4,911 research outputs found
Analyzing helicopter evasive maneuver effectiveness against rocket-propelled grenades
It has long been acknowledged that military helicopters are vulnerable to ground-launched threats, in particular, the RPG-7 rocket-propelled grenade. Current helicopter threat mitigation strategies rely on a combination of operational tactics and selectively placed armor plating, which can help to mitigate but not entirely remove the threat. However, in recent years, a number of active protection systems designed to protect land-based vehicles from rocket and missile fire have been developed. These systems all use a sensor suite to detect, track, and predict the threat trajectory, which is then employed in the computation of an intercept trajectory for a defensive kill mechanism. Although a complete active protection system in its current form is unsuitable for helicopters, in this paper, it is assumed that the active protection systemâs track and threat trajectory prediction subsystem could be used offline as a tool to develop tactics and techniques to counter the threat from rocket-propelled grenade attacks. It is further proposed that such a maneuver can be found by solving a pursuitâevasion differential game. Because the first stage in solving this problem is developing the capability to evaluate the game, nonlinear dynamic and spatial models for a helicopter, RPG-7 round, and gunner, and evasion strategies were developed and integrated into a new simulation engine. Analysis of the results from representative vignettes demonstrates that the simulation yields the value of the engagement pursuitâevasion game. It is also shown that, in the majority of cases, survivability can be significantly improved by performing an appropriate evasive maneuver. Consequently, this simulation may be used as an important tool for both designing and evaluating evasive tactics and is the first step in designing a maneuver-based active protection system, leading to improved rotorcraft survivability
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Nexus of thermal resilience and energy efficiency in buildings: A case study of a nursing home
Extreme weather events become more frequent and severe due to climate change. Although energy efficiency technologies can influence thermal resilience of buildings, they are traditionally studied separately, and their interconnections are rarely quantified. This study developed a methodology of modeling and analysis to provide insights into the nexus of thermal resilience and energy efficiency of buildings. We conducted a case study of a real nursing home in Florida, where 12 patients died during Hurricane Irma in 2017 due to HVAC system power loss, to understand and quantify how passive and active energy efficiency measures (EEMs) can improve thermal resilience to reduce heat-exposure risk of patients. Results show that passive measures of opening windows and doors for natural ventilation, as well as miscellaneous load reduction, are very effective in eliminating the extreme dangerous occasions. However, to maintain safe conditions, active measures such as on-site power generators and thermal storage are also needed. The nursing home was further studied by changing its location to two other cities: San Francisco (mild climate) and Chicago (cold winter and hot summer). Results revealed that the EEMs' impacts on thermal resilience vary significantly by climate and building characteristics. The study also estimated the costs of EEMs to help stakeholders prioritize the measures. Passive measures that may not save energy may greatly improve thermal resilience, and thus should be considered in building design or retrofit. Findings from this study indicate energy efficiency technologies should be evaluated not only by their energy savings performance but also by their influence on a building's resilience to extreme weather events
Allocating Conservation Resources under the Endangered Species Act
The necessity to develop a priority system to guide the allocation of resources to the conservation of endangered species is widely recognized. The economic theory of biodiversity has established a framework to do so, and has identified priority criteria that should be considered when making conservation decisions. This paper uses a random effects ordered probit model of endangered species recovery to simulate the effects of reallocating conservation funds among species listed under the Endangered Species Act according to these criteria. Our results suggest that if the goal of conservation policy is to preserve a diverse set of species, reallocating conservation funds according to criteria identified by economic theory would yield an improvement over actual spending patterns without significant tradeoffs in terms of overall species recovery.Endangered Species Act, endangered species, recovery plans, U.S. Fish and Wildlife Service, biodiversity, critical habitat, Research and Development/Tech Change/Emerging Technologies,
Understanding and Specifying Information Security Needs to Support the Delivery of High Quality Security Services
In this paper we present an approach for specifying and prioritizing information security requirements in organizations. It is important to prioritize security requirements since hundred per cent security is\ud
not achievable and the limited resources available should be directed to satisfy the most important ones. We propose to explicitly link security requirements with the organizationâs business vision, i.e. to provide business\ud
rationale for security requirements. The rationale is then used as a basis for comparing the importance of different security requirements.\ud
Furthermore we discuss how to integrate the aforementioned solution concepts into a service level management process for security services, which is an important step in IT Governance. We validate our approach by way of a focus group session
Modeling Supply Chain Resiliency
Engineered Resilient Systems (ERS) is a Department of Defense (DoD) program focusing on the effective and efficient design and development of complex engineered systems throughout their life cycle. There is a growing literature with qualitative definitions of resilience and quantitative models for systems with one performance measure. This paper uses a quantitative resilience framework (the Framework for ERS) that includes system design options, reliability, threats, vulnerabilities, responses, and consequences assessed in multiple system performance measures. The framework assists in establishing a model for any system to evaluate resiliency. This paper applies this framework using Multiple Objective Decision Analysis (MODA) to evaluate resiliency tradeoffs in designing supply chain and logistics networks to help decision makers increase the resilience of their supply chain networks. By using the MODA framework, decision makers can identify and evaluate multiple design options for a supply chain network
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