Unknown Radial Distortion Centers in Multiple View Geometry Problems

The radial undistortion model proposed by Fitzgibbon and the radial fundamental matrix were early steps to extend classical epipolar geometry to distorted cameras. Later minimal solvers have been proposed to find relative pose and radial distortion, given point correspondences between images. However, a big drawback of all these approaches is that they require the distortion center to be exactly known. In this paper we show how the distortion center can be absorbed into a new radial fundamental matrix. This new formulation is much more practical in reality as it allows also digital zoom, cropped images and camera-lens systems where the distortion center does not exactly coincide with the image center. In particular we start from the setting where only one of the two images contains radial distortion, analyze the structure of the particular radial fundamental matrix and show that the technique also generalizes to other linear multi-view relationships like trifocal tensor and homography. For the new radial fundamental matrix we propose different estimation algorithms from 9,10 and 11 points. We show how to extract the epipoles and prove the practical applicability on several epipolar geometry image pairs with strong distortion that - to the best of our knowledge - no other existing algorithm can handle properly.

One-sided Radial-Fundamental Matrix Estimation

For modern consumer cameras often approximate calibration data is available, making applications such as 3D reconstruction or photo registration easier as compared to the pure uncalibrated setting. In this paper we address the setting with calibrateduncalibrated image pairs: for one image intrinsic parameters are assumed to be known, whereas the second view has unknown distortion and calibration parameters. This situation arises e.g. when one would like to register archive imagery to recently taken photos. A commonly adopted strategy for determining epipolar geometry is based on feature matching and minimal solvers inside a RANSAC framework. However, only very few existing solutions apply to the calibrated-uncalibrated setting. We propose a simple and numerically stable two-step scheme to first estimate radial distortion parameters and subsequently the focal length using novel solvers. We demonstrate the performance on synthetic and real datasets.

A mobile systems interface protocol

Recent progresses in the software development world has assisted a change in hardware from heavy mainframes and desktop machines to unimaginable small devices leading to the prophetic "third computing paradigm", Ubiquitous Computing. Still, this novel unnoticeable devices lack in various capabilities, like computing power, storage capacity and human interface. Connectivity associated to this devices is also considered an handicap which comes generally associated expensive and limited protocols like GSM and UMTS. Considering this scenario as background, this paper presents a minimal communication protocol introducing better interfaces for limited devices. Special attention has been paid to the limitations of connectivity, storage capacity and scalability of the developed software applications. Illustrating this new protocol, a case-study is presented addressing car sensors communicating with a central

Factors Influencing the Implementation of the Balanced Scorecard in Portugal: Empirical Evidence From Privately Owned and Publicly Owned Organizations

In this paper we aim to identify and analyze a set of variables that can potentially influence the adoption and knowledge of the Balanced Scorecard (BSC) in Portugal. Hypotheses were tested using data obtained from a questionnaire sent to 591 publicly-owned organizations (local governments, municipal corporations and hospitals) and 549 privately-owned organizations (large companies and small and medium enterprises) in Portugal. The results allow us to conclude that although the majority of respondents claimed to know the BSC, its use in Portugal is still limited and very recent, particularly in the public sector organizations. However, it should be noted that its use has increased in Portugal in recent years. The study also reveals that in spite of the noticeable differences between public and private sector, the BSC is used in the public sector after a few adjustments to the traditional model. Using as theoretical framework the contingency and institutional theories, we found that decentralization, vertical differentiation and the degree of higher education are associated with the implementation of the BSC.

Divulgação de informação sobre Activos Intangíveis, Concentrações de Actividades Empresariais e Goodwill: evidência empírica nas empresas cotadas na Bolsa de Valores Portuguesa.

This paper analyzes the level of disclosure of Intangible Assets, Business Combinations and Goodwill in the consolidated financial statements and its explanatory factors. We have analyzed the annual reports of companies listed on Euronext Lisbon for the year 2010 and have created a Disclosure Index which allows to measure the level of disclosure for each company in this area, based on the existing accounting standards. In order to identify the association between the level of disclosure and its determinants, we have tested several hypotheses which explain the degree of disclosure. The results evidences, company’s size, industry, leverage and audit firms belonging to Big 4as explanatory factors. Only the size presentsa positive association with disclosure index, confirming the hypothesis which establishes that the level of disclosure about Intangible Assets, Business Combinations and Goodwill is greater in larger companies. The remaining explanatory variables presenta negative association with disclosure level.

