Effects of Common Breaching Practices on the Overpressures Recorded Within the Stack

The objective of this paper is to provide useful information to both military and law enforcement dynamic entry teams for estimating the level of protection provided by their standard protective equipment and procedures. The procedures investigated include: the K-Equation for predicting safe standoff, the effects of stack spacing, and the effect of the orientation of the stack within the blast field on the breachers’ blast exposure. This investigation leveraged both experimental data gathered during explosive breaching training exercises (Breacher Consortium, 2011 - draft) and numerical simulations using the shock physics code CTH (McGlaun, 1990). The analysis revealed that the presence of objects within the blast range, including the other team members, significantly affected the individual’s exposure to the point that it sometimes exceeds current exposure recommendations. When each team member’s exposure was compared to the current limit of 4 psi (28 kPa), the average pressure from the gauges on the breacher helmets exceeded that level 43% of the time, and the averaged pressure at the shoulders exceeded the limit 50% of the time. In a comparison of the measured incident impulse energy to the maximum impulse energy predicted based on 4 psi peak pressure, the helmet impulse energy was exceeded 79% of the time and 64% of the time at the shoulders. Because the K-Equation was shown to be accurate in predicting the free-field pressure, these results and the output from the numerical simulations suggest that the stack and blanket do not provide the level of protection anticipated and that reducing the standoff distance, as prescribed by some protocols, is not justified. Ultimately, the operational impact of these results will depend on efforts to identify blast exposure injury thresholds. Since there is a direct relationship between the peak overpressure and total impulse to which the breaching team members in the stack are exposed, injury thresholds must reveal which component, pressure, impulse or a combination is more injurious. Based on whether pressure or impulse must be minimized, the ideal stack configuration can be calculated using the developed numerical model.

Mechanics of Hip Dysplasia Reduction in Infants With the Pavlik Harness Using Patient-Specific Geometry

A physics-based computational model of neonatal Developmental Dysplasia of the Hip (DDH) following treatment with the Pavlik Harness was developed to obtain muscle force contribution in order to elucidate biomechanical factors influencing the reduction of dislocated hips. Clinical observation indicates that reduction occurs in deep sleep and involves passive muscle action. Consequently, a set of five (5) adductor muscles, namely, the Adductor Brevis, Adductor Longus, Adductor Magnus, Pectineus, and Gracilis were identified as mediators of reduction using the Pavlik Harness. A Fung-type model was used to characterize the hyperelastic stress-strain muscle response. Four grades (1–4) of dislocation as specified by the International Hip Dysplasia Institute (IHDI) were considered. A three-dimensional model of the pelvis-femur-lower limb assembly of a representative 10 week-old female was generated based on CT scans of a 6-month and 14-year old female as well as the visible human project with the aid of anthropomorphic scaling of anatomical landmarks. The muscle model was calibrated to achieve equilibrium at 90° flexion and 80° abduction. The hip was computationally dislocated according to the grade under investigation, the femur was restrained to move in an envelope consistent with Pavlik Harness restraints, and the dynamic response under passive muscle action and under the effect of gravity was resolved using the ADAMS solver in Solidworks. Results of the current model with an anteversion angle of 50° show successful reduction IHDI Grades 1–3, while IHDI Grade 4 failed to reduce with the Pavlik Harness. These results are consistent with a previous study based on a simplified anatomically-consistent synthetic model and clinical reports of very low success of the Pavlik Harness for Grade 4. However, our model indicates that it is possible to achieve reduction of Grade 4 dislocation by hyperflexion. This finding is consistent with clinical procedures that utilize hyperflexion to help achieve reduction for patients with severe levels of DDH for whom the Pavlik Harness fails.

