Posts tagged data
Mining big data for performance clues as a study guide
Jan 21st
forgetting with personalized content review
Computer software similar to that used by online retailers to recommend products to a shopper can help students remember the content they’ve studied, according to a new study by the University of Colorado Boulder.
The software, created by computer scientists at CU-Boulder’s Institute for Cognitive Science, works by tapping a database of past student performance to suggest what material an individual student most needs to review.
For example, the software might know that a student who forgot one particular concept but remembered another three weeks after initially learning them is likely to need to review a third concept six weeks after it was taught. When a student who fits that profile uses the software, the computer can pull up the most useful review questions.
“If you have two students with similar study histories for specific material, and one student couldn’t recall the answer, it’s a reasonable predictor that the other student won’t be able to either, especially when you take into consideration the different abilities of the two students,” said CU-Boulder Professor Michael Mozer, senior author of the study published in the journal Psychological Science.
The process of combing “big data” for performance clues is similar to strategies used by e-commerce sites, Mozer said.
“They know what you browsed and didn’t buy and what you browsed and bought,” Mozer said. “They measure your similarity to other people and use purchases of similar people to predict what you might want to buy. If you substitute ‘buying’ with ‘recalling,’ it’s the same thing.”
The program is rooted in theories that psychologists have developed about the nature of forgetting. Researchers know that knowledge—whether of facts, concepts or skills—slips away without review, and that spacing the review out over time is crucial to obtaining robust and durable memories.
Still, it’s uncommon for students to do the kind of extended review that favors long-term retention. Students typically review material that was presented only in the most recent unit or chapter—often in preparation for a quiz—without reviewing previous units or chapters at the same time.
This leads to rapid forgetting, even for the most motivated learners, Mozer said. For example, a recent study found that medical students forget roughly 25 to 35 percent of basic science knowledge after one year and more than 50 percent by the next year.
Over the last decade, Mozer has worked with University of California, San Diego, psychologist Harold Pashler, also a co-author of the new study, to create a computer model that could predict how spaced review affects memory. The new computer program described in the study is an effort to make practical use of that model.
Robert Lindsey, a CU-Boulder doctoral student collaborating with Mozer, built the personalized review program and then tested it in a middle school Spanish class.
For the study, Lindsey and Mozer divided the material students were learning into three groups. For material in a “massed” group, the students were drilled only on the current chapter. For material in a “generic-spaced” group, the students were drilled on the most recent two chapters. For material in a “personalized-spaced” group, the algorithm determined what material from the entire semester each student would benefit most from reviewing.
In a cumulative test taken a month after the semester’s end, personalized-spaced review boosted remembering by 16.5 percent over massed study and by 10 percent over generic-spaced review.
In a follow-up experiment, Mozer and his colleagues compared their personalized review program to a program that randomly quizzes students on all units that have been covered so far. Preliminary results show that the personalized program also outperforms random reviews of all past material.
So far, the program has been tested only in foreign language classes, but Mozer believes the program could be helpful for improving retention in a wide range of disciplines, including math skills.
It’s not necessary to have a prior database of student behavior to implement the personalized review program. Students can begin by using the program as a traditional review tool that asks random questions, and as students answer, the computer begins to search for patterns in the answers. “It doesn’t take long to get lots and lots of data,” Mozer said.
The research was funded by the National Science Foundation and the McDonnell Foundation.
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CU: Gas-fired plants help clean the air
Jan 10th
Power plants that use natural gas and a new technology to squeeze more energy from the fuel release far less of the greenhouse gas carbon dioxide than coal-fired power plants do, according to a new analysis accepted for publication Jan. 8 in Earth’s Future, a journal of the American Geophysical Union. The so-called “combined cycle” natural gas power plants also release significantly less nitrogen oxides and sulfur dioxide, which can worsen air quality.
“Since more and more of our electricity is coming from these cleaner power plants, emissions from the power sector are lower by 20, 30 even 40 percent for some gases since 1997,” said lead author Joost de Gouw, an atmospheric scientist with NOAA’s Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder. NOAA is the National Oceanic and Atmospheric Administration.
De Gouw, who works at NOAA’s Earth System Research Laboratory (ESRL), and his NOAA and CIRES colleagues analyzed data from systems that continuously monitor emissions at power plant stacks around the country. Previous aircraft-based studies have shown these stack measurements are accurate for carbon dioxide (CO2) and for nitrogen oxides and sulfur dioxide. Nitrogen oxides and sulfur dioxide can react in the atmosphere to form tiny particles and ozone, which can cause respiratory disease.
To compare pollutant emissions from different types of power plants, the scientists calculated emissions per unit of energy produced, for all data available between 1997 and 2012. During that period of time, on average:
- Coal-based power plants emitted 915 grams (32 ounces) of CO2 per kilowatt hour of energy produced;
- Natural gas power plants emitted 549 grams (19 ounces) CO2 per kilowatt hour; and
- Combined cycle natural gas plants emitted 436 grams (15 ounces) CO2 per kilowatt hour.
