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See detailAt the boundaries of institutional theorizing: Individual entrepreneurship in episodes of regulatory change
Löhlein, Lukas; Muessig, Anke UL

in Accounting, Organizations and Society (2020), 83

We analyse the institutional dynamics surrounding the establishment of independent audit oversight in Germany from 1997 to 2016. Complementing prior works, which have focused on countries where the global ... [more ▼]

We analyse the institutional dynamics surrounding the establishment of independent audit oversight in Germany from 1997 to 2016. Complementing prior works, which have focused on countries where the global demand for independent regulation coincides with the domestic erosion of public trust in professional self-regulation, we investigate regulatory change in a context featuring strong trust in the accounting profession. To analyse the accounting establishment’s response to expanding global standards of accounting regulation and the escalating resistance of small accounting firms, as orchestrated by one individual, we mobilize a Bourdieusian field perspective and the literature on institutional entrepreneurship. By demonstrating how intra-professional conflict has increasingly eroded the establishment’s capital to reproduce its hegemonic field position and keep the regulator at distance, our case provides a counterpoint to prior research, which suggests that oversight is mainly the product of negotiations between a unified profession and the regulatory authority. Examining a rare instance of individual entrepreneurship also enables us to engage in a theory-testing process on the explanatory power of institutional ambiguitiesdthe subjectively perceived ruptures and contradictions within established social arrangementsdfor agency. Our findings suggest that ongoing encounters with institutional ambiguities result in varying disposition to activism. In this way, while acknowledging agency as a cause of field reproduction and change, our analysis shifts attention towards the relational, temporal, and transformational institutional dynamics that constitute distinct modes of agency. By identifying empirical residuals that seem to escape theorization, we also reveal the limits of institutional theorizing. [less ▲]

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See detail'Faster-than-Nyquist Signaling via Spatiotemporal Symbol-Level Precoding for Multi-User MISO Redundant Transmissions
Alves Martins, Wallace UL; Spano, Danilo UL; Chatzinotas, Symeon UL et al

in International Conference on Acoustics, Speech, and Signal Processing (ICASSP-2020), Barcelona 4-8 May 2020 (2020, May)

This paper tackles the problem of both multi-user and intersymbol interference stemming from co-channel users transmitting at a faster-than-Nyquist (FTN) rate in multi-antenna downlink transmissions. We ... [more ▼]

This paper tackles the problem of both multi-user and intersymbol interference stemming from co-channel users transmitting at a faster-than-Nyquist (FTN) rate in multi-antenna downlink transmissions. We propose a framework for redundant block-based symbol-level precoders enabling the trade-off between constructive and destructive multi-user and interblock interference (IBI) effects at the single-antenna user terminals. Redundant elements are added as guard interval to handle IBI destructive effects. It is shown that, within this framework, accelerating the transmissions via FTN signaling improves the error-free spectral efficiency, up to a certain acceleration factor beyond which the transmitted information cannot be perfectly recovered by linear filtering followed by sampling. Simulation results corroborate that the proposed spatiotemporal symbol-level precoding can change the amount of added redundancy from zero (full IBI) to half (IBI-free) the equivalent channel order, so as to achieve a target balance between spectral and energy efficiencies. [less ▲]

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See detailSecurity and Performance Implications of BGP Rerouting-resistant Guard Selection Algorithms for Tor
Mitseva, Asya UL; Aleksandrova, Marharyta UL; Engel, Thomas UL et al

in Security and Performance Implications of BGP Rerouting-resistant Guard Selection Algorithms for Tor (2020, May)

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See detailSDN-based Misbehavior Detection System for Vehicular Networks
Boualouache, Abdelwahab UL; Soua, Ridha UL; Engel, Thomas UL

in 2020 IEEE 91st Vehicular Technology Conference (VTC2020-Spring) (2020, May)

Vehicular networks are vulnerable to a variety of internal attacks. Misbehavior Detection Systems (MDS) are preferred over the cryptography solutions to detect such attacks. However, the existing ... [more ▼]

