Management information systems for the horticultural firm

The development of micro computers has highlighted the need for accurate information at a property level in order to have suitable input data for planning and decision making. This review reveals limited research in developing horticultural information systems and a disappointing response from the farming community in various countries to a generalised recording scheme. Attempts to impose formalised recording schemes have suffered from lack of involvement of growers in the planning stage and limited · contact between advisers and growers after the information has been collated and returned. The Horticultural Management Information System developed by Carlsson and his co-workers in Sweden has received ready acceptance by growers. It seems that Calrsson is succeeding because he has compiled his information system with a close and frequent consultancy approach. The conclusions drawn in this review suggest that the simple intimate approach to information systems initially, lead to grower interest and increasing enthusiasm

Decision making in horticultural firms

Before looking at decision making in the horticultural firm in detail, it is desirable to briefly describe the types of decisions, that are made along with the nature of the environment within which the horticultural firm typically exists. Decision making in horticultural firms is characterised by a diversity of decision types which maybe categorised for convenience on the basis of time scales. In the long term, decisions need to be made concerning the legal form of the business structure, the crop plan choice, scale of operation and location of operation. In the medium term will be decisions concerning investment in equipment, machines and storage facilities. As a result of these medium and long term decisions, there is a requirement in the short term for decisions relating to crop production methods and husbandry matters (e.g. pest and disease control), labour, harvesting and marketing. Marketing policy may in fact be a medium term decision requiring short term decisions for its implementation. Set-out in Figure 1 is one version of an abbreviated decision making cycle (Rae, 1977). The horticultural firm, especially for small family operations, is characterised by a close relationship between the operations of the household and the firm. Both entities consume funds and labour resources and may be in conflict with one another. Horticultural firms maybe legally structured in several ways such as sole ownership, partnerships, companies or as a co-operative. While these forms of business structure determine responsibility for consequences of management decisions, they may not necessarily be an accurate reflection of who makes particular decisions. Having considered briefly the system of the horticultural firm and the types of decisions it is involved in making, we now briefly consider the environment within which the firm exists, as it will markedly influence decision making

Dewetting of thin films on heterogeneous substrates: Pinning vs. coarsening

We study a model for a thin liquid film dewetting from a periodic heterogeneous substrate (template). The amplitude and periodicity of a striped template heterogeneity necessary to obtain a stable periodic stripe pattern, i.e. pinning, are computed. This requires a stabilization of the longitudinal and transversal modes driving the typical coarsening dynamics during dewetting of a thin film on a homogeneous substrate. If the heterogeneity has a larger spatial period than the critical dewetting mode, weak heterogeneities are sufficient for pinning. A large region of coexistence between coarsening dynamics and pinning is found.Comment: 4 pages, 4 figure

Stability analysis of polarized domains

Polarized ferrofluids, lipid monolayers and magnetic bubbles form domains with deformable boundaries. Stability analysis of these domains depends on a family of nontrivial integrals. We present a closed form evaluation of these integrals as a combination of Legendre functions. This result allows exact and explicit formulae for stability thresholds and growth rates of individual modes. We also evaluate asymptotic behavior in several interesting limits.Comment: 12 pages, 3 figures, Late

Extending ballistic graphene FET lumped element models to diffusive devices

In this work, a modified, lumped element graphene field effect device model is presented. The model is based on the "Top-of-the-barrier" approach which is usually valid only for ballistic graphene nanotransistors. Proper modifications are introduced to extend the model's validity so that it accurately describes both ballistic and diffusive graphene devices. The model is compared to data already presented in the literature. It is shown that a good agreement is obtained for both nano-sized and large area graphene based channels. Accurate prediction of drain current and transconductance for both cases is obtained

Asymptotic theory for a moving droplet driven by a wettability gradient

An asymptotic theory is developed for a moving drop driven by a wettability gradient. We distinguish the mesoscale where an exact solution is known for the properly simplified problem. This solution is matched at both -- the advancing and the receding side -- to respective solutions of the problem on the microscale. On the microscale the velocity of movement is used as the small parameter of an asymptotic expansion. Matching gives the droplet shape, velocity of movement as a function of the imposed wettability gradient and droplet volume.Comment: 8 fig

Noise-induced switching between vortex states with different polarization in classical two-dimensional easy-plane magnets

In the 2-dimensional anisotropic Heisenberg model with XY-symmetry there are non-planar vortices which exhibit a localized structure of the z-components of the spins around the vortex center. We study how thermal noise induces a transition of this structure from one polarization to the opposite one. We describe the vortex core by a discrete Hamiltonian and consider a stationary solution of the Fokker-Planck equation. We find a bimodal distribution function and calculate the transition rate using Langer's instanton theory (1969). The result is compared with Langevin dynamics simulations for the full many-spin model.Comment: 15 pages, 4 figures, Phys. Rev. B., in pres