Polynomial-Time Fence Insertion for Structured Programs

To enhance performance, common processors feature relaxed memory models that reorder instructions. However, the correctness of concurrent programs is often dependent on the preservation of the program order of certain instructions. Thus, the instruction set architectures offer memory fences. Using fences is a subtle task with performance and correctness implications: using too few can compromise correctness and using too many can hinder performance. Thus, fence insertion algorithms that given the required program orders can automatically find the optimum fencing can enhance the ease of programming, reliability, and performance of concurrent programs. In this paper, we consider the class of programs with structured branch and loop statements and present a greedy and polynomial-time optimum fence insertion algorithm. The algorithm incrementally reduces fence insertion for a control-flow graph to fence insertion for a set of paths. In addition, we show that the minimum fence insertion problem with multiple types of fence instructions is NP-hard even for straight-line programs

The Cowl - v.1 - n.15 - Mar 27, 1936

The Cowl - student newspaper of Providence College. Volume 1, Number 15 - March 27, 1936. 6 pages. Note: Due to the way these issues were bound into volumes, some of the letters on extreme left- and right-hand columns are slightly truncated

Mechanical strength and tribological behavior of ion-beam deposited boron nitride films on non-metallic substrates

An investigation was conducted to examine the mechanical strength and tribological properties of boron nitride (BN) films ion-beam deposited on silicon (Si), fused silica (SiO2), gallium arsenide (GaAs), and indium phosphide (InP) substrates in sliding contact with a diamond pin under a load. The results of the investigation indicate that BN films on nonmetallic substrates, like metal films on metallic substrates, deform elastically and plastically in the interfacial region when in contact with a diamond pin. However, unlike metal films and substrates, BN films on nonmetallic substrates can fracture when they are critically loaded. Not only does the yield pressure (hardness) of Si and SiO2 substrates increase by a factor of 2 in the presence of a BN film, but the critical load needed to fracture increases as well. The presence of films on the brittle substrates can arrest crack formation. The BN film reduces adhesion and friction in the sliding contact. BN adheres to Si and SiO2 and forms a good quality film, while it adheres poorly to GaAs and InP. The interfacial adhesive strengths were 1 GPa for a BN film on Si and appreciably higher than 1 GPa for a BN film on SiO2

Effects of fabrication and joining processes on compressive strength of boron/aluminum and borsic/aluminum structural panels

Processes for forming and joining boron/aluminum and borsic/aluminum to themselves and to titanium alloys were studied. Composite skin and titanium skin panels were joined to composite stringers by high strength bolts, by spotwelding, by diffusion bonding, by adhesive bonding, or by brazing. The effects of the fabrication and joining processes on panel compressive strengths were discussed. Predicted buckling loads were compared with experimental data

Diamond Sheet: A new diamond tool material

Diamond sheet is termed a diamond tool material because it is not a cutting tool, but rather a new material from which a variety of different tools may be fabricated. In appearance and properties, it resembles a sheet of copper alloy with diamond abrasive dispersed throughout it. It is capable of being cut, formed, and joined by conventional methods, and subsequently used for cutting as a metal bonded diamond tool. Diamond sheet is normally made with industrial diamond as the abrasive material. The metal matrix in diamond sheet is a medium hard copper alloy which has performed well in most applications. This alloy has the capability of being made harder or softer if specific cutting conditions require it. Other alloys have also been used including a precipitation hardened aluminum alloy with very free cutting characteristics. The material is suitable for use in a variety of cutting, surfacing, and ring type tools, as well as in such mundane items as files and sandpaper. It can also be used as a bearing surface (diamond to diamond) and in wear resistant surfaces

Studies in prestressed and segmented brittle structures

Application of nonlinear bending theory to prestressed and segmented brittle structure

Protocolo para la evaluación del estado ecológico de la red fluvial de Aragón (NE de España) según sus comunidades de macroinvertebrados bentónicos

Rivers play a fundamental role in the biosphere, and to attain a sustainable development it is necessary to evaluate their ecological status, to know how and which human activities affect them, the Water Framework Directive (2000/60/CE) establishes the basic principles for a sustainable water use policy in the EU. With the aim of evaluate the ecological status of the fluvial network of Aragón for the Aragon Government, a protocol for sample taking and analysis was designed to cover two objectives. It had to produce enough precise results and also, it had to allow for space-time comparisons, in accordance with the Directive and international standardization rules. It is based on sampling with Surber net in laminar and turbulent flow, IBMWP index applications, evaluation of the differences in abundance of macroinvertebrates, evaluation of the presence of alien species, assignation of ecological state categories, and cartographic representation. Through this protocol, the ecological status of 140 reaches of the Aragon fluvial network was determined. Abundance corrections were not necessary and only one correction was due to the presence of alien species.Los ríos desempeñan un papel fundamental en la biosfera y para conseguir un desarrollo sostenible es necesario valorar su estado ecológico, comprobando qué actuaciones humanas les afectan y cómo; la Directiva Marco de Aguas (2000/60/CE) establece los principios básicos para una políıtica hídrica sostenible en la UE. Con el objeto de valorar el estado ecológico de la red fluvial aragonesa para el Gobierno de Aragón, se diseñó un protocolo de toma y análisis de muestras que cubriera dos objetivos. Debía producir unos resultados suficientemente precisos y, además, debía permitir las comparaciones espaciotemporales, siguiendo tanto la Directiva como las normas internacionales de estandarización. Está basado en el muestreo con red Surber tanto en flujo laminar como turbulento, aplicación del índice IBMWP, evaluación de las diferencias en la abundancia de macroinvertebrados, valoración de la presencia de especies alóctonas, asignación de categorías de estado ecológico y representación cartográfica. Mediante este protocolo se determinó el estado ecológico de 140 tramos de la red fluvial aragonesa, no siendo necesarias correcciones por abundancia y sólo una corrección por la presencia de especies alóctonas

Amelioratory Effect of Nanoconjugated Vancomycin on Spleen during VRSA-Induced Oxidative Stress

Objective. The aim of the present study was to evaluate the possible antioxidant effects of nanoconjugated vancomycin against VRSA infection on select makers of oxidative damage and antioxidant status in spleen. Methods. A coagulase-positive VRSA strain was used for this study. VRSA infection was developed in Swiss mice by intraperitoneal injection of 5 × 106 CFU/mL bacterial solutions. VRSA-infected mice were treated with nanoconjugated vancomycin at its effective dose for 10 days. After decapitation, blood was used for determination of viable bacteria count and spleen was excised from control and experimental groups, homogenized and used for different biochemical estimations. Results. Nitrate level, myeloperoxidase activity, lipid peroxidation, protein oxidation, oxidized glutathione, and DNA fragmentation level were increased significantly (P < 0.05) in spleen of VRSA-infected group as compared to control group, and reduced glutathione level, activity of SOD, CAT, GPx, GR, and GST were decreased significantly (P < 0.05); which were increased or decreased significantly (P < 0.05) near to normal in nanoconjugated vancomycin-treated group. Conclusion. These findings suggest the potential use and beneficial role of nanoconjugated vancomycin against VRSA-infection-induced oxidative stress and DNA damage in spleen

Development of deployable structures for large space platform systems, part 1

Eight deployable platform design objectives were established: autodeploy/retract; fully integrated utilities; configuration variability; versatile payload and subsystem interfaces; structural and packing efficiency; 1986 technology readiness; minimum EVA/RMS; and Shuttle operational compatibility