Диффузия водорода в палладии: рас-четы из первых принципов

Целью данной работы является теоретическое исследование профилей диффузионных барьеров и температурной зависимости коэффициентов диффузии водорода в палладии. По результатам расчетов наиболее вероятным механизмом диффузии атома Н в Pd являются диффузионные скачки через октаэдрические – тетраэдрические – октаэдрическе междоузлия (величина барьеров в этих случаях составляет ~ 0,39 и 0,16 эВ, соответственно). Для большинства диффузионных скачков, высота барьеров в твердом растворе Pd16H2 ниже, чем высота барьеров в твердом растворе Pd16H. При температурах 600-900 K, значения коэффициентов диффузии водорода вдоль направлений [110] и [001] решетки Pd хорошо согласуются с результатами других работ.The purpose of this study is theoretically study of the diffusion barrier profiles and the temperature dependence of the hydrogen diffusion coefficients in palladium. According to the results of our calculations, diffusion jumps through octahedral-tetrahedral-octahedral interstitial sites are the most probable mechanism of diffusion of the H atom in Pd (the barrier in these cases amounts to ~ 0.39 and 0.16 eV, respectively). For most diffusion jumps, the value of the barriers in a solid solution of Pd16H2 is lower than the value of the barriers in a solid solution of Pd16H. At temperatures of 600-900 K, the values of the hydrogen diffusion coefficients along the [110] and [001] directions of the Pd lattice agree well with the results of other studies

Modelling wind turbine degradation and maintenance

degradation, inspection and maintenance processes. The model was developed based on the Petri net method that effectively captures the stochastic nature of the dynamic processes through the use of appropriate statistical distributions. The versatility of the method allows the details of the degradation and maintenance operations to be incorporated in the model. In particular, there are dependent deterioration processes between wind turbine subsystems, complex maintenance rules and the incorporation of condition monitoring systems for early failure indication to enable replacement prior to failure. The purposes of the model are to predict the future condition of wind turbine components and to investigate the effect of a specified maintenance strategy. The model outputs are statistics indicating the performance of the wind turbine components; these include the probability of being in different condition states, the expected number of maintenance actions and the average number and duration of system downtime under any maintenance strategy

Morphologically and immunohistochemically undifferentiated gastric neoplasia in a patient with multiple metastatic malignant melanomas: a case report

Introduction: Malignant melanoma is a neoplasia which frequently involves the gastrointestinal tract (GIT). GIT metastases are difficult to diagnose because they often recur many years after treatment of the primary cutaneous lesion and also manifest clinically at an advanced stage of the neoplasia. Furthermore, GIT metastases can appear in various morphological forms, and therefore immunohistochemistry is often useful in distinguishing between a malignant melanoma and other malignancies. Case presentation: We report the case of a 60-year-old man with a multiple metastatic melanoma who underwent an upper endoscopy to clarify the possible involvement of the gastric wall with a mass localized in the upper abdomen involving the pancreas and various lymph nodes, which was previously described with computed tomography. Clinically, the patient reported a progressive loss of appetite, nausea and vomiting. The upper endoscopy and histological examination revealed a gastric location of an undifferentiated neoplasm with an absence of immunohistochemical characteristics referable to the skin malignant melanoma that was removed previously. Conclusion: The present case report shows the difficulty in diagnosing a metastatic melanoma in the GIT and therefore, it seems worthwhile to consider metastatic malignant melanoma in the differential diagnosis of undifferentiated neoplasia. © 2008 Alghisi et al; licensee BioMed Central Ltd

Imaging of Hereditary Hemorrhagic Telangiectasia

This pictorial review is based on our experience of the follow-up of 120 patients at our multidisciplinary center for hereditary hemorrhagic telangiectasia (HHT). Rendu-Osler-Weber disease or HHT is a multiorgan autosomal dominant disorder with high penetrance, characterized by epistaxis, mucocutaneous telangiectasis, and visceral arteriovenous malformations (AVMs). The research on gene mutations is fundamental and family screening by clinical examination, chest X-ray, research of pulmonary shunting, and abdominal color Doppler sonography is absolutely necessary. The angioarchitecture of pulmonary AVMs can be studied by unenhanced multidetector computed tomography; however, all other explorations of liver, digestive bowels, or brain require administration of contrast media. Magnetic resonance angiography is helpful for central nervous system screening, in particular for the spinal cord, but also for pulmonary, hepatic, and pelvic AVMs. Knowledge of the multiorgan involvement of HHT, mechanism of complications, and radiologic findings is fundamental for the correct management of these patients

Analysis of electrical power data for condition monitoring of a small wind turbine

This paper is a postprint of a paper submitted to and accepted for publication in IET Renewable Power Generation and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at IET Digital Library.Certain parts of a wind turbine, for example, the gearbox require significant time and heavy lifting equipment in the event of catastrophic failure necessitating replacement. Continuous condition monitoring has the potential to catch problems early, enable scheduled preventative maintenance and thereby reduce turbine downtime, reduce the number of site visits and prevent secondary damage. Accelerometers applied to mechanical components of the drive train are traditionally used for condition monitoring but require their own data acquisition system and analysis software. In contrast, the electrical current and voltage are continuously measured and could also be used for condition monitoring more cheaply. An experimental data acquisition system has been installed on a small (25kW) onshore turbine in Leicestershire, UK to compare three-phase currents and voltages on the stator windings with six accelerometer signals. Data have been recorded before and after a gearbox failure and replacement. Data were analysed using both Fourier Transform and Morlet Continuous Wavelet Transform methods. Results show that the stator voltages show the same radial and axial mode vibration frequencies as the accelerometers and could therefore be used for condition monitoring. Furthermore, the stator currents show torsional modes of vibration not picked up by the accelerometers