Search

This paper tackles the problem of mitigating catastrophic risk (which is risk with very low frequency but very high severity) in the context of a sequential decision making process. This problem is particularly challenging due to the scarcity of observations in the far tail of the distribution of cumulative costs (negative rewards). A policy gradient algorithm is developed, that we call POTPG. It is based on approximations of the tail risk derived from extreme value theory. Numerical experiments highlight the out-performance of our method over common benchmarks, relying on the empirical distribution. An application to financial risk management, more precisely to the dynamic hedging of a financial option, is presented., Comment: The Python code to replicate the various numerical experiments of this paper is available at https://github.com/parisadavar/EVT-policy-gradient-RL

In this paper we continue to develop the homotopy method for solving of the non linear evolution equation for the diffractive production in deep inelastic scattering(DIS). We introduce part of the nonlinear corrections as a first step of this approach. This simplified nonlinear evolution equation is solved analytically taking into account the initial and boundary conditions for the process. At the second step of our approach we demonstrated that the perturbative procedure can be used for the remaining parts of the non-linear corrections. It turns out that these corrections are small and can be estimated in the regular iterative procedure., Comment: 22 pages, 16 figures in pdf files

The recognition of business opportunities is the first stage in the entrepreneurial process. The current work analyzes the effects of individuals' possession of and access to knowledge on the probability of recognizing good business opportunities in their area of residence. The authors use an eclectic theoretical framework consisting of intellectual and social capital concepts. In particular, they analyze the role of individuals' educational level, their perception that they have the right knowledge and skills to start a business, whether they own and manage a firm, their contacts with other entrepreneurs, and whether they have been business angels. The hypotheses proposed here are tested using data collected for the GEM project in Spain in 2007. The results show that individuals' access to external knowledge through the social networks in which they participate is fundamental for developing the capacity to recognize new business opportunities.

The objective of this work is to assess the influence of certain factors on the likelihood of being a Hotels and Restaurants (H&R) entrepreneur. The factors evaluated are demographic and economic variables, variables related to perceptions of the environment and personal traits, and variables measuring the individual's intellectual and social capital. The work uses logistic regression techniques to analyze a sample of 33,711 individuals in the countries participating in the GEM project in 2008. The findings show that age, gender, income, perception of opportunities, fear of failure, entrepreneurial ability, knowing other entrepreneurs and being a business angel are explanatory factors of the probability of being an H&R entrepreneur.

In the past 15 years, two international observatories have been intensively studying entrepreneurship using empirical studies with different methodologies: GEM and PSED. Both projects have generated a considerable volume of scientific production, and their intellectual structures are worth analyzing. The current work is an exploratory study of the knowledge base of the articles generated by each of these two observatories and published in prestigious journals. The value added of this work lies in its novel characterization of the intellectual structure of entrepreneurship according to the academic production of these two initiatives. The results may be of interest to the managers and members of these observatories, as well as to academics, researchers, sponsors and policymakers interested in entrepreneurship.

Purpose: To assess the impact of the existence of and access to different work-family policies on employee well-being and job performance. Design-methodology-approach: Hypothesis testing was performed using a structural equation model based on a PLS-SEM approach applied to a sample of 1,511 employees of the Spanish banking sector. Findings: The results obtained demonstrate that the existence and true access to different types of work-family policies such as flexible working hours (flexi-time), long leaves, and flexible work location (flexi-place) are not directly related to job performance, but indirectly so, when mediated by the well-being of employees generated by work-family policies. In a similar vein, true access to employee and family support services also has an indirect positive impact on job performance mediated by the well-being produced. In contrast, the mere existence of employee and family support services does not have any direct or indirect effect on job performance. Originality-value: This study makes a theoretical and empirical contribution to better understand the impact that of the existence of and access to work-family policies on job performance mediated by employee well-being. In this sense, we posited and tested an unpublished theoretical model where the concept of employee well-being gains special relevance at academic and organizational level due to its implications for human resource management.

