A series solution for surface motion amplification due to underground group cavities for incident plane P waves is derived by Fourier-Bessel series expansion method. It is shown that underground group cavities signifi...A series solution for surface motion amplification due to underground group cavities for incident plane P waves is derived by Fourier-Bessel series expansion method. It is shown that underground group cavities significantly am-plify the surface ground motion nearby. It is suggested that the effect of subways on ground motion should be con-sidered when the subways are planned and designed.展开更多
Let M(2)be the group of rigid motions of the plane.The Fourier transform and the Piancherel formula on M(2)can be explicitly given by the general group representation theory.Using this fact.we establish a kind of unce...Let M(2)be the group of rigid motions of the plane.The Fourier transform and the Piancherel formula on M(2)can be explicitly given by the general group representation theory.Using this fact.we establish a kind of uncertainty principle on M(2).The result can easily be generalized to higher dimensional cases.An application of the result yields an uncertainty principle on the Euclidean spaces obtained by R.S.Strichartz.展开更多
Amplification of in-plane seismic ground motion by underground group cavities in layered half-space is studied both in frequency domain and time domain by using indirect boundary element method （IBEM）, and the effec...Amplification of in-plane seismic ground motion by underground group cavities in layered half-space is studied both in frequency domain and time domain by using indirect boundary element method （IBEM）, and the effect of cavity interval and spectrum of incident waves on the amplification are studied by numerical examples. It is shown that there may be large interaction between cavities, and group cavities with certain intervals may have significant amplification to seismic ground motion. The amplification of PGA （peak ground acceleration） and its PRS （peak response spectrum） can be increased up to 45.2% and 84.4%, for an example site in Tianjin, under the excitation of Taft wave and E1 Centro wave; and group cavities may also affect the spectra of the seismic ground motion. It is suggested that the effect of underground group cavities on design seismic ground motion should be considered.展开更多
Group-invariant solutions to certain plane curve motions in Euclidean and centro-affine geometries areobtained. The behavior of some solutions is also presented.
As the continuation study on amplification of in-plane seismic ground motion by underground group cavities in layered half-space, this study extends to the case of poroelastic half-space with dry poroelastic and satur...As the continuation study on amplification of in-plane seismic ground motion by underground group cavities in layered half-space, this study extends to the case of poroelastic half-space with dry poroelastic and saturated poroelastic soil layers. The influence of poroelastic layers on the amplification of seismic ground motion is studied both in frequency domain and time domain using indirect boundary element method （IBEM）. It is shown that for the example of a saturated poroelastic site in Tianjin under the excitation of Taft wave and E1 Centro wave, the amplification of seismic ground motion in poroelastic case is slightly smaller than that in the elastic case, and the amplification of PGA （peak ground acceleration） and its PRS （peak response spectrum）.. can be increased up to 38.8% and 64.6%; the predominant period of response spectra in poroelastic case becomes shorter to some extent compared with that in the elastic case. It is suggested that the effect of underground group cavities in poroelastic half-space on design seismic ground motion should be considered.展开更多
Finding damage inside pipes is important for the inspection of complex pipes used in nuclear power plants and chemical plants. A number of studies have investigated the mechanisms of an actuator with an electric cable...Finding damage inside pipes is important for the inspection of complex pipes used in nuclear power plants and chemical plants. A number of studies have investigated the mechanisms of an actuator with an electric cable to provide locomotion through various devices in complex pipes. An in-pipe robot capable of movement in narrow complex pipes has not yet been developed. In the present paper, we propose a globular magnetic actuator group that exhibits a very high thrust force and is capable of free reversible motion in complex pipes. Two actuators of the same size and characteristics are coupled by the magnetic connection method, which generates almost no mechanical loss. The globular magnetic actuator group capable of reversible motion through elongation and contraction of eight shape-memory-alloy (SMA) coils was fabricated. Experimental results indicate that the prototype actuator group is able to climb at a rate of 29 mm/s in a straight pipe while pulling a load mass of 48 g. In addition, the average speeds for two patterns of movement in a complex pipe with several curved sections and step sections were measured. The prototype actuator group is able to move in a complex pipe at an average speed of over 30 mm/s. This actuator group has several possible applications, including inspection using a micro-camera and pipe maintenance.展开更多
It is shown that the Pinney equation, Ermakov systems, and their higher-order generalizations describeself-similar solutions of plane curve motions in centro-affine and affine geometries.
