Impact of Gamma Radiation on Dynamic RDSON Characteristics in AlGaN/GaN Power HEMTs

GaN high-electron-mobility transistors (HEMTs) are promising next-generation devices in the power electronics field which can coexist with silicon semiconductors, mainly in some radiation-intensive environments, such as power space converters, where high frequencies and voltages are also needed. Its wide band gap (WBG), large breakdown electric field, and thermal stability improve actual silicon performances. However, at the moment, GaN HEMT technology suffers from some reliability issues, one of the more relevant of which is the dynamic on-state resistance (RON_dyn) regarding power switching converter applications. In this study, we focused on the drain-to-source on-resistance (RDSON) characteristics under 60Co gamma radiation of two different commercial power GaN HEMT structures. Different bias conditions were applied to both structures during irradiation and some static measurements, such as threshold voltage and leakage currents, were performed. Additionally, dynamic resistance was measured to obtain practical information about device trapping under radiation during switching mode, and how trapping in the device is affected by gamma radiation. The experimental results showed a high dependence on the HEMT structure and the bias condition applied during irradiation. Specifically, a free current collapse structure showed great stability until 3.7 Mrad(Si), unlike the other structure tested, which showed high degradation of the parameters measured. The changes were demonstrated to be due to trapping effects generated or enhanced by gamma radiation. These new results obtained about RON_dyn will help elucidate trap behaviors in switching transistors

How do market imperfections affect working capital management?

This paper examines whether Working Capital Management (WCM) is sensitive to market imperfections such as asymmetric information, agency conflicts or financial distress. We find that firms have a target investment in working capital and that they take decisions in order to achieve this. In addition, the results appear to support the hypothesis that the working capital competes with investment in fixed assets for the funds of the firms when they have financial constraints. Finally, we also find that WCM depends on bargaining power and other financial factors such as the availability of internal finance, cost of financing and access to capital markets. Este artículo analiza si la gestión del capital circulante está afectada por las imperfecciones de mercado tales como la asimetría informativa, los conflictos de agencia o las dificultades financieras. Los resultados muestran que las empresas tienen un nivel de inversión en capital circulante objetivo y toman decisiones con el fin de alcanzarlo. Además, los resultados parecen apoyar la hipótesis de que el capital circulante compite con los activos fijos por los fondos de las empresas cuando éstas tienen restricciones financieras. Finalmente, la gestión del capital circulante depende del poder de negociación y otros factores financieros tales como la disponibilidad de financiación interna, el coste de financiación y el acceso a los mercados de capitales.ciclo de efectivo, gestión del capital circulante, imperfecciones de mercado, datos de panel net trade cycle, working capital management, market imperfections, panel data

ENDEUDAMIENTO A CORTO PLAZO EN LAS PYMES ESPAÑOLAS

This paper analyses the debt maturity structure of the small and middle sizedfirms using the trade-off reward risk associated to the use of short-term loans.Therefore, a sample of 11.533 small and middle Spanish manufacturing firms from year1997 through 2001 was used. The results of our study show that short-term loans aremore frequent in firms with greater financial strength and greater financial flexibility,major growth options and when the interest cost differential between short-long terms ismore pronounced. Also, the firm size seems to have an influence on the level of shorttermloans, it being higher in the smaller firms. Este trabajo analiza la estructura de vencimiento de la deuda en las PYMEs a partir del trade-off rentabilidad riesgo asociado al uso de recursos ajenos a corto plazo. Para ello, se ha utilizado una muestra de 11.533 pequeñas y medianas empresas manufactureras españolas durante el periodo 1997-2001. Los resultados obtenidos muestran que el endeudamiento a corto plazo es mayor en aquellas empresas que presentan una mayor solvencia y flexibilidad financiera, mayores oportunidades de crecimiento y cuando el diferencial de tipos de interés corto-largo es más acentuado. Así mismo, el tamaño de las sociedades también parece influir en los niveles de endeudamiento a corto plazo, siendo mayor en las empresas más pequeñas.Pymes, vencimiento de la deuda, solvencia financiera, flexibilidad financiera. SMEs, debt maturity, financial solvency, financial flexibility.

