Critical Behavior of a Three-State Potts Model on a Voronoi Lattice

We use the single-histogram technique to study the critical behavior of the three-state Potts model on a (random) Voronoi-Delaunay lattice with size ranging from 250 to 8000 sites. We consider the effect of an exponential decay of the interactions with the distance,$J(r)=J_0\exp(-ar)$, with $a>0$, and observe that this system seems to have critical exponents $\gamma$ and $\nu$ which are different from the respective exponents of the three-state Potts model on a regular square lattice. However, the ratio $\gamma/\nu$ remains essentially the same. We find numerical evidences (although not conclusive, due to the small range of system size) that the specific heat on this random system behaves as a power-law for $a=0$ and as a logarithmic divergence for $a=0.5$ and $a=1.0$Comment: 3 pages, 5 figure

Predicting the cost of the consequences of a large nuclear accident in the UK

Nuclear accidents have the potential to lead to significant off-site effects that require actions to minimise the radiological impacts on people. Such countermeasures may include sheltering, evacuation, restrictions on the sale of locally-grown food, and long-term relocation of the population amongst others. Countries with nuclear facilities draw up emergency preparedness plans, and put in place such provisions as distributing instructions and iodine prophylaxis to the local population. Their plans are applied in simulated exercises on a regular basis. The costs associated with emergency preparedness and the safety provisions to reduce the likelihood of an accident, and/or mitigate the consequences, are justified on the basis of the health risks and accident costs averted. There is, of course, only limited actual experience to indicate the likely costs so that much of the costing of accidents is based on calculations. This paper reviews the methodologies used, in particular the approach that has been developed in the UK, to appraise the costs of a hypothetical nuclear accident. Results of analysing a hypothetical nuclear accident at a fictitious reactor site within the United Kingdom are discussed in relation to the accidents at Three Mile Island 2, Chernobyl and Fukushima Dai-ichi

Bayesian modeling of neural net emulators

This is a Whitepaper submitted to the 2017 DOE ASCR Applied Math Meeting. It contains a proposal to develop verification and validation technologies for neural networks, that can serve as useful emulators of computationally-expensive PDE-based models. These emulators can be used in many-query applications such as global sensitivity analysis, Bayesian calibration and estimation of model-form errors

Final LDRD report : the physics of 1D and 2D electron gases in III-nitride heterostructure NWs.

The proposed work seeks to demonstrate and understand new phenomena in novel, freestanding III-nitride core-shell nanowires, including 1D and 2D electron gas formation and properties, and to investigate the role of surfaces and heterointerfaces on the transport and optical properties of nanowires, using a combined experimental and theoretical approach. Obtaining an understanding of these phenomena will be a critical step that will allow development of novel, ultrafast and ultraefficient nanowire-based electronic and photonic devices

Analysis of Drought Impacts on Electricity Production in the Western and Texas Interconnections of the United States.

