The installation of a back-wall guard-board is the key to successfully supporting underground retreating roadways in coal mines. Based on the coordinate support principle, and using an I-shaped steel support for the s...The installation of a back-wall guard-board is the key to successfully supporting underground retreating roadways in coal mines. Based on the coordinate support principle, and using an I-shaped steel support for the surrounding rock, a mechanical model was developed for the stability of the roadway support and surrounding rock. Analysis of the bearing capacity of the roof back-wall guard-board and modelling of the equations for the maximum deflection and the maximum compressive stress of the top and side beams of the I-shaped steel support were undertaken. Simultaneously, the model was used to calculate and analyse the stability of the top and side beams of the I-shaped steel support structure and analyse the criteria for their stability. The results provide a reliable theoretical basis for the judgment of the stability of the surrounding rock and support structure. The theoretical evaluation results are consistent with field data. Finally, the key support parameters of the top and side beams of the I-shaped steel support structure and the variation of the maximum deflection and the maximum compressive stress as affected by the influence of the guard-board length were investigated. It is concluded that, as the back-board length increases, the maximum compressive stress in the top beam of the I-shaped steel support increases while the compressive stress in the side beam decreases. The results show that the accuracy of judgment of the stability of a supported retreating roadway is improved, providing guidance for the design of such typical I-shaped steel support and back-board structures.展开更多
Dinoflagellate is one of the primitive eukaryotes, whose nucleus may represent one of the transition stages from prokaryotic nucleoid to typical eukaryotic nucleus. Using selective extraction together with embeddment ...Dinoflagellate is one of the primitive eukaryotes, whose nucleus may represent one of the transition stages from prokaryotic nucleoid to typical eukaryotic nucleus. Using selective extraction together with embeddment - free section and whole mount electron microscopy, a delicate nuclear matrix filament network was shown, for the first time, in dinoflagellate Crypthecodinium cohnii nucleus. Chromosome residues are connected with nuclear matrix filaments to form a complete network spreading over the nucleus. Moreover, we demonstrated that the dinoflagellate chromosome retains a protein scaffold after the depletion of DNA and soluble proteins. This scaffold preserves the characteristic morphology of the chromosome. Two dimensional elec-trophoreses indicated that the nuclear matrix and chromosome scaffold are mainly composed of acidic proteins. Our results demonstrated that a framework similar to the nuclear matrix and chromosome scaffold in mammalian cells appears in this primitive eukaryote,suggesting that these structures may have been originated from the early stages of eukaryote evolution.展开更多
The end windings of generators are excited to vibrations due to electromagnetic forces which can cause severe damage （especially in case of resonance） and noise. To avoid this, it is important to predict the natural...The end windings of generators are excited to vibrations due to electromagnetic forces which can cause severe damage （especially in case of resonance） and noise. To avoid this, it is important to predict the natural frequencies and modes of the end windings with finite elements during the design process. Hence, a material model of the complete stator bar is necessary. This paper shows the development of such a material model. The composite structure of a stator bar is quite complex and makes it impossible to provide a quick calculation of the eigenvalues. That is the reason for using a suitable, homogeneously, geometry based solid model. Special attention was paid to the experimental determination of the material characteristics of the orthotropic composite space brackets. The numerical results have been evaluated against measurements. Eigenvalues, Young＇s modulus, and shear modulus have been experimentally investigated.展开更多
Aiming at prestressed anchor cable frame in the presence of reinforcement landslide problem, through the selection of test points, the paper study and tested soil pressure, frame internal force and prestress losses un...Aiming at prestressed anchor cable frame in the presence of reinforcement landslide problem, through the selection of test points, the paper study and tested soil pressure, frame internal force and prestress losses under prestressed anchor cable frame beam, reveal the law of internal force distribution, and provides a theory basis for the rational design of prestressed anchor cable in landslide.展开更多
We present the technical report for treat- ment of comminuted fracture of the capitate with ligamentotaxis. The base of third metacarpal was found to be fractured with comminution of the capitate. The decrease in carp...We present the technical report for treat- ment of comminuted fracture of the capitate with ligamentotaxis. The base of third metacarpal was found to be fractured with comminution of the capitate. The decrease in carpal height index and comminution of the third metacar- pal base lead to dilemma between conservative treatment and surgical management of this particular injury. The sur- gical management was chosen to maintain the carpal height index of the wrist to prevent the late degenerative changes.The patient was applied with external fixator in distraction mode expanning the wrist joint for six weeks, and the wrist was mobilised after removal of the fixator. It is shown that the external fixator in distraction mode expanning the wrist joint is a good alternative method for treatment of capitate fracture.展开更多
