Numerical Design Of Experiments Research Articles

Genetic algorithms for dynamic tuning of structures

A category of methods developed in the branch of artificial intelligence known as genetic algorithms is suggested for numerical estimation and experimental design of dynamic tuning and resonance limit state analysis in ultimate dynamic states of structures in civil engineering. The performance of a set of genetic algorithms is presented by using the application problems. The results indicate that genetic algorithms are promising tools for solving nonlinear optimization problems, even when the objective function is either discrete, nonconvex, mulitmodal or flat in shape. The applications are performed on the adoption of up-to-date vectorized numerical methods for wave propagation and ultimate transient dynamics problems and optoelectronical experimental approaches for resonance tuning of engineering structures and technologies submitted to limit state dynamic loads.

Inducing risk-neutral preferences: Further analysis of the data

The lottery payoff procedure does not successfully induce risk-neutral bidding behavior in first-price, sealedbid auctions. This conclusion follows from both ordinary-least-squares estimation with natural data and leastabsolute-deviation estimation with transformed data from numerous experimental designs. Lottery payoffs do not succeed in inducing behavior predicted from standard expected utility theory assumptions or from assumed utility from winning and/or income thresholds. In contrast, first-price auction experiments with monetary payoffs yield results that are consistent with general models of bidding in the independent private values information environment.

Secondary Instabilities in Langmuir Circulations

Finite-amplitude Langmuir circulation in the form of rolls parallel to the wind direction is shown to be subject to three-dimensional instability under certain circumstances. Density stratification is not required for instability to manifest. The preferred form of this secondary instability appears to be traveling waves propagating in the direction of the wind. These cause the rolls, and their surface windrows, to deviate from the wind direction by a small angle for which estimates are given. The results of the paper show the value of secondary stability results for the design of numerical experiments to simulate Langmuir circulation.

On the cold start problem in transient simulations with coupled atmosphere-ocean models

Finite computer resources force compromises in the design of transient numerical experiments with coupled atmosphere-ocean general circulation models which, in the case of global warming simulations, normally preclude a full integration from the undisturbed pre-industrial state. The start of the integration at a later time from a climate state which, in contrast to the true climate, is initially in equilibrium then induces a cold start error. Using linear response theory a general expression for the cold start error is derived. The theory is applied to the Hamburg CO2 scenario simulations. An attempt to estimate the global-mean-temperature response function of the coupled model from the response of the model to a CO2 doubling was unsuccessful because of the non-linearity of the system. However, an alternative derivation, based on the transient simulation itself, yielded a cold start error which explained the initial retardation of the Hamburg global warming curve relative to the IPCC results obtained with a simple box-diffusion-upwelling model. In the case of the sea level the behaviour of the model is apparently more linear. The cold start error estimations based on a CO2 doubling experiment and on an experiment with gradually increasing CO2 (scenario A) are very similar and explain about two thirds of the coupled model retardation relative to the IPCC results.

Design and Analysis of Numerical Experiments

Methods for the design and analysis of numerical experiments that are especially useful and efficient in multidimensional parameter spaces are presented. The analysis method, which is similar to kriging in the spatial analysis literature, fits a statistical model to the output of the numerical model. The method is applied to a fully nonlinear, global, equivalent-barotropic dynamical model. The statistical model also provides estimates for the uncertainty of predicted numerical model output, which can provide guidance on where in the parameter space to conduct further experiments, if necessary. The method can provide significant improvements in the efficiency with which numerical sensitivity experiments are conducted.

Synergistic Interactions between an Upper-Level Jet Streak and Diabatic Processes that Influence the Development of a Low-Level Jet and a Secondary Coastal Cyclone

A series of numerical simulations of the February 1979 Presidents Day cyclone is presented. The development of the low-level jet (LLJ) associated with the cyclone is described, and the mesoscale numerical model, initial analyses, and experimental design used in the study are discussed. Four numerical simulations are discussed and compared, including an adiabatic simulation that isolates the development of upper-level divergence along the axis of a subtropical jet streak and three other simulations that reveal the contributions of sensible and latent heat release in modifying lower-tropospheric wind fields and reducing the sea-level pressure. The formation of the LLJ is described through an evaluation of trajectories derived from the various model simulations. The effect of the LLJ on secondary cyclogenesis along the East Coast is described.

I. Computation of Bell Profiles Using Structural Optimization

This article describes the design of the profile for a major-third bell using structural optimization strategies. First a sequential linear programming method was used to find a prototype of the bell. The necessary analyses were done using the finite element method. Next, a fast analysis model was derived by numerical experimental design techniques. This analysis model led to the final geometry of the major-third bell.

Increased susceptibility of splenectomized mice to infection after exposure to an aerosolized suspension of type III Streptococcus pneumoniae.

Most reported experimental studies concerning the effect of splenectomy in animals have shown enhanced mortality from pneumococci injected either intravenously or intraperitoneally. We have developed a laboratory model in which mice are exposed to type III Streptococcus pneumoniae via an aerosolized atmosphere, thus closely approximating the route of human infection with this organism. Ninety-one male Swiss mice (mean weight 26 g) were divided into three approximately equal groups of control, sham-operated, and splenectomized animals. Two weeks later they were exposed for 30 min in individualized compartments within a confined chamber to an aerosolized atmosphere producing a uniform challenge of 5.9 X 10(9) colony-forming units per ml of pneumococci. A statistically significant increase (P less than 0.01) in mortality was demonstrated in the splenectomized group over the pooled sham-operated and control groups. The animal model used in these investigations can be applied to the study of infections acquired by the respiratory route in numerous experimental designs.

NORMAL HEAT SOURCES AND SINKS IN THE LOWER TROPOSPHERE IN WINTER

A synthesis is made of several published studies of the normal heat budget of the lower troposphere over the Northern Hemisphere in winter. Charts of heat sources and sinks are presented, based on two independent methods, one using the thermodynamic energy equation and the other a heat-balance procedure. Although there are differences in important details, both methods indicate that the horizontal scale of heating is the same as that of the normal lower-tropospheric temperature field, but that the field of heating is almost 90° out of phase with that of temperature. This result has an important bearing on the energy budget of the circulation. It is concluded that the heat-balance method is correct in indicating that there is a positive correlation between the normal temperature and heating fields. According to the energy transformation equations, this means that there is a positive transformation from heating to potential energy at the scale of the climatological long waves. This energy is directly available for maintaining these waves against friction. It is hoped that this study will be of some use in the design of numerical general circulation experiments, and as a basis of comparison with data from meteorological satellites.