Novel Periodic and Turning Motions in the Simplest Passive Walking Model

The ability to move along curved paths is an essential feature for biped walkers to move around obstacles. This study is aimed at extending passive walking concept for curved walking and turning to generate more natural and effective motion. Hence three-dimensional (3D) motion of a rimless spoked-wheel, as the simplest walking model, about a general vertical fixed coordinate system has been derived. Then, two kinds of a stable passive turning, i.e. limited and circular continuous have been considered and discussed. The first kind is actually transferring from a 2D periodic motion to another, and can be implemented on a straight slope surface. While, it was shown that the second kind is just related to novel 3D periodic motions and can be recognized on a special surface profile namely “helical slope” introduced here. The latter are interpreted as 3D fixed points of a Poincare return map again. So, their stability was evaluated numerically by a Jacobian analysis and demonstrated through several simulations. Results show asymptotical stability of such motions and their considerable basin of attraction with respect to initial states. In addition, the characteristic of passive turning is shown to be strictly connected with the value of the initial perturbed condition, for instance, to the initial inclination of the wheel. It is then surprising to note that the stability of a 3D passive periodic motion (turning) is higher than 2D one (straight walking) which is actually a special case just with an infinite radius of turn.

Effect of Heel to Toe Walking on Time Optimal Walking of a Biped During Single Support Phase

Dynamic modeling of a biped has gained lots of attention during past few decades. While stability and energy consumption were among the first issues which were considered by researchers, nowadays achieving maximum speed and improving pattern of motion to reach that speed are the important targets in this field. Walking model of bipeds usually includes two phases, single support phase (SSP), in which only the stance foot is in contact with the ground while the opposite leg is swinging; and double support phase (DSP) in which the swing leg is in contact with the ground in addition to the rear foot. It is common in the simplified model of walking to assume the stance leg foot, flat during the entire SSP; but one may know that for human walking, there is also a sub-phase during SSP in which the heel of stance foot leaves the ground while the whole body is supported by toe link. Actually in this sub phase the stance leg foot rotates around the toe joint. This paper is trying to study the effect of toe-link and heel to toe walking model on dynamic and specially speed of walking compare to flat foot model.

Investigation of Lumbosacral Spine Anatomical Variation Effect on Load-Partitioning Under Follower Load Using Geometrically Personalized Finite Element Model

The spinal load sharing and mechanical stresses developed in the spine segments due to mechanical loads are dependent on the unique spinal anatomy (geometry and posture). Variation in spinal curvature alters the load sharing of the lumbar spine as well as the stiffness and stability of the passive tissues. In this paper, effects of lumbar spine curvature variation on spinal load sharing under compressive Follower Load (FL) are investigated numerically. 3D nonlinear Finite Element (FE) models of three ligamentous lumbosacral spines are developed based on personalized geometries; hypo-lordotic (Hypo-L), normal (Normal-L) and hyper-lordotic (Hyper-L) cases. Analysis of each model is performed under Follower Load and developed stress in the discs and forces in the collagen fibers are investigated. Stresses on the discs vary in magnitude and distribution depending on the degree of lordosis. A straight hypo-lordotic spine shows stresses more equally distributed among discs while a highly curved hyper-lordotic spine has stresses concentrated at lower discs. Stresses are uniformly distributed in each disc for Hypo-L case while they are concentrated posteriorly for Hyper-L case. Also, the maximum force in collagen fibers is developed in the Hyper-L case. These differences might be clinically significant related to back pain.

4D Mitral Valve Motion Analysis Using Multi-Plane Cine Cardiac MRI Reconstructions for Functional Classification of Patients With Mitral Regurgitation

Mitral regurgitation (MR) is a common consequence of ventricular remodeling in heart failure (HF) patients with systolic dysfunction and is associated with diminished survival rates. Characterization of patient-specific anatomy and function of the regurgitant mitral valve (MV) can enhance surgical decision making in terms of medical device choice and deployment strategy for minimally invasive endovascular approaches for MV repair. As a first step toward pre-operative planning for MV repair, we examine the feasibility of using cardiac magnetic resonance (CMR) images acquired in multiple orientations to resolve leaflet function and timing. In this study, MV motion of a HF patient with ischemic heart disease exhibiting both adverse ventricular remodeling and MR was compared pre-operatively against a normal control from the Sunnybrook cardiac database, starting with manually segmented 2D MV contours from cine CMR images acquired in multiple orientations. We find that MV motion analysis from CMR imaging is feasible and anatomical reconstruction using oriented segmentations from a combination of imaging slices acquired in multiple orientations can help overcome inherent limitations of CMR image data in terms of resolving small anatomical features, owing to finite slice-thicknesses and partial volume effects.

