3,168 research outputs found
Conservative implicit schemes for the full potential equation applied to transonic flows
Implicit approximate factorization techniques (AF) were investigated for the solution of matrix equations resulting from finite difference approximations to the full potential equation in conservation form. For transonic flows, an artificial viscosity, required to maintain stability in supersonic regions, was introduced by an upwind bias of the density. Two implicit AF procedures are presented and their convergence performance is compared with that of the standard transonic solution procedure, successive line overrelaxation (SLOR). Subcritical and supercritical test cases are considered. The results indicate that the AF schemes are substantially faster than SLOR
Valuation of Safety-Branded and Traceable Free Range Chicken in Ha Noi: Results from a Field Experiment
The valuation of traceable or safety-branded food by consumers in developing countries affected by diseases such as avian influenza, or with food safety issues in general, is very difficult to identify. Products that have safety-branding are not common, and food is usually purchased by bargaining at informal markets. However, valuation of traceability has important implications for livestock disease policies as well as agricultural sector development. Through developing a short-term certified supply chain for free range chicken in Hanoi, we were able to conduct a combined field experiment and detailed household survey to measure the valuation of this type of poultry. We find that consumers in urban Hanoi on average have a welfare gain of about 66 million for such characteristics.field experiments, avian influenza, Vietnam, food safety, Demand and Price Analysis, Food Consumption/Nutrition/Food Safety, C93, D12, Q13, Q18,
Credible Duck Food Safety Certification: Results of a Field Experiment
Food Security and Poverty,
A Bose-Einstein Approach to the Random Partitioning of an Integer
Consider N equally-spaced points on a circle of circumference N. Choose at
random n points out of on this circle and append clockwise an arc of
integral length k to each such point. The resulting random set is made of a
random number of connected components. Questions such as the evaluation of the
probability of random covering and parking configurations, number and length of
the gaps are addressed. They are the discrete versions of similar problems
raised in the continuum. For each value of k, asymptotic results are presented
when n,N both go to infinity according to two different regimes. This model may
equivalently be viewed as a random partitioning problem of N items into n
recipients. A grand-canonical balls in boxes approach is also supplied, giving
some insight into the multiplicities of the box filling amounts or spacings.
The latter model is a k-nearest neighbor random graph with N vertices and kn
edges. We shall also briefly consider the covering problem in the context of a
random graph model with N vertices and n (out-degree 1) edges whose endpoints
are no more bound to be neighbors
Predictions for the First Parker Solar Probe Encounter
We examine Alfv\'en Wave Solar atmosphere Model (AWSoM) predictions of the
first Parker Solar Probe (PSP) encounter. We focus on the 12-day closest
approach centered on the 1st perihelion. AWSoM (van der Holst et al., 2014)
allows us to interpret the PSP data in the context of coronal heating via
Alfv\'en wave turbulence. The coronal heating and acceleration is addressed via
outward-propagating low-frequency Alfv\'en waves that are partially reflected
by Alfv\'en speed gradients. The nonlinear interaction of these
counter-propagating waves results in a turbulent energy cascade. To apportion
the wave dissipation to the electron and anisotropic proton temperatures, we
employ the results of the theories of linear wave damping and nonlinear
stochastic heating as described by Chandran et al. (2011). We find that during
the first encounter, PSP was in close proximity to the heliospheric current
sheet (HCS) and in the slow wind. PSP crossed the HCS two times, namely at
2018/11/03 UT 01:02 and 2018/11/08 UT 19:09 with perihelion occuring on the
south of side of the HCS. We predict the plasma state along the PSP trajectory,
which shows a dominant proton parallel temperature causing the plasma to be
firehose unstable.Comment: 16 pages, 5 figures; accepted for publication in the Astrophysical
Journal Letter
Making Anti-de Sitter Black Holes
It is known from the work of Banados et al. that a space-time with event
horizons (much like the Schwarzschild black hole) can be obtained from 2+1
dimensional anti-de Sitter space through a suitable identification of points.
We point out that this can be done in 3+1 dimensions as well. In this way we
obtain black holes with event horizons that are tori or Riemann surfaces of
genus higher than one. They can have either one or two asymptotic regions.
Locally, the space-time is isometric to anti-de Sitter space.Comment: LaTeX, 10 pages, 6 postscript figures, uses epsf.te
Innovative Design Concept for the New Bangkok International Airport, NBIA
Thermal and visual comfort for the occupants of a
room are not defined by air temperature only, but also
radiation with its three components solar radiation,
daylight and heat radiation has to be taken into account
(among other factors such as humidity, air speed and
occupant activity and clothing levels). In hot climates the
optimization of room comfort is a challenging task due
to the high solar radiation over the whole year.
In intelligent buildings new material developments
are applied optimizing the building envelope in an
integral building design process. New solutions for
weather, noise and heat protection are developed, where
building envelope and installed mechanical equipment
work together creating optimal comfort at minimum
energy consumption.
This approach was used in the design of the New
Bangkok International Airport, NBIA to develop an
optimized building concept in a design team comprising
the architects, structural and mechanical engineers,
HVAC, acoustic and climate engineers
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