scholarly journals Biomechanics of Sports-Induced Axial-Compression Injuries of the Neck

2012 ◽  
Vol 47 (5) ◽  
pp. 489-497 ◽  
Author(s):  
Paul C. Ivancic
Keyword(s):  
Axial Compression ◽  
Time History ◽  
Occipital Condyle ◽  
Neck Injuries ◽  
Compression Force ◽  
Cervical Fractures ◽  
Human Cadavers ◽  
Clinical Awareness ◽  
Occipital Condyles ◽  
The Impact

ContextHead-first sports-induced impacts cause cervical fractures and dislocations and spinal cord lesions. In previous biomechanical studies, researchers have vertically dropped human cadavers, head-neck specimens, or surrogate models in inverted postures.ObjectiveTo develop a cadaveric neck model to simulate horizontally aligned, head-first impacts with a straightened neck and to use the model to investigate biomechanical responses and failure mechanisms.DesignDescriptive laboratory study.SettingBiomechanics research laboratory.Patients or Other ParticipantsFive human cadaveric cervical spine specimens.Intervention(s)The model consisted of the neck specimen mounted horizontally to a torso-equivalent mass on a sled and carrying a surrogate head. Head-first impacts were simulated at 4.1 m/s into a padded, deformable barrier.Main Outcome Measure(s)Time-history responses were determined for head and neck loads, accelerations, and motions. Average occurrence times of the compression force peaks at the impact barrier, occipital condyles, and neck were compared.ResultsThe first local compression force peaks at the impact barrier (3070.0 ± 168.0 N at 18.8 milliseconds), occipital condyles (2868.1 ± 732.4 N at 19.6 milliseconds), and neck (2884.6 ± 910.7 N at 25.0 milliseconds) occurred earlier than all global compression peaks, which reached 7531.6 N in the neck at 46.6 milliseconds (P < .001). Average peak head motions relative to the torso were 6.0 cm in compression, 2.4 cm in posterior shear, and 6.4° in flexion. Neck compression fractures included occipital condyle, atlas, odontoid, and subaxial comminuted burst and facet fractures.ConclusionsNeck injuries due to excessive axial compression occurred within 20 milliseconds of impact and were caused by abrupt deceleration of the head and continued forward torso momentum before simultaneous rebound of the head and torso. Improved understanding of neck injury mechanisms during sports-induced impacts will increase clinical awareness and immediate care and ultimately lead to improved protective equipment, reducing the frequency and severity of neck injuries and their associated societal costs.

scholarly journals Anatomical Parameters for Occipital Condyle Screws: An Analysis of 500 Condyles Using CT Scans

2021 ◽  
pp. 219256822098331
Author(s):  
David N. Bernstein ◽  
Tochukwu C. Ikpeze ◽  
Kenneth Foxx ◽  
Adan Omar ◽  
Addisu Mesfin
Keyword(s):  
Clinical Care ◽  
Ct Imaging ◽  
Occipital Condyle ◽  
Neoplastic Disease ◽  
Optimal Outcomes ◽  
Occipitocervical Fixation ◽  
Cervical Fractures ◽  
Length Width ◽  
Occipital Condyles ◽  
Anatomical Parameters

Study Design: Retrospective observational study. Objective: To establish occipital condyle dimensions (length, width, height), as well as the medialization angle necessary for safe occipital condyle screw placement in occipitocervical fixation. Methods: Between 1/2014-6/2014, patients who presented to a single level 1 academic trauma center emergency room and received computed tomography (CT) imaging of the cervical spine as part of routine clinical care were identified. After excluding patients with cervical fractures, neoplastic disease, or infection, 500 condyles representing 250 patients were analyzed. Condyle length, height, and width (all reported in millimeters [mm]) were evaluated on the sagittal, coronal, and axial series, respectively. Medialization angle (reported in degrees) was evaluated on the axial series of CT imaging. Measurements were compared by sex and age. Results: The average condyle length, width, and height were 18.6 millimeters (mm) (range, 14.5-23.0 mm), 10.5 mm (range, 7.4-13.8 mm), and 11.3 mm (7.1-15.3 mm), respectively. Additionally, the average occipital condyle medialization angle was 23° (range, 14-32°). Occipital condyles of men were significantly longer, wider, and taller (all comparisons, p < 0.05). The medialization angle was significantly steeper for women than men (p < 0.05). No measurement differences were appreciated by age. Conclusion: Our findings are similar to previous studies in the field; however, length appears slightly shorter. Further, measurement differences were appreciated by sex but not age. Thus, our measurement findings emphasize the importance of preoperative planning utilizing individual patient anatomy to ensure safe placement of occipital condyle screws for optimal outcomes.

