| NEWS & IDEAS |
September 1998
POWER ELECTRONICS:
Goal--30% Savings in Power Use
CHEMICAL ENGINEERING:
ACS Meeting--Enzyme Catalysts
CHEMICAL ENGINEERING:
ACS Meeting--Membrane Cleaning Vortices
CHEMICAL ENGINEERING:
ACS Meeting--A New Use for Displacers
MANAGEMENT & TECHNOLOGY:
Consensus Needed on Strategy
BIOMEDICAL ENGINEERING:
Robotic Hip Surgery Could Cut Pain
POWER ELECTRONICS:
Goal--30% Savings in Power Use
Improved power electronics devices can save 30 percent in electric power consumption in the United States in the next 10 years, according to T. Paul Chow. One key is replacing silicon with silicon carbide in high-voltage power devices, and Chow expects to see the first commercial silicon carbide device hit the market by the year 2000.
Rensselaer is one of five university partners in a new Engineering Research Center (ERC) in Power Electronics funded by the National Science Foundation to make the United States the most efficient user of electrical energy in the world. The consortium will improve and standardize the electronic components that now manage more than 60 percent of the total electric power used in the United States.
Chow, campus director of the program at Rensselaer, is an expert on power electronics, whose research in the last five years has concentrated on high-voltage devices built from such "wide band gap" materials as silicon carbide.
He has studied a variety of materials classified as wide band gap because of their electrical properties and has concluded that silicon carbide has advantages that could improve performance of high-voltage power-switching devices by at least a factor of 10. Silicon carbide conducts heat better than silicon, less thickness of the material is required to support the same voltage, and there is less leakage at high temperatures. Unlike other wide band gap materials, moreover, it is possible to grow a thermal oxide on silicon carbide, a necessary step in the manufacture of power devices.
Using silicon carbide would let motors and other equipment perform efficiently at much higher temperatures (400 C instead of 200 C), requiring less cooling and wasting less energy.
But switching to silicon carbide requires more than replacing one material with the other. Researchers must develop practical ways to design and build devices that best exploit the properties of the new material.
At Rensselaer, Ishwara Bhat, also an ERC participant, concentrates on the growth and processing of silicon carbide on substrates of silicon, sapphire, or silicon carbide. Ronald Gutmann, another ERC participant, and Chow are collaborating to design, simulate, fabricate, and test silicon carbide high-voltage, high-frequency devices. And David Torrey will use silicon carbide components to build power electronics circuits and systems.
Contact: Paul Chow (518) 276-2910, chow@unix.cie.rpi.edu
CHEMICAL ENGINEERING:
ACS Meeting--Enzyme Catalysts
Enzymes are proteins that come from living systems, but they can function in remarkably harsh environments, according to Jonathan S. Dordick, the new Howard P. Isermann Professor and chair of chemical engineering at Rensselaer.
While enzymes already are used widely as catalysts in the food and pharmaceutical industries, Dordick is finding ways to extend their use to many other industrial settings. He described some of his techniques during the annual meeting of the American Chemical Society in August in Boston.
Enzymes are used as catalysts in processes that produce such products as high-fructose corn syrups or antibiotics. While these natural proteins are intended by nature to work in water, they can be made to function quite effectively in harsh organic solvents, Dordick says. Used in this way, they can often outperform chemical catalysts in the chemical or polymer industries, efficiently creating new, highly selective materials.
In their research, Dordick's team has used protein engineering to change some of the amino acids in natural enzymes, making them perform more efficiently.
They also have effectively modified the environment around the enzyme. In one of their simpler approaches, they teamed up with Douglas Clark, professor of chemical engineering at the University of California at Berkeley, to dissolve enzymes in water and then freeze-dry them in the presence of salts. This created a matrix around the enzymes, producing catalytic activity that is 1,000 times more effective that than achieved with untreated enzymes, Dordick reports.
Contact: Jonathan Dordick (518) 276-6379, dordick@rpi.edu
CHEMICAL ENGINEERING:
ACS Meeting--Membrane Cleaning Vortices
Vortices - tiny whirlpools that have fascinated scientists since Leonardo DaVinci - can reduce membrane fouling problems for the biotechnical industry, speeding production and cutting drug prices, according to Georges Belfort, professor of chemical engineering.
Belfort and his students have developed a system that forces the liquid solutions containing the desired biological products through a series of curves, creating tiny counter-rotating vortices that scrub the foulants from the membrane. He presented a paper describing the patented process at the annual meeting of the American Chemical Society. Co-authors are doctoral student Gunther Gehlert and post-doc Susana Luque.
The biotechnology industry uses pressure-driven membrane processes to concentrate proteins and other biological products. These processes are all plagued by the buildup of dissolved and suspended substances on the membranes. Many approaches have been tried to keep the membrane clean, but the design developed by Belfort's team is the first to create effective vortices without using moving parts.
