Publications

Results 68701–68800 of 99,299

Search results

Jump to search filters

Development of a micro flow-through cell for high field NMR spectroscopy

Alam, Todd M.; Mcintyre, Sarah K.

A highly transportable micro flow-through detection cell for nuclear magnetic resonance (NMR) spectroscopy has been designed, fabricated and tested. This flow-through cell allows for the direct coupling between liquid chromatography (LC) and gel permeation chromatography (GPC) resulting in the possibility of hyphenated LC-NMR and GPC-NMR. The advantage of the present flow cell design is that it is independent and unconnected to the detection probe electronics, is compatible with existing commercial high resolution NMR probes, and as such can be easily implemented at any NMR facility. Two different volumes were fabricated corresponding to between {approx}3.8 and 10 {micro}L detection volume. Examples of the performance of the cell on different NMR instruments, and using different NMR detection probes were demonstrated.

More Details
TYPE SAND Report YEAR 2011
DOIOSTI

A nonlocal, ordinary, state-based plasticity model for peridynamics

Mitchell, John A.

An implicit time integration algorithm for a non-local, state-based, peridynamics plasticity model is developed. The flow rule was proposed in [3] without an integration strategy or yield criterion. This report addresses both of these issues and thus establishes the first ordinary, state-based peridynamics plasticity model. Integration of the flow rule follows along the lines of the classical theories of rate independent J{sub 2} plasticity. It uses elastic force state relations, an additive decomposition of the deformation state, an elastic force state domain, a flow rule, loading/un-loading conditions, and a consistency condition. Just as in local theories of plasticity (LTP), state variables are required. It is shown that the resulting constitutive model does not violate the 2nd law of thermodynamics. The report also develops a useful non-local yield criterion that depends upon the yield stress and horizon for the material. The modulus state for both the ordinary elastic material and aforementioned plasticity model is also developed and presented.

More Details
TYPE SAND Report YEAR 2011
DOIOSTI

Environmental Management System (EMS) objectives & targets : annual results summary %3CU%2B2013%3E FY10

Waffelaert, Pascale S.; Vetter, Douglas W.

Sandia National Laboratory/New Mexico's (SNL/NM) Environmental Management System is the integrated approach for members of the workforce to identify and manage environmental risks. Each fiscal year (FY) significant environmental aspects are identified and the environmental programs associated with them are charged with the task of routinely monitoring and measuring the objectives and targets that are designed to mitigate the impact of SNL/NM's operations on the environment. An annual summary of the results achieved towards meeting established objectives and targets provides a connection to and rational for annually revised significant aspects. The purpose of this document is to summarize the results achieved and documented in FY2010.

More Details
TYPE SAND Report YEAR 2011
DOIOSTI

Techniques to evaluate the importance of common cause degradation on reliability and safety of nuclear weapons

Darby, John L.

As the nuclear weapon stockpile ages, there is increased concern about common degradation ultimately leading to common cause failure of multiple weapons that could significantly impact reliability or safety. Current acceptable limits for the reliability and safety of a weapon are based on upper limits on the probability of failure of an individual item, assuming that failures among items are independent. We expanded the current acceptable limits to apply to situations with common cause failure. Then, we developed a simple screening process to quickly assess the importance of observed common degradation for both reliability and safety to determine if further action is necessary. The screening process conservatively assumes that common degradation is common cause failure. For a population with between 100 and 5000 items we applied the screening process and conclude the following. In general, for a reliability requirement specified in the Military Characteristics (MCs) for a specific weapon system, common degradation is of concern if more than 100(1-x)% of the weapons are susceptible to common degradation, where x is the required reliability expressed as a fraction. Common degradation is of concern for the safety of a weapon subsystem if more than 0.1% of the population is susceptible to common degradation. Common degradation is of concern for the safety of a weapon component or overall weapon system if two or more components/weapons in the population are susceptible to degradation. Finally, we developed a technique for detailed evaluation of common degradation leading to common cause failure for situations that are determined to be of concern using the screening process. The detailed evaluation requires that best estimates of common cause and independent failure probabilities be produced. Using these techniques, observed common degradation can be evaluated for effects on reliability and safety.

More Details
TYPE SAND Report YEAR 2011
DOIOSTI
Results 68701–68800 of 99,299
Results 68701–68800 of 99,299