Electricity generation relies heavily on water resources and their availability. To examine the interdependence of energy and water in the electricity context, the impacts of a severe drought to assess the risk posed by drought to electricity generation within the western and Texas interconnections has been examined. The historical drought patterns in the western United States were analyzed, and the risk posed by drought to electricity generation within the region was evaluated. The results of this effort will be used to develop scenarios for medium- and long-term transmission modeling and planning efforts by the Western Electricity Coordination Council (WECC) and the Electric Reliability Council of Texas (ERCOT). The study was performed in response to a request developed by the Western Governors Association in conjunction with the transmission modeling teams at the participating interconnections. It is part of a U.S. Department of Energy-sponsored, national laboratory-led research effort to develop tools related to the interdependency of energy and water as part of a larger interconnection-wide transmission planning project funded under the American Recovery and Reinvestment Act. This study accomplished three main objectives. It provided a thorough literature review of recent studies of drought and the potential implications for electricity generation. It analyzed historical drought patterns in the western United States and used the results to develop three design drought scenarios. Finally, it quantified the risk to electricity generation for each of eight basins for each of the three drought scenarios and considered the implications for transmission planning. Literature on drought impacts on electricity generation describes a number of examples where hydroelectric generation capacity has been limited because of drought but only a few examples of impact on thermoelectric generation. In all documented cases, shortfalls of generation were met by purchasing power from the market, albeit at higher prices. However, sufficient excess generation and transmission must be available for this strategy to work. Although power purchase was the most commonly discussed drought mitigation strategy, a total of 12 response strategies were identified in the literature, falling into four main categories: electricity supply, electricity demand response, alternative water supplies, and water demand response. Three hydrological drought scenarios were developed based on a literature review and historical data analysis. The literature review helped to identify key drought parameters and data on drought frequency and severity. Historical hydrological drought data were analyzed for the western United States to identify potential drought correlations and estimate drought parameters. The first scenario was a West-wide drought occurring in 1977; it represented a severe drought in five of the eight basins in the study area. A second drought scenario was artificially defined by selecting the conditions from the 10th-percentile drought year for each individual basin; this drought was defined in this way to allow more consistent analysis of risk to electricity generation in each basin. The final scenario was based upon the current low-flow hydro modeling scenario defined by WECC, which uses conditions from the year 2001. These scenarios were then used to quantify the risk to electricity generation in each basin. The risk calculations represent a first-order estimate of the maximum amount of electricity generation that might be lost from both hydroelectric and thermoelectric sources under a worst-case scenario. Even with the conservative methodology used, the majority of basins showed a limited amount of risk under most scenarios. The level of risk in these basins is likely to be amenable to mitigation by known strategies, combined with existing reserve generation and transmission capacity. However, the risks to the Pacific Northwest and Texas Basins require further study. The Pacific Northwest is vulnerable because of its heavy reliance on hydroelectric generation. Texas, conversely, is vulnerable because of its heavy dependence on thermoelectric generation, which relies on surface water for cooling, along with the fact that this basin seems to experience more severe drought events on average. Further modeling analysis will be performed in conjunction with the modeling teams at the participating interconnections (WECC and ERCOT) to explore the transmission implications of the drought scenarios in more detail. Given the first-order nature of this analysis, more detailed study of the potential impacts of drought on electricity generation is recommended. Future analyses should attempt to model the potential impacts of drought at the power-plant level, including potential mitigation strategies; include the effects of drought duration; understand the impacts of climate change; and consider economic impacts

Ten Years of Manufacturing R and D in PVMaT -- Technical Accomplishments, Return on Investments, and Where We Go Next

The Photovoltaic Manufacturing Technology Project has been conducting cost-shared R and D with industry for ten years. Objectives of this project are to improve photovoltaic manufacturing processes and products and to lower manufacturing costs. The majority of the efforts have been module related. Results in terms of automation, yield, and throughput have provided a significant reduction in direct manufacturing costs. Some of these results are detailed, and a measure of the return due to these efforts is discussed. Finally, technical directions for future activities are identified

Objective Method for Selecting Outdoor Reporting Conditions for Photovoltaic Performance

Outdoor performance of photovoltaic modules and systems depends on prevailing conditions at the time of measurement. Outdoor test conditions must be relevant to device performance and readily attainable. Flat-plate, nonconcentrator PV device performance is reported with respect to fixed conditions referred to as Standard Reporting Conditions (SRC) of 1 kW/m{sup 2} plane of array total irradiance, 25 C device temperature, and a reference spectral distribution at air mass 1.5 under certain atmospheric conditions. We report a method of analyzing historical meteorological and irradiance data to determine the range of outdoor environmental parameters and solar irradiance components that affect solar collector performance when the SRC 1 kW/m{sup 2} total irradiance value occurs outdoors. We used data from the 30 year U.S. National Solar Radiation Data Base (NSRDB) , restricting irradiance conditions to within +/- 25 W/m{sup 2} of 1 kW/m{sup 2} on a solar tracking flat-plate collector. The distributions of environmental parameter values under these conditions are non-Gaussian and site dependent. Therefore the median, as opposed to the mean, of the observed distributions is chosen to represent appropriate outdoor reporting conditions. We found the average medians for the direct beam component (834 W/m{sup 2}), ambient temperature (24.4 C), total column water vapor (1.4 cm), and air mass (1.43) are near commonly used SRC values. Average median wind speed (4.4 m/s) and broadband aerosol optical depth (0.08) were significantly different from commonly used values