Purpose: Understanding the formation of entrepreneurial intentions is critical, given that it is the first step in the entrepreneurial process. Although entrepreneurial intention has been extensively studied, little attention has been paid on the intended timing of future entrepreneurial projects. This paper analyses entrepreneurial intentions among final-year university students after graduation in terms of the timeframe to start a business. Potentially rapid entrepreneurs and entrepreneurs-in-waiting were compared using the Theory of Planned Behaviour (TPB). Methodology: A variance-based structural equation modelling approach was used for the sample of 851 final-year university students with entrepreneurial intentions who participated in GUESSS project. Findings: The results obtained contribute to the understanding of how entrepreneurial intentions are formed, particularly, how intended timing plays a moderating role in the relationships of the variables of the theoretical model of TPB. This study provides empirical evidence that significant differences exist between potential rapid entrepreneurs and entrepreneurs-in-waiting. Practical implications: The findings of this study have practical implications for entrepreneurship education, and they can help policy makers develop more effective policies and programs to promote entrepreneurship. Originality: Intention-based models have traditionally examined the intent -- but not the timing -- of new venture creation. However, the time elapsed between the formation of the entrepreneurial intent and the identification of a business opportunity can vary considerably. Therefore, analysing the moderating role of intended timing could be relevant to entrepreneurial intention research.

This study analyzes the impact of work-family policies (WFP) on job performance, and the possible moderating role of gender and family responsibilities. Hypothesis testing was performed using a structural equation model based on a PLS-SEM approach applied to a sample of 1,511 employees of the Spanish banking sector. The results show that neither the existence nor the accessibility of the WFP has a direct, positive impact on performance, unlike what we expected, but both have an indirect effect via the well-being generated by these policies. We also find that neither gender nor family responsibilities have a significant moderating role on these relations, contrary to what we initially expected.

Tourism's increasing share of Gross Domestic Product throughout the world, its impact on employment and its continuous growth justifies the interest it raises amongst entrepreneurs and public authorities. However, this growth coexists with intense competition; as a result of which, tourism companies must continuously innovate in order to survive and grow. This is evident in the diversification of tourism products and destinations, the improvement of business processes and the incorporation of new technologies for intermediation, amongst other examples. This paper expounds on the factors that explain the propensity for innovation amongst tourism entrepreneurs and it may help governments to promote innovation that is based on those determining factors. The hypotheses are tested using a logistic regression on 699 international tourism entrepreneurs, taken from the 2014 Global Adult Population Survey of the Global Entrepreneurship Monitor project. The propensity for innovation amongst tourism entrepreneurs has a statistically significant relationship to gender, age, level of education and informal investments in previous businesses.

Among the main causes of absenteeism are health problems, emotional problems, and inadequate work-family policies (WFP). This paper analyses the impact of the existence and accessibility of WFP on work absenteeism, by considering the mediating role of the well-being, which includes emotional as well as physical or health problems, that is generated by these policies. We differentiate between the existence of the WFP and its accessibility, as the mere existence of the WFP in an organisation is not enough. Additionally, workers must be able to access these policies easily and without retaliation of any kind. The model includes the hierarchy and the gender as moderating variables. To test the proposed hypotheses, a structural equation model based on the partial least squares structural equation modelling (PLS-SEM) approach is applied to a sample of employees in the service sector in Spain. On the one hand, the findings show that the existence of WFP has no direct effect on absenteeism; however, accessibility to these policies does have a direct effect on absenteeism. On the other hand, both the existence and accessibility of WFP have positive direct effects on emotional well-being. In addition, emotional well-being is positively related to physical well-being which, in turn, promotes a reduction in absenteeism. Finally, significant differences in the relationship between the existence of WFP and emotional well-being confirm the special difficulty of female managers in reconciling family life and work life.

The literature on effectual theory offers validated scales to measure effectual or causal logic in entrepreneurs' decision-making. However, there are no adequate scales to assess in advance the effectual or causal propensity of people with an entrepreneurial intention before the creation of their companies. We aim to determine the validity and reliability of an instrument to measure that propensity by first analysing those works that provide recognised validated scales with which to measure the effectual or causal logic in people who have already started up companies. Then, considering these scales, we designed a scale to evaluate the effectual or causal propensity in people who had not yet started up companies using a sample of 230 final-year business administration students to verify its reliability and validity. The validated scale has theoretical implications for the literature on potential entrepreneurship and entrepreneurial intention and practical implications for promoters of entrepreneurship who need to orient the behaviour of entrepreneurs, entrepreneurs of established businesses who want to implement a specific strategic orientation, entrepreneurs who want to evaluate the effectual propensity of their potential partners and workers, and academic institutions interested in orienting the entrepreneurial potential of their students.