scholarly journals Seismic Performance of a Green Roof Structure

2021 ◽  
Vol 13 (8) ◽  
pp. 4278
Author(s):  
Svetlana Tam ◽  
Jenna Wong
Keyword(s):  
Green Roof ◽  
Time History ◽  
Green Roofs ◽  
Moment Frame ◽  
Steel Moment Frame ◽  
Roof Structure ◽  
Nonlinear Time History Analyses ◽  
Vegetated Roofs ◽  
Nonlinear Time History ◽  
The Impact

Sustainability addresses the need to reduce the structure’s impact on the environment but does not reduce the environment’s impact on the structure. To explore this relationship, this study focuses on quantifying the impact of green roofs or vegetated roofs on seismic responses such as story displacements, interstory drifts, and floor level accelerations. Using an archetype three-story steel moment frame, nonlinear time history analyses are conducted in OpenSees for a shallow and deep green roof using a suite of ground motions from various distances from the fault to identify key trends and sensitivities in response.

scholarly journals Detonation effects of shallow buried explosive in sandy soil on target plate acceleration in a small-scale blast test

2018 ◽  
Vol 192 ◽  
pp. 02028
Author(s):  
Hassan Zulkifli Abu ◽  
Ibrahim Aniza ◽  
Mohamad Nor Norazman
Keyword(s):  
Sandy Soil ◽  
High Speed ◽  
Early Stage ◽  
Time History ◽  
Video Camera ◽  
Small Scale ◽  
Target Plate ◽  
Air Blast ◽  
High Speed Video Camera ◽  
The Impact

Small-scale blast tests were carried out to observe and measure the influence of sandy soil towards explosive blast intensity. The tests were to simulate blast impact imparted by anti-vehicular landmine to a lightweight armoured vehicle (LAV). Time of occurrence of the three phases of detonation phase in soil with respect to upward translation time of the test apparatus were recorded using high-speed video camera. At the same time the target plate acceleration was measured using shock accelerometer. It was observed that target plate deformation took place at early stage of the detonation phase before the apparatus moved vertically upwards. Previous data of acceleration-time history and velocity-time history from air blast detonation were compared. It was observed that effects of soil funnelling on blast wave together with the impact from soil ejecta may have contributed to higher blast intensity that characterized detonation in soil, where detonation in soil demonstrated higher plate velocity compared to what occurred in air blast detonation.

Modelling of Convective Melt Flow and Interface Shape in Commercial Bridgman-Stockbarger Growth of CdZnTe

2000 ◽  
Author(s):  
Toby D. Rule ◽  
Ben Q. Li ◽  
Kelvin G. Lynn
Keyword(s):  
Heat Transfer ◽  
Thermal Stress ◽  
Solute Transport ◽  
Latent Heat ◽  
Thermal Stresses ◽  
Radiation Detector ◽  
Time History ◽  
High Quality ◽  
Melt Convection ◽  
The Impact