They first designed a microfilter to remove large particles such as cells from a biological solution. They have now designed an ultrafiltration module that removes protein-size molecules. In this design, the liquids are forced through hollow fiber membranes arranged in a helical configuration rather than the linear one now used in industry. This ultrafiltration design extends the usefulness of Belfort's approach to many more biotechnological separations as well as to such important biomedical applications as kidney dialysis and blood filtration.
Contact: Georges Belfort (518) 276-6948, belfog@rpi.edu
CHEMICAL ENGINEERING:
ACS Meeting--A New Use for Displacers
Rensselaer researchers have developed an improvement to a form of chromatography that is widely used in the drug industry.
This new use of "displacers," described during the annual meeting of the American Chemical Society in Boston, is expected to make hydrophobic interaction chromatography, a key process in the production of a wide range of proteins, more efficient and cost-effective, according to Steven Cramer, Rensselaer professor of chemical engineering.
Medically valuable proteins are often present in very small amounts in extremely complex mixtures. Separating and purifying them can represent a significant portion of a drug's costs. Cramer is a leader in the development of displacement chromatography, a process in which a compound called a displacer is pumped into the chromatography column after the introduction of the feed mixture. The displacer forces the mixture through the column, causing the separated substances to emerge in concentrated, pure blocks.
His earlier work, particularly with low-molecular weight compounds used as displacers in ion exchange chromatography, has made displacement chromatography far more practical for the biotechnology industry.
Now, Cramer's group has extended the use of displacers to hydrophobic interaction chromatography, another widely used separation process.
Contact: Steven Cramer (518) 276-6198, crames@rpi.edu
MANAGEMENT & TECHNOLOGY:
Consensus Needed on Strategy
A company's operations strategy must be clear to every employee or that strategy will be weakened by thousands of decisions employees make every day, says Chris McDermott, assistant professor at Rensselaer's Lally School of Management and Technology.
"If the competitive priority is low cost, everyone should be clear on that. If, on the other hand, the strategy is flexibility, that must be clear to every employee," said McDermott, who studied communication in the metalworking industry with Ken Boyer, assistant professor at DePaul University.
The researchers found a substantial lack of consensus on corporate strategy during separate interviews with managers and the people who operated the machines on the factory floor. Both groups were asked to rank the importance the company placed on cost, quality, delivery, and flexibility. In a few companies the operators and managers chose the same priority. In most, however, the operators and managers disagreed on what was most important to the company.
The critical factor that determines the success of a strategy is not necessarily which competitive priority is stressed (delivery, cost, quality, or flexibility), but how well the priority is translated into a consistent set of decisions that support corporate strategy, McDermott said.
"There needs to be strategic consensus. The strategy may be absolutely right, but members of the firm all need to be pulling in the same direction for that strategy to work," said McDermott.
The research has been accepted for publication in the Journal of Operations Management.
Contact: Chris McDermott, Lally School of Management and Technology (518) 276-4861 or mcderc@rpi.edu
BIOMEDICAL ENGINEERING:
Robotic Hip Surgery Could Cut Pain
Patients undergoing gall bladder surgery or appendectomies once required weeks of recovery time. Now, thanks to minimally invasive surgery, most are back to work in days.
A coalition from Rensselaer and Albany Medical Center (AMC) is using robots and groundbreaking computing techniques to extend similar savings in pain, recovery time, and expense to patients facing orthopedic surgery. The coalition includes RensselaerŐs Scientific Computation Research Center and its Center for Automation Technology, as well as Albany Medical CenterŐs new Minimally Invasive Surgery Center for Training and Education and its Orthopedic Surgery Department. As a first challenge, this team has focused on hip replacement.
Surgeons now make two incisions Ń each 20 to 30 centimeters long. One allows them to ream out the acetabulum, the cup-shaped socket of the hipbone, and cement in a steel cup. The other gives them room to drill a hole in the femur and insert a shaft with a ball on the end. The ball will ride in the steel cup, creating a new hip joint.
In a minimally invasive version, a surgeon will need incisions of only 3 to 4 centimeters, just enough space to squeeze in implants and robotic devices. Miniature power saws and reamers will pulverize bone and an irrigation system will carry it away. Tiny robots will also insert cement exactly where desired.
The robotic tools will perform each move precisely because the surgeon will have planned every detail on 3D computer models of the injured joint. During surgery, the 3D model will provide a screen image that gives the surgeon almost as clear a view as what is seen in open surgery and will enable the doctor to guide the robotic instruments inside the patient.
Already, the team has created a patient-specific computer model of a human hip suitable for analyzing stresses within the joint. A prototype robotic system is being built to demonstrate the robotic technologies needed.
Contacts: Robert Spilker, chair, biomedical engineering, (518) 276-2154, spilker@rpi.edu; Harry Stephanou, director, Center for Automation Technology, (518) 276-6156, hes@cat.rpi.edu