基金Supported by National Natural Science Foundation of China (50378063), Excellent Young Teachers Program of MOE and SRF for ROCS, MOE.
文摘A series solution for surface motion amplification due to underground group cavities for incident plane P waves is derived by Fourier-Bessel series expansion method. It is shown that underground group cavities significantly am-plify the surface ground motion nearby. It is suggested that the effect of subways on ground motion should be con-sidered when the subways are planned and designed.
文摘Let M(2)be the group of rigid motions of the plane.The Fourier transform and the Piancherel formula on M(2)can be explicitly given by the general group representation theory.Using this fact.we establish a kind of uncertainty principle on M(2).The result can easily be generalized to higher dimensional cases.An application of the result yields an uncertainty principle on the Euclidean spaces obtained by R.S.Strichartz.
基金supported by National Natural Science Foundation of China under grant No. 50978183Tianjin Key Project for Applied Basic Research under grant No. 12JCZDJC29000
文摘Amplification of in-plane seismic ground motion by underground group cavities in layered half-space is studied both in frequency domain and time domain by using indirect boundary element method （IBEM）, and the effect of cavity interval and spectrum of incident waves on the amplification are studied by numerical examples. It is shown that there may be large interaction between cavities, and group cavities with certain intervals may have significant amplification to seismic ground motion. The amplification of PGA （peak ground acceleration） and its PRS （peak response spectrum） can be increased up to 45.2% and 84.4%, for an example site in Tianjin, under the excitation of Taft wave and E1 Centro wave; and group cavities may also affect the spectra of the seismic ground motion. It is suggested that the effect of underground group cavities on design seismic ground motion should be considered.
文摘Group-invariant solutions to certain plane curve motions in Euclidean and centro-affine geometries areobtained. The behavior of some solutions is also presented.
基金supported by National Natural Science Foundation of China under grant No. 50978183Key Project for Applied Basic Research of Tianjin Municipality under Grant No. 12JCZDJC29000
文摘As the continuation study on amplification of in-plane seismic ground motion by underground group cavities in layered half-space, this study extends to the case of poroelastic half-space with dry poroelastic and saturated poroelastic soil layers. The influence of poroelastic layers on the amplification of seismic ground motion is studied both in frequency domain and time domain using indirect boundary element method （IBEM）. It is shown that for the example of a saturated poroelastic site in Tianjin under the excitation of Taft wave and E1 Centro wave, the amplification of seismic ground motion in poroelastic case is slightly smaller than that in the elastic case, and the amplification of PGA （peak ground acceleration） and its PRS （peak response spectrum）.. can be increased up to 38.8% and 64.6%; the predominant period of response spectra in poroelastic case becomes shorter to some extent compared with that in the elastic case. It is suggested that the effect of underground group cavities in poroelastic half-space on design seismic ground motion should be considered.
文摘Finding damage inside pipes is important for the inspection of complex pipes used in nuclear power plants and chemical plants. A number of studies have investigated the mechanisms of an actuator with an electric cable to provide locomotion through various devices in complex pipes. An in-pipe robot capable of movement in narrow complex pipes has not yet been developed. In the present paper, we propose a globular magnetic actuator group that exhibits a very high thrust force and is capable of free reversible motion in complex pipes. Two actuators of the same size and characteristics are coupled by the magnetic connection method, which generates almost no mechanical loss. The globular magnetic actuator group capable of reversible motion through elongation and contraction of eight shape-memory-alloy (SMA) coils was fabricated. Experimental results indicate that the prototype actuator group is able to climb at a rate of 29 mm/s in a straight pipe while pulling a load mass of 48 g. In addition, the average speeds for two patterns of movement in a complex pipe with several curved sections and step sections were measured. The prototype actuator group is able to move in a complex pipe at an average speed of over 30 mm/s. This actuator group has several possible applications, including inspection using a micro-camera and pipe maintenance.
文摘It is shown that the Pinney equation, Ermakov systems, and their higher-order generalizations describeself-similar solutions of plane curve motions in centro-affine and affine geometries.
