“…However, conventional moment methods have the disadvantage that the shape of the particle size distribution must be speciÿed in advance to obtain closure of the equations (Pratsinis & Kim, 1989). This could be a limitation if size distributions at early stages of particle formation are to be studied, where bimodal distributions are often observed (Landgrebe & Pratsinis, 1990;Park, Lee, & Choi, 1999;Xiong & Pratsinis, 1991). To avoid specifying the shape of the distribution a priori, the quadrature method of moments (QMOM) developed by McGraw (1997) approximates the integral moments of the size distribution by an n-point Gaussian quadrature (Gordon, 1968;Hulburt & Katz, 1964).…”