816 research outputs found
A method to include machine manufacturing energy in energy balance analysis
Manufacturing and also maintenance and repair energy demand is hard to find, there are only few research data available and this data seems no to be very reliable. Manufacturing energy damand can be calculated by estimating the mean tractor usage and calculating the manufacturing energy per consumed fuel liter. In this way it is easy to estimate the manufacturing energy, because it can be calculated with the liter/ha figures. Fuel consumption for different works in the form of liter/ha can easily be found in literature
Mapping the three-body system - decay time and reversibility
In this paper we carry out a quantitative analysis of the three-body systems
and map them as a function of decaying time and intial conguration, look at
this problem as an example of a simple deterministic system, and ask to what
extent the orbits are really predictable. We have investigated the behavior of
about 200 000 general Newtonian three body systems using the simplest initial
conditions. Within our resolution these cover all the possible states where the
objects are initially at rest and have no angular momentum. We have determined
the decay time-scales of the triple systems and show that the distribution of
this parameter is fractal in appearance. Some areas that appear stable on large
scales exhibit very narrow strips of instability and the overall pattern,
dominated by resonances, reminds us of a traditional Maasai warrior shield.
Also an attempt is made to recover the original starting conguration of the
three bodies by backward integration. We find there are instances where the
evolution to the future and to the past lead to different orbits, in spite of
time symmetric initial conditions. This implies that even in simple
deterministic systems there exists an Arrow of Time.Comment: 8 pages, 9 figures. Accepted for publication in MNRAS. Includes
low-resolution figures. High-resolution figures are available as PNG
Collisional dynamics around binary black holes in galactic centers
We follow the sinking of two massive black holes in a spherical stellar
system where the black holes become bound under the influence of dynamical
friction. Once bound, the binary hardens by three-body encounters with
surrounding stars. We find that the binary wanders inside the core, providing
an enhanced supply of reaction partners for the hardening. The binary evolves
into a highly eccentric orbit leading to coalescence well beyond a Hubble time.
These are the first results from a hybrid ``self consistent field'' (SCF) and
direct Aarseth N-body integrator (NBODY6), which combines the advantages of the
direct force calculation with the efficiency of the field method. The code is
designed for use on parallel architectures and is therefore applicable to
collisional N-body integrations with extraordinarily large particle numbers (>
10^5). This creates the possibility of simulating the dynamics of both globular
clusters with realistic collisional relaxation and stellar systems surrounding
supermassive black holes in galactic nuclei.Comment: 38 pages, 13 figures, submitted to ApJ, accepted, revised text and
added figure
Long-Term Evolution of Massive Black Hole Binaries. II. Binary Evolution in Low-Density Galaxies
We use direct-summation N-body integrations to follow the evolution of binary
black holes at the centers of galaxy models with large, constant-density cores.
Particle numbers as large as 400K are considered. The results are compared with
the predictions of loss-cone theory, under the assumption that the supply of
stars to the binary is limited by the rate at which they can be scattered into
the binary's influence sphere by gravitational encounters. The agreement
between theory and simulation is quite good; in particular, we are able to
quantitatively explain the observed dependence of binary hardening rate on N.
We do not verify the recent claim of Chatterjee, Hernquist & Loeb (2003) that
the hardening rate of the binary stabilizes when N exceeds a particular value,
or that Brownian wandering of the binary has a significant effect on its
evolution. When scaled to real galaxies, our results suggest that massive black
hole binaries in gas-poor nuclei would be unlikely to reach gravitational-wave
coalescence in a Hubble time.Comment: 13 pages, 8 figure
Sairaanhoitovakuutuksen korvaamien yksityisten terveyspalvelujen käytön kehitys ja hintavertailu
Baltic Ecological Recycling Agriculture and Society (BERAS project) - a case of Juva milk system
The aim of the study was to determine the potential, impact and prerequisites of localization and enhanced recycling in a rural food system, illustrated by the case of Juva milk. An interdisciplinary scenario based on the increase of local, organic milk to 50 % of milk comsumption was created and the sustainability was compared, on the basis of the statistics and data collected from the actors, with the present milk system
Unleashing Potato’s Potential in Sudan. A Scoping Mission Report
CIP, in partnership with Orgamed Farms Ltd and Stokman Rozen Kenya conducted a scoping exercise to assess
private interest in seed production, and the potato sector and partners in general. This scoping report maps
partners relevant to potato development and provides an agro-ecological and socio-economic assessment of
potential areas for developing potato sector considering differing profiles of value chains: rural, food security
focused, urban, commercially driven. The scoping exercise shows great potential to uplift the potato sector to
transform the various value chains, and ultimately contribute to development goals to improve livelihoods of
Sudanese. Limited access to costly seed is the principal bottle to potato sector development, with the majority
of certified seed being imported and sold at 1.37 to 1.87 USD/kg, whereas commercial seed in East African
countries ranges from 0.5 to 0.6 USD/kg. As a result, market prices for potato for consumption are high, having
been observed as much as 2.20 USD/kg in rural markets, prohibitive for rural households to afford as a food
security crop. High production costs affecting supply prevent potato from reaching its potential to provide
income and economic development from household to regional levels, and contribute to food security at the
national level. At the same time, urbanization, change of dietary habits and removal of wheat import
subsidizes continue to drive demand of potato in Sudan. The scoping report will advise pathways to support
potato to reach its potential through creating opportunities for diverse partners, including national and
regional institutions, private sector, national NGOs, farmer organizations and microfinance institutions
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