Efeito das dimensões dos corpos de prova na resistência à flexão de compósitos restauradores

The aim of this study was to evaluate the influence of specimen size, in comparison with the ISO Standard, on the three point flexural strength of resin composite restorative materials Filtek Supreme and Filtek Z-250. Forty specimens were fabricated for each material with the following length, width and thickness measurements (n = 10): 1) 20 × 2 × 2 mm (ISO 4049); 2) 10 × 2 × 1 mm; 3) 10 × 1 × 1 mm; 4) 8 × 0.8 × 0.8 mm. The composites were inserted in a single increment into two-piece metal device and light-polymerized. The specimens were dry stored at 37 ± 1 °C and protected from light for 7 days. After this period, flexural strength was measured by three-point flexure test using MTS 810 equipment, with a load cell of 10 kN at a speed of 0.5 mm/min. For the evaluated sizes, the results showed significant variability (p = 0.00) with values when compared with the ISO Standard (116.700 MPa), being statistically higher for the test specimens measuring 10 × 1 × 1 mm (142.530 MPa), similar for those of 10  ×  2  ×  1  mm (115.815 MPa) and lower for those of 8 × 0.8 × 0.8 mm (86.650 MPa). There was statistical equality (p = 0.08) for the studied composites (Filtek Supreme, 125.270 MPa; Filtek Z-250, 108.130 MPa). Specimens measuring 10 × 2 × 1 mm provided flexural strength values equivalent to those obtained in the sizes recommended by the ISO 4049 standard, with lower consumption of material, energy and time.

Development of human visual system analysis for the implementation of a new instrument for flicker measurement

Flicker is a power quality phenomenon that applies to cycle instability of light intensity resulting from supply voltage fluctuation, which, in turn can be caused by disturbances introduced during power generation, transmission or distribution. The standard EN 61000-4-15 which has been recently adopted also by the IEEE as IEEE Standard 1453 relies on the analysis of the supply voltage which is processed according to a suitable model of the lamp – human eye – brain chain. As for the lamp, an incandescent 60 W, 230 V, 50 Hz source is assumed. As far as the human eye – brain model is concerned, it is represented by the so-called flicker curve. Such a curve was determined several years ago by statistically analyzing the results of tests where people were subjected to flicker with different combinations of magnitude and frequency. The limitations of this standard approach to flicker evaluation are essentially two. First, the provided index of annoyance Pst can be related to an actual tiredness of the human visual system only if such an incandescent lamp is used. Moreover, the implemented response to flicker is “subjective” given that it relies on the people answers about their feelings. In the last 15 years, many scientific contributions have tackled these issues by investigating the possibility to develop a novel model of the eye-brain response to flicker and overcome the strict dependence of the standard on the kind of the light source. In this light of fact, this thesis is aimed at presenting an important contribution for a new Flickermeter. An improved visual system model using a physiological parameter that is the mean value of the pupil diameter, has been presented, thus allowing to get a more “objective” representation of the response to flicker. The system used to both generate flicker and measure the pupil diameter has been illustrated along with all the results of several experiments performed on the volunteers. The intent has been to demonstrate that the measurement of that geometrical parameter can give reliable information about the feeling of the human visual system to light flicker.

Analog Signal Acquisition and Conditioning for Near-Field Capacitive Communication and Active Combined EEG-EIT Monitoring

The work of the present thesis is focused on the implementation of microelectronic voltage sensing devices, with the purpose of transmitting and extracting analog information between devices of different nature at short distances or upon contact. Initally, chip-to-chip communication has been studied, and circuitry for 3D capacitive coupling has been implemented. Such circuits allow the communication between dies fabricated in different technologies. Due to their novelty, they are not standardized and currently not supported by standard CAD tools. In order to overcome such burden, a novel approach for the characterization of such communicating links has been proposed. This results in shorter design times and increased accuracy. Communication between an integrated circuit (IC) and a probe card has been extensively studied as well. Today wafer probing is a costly test procedure with many drawbacks, which could be overcome by a different communication approach such as capacitive coupling. For this reason wireless wafer probing has been investigated as an alternative approach to standard on-contact wafer probing. Interfaces between integrated circuits and biological systems have also been investigated. Active electrodes for simultaneous electroencephalography (EEG) and electrical impedance tomography (EIT) have been implemented for the first time in a 0.35 um process. Number of wires has been minimized by sharing the analog outputs and supply on a single wire, thus implementing electrodes that require only 4 wires for their operation. Minimization of wires reduces the cable weight and thus limits the patient's discomfort. The physical channel for communication between an IC and a biological medium is represented by the electrode itself. As this is a very crucial point for biopotential acquisitions, large efforts have been carried in order to investigate the different electrode technologies and geometries and an electromagnetic model is presented in order to characterize the properties of the electrode to skin interface.

