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Search Results: 1 - 10 of 131865 matches for " Konstantinos V. Katsikopoulos "
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Coherence and correspondence in engineering design
Konstantinos V. Katsikopoulos
Judgment and Decision Making , 2009,
Abstract: I show how the coherence/correspondence distinction can inform the conversation about decision methods for engineering design. Some engineers argue for the application of multi-attribute utility theory while others argue for what they call heuristics. To clarify the differences among methods, I first ask whether each method aims at achieving coherence or correspondence. By analyzing statements in the design literature, I argue that utility theory aims at achieving coherence and heuristics aim at achieving correspondence. Second, I ask if achieving coherence always implies achieving correspondence. It is important to provide an answer because while in design the objective is correspondence, it is difficult to assess it, and coherence that is easier to assess is used as a surrogate. I argue that coherence does not always imply correspondence in design and that this is also the case in problems studied in judgment and decision-making research. Uncovering the conditions under which coherence implies, or does not imply, correspondence is a topic where engineering design and judgment and decision-making research might connect.
The less-is-more effect
Konstantinos V. Katsikopoulos
Judgment and Decision Making , 2010,
Abstract: In inductive inference, a strong prediction is the less-is-more effect: Less information can lead to more accuracy. For the task of inferring which one of two objects has a higher value on a numerical criterion, there exist necessary and sufficient conditions under which the effect is predicted, assuming that recognition memory is perfect. Based on a simple model of imperfect recognition memory, I derive a more general characterization of the less-is-more effect, which shows the important role of the probabilities of hits and false alarms for predicting the effect. From this characterization, it follows that the less-is-more effect can be predicted even if heuristics (enabled when little information is available) have relatively low accuracy; this result contradicts current explanations of the effect. A new effect, the below-chance less-is-more effect, is also predicted. Even though the less-is-more effect is predicted to occur frequently, its average magnitude is predicted to be small, as has been found empirically. Finally, I show that current empirical tests of less-is-more-effect predictions have methodological problems and propose a new method. I conclude by examining the assumptions of the imperfect-recognition-memory model used here and of other models in the literature, and by speculating about future research.
Swarm Intelligence in Animal Groups: When Can a Collective Out-Perform an Expert?
Konstantinos V. Katsikopoulos,Andrew J. King
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0015505
Abstract: An important potential advantage of group-living that has been mostly neglected by life scientists is that individuals in animal groups may cope more effectively with unfamiliar situations. Social interaction can provide a solution to a cognitive problem that is not available to single individuals via two potential mechanisms: (i) individuals can aggregate information, thus augmenting their ‘collective cognition’, or (ii) interaction with conspecifics can allow individuals to follow specific ‘leaders’, those experts with information particularly relevant to the decision at hand. However, a-priori, theory-based expectations about which of these decision rules should be preferred are lacking. Using a set of simple models, we present theoretical conditions (involving group size, and diversity of individual information) under which groups should aggregate information, or follow an expert, when faced with a binary choice. We found that, in single-shot decisions, experts are almost always more accurate than the collective across a range of conditions. However, for repeated decisions – where individuals are able to consider the success of previous decision outcomes – the collective's aggregated information is almost always superior. The results improve our understanding of how social animals may process information and make decisions when accuracy is a key component of individual fitness, and provide a solid theoretical framework for future experimental tests where group size, diversity of individual information, and the repeatability of decisions can be measured and manipulated.
