Comparison of Test and Finite Element Analysis for Two Full-Scale Helicopter Crash Tests

Finite element analyses have been performed for two full-scale crash tests of an MD-500 helicopter. The first crash test was conducted to evaluate the performance of a composite deployable energy absorber under combined flight loads. In the second crash test, the energy absorber was removed to establish the baseline loads. The use of an energy absorbing device reduced the impact acceleration levels by a factor of three. Accelerations and kinematic data collected from the crash tests were compared to analytical results. Details of the full-scale crash tests and development of the system-integrated finite element model are briefly described along with direct comparisons of acceleration magnitudes and durations for the first full-scale crash test. Because load levels were significantly different between tests, models developed for the purposes of predicting the overall system response with external energy absorbers were not adequate under more severe conditions seen in the second crash test. Relative error comparisons were inadequate to guide model calibration. A newly developed model calibration approach that includes uncertainty estimation, parameter sensitivity, impact shape orthogonality, and numerical optimization was used for the second full-scale crash test. The calibrated parameter set reduced 2-norm prediction error by 51% but did not improve impact shape orthogonality

Spinal Tuberculosis. Case Report and Review of the Literature

A partir de uma invulgar apresentação clínica e radiológica de um caso de tuberculose (TB) vertebral, fazemos uma revisão da literatura sobre infecção tuberculosa da coluna. Destacam-se alguns aspectos epidemiológicos relativamente à infecção por Mycobacterium Tuberculosis em geral e à sua localização vertebral em particular, incluindo-se os dados disponíveis respeitantes ao nosso país. São ainda focados os mecanismos patogénicos da infecção óssea, considerando-se 3 padrões de lesão vertebral cada um com diferentes aspectos radiológicos e diferentes consequências clínicas

Solar thermal collector yield: experimental validation of calculations based on steady-state and quasi-dynamic test methodologies

The characterization of collector efficiency is the fundamental tool for long term calculation of collector yield. It is, thus, one of the most important inputs in software tools aiming the design of solar thermal systems. Presently two test methodologies are available for characterization of the efficiency of glazed collectors: i) steady state test and ii) quasi-dynamic test, methodologies based in different model approaches to a solar collector, providing different collector efficiency curve parameters and, consequently, imposing different power calculation algorithms. Moreover, Horta et al (2008) demonstrated that the use of the collector efficiency curve derived from steady state test method is not enough for a thorough characterization of the long term performance of a collector. The present work takes into account the introduction of the above referred test methodologies in the European Test Standard for Solar Thermal Collectors, and aims at clarifying how each test results should be used in long term thermal performance calculations. The paper presents a synthesis of the different efficiency parameters provided by each test methodology and corresponding algorithms, applicable in the calculation of delivered power. Application of these algorithms to two days of measured data allows for a comparison of the results obtained with these different methodologies. For validation purposes, results of tests performed on a CPC type collector with a concentration ratio C=1.72 are used. Measurement sequences are used to validate the calculation of power delivered by the collector using both algorithms based on steady-state methodology (with and without correction) and quasi-dynamic methodology

Skilled unemployment and the creation of academic spin-offs: a recession-push hypothesis

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Homophily in higher education research: A perspective based on co-authorships

Research collaborations are the norm in science today, and are usually evaluated using co-authorships as the unit of analysis. Research collaborations have been typically analyzed using a mapping perspective that focuses on countries, institutions, or individuals, or by assessments of the determinants of research collaboration, i.e., who engages in collaborations and who collaborates the most. One analytical perspective that has been used less frequently is the homophily perspective, which attempts to understand the likelihood of research collaborations based on the similarity of collaborators’ preferences and attributes. In addition, compared to studies focused on the fields of the natural and exact sciences, engineering, and the health sciences, research collaborations in the social sciences have been underexamined in the literature, despite the growing numbers of social scientists who engage in such collaborations. This study assessed homophily with respect to geographical, ascribed, acquired and career-related attributes in co-authorships in the social sciences, based on a co-authorship matrix of 913 higher education researchers. The findings showed that geographic and institutional attributes were by far the most powerful homophilic drivers of collaborations, suggesting the importance of physical proximity, national incentives, and shared culture, language, and identity. Another driver was the similarity of acquired attributes, particularly certain preferences regarding research agendas; these absorbed the residual explanatory power that ascribed attributes such as gender or age had in co-authorship preferences. The study is novel in its analysis of the extent to which similarities in the research agendas of researchers predicted co-authorship. The findings indicate the need for further co-authorship homophily analyses around a broader set of acquired attributes and the trajectories that lead to them.info:eu-repo/semantics/acceptedVersio