Vehicular networks are vulnerable to a variety of internal attacks. Misbehavior Detection Systems (MDS) are preferred over the cryptography solutions to detect such attacks. However, the existing misbehavior detection systems are static and do not adapt to the context of vehicles. To this end, we exploit the Software-Defined Networking (SDN) paradigm to propose a context-aware MDS. Based on the context, our proposed system can tune security parameters to provide accurate detection with low false positives. Our system is Sybil attack-resistant and compliant with vehicular privacy standards. The simulation results show that, under different contexts, our system provides a high detection ratio and low false positives compared to a static MDS. [less ▲]

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See detailBacAnalytics: A Tool to Support Secondary School Examination in France
Roussanaly, Azim; Aleksandrova, Marharyta UL; Boyer, Anne

in 25th International Symposium on Intelligent Systems (ISMIS 2020) (2020, May)

Students who failed the final examination in the secondary school in France (known as baccalauréat or baccalaureate) can improve their scores by passing a remedial test. This test consists of two oral ... [more ▼]

Students who failed the final examination in the secondary school in France (known as baccalauréat or baccalaureate) can improve their scores by passing a remedial test. This test consists of two oral examinations in two subjects of the student's choice. Students announce their choice on the day of the remedial test. Additionally, the secondary education system in France is quite complex. There exist several types of baccalaureate consisting of various streams. Depending upon the stream students belong to, they have different subjects allowed to be taken during the remedial test and different coefficients associated with each of them. In this context, it becomes difficult to estimate the number of professors of each subject required for the examination. Thereby, the general practice of remedial test organization is to mobilize a large number of professors. In this paper, we present BacAnalytics - a tool that was developed to assist the rectorate of secondary schools with the organization of remedial tests for the baccalaureate. Given profiles of students and their choices of subjects for previous years, this tool builds a predictive model and estimates the number of required professors for the current year. In the paper, we present the architecture of the tool, analyze its performance, and describe its usage by the rectorate of the Academy of Nancy-Metz in Grand Est region of France in the years 2018 and 2019. BacAnalytics achieves almost 100% of prediction accuracy with approximately 25% of redundancy and was awarded a French national prize Impulsions 2018. [less ▲]

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See detailOn the Efficiency of Test Suite based Program Repair: A Systematic Assessment of 16 Automated Repair Systems for Java Programs
Liu, Kui UL; Wang, Shangwen; Koyuncu, Anil UL et al

in 42nd ACM/IEEE International Conference on Software Engineering (ICSE) (2020, May)

Test-based automated program repair has been a prolific field of research in software engineering in the last decade. Many approaches have indeed been proposed, which leverage test suites as a weak, but ... [more ▼]

Test-based automated program repair has been a prolific field of research in software engineering in the last decade. Many approaches have indeed been proposed, which leverage test suites as a weak, but affordable, approximation to program specifications. Although the literature regularly sets new records on the number of benchmark bugs that can be fixed, several studies increasingly raise concerns about the limitations and biases of state-of-the-art approaches. For example, the correctness of generated patches has been questioned in a number of studies, while other researchers pointed out that evaluation schemes may be misleading with respect to the processing of fault localization results. Nevertheless, there is little work addressing the efficiency of patch generation, with regard to the practicality of program repair. In this paper, we fill this gap in the literature, by providing an extensive review on the efficiency of test suite based program repair. Our objective is to assess the number of generated patch candidates, since this information is correlated to (1) the strategy to traverse the search space efficiently in order to select sensical repair attempts, (2) the strategy to minimize the test effort for identifying a plausible patch, (3) as well as the strategy to prioritize the generation of a correct patch. To that end, we perform a large-scale empirical study on the efficiency, in terms of quantity of generated patch candidates of the 16 open-source repair tools for Java programs. The experiments are carefully conducted under the same fault localization configurations to limit biases. Eventually, among other findings, we note that: (1) many irrelevant patch candidates are generated by changing wrong code locations; (2) however, if the search space is carefully triaged, fault localization noise has little impact on patch generation efficiency; (3) yet, current template-based repair systems, which are known to be most effective in fixing a large number of bugs, are actually least efficient as they tend to generate majoritarily irrelevant patch candidates. [less ▲]