In combined cycle natural gas plants, operators use two heat engines in tandem to convert a higher fraction of heat into electrical energy. For context, U.S. households consumed 11,280 kilowatt hours of energy, on average, in 2011, according to the U.S. Energy Information Agency. This amounts to 11.4 metric tons per year of CO2 per household, if all of that electricity were generated by a coal power plant, or 5.4 metric tons if it all came from a natural gas power plant with combined cycle technology.
The researchers reported that between 1997 and 2012, the fraction of electric energy in the United States produced from coal gradually decreased from 83 percent to 59, and the fraction of energy from combined cycle natural gas plants rose from none to 34 percent.
That shift in the energy industry meant that power plants, overall, sent 23 percent less CO2 into the atmosphere last year than they would have, had coal been providing about the same fraction of electric power as in 1997, de Gouw said. The switch led to even greater reductions in the power sector’s emissions of nitrogen oxides and sulfur dioxide, which dropped by 40 percent and 44 percent, respectively.
The new findings are consistent with recent reports from the Energy Information Agency that substituting natural gas for coal in power generation helped lower power-related carbon dioxide emissions in 2012.
The authors noted that the new analysis is limited to pollutants emitted during energy production and measured at stacks. The paper did not address levels of greenhouse gases and other pollutants that leak into the atmosphere during fuel extraction, for example. To investigate the total atmospheric consequences of shifting energy use, scientists need to continue collecting data from all aspects of energy exploration, production and use, the authors concluded.
Authors of the new paper, “Reduced Emissions of CO2, NOx and SO2 from U.S. Power Plants Due to the Switch from Coal to Natural Gas with Combined Cycle Technology,” are de Gouw (CIRES), David Parrish (NOAA ESRL), Greg Frost (CIRES) and Michael Trainer (NOAA).
CIRES is a joint institute of NOAA and CU-Boulder.
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Climate change early warning system called for
Dec 3rd
Climate change has increased concern over possible large and rapid changes in the physical climate system, including Earth’s atmosphere, land surfaces and oceans, said Professor James White of CU-Boulder’s Institute of Arctic and Alpine Research and the chair of the National Research Council committee. Some abrupt changes and impacts already underway – including the loss of Arctic sea ice and increases in the extinction rates of marine and terrestrial species – and others could occur within a few decades or even years, said the committee.
“Research has helped us begin to distinguish more imminent threats from those that are less likely to happen this century,” said White, also a CU-Boulder professor in geological sciences. “Evaluating climate changes and impacts in terms of their potential magnitude and the likelihood they will occur will help policymakers and communities make informed decisions about how to prepare for or adapt to them.”
Other scenarios, such as the destabilization of the west Antarctic ice sheet, have potentially major consequences, but the probability of these changes occurring within the next century is not well understood, highlighting the need for more research, according to the committee.
In some cases, scientific understanding has progressed enough to determine whether certain high-impact climate changes are likely to happen within the next century. The report notes that a shutdown in the Atlantic Ocean circulation patterns or a rapid release of methane from high-latitude permafrost or undersea ice are now known to be unlikely this century, although these potential abrupt changes are still worrisome over longer time horizons.
But even changes in the physical climate system that happen gradually over many decades or centuries can cause abrupt ecological or socio-economic change once a “tipping point” is reached, the report adds. Relatively slow global sea-level rise could directly affect local infrastructure such as roads, airports, pipelines or subway systems if a sea wall or levee is breached. And slight increases in ocean acidity or surface temperatures could cross thresholds beyond which many species cannot survive, leading to rapid and irreversible changes in ecosystems that contribute to extinction events.
Further scientific research and enhanced monitoring of the climate, ecosystems and social systems may be able to provide information that a tipping point is imminent, allowing time for adaptation or possibly mitigation, or that a tipping point has recently occurred, the report says.
“Right now we don’t know what many of these thresholds are,” White said. “But with better information, we will be able to anticipate some major changes before they occur and help reduce the potential consequences.” The report identifies several research needs, such as identifying keystone species whose population decline due to an abrupt change would have cascading effects on ecosystems and ultimately on human provisions such as food supply.
If society hopes to anticipate tipping points in natural and human systems, an early warning system for abrupt changes needs to be developed, the report says. An effective system would need to include careful and vigilant monitoring, taking advantage of existing land and satellite systems and modifying them if necessary, or designing and implementing new systems when feasible. It would also need to be flexible and adaptive, regularly conducting and alternating between data collection, model testing and model predictions that suggest future data needs.
The study was sponsored by the National Oceanic and Atmospheric Administration, National Science Foundation, U.S. intelligence community, and the National Academies. The National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council make up the National Academies. They are private, independent nonprofit institutions that provide science, technology, and health policy advice under a congressional charter granted to NAS in 1863. The National Research Council is the principal operating agency of the National Academy of Sciences and the National Academy of Engineering.
For more information and a copy of the report visit http://national-academies.org. For more information on INSTAAR visithttp://instaar.colorado.edu.