Abstract CdZnTe single crystals for radiation detector and IR substrate applications must be of high quality and controlled purity. The growth of such crystals from a melt is very difficult due to the low thermal conductivity and high latent heat of the material, and the ease with which dislocations, twins and precipitates are introduced during crystal growth. These defects may be related to solute transport phenomena and thermal stresses associated with the solidification process. As a result, production of high quality material requires excellent thermal control during the entire growth process. A comprehensive model is being developed to account for radiation and conduction within the furnace, thermal coupling between the furnace and growth crucible, and finally the thermal stress fields within the growing crystal which result from the thermal conditions imposed on the crucible. As part of this effort, the present work examines the heat transfer and fluid flow within the crucible, using thermal boundary conditions obtained from experimental measurements. The 2-D axisymetric numerical model uses the deforming finite element method, with allowance made for melt convection, solidification with latent heat release and conjugate heat transfer between the solid material and the melt. Results are presented for several stages of growth, including a time-history of the solid-liquid interface (1365 K isotherm). The impact of melt convection, thermal end conditions and furnace temperature gradient on the growth interface is evaluated. Future work will extend the present model to include radiation exchange within the furnace, and a transient analysis for studying solute transport and thermal stress.

scholarly journals Markovian inhomogeneous closures for Rossby waves and turbulence over topography

2018 ◽  
Vol 858 ◽  
pp. 45-70
Author(s):  
Jorgen S. Frederiksen ◽  
Terence J. O’Kane
Keyword(s):  
Turbulent Flows ◽  
Rossby Waves ◽  
Time History ◽  
Direct Interaction ◽  
Mean Flow ◽  
Current Time ◽  
Fluctuation Dissipation ◽  
Large Ensembles ◽  
Direct Interaction Approximation ◽  
The Impact

Manifestly Markovian closures for the interaction of two-dimensional inhomogeneous turbulent flows with Rossby waves and topography are formulated and compared with large ensembles of direct numerical simulations (DNS) on a generalized $\unicode[STIX]{x1D6FD}$-plane. Three versions of the Markovian inhomogeneous closure (MIC) are established from the quasi-diagonal direct interaction approximation (QDIA) theory by modifying the response function to a Markovian form and employing respectively the current-time (quasi-stationary) fluctuation dissipation theorem (FDT), the prior-time (non-stationary) FDT and the correlation FDT. Markov equations for the triad relaxation functions are derived that carry similar information to the time-history integrals of the non-Markovian QDIA closure but become relatively more efficient for long integrations. Far from equilibrium processes are studied, where the impact of a westerly mean flow on a conical mountain generates large-amplitude Rossby waves in a turbulent environment, over a period of 10 days. Excellent agreement between the evolved mean streamfunction and mean and transient kinetic energy spectra are found for the three versions of the MIC and two variants of the non-Markovian QDIA compared with an ensemble of 1800 DNS. In all cases mean Rossby wavetrain pattern correlations between the closures and the DNS ensemble are greater than 0.9998.

scholarly journals Analysis of the Impact on Axial Compression and Diametric tensile strength of concrete using recycled fine aggregate

2021 ◽  
Vol 8 (7) ◽  
pp. 155-163
Author(s):  
Eduardo Dalla Costa Silva ◽  
Dykenlove Marcelin ◽  
Douglas Guedes Batista Torres ◽  
Thiago Guerra
Keyword(s):  
Tensile Strength ◽  
Axial Compression ◽  
Fine Aggregate ◽  
Recycled Fine Aggregate ◽  
The Impact

Novel Hanger Design to Improve the Robustness of Through Arch Bridges

2011 ◽  
Vol 90-93 ◽  
pp. 862-868
Author(s):  
Qi Ming Wu ◽  
Dang Qi Yang ◽  
Fei Cui ◽  
Xiao Wei Yi ◽  
Rui Juan Jiang
Keyword(s):  
Progressive Collapse ◽  
Time History ◽  
Structural Members ◽  
New Approach ◽  
Arch Bridge ◽  
Structural Robustness ◽  
Arch Bridges ◽  
Dynamic Time ◽  
The Impact ◽  
Emergency Measures

