Konstantinos Pelechrinis

University of Pittsburgh | Pitt · Telecommunications

Non-Fungible Token (NFT) markets are one of the fastest growing digital markets today, with the sales during the third quarter of 2021 exceeding $10 billions! Nevertheless, these emerging markets—similar to traditional emerging marketplaces—can be seen as a great opportunity for illegal activities (e.g., money laundering, sale of illegal goods etc....

Implicit biases occur automatically and unintentionally and are particularly present when we have to make split second decisions. One such situations appears in refereeing, where referees have to make an instantaneous decision on a potential violation. In this work I revisit and extend some of the existing work on implicit biases in refereeing. In...

Implicit biases occur automatically and unintentionally and are particularly present when we have to make split second decisions. One such situations appears in refereeing, where referees have to make an instantaneous decision on a potential violation. In this work we revisit and extend some of the existing work on implicit biases in refereeing. In...

Implicit biases occur automatically and unintentionally and are particularly present when we have to make split second decisions. One such situations appears in refereeing, where referees have to make an instantaneous decision on a potential violation. In this work we revisit and extend some of the existing work on implicit biases in refereeing. In...

In the Pittsburgh region, the Every1online project, led by the non-profit Meta Mesh, bridges communities with no-cost Internet service. Recognizing that digital literacy is a core component of digital inclusion, the authors worked with Meta Mesh to consider the digital literacy needs of community members and to be responsive to these needs through...

"An advanced city is not a place where the poor move about in cars, rather it's where even the rich use public transportation". This is what Enrique Penalosa, the celebrated ex-mayor of Bogota once said. However, in order to achieve this objective, one of the crucial properties that the public transportation systems need to satisfy is reliability....

Non-Fungible Token (NFT) markets are one of the fastest growing digital markets today, with the sales during the third quarter of 2021 exceeding $10 billions! Nevertheless, these emerging markets - similar to traditional emerging marketplaces - can be seen as a great opportunity for illegal activities (e.g., money laundering, sale of illegal goods...

Streaks of success have always fascinated people and a lot of research has been conducted to identify whether the “hot hand” effect is real. While sports have provided an appropriate platform for studying this phenomenon, the majority of existing literature examines scenarios in a vacuum with results that might or might not be applicable in the wil...

Identifying the patterns in urban mobility is important for a variety of tasks such as transportation planning, urban resource allocation, emergency planning etc. This is evident from the large body of research on the topic, which has exploded with the vast amount of geo-tagged user-generated content from online social media. However, most of the e...

One of the most crucial elements for the long-term success of shared transportation systems (bikes, cars etc.) is their ubiquitous availability. To achieve this, and avoid having stations with no available vehicle, service operators rely on rebalancing. While different operators have different approaches to this functionality, overall it requires a...

Modern basketball is all about creating efficient shots, that is, shots with high payoff. This is not necessarily equivalent to creating looks with the highest probability of success. In particular, the two most efficient shots in the NBA - which are shots from the paint, i.e., extremely close to the basket, and three-point shots from the corner, i...

With the focus that cities around the world have put on sustainable transportation during the past few years, biking has become one of the foci for local governments globally. Cities all over the world invest in biking infrastructure, including bike lanes, bike parking racks, shared (dockless) bike systems etc. However, one of the critical factors...

Soccer is undeniably the most popular sport world-wide and everyone from general managers and coaching staff to fans and media are interested in evaluating players’ performance. Metrics applied successfully in other sports, such as the (adjusted) +/− that allows for division of credit among a basketball team’s players, exhibit several challenges wh...

Miller and Sanjurjo [8] showed that the majority of the hot hand studies were subject to streak selection bias, leading to an underestimation of any effect present. In this study, we extend the elegant permutation test recommended by Miller and Sanjurjo [8] to in-game situations, where consecutive shots of a player are not identical. We do so by de...

In the absence of pharmaceutical interventions to curb the spread of COVID-19, countries relied on a number of nonpharmaceutical interventions to fight the first wave of the pandemic. The most prevalent one has been stay-at-home orders, whose the goal is to limit the physical contact between people, which consequently will reduce the number of seco...

Traditional venue and tour recommendation systems do not necessarily provide a diverse set of recommendations and leave little room for serendipity . In this article, we design MPG, a Mobile Personal Guide that recommends: (i) a set of diverse yet surprisingly interesting venues that are aligned to user preferences and (ii) a set of routes, constru...

The NFL collects detailed tracking data capturing the location of all players and the ball during each play. Although the raw form of this data is not publicly available, the NFL releases a set of aggregated statistics via their Next Gen Stats (NGS) platform. They also provide charts showing the locations of pass attempts and outcomes for individua...

Continuous-time assessments of game outcomes in sports have become increasingly common in the last decade. In American football, only discrete-time estimates of play value were possible, since the most advanced public football datasets were recorded at the play-by-play level. While measures such as expected points and win probability are useful for...

