New approach to overcome key hurdle for next-generation superconductors

ScienceDaily (Oct. 27, 2011) — Researchers from North Carolina State University have developed a new computational approach to improve the utility of superconductive materials for specific design applications -- and have used the approach to solve a key research obstacle for the next-generation superconductor material yttrium barium copper oxide (YBCO).

A superconductor is a material that can carry electricity without any loss -- none of the energy is dissipated as heat, for example. Superconductive materials are currently used in medical MRI technology, and are expected to play a prominent role in emerging power technologies, such as energy storage or high-efficiency wind turbines.

One problem facing systems engineers who want to design technologies that use superconductive materials is that they are required to design products based on the properties of existing materials. But NC State researchers are proposing an approach that would allow product designers to interact directly with the industry that creates superconductive materials -- such as wires -- to create superconductors that more precisely match the needs of the finished product.

"We are introducing the idea that wire manufacturers work with systems engineers earlier in the process, utilizing computer models to create better materials more quickly," says Dr. Justin Schwartz, lead author of a paper on the process and Kobe Steel Distinguished Professor and head of NC State's Department of Materials Science and Engineering. "This approach moves us closer to the ideal of having materials engineering become part of the product design process."

To demonstrate the utility of the process, researchers tackled a problem facing next-generation YBCO superconductors. YBCO conductors are promising because they are very strong and have a high superconducting current density -- meaning they can handle a large amount of electricity. But there are obstacles to their widespread use.

One of these key obstacles is how to handle "quench." Quench is when a superconductor suddenly loses its superconductivity. Superconductors are used to store large amounts of electricity in a magnetic field -- but a quench unleashes all of that stored energy. If the energy isn't managed properly, it will destroy the system -- which can be extremely expensive. "Basically, the better a material is as a superconductor, the more electricity it can handle, so it has a higher energy density, and that makes quench protection more important, because the material may release more energy when quenched," Schwartz says.

To address the problem, researchers explored seven different variables to determine how best to design YBCO conductors in order to optimize performance and minimize quench risk. For example, does increasing the thickness of the YBCO increase or decrease quench risk? As it turns out, it actually decreases quench risk. A number of other variables come into play as well, but the new approach was effective in helping researchers identify meaningful ways of addressing quench risk.

"The insight we've gained into YBCO quench behavior, and our new process for designing better materials, will likely accelerate the use of YBCO in areas ranging from new power applications to medical technologies -- or even the next iteration of particle accelerators," Schwartz says.

"This process is of particular interest given the White House's Materials Genome Initiative," Schwartz says. "The focus of that initiative is to expedite the process that translates new discoveries in materials science into commercial products -- and I think our process is an important step in that direction."

The paper was co-authored by Dr. Wan Kan Chan, a research associate at NC State. The paper is available online from IEEE Transactions on Applied Superconductivity. The research was funded by the Air Force Research Laboratory.

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The above story is reprinted from materials provided by North Carolina State University.

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Journal Reference:

Wan Kan Chan, Justin Schwartz. Three-Dimensional Micrometer-Scale Modeling of Quenching in High-Aspect-Ratio YBa2Cu3O7-d Coated Conductor Tapes -- Part II: Influence of Geometric and Material Properties and Implications for Conductor Engineering and Magnet Design. IEEE Transactions on Applied Superconductivity, 2011; DOI: 10.1109/TASC.2011.2169670

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To diagnose heart disease, visualization experts recommend a simpler approach

ScienceDaily (Oct. 27, 2011) — A team of computer scientists, physicists, and physicians at Harvard has developed a simple yet powerful method of visualizing human arteries that may result in more accurate diagnoses of atherosclerosis and heart disease.

The prototype tool, called "HemoVis," creates a 2D diagram of arteries that performs better than the traditional 3D, rainbow-colored model. In a clinical setting, the tool has been shown to increase diagnostic accuracy from 39% to 91%.

Presented Oct. 27 at the IEEE Information Visualization Conference(InfoVis 2011), the new visualization methodoffers insight to clinicians, imaging specialists, engineers, and others in a wide range of fields who need to explore and evaluate complex, branching structures.

"Our goal was to design a visual representation of the data that was as accurate and efficient for patient diagnosis as possible," says lead author Michelle Borkin, a doctoral candidate at the Harvard School of Engineering and Applied Sciences (SEAS). "What we found is that the prettiest, most popular visualization is not always the most effective."

HemoVis takes data from patient-specific blood flow simulations, combined with traditional imaging data, and visually displays a tree diagram of the arteries with areas of disease highlighted to assist in diagnosis.

Tools for artery visualization in both clinical and research settings commonly use 3D models that portray the shape and spatial arrangement of vessels of interest. These complex tools require users to rotate the models to get a complete perspective of spatial orientation.

By contrast, the new visualization requires no such rotation or interaction. The tool utilizes 2D, circumference-adjusted cylindrical cross sections arranged in tree diagrams.

Though this visualization method may seem less high-tech, the team demonstrated through quantitative evaluation with medical experts that the 2D model is actually more accurate and efficient for patient diagnosis.

"In the 3D case, the more complex and branched the arteries were, the longer it took to complete the patient diagnosis, and the lower the accuracy was," Borkin reflects. "In the 2D representation, it didn't matter how many branches we had or how complex they were -- we got consistently fast, accurate results. We weren't expecting that."

Tree diagrams are hardly new, as evolutionary biologists will attest, but scientists in many fields are using them to solve a range of very modern and complex problems. In fact, Borkin applied her own experience in astronomy and physics to transform the concept of visualization for SEAS' Multiscale Hemodynamics research group. In prior work, she had used a very similar type of tree diagram to determine the structure of nebulae in outer space.

"With the consultation and cooperation of clinicians, we were able to draw on fairly well known visualization techniques and principles from computer science to solve a practical clinical problem," says Hanspeter Pfister, Gordon McKay Professor of the Practice of Computer Science at SEAS.

Borkin, Pfister, and their colleagues relied on the input of physicians and others with clinical or laboratory imaging experience throughout the process. Through extensive surveys and interviews, they identified the most popular options for display, accurate layout, and coloring of these arterial projections.

However, Borkin drew on well supported research that is less well known outside the visualization community:

"For years, visualization, computer science, and psychology researchers have identified that color is critical for conveying the value of data, but that the rainbow coloring is not well-attuned to the human visual system."

Accordingly, HemoVis departs from the traditional practice of rainbow color-coding in favor of a graded single-color scheme (red to black) that can represent placement along a continuum.

In tests, diagnostic accuracy, as measured by the proportion of diseased areas identified, increased dramatically with the new color scheme.

Widespread adoption of visual representations like those in HemoVis could have the effect of not only optimizing tasks that are critical for doctors, but also changing long-entrenched mindsets and making scientists "think twice" about their assumptions in data visualization, Borkin says.

"This approach to visualization design and validation is broadly applicable in medicine, engineering, and science," notes Pfister. "We hope that people will use this process as a template for transforming their own visualizations."

Borkin and Pfister acknowledged that while HemoVis represents an important step forward, traditional 3D artery models still play a role, particularly in providing a spatially intuitive tool for surgical planning.

With this in mind, the next steps for this research include further development and optimization of the 2D tool and investigation into how it might complement, rather than replace, its 3D counterpart.

A paper about this work will be published later this year in the journal IEEE Transactions on Visualization and Computer Graphics.

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The above story is reprinted from materials provided by Harvard University. The original article was written by Mureji Fatunde.

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Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

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