Sonia Malefaki

University of Patras | UP · Department of Mechanical Engineering and Aeronautics

The sustainability evaluation of engineering processes and structures is a multifaceted challenge, requiring the integration of diverse and often conflicting criteria. A comprehensive Sustainability Index (SI) has been developed to address this complexity, utilizing Multi-Criteria Decision-Making (MCDM), to provide balanced and effective solutions....

Eco-design has emerged as a design methodology for aircraft structures aimed at mitigating the environmental impact of aviation, starting from the design phase and onward. In the current study, an approach is proposed to facilitate a transition from eco-driven to sustainability-driven design practices for aircraft components. In this method, sustai...

The Children’s Color Trail Test (CCTT) is considered a culture fair equivalent of the Trail Making Test for the assessment of cognitive flexibility in pediatric populations, while others emphasize its additional validity as a measure of attention, perceptual tracking, processing speed, susceptibility to interference and inhibition. The need for sta...

The objective of this study was to apply and preliminarily evaluate a High-Resolution Melting (HRM) analysis technique coupled with qPCR, that allows the simultaneous detection of 10 different ruminant abortogenic pathogens, for investigating abortions in sheep and goats throughout Greece. A total of 264 ovine and caprine vaginal swabs were obtaine...

The current prevailing trend in design across key sectors prioritizes eco-design, emphasizing considerations of environmental aspects in the design process. The present work aims to take a significant leap forward by proposing a design process where sustainability serves as the primary driving force. In this context, sustainability is positioned as...

The rapid development of information and communication technologies (ICT) in recent years has brought about significant changes in many social sectors such as communication, economy, entertainment, and others. To define the key role that ICT plays in its development course, the European Union (EU) has developed a composite indicator, the Digital Ec...

The European Innovation Scoreboard (EIS) is a tool developed at the initiative of the European Commission to provide a comparative assessment of the innovation performance of European Union Member States on an annual basis through the Summary Innovation Index (SII). The assessment is based on a wide range of indicators covering four key innovation...

When it comes to achieving sustainability and circular economy objectives, multi-criteria decision-making (MCDM) tools can be of aid in supporting decision-makers to reach a satisfying solution, especially when conflicting criteria are present. In a previous work of the authors, a hybrid MCDM tool was introduced to support the selection of sustaina...

Time series quite often appear to exhibit a certain nonstationary behavior, but if they are studied jointly, there might exist a linear combination of them that could be modeled by a stationary process. Cointegration studies the effects of these combinations and the relationships among time series. If these time series share a long-run relationship...

Purpose: The aim of the present study was to adapt and validate the Speech Pathology-Specific Questionnaire for Persons with Multiple Sclerosis (SMS) into the Greek language. Method: The study sample consisted of 124 people with multiple sclerosis (PwMS) and 50 healthy controls (HCs). All PwMS underwent cognitive assessment using the Brief Inter...

Aim To compare neuropsychological function in juvenile myoclonic epilepsy (JME) and frontal lobe epilepsy (FLE) since frontal circuitry is involved in both conditions. By drawing on previously theory-guided hypotheses and findings, a particular emphasis is placed on the way different cognitive-pathophysiological mechanisms act upon to produce front...

This study investigates the relationship between verb-related morphosyntactic production (VRMP) and locality (i.e., critical cue being adjacent to the target or not), verbal Working Memory (vWM), nonverbal/visuospatial WM (nvWM), verbal short-term memory (vSTM), nonverbal/visuospatial STM (nvSTM), speed of processing, and education. Eighty healthy...

The ability of persons with non-fluent aphasia (PWAs) to produce sentential negation has been investigated in several languages, but only in small samples. Accounts of (morpho)syntactic impairment in PWAs have emphasized various factors, such as whether the negative marker blocks or interferes with verb movement, the position of the Negation Phrase...

Objective: Cognitive screening instruments (CSIs) are essential for everyday practice. The Quick Mild Cognitive Impairment (Qmci) screen, a short instrument designed to identify mild cognitive impairment, was recently translated into Greek (Qmci-Gr). The present study compared its diagnostic value against the Montreal Cognitive Assessment (MoCA) sc...

Plant growth modeling has attracted a lot of attention due to its potential applications. Many scientific disciplines are involved, and a lot of research effort and intensive computer methods were needed to understand better the complex mechanisms underlying plant evolution. Among the numerous challenges, one can cite mathematical modeling, paramet...