When Does Diversity Trump Ability (and Vice Versa) in Group Decision Making? A Simulation Study
Shenghua Luan, Konstantinos V. Katsikopoulos, Torsten Reimer
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0031043
Abstract: It is often unclear which factor plays a more critical role in determining a group's performance: the diversity among members of the group or their individual abilities. In this study, we addressed this “diversity vs. ability” issue in a decision-making task. We conducted three simulation studies in which we manipulated agents' individual ability (or accuracy, in the context of our investigation) and group diversity by varying (1) the heuristics agents used to search task-relevant information (i.e., cues); (2) the size of their groups; (3) how much they had learned about a good cue search order; and (4) the magnitude of errors in the information they searched. In each study, we found that a manipulation reducing agents' individual accuracy simultaneously increased their group's diversity, leading to a conflict between the two. These conflicts enabled us to identify certain conditions under which diversity trumps individual accuracy, and vice versa. Specifically, we found that individual accuracy is more important in task environments in which cues differ greatly in the quality of their information, and diversity matters more when such differences are relatively small. Changing the size of a group and the amount of learning by an agent had a limited impact on this general effect of task environment. Furthermore, we found that a group achieves its highest accuracy when there is an intermediate amount of errors in the cue information, regardless of the environment and the heuristic used, an effect that we believe has not been previously reported and warrants further investigation.
Herbert Simon’s spell on judgment and decision making
Konstantinos V. Katsikopoulos,Cherng-Horng (Dan) Lan
Judgment and Decision Making , 2011,
Abstract: How many judgment and decision making (JDM) researchers have not claimed to be building on Herbert Simon's work? We identify two of Simon's goals for JDM research: He sought to understand people's decision processes---the descriptive goal---and studied whether the same processes lead to good decisions---the prescriptive goal. To investigate how recent JDM research relates to these goals, we analyzed the articles published in the Journal of Behavioral Decision Making and in Judgment and Decision Making from 2006 to 2010. Out of 377 articles, 91 cite Simon or we judged them as directly relating to his goals. We asked whether these articles are integrative, in the following sense: For a descriptive article we asked if it contributes to building a theory that reconciles different conceptualizations of cognition such as neural networks and heuristics. For a prescriptive article we asked if it contributes to building a method that combines ideas of other methods such as heuristics and optimization models. Based on our subjective judgments we found that the proportion of integrative articles was 67% of the prescriptive and 52% of the descriptive articles. We offer suggestions for achieving more integration of JDM theories. The article concludes with the thesis that although JDM researchers work under Simon's spell, no one really knows what that spell is.
Do we really understand what the immunological disturbances in inflammatory bowel disease mean?
Epameinondas V Tsianos, Konstantinos Katsanos
World Journal of Gastroenterology , 2009,
Abstract: The gastrointestinal tract uses a system of tolerance and controlled inflammation to limit the response to dietary or bacteria-derived antigens in the gut. When this complex system breaks down, either by a chemical or pathogenic insult in a genetically predisposed individual the resulting immune response may lead to inflammatory bowel disease. Although the aetiopathogenesis of inflammatory bowel disease remains unsolved current evidence indicates that defective T-cell apoptosis and impairment of intestinal epithelial barrier function play important roles. In inflammatory bowel disease, it has been reported that activation of macrophages seems to be as important as increased production of the macrophage-derived cytokines such as TNF-α, IL-1 and IL-6. The triggering factor for this cascade is still to be elucidated as to whether it represents an auto-antigen or a hetero-antigen. It has been also demonstrated that a serologic anti-microbial response exists. This response includes antibodies against saccharomyces cerevisiae (ASCA), E. coli outer membrane porin C (Omp-C), flagelin (cBir1) and pseudomonas aeroginosa (I2). Host response to microbial pathogens includes self-defense mechanisms including defensins, pattern recognition receptors and Toll-like receptors. Neuroimmunomodulation in inflammatory bowel disease (IBD) is another interesting approach with implications on the influence of brain-gut axis on intestinal inflammation and its perpetuation. It is probable that inflammatory bowel disease represents a heterogenic group of diseases that share similar mechanisms of tissue damage but have different initiating events and immunoregulatory abnormalities. A better understanding of all these events will hopefully provide new insights into the mechanisms of epithelial responses to microorganisms and ideas for therapies.
