The mechanism of cracks propagation and cracks coalescence due to compressive loading of the brittle substances containing pre-existing cracks(flaws)was modeled experimentally using specially made rock-like specimens ...The mechanism of cracks propagation and cracks coalescence due to compressive loading of the brittle substances containing pre-existing cracks(flaws)was modeled experimentally using specially made rock-like specimens from Portland Pozzolana Cement(PPC).The breakage process of the specimens was studied by inserting single and double flaws with different inclination angles at the center and applying uniaxial compressive stress at both ends of the specimen.The first crack was oriented at 50° from the horizontal direction and kept constant throughout the analysis while the orientation of the second crack was changed.It is experimentally observed that the wing cracks are produced at the first stage of loading and start their propagation toward the direction of uniaxial compressive loading.The secondary cracks may also be produced in form of quasi-coplanar and/or oblique cracks in a stable manner.The secondary cracks may eventually continue their propagation in the direction of maximum principle stress.These experimental works were also simulated numerically by a modified higher order displacement discontinuity method and the cracks propagation and cracks coalescence were studied based on Mode I and Mode II stress intensity factors(SIFs).It is concluded that the wing cracks initiation stresses for the specimens change from 11.3 to 14.1 MPa in the case of numerical simulations and from 7.3 to 13.8 MPa in the case of experimental works.It is observed that cracks coalescence stresses change from 21.8 to 25.3 MPa and from 19.5 to 21.8 MPa in the numerical and experimental analyses,respectively.Comparing some of the numerical and experimental results with those recently cited in the literature validates the results obtained by the proposed study.Finally,a numerical simulation was accomplished to study the effect of confining pressure on the crack propagation process,showing that the SIFs increase and the crack initiation angles change in this case.展开更多
Biological specimens are fundamental for taxonomy and flora/fauna research.More importantly,they also play crucial roles in recording environmental impacts on morphology and behavior,which is vital for biodiversity re...Biological specimens are fundamental for taxonomy and flora/fauna research.More importantly,they also play crucial roles in recording environmental impacts on morphology and behavior,which is vital for biodiversity research and conservation.However,there are few systematic studies on the patterns and drivers of bird specimen number at regional scales.This study is the first attempt to examine the relationships between bird specimen number and species traits as well as climate niche breadth in China,aiming to answer two questions:1)how do species’temperature niche breadth and precipitation niche breadth influence specimen number?2)which trait is most associated with bird specimen number?The associations between bird specimen number and explanatory variables were examined using ordinary least squares,generalized linear models,phylogenetic generalized linear mixed models,and multiple comparisons.The results showed that Muscicapidae was the family with the highest specimen number,and Passeriformes was the order with the highest specimen number.Bird specimen number significantly increased with larger temperature niche breadth and precipitation niche breadth.Specimen number was also positively associated with geographic range size,habitat specificity,hunting vulnerability and clutch size,but negatively associated with body size.These findings suggest that future bird specimen collection should pay more attention to birds with limited ecological niches,large body sizes,and small clutch sizes.This research enhances the use of bird specimen data to study and preserve biodiversity.展开更多
Many different factors,such as species traits,socio-economic factors,geographical and environmental factors,can lead to specimen collection preference.This study aims to determine whether grassland specimen collection...Many different factors,such as species traits,socio-economic factors,geographical and environmental factors,can lead to specimen collection preference.This study aims to determine whether grassland specimen collection in China is preferred by species traits(i.e.,plant height,flowering and fruiting period),environmental range(i.e.,the temperature and precipitation range)and geographical range(i.e.,distribution range and altitudinal range).Ordinary least squares models and phylogenetic generalized linear mixed models were used to analyze the relationships between specimen number and the explanatory variables.Random Forest models were then used to find the most parsimonious multivariate model.The results showed that interannual variation in specimen number between 1900 and 2020 was considerable.Specimen number of these species in southeast China was notably lower than that in northwest China.Environmental range and geographical range of species had significant positive correlations with specimen number.In addition,there were relatively weak but significant associations between specimen number and species trait(i.e.,plant height and flowering and fruiting period).Random Forest models indicated that distribution range was the most important variable,followed by flowering and fruiting period,and altitudinal range.These findings suggest that future floristic surveys should pay more attention to species with small geographical range,narrow environmental range,short plant height,and short flowering and fruiting period.The correction of specimen collection preference will also make the results of species distribution model,species evolution and other works based on specimen data more accurate.展开更多
