59,829 research outputs found
A Taxonomy for Congestion Control Algorithms in Vehicular Ad Hoc Networks
One of the main criteria in Vehicular Ad hoc Networks (VANETs) that has
attracted the researchers' consideration is congestion control. Accordingly,
many algorithms have been proposed to alleviate the congestion problem,
although it is hard to find an appropriate algorithm for applications and
safety messages among them. Safety messages encompass beacons and event-driven
messages. Delay and reliability are essential requirements for event-driven
messages. In crowded networks where beacon messages are broadcasted at a high
number of frequencies by many vehicles, the Control Channel (CCH), which used
for beacons sending, will be easily congested. On the other hand, to guarantee
the reliability and timely delivery of event-driven messages, having a
congestion free control channel is a necessity. Thus, consideration of this
study is given to find a solution for the congestion problem in VANETs by
taking a comprehensive look at the existent congestion control algorithms. In
addition, the taxonomy for congestion control algorithms in VANETs is presented
based on three classes, namely, proactive, reactive and hybrid. Finally, we
have found the criteria in which fulfill prerequisite of a good congestion
control algorithm
Improving Labor Inspections Systems: Design Options
[Excerpt] The following paper identifies experimental designs for the evaluation of labor inspection systems in Latin America. It includes six principal sections. Section 1 discusses the main differences between the “Latin model” (Piore and Schrank 2008) of labor inspection and the more familiar approach adopted by enforcement agencies like OSHA and the Wage and Hour Division in the US. Section 2 discusses theories of regulatory noncompliance and develops a logic model that links enforcement strategies to compliance outcomes in the region. Section 3 discusses some of the strategies that are available to Latin American labor inspectors and sets the stage for a discussion of their assignment to experimental subjects. Section 4 identifies five possible subjects of experimentation (e.g., inspectors, firms, jurisdictions) and discusses their respective receptivity to both random assignment and counterfactual analysis (e.g., data needs, estimation procedures, etc.). Section 5 addresses practical considerations involved in the design and conduct of experiments on inspection systems—including their utility, ethics, and viability—and introduces a checklist designed to facilitate their assessment. And Section 6 describes three potential experiments—labeled “professionals v. partisans,” “risk-based targeting v. randomized inspection,” and “carrots v. sticks” respectively—and discusses their principal goals and limitations in light of the checklist
More than Dollars for Scholars: The Impact of the Dell Scholars Program on College Access, Persistence and Degree Attainment
Although college enrollment rates have increased substantially over the last several decades, socioeconomic inequalities in college completion have actually widened over time. A critical question, therefore, is how to support low-income and first-generation students to succeed in college after they matriculate. We investigate the impact of the Dell Scholars Program which provides a combination of generous financial support and individualized advising to scholarship recipients before and throughout their postsecondary enrollment. The program's design is motivated by a theory of action that, in order to meaningfully increase the share of lower-income students who earn a college degree, it is necessary both to address financial constraints students face and to provide ongoing support for the academic, cultural and other challenges that students experience during their college careers. We isolate the unique impact of the program on college completion by capitalizing on an arbitrary cutoff in the program's algorithmic selection process. Using a regression discontinuity design, we find that although being named a Dell Scholar has no impact on initial college enrollment or early college persistence, scholars at the margin of eligibility are significantly more likely to earn a bachelor's degree on-time or six years after high school graduation. These impacts are sizeable and represent a nearly 25 percent or greater increase in both four- and six-year bachelor's attainment. The program is resource intensive. Yet, back-of-theenvelope calculations indicate that the Dell Scholars Program has a positive rate of return
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Information Behavior and Political Preferences
This article shows that citizens consider policy positions for the formation of their political preferences when they actively seek and find high-quality information, while they dismiss passively acquired and low-quality information. The study develops an extended theory of information and political preferences that incorporates the process of information acquisition and its connection with information quality. A novel experimental design separates the effects on political preferences due to information behavior as an activity from those due to selective exposure to information. The study applies this design in a laboratory experiment with a diverse group of participants using the example of issue voting and European integration in the context of the 2014 European Parliament elections
Population extremal optimisation for discrete multi-objective optimisation problems
The power to solve intractable optimisation problems is often found through population based evolutionary methods. These include, but are not limited to, genetic algorithms, particle swarm optimisation, differential evolution and ant colony optimisation. While showing much promise as an effective optimiser, extremal optimisation uses only a single solution in its canonical form – and there are no standard population mechanics. In this paper, two population models for extremal optimisation are proposed and applied to a multi-objective version of the generalised assignment problem. These models use novel intervention/interaction strategies as well as collective memory in order to allow individual population members to work together. Additionally, a general non-dominated local search algorithm is developed and tested. Overall, the results show that improved attainment surfaces can be produced using population based interactions over not using them. The new EO approach is also shown to be highly competitive with an implementation of NSGA-II.No Full Tex
Designing and Deploying Online Field Experiments
Online experiments are widely used to compare specific design alternatives,
but they can also be used to produce generalizable knowledge and inform
strategic decision making. Doing so often requires sophisticated experimental
designs, iterative refinement, and careful logging and analysis. Few tools
exist that support these needs. We thus introduce a language for online field
experiments called PlanOut. PlanOut separates experimental design from
application code, allowing the experimenter to concisely describe experimental
designs, whether common "A/B tests" and factorial designs, or more complex
designs involving conditional logic or multiple experimental units. These
latter designs are often useful for understanding causal mechanisms involved in
user behaviors. We demonstrate how experiments from the literature can be
implemented in PlanOut, and describe two large field experiments conducted on
Facebook with PlanOut. For common scenarios in which experiments are run
iteratively and in parallel, we introduce a namespaced management system that
encourages sound experimental practice.Comment: Proceedings of the 23rd international conference on World wide web,
283-29
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