a suite of volcanic and pyroclastic rocks from the Khan-Bogd area in southern Mongolia.These Carboniferous pyroclastic rocks generally have some early Paleozoic zircons,probably derived from the granitic and sedimentary rocks of the Lake Zone and the Gobi-Altai Zone to the north,indicative of a continental arc nature.In addition,they have a main zircon U-Pb age of ca.370–330 Ma,positive Hf and Nd isotopes,and mafic-intermediate arc affinity,similar to the coeval arc magmatism.Moreover,the pyroclastic rocks of the northern area have more mafic and older volcanic components with depositional time(ca.350–370 Ma;Visean and Bashkirian stages)earlier than that in the southern area(mainly ca.350–315 Ma;Serpukhovian and Bashkirian stages).Combining a preexisting northward subduction supported by the available magnetotelluric data with a slab rollback model of the main oceanic basin of the Paleo-Asian Ocean(PAO)during Carboniferous and Triassic times,we infer that the Carboniferous arc magmatism was probably derived from a backarc ocean triggered by slab rollback.Thus,the juvenile arc volcanism of Mongolia,together with other areas(e.g.,Junggar)in the southern CAOB,represented a significant lateral accretion that terminated after the Carboniferous due to a significant contraction of the PAO. 展开更多
关键词 CARBONIFEROUS Central Asian Orogenic Belt Paleo-Asian Ocean Southern Mongolia Slab retreating
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Feature analysis of LIDAR waveforms from forest canopies 被引量:7
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作者 LIU QingWang LI ZengYuan +3 位作者 CHEN ErXue PANG Yong LI ShiMing TIAN Xin 《Science China Earth Sciences》 SCIE EI CAS 2011年第8期1206-1214,共9页
Airborne light detection and ranging (LIDAR) can detect the three-dimensional structure of forest canopies by transmitting laser pulses and receiving returned waveforms which contain backscatter from branches and leav... Airborne light detection and ranging (LIDAR) can detect the three-dimensional structure of forest canopies by transmitting laser pulses and receiving returned waveforms which contain backscatter from branches and leaves at different heights.We established a solid scatterer model to explain the widened durations found in analyzing the relationship between laser pulses and forest canopies,and obtained the corresponding rule between laser pulse duration and scatterer depth.Based on returned waveform characteristics,scatterers were classified into three types:simple,solid and complex.We developed single-peak derivative and multiple-peak derivative analysis methods to retrieve waveform features and discriminate between scatterer types.Solid scatterer simulations showed that the returned waveforms were widened as scatterer depth increased,and as space between sub-scatterers increased the returned waveforms developed two peaks which subsequently developed into two separate sub-waveforms.There were slight differences between the durations of simulated and measured waveforms.LIDAR waveform data are able to describe the backscatter characteristics of forest canopies,and have potential to improve the estimation accuracy of forest parameters. 展开更多
关键词 remote sensing forest canopy LIDAR waveform feature solid scatterer
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Effect of acupuncture on blood oxygen concentration in brain of rats with post-traumatic stress disorder based on functional near-infrared spectroscopy 被引量:3
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作者 Zhang Yan-feng Han Ya-di +2 位作者 Zhao Zhong-ting Yan Xing-ke Yang Yan-ping(Translator) 《Journal of Acupuncture and Tuina Science》 CSCD 2019年第1期9-15,共7页
Objective: To observe the effect of acupuncture on blood oxygen concentration in the brain of rats with post-traumatic stress disorder (PTSD) based on functional near-infrared spectroscopy (fNIRS), thus to reveal the ... Objective: To observe the effect of acupuncture on blood oxygen concentration in the brain of rats with post-traumatic stress disorder (PTSD) based on functional near-infrared spectroscopy (fNIRS), thus to reveal the mechanisms of acupuncture in intervening the brain function of PTSD rats. Methods: Sixty Sprague-Dawley (SD) rats were randomly divided into a blank group, a model group, a grasping group, a paroxetine group and an acupuncture group, with 12 rats in each group. Except the blank group, rats in the other groups all received incarceration plus electric shock for 7 d to prepare the PTSD animal model. One hour before the stress model was established, rats in each group received the desig nated in tervention: rats in the blank group and the model group did not receive any intervention;rats in the grasping group received grasping and fixation;rats in the paroxetine group received paroxetine hydrochloride solution by intragastric administration;and rats in the acupuncture group received acupuncture. Six-day treatme nt was a course, with 2 courses of treatme nt con ducted for a total of 12 d. After the modeli ng, rats in each treatment group received intervention for 5 dz and the fNIRS system was used to collect and record the changes in the concentrations of oxygenated hemoglobin (HbO2), deoxygenated hemoglobin (d-Hb) and total hemoglobin (t-Hb) of the involved rat's brain regions, and also to assess the brain function. Results: Compared with the blank group, the con centrati on of HbO2 was significa ntly in creased, the concen trati on of d-Hb was significa ntly decreased, and the concen tration of t-Hb was sign ifica ntly in creased in the model group and the graspi ng group after the in tervention, and the differ en ces were statistically significant (all P<0.01). Compared with the model group, the concentrations of HbO2, d-Hb and t-Hb in the grasping group did not change significantly (all P>0.05). Compared with the grasping group, the concentration of HbC^was significantly decreased, the concentration of d-Hb was significantly in creased, and the concen trati on of t-Hb was sign ifica ntly decreased in the paroxeti ne group and the acup un cture group, and the differences were statistically sigrdficant (all P<0.05). There were no significant differences in the concentrations of HbO2, d-Hb and t-Hb between the paroxetine group and the acupuncture group (all P>0.05). Con elusion: Acup un cture can regulate the blood oxyge n conce ntrati on in the brain of PTSD model rats, which may be an important mechanism of acupuncture in intervening the brain function in PTSD rats. 展开更多
