Janet Brelin-Fornari

Establishing reference values for cervical spine range of motion in pre-pubescent children

Medical professionals, physical therapists, product designers, and computational models all use cervical spine range of motion reference values. To support these functions, researchers have collected a plethora of data to determine the normal range of motion of the cervical spine of adult subjects. However, little to no data exists for subjects under the age of 14. This study utilized the cervical range of motion device, referenced with respect to the Frankfort Plane, to measure the active cervical spine range of motion in all three cardinal planes of the human body, for 106 subjects whose ages ranged from 8 to 10 years. The active range of motion for flexion, extension, lateral extension, and rotation was calculated as 66+/-13 degrees , 85+/-14 degrees , 58+/-8 degrees , and 77+/-7 degrees , respectively, using linear statistics. The observed data significantly differed from the published American Medical Association guidelines for adults but fell within the range of the reference values for 10 year olds. Stratifying and analyzing the range of motion data with respect to gender yielded no significant effect. Appendix A analyzes the data using angular statistics, and produces virtually identical results as those from linear statistics.

Effect of Seat Belts Equipped with Pretensioners on Rear Seat Adult Occupants in High-Severity Rear Impact

This paper provides a preliminary investigation of occupant kinematics for rear seat occupants involved in high-severity rear impacts. The effect of seatbelts equipped with or without a pyrotechnic pretensioner on restraining the rear seat adult occupant was evaluated in the paper. Further, the study examined the result of the occupants seating alignment by comparing a Nominal Seating Position (NSP) to an occupant whose torso would be rotated forward to be placed in a Moderately Displaced Position (MDP) prior to impact. A series of eight sled tests were performed using a deceleration sled subjected to a delta-V of 30 mph. Instrumented HIII 50th and 5th ATDs were positioned in the outboard, rear seating positions. The study found that pretensioners had little effect on the occupant kinematics of rear seat occupants in either the NSP or the MDP. But, there were marked differences in kinematic evaluations between the occupant seating alignment configurations. HIC 15, HIC 36, Ncf, Nte, Ntf, peak chest acceleration, and peak, resultant pelvis acceleration all increased when the occupants torso was displaced forward prior to the rear impact.

Physically correlated muscle activation for a human head and neck computational model

A computational 50th percentile male head and neck complex model was correlated to physical experimental data. The computational model utilizes 15 muscle pairs represented by the Hill Muscle Model with the complete head/neck system modeled using MADYMO™. The model was used for analysis and optimization of activation and deactivation of muscle activity in flexion and extension. Sensitivity analysis performed using the model shows that, of the multiple parameters within the Hill Model, activation level and timing prove to have the greatest effect on the system kinematics. In addition, the rate by which an activation level is changed becomes an important factor in the simulation. With the use of numerical optimization techniques, a pattern was determined for the applied activation/deactivation rates and timing of flexors and extensors during flexion and extension of the head. The numerical optimization result correlated to within 9% of measured value during the initial flexion of the head. The optimized activation model reflected an activation onset 90 ms after the start of the impulse load, which agrees with published reaction times of muscles. Activation and deactivation rates for the extensors were found to be 1.7 and 0.29%, respectively. While the onset of activation of the flexor muscles occurred before rebound, it was found that muscles, at near the mid-plane, were triggered by the optimized model to abate the flexion. Rates of activation and deactivation of the flexors were found to be 0.9 and 0.3%, respectively. Both the extensors as well as the flexors were found to activate only up to 70% before deactivating. Therefore, it was evident from this study that using the Hill Muscle Model with the activation parameter modeled as binary, 0 or 100%, may lead to inaccurate simulation results.

Quantifying R2 bias in the presence of measurement error

Measurement error (ME) is the difference between the true unknown value of a variable and the data assigned to that variable during the measuring process. The multiple correlation coefficient quantifies the strength of the relationship between the dependent and independent variable(s) in regression modeling. In this paper, we show that ME in the dependent variable results in a negative bias in the multiple correlation coefficient, making the relationship appear weaker than it should. The adjusted R 2 provides regression modelers an unbiased estimate of the multiple correlation coefficient. However, due to the ME induced bias in the multiple correlation coefficient, the otherwise unbiased adjusted R 2 under-estimates the variance explained by a regression model. This paper proposes two statistics for estimating the multiple correlation coefficient, both of which take into account the ME in the dependent variable. The first statistic uses all unbiased estimators, but may produce values outside the [0,1] interval. The second statistic requires modeling a single data set, created by including descriptive variables on the subjects used in a gage study. Based on sums of squares, the statistic has the properties of an R 2: it measures the proportion of variance explained; has values restricted to the [0,1] interval; and the endpoints indicate no variance explained and all variance explained respectively. We demonstrate the methodology using data from a study of cervical spine range of motion in children.

Evaluating Impact Attenuator Performance for a Formula SAE Vehicle

Formula SAE® is one of several student design competitions organized by SAE International. In the Formula SAE events undergraduate and graduate students are required to conceive, design, fabricate and compete with a small, formula-style, race car. Formula SAE safety rules dictate a 7 m/s (or approximately 15.65 mph) frontal crash test for nose mounted impact attenuators. These rules are outlined in section B3.21 of the Formula SAE rule book. Development and testing methods of these energy absorbing devices have varied widely among teams. This paper uses real world crash sled results to research methods for predicting the performance of aluminum honeycomb impact attenuators that will comply with the Formula SAE standards. However, the resulting models used to predict attenuator performance may also have a variety of useful applications outside of Formula SAE. In this paper, various energy absorbers were mounted to a free rolling trolley sitting on top of a crash sled. The sled was launched so that the trolley with the attached attenuator was allowed to strike a rigid barrier. This resulted in a sudden deceleration measured by accelerometers attached to the trolley. The resulting deceleration from each impact attenuator was then correlated to predicted pulses from theoretical calculations. The lessons learned from extensive testing will be discussed including comparisons between size, shapes, and material properties of energy absorption devices. Additionally, a final theory will be presented describing the ideal way to predict impact attenuator performance. Ultimately it will be shown that, given a known geometry, material properties, and safety factor, the behavior of an impact attenuator can be predicted accurately enough that testing will only be needed as verification. This study will ultimately benefit all Formula SAE® teams, as it will help speed up development time and cut costs, while providing a proven method for creating attenuators that will perform to SAE standards.