Abstract Learning low-dimensional representations of graphs has facilitated the use of traditional machine learning techniques to solving classic network analysis tasks such as link prediction, node classification, community detection, etc. However, to date, the vast majority of these learning tasks are focused on traditional single-layer/unimodal...

Basketball is one of a number of sports which, within the past decade, have seen an explosion in quantitative metrics and methods for evaluating players and teams. However, it is still challenging to evaluate individual off-ball events (e.g., screens, cuts away from the ball etc.) in terms of how they contribute to the success of a possession. In t...

Which area in NYC is the most similar to Lower East Side? What about the NoHo Arts District in Los Angeles? Traditionally this task utilizes information about the type of places located within the areas and some popularity/quality metric. We take a different approach. In particular, urban dwellers' time-variant mobility is a reflection of how they...

In his seminal work stability in competition, Hotelling developed a model for identifying the spatial equilibrium for two competing firms such that they maximize their market-share. He considered a linear area of fixed length and he showed that in this setting the two competing firms should be located side-by-side in the middle of the line. Hotelli...

The NFL collects detailed tracking data capturing the location of all players and the ball during each play. Although the raw form of this data is not publicly available, the NFL releases a set of aggregated statistics via their Next Gen Stats (NGS) platform. They also provide charts that visualize the locations of pass attempts for players through...

Continuous-time assessments of game outcomes in sports have become increasingly common in the last decade. In American football, only discrete-time estimates of play value were possible, since the most advanced public football datasets were recorded at the play-by-play level. While measures like expected points (EP) and win probability (WP) are use...

The goal of this work is to systematically extract information from hacker forums, whose information would be in general described as unstructured: the text of a post is not necessarily following any writing rules. By contrast, many security initiatives and commercial entities are harnessing the readily public information, but they seem to focus on...

“Not all yards are created equal”. A 3rd and 15, where the running back gains 12 yards is clearly less valuable than a 3rd and 3 where the running back gains 4 yards, even though it will not necessarily show up in the yardage statistics. While this problem has been addressed to some extent with the introduction of expected point models, there is st...

How much is an on-ball screen worth? How much is a backdoor cut away from the ball worth? Basketball is one of a number of sports which, within the past decade, have seen an explosion in quantitative metrics and methods for evaluating players and teams. However, it is still challenging to evaluate individual off-ball events in terms of how they con...

With the focus that cities around the world have put on sustainable transportation during the past few years, biking has become one of the foci for local governments around the world. Cities all over the world invest in bike infrastructure, including bike lanes, bike parking racks, shared (dockless) bike systems etc. However, one of the critical fa...

Which of your team’s possible lineups has the best chances against each of your opponent’s possible lineups? To answer this question, we develop LinNet (which stands for LINeup NETwork). LinNet exploits the dynamics of a directed network that captures the performance of lineups during their matchups. The nodes of this network represent the differen...

Computer and social sciences offer a wide range of tools to help face the world’s challenges arising in smart city scenarios and involving environment, energy, food, water, transportation, infrastructures, society, healthcare, education, governance, and economy. Indeed, purely technical solutions might be of little effect without proper considerati...

During the past few years advancements in sports information systems and technology has allowed the collection of a number of detailed spatio-temporal data that capture various aspects of basketball. For example, shot charts, that is, maps capturing locations of (made or missed) shots, and spatio-temporal trajectories for the players on the court c...

Analyzing the impact of disastrous events has been central to understanding and responding to crises. Traditionally, the assessment of disaster impact has primarily relied on the manual collection and analysis of surveys and questionnaires as well as the review of authority reports. This can be costly and time-consuming, whereas a timely assessment...

Soccer is undeniably the most popular sport world-wide, but at the same time it is one of the least quantified. While there are many reasons for this, one of the main is the difficulty to explicitly quantify the contribution of every player on the field to his team chances of winning. For example, successful advanced metrics such as the (adjusted)...

Recent studies in urban navigation have revealed new demands (e.g., diversity, safety, happiness, serendipity) for the navigation services that are critical to providing useful recommendations to travelers. This exposes the need to design next-generation navigation services that accommodate these newly emerging aspects. In this paper, we present a...

The goal of this work is to systematically extract information from hacker forums, whose information would be in general described as unstructured: the text of a post is not necessarily following any writing rules. By contrast, many security initiatives and commercial entities are harnessing the readily public information, but they seem to focus on...

Waterpipe tobacco smoking has grown in popularity among US college students and is associated with serious health risks. Much of the waterpipe tobacco smoking takes place in establishments such as “hookah bars” or in lounge settings. Web-based data platforms such as Yelp have demonstrated utility in locating these establishments but are prone to ov...

