Ground failure is a major contributor to fatalities in underground mines in the US.Underground coal mines in the Northern Appalachian have weak roof rock composed of shale,which is prone to failure under high horizont...Ground failure is a major contributor to fatalities in underground mines in the US.Underground coal mines in the Northern Appalachian have weak roof rock composed of shale,which is prone to failure under high horizontal stress.Understanding the relationship among strength,specimen size and rock petrographic parameters is essential for developing an effective ground control plan.Size effect studies have found that rock strength varies with specimen size.This paper attempts to understand this strength variation using three specimen sizes(254-mm,508-mm,and 762-mm).The specimen strength was measured and the major petrographic parameters affecting the strength,namely grain size,grain shape,quartz content,clay content,etc.were analyzed using X-ray diffraction(XRD)and scanning electron microscopy(SEM).The petrographic parameters were then correlated with the strength of the three differently sized specimens.The results showed that 508-mm specimen had the lowest strength.Quartz content of the 508-mm specimen was lower than that of 254-mm and 762-mm specimens.Clay content and average grain size of the 508-mm specimen were higher than those of 254-mm and 762-mm specimens.These results clearly show that grain size,quartz content and clay content contribute to strength variation observed in differently sized shale specimens.展开更多
In this study, 40 Cr Mn Si B steel cylindrical shells were tempered at 350, 500 and 600 ℃ to study the effect of tempering temperature on the dynamic process of expansion and fracture of the metal shell. A midexplosi...In this study, 40 Cr Mn Si B steel cylindrical shells were tempered at 350, 500 and 600 ℃ to study the effect of tempering temperature on the dynamic process of expansion and fracture of the metal shell. A midexplosion recovery experiment for the metal cylinder under internal explosive loading was designed, and the wreckage of the casings at the intermediate phase was obtained. The effects of different tempering temperatures on the macroscopic and microscopic fracture characteristics of 40 Cr Mn Si B steel were studied. The influence of tempering temperatures on the fracture characteristic parameters of the recovered wreckage were measured and analyzed, including the circumferential divide size, the thickness and the number of the circumferential divisions. The results show that as the tempering temperature was increased from 350 to 600 ℃, at first, the degree of fragmentation and the fracture characteristic parameters of the recovered wreckage changed significantly and then became essentially consistent. Scanning electron microscopy analysis revealed flow-like structure characteristics caused by adiabatic shear on different fracture surfaces. At the detonation initiation end of the casing, fracturing was formed by tearing along the crack, which existed a distance from the initiation end and propagated along the axis direction. In contrast, the fracturing near the middle position consists of a plurality of radial shear fracture units. The amount of alloy carbide that was precipitated during the tempering process increased continuously with tempering temperature, leading to an increasing number of spherical carbide particles scattered around the fracture surface.展开更多
Electro-spinning is a very modern process which can be used in various purposes. We did this experimental work at Swerea IVF in Sweden during M. Sc in Textile Technology programme at University of Bor?s. We should esp...Electro-spinning is a very modern process which can be used in various purposes. We did this experimental work at Swerea IVF in Sweden during M. Sc in Textile Technology programme at University of Bor?s. We should especially thank our supervisor—Anna Thorvaldsson and course teacher—Ioannis S. Chronakis. In this report, we have tried to explain the basic manufacturing techniques of the electrospun nanofiber by the electro-spinning, how one can characterize it by SEM (Scanning Electron Microscopy) and its various applications in the practical field, e.g wound healing, Tissue Engineering Scaffold. The experimental work helped us a lot to gather sufficient knowledge about the electro-spinning process which we wanted to share with all.展开更多
