Thermal and mechanical properties of polycrystalline U3Si2 synthesized by spark plasma sintering

U₃Si₂ has been explored as an alternative nuclear fuel material for increased accident tolerance. However, scatter has been reported in the thermal properties possibly because of the pores and impurities within the samples. In the present study, we prepared a polycrystalline U₃Si₂ bulk sample with high density and without impurity, and evaluated its thermal and mechanical properties. The sample was synthesized by arc melting and spark plasma sintering, followed by annealing. The density of the U₃Si₂ pellet was 96% of the theoretical density. The heat capacity was measured and compared with the calculation data. In addition, the measured data were used to evaluate thermal conductivity of U₃Si₂. The measurement data of elastic properties were compared with the theoretical calculation and agreed well. A high thermal conductivity and hardness compare to UO₂make it favorable to anticipated as alternative nuclear fuel.     

High Strength Low Alloy (HSLA) Steels in Building Construction

Majority of the buildings,including industrial buildings,are constructed using either structural steel (plates and structural shapes) or deformed bar steel reinforced concrete.Such buildings,however,must be designed to be safe and serviceable during construction and during use and occupancy.These objectives can be easily achieved by the use of steels having superior mechanical properties,ductility,weldability,fire resistance,etc.Over the years,the steel industry has made improvements in steel making technologies resulting in high strength low alloy (HSLA) steels with superior steel properties well suited for building construction.First part of this paper presents the structural design considerations,and the constructional considerations associated with the building structures in general,and steel structures in particular.This second part of the paper looks at the acceptance criteria for HSLA steels for North American building codes and construction.The third part of the paper presents the structural properties of currently available HSLA steels for building construction.The discussion focuses on hot-rolled structural steel shapes as well as deformed steel bars for concrete reinforcement.The paper argues that Niobium microalloying is the key to achieving superior properties in such steels.     

Production of olefins from ethanol by Fe and/or P‐modified H‐ZSM‐5 zeolite catalysts

BACKGROUND: Much attention has been paid to the catalytic conversion of ethanol to olefins, since biomass resources such as ethanol are carbon‐neutral and renewable, and olefins are useful as both fuels and chemicals. It has been reported that zeolite H‐ZSM‐5 is effective for converting ethanol to hydrocarbons, with the chief products being aromatic compounds. RESULTS: Successive addition of Fe and P to the H‐ZSM‐5 improved the initial selectivity for propylene, while the sole addition of Fe or P and co‐addition of Fe and P showed medium initial selectivity. In general, catalysts showing higher initial selectivity for propylene exhibited a steeper decrease in propylene selectivity with time on‐stream. The cause of the change in product selectivity may be carbon deposition during reaction. Addition of Fe and P can improve catalytic stability when processing both neat and aqueous ethanol. The catalytic performance was regenerated by calcination in flowing air. CONCLUSION: Fe‐ and/or P‐modified H‐ZSM‐5 zeolite catalysts efficiently produced olefins (especially propylene) from ethanol. Effective catalyst regeneration was achieved by calcination in flowing air. Copyright © 2010 Society of Chemical Industry     

Mitigating Malicious Code

ABSTRACT

Mitigation of malicious code is increasingly complicated by multi-staged and mutli-variant attacks taking place daily on the Internet today. It is now common for computers to be infected for long periods of time, with malicious browser help objects, rootkits, and similar stealth codes. Identification and removal from a computer can be especially difficult. In some cases, the only reasonable effort may be to completely wipe and reinstall an image of the system, known to be free of malicious code. Manual mitigation of malicious code is a sophisticated process of threat identification, research, mitigation, and monitoring to properly remove all threat components related to an attack.     

Big Board: Teleconferencing Over Maps for Shared Situational Awareness

Collaborative technologies for information sharing are an invaluable resource for emergency managers to respond to and manage highly dynamic events such as natural disasters and other emergencies. However, many standard collaboration tools can be limited either because they provide passive presentation and dissemination of information, or because they are targeted towards highly specific usage scenarios that require considerable training to use the tools. We present a real-time gather and share system called “Big Board” which facilitates collaboration over maps. The Big Board is an open-source, web based, real time visual collaborative environment that runs on all modern web browsers and uses open-source web standards developed by the Open Geospatial Consortium (OGC) and WorldWideWeb Consortium (W3C). An evaluation of Big Board was conducted by school representatives in North Carolina for use in situational understanding for school closure decisions during winter weather events. The decision to close schools has major societal impacts and is one that is usually made based on how well a teenage driver could handle wintry precipitation on a road. Collecting information on the conditions of roads is especially critical, however gathering and sharing of this information within a county can be difficult. Participants in the study found the Big Board intuitive and useful for sharing real time information, such as road conditions and temperatures, leading up to and during a winter storm scenario. We have adapted the Big Board to manage risks and hazards during other types of emergencies such as tropical storm conditions.