To compare finite element analysis(FEA)predictions and stereovision digital image correlation(StereoDIC)strain measurements at the same spatial positions throughout a region of interest,a field comparison procedure is...To compare finite element analysis(FEA)predictions and stereovision digital image correlation(StereoDIC)strain measurements at the same spatial positions throughout a region of interest,a field comparison procedure is developed.The procedure includes(a)conversion of the finite element data into a triangular mesh,(b)selection of a common coordinate system,(c)determination of the rigid body transformation to place both measurements and FEA data in the same system and(d)interpolation of the FEA nodal information to the same spatial locations as the StereoDIC measurements using barycentric coordinates.For an aluminum Al-6061 double edge notched tensile specimen,FEA results are obtained using both the von Mises isotropic yield criterion and Hill’s quadratic anisotropic yield criterion,with the unknown Hill model parameters determined using full-field specimen strain measurements for the nominally plane stress specimen.Using Hill’s quadratic anisotropic yield criterion,the point-by-point comparison of experimentally based full-field strains and stresses to finite element predictions are shown to be in excellent agreement,confirming the effectiveness of the field comparison process.展开更多
Objective:To analyze the application effect of feedforward control in outpatient blood specimen management.Methods:1,200 patients who had their venous blood collected in outpatient phlebotomy room of our hospital'...Objective:To analyze the application effect of feedforward control in outpatient blood specimen management.Methods:1,200 patients who had their venous blood collected in outpatient phlebotomy room of our hospital's outpatient clinic from January 2021 to April 2021 were selected as study subjects and divided into 600 cases in the control group and 600 cases in the observation group.The two groups of patients were compared in terms of their satisfaction with the staff,the efficiency of the nurses and the quality of nursing care,turnaround time before specimen analysis,the rejection rate of the blood specimens,and the time of result reporting.Results:After the implementation of feedforward control,patients'satisfaction with staff,nurses work efficiency and quality of care,turnaround time before specimen analysis,specimen rejection rate,and result reporting time in the observation group were significantly higher than those in the control group(P<0.05).Conclusion:The application of feedforward control in the management of outpatient blood specimens has significant effect,which effectively improves patients'satisfaction,enhances the efficiency of nurses and the quality of nursing care,shortens the turnaround time of specimens before analysis and the reporting time of results,and reduces the rejection rate of specimens.展开更多
Coalescence among fractures would have influence on the stability of rock masses. Deep understanding of mechanical behavior of fractured rock masses is an important mean to identify failure mechanism of geological dis...Coalescence among fractures would have influence on the stability of rock masses. Deep understanding of mechanical behavior of fractured rock masses is an important mean to identify failure mechanism of geological disaster. In this study, crack propagation processing was studied through loading pre-fractured specimens of concrete block, termed as rock-like material, in uniaxial compression tests. New non-parallel double-crack geometry was introduced to observe crack coalescence. The flaw combinations are different from the normally used flaw configurations. In addition, ultrasonic detection tests were performed on the test blocks. The stress and strain data of these tests and characteristic parameters of sound wave were recorded. The stress-strain curves of each test block under the uniaxial compression test were drawn, relations among deformation characteristics and crack angle of the crack specimens, and their overall strength were analyzed. It is found that strength of the specimen decreases as crack inclination increases under two crack inclinations. The highest uniaxial compressive strength is found in the specimen with the cracks at the same angle in different directions. Based on description of the crack initiation location, crack surface and the ultimate failure patterns, failure modes of eight subtype for test blocks are divided into three categories. It is expected that the study results could be beneficial for engineering application of jointed rock masses.展开更多
