High Speed Bearing Wear Rate Measurements for Spacecraft Active Thermal Control Fluid Pumps with a Novel Pin on Disk Apparatus

A novel pin on disc tribometer was designed and constructed to generate a high-speed, wear coefficient database for hydrodynamic bearings that are typically used in canned motors found in the active thermal control circuits of robotic and inhabited spacecraft. The primary motivation for this work was the premature failure of the active external thermal control pump on the International Space Station in 2010. During the failure investigation of this incident, the root cause was postulated to be high speed wear of the bearings. Although a detailed forensic analysis gave credibility to this theory, the lack of wear coefficient data at relevant conditions prevented validation of this finding. The database generated from the new Extreme Environment Tribometer (EET) enabled a closure calculation within 5% of the observed wear from inspections of the failed hardware. Testing in anhydrous ammonia and surrogate fluid was performed to provide a means for simplified testing in the future and to populate a preliminary database for the design of future active thermal control systems on spacecraft. The EET and test techniques developed for the measurement of high-speed wear coefficients are available to future system designers

The Relevance of Academic Libraries in the Twenty-First Century

The biggest challenge facing the library profession in the twenty-first century is staying relevant to its users. It is often stated that the Internet and Google have changed librarianship. This challenge, while significant, does not mean that libraries will go away. It is causing us to re-evaluate what we do, how we do it, and what role libraries have in the academy and in our culture at large. This column addresses some of the ways in which academic libraries can stay relevant throughout the twenty-first century

Compact model of latent heat thermal storage for its integration in multi-energy systems

Nowadays, flexibility through energy storage constitutes a key feature for the optimal management of energy systems. Concerning thermal energy, Latent Heat Thermal Storage (LHTS) units are characterized by a significantly higher energy density with respect to sensible storage systems. For this reason, they represent an interesting solution where limited space is available. Nevertheless, their market development is limited by engineering issues and, most importantly, by scarce knowledge about LHTS integration in existing energy systems. This study presents a new modeling approach to quickly characterize the dynamic behavior of an LHTS unit. The thermal power released or absorbed by a LHTS module is expressed only as a function of the current and the initial state of charge. The proposed model allows simulating even partial charge and discharge processes. Results are fairly accurate when compared to a 2D finite volume model, although the computational effort is considerably lower. Summarizing, the proposed model could be used to investigate optimal LHTS control strategies at the system level. In this paper, two relevant case studies are presented: (a) the reduction of the morning thermal power peak in District Heating systems; and (b) the optimal energy supply schedule in multi-energy systems

Comparación de la precisión diagnóstica de la tomografía computarizada de haz cónico y tres sistemas radiográficos intraorales en la detección de lesiones de caries in vitro.

Objective: The objective of the study was to compare the diagnostic accuracy of cone beam computed tomography and three intraoral radiographic systems in the detection of in vitro caries lesions. Material and Methods: One hundred teeth (46 molars and 54 premolars) were evaluated, including 176 proximal surfaces and 90 occlusal surfaces, with or without dental caries lesions. Digital images of all teeth were obtained using specific intraoral radiographs, VistaScan DürrDental®phosphor-plate radiography, XIOS XG Sirona® digital sensor radiography, and CBCT I-CATTM. Observers evaluated the images for the detection of caries lesions. The teeth were clinically sectioned and stereomicroscopy served as a validation tool. The relationship of sensitivity and specificity between all systems was determined through the ROC curve using Az values. Results: The values of the area under the curve (Az) selected for the CBCT I-CATTM system were 0.89 (0.84-0.93), for conventional radiography 0.71 (0.66-0.76), digital sensor radiography 0.74 (0.70-0.78) and digital radiography with phosphor-plates 0.73 (0.69-0.77). Statistically significant differences were found between the CBCT I-CATTM system and intraoral radiographic systems (p<0.01). The sensitivity and specificity values for the CBCT I-CATTM were 0.84 and 0.93 respectively. Conclusion: CBCT has a high sensitivity and specificity compared to intraoral radiographic systems for the diagnosis of dental caries lesions in vitro.Objetivo: El objetivo del estudio fue comparar la precisión diagnóstica de la tomografía computarizada de haz cónico y tres sistemas radiográficos intraorales en la detección de lesiones de caries in vitro. Material y Métodos: Se evaluaron 100 dientes, 46 molares y 54 premolares; 176 superficies proximales y 90 superficies oclusales, con o sin lesión de caries dental. Se obtuvieron imágenes digitales de todos los dientes utilizando radiografías intraorales convencionales, radiografía con placas de fósforo VistaScan Du?rrDental®, radiografía con sensor digital XIOS XG Sirona® y CBCT I-CATTM. Tres observadores evaluaron las imágenes para la detección de lesiones de caries. Los dientes se seccionaron clínicamente y la estereomicroscopía sirvió como herramienta de validación. Se determinó relación de sensibilidad y especificidad entre todos los sistemas a través de la curva ROC utilizando valores Az. Resultados: Los valores de área debajo de la curva (Az) obtenidos para el sistema CBCT I-CATTM fueron de 0.89 (0.84-0.93), para radiografía convencional 0.71 (0.66-0.76), radiografía con sensor digital 0.74 (0.70-0.78) y radiografía digital con placas de fósforo 0.73 (0.69-0.77). Se encontró diferencias estadísticamente significativas entre el sistema CBCT I-CATTM y todos los sistemas radiográficos convencionales y digitales (p<0.01). Los valores de sensibilidad y especificidad para el CBCT I-CATTM fueron 0.84 y 0.93 respectivamente. Conclusión: La CBCT tiene una alta sensibilidad y especificidad en comparación a los sistemas radiográficos intraorales en el diagnóstico de lesiones de caries dental in vitro

A semi-automatic methodology for tire’s wear evaluation

In this work, the authors aim at developing a reliable and fast methodology to evaluate the wear evolution in tire starting from a complete optical 3D scanning. Starting from a data cloud, a semi-automatic methodology was implemented in MATLAB to extract mean tread radial profiles in correspondence of the desired angular position of the tire. These profiles could be numerically evaluated to establish the presence of irregular wear and the characteristic parameter of the groove depth. The reliability and the robustness of this methodology was firstly tested by applying it to several synthetic case studies modeled in CATIA V5®, where ovalization and presence of defects were also simulated. The groove depth was determined with an error lower than 1% for the ideal model, while the introduction of ovalization and defects leaded to an error of 2.6% in the worst condition. In a second time, the methodology has been successfully applied to experimental measurements carried out in two different wear life of the tire, allowing the tracking of the wear phenomena through the evaluation of the progressive lowering of tread radial profiles