Effect of quasi-static prestrain on the formability of dual phase steels in electrohydraulic forming

Dual phase steels derive their name from their microstructure, which consists of islands of martensite surrounded by a ferrite matrix. These steels are increasingly being used in automobile structures in order to reduce weight, improve fuel economy, and maintain crash safety performance. The higher strength grades of dual phase steels, such as DP780 and DP980, often present significant formability challenges in sheet stamping operations, and therefore any technologies which could alleviate these issues would be of significant value to the automotive industry. Electrohydraulic forming (EHF) is based upon the electro-hydraulic effect: a complex phenomenon related to the discharge of high voltage electrical current through a liquid. In EHF, electrical energy is stored in a bank of capacitors and is converted into the kinetic energy needed to form sheet metal by rapidly discharging that energy across a pair of electrodes submerged in a fluid. During such a discharge, a high pressure, high temperature plasma channel is created between the tips of the electrodes. The resulting shockwave in the liquid, initiated by the expansion of the plasma channel, is propagated toward the blank at the acoustic velocity of the fluid, and the mass and momentum of the water in the shock wave accelerates the sheet metal blank toward the die. The objective of this paper is to report the results of formability testing of dual phase steels under three basic conditions: (1) conventional limiting dome height (LDH) testing; (2) starting with a flat blank and using one pulse of EHF to fill the desired die geometry; and (3) starting with a quasi-static preforming step to partially fill the die cavity and then using one pulse of EHF to fill the remaining area of the die cavity. A hybrid process which combines sheet hydroforming (HF) and EHF as described herein has the potential to reduce the cycle time of the EHF process by replacing the initial EHF forming increments with one quasi-static preforming step. Additionally, a numerical model was developed and employed in order to better understand the sheet deformation process within EHF. The numerical model consists of four distinct models that are integrated into one: (1) an electrical model of the discharge channel, (2) a model of the plasma, (3) a model of the liquid as a pressure-transmitting medium, and (4) a deformable sheet metal blank in contact with a rigid die. Significant improvements in formability were confirmed experimentally for DP780 and DP980 by forming into conical and v-shape dies using EHF from a flat sheet and by using EHF combined with a quasi-static preforming step. Numerical modeling showed that the peak strain rates occurring in both single-pulse EHF the hybrid HF-EHF process are approximately 17,000 units per second.     

Disseminating near-real-time hazards information and flood maps in the Philippines through Web-GIS

The Philippines being a locus of tropical cyclones, tsunamis, earthquakes and volcanic eruptions, is a hotbed of disasters. These natural hazards inflict loss of lives and costly damage to property. Situated in a region where climate and geophysical tempest is common, the Philippines will inevitably suffer from calamities similar to those experienced recently. With continued development and population growth in hazard prone areas, it is expected that damage to infrastructure and human losses would persist and even rise unless appropriate measures are immediately implemented by government. In 2012, the Philippines launched a responsive program for disaster prevention and mitigation called the Nationwide Operational Assessment of Hazards (Project NOAH), specifically for government warning agencies to be able to provide a 6 hr lead-time warning to vulnerable communities against impending floods and to use advanced technology to enhance current geo-hazard vulnerability maps. To disseminate such critical information to as wide an audience as possible, a Web-GIS using mashups of freely available source codes and application program interface (APIs) was developed and can be found in the URLs http:// noah.dost.gov.ph and http://noah.up.edu.ph/. This Web-GIS tool is now heavily used by local government units in the Philippines in their disaster prevention and mitigation efforts and can be replicated in countries that have a proactive approach to address the impacts of natural hazards but lack sufficient funds.     

User behaviour, best practice and the risks of non-target exposure associated with anticoagulant rodenticide use

Usage of anticoagulant rodenticides (ARs) is an integral component of modern agriculture and is essential for the control of commensal rodent populations. However, the extensive deployment of ARs has led to widespread exposure of a range of non-target predatory birds and mammals to some compounds, in particular the second-generation anticoagulant rodenticides (SGARs). As a result, there has been considerable effort placed into devising voluntary best practice guidelines that increase the efficacy of rodent control and reduce the risk of non-target exposure. Currently, there is limited published information on actual practice amongst users or implementation of best practice. We assessed the behaviour of a typical group of users using an on-farm questionnaire survey. Most baited for rodents every year using SGARs. Most respondents were apparently aware of the risks of non-target exposure and adhered to some of the best practice recommendations but total compliance was rare. Our questionnaire revealed that users of first generation anticoagulant rodenticides rarely protected or checked bait stations, and so took little effort to prevent primary exposure of non-targets. Users almost never searched for and removed poisoned carcasses and many baited for prolonged periods or permanently. These factors are all likely to enhance the likelihood of primary and secondary exposure of non-target species.     