Proceedings 8th International Workshop on Security Issues in Concurrency
Konstantinos Chatzikokolakis,Véronique Cortier
Computer Science , 2011, DOI: 10.4204/EPTCS.51
Abstract: This volume contains the proceedings of the 8th Workshop on Security Issues in Concurrency (SecCo 2010). The workshop was held in Paris, France on August 30th, 2010, as a satellite workshop of CONCUR'10. The aim of the SecCo workshop series is to cover the gap between the security and the concurrency communities. More precisely, the workshop promotes the exchange of ideas, trying to focus on common interests and stimulating discussions on central research questions. In particular, we called for papers dealing with security issues (such as authentication, integrity, privacy, confidentiality, access control, denial of service, service availability, safety aspects, fault tolerance, trust, language-based security, probabilistic and information theoretic models) in emerging fields like web services, mobile ad-hoc networks, agent-based infrastructures, peer-to-peer systems, context-aware computing, global/ubiquitous/pervasive computing.
A Better Understanding of the Performance of Rate-1/2 Binary Turbo Codes that Use Odd-Even Interleavers
Konstantinos S. Arkoudogiannis,Christos E. Dimakis,Konstantinos V. Koutsouvelis
Mathematics , 2012,
Abstract: The effects of the odd-even constraint - as an interleaver design criterion - on the performance of rate-1/2 binary turbo codes are revisited. According to the current understanding, its adoption is favored because it makes the information bits be uniformly protected, each one by its own parity bit. In this paper, we provide instances that contradict this point of view suggesting for a different explanation of the constraint's behavior, in terms of distance spectrum.
Eye Rubbing as a Possible Cause of Clinical Progressive Keratoconus in a Forme Fruste Keratoconic Family  [PDF]
George D. Kymionis, Konstantinos I. Tsoulnaras, Stella V. Blazaki, Michael A. Grentzelos
Open Journal of Ophthalmology (OJOph) , 2015, DOI: 10.4236/ojoph.2015.51004
Abstract: We report a case of a 21-year-old male patient who underwent corneal cross-linking (CXL) due to bilateral progressive keratoconus. Topographical screening of his family members was performed for the detection of possible familial keratoconus and showed abnormal topographical patterns resembling to Forme Fruste Keratoconus (FFK) in all the members of his family. The reported keratoconic patient that underwent CXL was the only individual of this family that referred eye rubbing in his personal ocular history; ocular and medical history of the other family members was clear. Eye rubbing could be a possible adjuvant risk factor that contributes to conversion of FFK to clinical progressive keratoconus.
Beyond the Dirac Phase Factor: Dynamical Quantum Phase-Nonlocalities in the Schrödinger Picture  [PDF]
Konstantinos Moulopoulos
Journal of Modern Physics (JMP) , 2011, DOI: 10.4236/jmp.2011.211156
Abstract: Generalized solutions of the standard gauge transformation equations are presented and discussed in physical terms. They go beyond the usual Dirac phase factors and they exhibit nonlocal quantal behavior, with the well-known Relativistic Causality of classical fields affecting directly the phases of wavefunctions in the Schrödinger Picture. These nonlocal phase behaviors, apparently overlooked in path-integral approaches, give a natural account of the dynamical nonlocality character of the various (even static) Aharonov-Bohm phenomena, while at the same time they seem to respect Causality. For particles passing through nonvanishing magnetic or electric fields they lead to cancellations of Aharonov-Bohm phases at the observation point, generalizing earlier semiclassical experimental observations (of Werner & Brill) to delocalized (spread-out) quantum states. This leads to a correction of previously unnoticed sign-errors in the literature, and to a natural explanation of the deeper reason why certain time-dependent semiclassical arguments are consistent with static results in purely quantal Aharonov-Bohm configurations. These nonlocalities also provide a remedy for misleading results propagating in the literature (concerning an uncritical use of Dirac phase factors, that persists since the time of Feynman’s work on path integrals). They are shown to conspire in such a way as to exactly cancel the instantaneous Aharonov-Bohm phase and recover Relativistic Causality in earlier “paradoxes” (such as the van Kampen thought-experiment), and to also complete Peshkin’s discussion of the electric Aharonov-Bohm effect in a causal manner. The present formulation offers a direct way to address time-dependent single- vs double-slit experiments and the associated causal issues—issues that have recently attracted attention, with respect to the inability of current theories to address them.
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