Industrial accidents triggered by lightning: causes and consequences

Natural hazards affecting industrial installations could directly or indirectly cause an accident or series of accidents with serious consequences for the environment and for human health. Accidents initiated by a natural hazard or disaster which result in the release of hazardous materials are commonly referred to as Natech (Natural Hazard Triggering a Technological Disaster) accidents. The conditions brought about by these kinds of events are particularly problematic, the presence of the natural event increases the probability of exposition and causes consequences more serious than standard technological accidents. Despite a growing body of research and more stringent regulations for the design and operation of industrial activities, Natech accidents remain a threat. This is partly due to the absence of data and dedicated risk-assessment methodologies and tools. Even the Seveso Directives for the control of risks due to major accident hazards do not include any specific impositions regarding the management of Natech risks in the process industries. Among the few available tools there is the European Standard EN 62305, which addresses generic industrial sites, requiring to take into account the possibility of lightning and to select the appropriate protection measures. Since it is intended for generic industrial installations, this tool set the requirements for the design, the construction and the modification of structures, and is thus mainly oriented towards conventional civil building. A first purpose of this project is to study the effects and the consequences on industrial sites of lightning, which is the most common adverse natural phenomenon in Europe. Lightning is the cause of several industrial accidents initiated by natural causes. The industrial sectors most susceptible to accidents triggered by lightning is the petrochemical one, due to the presence of atmospheric tanks (especially floating roof tanks) containing flammable vapors which could be easily ignited by a lightning strike or by lightning secondary effects (as electrostatic and electromagnetic pulses or ground currents). A second purpose of this work is to implement the procedure proposed by the European Standard on a specific kind of industrial plant, i.e. on a chemical factory, in order to highlight the critical aspects of this implementation. A case-study plant handling flammable liquids was selected. The application of the European Standard allowed to estimate the incidence of lightning activity on the total value of the default release frequency suggested by guidelines for atmospheric storage tanks. Though it has become evident that the European Standard does not introduce any parameters explicitly pointing out the amount of dangerous substances which could be ignited or released. Furthermore the parameters that are proposed to describe the characteristics of the structures potentially subjected to lightning strikes are insufficient to take into account the specific features of different chemical equipment commonly present in chemical plants.

[Diagnosis and therapy of depression in the heart disease patient]

Even though depressions and depressive symptoms are frequently observed in patients with medical diseases, their psychological problems are often neither diagnosed nor treated. Diagnosis of mood state might be easy in isolated cases yet it often is not since the precise nature of normal mood cannot be expressed in quantitative terms. Furthermore, depression can only be diagnosed based on the doctor's clinical appraisal and the patient's own description of his/her complaints. There is no gold standard on which depressive symptoms can be based on--and further on, depression is not a diagnosis. Instead, it is a syndrome that calls for differential diagnoses before treatment can be offered. Diagnosing depressive comorbidity in patients with medical complaints is even more difficult because of the overlap between symptoms of depression and accompanying symptoms of the somatic illness e.g. lack of energy. Although depressive states have been known to be a risk factor for the prognosis of patients with coronary heart disease for a long time, there is a paucity of research about the therapy these patients undergo due to the fact that tricyclic anti-depressants can have cardiotoxic effects on patients with heart disease. The treatment of depression in these patients has become a much lower risk since the introduction of serotonin reuptake inhibitors. There is widespread evidence that depressive comorbidity has a negative impact on the prognosis of medical disorders. Despite the complex nature of diagnosing depression, proper diagnosis and treatment is increasingly important in internal medicine and especially cardiology.

Multiple Frequency Solidly Mounted BAW Filters

This paper reports the simultaneous fabrication of Receive and Transmit Bulk Acoustic Wave filters for the WCDMA standard on the same die. Both filters are based on Solidly Mounted Resonators using a common Bragg mirror, but with each having a specific piezoelectric film thickness. Electrical measurements reveal that the process steps required to provide the two different piezoelectric film thicknesses on the same die does not impact the electrical performances of resonators and filters and that this approach could thus be generalised to more than two filters.