In this paper,scanning acoustic microscope(SAM) was used to obtainsome characteristic photographs which explain the mesoscopic information of severalcracked specimens.New results on subsurface information of steel,nic...In this paper,scanning acoustic microscope(SAM) was used to obtainsome characteristic photographs which explain the mesoscopic information of severalcracked specimens.New results on subsurface information of steel,nickel andaluminium were presented.Plastic deformation and crack initiation were observed andanalysed.The length of crack propagation was measured.SAM is particularly suited tothe study of many mesoscopic phenomena in material science because it can imagemesoscopic subsurface feature without sectioning.It is revealed that SAM has a brightfuture in the field of mesomechanics.展开更多
In this study, we use a pluripotent mesenchymal stem cell (MSC) model, C3H/10T1/2, to evaluate three calcium phos-phate (CaP) materials, namely the hydroxyapatite (HA), α-tricalcium phosphate (α-TCP) and β-tricalci...In this study, we use a pluripotent mesenchymal stem cell (MSC) model, C3H/10T1/2, to evaluate three calcium phos-phate (CaP) materials, namely the hydroxyapatite (HA), α-tricalcium phosphate (α-TCP) and β-tricalcium phosphate (β-TCP). 10T1/2 cell was chosen as it has advantages over its counterparts in terms of ease of maintenance, free of ethical concerns and also more reproducible results. ALP enzymatic assay, RT-qPCR, DAPI staining and SEM were employed to assess the osteoinductivity of these materials. A good reference material which also acts as a scientific control is necessary for comparisons of results from different experimental batches and hence other materials such as titanium, Nunclon plastic surface, BD Falcon plastic surface and gold coated porous HA were also tested. The results show that ceramics induce a more sustained osteo-differentiation state as compared with plastics. Inductivity was found to be acting in descending order of strength with HA > β-TCP > α-TCP, which is reversed in terms of their impact on proliferation rate (HA TCP) and in vivo osteoinductivity in terms of incidence and quality of bone described previously (HA > β-TCP > α-TCP). These confirm the suitability of using 10T1/2 cells in cell culture assay of osteoinductivity.展开更多
This study shows that submicron/nanoparticles found in bacterial cells (S. aureus) incubated with polyurethane (a material commonly used for prostheses in odontostomatology) are a consequence of biodestruction. The pr...This study shows that submicron/nanoparticles found in bacterial cells (S. aureus) incubated with polyurethane (a material commonly used for prostheses in odontostomatology) are a consequence of biodestruction. The presence of polyurethane nanoparticles into bacterial vesicles suggests that the internalization process occurs through endocytosis. TEM and FIB/SEM are a suitable set of correlated instruments and techniques for this multi facet investigation: polyurethane particles influence the properties of S. aureus from the morpho-functional standpoint that may have undesirable effects on the human body. S. aureus and C. albicans are symbiotic microorganisms;it was observed that C. albicans has a similar interaction with polyurethane and an increment of the biodestruction capacity is expected by its mutual work with S. aureus.展开更多
本文以人教版Book4 Unit1 A Student of African wildlife阅读课为例,阐述英语阅读教学的具体方法,讲清教学目标,定好教学立意,分阶段展开教学过程,并在每一个教学过程中都有明确的教学意图,循序渐进,步步深入,训练学生略读（scanning...本文以人教版Book4 Unit1 A Student of African wildlife阅读课为例,阐述英语阅读教学的具体方法,讲清教学目标,定好教学立意,分阶段展开教学过程,并在每一个教学过程中都有明确的教学意图,循序渐进,步步深入,训练学生略读（scanning）、细读（close reading）、归纳内容（summarizing）等技巧,获取文章中的重要信息,把握文章的中心内容。展开更多
文摘Ground failure is a major contributor to fatalities in underground mines in the US.Underground coal mines in the Northern Appalachian have weak roof rock composed of shale,which is prone to failure under high horizontal stress.Understanding the relationship among strength,specimen size and rock petrographic parameters is essential for developing an effective ground control plan.Size effect studies have found that rock strength varies with specimen size.This paper attempts to understand this strength variation using three specimen sizes(254-mm,508-mm,and 762-mm).The specimen strength was measured and the major petrographic parameters affecting the strength,namely grain size,grain shape,quartz content,clay content,etc.were analyzed using X-ray diffraction(XRD)and scanning electron microscopy(SEM).The petrographic parameters were then correlated with the strength of the three differently sized specimens.The results showed that 508-mm specimen had the lowest strength.Quartz content of the 508-mm specimen was lower than that of 254-mm and 762-mm specimens.Clay content and average grain size of the 508-mm specimen were higher than those of 254-mm and 762-mm specimens.These results clearly show that grain size,quartz content and clay content contribute to strength variation observed in differently sized shale specimens.