The tourism sector is a sector with many opportunities for business development. Entrepreneurship in this sector promotes economic growth and job creation. Knowing how entrepreneurial intention develops facilitates its transformation into entrepreneurial behaviour. Entrepreneurial behaviour can adopt a causal logic, an effectual logic or a combination of both. Considering the causal logic, decision-making is done through prediction. In this way, entrepreneurs try to increase their market share by planning strategies and analysing possible deviations from their plans. Previous literature studies causal entrepreneurial behaviour, as well as variables such as creative innovation, proactive decisions and entrepreneurship training when the entrepreneur has already created his or her firm. However, there is an obvious gap at a stage prior to the start of entrepreneurial activity when the entrepreneurial intention is formed. This paper analyses how creativity, proactivity, entrepreneurship education and the propensity for causal behaviour influence entrepreneurial intentions. To achieve the research objective, we analysed a sample of 464 undergraduate tourism students from two universities in southern Spain. We used SmartPLS 3 software to apply a structural equation methodology to the measurement model composed of nine hypotheses. The results show, among other relationships, that causal propensity, entrepreneurship learning programmes and proactivity are antecedents of entrepreneurial intentions. These findings have implications for theory, as they fill a gap in the field of entrepreneurial intentions. Considering propensity towards causal behaviour before setting up the firm is unprecedented. Furthermore, the results of this study have practical implications for the design of public education policies and the promotion of business creation in the tourism sector.

Business Process Management Systems (BPMS) represent a technology that automates business processes, connecting users to their tasks. There are many business processes within the port activity that can be improved through the use of more efficient technologies and BPMS in particular, which can help to coordinate and automate critical processes such as cargo manifests, customs declaration the management of scales, or dangerous goods, traditionally supported by EDI technologies. These technologies could be integrated with BPMS, modernizing port logistics management. The aim of this work is to demonstrate, through a systematic analysis of the literature, the state of the art in BPMS research in the port industry. For this, a systematic review of the literature of the last ten years was carried out. The works generated by the search were subsequently analysed and filtered. After the investigation, it is discovered that the relationship between BPMS and the port sector is practically non-existent which represents an important gap to be covered and a future line of research.

The aim of this paper is to carry out a systematic analysis of the literature to show the state of the art of Business Processes Management Systems (BPMS). BPMS represents a technology that automates business processes connecting users with their tasks. For this, a systematic review of the literature of the last ten years was carried out, using scientific papers indexed in the main databases of the knowledge area. The papers generated by the search were later analysed and filtered. Among the findings of this study, the academic interest and the multidisciplinary nature of the subject, as this type of studies have been identified in different areas of knowledge. Our research is a starting point for future research eager to develop a more robust theory and broaden the interest of the subject due its economic impact on process management.

Purpose: The objective of this work is to analyze the impact of implementing work-family reconciliation measures on workers' perception and how this can influence their behavior, especially in their organizational performance. Design/methodology/approach: A literature review and the main research works related to the work-family conflict and reconciliation measures to overcome this conflict have been conducted to draw conclusions about their impact on worker performance. Contributions and results: This work proposes an integrative model that shows the existing relationships between work-family reconciliation and perceptual variables on one side, and those related to the worker's organizational behavior on the other. Perceptual variables such as stress, job satisfaction, and motivation are analyzed. Regarding variables related to the worker's organizational behavior, absenteeism, turnover, and performance are analyzed. The results of the analysis provide evidence that the existence of work-family reconciliation is perceived favorably by workers and improves their organizational behavior, especially their performance. Originality/Added value: This study integrates different perspectives related to the conflict and work-family reconciliation, from an eclectic vision. Thus, it contributes to existing literature with a more comprehensive approach to the investigated topic. Additionally, the proposed integrative model allows for useful conclusions for management from both a purely human resources management perspective and organizational productivity improvement. Keywords: Work-family conflict, work-family reconciliation, perceptual variables, organizational performance, human resources managements

BPMS (Business Process Management System) represents a type of software that automates the organizational processes looking for efficiency. Since the knowledge of organizations lies in their processes, it seems probable that a BPMS can be used to manage the knowledge applied in these processes. Through the BPMS-KM Support Model, this study aims to determine the reliability and validity of a 65-item instrument to measure the utility and the use of a BPMS for knowledge management (KM). A questionnaire was sent to 242 BPMS users and to determine its validity, a factorial analysis was conducted. The results showed that the measuring instrument is trustworthy and valid. It represents implications for research, since it provides an instrument validated for research on the success of a BPMS for KM. There would also be practical implications, since managers can evaluate the use of BPMS, in addition to automating processes to manage knowledge.