In several real data applications a biased sample arises naturally from the selection procedure. Recently, Economou et al. (Biom J 62: 238–249, 2020) used the concept of bivariate weighted distributions and proposed four different families of weight functions to describe cases in which the bias in a bivariate sample is caused by adopting sampling s...

Growth theory argues on the role of heterogeneity that can lead to multiple regimes examining countries’ performance. A metaproduction stochastic function for the Bayesian frontier model is developed to estimate productive performance across 109 countries over a 20-year period using two distinct frontiers (OECD vs. non-OECD countries). The metafron...

Background A recent systematic review found that language deficits are not very common in individuals with multiple sclerosis (MS). However, there are significant gaps in our knowledge about language abilities in MS. For instance, morphosyntactic production has not been explored adequately thus far. This study investigated verb-related morphosyntac...

This chapter considers a two‐unit multi‐state deteriorating system under preventive condition‐based maintenance and imperfect switch among units. It describes the transient behavior of the two‐unit system under a Markov framework and examines how unit inspection intervals, as well as switching mechanism success probability, affect the entire system...

Growth theory argues on the role of heterogeneity that can lead to multiple regimes examining countries performance. A meta-production stochastic function under a Bayesian perspective has been developed to estimate technical efficiencies across countries over a time period. The metafrontier model is used to highlight heterogeneity among cluster of...

The most of the contemporary large scale technological systems are functioning under multiple stages of degradation, from their perfect state to their total failure. The study of the performance and the availability of multi-stage systems is of great importance since their deterioration and/or failure may lead to important losses. Under a proper in...

Cognitive impairment is frequently encountered in multiple sclerosis (MS) affecting between 40-65% of individuals, irrespective of disease duration and severity of physical disability. In the present multicenter randomized controlled trial, fifty-eight clinically stable RRMS patients with mild to moderate cognitive impairment and relatively low dis...

A significant challenge being faced in recommender systems research concerns the provision of robust explanations about why a particular option is suggested. These explanations may exploit diverse data types concerning the users and items under consideration. In line with the above, this paper introduces a novel framework for automatic explanations...

In this paper, a general model for multi-state deteriorating systems with condition based preventive maintenance is introduced and analyzed extensively. The system experiences various levels of deterioration and at each stage, an inspection is carried out at constant time intervals in order to identify what kind of preventive maintenance, the syste...

It is of practical importance to extend time-to-event models in order to be applicable in situations with recurrent events on the same individual or machine. The model proposed here extends in this direction a threshold regression model with random individual effects, in which event times are modeled as realizations of the first hitting times of an...

Rey's Auditory Verbal Learning Test (RAVLT) is a widely used neuropsychological test to assess episodic memory. In the present study we sought to establish normative and discriminative validity data for the RAVLT in the elderly population using previously adapted learning lists for the Greek adult population. We administered the test to 258 cogniti...

The empirical survival function of time-to-event data very often appears not to tend to zero. Thus there are long-term survivors, or a “cured fraction” of units which will apparently never experience the event of interest. This feature of the data can be incorporated into lifetime models in various ways, for example, by using mixture distributions...

The procedure of damage accumulation in composite materials, especially during fatigue loading, is a complex phenomenon which depends on a number of parameters such as service loading conditions, ply orientation, material properties, geometrical non-linearities etc. Due to the stochastic nature of damage evolution, its mathematical modelling, param...

In this paper a multi-state deterioration system which experiences several states of performance degradation until it fails is studied extensively and condition-based preventive maintenance policies are examined. The optimal maintenance policy aims at maximizing system's asymptotic availability and at minimizing its total operational cost, with res...

A semi–Markov setting is considered in order to study the main dependability measures of a repairable continuous time system under the hypothesis that the evolution in time of its components is described by a continuous time semi–Markov process. Moreover, the main dependability measures of a periodically maintained system are studied. Finally, all...

Mathematical modeling of plant growth has gained increasing interest in recent years due to its potential applications. A general family of models, known as functional–structural plant models (FSPMs) and formalized as dynamic systems, serves as the basis for the current study. Modeling, parameterization and estimation are very challenging problems...

Grid computing is an evolutionary technological achievement that takes advantages of wide area communication and large scale resource sharing. Although there are several advantages, grid does not guaranty stableness of resources due to their resources’ nature, diverse failures and error conditions that may appear. Consequently, grid dependability i...

The Metropolis–Hastings algorithm is one of the most basic and well-studied Markov chain Monte Carlo methods. It generates a Markov chain which has as limit distribution the target distribution by simulating observations from a different proposal distribution. A proposed value is accepted with some particular probability otherwise the previous valu...