Syndrome in question

Neurofibromatosis is extremely variable in its presentation. Segmental neurofibromatosis (SNF), which corresponds to NF-type 5 in the Riccardi classification, is a rare disorder. It may go unrecognized if few lesions are observed. We present a case of segmental neurofibromatosis in a 28 year-old patient who presented with multiple papules and nodules distributed in dermatomal fashion on the trunk. The histopathological examination of the lesions revealed a non-encapsulated, well-circumscribed spindle cell neoplasm, which was consistent with neurofibromas.info:eu-repo/semantics/publishedVersio

Thorotrast Related Hepatic Malignancies. Two Case Reports

Os A.A apresentam dois casos clínicos de tumores hepáticos associados ao torotraste, dois colangiocarcinomas, observados numa enfermaria de Medicina Interna de um hospital de Lisboa. É feito um comentário sobre o efeito nefasto das radiações ionizantes em geral sobre o organismo humano, particularizando os efeitos do torotraste. Comenta-se, ainda, o prolongado tempo de latência que existiu nestes dois casos, bem como o facto de, provavelmente, estarmos perante os últimos casos de tumores induzidos pelo torotraste

Behçet's Disease. The Experience of an Internal Medicine Service

Os autores apresentam um estudo retrospectivo dos doentes com Doença de Behçet observados num Serviço de Medicina Interna entre 1982 e 2000. Foram analisados 33 doentes, sendo 20 do sexo masculino e 13 do sexo feminino. A primeira manifestação surgiu, em média, aos 24 anos e a média de idades, na altura do diagnóstico, foi de 32 anos. Todos os doentes apresentaram na sua evolução aftose oral recorrente, surgindo aftose genital em 84,8%, patologia ocular em 81,8%, articular em 75,7%, cutânea em 69,6%, alterações do sistema nervoso central em 27,3%, gerais em 24,2%, vasculares em 21,2%, gastrintestinais em 18,1%, neuropatia periférica em 12,1% e vasculite em 3% dos doentes observados

Hepatocellular carcinoma presenting with Budd-Chiari syndrome, right atrial thrombus and pulmonary emboli

A 47-year-old patient presented with a two-week history of right upper quadrant pain, abdominal distention and new onset of shortness of breath. He had a history of intravenous drug abuse, no alcohol consumption and denied any known liver disease. On physical examination, he was tachypneic and had dullness in the flanks. His blood analysis at admission was as follows: hemoglobin, 12.9 g/dL; leukocyte count, 6,800/uL; platelet count, 63,000/uL; INR, 2.1; serum creatinine, 1.27 mg/dL; liver biochemistry tests were notable for marginal derangement, HBsAg was negative, anti-HCV was positive, HCV RNA was 367,498 IU/ml and alpha-fetoprotein was 992 mg/dL. Abdominal ultrasound showed a right liver lobe mass (13 cm in diameter) with inferior vena cava (IVC) thrombosis and mild peri-hepatic ascites. A 2D echocardiogram showed a presumed right atrial tumor thrombus. A multiphasic contrast-enhanced abdominal tomography (CT) confirmed a hepatocellular carcinoma (HCC) with IVC obstruction and extensive tumoral thrombus to the right atrium (14 cm long).info:eu-repo/semantics/publishedVersio

Calibration of Airframe and Occupant Models for Two Full-Scale Rotorcraft Crash Tests

Two full-scale crash tests of an MD-500 helicopter were conducted in 2009 and 2010 at NASA Langley's Landing and Impact Research Facility in support of NASA s Subsonic Rotary Wing Crashworthiness Project. The first crash test was conducted to evaluate the performance of an externally mounted composite deployable energy absorber under combined impact conditions. In the second crash test, the energy absorber was removed to establish baseline loads that are regarded as severe but survivable. Accelerations and kinematic data collected from the crash tests were compared to a system integrated finite element model of the test article. Results from 19 accelerometers placed throughout the airframe were compared to finite element model responses. The model developed for the purposes of predicting acceleration responses from the first crash test was inadequate when evaluating more severe conditions seen in the second crash test. A newly developed model calibration approach that includes uncertainty estimation, parameter sensitivity, impact shape orthogonality, and numerical optimization was used to calibrate model results for the second full-scale crash test. This combination of heuristic and quantitative methods was used to identify modeling deficiencies, evaluate parameter importance, and propose required model changes. It is shown that the multi-dimensional calibration techniques presented here are particularly effective in identifying model adequacy. Acceleration results for the calibrated model were compared to test results and the original model results. There was a noticeable improvement in the pilot and co-pilot region, a slight improvement in the occupant model response, and an over-stiffening effect in the passenger region. This approach should be adopted early on, in combination with the building-block approaches that are customarily used, for model development and test planning guidance. Complete crash simulations with validated finite element models can be used to satisfy crash certification requirements, thereby reducing overall development costs