By using site observation data and establishing 3D model using ANSYS software, this paper has discussed the strain change of stratum stress during process of jacking-in and the impact of machine head on ground surface under different frontal resistances. Analysis of the two cases shows that soil pressure reaches its maximum point when the soil is right above machine head, and soil stress will grad...... hiện toàn bộ
A conspiracy attack is proposed to show that Wang-Li's scheme is insecure, because anyt or more group members can impersonate othert members to sign any message without holding the responsibility. To avoid the conspiracy attack, this paper presents a new (t, n) threshold signature scheme with traceable signers.