Data and analytics have been part of the sports industry from as early as the 1870s, when the first boxscore in baseball was recorded. However, it is only recently that advanced data mining and machine learning techniques have been utilized for facilitating the operations of sports franchises. While part of the reason is related with the ability to...

Location has been identified as a critical factor for the success of a business. For example, businesses in dense urban areas are exposed to more customers than businesses in sparsely populated neighborhoods, while proximity to a popular landmark can increase a business’s reach. This creates significant challenges for new businesses to expand their...

The shot selection process in basketball can be thought of as an indicator of the identity of a player/team. Characterization of these processes is important for player and team comparisons, pre-game scouting etc. Typically, shot charts are compared in a heuristic manner. Recently though automated ways have appeared in the sports analytics literatu...

During a trip planning, tourists gather information from different sources, select and rank the places to visit according to their personal interests, and try to devise daily tours among them. This paper addresses the complex selection and touring problem and proposes a “filter-first, tour-second” framework for generating personalized tour recommen...

During the last years the number of cities that have installed and started operating shared bike systems has significantly increased. These systems provide an alternative and sustainable mean of transportation to the city dwellers. Apart from the energy sustainability benefits, shared bike systems can have a positive effect on residents’ health, ai...

Demographic information. (PDF)

Null experiment for ϕτ. (PDF)

Demographics of home owners and renters. (PDF)

How much useful information can we extract from security forums? Many security initiatives and commercial entities are harnessing the readily public information, but they seem to focus on structured sources of information. Our goal here is to extract information from hacker forums, whose information is provided in ad hoc and unstructured ways. Here...

Which of your team's possible lineups has the best chances against each of your opponents possible lineups? In order to answer this question we develop LinNet. LinNet exploits the dynamics of a directed network that captures the performance of lineups at their matchups. The nodes of this network represent the different lineups, while an edge from n...

As the Internet of Things permeates every aspect of human life, assessing the credence or integrity of the data generated by "things" becomes a central exercise for making decisions or in auditing events. In this paper, we present a vision of this exercise that includes the notion of data credence, assessing data credence in an efficient manner, an...

During the last sports season a lot of discussion has been generated for the several, high-profile, "comebacks" that were observed in almost all sports. The Cavaliers won the championship after being down 3-1 in the NBA final's series, which was exactly the case for Chicago Cubs and the World Series. The Patriots won the Super Bowl even though they...

Standardized FPM. (PDF)

How much does a fumble affect the probability of winning an American football game? How balanced should your offense be in order to increase the probability of winning by 10%? These are questions for which the coaching staff of National Football League teams have a clear qualitative answer. Turnovers are costly; turn the ball over several times and...

The workshop program of the Association for the Advancement of Artificial Intelligence's International Confer: ence on Web and Social Media (AAAI-16) was held in Cologne, Germany. There were.eight workshops in the program: CityLab, Challenges and Futures for Ethical Social Media Research, Social Media and Demographic Research, Wiki, #Fail: Things T...

In mission critical IT services, system failure prediction becomes increasingly important; it prevents unexpected system downtime, and assures service reliability for end users. While operational console logs record rich and descriptive information on the health status of those IT systems, existing system management technologies mostly use them in...

The study of disaster events and their impact in the urban space has been traditionally conducted through manual collections and analysis of surveys, questionnaires and authority documents. While there have been increasingly rich troves of human behavioral data related to the events of interest, the ability to obtain hindsight following a disaster...

Local businesses and retail stores are a crucial part of local economy. Local governments design policies for facilitating the growth of these businesses that can consequently have positive externalities on the local community. However, many times these policies have completely opposite from the expected results (e.g., free curb parking instead of...

Even though it might have taken some time, the three-point line ultimately changed the way the game is played as evidenced by the increase in the three-point shot attempts over the years. However, during the last few years we have experienced record-breaking seasons in terms of both three-point attempts and field goals made. This brings back to the...

Peer behaviors are highly influential in youth decision-making around whether to use marijuana. Social media, as a popular form of peer interaction, has extended peer influence on marijuana use from “in-person” to “on-line” relationships. This is highly concerning, as youth may report their marijuana use on social media as it occurs. The immediacy...

Identifying the patterns in urban mobility is important for a variety of tasks such as transportation planning, urban resource allocation, emergency planning etc. This is evident from the large body of research on the topic, which has exploded with the vast amount of geo-tagged user-generated content from online social media. However, most of the e...

Jamming attacks have become prevalent during the last few years facilitated by the open access to the shared wireless medium as well as the increased motivation and easiness to create damage as a result of sophistication of wireless devices, both legitimate and jamming ones. Among the challenges that a wireless network faces while trying to confron...

Complex networks have been shown to exhibit universal properties, with one of the most consistent patterns being the scale-free degree distribution, but are there regularities obeyed by the r-hop neighborhood in real networks? We answer this question by identifying another power-law pattern that describes the relationship between the fractions of n...

