Massoud Tavakoli

Volume and surface area study of tobramycin-polymethylmethacrylate beads.

Polymethylmethacrylate bone cement beads impregnated with antibiotic are a common treatment for patients with persistent articular joint infections or osteomyelitis. They also are used as a prophylaxis for infection in patients with large soft tissue wounds. The current study was designed to evaluate the relationship between bead geometry and elution of the antibiotic tobramycin by methodically varying the shape of the beads for a given set of volumes. Beads of five shapes (spherical to ovoid) and two volumes were prepared and studied. Only 0.9% to 3.3% of the total amount of tobramycin present actually eluted from the beads in a 96-hour period and of this amount, approximately ⅓ eluted within the first 4 hours. The elution mass data indicate the benefit of numerous, small and elliptically shaped beads for maximal antibiotic availability. Additionally, a mathematical model is presented that describes these findings and can be used to predict tobramycin delivery rates from bone cement beads. This model assumes that the antibiotic is delivered through two mechanisms: fast dissolution of tobramycin initially adhering to the bead surface and slow release by diffusion through the polymer. The results generate diffusion coefficients for tobramycin in polymethylmethacrylate bone cement on the order of 2 × 10−11 cm2/s.

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.

Concurrent Teaching of Engineering Design, Analysis and Manufacturing

In this paper, we first offer a brief overview of the literature on recent efforts in engineering design education, followed by a discussion of the challenges involved with teaching engineering design at an early stage in the curriculum. We then propose an approach utilizing a multi-track teaching style that allows for concurrent teaching of engineering design, analysis and manufacturing. We provide details of how a traditional sophomore-level introductory design course at Kettering University (formerly GMI Engineering & Management Institute) has been modified over the past five years to face pedagogical challenges and accommodate our ideas on the proposed teaching style. The evolution of the ideas, the philosophy behind them and the effects of their implementation on the course are also discussed. Finally, we address teaching quality control, time and budgetary issues.

Design for Assembly Versus Design for Disassembly: A Comparison of Guidelines

As key issues in product life-cycle investigations. Design for Assembly (DFA) and Design for Disassembly (DFD) have received increasingly more attention. While some DFA techniques have reached a reasonable level of maturity, DFD methodology is still in its early stages of development. There has been little research on the relationship between DFA and DFD, especially as it pertains to their implementation. in this paper, the relationship between DFA and DFD rules is explored through a case study, where assemble and disassembly time data are collected for a commercial device. Then, a DFA and a DFD tool are applied to this device, and the results are examined to gauge the degree of overlap between DFA and DFD rules.Copyright

Estimation of Frontal Crush Stiffness Coefficients for Car-to-Heavy Truck Underride Collisions

The objective of this paper was to evaluate a public domain finite element (FE) model of a 1990 Ford Taurus from the perspective of crush energy absorption. The validity of the FE model was examined by comparing simulation results to several published full-frontal crash tests. The suitability of the model for underride simulation was evaluated against two series of full-scale crash tests into vertically offset rigid barriers. Next, the evaluated FE model was used to pursue the main objective of this work, namely to develop an approach for estimating underride crush energy. The linear-spring methodology was adopted whereby the underride crush stiffness was determined by relating the residual upper radiator support deformation to crush energy. An underride crush stiffness estimation method was proposed based on modifying the full-frontal stiffness coefficients. The method was further simplified into a “Rule-of-Thumb” estimation method, and an example of its application was provided along with a discussion of its estimation accuracy.

Paired vehicle occupant analysis indicates age and crash severity moderate likelihood of higher severity injury in second row seated adults in frontal crashes

The majority of advances in occupant protection systems for motor vehicle occupants have focused on occupants seated in the front row of the vehicle. Recent studies suggest that these systems have resulted in lower injury risk for front row occupants as compared to those in the second row. However, these findings are not universal. In addition, some of these findings result from analyses that compare groups of front and second row occupants exposed to dissimilar crash conditions, raising questions regarding whether they might reflect differences in the crash rather than the front and second row restraint systems. The current study examines factors associated with injury risk for pairs of right front seat and second row occupants in frontal crashes in the United States using paired data analysis techniques. These data indicate that the occupant seated in the front row frequently experiences the more severe injury in the pair, however there were no significant differences in the rate of occurrence of these events and events where the more severe injury occurs in the second row occupant of the pair. A logistic regression indicated that the likelihood of the more severe injury occurring in the second row seated occupant of the pair increased as crash severity increased, consistent with data from anatomic test dummy (ATD) tests. It also indicated that the second row occupant was more likely to have the more severe injury in the pair if that occupant was the older occupant of the pair. These findings suggest that occupant protection systems which focus on providing protection specifically for injuries experienced by older occupants in the second row in higher severity crash conditions might provide the greatest benefit.

THE USE OF FINITE ELEMENT METHOD TO ADDRESS PROXIMAL MIGRATION OF FEMORAL NECK FRACTURE FIXATION DEVICES IN THE ELDERLY

Falls among the elderly are a common occurrence and the incidence rate is increasing with our aging population. In such a population, a fall may precipitate a femoral neck fracture which may be treated by any one of a variety of femoral screw/plate mechanisms. Unfortunately, such mechanisms can fail in service as the device migrates proximally eventually requiring a secondary and more invasive surgery. In the current study we propose a new design to address this failure mechanism and we use a simple finite element model to study a modification to the current design.

Injury severity data for front and second row passengers in frontal crashes

The data contained here were obtained from the National Highway Transportation Safety Administration׳s National Automotive Sampling System – Crashworthiness Data System (NASS-CDS) for the years 2008–2014. This publically available data set monitors motor vehicle crashes in the United States, using a stratified random sample frame, resulting in information on approximately 5000 crashes each year that can be utilized to create national estimates for crashes. The NASS-CDS data sets document vehicle, crash, and occupant factors. These data can be utilized to examine public health, law enforcement, roadway planning, and vehicle design issues. The data provided in this brief are a subset of crash events and occupants. The crashes provided are exclusively frontal crashes. Within these crashes, only restrained occupants who were seated in the right front seat position or the second row outboard seat positions were included. The front row and second row data sets were utilized to construct occupant pairs crashes where both a right front seat occupant and a second row occupant were available. Both unpaired and paired data sets are provided in this brief.