基金funded by the National Natural Science Foundation of China (Grant No.11972018)sponsored by the Defense Pre-Research Joint Foundation of Chinese Ordnance Industry (Grant No. 6141B012858)。
文摘In this study, 40 Cr Mn Si B steel cylindrical shells were tempered at 350, 500 and 600 ℃ to study the effect of tempering temperature on the dynamic process of expansion and fracture of the metal shell. A midexplosion recovery experiment for the metal cylinder under internal explosive loading was designed, and the wreckage of the casings at the intermediate phase was obtained. The effects of different tempering temperatures on the macroscopic and microscopic fracture characteristics of 40 Cr Mn Si B steel were studied. The influence of tempering temperatures on the fracture characteristic parameters of the recovered wreckage were measured and analyzed, including the circumferential divide size, the thickness and the number of the circumferential divisions. The results show that as the tempering temperature was increased from 350 to 600 ℃, at first, the degree of fragmentation and the fracture characteristic parameters of the recovered wreckage changed significantly and then became essentially consistent. Scanning electron microscopy analysis revealed flow-like structure characteristics caused by adiabatic shear on different fracture surfaces. At the detonation initiation end of the casing, fracturing was formed by tearing along the crack, which existed a distance from the initiation end and propagated along the axis direction. In contrast, the fracturing near the middle position consists of a plurality of radial shear fracture units. The amount of alloy carbide that was precipitated during the tempering process increased continuously with tempering temperature, leading to an increasing number of spherical carbide particles scattered around the fracture surface.
文摘Electro-spinning is a very modern process which can be used in various purposes. We did this experimental work at Swerea IVF in Sweden during M. Sc in Textile Technology programme at University of Bor?s. We should especially thank our supervisor—Anna Thorvaldsson and course teacher—Ioannis S. Chronakis. In this report, we have tried to explain the basic manufacturing techniques of the electrospun nanofiber by the electro-spinning, how one can characterize it by SEM (Scanning Electron Microscopy) and its various applications in the practical field, e.g wound healing, Tissue Engineering Scaffold. The experimental work helped us a lot to gather sufficient knowledge about the electro-spinning process which we wanted to share with all.
基金Sponsored by the National Natural Science Foundation of China.
文摘In this paper,scanning acoustic microscope(SAM) was used to obtainsome characteristic photographs which explain the mesoscopic information of severalcracked specimens.New results on subsurface information of steel,nickel andaluminium were presented.Plastic deformation and crack initiation were observed andanalysed.The length of crack propagation was measured.SAM is particularly suited tothe study of many mesoscopic phenomena in material science because it can imagemesoscopic subsurface feature without sectioning.It is revealed that SAM has a brightfuture in the field of mesomechanics.
文摘In this study, we use a pluripotent mesenchymal stem cell (MSC) model, C3H/10T1/2, to evaluate three calcium phos-phate (CaP) materials, namely the hydroxyapatite (HA), α-tricalcium phosphate (α-TCP) and β-tricalcium phosphate (β-TCP). 10T1/2 cell was chosen as it has advantages over its counterparts in terms of ease of maintenance, free of ethical concerns and also more reproducible results. ALP enzymatic assay, RT-qPCR, DAPI staining and SEM were employed to assess the osteoinductivity of these materials. A good reference material which also acts as a scientific control is necessary for comparisons of results from different experimental batches and hence other materials such as titanium, Nunclon plastic surface, BD Falcon plastic surface and gold coated porous HA were also tested. The results show that ceramics induce a more sustained osteo-differentiation state as compared with plastics. Inductivity was found to be acting in descending order of strength with HA > β-TCP > α-TCP, which is reversed in terms of their impact on proliferation rate (HA TCP) and in vivo osteoinductivity in terms of incidence and quality of bone described previously (HA > β-TCP > α-TCP). These confirm the suitability of using 10T1/2 cells in cell culture assay of osteoinductivity.
文摘This study shows that submicron/nanoparticles found in bacterial cells (S. aureus) incubated with polyurethane (a material commonly used for prostheses in odontostomatology) are a consequence of biodestruction. The presence of polyurethane nanoparticles into bacterial vesicles suggests that the internalization process occurs through endocytosis. TEM and FIB/SEM are a suitable set of correlated instruments and techniques for this multi facet investigation: polyurethane particles influence the properties of S. aureus from the morpho-functional standpoint that may have undesirable effects on the human body. S. aureus and C. albicans are symbiotic microorganisms;it was observed that C. albicans has a similar interaction with polyurethane and an increment of the biodestruction capacity is expected by its mutual work with S. aureus.
文摘本文以人教版Book4 Unit1 A Student of African wildlife阅读课为例,阐述英语阅读教学的具体方法,讲清教学目标,定好教学立意,分阶段展开教学过程,并在每一个教学过程中都有明确的教学意图,循序渐进,步步深入,训练学生略读（scanning）、细读（close reading）、归纳内容（summarizing）等技巧,获取文章中的重要信息,把握文章的中心内容。
