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[en] The cost of space heating may soon increase due to rising fuel prices in international energy markets and the absence of federal and provincial energy security policies. This report examined the benefits and disadvantages of 2 approaches to assist those with limited incomes to meet heating requirements: (1) offering Low Income Fuel Assistance (LIFA) as a one-time payment during the heating season; and (2) the elimination of taxes for home heating fuels. The cost of home heating fuels and their impacts on consumers and governments were considered. A review of the Nova Scotia government's Keep the Heat program noted that the program was not responsive to increases in the price of home heating fuel, particularly if increases in a year exceeded the level of assistance. It was suggested that the removal of heating sales taxes could provide unnecessary windfalls to households with large homes, as well as windfall profits for landlords if savings were not passed on to tenants. Using Nova Scotia as a case study, an alternative support system was considered that guaranteed a set price for heating fuel for those in need. It was suggested that this approach could cost less than a lump-sum payment or the elimination of taxes on home-heating fuel. In addition, the approach would provide low-income consumers with predictable and affordable prices. It was concluded that as space heating energy costs continue to rise, all government fuel assistance programs run the risk of becoming larger and more costly. Other solutions included reducing Canada's dependence on fossil fuels through the use of solar energy; the reduction of residential energy demand; and the promotion of district heating. 26 refs., 9 tabs., 3 figs
[en] A Rayleigh-Taylor-like interface instability is studied in a compressible Brownian Yukawa fluid mixture on the 'molecular' scales of length and time of the individual particles. As a model, a two-dimensional phase-separated symmetric binary mixture of colloidal particles of type A and B with a fluid-fluid interface separating an A-rich phase from a B-rich phase is investigated, by means of Brownian computer simulations, when brought into non-equilibrium via a constant external driving field which acts differently on the different particles and perpendicular to the interface. Two different scenarios are observed which occur either for high or for low interfacial free energies as compared to the driving force. In the first scenario for high interfacial tension, the critical wavelength λc of the unstable interface modes is in good agreement with the classical Rayleigh-Taylor formula provided that dynamically rescaled values for the interfacial tension are used. The wavelength λc increases with time, representing an effect of self-healing of the interface due to a local density increase near the interface. The Rayleigh-Taylor formula is confirmed even if λc is of the order of a molecular correlation length. In the second scenario for very large driving forces as compared to the interfacial line tensions, on the other hand, the particles penetrate the interface easily due to the driving field and form microscopic lanes with a width different from the predictions of the classical Rayleigh-Taylor formula. The results are of relevance for phase-separating colloidal mixtures in a gravitational or electric field
[en] GPI Atlantic has developed a Genuine Progress Index (GPI) involving a new measure of sustainability, wellbeing and quality of life in order to better evaluate energy supply and demand by accounting for all benefits and costs including natural capital, social capital, human capital, and conventional produced capital. The executive summary provides an energy overview and presents indicators of energy sustainability including socio-economic, health and environmental and institutional indicators. Socio-economic indicators are organized across the following 6 areas of concern: reliability, affordability, employment; energy efficiency, energy consumption; and energy production and supply. Health and environmental trends examined include carbon monoxide; nitrogen oxide; sulphur dioxide; mercury; total particulate matter; volatile organic compounds; and greenhouse gas emissions. Trends over time are assessed to determine if energy use is becoming more or less sustainable. Institutional indicators are grouped according to several areas of concern, such as leading by example; creating societal change; reporting; and evaluation. The full cost of energy was then discussed using the underlying physical indicators. It was concluded that Nova Scotia is not making sufficient progress towards sustainability in its energy system, and that the production and use of energy are the leading causes of a number of serious environmental problems. Several recommendations are made for government to lead on a number of initiatives. 4 tabs
[en] A review is given on recent studies of charged colloidal suspensions and polyelectrolytes both in static and non-equilibrium situations. As far as static equilibrium situations are concerned, we discuss three different problems: 1) Sedimentation density profiles in charged suspensions are shown to exhibit a stretched non-bariometric wing at large heights and binary suspensions under gravity can exhibit an analog of the brazil-nut effect known from granular matter, i.e. the heavier particles settle on top of the lighter ones. 2) Soft polyelectrolyte systems like polyelectrolyte stars and microgels show an ultra-soft effective interaction and this results into an unusual equilibrium phase diagram including reentrant melting transitions and stable open crystalline lattices. 3) The freezing transition in bilayers of confined charged suspensions is discussed and a reentrant behaviour is obtained. As far as nonequilibrium problems are concerned, we discuss an interface instability in oppositely driven colloidal mixtures and discuss possible approaches to simulate electrokinetic effects in charged suspensions
[en] Highlights: • Out-of-phase limit cycle oscillations were simulated in a 4-channel systems model. • Rotating mode oscillations were observed both in standalone and coupled simulations. • A physical explanation was proposed for why rotating mode oscillations are favored. • Conclusion: the rotating mode is always favored from a thermal hydraulic standpoint. - Abstract: Previous neutronic/thermal-hydraulic (TH) coupled numerical simulations using full-core TRACE/PARCS and SIMULATE-3K boiling water reactor (BWR) models have shown evidence of a specific “rotating mode” behavior (steady rotation of the symmetry line, i.e. constant phase shift of approximately 90° between the first two azimuthal modes) in BWR out-of-phase limit cycle oscillations, regardless of initial conditions and even if the first two azimuthal modes have different natural frequencies. This suggests a nonlinear coupling between these modes; otherwise, the phase shift between these modes would change at a constant rate during the limit cycle. The previous paper (“Part 1”) presented a series of results to examine this rotating behavior with a reduced-order model. The goal of the present study is to provide additional analyses of the predicted rotating mode behavior using higher-fidelity numerical modeling, as well as a physical explanation for why this mode is favored over side-to-side or other oscillatory behaviors from a TH perspective. Results are presented using TRACE and TRACE/PARCS for a small number of parallel channels, which confirmed that the conclusions developed from the reduced-order model remain applicable when applying a full two-fluid, six-equation, finite-volume modeling approach. From these results, a physical explanation has been put forth to explain why the rotating symmetry line behavior is preferred from a TH standpoint, demonstrating that predominantly out-of-phase unstable systems are most unstable when the variation in the total inlet flow rate is minimized (which minimizes the effective single-phase to two-phase pressure drop ratio) and that the rotating mode is the most successful in minimizing this total flow rate variation as compared with the side-to-side case or any other oscillation pattern. The conclusion is that the rotating mode will be favored for any out-of-phase unstable system of parallel channels with no neutronic feedback or relatively weak neutronic feedback. Previous analyses have indicated that systems with sufficiently strong neutronic coupling may favor the side-to-side oscillation mode over the rotating mode; this topic is left as a subject of future investigation.
