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By NASA
Download PDF: Statistical Analysis Using Random Forest Algorithm Provides Key Insights into Parachute Energy Modulator System
Energy modulators (EM), also known as energy absorbers, are safety-critical components that are used to control shocks and impulses in a load path. EMs are textile devices typically manufactured out of nylon, Kevlar® and other materials, and control loads by breaking rows of stitches that bind a strong base webbing together as shown in Figure 1. A familiar EM application is a fall-protection harness used by workers to prevent injury from shock loads when the harness arrests a fall. EMs are also widely used in parachute systems to control shock loads experienced during the various stages of parachute system deployment.
Random forest is an innovative algorithm for data classification used in statistics and machine learning. It is an easy to use and highly flexible ensemble learning method. The random forest algorithm is capable of modeling both categorical and continuous data and can handle large datasets, making it applicable in many situations. It also makes it easy to evaluate the relative importance of variables and maintains accuracy even when a dataset has missing values.
Random forests model the relationship between a response variable and a set of predictor or independent variables by creating a collection of decision trees. Each decision tree is built from a random sample of the data. The individual trees are then combined through methods such as averaging or voting to determine the final prediction (Figure 2). A decision tree is a non-parametric supervised learning algorithm that partitions the data using a series of branching binary decisions. Decision trees inherently identify key features of the data and provide a ranking of the contribution of each feature based on when it becomes relevant. This capability can be used to determine the relative importance of the input variables (Figure 3). Decision trees are useful for exploring relationships but can have poor accuracy unless they are combined into random forests or other tree-based models.
The performance of a random forest can be evaluated using out-of-bag error and cross-validation techniques. Random forests often use random sampling with replacement from the original dataset to create each decision tree. This is also known as bootstrap sampling and forms a bootstrap forest. The data included in the bootstrap sample are referred to as in-the-bag, while the data not selected are out-of-bag. Since the out-of-bag data were not used to generate the decision tree, they can be used as an internal measure of the accuracy of the model. Cross-validation can be used to assess how well the results of a random forest model will generalize to an independent dataset. In this approach, the data are split into a training dataset used to generate the decision trees and build the model and a validation dataset used to evaluate the model’s performance. Evaluating the model on the independent validation dataset provides an estimate of how accurately the model will perform in practice and helps avoid problems such as overfitting or sampling bias. A good model performs well on
both the training data and the validation data.
The complex nature of the EM system made it difficult for the team to identify how various parameters influenced EM behavior. A bootstrap forest analysis was applied to the test dataset and was able to identify five key variables associated with higher probability of damage and/or anomalous behavior. The identified key variables provided a basis for further testing and redesign of the EM system. These results also provided essential insight to the investigation and aided in development of flight rationale for future use cases.
For information, contact Dr. Sara R. Wilson. sara.r.wilson@nasa.gov
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By NASA
3 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Dr. Rainee Simons (right) and Dr. Félix Miranda work together to create technology supporting heart health at NASA’s Glenn Research Center in Cleveland.Credit: NASA Prioritizing health is important on Earth, and it’s even more important in space. Exploring beyond the Earth’s surface exposes humans to conditions that can impact blood pressure, bone density, immune health, and much more. With this in mind, two NASA inventors joined forces 20 years ago to create a way to someday monitor astronaut heart health on long-duration spaceflight missions. This technology is now being used to monitor the health of patients with heart failure on Earth through a commercial product that is slated to launch in late 2024.
NASA inventors Dr. Rainee Simons, senior microwave communications engineer, and Dr. Félix Miranda, deputy chief of the Communications and Intelligent Systems Division, applied their expertise in radio frequency integrated circuits and antennas to create a miniature implantable sensor system to keep track of astronaut health in space. The technology, which was created at NASA’s Glenn Research Center in Cleveland with seed funds from the agency’s Technology Transfer Office, consists of a small bio-implanted sensor that can transmit a person’s health status from a sensor to a handheld device. The sensor is battery-less and wireless.
“You’re able to insert the sensor and bring it up to the heart or the aorta like a stent – the same process as in a stent implant,” Simons said. “No major surgery is needed for implantation, and operating the external handheld device, by the patient, is simple and easy.”
After Glenn patented the invention, Dr. Anthony Nunez, a heart surgeon, and Harry Rowland, a mechanical engineer, licensed the technology and founded a digital health medical technology company in 2007 called Endotronix, now an Edwards Lifesciences company. The company focuses on enabling proactive heart failure management with data-driven patient-to-physician solutions that detect dangers, based on the Glenn technology. The Endotronix primary monitoring system is called the Cordella Pulmonary Artery (PA) Sensor System. Dr. Nunez became aware of the technology while reading a technical journal that featured the concept, and he saw parallels that could be used in the medical technology industry.
The concept has proven to be an aid for heart failure management through several clinical trials, and patients have experienced improvements in their quality of life. Based on the outcome of Endotronix’s clinical testing to demonstrate safety and effectiveness, in June 2024 the U.S. Food and Drug Administration granted premarket approval to the Cordella PA Sensor System. The system is meant to help clinicians remotely assess, treat, and manage heart failure in patients at home with the goal of reducing hospitalizations.
