Geb Thomas

Dr. Geb Thomas


Research Focus & Metrics

Academic Career Length

26Years (2001-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

View All Publications
3 October 2012 in Human Factors: The Journal of the Human Factors and Ergonomics Society
Verified
Journal Article
Open access
PDF file
MSMark Schall
Mark Schall
MRMichelle L. Rusch
Michelle L. Rusch
JLJohn D. Lee
John D. Lee
JDJeffrey D. Dawson
Jeffrey D. Dawson
GTGeb Thomas
Geb Thomas
MRMatthew Rizzo
Matthew Rizzo
The aim of this study was to evaluate the effectiveness of augmented reality (AR) cues in improving driving safety among elderly drivers who are at increased crash risk because of cognitive impairments. Cognitively challenging driving environments pose a particular crash risk for elderly drivers. AR cuing is a promising technology to mitigate risk by directing driver attention to roadway hazards. We investigate whether AR cues improve or interfere with hazard perception in elderly drivers with age-related cognitive decline. A total of 20 elderly (M = 73 years, SD = 5) licensed drivers with a range of cognitive abilities measured by a speed-of-processing (SOP) composite participated in a 1-hr drive in an interactive, fixed-base driving simulator. Each participant drove through six straight, 6-mile-long, rural roadway scenarios following a lead vehicle. AR cues directed attention to potential roadside hazards in three of the scenarios, and the other three were uncued (baseline) drives. Effects of AR cuing were evaluated with respect to (a) detection of hazardous target objects, (b) interference with detecting nonhazardous secondary objects, and (c) impairment in maintaining safe distance behind a lead vehicle. AR cuing improved the detection of hazardous target objects of low visibility. AR cues did not interfere with detection of nonhazardous secondary objects and did not impair ability to maintain safe distance behind a lead vehicle. SOP capacity did not moderate those effects. AR cues show promise for improving elderly driver safety by increasing hazard detection likelihood without interfering with other driving tasks, such as maintaining safe headway.

17 June 2015 in Journal of Bone and Joint Surgery
Verified
Journal Article
Closed access
PDF file
MKMatthew D. Karam
Matthew D. Karam
GTGeb Thomas
Geb Thomas
DKDaniel M. Koehler
Daniel M. Koehler
BWBrian O. Westerlind
Brian O. Westerlind
PLPaul M. Lafferty
Paul M. Lafferty
DADonald D. Anderson
Donald D. Anderson
Background: The evolving surgical skills education paradigm in orthopaedics has generated a strong demand for validated educational tools and methodologies. This study aimed to confirm that a one-on-one faculty coaching review of the head-mounted video recording of a resident’s surgical performance on a validated articular fracture simulation trainer would substantially improve subsequent performance. Methods: Fifteen first-year or second-year orthopaedic surgery residents reduced and fixed a standardized intra-articular tibial plafond fracture model under fluoroscopic guidance. Their performances were recorded by a head-mounted video camera. Prior to repeating the procedure six weeks later, eight subjects (the intervention group) reviewed the video of their performance with an orthopaedic traumatologist, and seven subjects (the control group) did not. Cohort performance was compared with respect to task duration, number of fluoroscopic images, and scores on the Objective Structured Assessment of Technical Skills (OSATS) as evaluated by fellowship-trained orthopaedic traumatologists blinded to the residents’ year in training and prior surgical experience. Results: The initial performance OSATS scores were not significantly different (p ≥ 0.05) between the control and intervention groups. Assessments of their repeat performance showed a significant net interval improvement (p < 0.05) in OSATS scores in the intervention group (mean [and standard deviation], 21 ± 8 points) compared with the control group (6 ± 3 points). The mean fluoroscopy utilization had a significant net decrease (p < 0.05) in the intervention group (−5.4 ± 11.7 points) compared with the control group (5.3 ± 7.0 points). Task duration in the repeat performance was similar between both groups. Conclusions: Personalized video-based feedback improved performance on a standardized articular fracture trainer for first-year and second-year residents. The described technique may further enhance resident surgical skills education.

1 January 2001 in Computer Methods and Programs in Biomedicine
Verified
Journal Article
Closed access
GTGeb Thomas
Geb Thomas
LJLynn Johnson
Lynn Johnson
SDSteven Dow
Steven Dow
CSClark Stanford
Clark Stanford