Strength and deformability characteristics of rock with pre-existing fissures are governed by cracking behavior. To further research the effects of pre-existing fissures on the mechanical properties and crack coalesce...Strength and deformability characteristics of rock with pre-existing fissures are governed by cracking behavior. To further research the effects of pre-existing fissures on the mechanical properties and crack coalescence process, a series of uniaxial compression tests were carried out for rock-like material with two unparallel fissures.In the present study, cement, quartz sand, and water were used to fabricate a kind of brittle rock-like material cylindrical model specimen. The mechanical properties of rock-like material specimen used in this research were all in good agreement with the brittle rock materials. Two unparallel fissures(a horizontal fissure and an inclined fissure) were created by inserting steel during molding the model specimen.Then all the pre-fissured rock-like specimens were tested under uniaxial compression by a rock mechanics servocontrolled testing system. The peak strength and Young's modulus of pre-fissured specimen all first decreased and then increased when the fissure angle increased from 0?to 75?.In order to investigate the crack initiation, propagation and coalescence process, photographic monitoring was adopted to capture images during the entire deformation process.Moreover, acoustic emission(AE) monitoring technique was also used to obtain the AE evolution characteristic of prefissured specimen. The relationship between axial stress, AE events, and the crack coalescence process was set up: when a new crack was initiated or a crack coalescence occurred, thecorresponding axial stress dropped in the axial stress–time curve and a big AE event could be observed simultaneously.Finally, the mechanism of crack propagation under microscopic observation was discussed. These experimental results are expected to increase the understanding of the strength failure behavior and the cracking mechanism of rock containing unparallel fissures.展开更多
The critical bifurcation orientation and its corresponding hardening modulus for rock-like geomaterials are derived by considering the effect of stiffness degradation and volumetric dilatancy under the assumption of i...The critical bifurcation orientation and its corresponding hardening modulus for rock-like geomaterials are derived by considering the effect of stiffness degradation and volumetric dilatancy under the assumption of isotropic damage. The dependency of the localized orientation on the degree of damage and initial Poisson's ratio of rock is examined and the bifurcation behavior of the uniaxial compression sample under the plane-stress condition is compared with that under plane-strain condition. It is shown that the localization orientation angle intimately depends on both the initial Poisson's ratio and degree of damage for the rock sample under the uniaxial compression condition. As the initial Poisson's ratio or degree of damage increases, the orientation angle of the plane on which localization tends to be initiated gets to decrease. At the same time, the localization orientation angle of a rock sample under the plane-stress condition is larger than that under the plane-strain condition.展开更多
In this study, p o ly u reth an e foam ty p e th e rm o se t polym erizing, d u e to chem ical reaction b e tw e e n itsliquid ingredients, w as teste d as b in d e r afte r solidifying and th e n a rock-like m ateria...In this study, p o ly u reth an e foam ty p e th e rm o se t polym erizing, d u e to chem ical reaction b e tw e e n itsliquid ingredients, w as teste d as b in d e r afte r solidifying and th e n a rock-like m aterial m ixing w ith asandy silt ty p e soil w as prep ared . The uniaxial com pressive stren g th s (UCSs) o f p o ly u reth an e foamreinforced soil specim ens w ere d e term in ed for different p o ly u reth an e ratios in th e m ixture. A dditionally,a series o f te sts o n slake durability, im pact value, freezing-th aw in g resistance, and ab rasio n resistance ofp o ly u reth an e reinforced soil (PRS) m ix tu re w as co n d u cted . The UCS values over 3 M Pa w ere m easuredfrom th e PRS specim ens. The testin g results show ed th a t tre a te d soil can econom ically b ecom e adesirable rock-like m aterial in term s o f slake d u ra b ility a n d resistances ag ain st freezing-thaw ing, im pacteffect an d abrasion. As a n o th e r ch aracteristic o f th e rock-like m aterial m ade w ith p o ly u reth an e foam,u n it volum e w eig h t w as found to be q uite low er th a n th o se o f n atu ral rock m aterials.展开更多