“If you look at the statistics of how many people have congestive heart failure, high blood pressure… it’s a lot of people,” Miranda said. “To have the medical community saying we have a device that started from NASA’s intellectual property – and it could help people worldwide to be healthy, to enjoy life, to go about their business – is highly gratifying, and it’s very consistent with NASA’s mission to do work for the benefit of all.”
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By NASA
5 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Pacific Island nations such as Kiribati — a low-lying country in the southern Pacific Ocean — are preparing now for a future of higher sea levels.NASA Earth Observatory Climate change is rapidly reshaping a region of the world that’s home to millions of people.
In the next 30 years, Pacific Island nations such as Tuvalu, Kiribati, and Fiji will experience at least 8 inches (15 centimeters) of sea level rise, according to an analysis by NASA’s sea level change science team. This amount of rise will occur regardless of whether greenhouse gas emissions change in the coming years.
The sea level change team undertook the analysis of this region at the request of several Pacific Island nations, including Tuvalu and Kiribati, and in close coordination with the U.S. Department of State.
In addition to the overall analysis, the agency’s sea level team produced high-resolution maps showing which areas of different Pacific Island nations will be vulnerable to high-tide flooding — otherwise known as nuisance flooding or sunny day flooding — by the 2050s. Released on Sept. 23, the maps outline flooding potential in a range of emissions scenarios, from best-case to business-as-usual to worst-case.
“Sea level will continue to rise for centuries, causing more frequent flooding,” said Nadya Vinogradova Shiffer, who directs ocean physics programs for NASA’s Earth Science Division. “NASA’s new flood tool tells you what the potential increase in flooding frequency and severity look like in the next decades for the coastal communities of the Pacific Island nations.”
Team members, led by researchers at the University of Hawaii and in collaboration with scientists at the University of Colorado and Virginia Tech, started with flood maps of Kiribati, Tuvalu, Fiji, Nauru, and Niue. They plan to build high-resolution maps for other Pacific Island nations in the near future. The maps can assist Pacific Island nations in deciding where to focus mitigation efforts.
“Science and data can help the community of Tuvalu in relaying accurate sea level rise projections,” said Grace Malie, a youth leader from Tuvalu who is involved with the Rising Nations Initiative, a United Nations-supported program led by Pacific Island nations to help preserve their statehood and protect the rights and heritage of populations affected by climate change. “This will also help with early warning systems, which is something that our country is focusing on at the moment.”
Future Flooding
The analysis by the sea level change team also found that the number of high-tide flooding days in an average year will increase by an order of magnitude for nearly all Pacific Island nations by the 2050s. Portions of the NASA team’s analysis were included in a sea level rise report published by the United Nations in August 2024.
Areas of Tuvalu that currently see less than five high-tide flood days a year could average 25 flood days annually by the 2050s. Regions of Kiribati that see fewer than five flood days a year today will experience an average of 65 flood days annually by the 2050s.
“I am living the reality of climate change,” said Malie. “Everyone (in Tuvalu) lives by the coast or along the coastline, so everyone gets heavily affected by this.”
Flooding on island nations can come from the ocean inundating land during storms or during exceptionally high tides, called king tides. But it can also result when saltwater intrudes into underground areas and pushes the water table to the surface. “There are points on the island where we will see seawater bubbling from beneath the surface and heavily flooding the area,” Malie added.
Matter of Location
Sea level rise doesn’t occur uniformly around the world. A combination of global and local conditions, such as the topography of a coastline and how glacial meltwater is distributed in the ocean, affects the amount of rise a particular region will experience.
“We’re always focused on the differences in sea level rise from one region to another, but in the Pacific, the numbers are surprisingly consistent,” said Ben Hamlington, a sea level researcher at NASA’s Jet Propulsion Laboratory in Southern California and the agency’s sea level change science team lead.
The impacts of 8 inches (15 centimeters) of sea level rise will vary from country to country. For instance, some nations could experience nuisance flooding several times a year at their airport, while others might face frequent neighborhood flooding equivalent to being inundated for nearly half the year.
Researchers would like to combine satellite data on ocean levels with ground-based measurements of sea levels at specific points, as well as with better land elevation information. “But there’s a real lack of on-the-ground data in these countries,” said Hamlington. The combination of space-based and ground-based measurements can yield more precise sea level rise projections and improved understanding of the impacts to countries in the Pacific.
“The future of the young people of Tuvalu is already at stake,” said Malie. “Climate change is more than an environmental crisis. It is about justice, survival for nations like Tuvalu, and global responsibility.”
To explore the high-tide flooding maps for Pacific Island nations, go to:
https://sealevel.nasa.gov
News Media Contacts
Jane J. Lee / Andrew Wang
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0307 / 626-379-6874
jane.j.lee@jpl.nasa.gov / andrew.wang@jpl.nasa.gov
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Last Updated Sep 25, 2024 Related Terms
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