A simple graph G on n vettices is said to be a simple MCD-graph if G has no two cyties having the same length and has the maximum possible number of edges.Two results of the number of cy cles in G are given by introdu...A simple graph G on n vettices is said to be a simple MCD-graph if G has no two cyties having the same length and has the maximum possible number of edges.Two results of the number of cy cles in G are given by introdueing the Concept of a path decomposition and by them,the following theorem is proved:If G is a simple MCD-graph,then G is not a 2-connected planar graph and for all n except seven integer,G is not a 2-connected graph on n vertices containing a subgraph homeomor phic to K_4.展开更多
A proven beam-track contact model was used to analyze the track-structure interaction of CWR (continuously welded track) on bridge. Considering the impact of adjacent bridges, the tower-cable-track-beam-pier-pile fini...A proven beam-track contact model was used to analyze the track-structure interaction of CWR (continuously welded track) on bridge. Considering the impact of adjacent bridges, the tower-cable-track-beam-pier-pile finite element model of the cable-stayed bridge was established. Taking a bridge group including 40-32m simply-supported beam and (32+80+112)m single-tower cable-stayed bridge and 17-32m simply-supported beam on the Kunming-Shanghai high-speed railway as an example, the characteristics of CWR longitudinal force on the cable-stayed bridge were studied. It is shown that adjacent bridges must be considered in the calculation of the track expansion force and bending force on cable-stayed bridge. When the span amount of adjacent bridges is too numerous, it can be simplified as six spans; the fixed bearing of adjacent simply-supported beams should be placed on the side near the cable-stayed bridge; the track expansion device should be set at the bridge tower to reduce the track force near the bridge abutment.展开更多
Compared with gentle dip long-wall caving,the length of a working face in fully-mechanized top-coal caving for extremely steep and thick seams is short,while its horizontal section is high with increasing production.B...Compared with gentle dip long-wall caving,the length of a working face in fully-mechanized top-coal caving for extremely steep and thick seams is short,while its horizontal section is high with increasing production.But the caving ratio is low,which might result in some disasters,such as roof falls,induced by local and large area collapse of the top coal in a working face and dangers induced by gas accumulation. After the development of cracks and weakening of the coal body,the tall,broken section of the top coal（a granular medium）of an extremely steep seam（over 60°）shows clear characteristics of nonlinear movement.We have thoroughly analyzed the geological environment and mining conditions of an excavation disturbed zone.Based on the results from a physical experiment of large-scale 3D modeling and coupling simulation of top coal-water-gas,we conclude that the weakened top coal can be regarded as a non-continuous medium.We used a particle flow code program to compare and analyze migration processes and the movements of a 30 m high section top coal over time before and after weakening of an extremely steep seam in the Weihuliang coal mine.The results of our simulation, experiment and monitoring show that pre-injection of water and pre-splitting blasting improve caving ability and symmetrical caving,relieve space for large area dynamic collapse of top coal,prolong migration time of noxious gases and release them from the mined out area and so achieve safety in mining.展开更多
As an orientation measurement system,north-finder has been playing a significant role in both military and civilian fields of orientation and control.In this paper,to deal with drawbacks in the conventional north-find...As an orientation measurement system,north-finder has been playing a significant role in both military and civilian fields of orientation and control.In this paper,to deal with drawbacks in the conventional north-finding systems,a dynamic strategy based on continuous rotation modulation to measure the rotational angular velocity of the earth is proposed.By modeling the dynamic error,optimizing the process constraint and estimating dynamic noise,a method combining delay compensation and hardware adjustment,and a constrained adaptive Kalman filter(CAKF)algorithm are designed for the north-finding strategy.According to simulation and experiments,the proposed algorithm can achieve the high-precision north-finding with robust and anti-noise performance.展开更多
In this paper,the optimum supercontinuum(SC)spectrum generation in a dispersion decreasing fiber is presented.Three normalized parameters for the pump pulse and SC fiber are introduced.It is found that the shape of an...In this paper,the optimum supercontinuum(SC)spectrum generation in a dispersion decreasing fiber is presented.Three normalized parameters for the pump pulse and SC fiber are introduced.It is found that the shape of an SC spectrum is uniquely specified by the input soliton order,the normalized dispersion slope and the normalized effective fiber length.For a pumping condition with a given input soliton order and a given normalized dispersion slope,by optimizing the normalized effective fiber length,the residual spectral peak in the SC spectrum can be suppressed effectively,and a broad SC spectrum with optimum spectral flatness can be obtained.展开更多
文摘A simple graph G on n vettices is said to be a simple MCD-graph if G has no two cyties having the same length and has the maximum possible number of edges.Two results of the number of cy cles in G are given by introdueing the Concept of a path decomposition and by them,the following theorem is proved:If G is a simple MCD-graph,then G is not a 2-connected planar graph and for all n except seven integer,G is not a 2-connected graph on n vertices containing a subgraph homeomor phic to K_4.
