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Recent studies have shown that base-isolated objects with long fundamental natural periods are highly influenced by long-period earthquakes. These long-period waves result in large displacements for isolators, possibly leading to exceedance of the allowable displacement limits. Conventional isolation systems, in general, fail to resist such large displacements. This has prompted the need to modify conventional base isolation systems. The current work focuses on the development of an external device, comprising a unit of negative and positive springs, for improving the performance of conventional base isolation systems. This unit accelerates the change in the stiffness of the isolation system where the stiffness of the positive spring varies linearly in terms of the displacement response of the isolated objects. The target objects of the present study are small structures such as computer servers, sensitive instruments and machinery. Numerical studies show that the increase in the damping of the system and the slope of the linear function is effective in reducing the displacement response. An optimal range of damping values and slope, satisfying the stability condition and the allowable limits of both displacement and acceleration responses when the system is subjected to near-fault and long-period ground motions simultaneously, is proposed.

Bioenergy crops can provide a reliable and adequate supply of biomass feedstocks to support the bioenergy industry. However, promoting bioenergy crops would require major change in land use and management practices that can have long term socio-economic and environmental impacts. Therefore, it is important to evaluate potential opportunities and challenges presented by bioenergy crop production. We developed a multi-objective optimization model to analyze trade-offs among various components of bioenergy crop production to help make better production decisions. Our model integrated sustainability dimensions including social, economic and environmental factors for bioenergy crop production. As bioenergy crop production may incorporate various objectives, we ran the model by optimizing one objective at a time to measure the magnitude of change in one objective with respect to change in other objectives given a set of constraints. In addition, our model had the ability to assess how trade-offs would be affected by chancing preferences for different factors in the production decisions. The model was applied for a four-county study area in northern Kentucky and it provided a regional examination for the potential of bioenergy crops for energy production. The model can serve as an effective tool for making bioenergy production planning and management decisions.

Bioenergy crops are considered as potential biomass feedstocks to support the bioenergy industry in the southern US. Even though there are suitable areas to grow bioenergy crops, commercial scale production of bioenergy crops has not been established to meet the increasing energy demand. Establishing bioenergy crops in the region requires landowners&rsquo, participation and it is crucial to understand whether they intend to promote bioenergy crop production. This study evaluated landowners&rsquo, perception of bioenergy and their willingness to supply lands for bioenergy crops in northern Kentucky. A questionnaire survey of randomly selected landowners was administered in four selected counties. Results indicated that landowners&rsquo, land use decisions for bioenergy crop production were based on their current land management practices, socio-economic and environmental factors. Overall, there was a low willingness of landowners to participate in bioenergy crop production. Those who were interested indicated that a higher biomass price would be required to promote bioenergy crops on their land. This information could be useful to plan for policies that provide economic incentives to landowners for large-scale production of bioenergy crops in the study area and beyond. Further, results showed how landowners&rsquo, opinion on bioenergy affected their preferences for land use decisions. Younger landowners with positive attitude towards bioenergy were more willing to promote bioenergy crops. This information could be useful to develop outreach programs for landowners to encourage them to promote bioenergy crops in the study area.

This study used a spatially-explicit model to identify the amount and spatial distribution of economically feasible sites for establishing dedicated energy crops under various market and policy scenarios. A sensitivity analysis was performed for a biomass market with different discount rates and biomass prices as well as policy scenarios including propriety tax exemption, carbon offset payments, and the inclusion of farmland for biomass production. The model was applied to a four-county study area in Kentucky representing conditions commonly found in the Ohio River Valley. Results showed that both biomass price and discount rate have a can strongly influence the amount of economically efficient sites. Rising the biomass price by 5 $·t −1 and lowering discount rate by 1% from the baseline scenario (40 $·t −1 and 5%) resulted in an over fourteen fold increment. Property tax exemption resulted in a fourfold increase, a carbon payment on only 1 $·t −1 caused a twelve fold increase and extending the landbase from marginal land to farmland only slightly increase the economically efficient sites. These results provide an objective evaluation of market and policy scenarios in terms of their potential to increase land availability for establishing dedicated energy crops and to promote the bioenergy industry.

Biomass has gained considerable attention in the southern United States (US) mainly because of its potential to partially replace fossil fuels and develop a sustainable bioenergy industry. Dedicated energy crops could offer a reliable and sustainable biomass supply, but there is limited research identifying suitable sites and evaluating their economic feasibility. This study developed a model to identify potential sites to establish dedicated energy crops based on the economic feasibility of short rotation woody crops. Site suitability was based on site-specific woody biomass yield, production costs, and delivered biomass prices. Transportation costs including off-road and on-road transportation costs were based on travel time from each potential plantation site to the nearest conversion facility. Break-even biomass amounts were obtained by considering production costs and biomass price, and potential biomass yield was estimated based on site index. Break-even biomass amounts were then compared with potential biomass yields to determine suitable sites to establish dedicated energy crops. To illustrate the applicability of the model, it was applied to a four-county test area in northern Kentucky with a diverse land cover and ownership, relatively extensive transportation network, and presence of existing conversion facilities, conditions which are common in the Ohio River Valley region and much of the southern US.

doi: 10.3126/banko.v19i1.2182Banko Janakari, Vol. 19, No. 1, 41