LA TESORERIA EN LA EMPRESA Y SUS DETERMINANTES

This paper analyzes the determinants of the corporate cash holding for a sampleof companies listed in the Spanish stock market. The results show that the firms have acorporate cash holding target level, and that this level is greater in companies withgreater cash flows. On the other hand, cash holding is negatively related to size, growthoptions, leverage, bank debt and liquid assets. Finally, the ownership structure alsoseems to affect the cash holdings. Este trabajo analiza los factores explicativos de la tesorería para una muestra de empresas cotizadas en el mercado continuo español. Los resultados obtenidos revelan que las empresas poseen un nivel de tesorería objetivo al que pretenden converger, y que dicho nivel es mayor en las sociedades con mayores flujos de caja. Por el contrario, el nivel de efectivo se ve reducido con el tamaño, con las oportunidades de crecimiento, con el nivel de endeudamiento, con el uso de deuda bancaria y con la liquidez de la empresa. Además, la estructura de propiedad también parece influir sobre los niveles de efectivo.Tesorería, liquidez, datos de panel. cash, liquidity, panel data

Determinants of working capital management

This paper analyzes the determinants of working capital management (WCM) for a sample of Spanish firms during the period 1997-2004. We find that firms have a target investment in working capital and that they take decisions in order to achieve this. The results appear to support the hypothesis that the working capital competes with investment in fixed assets for the funds of the firms when they have financial constraints. Finally, we also find that WCM depends on bargaining power and other financial factors such as the availability of internal finance, cost of financing and financial constraints.Research Agency of the Spanish Government ECO2008-06179/ECO

Enabling Practical IPsec authentication for the Internet

On the Move to Meaningful Internet Systems 2006: OTM 2006 Workshops (First International Workshop on Information Security (IS'06), OTM Federated Conferences and workshops). Montpellier, Oct,/Nov. 2006There is a strong consensus about the need for IPsec, although its use is not widespread for end-to-end communications. One of the main reasons for this is the difficulty for authenticating two end-hosts that do not share a secret or do not rely on a common Certification Authority. In this paper we propose a modification to IKE to use reverse DNS and DNSSEC (named DNSSEC-to-IKE) to provide end-to-end authentication to Internet hosts that do not share any secret, without requiring the deployment of a new infrastructure. We perform a comparative analysis in terms of requirements, provided security and performance with state-of-the-art IKE authentication methods and with a recent proposal for IPv6 based on CGA. We conclude that DNSSEC-to-IKE enables the use of IPsec in a broad range of scenarios in which it was not applicable, at the price of offering slightly less security and incurring in higher performance costs.Universidad de Montpellier IIPublicad

Acquisition of financial management skills in the new framework for adaptation to the EHEA. Póster

One of the main consequences of adapting to the European Higher Education Area (EHEA) is the replacement of traditional teaching methods, based almost entirely on the lecture, with new methodologies where active participation on the part of the students is a key part of the teaching-learning process. It is, therefore, of interest to offer empirical evidence showing that the new teaching methods employed really do serve to improve the results of the students in the acquisition of skills. The aim of this paper is, therefore, to assess the results obtained from bringing in the new EHEA, compared to those obtained under the traditional teaching system. With the above aim in mind, we analysed the results from the two existing groups of students studying Financial Management I of the Degree in Business Administration and Management (academic year 2009-10) at the Faculty of Economics and Business of the University of Murcia. The first group comprised students who had followed the course under the traditional lecture-based teaching system. The second group was made up of students taking part in the innovation project being run by the Faculty of Economics and Business. EHEA teaching methodologies and materials have been employed in the second group. Besides the lecture and the practical class, the following teaching methodologies have been employed: problem-based learning, workshops on problems, group tutorials, group work and participative models. The first group was assessed purely on the basis of an end of semester examination, while in the case of the second group, the final examination counted for 60% of the mark, 30% corresponded to individual work and group practical work and 10% to participation in class and responses to questions posed by the teacher. It should be highlighted that the final examination was the same for both groups, so the comparison o results is free of bias in that aspect. The results show that higher percentage of passes in the group with innovative teaching – 93.75% versus 48.19% in the lecture-based class group. The average grade was also higher – 7.08 over 10 versus 4.52 over 10. These differences are significant (t statistic 6.382 for the means difference test). In order to rule out the possibility of these better results being due to the assessment awarded for the non similar parts of the examination, a comparison was also made of the marks obtained exclusively in the examination common to both groups. While the number of passes (75%) and the average mark of the group in the innovative method (6 over 10) fall, the results remain significantly better than those of the lecture-based classes group (t statistic for the difference in mean marks was 2.485).Campus Mare Nostrum, Universidad Politécnica de Cartagena, Universidad de Murcia, Región de Murci