基金Project(2014QNA50) supported by Fundamental Research Funds for the Central Universities,ChinaProject(51404248) supported by the National Natural Science Foundation of ChinaProject supported by the Priority Academic Program Development(PAPD) of Jiangsu Higher Education Institutions,China
文摘The installation of a back-wall guard-board is the key to successfully supporting underground retreating roadways in coal mines. Based on the coordinate support principle, and using an I-shaped steel support for the surrounding rock, a mechanical model was developed for the stability of the roadway support and surrounding rock. Analysis of the bearing capacity of the roof back-wall guard-board and modelling of the equations for the maximum deflection and the maximum compressive stress of the top and side beams of the I-shaped steel support were undertaken. Simultaneously, the model was used to calculate and analyse the stability of the top and side beams of the I-shaped steel support structure and analyse the criteria for their stability. The results provide a reliable theoretical basis for the judgment of the stability of the surrounding rock and support structure. The theoretical evaluation results are consistent with field data. Finally, the key support parameters of the top and side beams of the I-shaped steel support structure and the variation of the maximum deflection and the maximum compressive stress as affected by the influence of the guard-board length were investigated. It is concluded that, as the back-board length increases, the maximum compressive stress in the top beam of the I-shaped steel support increases while the compressive stress in the side beam decreases. The results show that the accuracy of judgment of the stability of a supported retreating roadway is improved, providing guidance for the design of such typical I-shaped steel support and back-board structures.
文摘Dinoflagellate is one of the primitive eukaryotes, whose nucleus may represent one of the transition stages from prokaryotic nucleoid to typical eukaryotic nucleus. Using selective extraction together with embeddment - free section and whole mount electron microscopy, a delicate nuclear matrix filament network was shown, for the first time, in dinoflagellate Crypthecodinium cohnii nucleus. Chromosome residues are connected with nuclear matrix filaments to form a complete network spreading over the nucleus. Moreover, we demonstrated that the dinoflagellate chromosome retains a protein scaffold after the depletion of DNA and soluble proteins. This scaffold preserves the characteristic morphology of the chromosome. Two dimensional elec-trophoreses indicated that the nuclear matrix and chromosome scaffold are mainly composed of acidic proteins. Our results demonstrated that a framework similar to the nuclear matrix and chromosome scaffold in mammalian cells appears in this primitive eukaryote,suggesting that these structures may have been originated from the early stages of eukaryote evolution.
文摘The end windings of generators are excited to vibrations due to electromagnetic forces which can cause severe damage （especially in case of resonance） and noise. To avoid this, it is important to predict the natural frequencies and modes of the end windings with finite elements during the design process. Hence, a material model of the complete stator bar is necessary. This paper shows the development of such a material model. The composite structure of a stator bar is quite complex and makes it impossible to provide a quick calculation of the eigenvalues. That is the reason for using a suitable, homogeneously, geometry based solid model. Special attention was paid to the experimental determination of the material characteristics of the orthotropic composite space brackets. The numerical results have been evaluated against measurements. Eigenvalues, Young＇s modulus, and shear modulus have been experimentally investigated.
文摘Aiming at prestressed anchor cable frame in the presence of reinforcement landslide problem, through the selection of test points, the paper study and tested soil pressure, frame internal force and prestress losses under prestressed anchor cable frame beam, reveal the law of internal force distribution, and provides a theory basis for the rational design of prestressed anchor cable in landslide.
文摘We present the technical report for treat- ment of comminuted fracture of the capitate with ligamentotaxis. The base of third metacarpal was found to be fractured with comminution of the capitate. The decrease in carpal height index and comminution of the third metacar- pal base lead to dilemma between conservative treatment and surgical management of this particular injury. The sur- gical management was chosen to maintain the carpal height index of the wrist to prevent the late degenerative changes.The patient was applied with external fixator in distraction mode expanning the wrist joint for six weeks, and the wrist was mobilised after removal of the fixator. It is shown that the external fixator in distraction mode expanning the wrist joint is a good alternative method for treatment of capitate fracture.
