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Second Scenario (second + scenario)
Selected AbstractsWavelet-based simulation of spectrum-compatible aftershock accelerogramsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 11 2008S. Das Abstract In damage-based seismic design it is desirable to account for the ability of aftershocks to cause further damage to an already damaged structure due to the main shock. Availability of recorded or simulated aftershock accelerograms is a critical component in the non-linear time-history analyses required for this purpose, and simulation of realistic accelerograms is therefore going to be the need of the profession for a long time to come. This paper attempts wavelet-based simulation of aftershock accelerograms for two scenarios. In the first scenario, recorded main shock and aftershock accelerograms are available along with the pseudo-spectral acceleration (PSA) spectrum of the anticipated main shock motion, and an accelerogram has been simulated for the anticipated aftershock motion such that it incorporates temporal features of the recorded aftershock accelerogram. In the second scenario, a recorded main shock accelerogram is available along with the PSA spectrum of the anticipated main shock motion and PSA spectrum and strong motion duration of the anticipated aftershock motion. Here, the accelerogram for the anticipated aftershock motion has been simulated assuming that temporal features of the main shock accelerogram are replicated in the aftershock accelerograms at the same site. The proposed algorithms have been illustrated with the help of the main shock and aftershock accelerograms recorded for the 1999 Chi,Chi earthquake. It has been shown that the proposed algorithm for the second scenario leads to useful results even when the main shock and aftershock accelerograms do not share the same temporal features, as long as strong motion duration of the anticipated aftershock motion is properly estimated. Copyright © 2008 John Wiley & Sons, Ltd. [source] Co-evolution between ectoparasites and their insect hosts: a simulation study of a damselfly,water mite interactionECOLOGICAL ENTOMOLOGY, Issue 6 2001Jens Rolff Summary 1. A simulation model investigating the co-evolution of water mites infesting their aquatic insect hosts during emergence is presented. The model is based on field and experimental studies of the ectoparasitic water mite Arrenurus cuspidator and the damselfly Coenagrion puella. 2. Three scenarios were studied: (1) Only the host was allowed to evolve timing of emergence, while the timing of the parasites' infestation opportunity was held constant. (2) Both host and parasite were allowed to evolve. (3) Only the parasite's timing was allowed to evolve, while the host was constrained completely. 3. In the first two scenarios, parasite abundances decreased in the course of evolution and reached values well below those found in the field, whereas in the third scenario, parasite abundances were maintained at a level close to that found in the field. In the second scenario (co-evolution), the host seemed to be the leader in the evolutionary race. 4. It is concluded that water mite parasitism is capable of shaping emergence patterns in aquatic insects and, despite the same life-cycle length for host and parasite, the parasite evolves fast enough to shape its hatching pattern to match the emergence pattern of its host. [source] If you try to stop smoking, should we pay for it?ADDICTION, Issue 6 2010The cost, utility of reimbursing smoking cessation support in the Netherlands ABSTRACT Background Smoking cessation can be encouraged by reimbursing the costs of smoking cessation support (SCS). The short-term efficiency of reimbursement has been evaluated previously. However, a thorough estimate of the long-term cost,utility is lacking. Objectives To evaluate long-term effects of reimbursement of SCS. Methods Results from a randomized controlled trial were extrapolated to long-term outcomes in terms of health care costs and (quality adjusted) life years (QALY) gained, using the Chronic Disease Model. Our first scenario was no reimbursement. In a second scenario, the short-term cessation rates from the trial were extrapolated directly. Sensitivity analyses were based on the trial's confidence intervals. In the third scenario the additional use of SCS as found in the trial was combined with cessation rates from international meta-analyses. Results Intervention costs per QALY gained compared to the reference scenario were approximately ,1200 extrapolating the trial effects directly, and ,4200 when combining the trial's use of SCS with the cessation rates from the literature. Taking all health care effects into account, even costs in life years gained, resulted in an estimated incremental cost,utility of ,4500 and ,7400, respectively. In both scenarios costs per QALY remained below ,16 000 in sensitivity analyses using a life-time horizon. Conclusions Extrapolating the higher use of SCS due to reimbursement led to more successful quitters and a gain in life years and QALYs. Accounting for overheads, administration costs and the costs of SCS, these health gains could be obtained at relatively low cost, even when including costs in life years gained. Hence, reimbursement of SCS seems to be cost-effective from a health care perspective. [source] Quantifying uncertainty in estimates of C emissions from above-ground biomass due to historic land-use change