We consider importance sampling as well as other properly weighted samples with respect to a target distribution π from a different point of view. By considering the associated weights as sojourn times until the next jump, we define appropriate jump processes. When the original sample sequence forms an ergodic Markov chain, the associated jump proc...

Mathematical modeling of plant growth has gained increasing interest in recent years due to its potential applications. A general family of models of Carbon allocation formalized as dynamic systems serves as the basis for our study. They are known as functional-structural plant models (FSPMs, [45]). Modeling, parameterization and estimation are ver...

In this paper, rejuvenation is modeled in a redundant computer system in order to counteract software aging. The evolution of such a system in time could be modeled by a Markov or a semi-Markov process. Nevertheless, due to generally distributed repair times of system components, the entire system is non -- Markovian. Thus, Monte Carlo simulation m...

We consider repairable Multi-state reliability systems with components, the lifetimes and the repair times of which are -independent. The -th component can be either in the complete failure state 0, in the perfect state , or in one of the degradation states . The sojourn time in any of these states is a random variable following a discrete distribu...

A Grid computing environment is an important technology used for solving large scale problems with geographically distributed resources. A grid enables the sharing and the aggregation of a wide variety of resources. In order to provide an efficient service to the users, a central node called Resource Management System manages all the grid services...

The Hidden semi-Markov models (HSMMs) were introduced to overcome the constraint of a geometric sojourn time distribution for the different hidden states in the classical hidden Markov models. Several variations of HSMMs were proposed that model the sojourn times by a parametric or a nonparametric family of distributions. In this article, we concen...

Two of the most common problems in computational statistics are sampling from a complex multidimensional distribution and integration. As the dimension of the state space increases such problems become more dicult to handle. For this reason, several Monte Carlo (MC) and Markov Chain Monte Carlo (MCMC) methods have been developed. A simple approach...

Probabilistic Neural Networks (PNNs) constitute a promis- ing methodology for classification and prediction tasks. Their perfor- mance depends heavily on several factors, such as their spread param- eters, kernels, and prior probabilities. Recently, Evolutionary Bayesian PNNs were proposed to address this problem by incorporating Bayesian models fo...

In the frame of current treatment options for multiple sclerosis (MS) and recommendations for early intervention, we investigated the practice and attitudes of neurologists towards MS-diagnosis communication in Greece. We constructed and sent out a 22-item questionnaire to neurologists practising in different employment settings and geographic regi...

Importance Sampling (IS) is a well-known Monte Carlo method which is used in order to estimate expectations with respect to a target distribution π, using a sample from another distribution g and weighting properly the output. Here, we consider IS from a different point of view. By considering the weights as sojourn times until the next jump, we as...

The present study sought to establish normative and discriminant validity data for Rey's Auditory Verbal Learning Test [Rey, A. (1964). L ‘examen clinique en psychologie [Clinical tests in psychology]. Paris: Presses Universitaires de France; Schmidt, M. (1996). Rey auditory verbal learning test: A handbook. Los Angeles, CA: Western Psychological S...

The multinomial distribution is a key-distribution for several applications. For this reason, many methods have been proposed so far in the literature in order to deal with the problem of simulation from it. A slight modification is suggested which can be used in conjunction with any of the standard schemes. The proposed variation is a two-stage pr...

A well-known and widely used model for classification and prediction is the Probabilistic Neural Network (PNN). PNN's performance is influenced by the kernels' spread parameters so recently several approaches have been proposed to tackle this problem. The proposed approach is a combination of two well known methods applied to PNNs. First, it incorp...

The authors examined neuropsychological functioning in 20 long-term (LT), 20 shorter term (ST) heavy frequent cannabis users, and 24 controls after abstinence for > or =24 hours prior to testing. LT users performed significantly worse on verbal memory and psychomotor speed. LT and ST users had a higher proportion of deficits on verbal fluency, verb...

We consider importance sampling as well as other properly weighted samples with respect to a target distribution $\pi$ from a different point of view. By considering the associated weights as sojourn times until the next jump, we define appropriate jump processes. When the original sample sequence forms an ergodic Markov chain, the associated jump...

Probabilistic Neural Networks (PNNs) constitute a well- known methodology for classification and prediction tasks. However, their performance depends on several factors, such as their spread pa- rameters, kernels and prior probabilities. Recently, Evolutionary Ba- yesian PNNs were proposed to address this problem by incorporating Bayesian estimatio...