Interface adaptor logic: A new model for interfacing peripherals in IP based designs

The introduction of standard on-chip buses has eased integration and boosted the production of IP functional cores. However, once an IP is bus specific retargeting to a different bus is time-consuming and tedious, and this reduces the reusability of the bus-specific IP. As new bus standards are introduced and different interconnection methods are proposed, this problem increases. Many solutions have been proposed, however these solutions either limit the IP block performance or are restricted to a particular platform. A new concept is presented that can connect IP blocks to a wide variety of interface architectures with low overhead. This is achieved through the use a special interface adaptor logic layer.

Executive characteristics and going concern opinions

Auditors have come under increased scrutiny over the past several years about the growing number of client failures without a warning in the form of a going-concern modified (GCM) audit opinion. Statement on Auditing Standards No. 59 requires auditors to evaluate whether substantial doubt exists on an audit client’s ability to continue as a going concern (AICPA 1988). My dissertation consists of three essays. ^ For the three essays, I empirically investigate issues related to GCM audit opinions and executive characteristics. Specifically, I examine the impact of executive tenure and gender on the issuance of GCM audit opinions. In addition, my dissertation addresses two other unique issues. Given that the Sarbanes-Oxley Act represents an important watershed event in the history and regulation of the accounting profession, I provide evidence about auditors’ propensities to issue GCM audit opinions in the post-SOX period. Further, I also expand extant research in this area by using multiple outcomes and thus go beyond the traditional use of bankruptcy alone as a tool to evaluate auditors’ GCM opinion. ^ The results indicate that, after controlling for other financial characteristics, GCM audit opinions are significantly more likely for firms that have CFOs with short tenure and/or for firms with a female CFO or CEO. However, when examining the association between executive characteristics and two types of reporting errors, the results vary with the type of reporting error. Overall, the results provide evidence that executive characteristics are associated with auditors' reporting decisions. ^

Shareholder ratification of the auditor and audit market competition

In my dissertation, I examine factors associated with firms’ submission of auditor selection for shareholder ratification and test if shareholder ratification of auditor selection is associated with the extent of price competition in the audit market (as measured by audit fees) and audit quality (as measured by clients’ earnings management). The dissertation is motivated from the recent recommendation of the U.S. Treasury’s Advisory Committee on Auditing Profession (ACAP) regarding the submission of auditor selection for shareholder ratification votes. The ACAP suggests that this practice may improve the competition in the audit market; yet, there is no empirical evidence supporting the ACAP’s recommendation. My dissertation attempts to fill the gap in the literature on an issue of current interest to the auditing profession. I find that firm size, CEO-Chair duality, insider ownership and institutional ownership are associated with the submission of auditor selection for shareholder ratification vote. However, I do not find an association between audit committee variables and the submission of auditor selection for shareholder ratification vote. The second essay investigates the association between auditor ratification and audit fees. Audit fees are higher in firms that submit auditor selection for shareholder ratification. The finding is not consistent with the increased price competition predicted by the ACAP. The third essay of my dissertation examine whether the submission of auditor selection for shareholder ratification is associated with earnings management. I find that firms that submit auditor selection for shareholder ratification are more likely to have lower level of earnings management. Overall, the results suggest that the same factors that are associated with higher quality monitoring also may be associated with the submission of auditor selection for shareholder ratification vote. The results call into question the one-size-fits-all approach recommended by the ACAP.

Shareholder Ratification of The Auditor and Audit Market Competition

In my dissertation, I examine factors associated with firms’ submission of auditor selection for shareholder ratification and test if shareholder ratification of auditor selection is associated with the extent of price competition in the audit market (as measured by audit fees) and audit quality (as measured by clients’ earnings management). The dissertation is motivated from the recent recommendation of the U.S. Treasury’s Advisory Committee on Auditing Profession (ACAP) regarding the submission of auditor selection for shareholder ratification votes. The ACAP suggests that this practice may improve the competition in the audit market; yet, there is no empirical evidence supporting the ACAP’s recommendation. My dissertation attempts to fill the gap in the literature on an issue of current interest to the auditing profession. I find that firm size, CEO-Chair duality, insider ownership and institutional ownership are associated with the submission of auditor selection for shareholder ratification vote. However, I do not find an association between audit committee variables and the submission of auditor selection for shareholder ratification vote. The second essay investigates the association between auditor ratification and audit fees. Audit fees are higher in firms that submit auditor selection for shareholder ratification. The finding is not consistent with the increased price competition predicted by the ACAP. The third essay of my dissertation examine whether the submission of auditor selection for shareholder ratification is associated with earnings management. I find that firms that submit auditor selection for shareholder ratification are more likely to have lower level of earnings management. Overall, the results suggest that the same factors that are associated with higher quality monitoring also may be associated with the submission of auditor selection for shareholder ratification vote. The results call into question the one-size-fits-all approach recommended by the ACAP.