BACKGROUND Robotic resection using the natural orifice specimen extraction surgery I-type F method(R-NOSES I-F)is a novel minimally invasive surgical strategy for the treatment of lower rectal cancer.However,the curre...BACKGROUND Robotic resection using the natural orifice specimen extraction surgery I-type F method(R-NOSES I-F)is a novel minimally invasive surgical strategy for the treatment of lower rectal cancer.However,the current literature on this method is limited to case reports,and further investigation into its safety and feasibility is warranted.AIM To evaluate the safety and feasibility of R-NOSES I-F for the treatment of low rectal cancer.METHODS From September 2018 to February 2022,206 patients diagnosed with low rectal cancer at First Affiliated Hospital of Nanchang University were included in this retrospective analysis.Of these patients,22 underwent R-NOSES I-F surgery(RNOSES I-F group)and 76 underwent conventional robotic-assisted low rectal cancer resection(RLRC group).Clinicopathological data of all patients were collected and analyzed.Postoperative outcomes and prognoses were compared between the two groups.Statistical analysis was performed using SPSS software.RESULTS Patients in the R-NOSES I-F group had a significantly lower visual analog score for pain on postoperative day 1(1.7±0.7 vs 2.2±0.6,P=0.003)and shorter postoperative anal venting time(2.7±0.6 vs 3.5±0.7,P<0.001)than those in the RLRC group.There were no significant differences between the two groups in terms of sex,age,body mass index,tumor size,TNM stage,operative time,intrao-perative bleeding,postoperative complications,or inflammatory response(P>0.05).Postoperative anal and urinary functions,as assessed by Wexner,low anterior resection syndrome,and International Prostate Symptom Scale scores,were similar in both groups(P>0.05).Long-term follow-up revealed no significant differences in the rates of local recurrence and distant metastasis between the two groups(P>0.05).CONCLUSION R-NOSES I-F is a safe and effective minimally invasive procedure for the treatment of lower rectal cancer.It improves pain relief,promotes gastrointestinal function recovery,and helps avoid incision-related complications.展开更多
An inverse method for parameters identification of discrete element model combined with experiment is proposed.The inverse problem of parameter identification is transmitted to solve an optimization problem by minimiz...An inverse method for parameters identification of discrete element model combined with experiment is proposed.The inverse problem of parameter identification is transmitted to solve an optimization problem by minimizing the distance between the numerical calculations and experiment responses.In this method,the discrete element method is employed as numerical calculator for the forward problem.Then,the orthogonal experiment design with range analysis was used to carry out parameters sensitivity analysis.In addition,to improve the computational efficiency,the approximate model technique is used to replace the actual computational model.The intergeneration projection genetic algorithm(IP-GA)is employed as the optimization algorithm.Consequently,the parameters of the discrete element model are determined.To verify the effectiveness and accuracy of the inverse results,the comparisons of shape deviation experiments with discrete element simulations are provided.It indicates that the effective and reliable discrete element model parameters can be quickly obtained through several sets of experimental data.Hence,this inverse method can be applied more widely to determine the parameters of discrete element model for other materials.展开更多
为研究高应力围岩扰动破坏机制,开展了不同围压下类岩石试件的三轴常规压缩和三轴循环扰动试验,得到了试件的扰动应力–应变规律和变形破坏特征,并对试件开展了核磁共振(Nuclear Magnetic Resonance)成像试验,从微观角度进一步阐明了试...为研究高应力围岩扰动破坏机制,开展了不同围压下类岩石试件的三轴常规压缩和三轴循环扰动试验,得到了试件的扰动应力–应变规律和变形破坏特征,并对试件开展了核磁共振(Nuclear Magnetic Resonance)成像试验,从微观角度进一步阐明了试件扰动破坏机理。研究结果表明:(1)试件在不同围压下均存在一个阈值强度,轴向荷载超过阈值强度后,轴向变形对扰动变得敏感,再次施加扰动会引起试件显著变形,当轴向荷载低于阈值强度时,变形对扰动不敏感。阈值强度与极限强度的比值可以反映试件的抗扰动能力,随着围压增大,该比值呈现逐步递减的规律,说明高围压下试件抗扰动能力下降,对扰动作用更敏感。(2)扰动作用下类岩石试件存在弱化效应,如常规三轴10MPa围压下试件表现出腰鼓破坏,而受扰动作用后,试件呈现斜切脆性破坏,与常规三轴5MPa围压下破坏形态相近。(3)岩石试件在高应力作用下进入塑性流动状态,内部颗粒重新排列,内部小孔隙与大孔隙的占比减少,而中孔隙的占比显著增多,试件内部孔隙率整体降低。展开更多
To explore ways to improve the accuracy of quantitative analysis of samples in the micrometer to nanometer range of magnitudes,we adopted analytical transmission electron microscopy(AEM/EDS)for qualitative and quantit...To explore ways to improve the accuracy of quantitative analysis of samples in the micrometer to nanometer range of magnitudes,we adopted analytical transmission electron microscopy(AEM/EDS)for qualitative and quantitative analysis of pyrite materials.Additionally,the k factor of pyrite is calculated experimentally.To develop an appropriate non-standard quantitative analysis model for pyrite materials,the experimentally calculated k factor is compared with that estimated from the non-standard quantitative analytical model of the instrument software.The experimental findings demonstrate that the EDS attached to a TEM can be employed for precise quantitative analysis of micro-and nanoscale regions of pyrite materials.Furthermore,it serves as a reference for improving the results of the EDS quantitative analysis of other sulfides.展开更多
The rejected specimens from the Emergency Department of the Center of Clinical Laboratory from January 1,2022 to January 1,2023 were analyzed to reduce the specimen rejection rates and to improve the quality of inspec...The rejected specimens from the Emergency Department of the Center of Clinical Laboratory from January 1,2022 to January 1,2023 were analyzed to reduce the specimen rejection rates and to improve the quality of inspection.The results showed that there were 1488 samples of rejected specimens and the non-conforming rate was 0.58%.The departments involved were mainly the Emergency Department,the Hematology Department,the Cardiology Department,the Intensive Care Department,and the Brain Surgery Department.Among the reasons for rejection,blood hemolysis accounted for 43.15%,blood coagulation accounted for 26.61%,and the rate of insufficient specimens was 17.14%.Among them,the sample rejection rate for arterial blood gas analysis was the highest,which accounted for 1.74%;followed by specimens for coagulation test,which was 1.18%.These results indicate the main reason for producing rejected specimens is mainly due to not following the standard operating procedure.Specimen rejection can largely be avoided if the standards for specimen collection are strictly followed.展开更多