3 May 2018 in Sensors
Verified
Journal Article
Open access
PDF file
GTGeb Thomas
Geb Thomas
Sinan SousanSinan Sousan
Sinan Sousan
MTMarcus Tatum
Marcus Tatum
XLXiaoxing Liu
Xiaoxing Liu
CZChristopher Zuidema
Christopher Zuidema
TPThomas M. Peters
Thomas M. Peters
An integrated network of environmental monitors was developed to continuously measure several airborne hazards in a manufacturing facility. The monitors integrated low-cost sensors to measure particulate matter, carbon monoxide, ozone and nitrogen dioxide, noise, temperature and humidity. The monitors were developed and tested in situ for three months in several overlapping deployments, before a full cohort of 40 was deployed in a heavy vehicle manufacturing facility for a year of data collection. The monitors collect data from each sensor and report them to a central database every 5 min. The work includes an experimental validation of the particle, gas and noise monitors. The R2 for the particle sensor ranges between 0.98 and 0.99 for particle mass densities up to 300 μg/m3. The R2 for the carbon monoxide sensor is 0.99 for concentrations up to 15 ppm. The R2 for the oxidizing gas sensor is 0.98 over the sensitive range from 20 to 180 ppb. The noise monitor is precise within 1% between 65 and 95 dBA. This work demonstrates the capability of distributed monitoring as a means to examine exposure variability in both space and time, building an important preliminary step towards a new approach for workplace hazard monitoring.

22 January 2019 in Annals of Work Exposures and Health
Verified
Journal Article
Open access
PDF file
CZChristopher Zuidema
Christopher Zuidema
Sinan SousanSinan Sousan
Sinan Sousan
LSLarissa V Stebounova
Larissa V Stebounova
AGAlyson Gray
Alyson Gray
XLXiaoxing Liu
Xiaoxing Liu
KKKirsten Koehler
Kirsten Koehler
Due to their small size, low-power demands, and customizability, low-cost sensors can be deployed in collections that are spatially distributed in the environment, known as sensor networks. The literature contains examples of such networks in the ambient environment; this article describes the development and deployment of a 40-node multi-hazard network, constructed with low-cost sensors for particulate matter (SHARP GP2Y1010AU0F), carbon monoxide (Alphasense CO-B4), oxidizing gases (Alphasense OX-B421), and noise (developed in-house) in a heavy-vehicle manufacturing facility. Network nodes communicated wirelessly with a central database in order to record hazard measurements at 5-min intervals. Here, we report on the temporal and spatial measurements from the network, precision of network measurements, and accuracy of network measurements with respect to field reference instruments through 8 months of continuous deployment. During typical production periods, 1-h mean hazard levels ± standard deviation across all monitors for particulate matter (PM), carbon monoxide (CO), oxidizing gases (OX), and noise were 0.62 ± 0.2 mg m−3, 7 ± 2 ppm, 155 ± 58 ppb, and 82 ± 1 dBA, respectively. We observed clear diurnal and weekly temporal patterns for all hazards and daily, hazard-specific spatial patterns attributable to general manufacturing processes in the facility. Processes associated with the highest hazard levels were machining and welding (PM and noise), staging (CO), and manual and robotic welding (OX). Network sensors exhibited varying degrees of precision with 95% of measurements among three collocated nodes within 0.21 mg m−3 for PM, 0.4 ppm for CO, 9 ppb for OX, and 1 dBA for noise of each other. The median percent bias with reference to direct-reading instruments was 27%, 11%, 45%, and 1%, for PM, CO, OX, and noise, respectively. This study demonstrates the successful long-term deployment of a multi-hazard sensor network in an industrial manufacturing setting and illustrates the high temporal and spatial resolution of hazard data that sensor and monitor networks are capable of. We show that network-derived hazard measurements offer rich datasets to comprehensively assess occupational hazards. Our network sets the stage for the characterization of occupational exposures on the individual level with wireless sensor networks.

8 September 2018 in Sensors
Verified
Journal Article
Open access
PDF file
Sinan SousanSinan Sousan
Sinan Sousan
AGAlyson Gray
Alyson Gray
CZChristopher Zuidema
Christopher Zuidema
LSLarissa Stebounova
Larissa Stebounova
GTGeb Thomas
Geb Thomas
TPThomas Peters
Thomas Peters
Deployment of low-cost sensors in the field is increasingly popular. However, each sensor requires on-site calibration to increase the accuracy of the measurements. We established a laboratory method, the Average Slope Method, to select sensors with similar response so that a single, on-site calibration for one sensor can be used for all other sensors. The laboratory method was performed with aerosolized salt. Based on linear regression, we calculated slopes for 100 particulate matter (PM) sensors, and 50% of the PM sensors fell within ±14% of the average slope. We then compared our Average Slope Method with an Individual Slope Method and concluded that our first method balanced convenience and precision for our application. Laboratory selection was tested in the field, where we deployed 40 PM sensors inside a heavy-manufacturing site at spatially optimal locations and performed a field calibration to calculate a slope for three PM sensors with a reference instrument at one location. The average slope was applied to all PM sensors for mass concentration calculations. The calculated percent differences in the field were similar to the laboratory results. Therefore, we established a method that reduces the time and cost associated with calibration of low-cost sensors in the field.