For decades, entrepreneurship has been promoted in academia and tourism sector and has it been seen as an opportunity for new business ventures. In terms of entrepreneurial behavior, effectual logic shows how the individual uses his or her resources to create new opportunities. In this context, this paper aims to determine effectual propensity as an antecedent of entrepreneurial intentions. For this purpose, and based on the TPB model, we conducted our research with tourism students from Cadiz and Seville (Spain) universities with Smart PLS 3. The results show that effectual propensity influences entrepreneurial intentions and that attitude and perceived behavioral control mediate between subjective norms and intentions. Our research has a great added value since we have studied for the first time efficacious propensity as an antecedent of intentions in people who have never been entrepreneurs.

The study of work-family conflict (WFC) and work-family policies (WFP) and their impact on the well-being of employees in the tourism sector is increasingly attracting the attention of researchers. To overcome the adverse effects of WFC, managers should promote WFP, which contribute to increased well-being at work and employees' commitment. This paper aims to analyze the impact of WFP accessibility and organizational support on well-being directly and by mediating the organizational commitment that these policies might encourage. In addition, we also study whether these relationships vary according to gender and employee seniority. To test the hypotheses derived from this objective, we collected 530 valid and completed questionnaires from workers in the tourism sector in Spain, which we analyzed using structural equation modeling based on the PLS-SEM approach. The results show that human resource management must consider the importance of organizational support for workers to make WFP accessible and generate organizational commitment and well-being at work., Comment: 2023 Journal of Hospitality and Tourism Management

The Strait of Gibraltar is a region characterized by intricate oceanic sub-mesoscale features, influenced by topography, tidal forces, instabilities, and nonlinear hydraulic processes, all governed by the nonlinear equations of fluid motion. In this study, we aim to uncover the underlying physics of these phenomena within 3D MIT general circulation model simulations, including waves, eddies, and gyres. To achieve this, we employ Dynamic Mode Decomposition (DMD) to break down simulation snapshots into Koopman modes, with distinct exponential growth/decay rates and oscillation frequencies. Our objectives encompass evaluating DMD's efficacy in capturing known features, unveiling new elements, ranking modes, and exploring order reduction. We also introduce modifications to enhance DMD's robustness, numerical accuracy, and robustness of eigenvalues. DMD analysis yields a comprehensive understanding of flow patterns, internal wave formation, and the dynamics of the Strait of Gibraltar, its meandering behaviors, and the formation of a secondary gyre, notably the Western Alboran Gyre, as well as the propagation of Kelvin and coastal-trapped waves along the African coast. In doing so, it significantly advances our comprehension of intricate oceanographic phenomena and underscores the immense utility of DMD as an analytical tool for such complex datasets, suggesting that DMD could serve as a valuable addition to the toolkit of oceanographers.

This paper introduces a new method of discretization that collocates both endpoints of the domain and enables the complete convergence of the costate variables associated with the Hamilton boundary-value problem. This is achieved through the inclusion of an \emph{exceptional sample} to the roots of the Legendre-Lobatto polynomial, thus promoting the associated differentiation matrix to be full-rank. We study the location of the new sample such that the differentiation matrix is the most robust to perturbations and we prove that this location is also the choice that mitigates the Runge phenomenon associated with polynomial interpolation. Two benchmark problems are successfully implemented in support of our theoretical findings. The new method is observed to converge exponentially with the number of discretization points used.