[en] The core simulator component of the Virtual Environment for Reactor Applications (Vera) that is being developed by the Consortium for the Advanced Simulation of Light Water Reactors (CASL) is coupled with the coolant chemistry code Mamba to model Crud induced power shift (CIPS). Cycle 7 of the Watts Bar Nuclear Power Station Unit 1 is simulated, and comparisons are made with measured boron concentrations, axial offset, and 3-D flux maps throughout the cycle. Cases are simulated with and without the effects of Crud to show the axial offset anomaly between measured and predicted results normally associated with CIPS. (Author)
[en] Highlights: • Out-of-phase oscillations were simulated in a 4-channel reduced-order model. • A novel approach was used to model thermal hydraulic channel coupling in the plena. • With little or no neutronic feedback, a rotating mode limit cycle was observed. • With strong neutronic feedback, a side-to-side limit cycle behavior was observed. - Abstract: Previous neutronic/thermal-hydraulic (TH) coupled numerical simulations using full-core TRACE/PARCS and SIMULATE-3K BWR models have shown evidence of a specific “rotating mode” behavior (steady rotation of the symmetry line, i.e. constant phase shift of approximately 90° between the first two azimuthal modes) in out-of-phase limit cycle oscillations, regardless of initial conditions and even if the first two azimuthal modes have different natural frequencies. This suggests a nonlinear coupling between these modes; otherwise, the phase shift between these modes would change at a constant rate during the limit cycle. The goal of the present work is to gain further insights on the rotating mode behavior using a simplified mathematical model which contains all of the important physics for this application while providing sufficient flexibility and simplicity to allow for in-depth understanding of the underlying phenomena. This was accomplished using a multi-channel, multi-modal reduced-order model, using a modification of the fixed pressure drop boundary condition to simulate channel coupling via the inlet and outlet plena, in order to destabilize the out-of-phase mode over the in-phase mode. Examination of the time-dependent solution of the nonlinear system showed a clear preference for rotating mode behavior in the four-channel model under stand-alone TH conditions and for conditions with weak neutronic feedback. When neutronic feedback was strengthened (i.e., larger reactivity feedback coefficients), the side-to-side mode (stationary symmetry line) was favored instead. Additional analyses using higher-fidelity numerical modeling, as well as a physical explanation for the rotating behavior seen in both sets of analyses, will be provided in a companion paper (“Part 2”).
[en] We discuss an effective spin Hamiltonian with biquadratic interaction for ferropnictide superconductors from the point of view of band structure theory and available experimental data. This model is consistent with electronic structure calculations and captures many observed magnetic properties, including the anisotropy of the exchange coupling, thin domain walls, and the crossover from first to second-order phase transition under doping. The parameters of the model are analyzed as a function of the local spin moment using first-principles calculations. Calculations show the biquadratic coupling is negative in stoichiometric KFe2Se2, and the phase diagram is extended into this region. We also consider magnetic short-range order and discuss the limitations of this model in comparison with experiment
[en] Vacuum-assisted breast biopsy / Mammotome HH '' R '' Breast Biopsy System/ is the milestone in the diagnosis of breast lesions. This system has proven to be as diagnostically reliable as open surgery, but without scarring, deformations and hospitalizations associated with an open procedure. The aim of our study was to assess the role and possibilities of using this biopsy in treatment of benign breast lesions like fibroadenoma. From 2001 to 2004, about 1118 Mammotome biopsies were performed in our Department. Among 445 Mammotome biopsies performed under US control there were 211 cases of fibroadenomas. Follow-up was performed in 156 patients with this result at 6 and 12 months after biopsy. In our study we took into considerations the size, localizations as well as performers. In 2002 there were 70.8% patients with total lesion excision, 16.7% with residual lesion and 12.5% women with hematomas or scars. In 2003-2004 there were more women with total lesion excision (84.3%), fewer residual tumors and other lesions. In future, Mammotome breast biopsy can replace scalpel, and will become an alternative method to open surgical excision of fibroadenomas. It is important especially in the cases of young women to prevent cosmetic deformations and scars. (author)