AGRICULTURAL PLANNING EXPERT: A MODEL OF FARM ENTERPRISE SELECTION

Agricultural Planning Expert is a software model designed for advising small-scale farmers in southern Maryland. Choosing farm enterprises is modelled as consisting of four activities: suggesting enterprises for consideration, investigating the suitability of enterprises, allocating resources to suitable enterprises, and controlling the overall direction of an advising session.Farm Management,

Time-dependent Robin boundary conditions in the dynamical Casimir effect

Motivated by experiments in which moving boundaries are simulated by time-dependent properties of static systems, we discuss the model of a massless scalar field submitted to a time-dependent Robin boundary condition (BC) at a static mirror in 1+1 dimensions. Using a perturbative approach, we compute the spectral distribution of the created particles and the total particle creation rate, considering a thermal state as the initial field state.Comment: 10 pages, 3 figures. To appear in proceedings of Conference on Quantum Field Theory under the Influence of External Condition

Some boundary effects in quantum field theory

We have constructed a quantum field theory in a finite box, with periodic boundary conditions, using the hypothesis that particles living in a finite box are created and/or annihilated by the creation and/or annihilation operators, respectively, of a quantum harmonic oscillator on a circle. An expression for the effective coupling constant is obtained showing explicitly its dependence on the dimension of the box.Comment: 12 pages, Late

O pastoreio em áreas de carvalhal. Um ensaio na Serra de Nogueira

O presente trabalho visa o estudo da utilização das áreas de carvalhal para o pastoreio. Sendo o fogo tradicionalmente usado pelos pastores da região c sendo o gado ovino o mais abundante, os ensaios efectuados procuraram criar situações que pudessem ser mais facilmente assimiladas e reproduzidas em larga escala, pelo que a combinação fogo controlado de Inverno- pastoreio com ovinos foi seleccionada. Os ensaios decorreram na Serra da Nogueira, num povoamento de Quercus pyrenaica em cujo sub-bosque dominavam a sua própria regeneração natural , a giesta (Cytisus scoparius) e gramíneas (Agrostis curtisii, etc.) tendo consistido num pastoreio de duas áreas, uma testemunha e outra submetida a fogos controlados. A disponiblidade de alimento num sub-bosque típico de carvalhal não é negligenciável (3.59 ton. M.S./ha), por outro lado na zona regularmente tratada com fogo controlado a disponibilidade total de alimento foi menor (2.89 ton. M.S./ha), mas a percentagem de folhas de carvalho desceu para cerca de 40% enquanto que as gramíneas c as folhas de outras arbustivas aumentaram significativamente. Estes dois tipos de alimentos, juntamente com as folhas e raminhos de giesta, apresentarem os maiores índices de preferência, poderemos concluir pelo interesse da utilização do fogo controlado na gestão dos carvalhais com o objectivo do pastoreio por ovinos

Nitrogen response studies of intercropped sorghum with pigeonpea

To study the N response of sorghum (Sorghum bicolor) intercropped with pigeon pea (Cajanus cajan), 3 experiments were conducted in Vertisols. In experiment 1, sole sorghum (180 000 plant/ha), sole pigeon pea (40 000 plants/ha) and 3 intercrop population treatments (40: 40, 80: 80 and 120: 120% of sole optimum) were sown as main plots with 4 levels of N (0, 40, 80 and 120 kg/ha) only to sorghum as subplots. It is concluded that intercropped and sole sorghum responded similarly to applied N. Different sorghum populations in the intercrop performed similarly. Pigeon pea did not seem to be contributing any N to its companion sorghum. Sorghum at higher N levels had a greater effect on pigeon pea yield. Both crops did equally well at 45 cm and 90 cm when grown as sole crop