6,205 research outputs found
Organic dairy farming in Norway under the 100% organically produced feed requirement
The EU regulation governing organic production will require 100% organic feed in organic dairy systems from August 2005 compared with 85% currently in Norway. This study aimed to assess adjustments in resource use and financial impacts on organic dairy herds using a discrete stochastic programming model. Farm management effects of the regulatory change varied between farm types. For the two organic dairy systems examined, both having a milk quota of 100 000 litres but with varying farmland availability, the introduction of the 100% organic feed regulation resulted in an economic loss of approximately 6-8% of the net income compared to the current regime. The economic loss was mainly due to the considerable higher price of organic compared to conventional concentrates
Stochastic utility-efficient programming of organic dairy farms
Opportunities to make sequential decisions and adjust activities as a season progresses and more information becomes available characterise the farm management process. In this paper, we present a discrete stochastic two-stage utility efficient programming model of organic dairy farms, which includes risk aversion in the decision maker’s objective function as well as both embedded risk (stochastic programming with recourse) and non-embedded risk (stochastic programming without recourse). Historical farm accountancy data and subjective judgements were combined to assess the nature of the uncertainty that affects the possible consequences of the decisions. The programming model was used within a stochastic dominance framework to examine optimal strategies in organic dairy systems in Norway
Model for Anisotropic Directed Percolation
We propose a simulation model to study the properties of directed percolation
in two-dimensional (2D) anisotropic random media. The degree of anisotropy in
the model is given by the ratio between the axes of a semi-ellipse
enclosing the bonds that promote percolation in one direction. At percolation,
this simple model shows that the average number of bonds per site in 2D is an
invariant equal to 2.8 independently of . This result suggests that
Sinai's theorem proposed originally for isotropic percolation is also valid for
anisotropic directed percolation problems. The new invariant also yields a
constant fractal dimension for all , which is the same
value found in isotropic directed percolation (i.e., ).Comment: RevTeX, 9 pages, 3 figures. To appear in Phys.Rev.
Risk programming analysis with imperfect information
A Monte Carlo procedure is used to demonstrate the dangers of basing (farm) risk programming on only a few states of nature and to study the impact of applying alternative risk programming methods. Two risk programming formulations are considered, namely mean-variance (E,V) programming and utility efficient (UE) programming. For the particular example of a Norwegian mixed livestock and crop farm, the programming solution is unstable with few states, although the cost of picking a sub-optimal plan declines with increases in number of states. Comparing the E,V results with the UE results shows that there were few discrepancies between the two and the differences which do occur are mainly trivial, thus both methods gave unreliable results in cases with small samples
Sensitivity limits of a Raman atom interferometer as a gravity gradiometer
We evaluate the sensitivity of a dual cloud atom interferometer to the
measurement of vertical gravity gradient. We study the influence of most
relevant experimental parameters on noise and long-term drifts. Results are
also applied to the case of doubly differential measurements of the
gravitational signal from local source masses. We achieve a short term
sensitivity of 3*10^(-9) g/Hz^(-1/2) to differential gravity acceleration,
limited by the quantum projection noise of the instrument. Active control of
the most critical parameters allows to reach a resolution of 5*10^(-11) g after
8000 s on the measurement of differential gravity acceleration. The long term
stability is compatible with a measurement of the gravitational constant G at
the level of 10^(-4) after an integration time of about 100 hours.Comment: 19 pages, 20 figure
Observing Coherence Effects in an Overdamped Quantum System
It is usually considered that the spectrum of an optical cavity coupled to an
atomic medium does not exhibit a normal-mode splitting unless the system
satisfies the strong coupling condition, meaning the Rabi frequency of the
coherent coupling exceeds the decay rates of atom and cavity excitations. Here
we show that this need not be the case, but depends on the way in which the
coupled system is probed. Measurements of the reflection of a probe laser from
the input mirror of an overdamped cavity reveal an avoided crossing in the
spectrum which is not observed when driving the atoms directly and measuring
the Purcell-enhanced cavity emission. We understand these observations by
noting a formal correspondence with electromagnetically-induced transparency of
a three-level atom in free space, where our cavity acts as the absorbing medium
and the coupled atoms play the role of the control field
What's the Matter with Relatedness?
A core proposition of the resource-based view of the firm is that related diversification is more efficient than unrelated diversification. Nevertheless, the empirical evidence is usually described as mixed or unstable. We empirically examine three possible explanations for the nature of these findings. One is that they reflect measurement problems. Another is that they reflect a failure to take the resource-based view far enough in terms of recognizing firm heterogeneity. The third is that the resource-based view is misspecified: relatedness is not a significant determinant of efficiency. We use a detailed line-of-business sample to examine these three explanations. Our findings clearly indicate that the main problem is measurement, and we describe an approach to overcoming these problems
Relatedness and Acquirer Performance
Includes bibliographical references.Uncorrected proofWhile the strategic management literature suggests that related diversification
is superior to unrelated diversification, there is little evidence that
acquirers benefit from pursuing related targets. We argue that the empirical
literature is plagued by poor measures of relatedness. Moreover,
many empirical studies do not control adequately for the characteristics of
the market for corporate control. We argue that not only value creation,
but also value appropriation, depend on the relatedness of acquirer and
target. Using an improved measure of relatedness, we provide empirical
evidence that acquirer returns are positively and significantly correlated
with relatedness
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