Structures at elevated temperatures: How long will they last?

In principle, questions about the behaviour of high-temperature structures can be answered by analysis in conjunction with material creep properties. However, because of the wide range of geometries in use, simplified methods have been developed which avoid lengthy computations yet isolate the important factors controlling component behaviour. This paper describes one approach which is to define a reference stress such that the component life is equal to the life of a simple specimen tested at the reference stress. A substantial body of work has shown that the reference stress can often be established quite simply even for complex components containing cracks. The approach then provides a simple framework for assessing structures which operate at high temperatures.     

A generic approach for developing process-level hydrologic modeling components

Component software architectures offer an alternative approach for building large, complex hydrologic modeling systems. In contrast to more traditional software paradigms (i.e. procedural or object-oriented approaches), using component-based approaches allows individuals to construct autonomous modeling units that can be linked together through shared boundary conditions during a simulation run. One of the challenges in component-based modeling is designing a simple yet robust means for authoring model components. We address this challenge by presenting an approach for efficiently creating standards-based, process-level hydrologic modeling components. Using this approach, a hydrologic process is implemented as a modeling component by (1) authoring a configuration file that defines the properties of the component and (2) creating a class with three methods that define the pre-run, runtime, and post-run behavior of the modeling component. We present the design and implementation of this approach, which we call the Simple Model Wrapper (SMW), and demonstrate how it can be applied to create an Open Modeling Interface (OpenMI)-compliant modeling component for a basic hydrologic process.     

A cytokine mRNA-destabilizing element that is structurally and functionally distinct from A+U-rich elements

The control of mRNA stability is crucial to the regulation of cytokine expression. We describe here a novel, potent destabilizing element found in the 3' untranslated region of granulocyte colony-stimulating factor mRNA. This element, which appears to require at least one stem-loop structure, we term the stem-loop destabilizing element (SLDE). Functionally equivalent elements appear to also exist in the interleukin 2 and interleukin 6 mRNAs. The SLDE is functionally distinct from the A+U-rich elements, which are also present in these and other cytokine mRNAs, because it destabilizes a chimeric mRNA in a tumor cell line in which A+U-rich elements do not function. In addition, the effect of the SLDE is insensitive to calcium ionophore and is therefore regulated independently of A+U destabilizing elements. The existence of two distinct mRNA-destabilizing elements provides an additional mechanism for the differential regulation of cytokine expression.     

Amplitude and phase measurements of forward-scattered microwave radiation from waterdrops

An experiment to determine the forward-scattering complex amplitude functions of waterdrops supported in a vertical wind tunnel is described. The measuring system is calibrated using a metal sphere of accurately known diameter. Measurements at 11 GHz on waterdrops in the range 1.6?3.1 mm radius are compared with theoretical values obtained by Oguchi using the point-matching technique.     

Asymptotic stabilization of a class of uncertain composite systems

A class of stabilizing, generalized feedback controls is presented for a class of uncertain dynamical systems. The uncertain systems are based on a composite prototype system consisting of two nonlinearly coupled subsystems, with a non-asymptotically-stabilizable linearization. To encompass all possible realizations of uncertainty, a problem formulation based on differential inclusions is adopted. The generalized feedback controls, described in terms of set-valued maps, have practical analogues in the form of discontinuous feedback controls. An intrinsic element of the control strategy is designed to render a prescribed nonlinear manifold, containing the state origin, invariant and globally finite-time attractive. For each uncertain system, the generalized feedback controls guarantee global asymptotic stability of the zero state.     

STRATIGRAPHY AND RESERVOIR POTENTIAL OF THE MESOZOIC KHORAT GROUP, NE THAILAND: Part 1: Stratigraphy and Sedimentary Evolution

In this paper, the sedimentology, petrography and biostratigraphy of the Nam Phong Formation and the overlying Mesozoic Khorat Group in NE Thailand are described. Data were gathered during extensive studies in the field (about 100 outcrop localities were investigated) and from laboratory analyses of over 500 surface samples.
The Nam Phong Formation is dated accurately for the first time as late Norian to Rhaetian, while the Phra Wihan, Sao Khua, Phu Phan and Khok Kruat Formations (of the Khorat Group) are reassigned to the Early Cretaceous (Berriasian to Aptian) on the basis of new palynological data. The age of the intervening Phu Kradung Formation, which is conventionally assigned to the Lower Jurassic, is probably Late Jurassic or Early Cretaceous, although this cannot be determined with confidence. Changes in provenance between the Nam Phong Formation and the overlying Phu Kradung Formation suggest a possible sedimentary hiatus. Palaeocurrent data suggest that sediments were mainly sourced from the north and east.
Part 1 of this paper describes the sedimentology and biostratigraphy of these units; Part 2, which is scheduled to appear in the April, 1996 issue of this Journal, reports on their diagenesis and reservoir quality.