Financing of working capital requirement, financial flexibility and SME performance

This paper investigates the relation between the financing strategies of working capital requirement and firm performance for the period 1997 to 2012. Using the two-step generalized method of moments estimator, we find that a suitable financing strategy can help firms improve their performance. Moreover, the results indicate that the working capital requirement financing-performance relation changes during a financial crisis. Finally, we also find that this relation depends on a firm’s financial flexibility. The findings are of interest for managers and researchers and show that managers should not only be concerned about investing in working capital requirement but also consider how this investment is to be financed. To the best of our knowledge, this is the first paper to analyse how the financing strategy selected by firms to finance their working capital requirement affects their performance

On the Performance of Interleavers for Quantum Turbo Codes

Quantum turbo codes (QTC) have shown excellent error correction capabilities in the setting of quantum communication, achieving a performance less than 1 dB away from their corresponding hashing bounds. Existing QTCs have been constructed using uniform random interleavers. However, interleaver design plays an important role in the optimization of classical turbo codes. Consequently, inspired by the widely used classical-to-quantum isomorphism, this paper studies the integration of classical interleaving design methods into the paradigm of quantum turbo coding. Simulations results demonstrate that error floors in QTCs can be lowered significantly, while decreasing memory consumption, by proper interleaving design without increasing the overall decoding complexity of the system

VNUML vs GNS3 en el desarrollo de laboratorios de redes virtuales

El aprendizaje práctico de redes de computadores es reconocido como un proceso crítico que permite a los estudiantes consolidar los conceptos introducidos en las lecciones teóricas. En este sentido, las tecnologías de virtualización están adquiriendo gran relevancia debido a que permiten desarrollar laboratorios de redes de computadores con un reducido coste de despliegue y gestión. Este artículo presenta un análisis comparativo entre GNS3 y VNUML, que son herramientas de virtualización open-source que han sido empleadas para el desarrollo de laboratorios de red virtuales para llevar a cabo el proceso de enseñanza-aprendizaje en las asignaturas Arquitectura de Redes y Arquitectura de Redes Avanzadas del Grado en Ingeniería Informática impartido en la Universidad de Murcia. El estudio presenta las principales ventajas y/o deficiencias de cada herramienta tanto para profesores como alumnos y se identifican los escenarios en los que parece más adecuada su utilización.SUMMARY -- The practical learning of computer networks is known to be a critical process in order to allow students to consolidate the concepts introduced in theoretical lessons. In this sense, virtualization technologies are becoming popular since they allow to set up a computer network laboratory with a reduced deployment and management cost. This paper presents a comparative analysis performed between GNS3 and VNUML, which are open-source tools for virtualization that have been used for developing virtual network laboratories that support the teaching-learning process in the Networks Architecture and Advanced Networks Architecture subjects of the Computer Engineering degree at the University of Murcia. The study presents the main advantages and/or deficiencies of each tool not only for professors but also for students and identifies the scenarios where the use of each tool seems to be more appropriate.Peer Reviewe