Dynamic-light-scattering experiments on semidilute aqueous solutions of gelatin indicate three relaxation processes: an exponential for times less than -50 psec followed by a power law at intermediate time and then a stretched exponential at long time. The characteristic time of the stretched exponential diverges as the system evolves to a gel. The latter two relaxations can be explained in terms of an anomalous diffusion mechanism where the mean-square displacement behaves as {R')-lnt at intermediate time and (R~) -te with p(1 at late time. Length scales derivable from these diffusion mechanisms obey scaling, and it is proposed that P is related to the fracton density-of-states exponent and the fractal dimension of the gelatin molecules.PACS number(s): 82.70. Gg, 05.40. +j, 61.41.+e

We present dynamic light scattering data which show that aqueous gelatin gels display a power-law relaxation to a nonergodic background. In the pregel sol this power law is terminated by a stretched exponential which restores ergodicity and which has a q dependent characteristic time proportional to the viscosity. The power-law exponent is q dependent and related to a characteristic length in the gel. Except for the q dependences these behaviors are similar to the a and p relaxation behavior in glasses. It is proposed that the different q dependences of the gels and glasses is a result of different characteristic length scales.

We obtained the shear viscosity 7 and optical probe (67-nm polystyrene latex spheres) diffusion coefficient D in hydroxypropylcellulose (HPC)/water at temperatures T = 10,25, and 39 O C . Polymer samples had weight-average molar masses M of 139,146,415, and 1280 ma. Polymer Concentrations c ranged up to 40-100 g/L; 7 was as large as 1@-1@ CP in different systems. 7 has a stretched-experimental dependence on c at small c and power-law behavior at large c. D generally follows a stretched exponential DO exp(-ac') but is consistent with power-law behavior at large c. Individual spectra fit well to Williams-Watta forms A0 exp(-Ote). The dependence of a, v, 0, and @ on c, M, and Tis discussed.

No abstract

The benefits of applying multi-objective optimization (MOO) in building design have been increasingly recognized in recent decades. The existing or traditional computational design optimization (CDO) approaches mostly focus on optimization problem solving (OPS), as they often conduct optimizations directly by assuming the optimization problems in question are good enough. In contrast, the computational design exploration (CDE) approaches defined in this research mainly focus on optimization problem formulation (OPF), which are considered more essential and aim to achieve or ensure appropriate optimization problems before conducting optimizations. However, the application of the CDE is very limited especially in conceptual architectural design. The necessity of re-formulating original optimization problems and its potential impacts on optimization results are often overlooked or not emphasized enough. This paper proposes a new CDE approach that highlights the knowledge-supported re-formulation of a changeable initial optimization problem. It improves upon the traditional CDO approach by introducing a changeable initial OPF and inserting a CDE module. The changeable initial OPF allows expanding the dimensionality of an objective space and design space being investigated, and the CDE module can re-formulate the changeable optimization problem using the information and knowledge extracted from statistical analyses. To facilitate designers in achieving the proposed approach, an improved computational platform is used which combines parametric modeling software (including simulation plug-ins) and design optimization software. Assisted by the platform, the proposed approach is applied to the conceptual design of an indoor sports building that considers multidisciplinary performance criteria (including architecture-, climate-and structure-related criteria) and a wide range of geometric variations. Through the case study, this paper demonstrates the use of the proposed approach, verifies its benefits over the traditional method, and unveils the factors that may affect the behaviour of the proposed approach. Besides, it also shows the suitability of the computational platform used.

No abstract

No abstract

No abstract