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See detailTransmit Beamforming Design with Received-Interference Power Constraints: The Zero-Forcing Relaxation
Lagunas, Eva UL; Perez-Neira, Ana; Lagunas, Miguel Angel et al

in IEEE Int. Conf. on Acoustics, Speech, and Signal Processing (ICASSP), Barcelona, Spain, May 2020 (2020, May)

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See detailExponential integrability and exit times of diffusions on sub-Riemannian and metric measure spaces
Thompson, James UL; Thalmaier, Anton UL

in Bernoulli (2020), 26(3), 2202-2225

In this article we derive moment estimates, exponential integrability, concentration inequalities and exit times estimates for canonical diffusions in two settings each beyond the scope of Riemannian ... [more ▼]

In this article we derive moment estimates, exponential integrability, concentration inequalities and exit times estimates for canonical diffusions in two settings each beyond the scope of Riemannian geometry. Firstly, we consider sub-Riemannian limits of Riemannian foliations. Secondly, we consider the non-smooth setting of RCD*(K,N) spaces. In each case the necessary ingredients are an Ito formula and a comparison theorem for the Laplacian, for which we refer to the recent literature. As an application, we derive pointwise Carmona-type estimates on eigenfunctions of Schrodinger operators. [less ▲]

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See detailIs Risk-Neutral Skewness an Indicator of Jump Risk? Evidence from Tail Risk-Taking of Hedge Funds
Lehnert, Thorsten UL

E-print/Working paper (2020)

Research suggests that systematic tail risk affects the cross-sectional variation in hedge fund returns. Fund’s tail risk is mainly induced by its investments in more tail-sensitive stocks and is ... [more ▼]

Research suggests that systematic tail risk affects the cross-sectional variation in hedge fund returns. Fund’s tail risk is mainly induced by its investments in more tail-sensitive stocks and is positively related to a trading strategy of writing out-of-the-money put options on the equity market index. Hence, high tail risk hedge funds are exposed to higher moments risks; they sell market volatility risk and buy market skewness risk. The relationship between the return spread of a high minus low tail risk strategy and a market volatility factor is expected to be negative and empirically observed to be negative. However, the relationship between a tail risk strategy and a market skewness factor is expected to be positive but I find it to be negative. In this paper, I explore this puzzling result. Using equity-oriented hedge fund return data, I find that equity market skewness risk explains a major part of variations in hedge funds’ tail risk. My results suggest that the observed negative relationship relates to the problem of price pressure associated with “crowded trades” of mutual funds. Given that retail investors are prone to herding, the directional trading of mutual funds is correlated, and their collective actions can generate short-term price pressure on aggregate stock prices (price ‘noise’). Short sellers systematically exploit these patterns not only in the equity lending market, but also in the options market by moving in the opposite direction. Hence, in times when investors shift their funds from bond to equity mutual funds, short selling in the options market, the non-fundamental demand for index put options, induces a negative relationship between risk-neutral market skewness and returns. Accordingly, the long leg of the tail risk strategy appears to be negatively exposed to market skewness risk, which is in contrast to the usual interpretation of option-implied skewness as an indicator of jump risk. My results are in line with empirical evidence that suggests that the shape of the implied volatility curve is attributable to the demand pressure of specific option series and a limited ability of arbitrageurs to bring prices back into alignment. [less ▲]

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See detailXPS Modeling of Immobilized Recombinant Angiogenin and Apoliprotein A1 on Biodegradable Nanofibers
Manakhov, Anton; Permyakova, Elizaveta; Ershov, Sergey UL et al

in Nanomaterials (2020), 10(5), 879

The immobilization of viable proteins is an important step in engineering efficient scaffolds for regenerative medicine. For example, angiogenin, a vascular growth factor, can be considered a neurotrophic ... [more ▼]

