Bifurcation characteristics of coal spontaneous combustion and analysis of critical state of gaseous reaction in a packed bed

The numerical model was presented for the coal combustion in the packed bed. The bifurcation characteristic of the ignition-extinction of solid-phase smoldering and tran- sition to flaming was studied for the packed bed of coal.One of the Frank-Kamenetskii parameter β_1 was selected as the control parameter.The computed results show that the bifurcation curve is obviously divided into two zones of solid-phase reaction and gas- phase reaction,and the total process of ignition-extinction presents twice bifurcation cha- racteristic.Moreover,the vanishing of critical state of ignition-extinction is studied.One of the transition points,ε_2=0.05,is numerically solved for the vanishing of critical state.The larger the value of ε_2 is,the easier the gas-phase can react.However,the combustion temperature will decrease with increasing ε_2.The other transition point α_2=0.53 is also ob- tained.With increasing the value of α_2,the combustion temperature of gas-phase reaction is close to the smoldering temperature of coal.When α_2 is infinite,the only reaction occur- ring is the smoldering combustion of solid-phase,and the gas-phase cannot react.

A novel line-symmetric Goldberg 6R linkage with bifurcation property

This paper proposes a novel reconfigurable Goldberg 6R linkage,conformed to the construction of variant serial Goldberg 6R linkage,while simultaneously satisfying the line-symmetric Bricard qualifications.The isomeric mechanism of this novel reconfigurable mechanism is obtained in combination with the isomerization method.The geometrically constrained conditions result in variable motion branches of the mechanism.Based on the singular value decomposition of the Jacobian matrix,the motion branches and branch bifurcation characteristics are analyzed,and the schematics of bifurcations in joint space is derived.This novel 6R linkage features one Goldberg 6R motion branch,two line-symmetric Bricard 6R motion branches,and one Bennett motion branch.With regards to the line-symmetric Bricard 6R motion branches,a similar function for the disassembly and recombination process can be achieved by reconstructing an intermediate configuration through bifurcation.Then,the isomerized generalized variant Goldberg 6R linkage is explicated in a similar way.Acting as a bridge,reconfigurability connects two families of overconstrained mechanisms.

STUDY ON THE STABILITY STRUCTURE OF SYNOPTIC SCALE SYSTEMS,THE BIFURCATION OF PHASE.PATH CHARACTERISTICS AND THE INFLUENCE OF THE TIME-OSCILLATION OF HEAT SOURCE

This paper discusses the stability structure and the bifurcation of phase path characteristics of synoptic scale system.The analytic results show that the catastrophe of the synoptic scale disturbance may be caused by the nonlinear effects of barotropic and baroclinic instability and advection of ambient large-scale flow.Also, foregoing nonlinear effects on the speed of development and decay of the system are presented in the processes deviating from or approaching to equilibrium state.It has been found that there is a resonance phenomenon between the time-oscillation of heat source and the atmospheric disturbance.