Methodology for Developing Flood Rule Curves Conditioned on El Niño‐Southern Oscillation Classification1

Lee, Se‐Yeun, Alan F. Hamlet, Carolyn J. Fitzgerald, and Stephen J. Burges, 2011. Methodology for Developing Flood Rule Curves Conditioned on El Niño‐Southern Oscillation Classification. Journal of the American Water Resources Association (JAWRA) 47(1):81‐92. DOI: 10.1111/j.1752‐1688.2010.00490.x Abstract: Regional climate varies on interannual and decadal time scales that in turn affect annual streamflows, flood risks, and reservoir storage deficits in mid‐summer. However, these variable elements of the climate system are generally not included in water resources operating policies that attempt to preserve a balance between flood risk and other water resources system objectives. A methodology for incorporating El Niño‐Southern Oscillation (ENSO) information in designing flood control curves is investigated. An optimization‐simulation procedure is used to develop a set of ENSO‐conditioned flood control rule curves that relate streamflow forecasts to flood control evacuation requirements. ENSO‐conditioned simulated flood risk and storage deficits under current operating policy are used to calibrate a unique objective function for each ENSO classification. Using a case study for the Columbia River Basin, we demonstrate that ENSO‐conditioned flood control curves constructed using the optimization‐simulation procedure consistently reduce storage deficits at a number of interrelated projects without increasing flood risk. For the Columbia Basin, the overall improvements in reservoir operations are relatively modest, and (in isolation) might not motivate a restructuring of flood control operations. However, the technique is widely applicable to a wide range of water resources systems and/or different climate indices.     

Principles for retrofitting coal burners for oxy-combustion

Experiments were performed in a 1.5 MW pilot-scale furnace to investigate the differences between air- and oxy-fired flame behavior from a pulverized coal oxy-research burner designed for flexible operating conditions. The flame behavior was characterized by recording video images of the flames and by measuring radiation intensity along the flame length. Various strategies relating air- and oxy-fired operation of the burner primary register were investigated where the oxy-fired burner primary mass, momentum and velocity were matched to the air-fired conditions. Matching either burner primary mass or momentum under oxy-fired conditions with air-fired conditions resulted in a flame stabilized within the quarl. Matching primary velocity with air-fired conditions resulted in a detached flame indicating a delay in flame ignition for the oxyfired conditions. A decrease in primary velocity of 13% was necessary in order to stabilize a flame within the quarl similar to the air-fired case. Additional experiments also showed a flame could be stabilized with no oxygen enrichment of the primary (～3 vol.%, dry O₂ in the primary). Experiments where oxygen was injected at the burner face indicated injection at the boundary of the primary and secondary flow paths strongly attach a flame and injection at the coal rich primary flow path increased the radiative intensity of the flame.     

Implications of ecological data constraints for integrated policy and livelihoods modelling: An example from East Kalimantan, Indonesia

Policy and human livelihoods modelling increasingly demands integrated research which requires ecological expertise. However, contributions from ecologists are often based on sparse data. Rather than discounting such data, in this paper we demonstrate how ecological modelling can effectively contribute to the development of policy recommendations in spite of data constraints. In a petrol subsidy analysis in East Kalimantan, Indonesia, we accounted for ecological data uncertainty by (a) assuming large parameter value ranges and (b) conducting a robustness test for policy recommendations. In addition to data scarcity, counter-intuitive results emerged emphasising the need for model validation. These counter-intuitive results indicated that decreasing petrol prices led to increased poverty. This informed a policy recommendation to prevent the reduction of petrol prices below IDR 5500 per litre. Using two key livelihood resources (fish and honey), we found that while a traditional sensitivity analysis suggested highly robust results, a robustness test indicated that policy recommendations would change if the incorrectness of parameter values approached 50%. The results show that ecological modelling can contribute effectively in spite of sparse data to guide policy, as well as identifying future research priorities.     

A model-based approach to determine the long-term effects of multiple interacting stressors on coral reefs

The interaction between multiple stressors on Caribbean coral reefs, namely, fishing effort and hurricane impacts, is a key element in the future sustainability of reefs. We develop an analytic model of coral-algal interactions and explicitly consider grazing by herbivorous reef fish. Further, we consider changes in structural complexity, or rugosity, in addition to the direct impacts of hurricanes, which are implemented as stochastic jump processes. The model simulations consider various levels of fishing effort corresponding to' several hurricane frequencies and impact levels dependent on geographic location. We focus on relatively short time scales so we do not explicitly include changes in ocean temperature, chemistry, or sea level rise. The general features of our approach would, however, apply to these other stressors and to the management of other systems in the face of multiple stressors. It is determined that the appropriate management policy, either local reef restoration or fisheries management, greatly depends on hurricane frequency and impact level. For sufficiently low hurricane impact and macroalgal growth rate, our results indicate that regions with lower-frequency hurricanes require stricter fishing regulations, whereas management in regions with higher-frequency hurricanes might be less concerned with enhancing grazing and instead consider whether local-scale restorative activities to increase vertical structure are cost-effective.