318 research outputs found
The dynamic bowser routing problem
We investigate opportunities offered by telematics and analytics to enable
better informed, and more integrated, collaborative management decisions on
construction sites. We focus on efficient refuelling of assets across
construction sites. More specifically, we develop decision support models that,
by leveraging data supplied by different assets, schedule refuelling operations
by minimising the distance travelled by the bowser truck as well as fuel
shortages. Motivated by a practical case study elicited in the context of a
project we recently conducted at Crossrail, we introduce the Dynamic Bowser
Routing Problem. In this problem the decision maker aims to dynamically refuel,
by dispatching a bowser truck, a set of assets which consume fuel and whose
location changes over time; the goal is to ensure that assets do not run out of
fuel and that the bowser covers the minimum possible distance. We investigate
deterministic and stochastic variants of this problem and introduce effective
and scalable mathematical programming models to tackle these cases. We
demonstrate the effectiveness of our approaches in the context of an extensive
computational study designed around data collected on site as well as supplied
by our project partners.
Keywords: Routing; Dynamic Bowser Routing Problem; Stochastic Bowser Routing
Problem; Mixed-Integer Linear Programming; Construction
jsdp: a Java Stochastic Dynamic Programming Library
Stochastic Programming is a framework for modelling and solving problems of
decision making under uncertainty. Stochastic Dynamic Programming is a branch
of Stochastic Programming that takes a "functional equation" approach to the
discovery of optimal policies. By leveraging constructs - lambda expressions,
functional interfaces, collections and aggregate operators - implemented in
Java to operationalise the MapReduce framework, jsdp provides a general purpose
library for modelling and solving Stochastic Dynamic Programs.Comment: 8 page
Sea Container Terminals
Due to a rapid growth in world trade and a huge increase in containerized goods, sea container terminals play a vital role in globe-spanning supply chains. Container terminals should be able to handle large ships, with large call sizes within the shortest time possible, and at competitive rates. In response, terminal operators, shipping liners, and port authorities are investing in new technologies to improve container handling infrastructure and operational efficiency. Container terminals face challenging research problems which have received much attention from the academic community. The focus of this paper is to highlight the recent developments in the container terminals, which can be categorized into three areas: (1) innovative container terminal technologies, (2) new OR directions and models for existing research areas, and (3) emerging areas in container terminal research. By choosing this focus, we complement existing reviews on container terminal operations
Isolated Ramp Metering Feedback Control Utilizing Mixed Sensitivity for Desired Mainline Density and the Ramp Queues
This paper presents a feedback control design for isolated ramp metering control. This feedback control design, unlike the existing isolated feedback ramp controllers, also takes into account the ramp queue length. Using a nonlinear H∞ control design methodology, we formulate the problem in the desired setting to be able to utilize the results of the methodology
Route optimization for the cement industry under the CPEC initiative
The China-Pakistan Economic Corridor (CPEC) initiative envisages substantial infrastructure development in Pakistan. This study ascertains optimal transportation routes for the cement industry under the CPEC program using a mixed integer linear programming model and discrete-event simulation using Witness simulation software. The solution of the mathematical model presents the best combination of cement manufacturing clusters, road interchanges and ports to connect. Policy makers and practitioners can use the findings of this study to optimize logistics decisions under CPEC
Towards the definition of a quality model for mail servers
The paper presents an approach for building a Mail Server Quality
Model, based on the ISO/IEC software quality standard. We start by defining
the mail system domain to be used as general framework and the relevant
technologies involved. Then a general overview of the ISO/IEC standard is
given. The basic steps, the relevant considerations and criteria used to
select the appropriated subcharacteristics and quality attributes are also
presented. The selected attributes are categorized under the six ISO/IEC
quality characteristics conforming the model. Finally some case studies
requirements and two commercial mail server tools are used to evaluate the
model.Postprint (published version
An Agent-Based Exploration of the Hurricane Forecast-Evacuation System Dynamics
In the mainland US, the hurricane-forecast-evacuation system is uncertain, dynamic, and complex. As a result, it is difficult to know whether to issue warnings, implement evacuation management strategies, or how to make forecasts more useful for evacuations. This dissertation helps address these needs, by holistically exploring the system’s complex dynamics from a new perspective. Specifically, by developing – and using – an empirically informed, agent-based modeling framework called FLEE (Forecasting Laboratory for Exploring the Evacuation-system). The framework represents the key, interwoven elements to hurricane evacuations: the natural hazard (hurricane), the human system (information flow, evacuation decisions), the built environment (road infrastructure), and connections between systems (forecasts and warning information, traffic). The dissertation’s first article describes FLEE’s conceptualization, implementation, and validation, and presents proof-of-concept experiments illustrating its behaviors when key parameters are modified. In the second article, sensitivity analyses are conducted on FLEE to assess how evacuations change with evacuation management strategies and policies (public transportation, contraflow, evacuation order timing), evolving population characteristics (population growth, urbanization), and real and synthetic forecast scenarios impacting the Florida peninsula (Irma, Dorian, rapid-onset version of Irma). The third article begins to explore how forecast elements (e.g., track and intensity) contribute to evacuation success, and whether improved forecast accuracy over time translates to improved evacuations outcomes. In doing so, we demonstrate how coupled natural-human models – including agent-based models –can be a societally-relevant alternative to traditional metrics of forecast accuracy. Lastly, the fourth article contains a brief literature review of inequities in transportation access and their implication on evacuation modeling. Together, the articles demonstrate how modeling frameworks like FLEE are powerful tools capable of studying the hurricane-forecast-evacuation system across many real and hypothetical forecast-population-infrastructure scenarios. The research compliments, and builds-upon empirical work, and supports researchers, practitioners, and policy-makers in hazard risk management, meteorology, and related disciplines, thereby offering the promise of direct applications to mitigate hurricane losses
Sounds of Silence: A Study of Stability and Diversity of Web Audio Fingerprints
Browser fingerprinting presents a grave threat to privacy as it allows user tracking even in private browsing modes. Prior measurement studies on HTML5-based fingerprinting have been limited to Canvas and WebGL but not Web Audio APIs. We aim to fill this gap by conducting the first large-scale systematic study of web audio fingerprints and studying their stability as well as diversity properties. Using MTurk and social media platforms, we collected 8 different audio fingerprints from 694 users.
Firstly, we show that the audio fingerprints are unstable unlike other fingerprinting methods with some users having as many as 20 different fingerprints. Despite this, we show that audio fingerprinting can still be used as an effective fingerprinting vector as most fingerprints tend to repeat quite often. We devised a graph-based fingerprint matching mechanism to measure the diversity of audio fingerprints. Our results show that audio fingerprints are much less diverse with only 45 distinct fingerprints among 694 users
- …