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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

High-resolution wave-theory-based ultrasound reflection imaging using the split-step fourier and globally optimized fourier finite-difference methods

Methods for enhancing ultrasonic reflection imaging are taught utilizing a split-step Fourier propagator in which the reconstruction is based on recursive inward continuation of ultrasonic wavefields in the frequency-space and frequency-wave number domains. The inward continuation within each extrapolation interval consists of two steps. In the first step, a phase-shift term is applied to the data in the frequency-wave number domain for propagation in a reference medium. The second step consists of applying another phase-shift term to data in the frequency-space domain to approximately compensate for ultrasonic scattering effects of heterogeneities within the tissue being imaged (e.g., breast tissue). Results from various data input to the method indicate significant improvements are provided in both image quality and resolution.

47 OTHER INSTRUMENTATION↗
DOE OSTI2017

Automated Detection of Alkali-silica Reaction in Concrete using Linear Array Ultrasound Data

Alkali-silica reaction (ASR) is a chemical reaction in either concrete or mortar between hydroxyl ions of the alkalis (sodium and potassium) from hydraulic cement (or other sources), and certain siliceous minerals present in some aggregates. The reaction product, an alkali-silica gel, is hygroscopic having a tendency to absorb water and swell, which under certain circumstances, leads to abnormal expansion and cracking of the concrete. This phenomenon affects the durability and performance of concrete structures severely since it can cause significant loss of mechanical properties. Developing reliable methods and tools that can evaluate the degree of the ASR damage in existing structures, so that informed decisions can be made toward mitigating ASR progression and damage, is important to the long term operation of nuclear power plants especially if licenses are extended beyond 60 years. This paper examines an automated method of determining the extent of ASR damage in fabricated concrete specimens.

Santos-Villalobos, Hector J↗
DOE OSTI2017

Ultrasound assisted in-situ formation of carbon/sulfur cathodes

A process of preparing an E-carbon nanocomposite includes contacting a porous carbon substrate with an E-containing material to form a mixture; and sonicating the mixture to form the E-carbon nanocomposite; where E is S, Se, Se.sub.xS.sub.y, or Te, x is greater than 0; and y is greater than 0.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Detecting alkali-silica reaction in thick concrete structures using linear array ultrasound

The use of concrete structures in commercial nuclear power plants (NPPs) has made its long-term performance crucial for safe operation, especially with license period extensions to sixty years and possibly beyond. Alkali-Silica Reaction (ASR) is a reaction that occurs over time in concrete between alkaline cement paste and reactive, non-crystalline silica (aggregates). In the presence of water, an expansive gel is formed within the aggregates, which results in micro cracks in aggregates and adjacent cement paste. ASR can potentially affect concrete properties and performance characteristics such as compressive strength, modulus of elasticity, flexural stiffness, shear strength, and tensile strength. Currently, no NDE methods have proven effective in identifying ASR before surface cracks form. ASR is usually identified either visibly or by petrographic analysis. While ASR definitely impacts concrete material properties, the performance of concrete structures exhibiting ASR is dependent upon whether or not the concrete is unconfined or confined with reinforcing bars. Confinement by reinforcing bars acts to restrain the expansion of ASR affected concrete similar to pre-stressing, thus improving the performance of a structure. Additionally, there is no direct correlation between the mechanical properties of concrete sample cores and the in-situ properties of the concrete when inside a structure. The University of Tennessee (UTK), along with Oak Ridge National Laboratory and a consortium of universities have developed an accelerated ASR experiment. Three large concrete specimens, representative of NPP infrastructure, were constructed with both embedded and surface instruments. This paper presents preliminary analysis using frequency banded synthetic aperture focusing technique (SAFT).

Ezell, N Dianne↗
DOE OSTI2019

Direct formation of gold nanoparticles using ultrasound

The invention provides a green chemistry, aqueous method to synthesize gold nanoparticles directly from bulk gold sources. The method involves the ultrasonication of bulk gold in water in the presence of an alkythiol species and a quaternary ammonium surfactant. An organic bilayer forms on the surface of the gold which renders it susceptible to material ejection from the violent collapse of cavitation bubbles. This ejected material is stabilized in solution by the formation of an organic bilayer and can be easily separated. It can then be subjected to an aqueous digestive ripening step to give a gold nanoparticle ensemble with a well-defined plasmon resonance. This method is applicable to a number of different sources of bulk gold. The method can be applied to an environmentally important problem; the recovery of gold from electronic waste streams. For example, gold nanoparticles can be extracted directly from the surface of SIM cards, with no prior manipulation of the cards necessary.

Huber, Dale L.↗