Executive Characteristics and Going Concern Opinions

Auditors have come under increased scrutiny over the past several years about the growing number of client failures without a warning in the form of a going-concern modified (GCM) audit opinion. Statement on Auditing Standards No. 59 requires auditors to evaluate whether substantial doubt exists on an audit client’s ability to continue as a going concern (AICPA 1988). My dissertation consists of three essays. For the three essays, I empirically investigate issues related to GCM audit opinions and executive characteristics. Specifically, I examine the impact of executive tenure and gender on the issuance of GCM audit opinions. In addition, my dissertation addresses two other unique issues. Given that the Sarbanes-Oxley Act represents an important watershed event in the history and regulation of the accounting profession, I provide evidence about auditors’ propensities to issue GCM audit opinions in the post-SOX period. Further, I also expand extant research in this area by using multiple outcomes and thus go beyond the traditional use of bankruptcy alone as a tool to evaluate auditors’ GCM opinion. The results indicate that, after controlling for other financial characteristics, GCM audit opinions are significantly more likely for firms that have CFOs with short tenure and/or for firms with a female CFO or CEO. However, when examining the association between executive characteristics and two types of reporting errors, the results vary with the type of reporting error. Overall, the results provide evidence that executive characteristics are associated with auditors' reporting decisions.

Practical calculations for uniform external pressure buckling in cylindrical shells with stepped walls

Metal cylindrical storage structures of significant size, such as silos and vertical-axis tanks, are almost always constructed from many short cylindrical shells of different thickness as the stress resultants on the wall progressively increase towards the base. The resulting increases in thickness are always made in step changes using metal sheets of uniform thickness because of the availability of such source materials. The result is a shell with a stepped wall with multiple discrete steps in thickness. Such shells are very susceptible to buckling under external pressure when empty or partially filled, but the buckling mode may involve only part of the shell height due to the changes in shell thickness. These changes must therefore be accounted for within the design process. A new method of determining the critical buckling resistance of such shells was recently developed, and although it has been shown to be valid, the methodology for its application in practical design has not been set out or shown. This paper therefore briefly describes the new method and demonstrates the manner in which it can be used to produce rapid, safe assessments of cylindrical shells with a wide range of patterns of wall thickness changes. The results are then suitable for direct introduction into such documents as the European standard on metal shells [1] and the ECCS Recommendations [2].

Radiografía de los observatorios de medios en España: una herramienta ciudadana para la reforma mediática

Introducción: Desde finales del pasado siglo XX, los observatorios vienen jugando un papel muy destacado entre las instituciones orientadas a la reforma mediática por cuanto suponen una vital herramienta para el análisis y fiscalización ciudadana de los medios. En este contexto, la investigación plantea una cartografía pionera de los observatorios de medios en España e intenta sistematizar su origen, evolución y sus principales características, entre otras: objetivos, promotores y ámbitos de especialización. Metodología: Partiendo de una extensa revisión documental, el estudio construye un censo de 28 observatorios que se analizan a partir de un protocolo de observación y una entrevista cualitativa a una decena de responsables de las distintas iniciativas. Resultados y conclusiones: Los resultados demuestran la existencia de un panorama heterogéneo de experiencias entre las que predominan las fiscalizadoras y promovidas por universidades. No obstante, los observatorios se caracterizan por su difícil sostenibilidad y por una actividad investigadora discontinua y poco constante.

Manual para la aplicación de las normas y procedimientos de auditoría de cumplimiento de obligaciones tributarias aplicables en la auditoría fiscal.

