The mercury emissions of coal combustion and the mercury concentration of coals in China were studied. The average mercury concentration of coals is 0.22 mg/kg. By founding a monitor program, we measured the mercury emission factors of coal-fired boilers, which are from 64.0% to 78.2%. On the basis of other data, we estimated that the total amount of mercury emission from coal combustion was 302.87 t in 1995, including 213.8 t into atmosphere and 89.07 t into ash and cinder. The results show that 2493.8 t of mercury was emitted into the atmosphere during the coal combustion process from 1978 to 1995, and the mercury emission intensity is higher in Beijing, Shanghai, and Tianjin.

No abstract

In this article, we give conditions on parameters k, l that the generalized eigenvalue problem x″″ + kx″ + lx = λh(t)x, 0 < t <1, x(0) = x(1) = x′(0) = x′(1) = 0 possesses an infinite number of simple positive eigenvalues {λ k } ∞ k=1 and to each eigenvalue there corresponds an essential unique eigenfunction ψ k which has exactly k -1 simple zeros in (0,1) and is positive near 0. It follows that we consider the fourth-order twopoint boundary value problem x″″ + kx″ + lx = f(t,x), 0 < t <1, x(0) = x(1) = x′(0) = x′ (1) = 0, where f(t, x) C([0,1] × ℝ, ℝ) satisfies f(t, x)x >0 for all x ≠ 0, t [0,1] and lim |x| 0 f(t,x)/x = a(t), lim |x| +∞ f(t,x)/x = b(t) or lim x -∞ f(t,x)/x = 0 and lim x +∞ f(t,x)/x = c(t) for some a(t), b(t), c(t) C([0,1], (0,+∞)) and t [0,1]. Furthermore, we obtain the existence and multiplicity results of nodal solutions for the above problem. The proofs of our main results are based upon disconjugate operator theory and the global bifurcation techniques. MSC (2000): 34B15.

No abstract