to cropping in AustraliaGLOBAL CHANGE BIOLOGY, Issue 8 2001Damian J. Barrett Abstract Quantifying continental scale carbon emissions from the oxidation of above-ground plant biomass following land-use change (LUC) is made difficult by the lack of information on how much biomass was present prior to vegetation clearing and on the timing and location of historical LUC. The considerable spatial variability of vegetation and the uncertainty of this variability leads to difficulties in predicting biomass C density (tC ha,1) prior to LUC. The issue of quantifying uncertainties in the estimation of land based sources and sinks of CO2, and the feasibility of reducing these uncertainties by further sampling, is critical information required by governments world-wide for public policy development on climate change issues. A quantitative statistical approach is required to calculate confidence intervals (the level of certainty) of estimated cleared above-ground biomass. In this study, a set of high-quality observations of steady state above-ground biomass from relatively undisturbed ecological sites across the Australian continent was combined with vegetation, topographic, climatic and edaphic data sets within a Geographical Information System. A statistical model was developed from the data set of observations to predict potential biomass and the standard error of potential biomass for all 0.05° (approximately 5 × 5 km) land grid cells of the continent. In addition, the spatial autocorrelation of observations and residuals from the statistical model was examined. Finally, total C emissions due to historic LUC to cultivation and cropping were estimated by combining the statistical model with a data set of fractional cropland area per land grid cell, fAc (Ramankutty & Foley 1998). Total C emissions from loss of above-ground biomass due to cropping since European colonization of Australia was estimated to be 757 MtC. These estimates are an upper limit because the predicted steady state biomass may be less than the above-ground biomass immediately prior to LUC because of disturbance. The estimated standard error of total C emissions was calculated from the standard error of predicted biomass, the standard error of fAc and the spatial autocorrelation of biomass. However, quantitative estimates of the standard error of fAc were unavailable. Thus, two scenarios were developed to examine the effect of error in fAc on the error in total C emissions. In the first scenario, in which fAc was regarded as accurate (i.e. a coefficient of variation, CV, of fAc = 0.0), the 95% confidence interval of the continental C emissions was 379,1135 MtC. In the second scenario, a 50% error in estimated cropland area was assumed (a CV of fAc = 0.50) and the estimated confidence interval increased to between 350 and 1294 MtC. The CV of C emissions for these two scenarios was 25% and 29%. Thus, while accurate maps of land-use change contribute to decreasing uncertainty in C emissions from LUC, the major source of this uncertainty arises from the prediction accuracy of biomass C density. It is argued that, even with large sample numbers, the high cost of sampling biomass carbon may limit the uncertainty of above-ground biomass to about a CV of 25%. [source] Beyond the Producer-driven/Buyer-driven Dichotomy The Evolution of Global Value Chains in the Internet EraIDS BULLETIN, Issue 3 2001Gary Gereffi Summaries The Internet is still in the early stages of its development, but its impact on global value chains is already evident. While it may be premature to try to identify lasting changes on producer-driven and buyer-driven chains, several possible scenarios are emerging and they are not mutually exclusive. The first scenario is that electronic commerce will lead to the emergence of infomediary-based value chains that privilege direct on-line access to consumers. A second scenario is that the Internet is really just extending the logic of buyer-driven chains as both information and power continue to shift inexorably from manufacturers, marketers and retailers to consumers. A third scenario is that the impact of the Internet will be captured and integrated into the practices of large established companies, thus reinforcing power relationships in existing producer-driven and buyer-driven governance structures. Although there is evidence to support all three scenarios, the third model currently seems to be dominant. [source] A re-examination of the excess smoothness puzzle when consumers estimate the income processJOURNAL OF FORECASTING, Issue 5 2001Anurag N. Banerjee Abstract The excess smoothness puzzle is explored using a simple version of the permanent income hypothesis. The new feature is that consumers do not know the observed data-generating process for income. Instead they estimate the income process every period using the past income data and update their income forecasts as new data arrive. Two scenarios are examined: first, where the income has a linear deterministic trend and second, where the income has a constant trend. There is a misspecification bias in the estimate of the marginal propensity to consume (MPC). This bias is of second-order importance in the first scenario while it is of first-order importance in the second. We conclude that the second scenario, which may be relevant for less developed countries, may offer a potential solution to the excess smoothness puzzle. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||