Factores explicativos da divulgação de informação sobre instrumentos derivados: evidência empírica no mercado de capitais português, em 2008

This study analyses the determinants of the derivative instruments disclosure level by Portuguese listed companies. It is built a disclosure index to measure the disclosure level using the Consolidated Annual Reports for 2008. The hypotheses have been tested through a linear regression model using the disclosure index as the dependent variable and companies’ characteristics as independent variables. Multivariate results suggest that firm size, quality of the external auditor, belonging to PSI 20, the market to book value ratio and the percentage of capital hold by the board of directors are associated with the disclosure level.

Factores relativos al entorno, recursos humanos y sistemas de información y gestión en la adopción del cuadro de mando integral en organizaciones portuguesas

In this paper we aim to identify and analyze a set of variables that can potentially influence the adoption of the Balanced Scorecard (BSC) in Portuguese public and private organizations. These variables are related to the environment (perception of environmental uncertainty), with human resources (support of top management) and, information and management systems (strategic map design and establishment of cause-effect relationships between indicators and perspectives of the BSC). Hypotheses were tested using data obtained from a questionnaire sent to 591 publicly-owned organizations and 549 privately-owned organizations in Portugal, with an overall response rate of 31.3%. The results allow us to conclude that the top management commitment, the development of strategy maps and the establishment of cause-effect relationships are factors that are associated with the implementation of the BSC.

Determinant factors of the implementation of the balanced scorecard in Portugal: empirical evidence in public and private organizations

In this article we aim to identify and analyze a set of variables that can potentially influence the adoption of the Balanced Scorecard (BSC)in Portugal. Hypotheses were tested using data obtained from a questionnaire sent to 591 publicly-owned organizations (local governments, municipal corporations and hospitals) and 549 privately-owned organizations (large companies and small and medium enterprises) in Portugal, with an overall response rate of 31.3%. The results allow us to conclude that although the majority of respondents claimed to know the BSC, its use in Portugal is still limited and very recent, particularly in the public sector organizations. However, it should be noted that its use has increased in Portugal in recent years. Using as theoretical framework the contingency and institutional theories, we found that decentralization, vertical differentiation and the degree of higher education are associated with the implementation of the BSC.

La influencia de factores relativos a la estrategia organizativa y al entorno en la adopción del cuadro de mando integral en empresas portuguesas

In this article we aim to identify and analyze a set of variables related to the organizational and environ-mental strategy that can potentially influence the adoption of the Balanced Scorecard (BSC) in Portuguesecompanies of different sizes. Hypotheses were tested using data obtained from a questionnaire sent to549 privately-owned Portuguese organizations (small and medium enterprises and large companies),with an overall response rate of 28.2%. The results allow us to conclude that the BSC is independent ofthe activity/industry in which the organization operates. Furthermore, we have found that organizationsthat follow a defensive strategy attach greater importance to the BSC financial perspective or equiva-lent. On the other hand, we did not find empirical evidence regarding the possible relationship betweenthe BSC, the type of strategy adopted by the organization, the phase/stage of the life cycle in which theorganization is located, and the environmental intensity competition.

Comissão de fiscalização e disciplina do sindicato nacional do ensino superior (CFD/SNESup): quem somos, o que temos feito e para que serve?

A Comissão de Fiscalização e Disciplina, como o próprio nome indica, serve para fiscalizar e disciplinar, no caso de necessidade, adequação, proporcionalidade, sempre com uma intervenção mínima. De acordo com o art. 8º/6 dos Estatutos do SNESup cabe à CFD declarar a perda ou suspensão compulsiva da qualidade de associado na sequência de processo disciplinar, em virtude de incumprimento grave dos respectivos deveres. Abstract: The Audit and Discipline, as its name implies, is to supervise and regulate, in case of necessity, appropriateness, proportionality, always with minimal intervention. According to art. 8/6 of the Statute SNESup it is for the CFD to confiscate or forced suspension of membership in the disciplinary procedure, due to a serious breach of his duties.