文摘The mechanism of cracks propagation and cracks coalescence due to compressive loading of the brittle substances containing pre-existing cracks(flaws)was modeled experimentally using specially made rock-like specimens from Portland Pozzolana Cement(PPC).The breakage process of the specimens was studied by inserting single and double flaws with different inclination angles at the center and applying uniaxial compressive stress at both ends of the specimen.The first crack was oriented at 50° from the horizontal direction and kept constant throughout the analysis while the orientation of the second crack was changed.It is experimentally observed that the wing cracks are produced at the first stage of loading and start their propagation toward the direction of uniaxial compressive loading.The secondary cracks may also be produced in form of quasi-coplanar and/or oblique cracks in a stable manner.The secondary cracks may eventually continue their propagation in the direction of maximum principle stress.These experimental works were also simulated numerically by a modified higher order displacement discontinuity method and the cracks propagation and cracks coalescence were studied based on Mode I and Mode II stress intensity factors(SIFs).It is concluded that the wing cracks initiation stresses for the specimens change from 11.3 to 14.1 MPa in the case of numerical simulations and from 7.3 to 13.8 MPa in the case of experimental works.It is observed that cracks coalescence stresses change from 21.8 to 25.3 MPa and from 19.5 to 21.8 MPa in the numerical and experimental analyses,respectively.Comparing some of the numerical and experimental results with those recently cited in the literature validates the results obtained by the proposed study.Finally,a numerical simulation was accomplished to study the effect of confining pressure on the crack propagation process,showing that the SIFs increase and the crack initiation angles change in this case.
基金supported by the Natural Science Foundation of Inner Mongolia,China(2023JQ01)the National Key R&D Program of China(2019YFA0607103)+2 种基金the Central Government Guides Local Science and Technology Development Fund Projects(2022ZY0224)the Open Project Program of’Ministry of Education Key Laboratory of Ecology and Resources Use of the Mongolian Plateau(KF2023003)’the Major Science and Technology Project of Inner Mongolia Autonomous Region:Monitoring,Assessment and Early Warning Technology Research of Biodiversity in Inner Mongolia(2021ZD0011)。
文摘Biological specimens are fundamental for taxonomy and flora/fauna research.More importantly,they also play crucial roles in recording environmental impacts on morphology and behavior,which is vital for biodiversity research and conservation.However,there are few systematic studies on the patterns and drivers of bird specimen number at regional scales.This study is the first attempt to examine the relationships between bird specimen number and species traits as well as climate niche breadth in China,aiming to answer two questions:1)how do species’temperature niche breadth and precipitation niche breadth influence specimen number?2)which trait is most associated with bird specimen number?The associations between bird specimen number and explanatory variables were examined using ordinary least squares,generalized linear models,phylogenetic generalized linear mixed models,and multiple comparisons.The results showed that Muscicapidae was the family with the highest specimen number,and Passeriformes was the order with the highest specimen number.Bird specimen number significantly increased with larger temperature niche breadth and precipitation niche breadth.Specimen number was also positively associated with geographic range size,habitat specificity,hunting vulnerability and clutch size,but negatively associated with body size.These findings suggest that future bird specimen collection should pay more attention to birds with limited ecological niches,large body sizes,and small clutch sizes.This research enhances the use of bird specimen data to study and preserve biodiversity.
基金the Natural Science Foundation of Inner Mongolia,China(2023JQ01)the National Key R&D Program of China(2019YFA0607103)+2 种基金the Central Government Guides Local Science and Technology Development Fund Projects(2022ZY0224)the Open Project Program of Ministry of Education Key Laboratory of Ecology and Resources Use of the Mongolian Plateau,Hohhot,Inner Mongolia,China(KF2023003)Major Science and Technology Project of Inner Mongolia Autonomous Region:Monitoring,Assessment and Early Warning Technology Research of Biodiversity in Inner Mongolia(2021ZD0011)for financial support.