Network connections have been shown to be correlated with structural or external attributes of the network vertices in a variety of cases. Given the prevalence of this phenomenon network scientists have developed metrics to quantify its extent. In particular, the assortativity coefficient is used to capture the level of correlation between a single...

Do NFL teams make rational decisions? What factors affect the probability of wining a game in NFL? How can a team come back from a demoralizing interception? In this study we begin by examining the hypothesis of irrational coaching, that is, coaching decisions are not always rational. We verify this hypothesis by analyzing the decisions made in the...

A heated debate has been in the forefront of scientific circles during the last few years. Rogue studies being published with falsified data, abuse and misuse of statistical analysis tools, and a general lack of trust for a scientific methods have been regular topics not only within the scientific community but in the popular press as well. In this...

With the ubiquitous development of mobile technologies, many cities today have installed mobile-enabled bike sharing systems - both publicly and privately owned - in an effort to nudge dwellers towards a more sustainable mode of transportation. However, there is little evidence - apart from anecdote stories - for the success of these systems. In th...

The increased levels of urbanization have resulted in the demand for developing urban technologies that can realize the vision of smart cities, i.e., urban environments that are sustainable, livable and resilient. Electromechanical infrastructure is substituted by intelligent, cyber-physical infrastructure (e.g., coin-based ticket fare collectors a...

With the rise of online social networks and smartphones that record the user's location, a new type of online social network has gained popularity during the last few years, the so called Location-based Social Networks (LBSNs). In such networks, users voluntarily share their location with their friends via a “check-in”. In exchange they get recomme...

Advancements in mobile technology and computing have fostered the collection of a large number of civic datasets that capture the pulse of urban life. Furthermore, the open government and data initiative has led many local authorities to make these datasets publicly available, hoping to drive innovation that will further improve the quality of life...

Advancements in mobile technology and computing have fostered the collection of a large number of civic datasets that capture the pulse of urban life. Furthermore, the open government and data initiative has led many local authorities to make these datasets pub- licly available, hoping to drive innovation that will further improve the quality of li...

Location-based social networks (LBSNs) have recently attracted a lot of attention due to the number of novel services they can offer. Prior work on analysis of LBSNs has mainly focused on the social part of these systems. Even though it is important to know how different the structure of the social graph of an LBSN is as compared to the friendship-...

Based on a recent report from the United Nations, more than 50% of the world's population currently lives in cities. This percentage is projected to increase to 70% by the year 2050 [1]. As massive amounts of people move to urban areas there is a need for cities to be run more efficiently, while at the same time improving the quality of life of the...

The proliferation of mobile handheld devices in combination with the technological advancements in mobile computing has led to a number of innovative services that make use of the location information available on such devices. Traditional yellow pages websites have now moved to mobile platforms, giving the opportunity to local businesses and poten...

Q&A social media have gained a lot of attention during the recent years. People rely on these sites to obtain information due to a number of advantages they offer as compared to conventional sources of knowledge (e.g., asynchronous and convenient access). However, for the same question one may find highly contradicting answers, causing an ambiguit...

Based on a recent report from the United Nations, more than 50% of the world’s population currently lives in cities. This percentage is projected to increase to 70% by the year 2050 [1]. As massive amounts of people move to urban areas there is a need for cities to be run more efficiently, while at the same time improving the quality of life of the...

During the last years the number of cities that have installed and operate shared biking systems has significantly increased. These systems provide an alternative and sustainable mean of transportation to the city-dwellers. Apart from the energy sustainability benefits, shared bike systems can have a positive effect on residents’ health, air qualit...

Local businesses and retail stores are a crucial part of local economy. Local governments design policies for facilitating the growth of these businesses that can consequently have positive externalities on the local community. However, many times these policies have completely opposite from the expected results (e.g., free curb parking instead of...

Assortative matching is a network phenomenon that arises when nodes exhibit a bias towards connections to others of similar characteristics. While mixing patterns in networks have been studied in the literature, and there are well-defined metrics that capture the degree of assortativity (e.g., assortativity coefficient), the latter deal only with s...

Identifying and understanding the emerging patterns in user activity is an important step in designing and developing features for online social networks. With the explosive growth of user-generated data in such networks, the recorded user activities are no more sparse snapshots but are close to a live reflection of real life. This allows us to ext...

The proliferation of mobile devices that are capable of estimating their position, has lead to the emergence of a new class of social networks, namely location-based social networks (LBSNs for short). The main interaction between users in an LBSN is location sharing. While the latter can be realized through continuous tracking of a user's whereabou...

Homophily is a phenomenon observed very frequently in social networks and is related with the inclination of people to be involved with others that exhibit similar characteristics. The roots of homophily can be subtle and are mainly traced back to two mechanisms: (i) social selection and (ii) peer influence. Decomposing the effects of each of these...