Toda profesión debe establecer las más altas normas de calidad en el ejercicio de su trabajo, ya que personas incapacitadas para juzgarlo por sí mismas confían en él, a veces con consecuencias irreparables. Es evidentemente imposible (e indeseable) relevar al contador de su responsabilidad profesional estableciendo reglas detalladas de conducta, ya que la responsabilidad profesional es una de las cualidades que las normas mismas deben salvaguardar, por lo que éstas deben ser cuidadosamente definidas y clasificadas para que sirvan como la guía más clara y útil al auditor en el desarrollo de su trabajo diario. La pugna entre el ejercicio de la responsabilidad profesional individual y la aplicación de regla específica de conducta se presenta en cada aspecto de la contabilidad y de la auditoria, la solución es clara en los extremos: por un lado, el contador no puede renunciar a sus responsabilidad profesional y, por otro, es imposible dictar reglas que cubran todas las circunstancias posibles, la tensión entre estos extremos crea controversia y ansiedad; el problema está en dictaminar cuánta uniformidad y rigidez se puede establecer mediante los principios de contabilidad, y qué tanta flexibilidad puede dejarse al juicio personal; o hasta qué grado debe definirse detalladamente el alcance de las pruebas y los procedimientos de auditoria, y hasta qué limite debe dejarse al juicio pragmático del auditor, etc. Aunque el punto específico de discusión cambie de tiempo en tiempo, es probable que nunca se dé por concluida esta polémica. Los miembros del Instituto Americano de Contadores Públicos (American Institute of Certified Public Accountants) han adoptado oficialmente 10 requisitos básicos conocidos en conjunto como “Normas de Auditoria Generalmente Aceptadas”. Estas normas se ampliaron a principios de 1973 en el boletín Nº 1 del Pronunciamiento de las normas de auditoria Statement on Auditing Standards (SAS) llamado “Codificación de las Normas y Procedimientos de Auditoria”. La solidez y utilidad de las normas han quedado demostradas por su permanencia: 9 de ellas fueron originalmente adoptadas en 1948 y desde entonces básicamente no han cambiado (aunque ha tomado mucho tiempo entender algunas de ellas), la décima fue adoptada unos años después, aunque el principio básico que la rige existe desde entonces y quizá desde antes. Sin embargo, no existía ningún tipo de normativa definida mediante la cual el auditor pueda definir su responsabilidad como auditor fiscal, y que a la vez lo oriente a dictaminar con apego a las Normas de Auditoria Generalmente Aceptadas. Los procedimientos que en nuestro trabajo se adopta nos permitieron determinar los métodos más adecuados para llevar a cabo los exámenes de auditoría fiscal ejecutados por el auditor Fiscal Independiente, del contribuyente sobre la base de las leyes tributarias y a la generación de la documentación respectiva que ampare la evaluación del control interno. Por lo que el presente trabajo está enfocado a la práctica de la Auditaría Fiscal, específicamente en la observancia de la Norma de Cumplimiento de Obligaciones Tributarias y la elaboración de un documento que sirva de guía para su aplicación en concordancia con los procedimientos de este tipo de auditoría, que será de gran ayuda al contador público. Considerando que en el país no existe suficiente bibliografía especializada de la auditoría fiscal, se ha elaborado el presente trabajo para profundizar en el aspecto técnico, como un aporte en la materia. Se considera de utilidad social debido a que la aplicación de la norma dará validez y profesionalismo a su trabajo, el trabajo pretende diseñar métodos, procedimientos y cuestionarios de control interno con enfoque al cumplimiento de la norma, que pueda aplicarse y adaptarse a todo tipo de empresa. Esto le otorga a la presente investigación una gran importancia por su aporte a la comunidad de contadores públicos, ya que este tema ha sido tratado en forma mínima.

A importância da informação financeira para o processo de tomada de decisão em empresas de estrutura familiar

Em Portugal, assim como um pouco por todo o mundo, a maioria das empresas são de cariz familiar. A predominância destas empresas faz com que as mesmas tenham um papel relevante na economia, seja pela criação e distribuição de riqueza seja pela criação de emprego. A importância que se lhes reconhece constituiu o fator ou motivação suficiente para desenvolver este trabalho que, com base numa metodologia preferencialmente quantitativa, aplicada a um conjunto de empresas familiares associadas da Associação Portuguesa das Empresas Familiares, se propõe averiguar se estas empresas atribuem importância à informação financeira no processo da tomada de decisão. Utilizou-se como instrumento de recolha de informação um inquérito por questionário e cujos resultados permitiram desenvolver uma análise descritiva exploratória e aplicar testes estatísticos não paramétricos. O trabalho realizado permitiu recolher evidência suficiente para concluir sobre a importância das demonstrações financeiras para o processo de tomada de decisão, em particular no que respeita à utilização do balanço e da demonstração dos resultados. Não foi, porém, possível identificar um padrão sobre as demonstrações financeiras preparadas em função do tipo de norma contabilística aplicável e do setor de atividade, nem sobre a importância atribuída à informação financeira em função da dimensão da empresa. Foi possível concluir que a informação financeira é, fundamentalmente, utilizada para avaliar os impactos financeiros, apoiar na gestão corrente, tomar decisões de investimento e cumprir com obrigações fiscais, sendo muito evidente a importância que as empresas familiares atribuem à informação financeira como forma de dar cumprimento às obrigações fiscais.