Interdicting a Nuclear‐Weapons Project

Operations Research, 57, pp. 866‐877.Center for Infrastructure Defense (CID) Paper.Operations Research, 57, pp. 866-877.The article of record as published may be located at http://dx.doi.org/10.1287/opre.1080.0643A “proliferator” seeks to complete a first small batch of fission weapons as quickly as possible, whereas an “interdictor” wishes to delay that completion for as long as possible. We develop and solve a max-min model that identifies resource- limited interdiction actions that maximally delay completion time of the proliferator’s weapons project, given that the proliferator will observe any such actions and adjust his plans to minimize that time. The model incorporates a detailed project-management (critical path method) submodel, and standard optimization software solves the model in a few minutes on a personal computer. We exploit off-the-shelf project-management software to manage a database, control the optimiza- tion, and display results. Using a range of levels for interdiction effort, we analyze a published case study that models three alternate uranium-enrichment technologies. The task of “cascade loading” appears in all technologies and turns out to be an inherent fragility for the proliferator at all levels of interdiction effort. Such insights enable policy makers to quantify the effects of interdiction options at their disposal, be they diplomatic, economic, or military

Rotação de culturas no sistema plantio direto em Tibagi (PR): II - Emissões de CO2 e N2O Crop rotation under no-tillage in Tibagi (Paraná State, Brazil): II - CO2 and N2O emissions

A atividade agrícola pode alterar a quantidade e qualidade da matéria orgânica do solo (MOS), resultando em emissões de dióxido de carbono (CO2) e óxido nitroso (N2O) do solo para a atmosfera. O sistema plantio direto (SPD) com a utilização de leguminosas em sistemas de rotação é uma estratégia que deve ser considerada tanto para o aumento da quantidade de MOS como para seu efeito na redução das emissões dos gases de efeito estufa. Com o objetivo de determinar os fluxos de gases do efeito estufa (CO2 e N2O) do solo, um experimento foi instalado em Tibagi (PR), em um Latossolo Vermelho distroférrico textura argilosa. Os tratamentos, dispostos em faixas não casualizadas com parcelas subdivididas, foram: sistema plantio direto por 12 anos com sucessões milho/trigo e soja/trigo (PD12 M/T e PD12 S/T, respectivamente) e por 22 anos (PD22 M/T e PD22 S/T, respectivamente). As emissões de CO2 do solo foram aproximadamente 20 % mais elevadas no PD22 em relação ao PD12. As emissões de CO2 apresentaram correlação significativa (R² = 0,85; p < 0,05) com a temperatura do solo, com emissões médias 40 % menores, registradas nos meses com temperaturas mais baixas. As emissões mais elevadas de N2O foram observadas após a colheita das culturas de verão, sobretudo na sucessão milho/trigo, em relação à sucessão soja/trigo. As emissões de N2O foram aproximadamente 25 % maiores após aplicação do fertilizante nitrogenado na cultura do trigo nas duas sucessões e apresentaram correlação significativa (R² = 0,88; p < 0,01) com o grau de saturação de água no solo (Sr %).<br>The agricultural activity can change the quantity and quality of soil organic matter (SOM), resulting in CO2 and N2O emissions from the soil. No-tillage (NT) with legume species in crop rotation is a strategy that should be considered not only to increase the SOM quantity, but also to reduce greenhouse gas emissions. The objective of this study was to determine the soil-atmosphere gas emissions with greenhouse effect (CO2 and N2O). For this purpose, an experiment was installed in Tibagi (Paraná State, Brazil), on a clayey Oxisol (Typic Hapludox). The treatments were conducted in non-random strips with subdivided plots: no-tillage crop successions corn/wheat and soybean/wheat (NT12 M/T and NT12 S/T, respectively) for 12 years and no-tillage (NT22 M/T and NT22 S/T, respectively) for 22 years. The CO2 soil emissions were nearly 20 % higher in NT22 than in NT12. The CO2 emissions were significantly correlated (R² = 0.85; p < 0.05) with soil temperature, with 40 % lower mean emissions in the months of minimal soil temperatures. Highest N2O emissions were observed after the summer crop harvest, mainly in corn/wheat compared to soybean/wheat succession. N2O emissions were approximately 25 % higher after N-fertilizer application to wheat in both crop successions, and were significantly correlated (R² = 0.88; p < 0.01) with soil water-filled pore space (Sr %)