System for Assistance on Bath of Bedridden Elderly People

From Ambient Assisted Living (AAL) perspective it is important to have information regarding the type of care needed by bedridden elderly people (BEP) living in their homes, in order to support independence, autonomy and maximize their quality of life. Some basic tasks as eating, taking a bath and the hygiene cares may be difficult to execute, regarding that almost always the main caregiver is the other element of the couple (husband or wife). Following this trend, the development of mechatronic devices is of upmost importance in creating solutions to facilitate these tasks. This paper presents the conceptual design of a mechatronic system especially devoted to the assistance during the bath of BEP. Issues as reducing the number of caregivers to only one to assist the bath and reducing the system’s handling complexity (because most of the time it will be used by an aged person) are considered. Visits to rehabilitation centers and hospitals, and respective working meetings, are considered in the development of the proposed mechatronic system.

Study on Detection of Epileptic Discharges Based on a Duffing Oscillator Model

In order to establish a quantitative detection method for appearance in epileptic discharges (EDs), we propose using the model parameters in a Duffing oscillator, which is a nonlinear mathematical model. Extracting four frequency bands of delta, theta, alpha and beta waves from the time history of the electrocorticogram (ECoG) obtained from rats with induced EDs, we applied a sweep window to the time history for each band. So as to fit the equation for the Duffing oscillator to the time history of the ECoG, we used the least square method to determine the model parameters expressing characteristics of ECoG. The Duffing oscillator has three kinds of vibrational parameters and four kinds of parameters about the amplitude for the driving force with two predominant frequencies contained in ECoG. In order to examine the appearance time of the EDs and the change of ECoG characteristics, we determined the model parameters for each sweep window. When epilepsy occurs, we found that the amount of the parameters related to “conservation”, “dissipation” and “input quantities” increases. On the other hand, the parameter value corresponding to nonlinearity tends to decrease. It is found that the proposed method by the model parameters of the Duffing oscillator can be used in quantitative detection for EDs.

A Bi-Frequency Co-Linear Array Transducer for Biomedical Ultrasound Imaging

Ultrasound imaging with high resolution and large field of depth has been increasingly adopted in medical diagnosis, surgery guidance and treatment assessment because of its relatively low cost, non-invasive and capability of real-time imaging. There is always a tradeoff between the resolution and depth of field in ultrasound imaging. Conventional ultrasound works at a particular frequency, with −6 dB fractional bandwidth of < 100%, limiting the resolution or field of depth in many ultrasound imaging cases. In this paper, a bi-frequency co-linear array covering a frequency range of 5 MHz-20 MHz was investigated to meet the requirements of resolution and depth of field for a broad range of ultrasound imaging applications. As a demonstration, a 31-element bi-frequency co-linear array was designed and fabricated, followed by element characterization and real time sectorial scan (S-scan) phantom imaging using a Verasonics system.

Joint Loading Effect on Kinematics of the Natural Knee During a Range of Simulated Walking Profiles

The physiological ratio of compression to anterior-posterior (A-P) knee joint loads has substantial effects on the loading of soft tissue structures, patellofemoral loads, and knee kinematics [1, 2]. There is also a direct relationship between resultant kinematics and joint forces. D’lima et al. was also able to compute A-P kinematics at a given flexion angle with minimal error using measured A-P and compressive load acquired from the instrumented tibia [3]. The direction of A-P load measured at the tibia is associated with the direction of translations of the femur relative to the tibia.