Hand-held robotic device for laparoscopic surgery and training

Laparoscopic surgery (LS) has revolutionized traditional surgical techniques introducing minimally invasive procedures for diagnosis and local therapies. LSs have undeniable advantages, such as small patient incisions, reduced postoperative pain and faster recovery. On the other hand, restricted vision of the anatomical target, difficult handling of the surgical instruments, restricted mobility inside the human body, need of dexterity to hand-eye coordination and inadequate and non-ergonomic surgical instruments may restrict LS only to more specialized surgeons. To overcome the referred limitations, this work presents a new robotic surgical handheld system – the EndoRobot. The EndoRobot was designed to be used in clinical practice or even as a surgical simulator. It integrates an electromechanical system with 3 degrees of freedom. Each degree can be manipulated independently and combined with different levels of sensitivity allowing fast and slow movements. As other features, the EndoRobot has battery power or external power supply, enables the use of bipolar radiofrequency to prevent bleeding while cutting and allows plug-and-play of the laparoscopic forceps for rapid exchange. As a surgical simulator, the system was also instrumented to measure and transmit, in real time, its position and orientation for a training software able to monitor and assist the trainee’s surgical movements.

Preliminary clinical trial in percutaneous nephrolithotomy using a real-time navigation system for percutaneous kidney access

Background: Precise needle puncture of renal calyces is a challenging and essential step for successful percutaneous nephrolithotomy. This work tests and evaluates, through a clinical trial, a real-time navigation system to plan and guide percutaneous kidney puncture. Methods: A novel system, entitled i3DPuncture, was developed to aid surgeons in establishing the desired puncture site and the best virtual puncture trajectory, by gathering and processing data from a tracked needle with optical passive markers. In order to navigate and superimpose the needle to a preoperative volume, the patient, 3D image data and tracker system were previously registered intraoperatively using seven points that were strategically chosen based on rigid bone structures and nearby kidney area. In addition, relevant anatomical structures for surgical navigation were automatically segmented using a multi-organ segmentation algorithm that clusters volumes based on statistical properties and minimum description length criterion. For each cluster, a rendering transfer function enhanced the visualization of different organs and surrounding tissues. Results: One puncture attempt was sufficient to achieve a successful kidney puncture. The puncture took 265 seconds, and 32 seconds were necessary to plan the puncture trajectory. The virtual puncture path was followed correctively until the needle tip reached the desired kidney calyceal. Conclusions: This new solution provided spatial information regarding the needle inside the body and the possibility to visualize surrounding organs. It may offer a promising and innovative solution for percutaneous punctures.

Validation of percutaneous puncture trajectory during renal access using 4D ultrasound reconstruction

Background: An accurate percutaneous puncture is essential for disintegration and removal of renal stones. Although this procedure has proven to be safe, some organs surrounding the renal target might be accidentally perforated. This work describes a new intraoperative framework where tracked surgical tools are superimposed within 4D ultrasound imaging for security assessment of the percutaneous puncture trajectory (PPT). Methods: A PPT is first generated from the skin puncture site towards an anatomical target, using the information retrieved by electromagnetic motion tracking sensors coupled to surgical tools. Then, 2D ultrasound images acquired with a tracked probe are used to reconstruct a 4D ultrasound around the PPT under GPU processing. Volume hole-filling was performed in different processing time intervals by a tri-linear interpolation method. At spaced time intervals, the volume of the anatomical structures was segmented to ascertain if any vital structure is in between PPT and might compromise the surgical success. To enhance the volume visualization of the reconstructed structures, different render transfer functions were used. Results: Real-time US volume reconstruction and rendering with more than 25 frames/s was only possible when rendering only three orthogonal slice views. When using the whole reconstructed volume one achieved 8-15 frames/s. 3 frames/s were reached when one introduce the segmentation and detection if some structure intersected the PPT. Conclusions: The proposed framework creates a virtual and intuitive platform that can be used to identify and validate a PPT to safely and accurately perform the puncture in percutaneous nephrolithotomy.