The immobilization of viable proteins is an important step in engineering efficient scaffolds for regenerative medicine. For example, angiogenin, a vascular growth factor, can be considered a neurotrophic factor, influencing the neurogenesis, viability, and migration of neurons. Angiogenin shows an exceptional combination of angiogenic, neurotrophic, neuroprotective, antibacterial, and antioxidant activities. Therefore, this protein is a promising molecule that can be immobilized on carriers used for tissue engineering, particularly for diseases that are complicated by neurotrophic and vascular disorders. Another highly important and viable protein is apoliprotein A1. Nevertheless, the immobilization of these proteins onto promising biodegradable nanofibers has not been tested before. In this work, we carefully studied the immobilization of human recombinant angiogenin and apoliprotein A1 onto plasma-coated nanofibers. We developed a new methodology for the quantification of the protein density of these proteins using X-ray photoelectron spectroscopy (XPS) and modeled the XPS data for angiogenin and apoliprotein A1 (Apo-A1). These findings were also confirmed by the analysis of immobilized Apo-A1 using fluorescent microscopy. The presented methodology was validated by the analysis of fibronectin on the surface of plasma-coated poly(ε-caprolactone) (PCL) nanofibers. This methodology can be expanded for other proteins and it should help to quantify the density of proteins on surfaces using routine XPS data treatment. [less ▲]

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See detailAn Annotation Framework for Luxembourgish Sentiment Analysis
Sirajzade, Joshgun UL; Gierschek, Daniela UL; Schommer, Christoph UL

in Besacier, Laurent; Sakti, Sakriani; Soria, Claudia (Eds.) et al Proceedings of the LREC 2020 1st Joint SLTU and CCURL Workshop (SLTU-CCURL 2020) (2020, May)

The aim of this paper is to present a framework developed for crowdsourcing sentiment annotation for the low-resource language Luxembourgish. Our tool is easily accessible through a web interface and ... [more ▼]

The aim of this paper is to present a framework developed for crowdsourcing sentiment annotation for the low-resource language Luxembourgish. Our tool is easily accessible through a web interface and facilitates sentence-level annotation of several annotators in parallel. In the heart of our framework is an XML database, which serves as central part linking several components. The corpus in the database consists of news articles and user comments. One of the components is LuNa, a tool for linguistic preprocessing of the data set. It tokenizes the text, splits it into sentences and assigns POS-tags to the tokens. After that, the preprocessed text is stored in XML format into the database. The Sentiment Annotation Tool, which is a browser-based tool, then enables the annotation of split sentences from the database. The Sentiment Engine, a separate module, is trained with this material in order to annotate the whole data set and analyze the sentiment of the comments over time and in relationship to the news articles. The gained knowledge can again be used to improve the sentiment classification on the one hand and on the other hand to understand the sentiment phenomenon from the linguistic point of view. [less ▲]

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See detailThe Lehman Sisters Claim
Lehnert, Thorsten UL

E-print/Working paper (2020)

I evaluate Christine Lagarde´s claim that more female leaders can be associated with more prudence, and less of the risky decision-making that had provoked the crisis. Indeed, the proportion of women who ... [more ▼]

I evaluate Christine Lagarde´s claim that more female leaders can be associated with more prudence, and less of the risky decision-making that had provoked the crisis. Indeed, the proportion of women who are employed in decision-making and management roles in governments, large enterprises and institutions varies substantially across European countries and is oftentimes below 30%. Research suggests that in addition to biological differences, men and women show morphological dissimilarities in specific brain regions, which explain the observed differences in behavior. As a result, female decision makers tend to be more risk averse, better suited to carefully analyze a problem, superior in multitasking and better in creating solutions that work for a group. Not surprisingly, firms with more female decision makers tend to outperform their peers in terms of productivity, profitability and stock performance while taking fewer risks. In this paper, I aim to explore the effect of female decision making on aggregate equity returns. Relying on an equilibrium asset-pricing model in an economy under jump diffusion, I decompose the moments of the returns of European stock market indices into a diffusive (systematic) risk and an (idiosyncratic) extreme event risk part. For a balanced panel of European countries, I find empirical evidence for a Lehman sisters’ effect: female decision making is an important determinant of (idiosyncratic) extreme event risk. As a result, stock markets in countries with more female decision makers are characterized by higher risk aversion, lower volatility and more positive return asymmetry, primarily driven by extreme event risk, e.g. the lower frequency of negative jumps. Results are robust to the inclusion of various controls for other country- or market-specific characteristics. [less ▲]