文摘Many different factors,such as species traits,socio-economic factors,geographical and environmental factors,can lead to specimen collection preference.This study aims to determine whether grassland specimen collection in China is preferred by species traits(i.e.,plant height,flowering and fruiting period),environmental range(i.e.,the temperature and precipitation range)and geographical range(i.e.,distribution range and altitudinal range).Ordinary least squares models and phylogenetic generalized linear mixed models were used to analyze the relationships between specimen number and the explanatory variables.Random Forest models were then used to find the most parsimonious multivariate model.The results showed that interannual variation in specimen number between 1900 and 2020 was considerable.Specimen number of these species in southeast China was notably lower than that in northwest China.Environmental range and geographical range of species had significant positive correlations with specimen number.In addition,there were relatively weak but significant associations between specimen number and species trait(i.e.,plant height and flowering and fruiting period).Random Forest models indicated that distribution range was the most important variable,followed by flowering and fruiting period,and altitudinal range.These findings suggest that future floristic surveys should pay more attention to species with small geographical range,narrow environmental range,short plant height,and short flowering and fruiting period.The correction of specimen collection preference will also make the results of species distribution model,species evolution and other works based on specimen data more accurate.
基金Financial support provided by Correlated Solutions Incorporated to perform StereoDIC experimentsthe Department of Mechanical Engineering at the University of South Carolina for simulation studies is deeply appreciated.
文摘To compare finite element analysis(FEA)predictions and stereovision digital image correlation(StereoDIC)strain measurements at the same spatial positions throughout a region of interest,a field comparison procedure is developed.The procedure includes(a)conversion of the finite element data into a triangular mesh,(b)selection of a common coordinate system,(c)determination of the rigid body transformation to place both measurements and FEA data in the same system and(d)interpolation of the FEA nodal information to the same spatial locations as the StereoDIC measurements using barycentric coordinates.For an aluminum Al-6061 double edge notched tensile specimen,FEA results are obtained using both the von Mises isotropic yield criterion and Hill’s quadratic anisotropic yield criterion,with the unknown Hill model parameters determined using full-field specimen strain measurements for the nominally plane stress specimen.Using Hill’s quadratic anisotropic yield criterion,the point-by-point comparison of experimentally based full-field strains and stresses to finite element predictions are shown to be in excellent agreement,confirming the effectiveness of the field comparison process.
文摘Objective:To analyze the application effect of feedforward control in outpatient blood specimen management.Methods:1,200 patients who had their venous blood collected in outpatient phlebotomy room of our hospital's outpatient clinic from January 2021 to April 2021 were selected as study subjects and divided into 600 cases in the control group and 600 cases in the observation group.The two groups of patients were compared in terms of their satisfaction with the staff,the efficiency of the nurses and the quality of nursing care,turnaround time before specimen analysis,the rejection rate of the blood specimens,and the time of result reporting.Results:After the implementation of feedforward control,patients'satisfaction with staff,nurses work efficiency and quality of care,turnaround time before specimen analysis,specimen rejection rate,and result reporting time in the observation group were significantly higher than those in the control group(P<0.05).Conclusion:The application of feedforward control in the management of outpatient blood specimens has significant effect,which effectively improves patients'satisfaction,enhances the efficiency of nurses and the quality of nursing care,shortens the turnaround time of specimens before analysis and the reporting time of results,and reduces the rejection rate of specimens.
文摘Coalescence among fractures would have influence on the stability of rock masses. Deep understanding of mechanical behavior of fractured rock masses is an important mean to identify failure mechanism of geological disaster. In this study, crack propagation processing was studied through loading pre-fractured specimens of concrete block, termed as rock-like material, in uniaxial compression tests. New non-parallel double-crack geometry was introduced to observe crack coalescence. The flaw combinations are different from the normally used flaw configurations. In addition, ultrasonic detection tests were performed on the test blocks. The stress and strain data of these tests and characteristic parameters of sound wave were recorded. The stress-strain curves of each test block under the uniaxial compression test were drawn, relations among deformation characteristics and crack angle of the crack specimens, and their overall strength were analyzed. It is found that strength of the specimen decreases as crack inclination increases under two crack inclinations. The highest uniaxial compressive strength is found in the specimen with the cracks at the same angle in different directions. Based on description of the crack initiation location, crack surface and the ultimate failure patterns, failure modes of eight subtype for test blocks are divided into three categories. It is expected that the study results could be beneficial for engineering application of jointed rock masses.
