Hamdi Kavak

Cloud-based simulators: making simulations accessible to non-experts and experts alike

The benefits of on-demand computing capabilities, broad network access, maintainability, and multiplatform support are some of the essential characteristics that have made cloud computing the technology to adopt in recent years. While the technology has been used in simulation to some extent, it has not been widely available as it is expensive and complex. This paper reports on the design and development of a cloud-based discrete event simulator called ClouDES. ClouDES provides a platform for designing and executing discrete-event simulations with all the advantages of cloud computing. Its web-based easy to use interface attracts even non-expert users. As an example, the potential impact on non-experts users like students and especially middle and high school students are described. It is believed that students can be exposed to STEM concepts like probability, queuing, and functions while using technologies they are familiar with like mobile devices and social media.

Applying statistical debugging for enhanced trace validation of agent-based models

The verification and validation (V&V) of agent-based models (ABMs) is challenging. The underlying structure of the model and the agents can change over time. Furthermore, the theoretical context of the model is often very different from established models of the same phenomenon. In an effort to overcome these issues, trace validation is becoming a common V&V mechanism within the agent-based modeling community. In trace validation, characteristics of agents and the model are tracked over time and then analyzed by subject matter experts (SMEs) to gain insight into unexpected and potentially invalid output. Here, we present our tool, the V&V Calculator, which applies predicates employed in the field of software engineering. The result is a structured trace validation approach with quantifiable measures that facilitates SME exploration and insight into the causes of unexpected output within ABMs.

Towards a World Wide Web of Simulation

The process of developing and running simulations needs to become simple and accessible to audiences ranging from middle school students in a learning environment to subject matter experts in order to make the benefits of modeling and simulation commonly available. However, current simulations are for the most part developed and run on platforms that are: (1) demanding in terms of computational resources, (2) difficult for general audiences to use owing to unintuitive interfaces mired in mathematical syntax, (3) expensive to acquire and maintain and (4) hard to interoperate and compose. The result is a four-dimensional expense that makes simulation inaccessible to the general public. In this paper we show that by embracing the web and its standards, the use and development of simulations can become democratized and be part of a Web of Simulation where people of all skill levels are able to build, upload, retrieve, rate, and connect simulations. We show how the Web of Simulation can be built using the three basic principles of service orientation, platform independence, and interoperability. Finally, we present strategies for implementing the Web of Simulation and discuss challenges and possible approaches.

Semi-automated initialization of simulations: an application to healthcare

As the number of variables and entities included in a simulation model increase, it becomes more difficult to initialize due to (a) the increasing number of input variables that are required and (b) the difficulty in finding, retrieving, and assigning the initial values of the input variables, especially in Human Social Cultural Behavior Modeling. As a result, the initialization process is generally more time consuming and error prone which motivates the need for semi-automated approaches wherever possible. In this paper, we propose a semi-automated approach for initializing input variables that are challenging to quantify and require additional processing to be assigned their initial values. We apply this approach to initialize a healthcare simulation using data from sources such as the US Census Bureau, County Health Rankings, and Twitter. Results show that the approach works well when we can find variables with existing values even for large input data sets (over 50 variables). However, additional work is required to determine whether the values assigned using this approach yield more accurate simulation results.

Temporal and Spatiotemporal Investigation of Tourist Attraction Visit Sentiment on Twitter

In this paper, we propose a sentiment-based approach to investigate the temporal and spatiotemporal effects on tourists’ emotions when visiting a city’s tourist destinations. Our approach consists of four steps: data collection and preprocessing from social media; visitor origin identification; visit sentiment identification; and temporal and spatiotemporal analysis. The temporal and spatiotemporal dimensions include day of the year, season of the year, day of the week, location sentiment progression, enjoyment measure, and multi-location sentiment progression. We apply this approach to the city of Chicago using over eight million tweets. Results show that seasonal weather, as well as special days and activities like concerts, impact tourists’ emotions. In addition, our analysis suggests that tourists experience greater levels of enjoyment in places such as observatories rather than zoos. Finally, we find that local and international visitors tend to convey negative sentiment when visiting more than one attraction in a day whereas the opposite holds for out of state visitors.

Using simulation games for teaching and learning discrete-event simulation

Capturing and retaining the attention of students while learning complex topics like modeling and simulation is a critical task. In discrete-event simulation (DES), educators rely on examples like queueing systems in fast food restaurants or manufacturing organizations to provide the necessary context for learning. In many instances, these examples fall short in capturing the attention of students, especially at the middle and high school levels. One approach for learning complex topics, like creating simulations, is through gaming. This paper reports on the creative use of regular simulation tools to develop simulation games with entertainment content aimed towards engaging young learners. Two games are presented: one focuses on the use of decision nodes while the second focuses on the use of batch/separator nodes. As part of future work, we propose to use these games to evaluate how much knowledge transfers from an entertainment context to one using simulations for real-life situations.