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See detailProceedings of the 6th Global Conference on Artificial Intelligence (GCAI 2020)
Danoy, Grégoire UL; Pang, Jun UL; Sutcliffe

in 6th Global Conference on Artificial Intelligence (2020, May)

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See detailCache-aided full-duplex: Delivery time analysis and optimization
Vu, Thang Xuan UL; Trinh, Anh Vu; Chatzinotas, Symeon UL et al

in Wireless Networks (2020)

Edge caching has received much attention as a promising technique to overcome the stringent latency and data-hungry challenges in the future generation wireless networks. Meanwhile, full-duplex (FD ... [more ▼]

Edge caching has received much attention as a promising technique to overcome the stringent latency and data-hungry challenges in the future generation wireless networks. Meanwhile, full-duplex (FD) transmission can improve the spectral efficiency by allowing a node to receive and transmit on the same frequency band simultaneously. In this paper, we investigate the delivery time performance of a cache-aided FD system, in which an edge node, operates in FD mode, serves users via wireless channels and is equipped with a cache memory. Firstly, we derive a closed-form expression for the average delivery time by taking into account the uncertainties of both backhaul and access wireless channels. The derived analysis allows the examination of the impact of the key parameters, e.g., cache size and transmit power. Secondly, a power optimization problem is formulated to minimize the average delivery time. To deal with the non-convexity of the formulated problem, we propose an iterative optimization algorithm based on the bisection method. Finally, numerical results are presented to demonstrate the effectiveness of the proposed algorithm, which can significantly reduce the delivery time compared to the FD reference and the half-duplex counterpart. [less ▲]

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See detailMultichannel Source Separation Using Time-Deconvolutive CNMF
Dias, Thadeu; Alves Martins, Wallace UL; Biscainho, Luiz Wagner

in Journal of Communication and Information Systems (2020), 35(1), 103-112

This paper addresses the separation of audio sources from convolutive mixtures captured by a microphone array. We approach the problem using complex-valued non-negative matrix factorization (CNMF), and ... [more ▼]

This paper addresses the separation of audio sources from convolutive mixtures captured by a microphone array. We approach the problem using complex-valued non-negative matrix factorization (CNMF), and extend previous works by tailoring advanced (single-channel) NMF models, such as the deconvolutive NMF, to the multichannel factorization setup. Further, a sparsity-promoting scheme is proposed so that the underlying estimated parameters better fit the time-frequency properties inherent in some audio sources. The proposed parameter estimation framework is compatible with previous related works, and can be thought of as a step toward a more general method. We evaluate the resulting separation accuracy using a simulated acoustic scenario, and the tests confirm that the proposed algorithm provides superior separation quality when compared to a state-of-the-art benchmark. Finally, an analysis of the effects of the introduced regularization term shows that the solution is in fact steered toward a sparser representation. [less ▲]

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See detailComponent Analysis of Adjectives in Luxembourgish for Detecting Sentiments
Sirajzade, Joshgun UL; Gierschek, Daniela UL; Schommer, Christoph UL

in Beermann, Dorothee; Besacier, Laurent; Sakti, Sakriani (Eds.) et al Proceedings of the LREC 2020 1st Joint SLTU and CCURL Workshop(SLTU-CCURL 2020) (2020, May)

The aim of this paper is to investigate the role of Luxembourgish adjectives in expressing sentiments in user comments written at the web presence of rtl.lu (RTL is the abbreviation for Radio Television ... [more ▼]