基金supported by the National Natural Science Foundation of China (Grant 51179189)the National Basic Research 973 Program of China (Grant 2013CB036003)+2 种基金the Program for New Century Excellent Talents in University (Grant NCET-120961)Outstanding Innovation Team Project in China University of Mining and Technology (Grant 2014QN002)the Fundamental Research Funds for the Central Universities (Grants 2014YC10 and 2014XT03)
文摘Strength and deformability characteristics of rock with pre-existing fissures are governed by cracking behavior. To further research the effects of pre-existing fissures on the mechanical properties and crack coalescence process, a series of uniaxial compression tests were carried out for rock-like material with two unparallel fissures.In the present study, cement, quartz sand, and water were used to fabricate a kind of brittle rock-like material cylindrical model specimen. The mechanical properties of rock-like material specimen used in this research were all in good agreement with the brittle rock materials. Two unparallel fissures(a horizontal fissure and an inclined fissure) were created by inserting steel during molding the model specimen.Then all the pre-fissured rock-like specimens were tested under uniaxial compression by a rock mechanics servocontrolled testing system. The peak strength and Young's modulus of pre-fissured specimen all first decreased and then increased when the fissure angle increased from 0?to 75?.In order to investigate the crack initiation, propagation and coalescence process, photographic monitoring was adopted to capture images during the entire deformation process.Moreover, acoustic emission(AE) monitoring technique was also used to obtain the AE evolution characteristic of prefissured specimen. The relationship between axial stress, AE events, and the crack coalescence process was set up: when a new crack was initiated or a crack coalescence occurred, thecorresponding axial stress dropped in the axial stress–time curve and a big AE event could be observed simultaneously.Finally, the mechanism of crack propagation under microscopic observation was discussed. These experimental results are expected to increase the understanding of the strength failure behavior and the cracking mechanism of rock containing unparallel fissures.
基金Project supported by the National Natural Sciences Foundation of China (No. 10172022).
文摘The critical bifurcation orientation and its corresponding hardening modulus for rock-like geomaterials are derived by considering the effect of stiffness degradation and volumetric dilatancy under the assumption of isotropic damage. The dependency of the localized orientation on the degree of damage and initial Poisson's ratio of rock is examined and the bifurcation behavior of the uniaxial compression sample under the plane-stress condition is compared with that under plane-strain condition. It is shown that the localization orientation angle intimately depends on both the initial Poisson's ratio and degree of damage for the rock sample under the uniaxial compression condition. As the initial Poisson's ratio or degree of damage increases, the orientation angle of the plane on which localization tends to be initiated gets to decrease. At the same time, the localization orientation angle of a rock sample under the plane-stress condition is larger than that under the plane-strain condition.
文摘In this study, p o ly u reth an e foam ty p e th e rm o se t polym erizing, d u e to chem ical reaction b e tw e e n itsliquid ingredients, w as teste d as b in d e r afte r solidifying and th e n a rock-like m aterial m ixing w ith asandy silt ty p e soil w as prep ared . The uniaxial com pressive stren g th s (UCSs) o f p o ly u reth an e foamreinforced soil specim ens w ere d e term in ed for different p o ly u reth an e ratios in th e m ixture. A dditionally,a series o f te sts o n slake durability, im pact value, freezing-th aw in g resistance, and ab rasio n resistance ofp o ly u reth an e reinforced soil (PRS) m ix tu re w as co n d u cted . The UCS values over 3 M Pa w ere m easuredfrom th e PRS specim ens. The testin g results show ed th a t tre a te d soil can econom ically b ecom e adesirable rock-like m aterial in term s o f slake d u ra b ility a n d resistances ag ain st freezing-thaw ing, im pacteffect an d abrasion. As a n o th e r ch aracteristic o f th e rock-like m aterial m ade w ith p o ly u reth an e foam,u n it volum e w eig h t w as found to be q uite low er th a n th o se o f n atu ral rock m aterials.
基金National Natural Science Foundation of China,No.81860519.
文摘BACKGROUND Robotic resection using the natural orifice specimen extraction surgery I-type F method(R-NOSES I-F)is a novel minimally invasive surgical strategy for the treatment of lower rectal cancer.However,the current literature on this method is limited to case reports,and further investigation into its safety and feasibility is warranted.AIM To evaluate the safety and feasibility of R-NOSES I-F for the treatment of low rectal cancer.METHODS From September 2018 to February 2022,206 patients diagnosed with low rectal cancer at First Affiliated Hospital of Nanchang University were included in this retrospective analysis.Of these patients,22 underwent R-NOSES I-F surgery(RNOSES I-F group)and 76 underwent conventional robotic-assisted low rectal cancer resection(RLRC group).Clinicopathological data of all patients were collected and analyzed.Postoperative outcomes and prognoses were compared between the two groups.Statistical analysis was performed using SPSS software.RESULTS Patients in the R-NOSES I-F group had a significantly lower visual analog score for pain on postoperative day 1(1.7±0.7 vs 2.2±0.6,P=0.003)and shorter postoperative anal venting time(2.7±0.6 vs 3.5±0.7,P<0.001)than those in the RLRC group.There were no significant differences between the two groups in terms of sex,age,body mass index,tumor size,TNM stage,operative time,intrao-perative bleeding,postoperative complications,or inflammatory response(P>0.05).Postoperative anal and urinary functions,as assessed by Wexner,low anterior resection syndrome,and International Prostate Symptom Scale scores,were similar in both groups(P>0.05).Long-term follow-up revealed no significant differences in the rates of local recurrence and distant metastasis between the two groups(P>0.05).CONCLUSION R-NOSES I-F is a safe and effective minimally invasive procedure for the treatment of lower rectal cancer.It improves pain relief,promotes gastrointestinal function recovery,and helps avoid incision-related complications.
