The nature of taphonomic overprint affecting the fossil records of the regular echinoid Families Cidaridae, Diadematidae, Toxopneustidae and Echinometridae is investigated using a synthesis of actualistic and literature-derived data. The actualistic portion of this study focuses on the following extant members of the four families: Eucidaris tribuloides, Diadema antillarum, Tripneustes ventricosus and Echinometra lucunter. Population censuses of these animals in tropical reef and near-reef environments demonstrate that the distribution of macro- and microscopic skeletal material does not reflect the distribution of the living fauna. Field experiments with freshly-killed carcasses of Eucidaris, Diadema and Echinometra indicate that loss of all organic tissue occurs within six days after death, reducing these echinoids to essentially bleached carcasses.
Stabilization of dynamical systems is a very important problem and has received great attention. The solution of such problems can be achieved for linear autonomous small scale (centralized) systems with specific parameters using the conventional control theory. This leads to the design of a centralized controller which determines the control actions based on the centralized structure. However, with the development of modern technology, the size and complexity of the systems are increasing everyday, stabilization of large scale systems using centralized techniques is therefore not feasible. And decentralized techniques are an attractive approach for large scale systems stabilization. Our objective in this research is to investigate the stability of linear nonautonomous large scale systems with uncertain parameters. Both feedback-free and feedback control systems will be studied. The technique is based upon using a Lyapunov function to disconnect and reassemble the subsystems in different ranges. So new criteria for studying and designing the finite-time or uniform stability can be developed. These criteria can also be used to design or estimate the convergence rate of the global system. In addition, since small scale (centralized) systems. Examples are given. Application and extensions are also discussed.
This research is an ethnographic study of literacy as a socially constructed process, literacy viewed as a part of the acquisition and transmission of culture. The focal population was a group of low SES high school students, most of whom were African American, and their children (ages 7 weeks to 4 years), several of whom were enrolled in a day care center housed within the large, urban high school their parents attended in a midwestern U.S. city. The research was an attempt to understand the kinds of literacy, specifically the types and amounts of reading and writing, that were a part of the home and school lives of the student/parents, and their parents, and a part of the home and day care lives of their children.
The temporal subdomain method based on the Ritz-Galerkin method is investigated as a method for the solution of space-time dependent neutron dynamics equations. In the temporal subdomain finite element method, the time domain is divided into subdomains and within each subdomain the unknown coefficients of the time dependent trial functions are determined by making the residual of an appropriate functional orthogonal to the step function.