关键词 Acupuncture Therapy Point Baihui (GV 20) Point Shenmen (HT 7) Point Neiguan (PC 6) Point Taichong (LR 3) Stress Disorders Post-traumatic Spectroscopy Near-infrared RATS
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Effects of acupuncture on neuro-electrophysiological activities in hippocampal CAI and CA3 areas of rats with post-traumatic stress disorder 被引量:2
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作者 Zhao Zhong-ting Zhao Yi-kun +4 位作者 Zhu Tian-tian Xing Jia-ming Bu Xiao-mei Zhang Yan-feng Yan Xing-ke 《Journal of Acupuncture and Tuina Science》 CSCD 2019年第2期67-73,共7页
Objective: To observe the effects of acupuncture on the characteristics of neuro-electrophysiological activity in hippocampal CAI and CA3 areas of rats with post-traumatic stress disorder (PTSD). Methods: Fifty Spragu... Objective: To observe the effects of acupuncture on the characteristics of neuro-electrophysiological activity in hippocampal CAI and CA3 areas of rats with post-traumatic stress disorder (PTSD). Methods: Fifty Sprague-Dawley (SD) rats were randomly divided into a blank group, a model group, a grasping group, a Western medicine group and an acupuncture group, with 10 rats in each group. Except for the blank group, rats in the other 4 groups all received the combined stress modeling method. Rats in the Western medicine group were intragastrically administrated with paroxetine hydrochloride, those in the acupuncture group received acupuncture intervention, those in the grasping group received grasping fixation, and those in the model group and the blank group did not receive any in terve ntions. After 14 d of in terve ntion, the interspike in terval (ISI) and power spectral den sities (PSD) were an a lyzed and mapped by in vivo multiple channels to record the neuron clusters discharge in the hippocampal CAI and CA3 areas. Results: Compared with the blank group, ISI was proIonged in the CAI and CA3 areas of the model group and the grasping group, and the concentrated PSD distribution area moved down (Pv0.05 or P<0.01). Compared with the grasping group, the ISI of the CAI and CA3 areas in the Western medicine group and the acupuncture group was shortened, and the concentrated PSD distribution area moved up (P<0.05 or P<0.01). The ISI and PSD distributions in the CAI and CA3 areas of the acupuncture group were not statistically different from those in the Western medicine group (both P>0.05). Conclusion: Both acupuncture and paroxetine hydrochloride can significantly regulate the neuro-electrophysiology activity of hippocampal CAI and CA3 areas in PTSD rats, which may be one of the mechanisms of acupuncture intervention to promote PTSD recovery. 展开更多
关键词 Acupuncture Therapy Point Baihui (GV 20) Point Neiguan (PC 6) Point Shenmen (HT 7) Point Taichong (LR 3) Stress Disorders Post-traumatic Electrophysiology RATS
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Effect of liver-soothing and mind-regulating acupuncture on resting-state electroencephalographic signals in rats with post-traumatic stress disorder 被引量:1
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作者 魏玉婷 严兴科 +2 位作者 韩雅迪 张彦峰 杨燕萍 《Journal of Acupuncture and Tuina Science》 CSCD 2018年第5期289-296,共8页
Objective:To observe the effect of liver-soothing and mind-regulating acupuncture method on the resting-state electroencephalography (EEG) in rats with post-traumatic stress disorder (PTSD),and to provide evidence for... Objective:To observe the effect of liver-soothing and mind-regulating acupuncture method on the resting-state electroencephalography (EEG) in rats with post-traumatic stress disorder (PTSD),and to provide evidence for the effect mechanism study and clinical application of acupuncture intervention for PTSD.Methods:Sixty Sprague-Dawley (SD) rats were randomly divided into a blank control group,a model group,a grasping group,a paroxetine group and an acupuncture group,with 12 rats in each group.Except for rats in the blank control group,rats in the other groups were subjected to preparing the PTSD models using 'incarceration plus electric shock' method.After interventions,changes in rat behavior of each group were observed;changes in resting-state EEG were collected and analyzed with multichannel EEG acquisition and analysis system,and image analysis and statistical processing were performed.Results:Compared with the blank control group,the average escape latency in the model group was significantly longer (P<0.05),and the times of crossing the platform and the effective areas were all significantly reduced (P<0.01).Compared with the grasping group,the average escape latencies in the paroxetine group and acupuncture group were significantly shortened (P<0.05),and the times of crossing the platform and the effective areas were all significantly increased (P<0.05).There were no significant differences in the average escape latency,the times of crossing the platform and the effective areas between the acupuncture group and paroxetine group (all P>0.05).Compared with the blank control group,the α-wave power spectrum value in the model group was significantly decreased,and the power spectrum values of β-wave,δ-wave and a-wave were significantly increased (all P<0.01);compared with the grasping group,α-wave power spectrum values in the paroxetine group and acupuncture group were significantly increased (both P<0.01),and the power spectrum values of β-wave,δ-wave and a-wave were decreased significantly (all P<0.01).The power spectrum values of α-wave,β-wave,δ-wave and (e)-wave of rats in the acupuncture group were not significantly different from those in the paroxetine group (all P>0.05).Conclusion:Liver-soothing and mind-regulating acupuncture method can significantly improve the abnormal EEG activity in PTSD rats,which may be one mechanism of liver-soothing and mind-regulating acupuncture method in effectively affecting the brain function in PTSD rats. 展开更多
关键词 Acupuncture Therapy Point Baihui (GV 20) Point Shenmen (HT 7) Point Neiguan (PC 6) Point Taichong (LR 3) Stress Disorders Post-traumatic Electroencephalography RATS
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