基金supported by the National Natural Science Foundation of China(11602212)the Natural Science Foundation of Hunan Province of China(2018JJ3509)supported by the National Natural Science Foundation of China(51605409,11802258,51775468).
文摘An inverse method for parameters identification of discrete element model combined with experiment is proposed.The inverse problem of parameter identification is transmitted to solve an optimization problem by minimizing the distance between the numerical calculations and experiment responses.In this method,the discrete element method is employed as numerical calculator for the forward problem.Then,the orthogonal experiment design with range analysis was used to carry out parameters sensitivity analysis.In addition,to improve the computational efficiency,the approximate model technique is used to replace the actual computational model.The intergeneration projection genetic algorithm(IP-GA)is employed as the optimization algorithm.Consequently,the parameters of the discrete element model are determined.To verify the effectiveness and accuracy of the inverse results,the comparisons of shape deviation experiments with discrete element simulations are provided.It indicates that the effective and reliable discrete element model parameters can be quickly obtained through several sets of experimental data.Hence,this inverse method can be applied more widely to determine the parameters of discrete element model for other materials.
文摘为研究高应力围岩扰动破坏机制,开展了不同围压下类岩石试件的三轴常规压缩和三轴循环扰动试验,得到了试件的扰动应力–应变规律和变形破坏特征,并对试件开展了核磁共振(Nuclear Magnetic Resonance)成像试验,从微观角度进一步阐明了试件扰动破坏机理。研究结果表明:(1)试件在不同围压下均存在一个阈值强度,轴向荷载超过阈值强度后,轴向变形对扰动变得敏感,再次施加扰动会引起试件显著变形,当轴向荷载低于阈值强度时,变形对扰动不敏感。阈值强度与极限强度的比值可以反映试件的抗扰动能力,随着围压增大,该比值呈现逐步递减的规律,说明高围压下试件抗扰动能力下降,对扰动作用更敏感。(2)扰动作用下类岩石试件存在弱化效应,如常规三轴10MPa围压下试件表现出腰鼓破坏,而受扰动作用后,试件呈现斜切脆性破坏,与常规三轴5MPa围压下破坏形态相近。(3)岩石试件在高应力作用下进入塑性流动状态,内部颗粒重新排列,内部小孔隙与大孔隙的占比减少,而中孔隙的占比显著增多,试件内部孔隙率整体降低。
基金Funded by the International Science&Technology Cooperation Program of Hubei Province of China(No.2022EHB024)。
文摘To explore ways to improve the accuracy of quantitative analysis of samples in the micrometer to nanometer range of magnitudes,we adopted analytical transmission electron microscopy(AEM/EDS)for qualitative and quantitative analysis of pyrite materials.Additionally,the k factor of pyrite is calculated experimentally.To develop an appropriate non-standard quantitative analysis model for pyrite materials,the experimentally calculated k factor is compared with that estimated from the non-standard quantitative analytical model of the instrument software.The experimental findings demonstrate that the EDS attached to a TEM can be employed for precise quantitative analysis of micro-and nanoscale regions of pyrite materials.Furthermore,it serves as a reference for improving the results of the EDS quantitative analysis of other sulfides.
文摘The rejected specimens from the Emergency Department of the Center of Clinical Laboratory from January 1,2022 to January 1,2023 were analyzed to reduce the specimen rejection rates and to improve the quality of inspection.The results showed that there were 1488 samples of rejected specimens and the non-conforming rate was 0.58%.The departments involved were mainly the Emergency Department,the Hematology Department,the Cardiology Department,the Intensive Care Department,and the Brain Surgery Department.Among the reasons for rejection,blood hemolysis accounted for 43.15%,blood coagulation accounted for 26.61%,and the rate of insufficient specimens was 17.14%.Among them,the sample rejection rate for arterial blood gas analysis was the highest,which accounted for 1.74%;followed by specimens for coagulation test,which was 1.18%.These results indicate the main reason for producing rejected specimens is mainly due to not following the standard operating procedure.Specimen rejection can largely be avoided if the standards for specimen collection are strictly followed.