Adding Carbon to the Equation in Online Flight Search

This study explores the potential to promote lower-emissions air travel by providing consumers with information about the carbon emissions of alternative flight choices in the context of online flight search and booking. Researchers surveyed over 450 UC Davis faculty, researchers, and staff, asking them to choose among hypothetical flight options for university-related business trips. Emissions estimates for flight alternatives were prominently displayed alongside cost, layovers and airport, and the lowest-emissions flight was labeled “Greenest Flight”. The researchers found an impressive rate of willingness to pay for lower-emissions flights: around $200/ton of CO2E saved, a magnitude higher than that seen in carbon offsets programs. They also found that displaying carbon information encouraged Davis employees to choose nonstop (lower-emissions) flights, when available, from a more distant airport over indirect flights from their preferred airport for medium-distance flights. In a second step of analysis, they estimated the carbon and cost impacts for UC Davis business travel if the university were to adopt a flight-search interface that prioritizes carbon emissions information and displays alternatives from multiple regional airports in their employee travel-booking portal. Based on the choice models from the survey data, a year’s worth of actual employee air travel data, and data collected on flight alternatives with respect to the flights chosen by employees, they estimated potential annual savings of more than 79 tons of CO2E, and a more impressive$56,000 reduction in airfare costs, due to an increased willingness of travelers to take advantage of cheaper (often nonstop) flight options out of SFO. Broader university policies encouraging lower-emissions flights and enhanced public transportation within the multi-airport mega-region would likely support much greater carbon savings. Institutionalizing this “nudge” within organizations with large travel budgets, like the UC system, could have an industry-wide impact in aviation.View the NCST Project Webpag

Normal variation for adaptive feature size

The change in the normal between any two nearby points on a closed, smooth surface is bounded with respect to the local feature size (distance to the medial axis). An incorrect proof of this lemma appeared as part of the analysis of the "crust" algorithm of Amenta and Bern

Case Study: Visualization of Evolutionary Trees

We describe a visualization tool which allows a biologist to explore a large set of hypothetical evolutionary trees. Interacting with such a dataset allows the biologist to identify distinct hypotheses about how different species or organisms evolved, which would not have been clear from traditional analyses. Our system integrates a point-set visualization of the distribution of hypothetical trees with detail views of an individual tree, or of a consensus tree summarizing a subset of trees. Efficient algorithms were required for the key tasks of computing distances between trees, finding consensus trees, and laying out the point-set visualization

Regression Depth and Center Points

We show that, for any set of n points in d dimensions, there exists a hyperplane with regression depth at least ceiling(n/(d+1)). as had been conjectured by Rousseeuw and Hubert. Dually, for any arrangement of n hyperplanes in d dimensions there exists a point that cannot escape to infinity without crossing at least ceiling(n/(d+1)) hyperplanes. We also apply our approach to related questions on the existence of partitions of the data into subsets such that a common plane has nonzero regression depth in each subset, and to the computational complexity of regression depth problems.Comment: 14 pages, 3 figure

GPU LSM: A Dynamic Dictionary Data Structure for the GPU

We develop a dynamic dictionary data structure for the GPU, supporting fast insertions and deletions, based on the Log Structured Merge tree (LSM). Our implementation on an NVIDIA K40c GPU has an average update (insertion or deletion) rate of 225 M elements/s, 13.5x faster than merging items into a sorted array. The GPU LSM supports the retrieval operations of lookup, count, and range query operations with an average rate of 75 M, 32 M and 23 M queries/s respectively. The trade-off for the dynamic updates is that the sorted array is almost twice as fast on retrievals. We believe that our GPU LSM is the first dynamic general-purpose dictionary data structure for the GPU.Comment: 11 pages, accepted to appear on the Proceedings of IEEE International Parallel and Distributed Processing Symposium (IPDPS'18

Largest Placement of One Convex Polygon Inside Another

Our aim was to detect tau tangles and beta amyloid plaques in retina for the early diagnosis of Alzheimers Disease (AD)

Surface Reconstruction from Noisy Point Clouds

We show that a simple modification of the power crust algorithm for surface reconstruction produces correct outputs in presence of noise. This is proved using a fairly realistic noise model. Our theoretical results are related to the problem of computing a stable subset of the medial axis. We demostrate the effectiveness of our algorithm with a number of experimental results