A model for multi-class road network recovery scheduling of regional road networks

Transportation - In this paper, an optimisation model for recovery planning of road networks is presented in which both social and economic resilience is aimed to be achieved. The model is...     

Cultural Models and Shoreline Social Conflict

Along the coast we witness property conflicts that would seem strange at inland locations. To understand why property conflicts seem particularly common and intense along shorelines, one must appreciate that property is enacted by real people in specific places. The successful enactment of property requires sufficiently shared expectations for behavior. Expectations are formed by consulting cultural models, which are inter-subjectively shared cognitive tools. This article describes seven cultural models of property that can play a role in the enactment of property along the shoreline. These are the sovereignty, community, landscape, ecology, commodity, moral order, and productivity models. A focus on cultural models shows how property conflicts can occur when models are not adequately grounded in real world circumstances, when a cultural model is not shared, or when multiple cultural models conflict. This article argues that all three of these types of failures are more likely to occur along shorelines than with inland property. Finally, even though cultural models of property are not hierarchical, this article argues that too much emphasis is currently being placed on the sovereignty and commodity models, and it suggests ways to reestablish a better balance between all of the cultural models of property.     

Power Spectral Density of Road Profiles

The road profile is usually considered to be a random process x ( d ), where x is the road height and d is the distance along the road. As the vehicle travels along the road with velocity v , the random process x ( d ) is converted to a random process x ( t ) which is input to the vehicle suspension via the tyre. The random process x ( d ) is usually described in terms of its power spectral density as a function of frequency in either radians or cycles per unit distance. However, there are several different ways of defining power spectral density, and this makes it difficult to compare published data without knowing how the power spectral density has been defined. The proper calculation of RMS values of vehicle response for an assumed road power spectral density is explained by an example.     

Modelling,simulation and evaluation of ground vibration caused by rail vehicles*

ABSTRACT

There is a great need to develop rail networks over long distances and within cities as more sustainable transport options. However, noise and vibration are seen as a negative environmental consequence. Compared with airborne noise, the related problem of ground vibration is much more complex. The properties of the ground vary significantly from one location to another. There is no common assessment criterion or measurement quantity and no equivalent to the noise maps. Ground-borne vibration is transmitted into buildings and perceived either as feelable whole-body vibration or as low frequency noise; it can also affect sensitive equipment but it is generally at a level that is too low to cause structural or cosmetic damage to buildings. A review is given of evaluation criteria for both feelable vibration and ground-borne noise, empirical and numerical prediction methods, the main vehicle and track parameters that can affect the vibration levels and a range of possible mitigation methods.     

Optimal Linear Active Suspensions with Derivative Constraints and Output Feedback Control

In optimally controlled active suspensions with either full or incomplete state feedback there is tradeoff between system performance and overall stiffness. It is sought to remove this limitation by incorporating integral action which results in a system with infinite stiffness towards static loading, but which is soft with respect to road inputs. The system is also able to eliminate the steady state deflections due to step and (potentially) ramp type inputs at the wheel. Optimality is retained at the cost only of a derivative constraint and the system can be physically realised using output feedback control.     

A combined science and management framework for developing regional monitoring objectives

Abstract

Designing environmental monitoring programs to deal with widespread, subtle, and/or cumulative impacts on a regional basis is challenging. It requires a shift away from focusing primarily on individual point sources to a more regional perspective. It also necessitates involving scientists and managers together in a cooperative effort to establish priorities and articulate clear objectives. In our view, this objective‐setting task is neither a strictly scientific nor a strictly management activity. It depends on effective communication between scientists and managers but is confounded by differing perspectives, value systems, and behaviors. We present a conceptual framework to assist managers and scientists in this process. This is intended to structure such communication by helping to create a context that permits fruitful give‐and‐take between the two groups. We then describe a six‐part model for specifying the key elements of regional monitoring objectives.     

The Importance of Brokers in Collaborative Marine Ecosystem-Based Management of Social Ecological Systems

Abstract

Practitioners play a critical yet largely unexamined role in translating collaborative, ecosystem-based management (EBM) for social-ecological systems from theory to practice. We paired mental models and social network analytical methods and applied them to two cases of marine EBM in Rhode Island and New York, focusing on practitioners themselves, to understand the relationship between practitioners’ mental models of marine ecosystems and the extent and nature of collaboration within each network. Mental models analysis was used to assess the comprehensiveness and balance of practitioners’ mental models, and social network analysis was used to assess the role and influence of practitioners within each network. A comparative statistical analysis was then performed to understand the relationship between mental models and network measures. Research revealed a statistically significant correlation between practitioners’ mental model comprehensiveness and practitioners’ influence within the network. In other words, practitioners with comprehensive mental models of the ecosystem for which they were planning were found to act as “brokers,” connecting those who were not otherwise connected, bridging jurisdictions, sectors, and disciplines. Results underscore the importance of brokers in achieving the collaborative and integrated goals of EBM and suggest the need for greater attention to practitioners’ role in EBM implementation.     

Wheel/Rail Non-linear Interactions With Coupling Between Vertical and Lateral Directions

Summary A theoretical model is developed to explore the high frequency wheel/rail interaction with coupling between the vertical and lateral directions. This coupling is introduced through the track dynamics due to the offset of the wheel/rail contact point from the rail centre line. Equivalent models of the railway track in the time domain are developed according to the rail vibration receptances in the frequency domain. The wheel is represented by a mass in each direction with no vertical-lateral coupling. The vertical wheel/rail interaction is generated through a non-linear Hertzian contact stiffness, allowing for the possibility of loss of contact between the wheel and rail. The lateral interaction is represented by a contact spring and a creep force damper in series and their values depend on the vertical contact force. The vibration source is the roughness on the wheel and rail contact surfaces which forms a relative displacement excitation in the vertical direction. Using the combined interaction model with this relative displacement excitation, the wheel/rail interactions with coupling between the vertical and lateral vibrations are simulated. It is found that the lateral interaction force caused by the offset is usually less than thirty percent of the vertical dynamic force. The lateral vibration of the rail is significantly reduced due to the presence of the lateral coupling, whereas the vertical interaction is almost unaffected by the lateral force.