Dynamics of Arctic and Sub-Arctic Climate and Atmospheric Circulation: Diagnosis of Mechanisms and Biases Using Data Assimilation (open access)

Dynamics of Arctic and Sub-Arctic Climate and Atmospheric Circulation: Diagnosis of Mechanisms and Biases Using Data Assimilation

This is the final report for DOE grant DE-FG02-07ER64434 to Eric DeWeaver at the University of Wisconsin-Madison. The overall goal of work performed under this grant is to enhance understanding of simulations of present-day climate and greenhouse gas-induced climate change. Enhanced understanding is desirable 1) as a prerequisite for improving simulations; 2) for assessing the credibility of model simulations and their usefulness as tools for decision support; and 3) as a means to identify robust behaviors which commonly occur over a wide range of models, and may yield insights regarding the dominant physical mechanisms which determine mean climate and produce climate change. A furthe objective is to investigate the use of data assimilation as a means for examining and correcting model biases. Our primary focus is on the Arctic, but the scope of the work was expanded to include the global climate system to the extent that research targets of opportunity present themselves. Research performed under the grant falls into five main research areas: 1) a study of data assimilation using an ensemble filter with the atmospheric circulation model of the National Center for Atmospheric Research, in which both conventional observations and observations of the refraction of radio waves from …
Date: January 19, 2010
Creator: DeWeaver, Eric T.
System: The UNT Digital Library
SUMMARY PLAN FOR BENCH-SCALE REFORMER AND PRODUCT TESTING TREATABILITY STUDIES USING HANFORD TANK WASTE (open access)

SUMMARY PLAN FOR BENCH-SCALE REFORMER AND PRODUCT TESTING TREATABILITY STUDIES USING HANFORD TANK WASTE

This paper describes the sample selection, sample preparation, environmental, and regulatory considerations for shipment of Hanford radioactive waste samples for treatability studies of the FBSR process at the Savannah River National Laboratory and the Pacific Northwest National Laboratory. The U.S. Department of Energy (DOE) Hanford tank farms contain approximately 57 million gallons of wastes, most of which originated during the reprocessing of spent nuclear fuel to produce plutonium for defense purposes. DOE intends to pre-treat the tank waste to separate the waste into a high level fraction, that will be vitrified and disposed of in a national repository as high-level waste (HLW), and a low-activity waste (LAW) fraction that will be immobilized for on-site disposal at Hanford. The Hanford Waste Treatment and Immobilization Plant (WTP) is the focal point for the treatment of Hanford tank waste. However, the WTP lacks the capacity to process all of the LAW within the regulatory required timeframe. Consequently, a supplemental LAW immobilization process will be required to immobilize the remainder of the LAW. One promising supplemental technology is Fluidized Bed Steam Reforming (FBSR) to produce a sodium-alumino-silicate (NAS) waste form. The NAS waste form is primarily composed of nepheline (NaAlSiO{sub 4}), sodalite (Nas[AlSiO{sub 4}]{sub …
Date: August 19, 2010
Creator: JB, DUNCAN
System: The UNT Digital Library
Design and Implementation of a Metadata-rich File System (open access)

Design and Implementation of a Metadata-rich File System

Despite continual improvements in the performance and reliability of large scale file systems, the management of user-defined file system metadata has changed little in the past decade. The mismatch between the size and complexity of large scale data stores and their ability to organize and query their metadata has led to a de facto standard in which raw data is stored in traditional file systems, while related, application-specific metadata is stored in relational databases. This separation of data and semantic metadata requires considerable effort to maintain consistency and can result in complex, slow, and inflexible system operation. To address these problems, we have developed the Quasar File System (QFS), a metadata-rich file system in which files, user-defined attributes, and file relationships are all first class objects. In contrast to hierarchical file systems and relational databases, QFS defines a graph data model composed of files and their relationships. QFS incorporates Quasar, an XPATH-extended query language for searching the file system. Results from our QFS prototype show the effectiveness of this approach. Compared to the de facto standard, the QFS prototype shows superior ingest performance and comparable query performance on user metadata-intensive operations and superior performance on normal file metadata operations.
Date: January 19, 2010
Creator: Ames, S; Gokhale, M B & Maltzahn, C
System: The UNT Digital Library