基金Project(51178469) supported by the National Natural Science Foundation of China
文摘A proven beam-track contact model was used to analyze the track-structure interaction of CWR (continuously welded track) on bridge. Considering the impact of adjacent bridges, the tower-cable-track-beam-pier-pile finite element model of the cable-stayed bridge was established. Taking a bridge group including 40-32m simply-supported beam and (32+80+112)m single-tower cable-stayed bridge and 17-32m simply-supported beam on the Kunming-Shanghai high-speed railway as an example, the characteristics of CWR longitudinal force on the cable-stayed bridge were studied. It is shown that adjacent bridges must be considered in the calculation of the track expansion force and bending force on cable-stayed bridge. When the span amount of adjacent bridges is too numerous, it can be simplified as six spans; the fixed bearing of adjacent simply-supported beams should be placed on the side near the cable-stayed bridge; the track expansion device should be set at the bridge tower to reduce the track force near the bridge abutment.
基金Financial support for this work,provided by the National Natural Science Foundation of China(No.11002021)the Doctoral Subject Foundation of the Ministry of Education of China(No.20070008012)the National High Technology Research and Development Program(No.2008AA062104)
文摘Compared with gentle dip long-wall caving,the length of a working face in fully-mechanized top-coal caving for extremely steep and thick seams is short,while its horizontal section is high with increasing production.But the caving ratio is low,which might result in some disasters,such as roof falls,induced by local and large area collapse of the top coal in a working face and dangers induced by gas accumulation. After the development of cracks and weakening of the coal body,the tall,broken section of the top coal（a granular medium）of an extremely steep seam（over 60°）shows clear characteristics of nonlinear movement.We have thoroughly analyzed the geological environment and mining conditions of an excavation disturbed zone.Based on the results from a physical experiment of large-scale 3D modeling and coupling simulation of top coal-water-gas,we conclude that the weakened top coal can be regarded as a non-continuous medium.We used a particle flow code program to compare and analyze migration processes and the movements of a 30 m high section top coal over time before and after weakening of an extremely steep seam in the Weihuliang coal mine.The results of our simulation, experiment and monitoring show that pre-injection of water and pre-splitting blasting improve caving ability and symmetrical caving,relieve space for large area dynamic collapse of top coal,prolong migration time of noxious gases and release them from the mined out area and so achieve safety in mining.
基金National Natural Science Foundation of China(No.61733012)。
文摘As an orientation measurement system,north-finder has been playing a significant role in both military and civilian fields of orientation and control.In this paper,to deal with drawbacks in the conventional north-finding systems,a dynamic strategy based on continuous rotation modulation to measure the rotational angular velocity of the earth is proposed.By modeling the dynamic error,optimizing the process constraint and estimating dynamic noise,a method combining delay compensation and hardware adjustment,and a constrained adaptive Kalman filter(CAKF)algorithm are designed for the north-finding strategy.According to simulation and experiments,the proposed algorithm can achieve the high-precision north-finding with robust and anti-noise performance.
基金supported by the Guangdong Natural Science Fund(No.1414050001224)the National Instrumentation Program(No.2012YQ14000511)the Guangdong Science and Technology Program(No.2012B090600009)
文摘In this paper,the optimum supercontinuum(SC)spectrum generation in a dispersion decreasing fiber is presented.Three normalized parameters for the pump pulse and SC fiber are introduced.It is found that the shape of an SC spectrum is uniquely specified by the input soliton order,the normalized dispersion slope and the normalized effective fiber length.For a pumping condition with a given input soliton order and a given normalized dispersion slope,by optimizing the normalized effective fiber length,the residual spectral peak in the SC spectrum can be suppressed effectively,and a broad SC spectrum with optimum spectral flatness can be obtained.