The aim of this paper is to investigate the role of Luxembourgish adjectives in expressing sentiments in user comments written at the web presence of rtl.lu (RTL is the abbreviation for Radio Television Lëtzebuerg). Alongside many textual features or representations, adjectives could be used in order to detect sentiment, even on a sentence or comment level. In fact, they are also by themselves one of the best ways to describe a sentiment, despite the fact that other word classes such as nouns, verbs, adverbs or conjunctions can also be utilized for this purpose. The empirical part of this study focuses on a list of adjectives that were extracted from an annotated corpus. The corpus contains the part of speech tags of individual words and sentiment annotation on the adjective, sentence, and comment level. Suffixes of Luxembourgish adjectives like -esch, -eg, -lech, -al, -el, -iv, -ent, -los, -bar and the prefix on- were explicitly investigated, especially by paying attention to their role in regards to building a model by applying classical machine learning techniques. We also considered the interaction of adjectives with other grammatical means, especially other part of speeches, e.g. negations, which can completely reverse the meaning, thus the sentiment of an utterance. [less ▲]

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See detailDynamic Adaptation of Software-defined Networks for IoT Systems: A Search-based Approach
Shin, Seung Yeob UL; Nejati, Shiva UL; Sabetzadeh, Mehrdad UL et al

in Proceedings of the 15th International Symposium on Software Engineering for Adaptive and Self-Managing Systems (SEAMS'20) (2020, May)

The concept of Internet of Things (IoT) has led to the development of many complex and critical systems such as smart emergency management systems. IoT-enabled applications typically depend on a ... [more ▼]

The concept of Internet of Things (IoT) has led to the development of many complex and critical systems such as smart emergency management systems. IoT-enabled applications typically depend on a communication network for transmitting large volumes of data in unpredictable and changing environments. These networks are prone to congestion when there is a burst in demand, e.g., as an emergency situation is unfolding, and therefore rely on configurable software-defined networks (SDN). In this paper, we propose a dynamic adaptive SDN configuration approach for IoT systems. The approach enables resolving congestion in real time while minimizing network utilization, data transmission delays and adaptation costs. Our approach builds on existing work in dynamic adaptive search-based software engineering (SBSE) to reconfigure an SDN while simultaneously ensuring multiple quality of service criteria. We evaluate our approach on an industrial national emergency management system, which is aimed at detecting disasters and emergencies, and facilitating recovery and rescue operations by providing first responders with a reliable communication infrastructure. Our results indicate that (1) our approach is able to efficiently and effectively adapt an SDN to dynamically resolve congestion, and (2) compared to two baseline data forwarding algorithms that are static and non-adaptive, our approach increases data transmission rate by a factor of at least 3 and decreases data loss by at least 70%. [less ▲]

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See detailDeep Learning for Beam Hopping in Multibeam Satellite Systems
Lei, Lei UL; Lagunas, Eva UL; Yuan, Yaxiong UL et al

in IEEE 91st Vehicular Technology Conference (VTC2020-Spring) (2020, May)

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See detailMarché du travail transfrontalier : Quelles équations à résoudre?
Pigeron-Piroth, Isabelle UL; Belkacem, Rachid

in Les Cahiers de la Grande Région (2020), 2

Après un premier numéro consacré aux évolutions démographiques, ce volume, édité par Rachid Belkacem (Université de Lorraine) et Isabelle Pigeron-Piroth (Université du Luxembourg) interroge les évolutions ... [more ▼]

Après un premier numéro consacré aux évolutions démographiques, ce volume, édité par Rachid Belkacem (Université de Lorraine) et Isabelle Pigeron-Piroth (Université du Luxembourg) interroge les évolutions actuelles et futures du marché du travail transfrontalier. Pour traiter ces différents aspects, cinq articles, constituant des synthèses de travaux réalisés par divers instituts (LISER, ADEM et STATEC) aborderont les questions de compétences recherchées dans la Grande Région, les inadéquations entre offres et demandes de travail, mais aussi les nouveaux modèles d’organisation du travail (télétravail), ou de croissance (croissance qualitative), reflets de ces équations difficiles à résoudre,mais aussi des problématiques d’actualité liées à la crise sanitaire . [less ▲]

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