1/f noise is a critical figure of merit for the performance of transistors and circuits. For two-dimensional devices (2D-FETs), and especially for applications in the GHz range where short-channel FETs are required, velocity saturation (VS) effect can result in the reduction of 1/f noise at high longitudinal electric fields. A new physics-based compact model is for the first time introduced for single- to few- layer 2D-FETs in this study, precisely validating 1/f noise experiments for various types of devices. The proposed model mainly accounts for the measured 1/f noise bias dependence as the latter is defined by different physical mechanisms. Thus, analytical expressions are derived, valid in all regions of operation in contrast to conventional approaches available in literature so far, accounting for carrier number fluctuation (DN), mobility fluctuation (Dmu}) and contact resistance (DR) effects based on the underlying physics that rules these devices. DN mechanism due to trapping/detrapping together with an intense Coulomb scattering effect, dominates 1/f noise from medium to strong accumulation region while Dmu, is also demonstrated to modestly contribute in subthreshold region. DR can also be significant in very high carrier density. The VS induced reduction of 1/f noise measurements at high electric fields, is also remarkably captured by the model. The physical validity of the model can also assist in extracting credible conclusions when conducting comparisons between experimental data from devices with different materials or dielectrics., Comment: Nanoscale, 2023, Advance Article

Objective. The COVID-19 pandemic has threatened to collapse hospital and ICU services, and it has affected the care programs for non-COVID patients. The objective was to develop a mathematical model designed to optimize predictions related to the need for hospitalization and ICU admission by COVID-19 patients. Design. Prospective study. Setting. Province of Granada (Spain). Population. Consecutive COVID-19 patients hospitalized, admitted to ICU, recovered and died from March 15 to September 22, 2020. Study variables. The number of patients infected with SARS-CoV-2 and hospitalized or admitted to ICU for COVID-19. Results. The data reported by hospitals was used to develop a mathematical model that reflects the flow of the population among the different interest groups in relation to COVID-19. This tool has allowed us to analyse different scenarios based on socio-health restriction measures, and to forecast the number of people infected, hospitalized and admitted to the ICU until May 2021. Conclusions. The mathematical model is capable of providing predictions on the evolution of the COVID-19 sufficiently in advance as to anticipate the peaks of prevalence and hospital and ICU care demands, and also the appearance of periods in which the care for non-COVID patients could be intensified., Comment: 23 pages, 5 figures, 2 tables, in Spanish

Low-frequency noise (LFN) variability in graphene transistors (GFETs) is for the first time researched in this work. LFN from an adequate statistical sample of long-channel solution-gated single-layer GFETs is measured in a wide range of operating conditions while a physics-based analytical model is derived that accounts for the bias dependence of LFN variance with remarkable performance. It is theoretically proved and experimentally validated that LFN deviations in GFETs stem from physical mechanisms that generate LFN. Thus, carrier number DN due to trapping/detrapping process and mobility fluctuations Dm which are the main causes of LFN, define its variability likewise as its mean value. DN accounts for an M-shape of normalized LFN variance versus gate bias with a minimum at the charge neutrality point (CNP) as it was the case for normalized LFN mean value while Dm contributes only near the CNP for both variance and mean value. Trap statistical nature is experimentally shown to differ from classical Poisson distribution at silicon-oxide devices, and this is probably caused by electrolyte interface in GFETs under study. Overall, GFET technology development is still in a premature stage which might cause pivotal inconsistencies affecting the scaling laws in GFETs of the same process.

In this paper, a detailed parameter extraction methodology is proposed for low-frequency noise (LFN) in single layer (SL) graphene transistors (GFETs) based on a recently established compact LFN model. Drain current and LFN of two short channel back-gated GFETs (L=300, 100 nm) were measured at lower and higher drain voltages, for a wide range of gate voltages covering the region away from charge neutrality point (CNP) up to CNP at p-type operation region. Current-voltage (IV) and LFN data were also available from a long channel SL top solution-gated (SG) GFET (L=5 um), for both p- and n-type regions near and away CNP. At each of these regimes, the appropriate IV and LFN parameters can be accurately extracted. Regarding LFN, mobility fluctuation effect is dominant at CNP and from there the Hooge parameter aH can be extracted while the carrier number fluctuation contribution which is responsible for the well-known M-shape bias dependence of output noise divided by squared drain current, also observed in our data, makes possible the extraction of the NT parameter related to the number of traps. In the less possible case of a Lambda-shape trend, NT and aH can be extracted simultaneously from the region near CNP. Away from CNP, contact resistance can have a significant contribution to LFN and from there the relevant parameter SDR^2 is defined. The LFN parameters described above can be estimated from the low drain voltage region of operation where the effect of Velocity Saturation (VS) mechanism is negligible. VS effect results in the reduction of LFN at higher drain voltages and from there the IV parameter hOmega which represents the phonon energy and is related to VS effect can be derived both from drain current and LFN data.