Hangers in through arch bridges are important components since they suspend the bridge deck from the arch ribs. Local damage at a hanger may lead to progressive damage of various components in the arch bridge or even progressive collapse of the bridge. In this paper, the conventional design of double-hangers in through arch bridges is reviewed. Then a new approach to design the double-hangers is put forward. The suitability and robustness of this approach is then verified by a numerical simulation of a real through arch bridge. The impact effects induced by local hanger fracture on other structural members are simulated by dynamic time-history analyses. The new approach to design the hangers for through arch bridges is shown to improve the structural robustness. With the application of the new way put forward here, when one or more hangers are damaged to fail, the through arch bridge will not be endangered and will still maintain the overall load-bearing capacity during an appropriate length of time to allow necessary emergency measures to be taken, which illustrates the leading principle of structural robustness well.

scholarly journals Dynamic Characteristics of Deep Dolomite Under One-Dimensional Static and Dynamic Loads

2019 ◽  
Vol 101 (1) ◽  
pp. 49-56 ◽  
Author(s):  
Jianguo Wang ◽  
Yang Liu ◽  
Kegang Li
Keyword(s):  
Strain Rate ◽  
Axial Compression ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Strength ◽  
Strong Positive Correlation ◽  
Hopkinson Pressure Bar ◽  
Irreversible Damage ◽  
One Dimensional ◽  
Rock Structure ◽  
The Impact

AbstractThe failure characteristics of rock subjected to impact disturbance under one-dimensional static axial compression are helpful for studying the problems of pillar instability and rock burst in deep, high geostress surrounding rock under blasting disturbances. Improved split Hopkinson pressure bar equipment was used for one-dimensional dynamic–static combined impact tests of deep-seated dolomite specimens under axial compression levels of 0, 12, 24, and 36 MPa. The experimental results demonstrate that the dolomite specimens exhibit strong brittleness. The dynamic strength always maintains a strong positive correlation with the strain rate when the axial compression is fixed; when the strain rate is close, the dynamic elasticity modulus and peak strength of the specimens first increase and then decrease with the increase in axial compression, and the peak value appears at 24 MPa. The impact resistance of specimens can be enhanced when the axial compression is 12 or 24 MPa, but when it increases to 36 MPa, the damage inside the specimen begins to cause damage to the dynamic rock strength. Prior to the rock macroscopic failure, the axial static load changes the rock structure state, and it can store strain energy or cause irreversible damage.

scholarly journals Study on the Impact Resistance of Metal Flexible Net to Rock fall

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Gaosheng Wang ◽  
Yunhou Sun ◽  
Ao Zhang ◽  
Lei Zheng ◽  
Yuzheng Lv ◽  
...  
Keyword(s):  
Finite Element ◽  
Impact Force ◽  
Impact Resistance ◽  
Time History ◽  
Rock Fall ◽  
Fe Model ◽  
Element Analysis ◽  
Inclination Angles ◽  
Fall Protection ◽  
The Impact

Based on experiments and finite element analysis, the impact resistance of metal flexible net was studied, which can provide reference for the application of metal flexible net in rock fall protection. The oblique (30 degrees) impact experiment of metal flexible net was carried out, the corresponding finite element (FE) to the experiment was established, and the FE model was verified by simulation results to the experimental tests from three aspects: the deformation characteristics of metal flexible net, the time history curves of impact force on supporting ropes, and the maximum instantaneous impact force on supporting ropes. The FE models of metal flexible nets with inclination angles of 0, 15, 30, 45, 60, and 75 degrees were established, and the impact resistance of metal flexible nets with different inclination angles was analyzed. The research shows that the metal flexible net with proper inclination can bounce the impact rock fall out of the safe area and prevent rock fall falling on the metal flexible net, thus realizing the self-cleaning function. When the inclination angle of the metal flexible net is 15, 30, and 45 degrees, respectively, the bounce effect after impact is better, the remaining height is improved, the protection width is improved obviously, and the impact force is reduced. Herein, the impact force of rock fall decreases most obviously at 45 degrees inclination, and the protective performance is relatively good.

Predictive Equations to Quantify the Impact of Spectral Matching on Ground Motion Characteristics

2016 ◽  
Vol 32 (1) ◽  
pp. 125-142 ◽  
Author(s):  
Clinton Carlson ◽  
Dimitrios Zekkos ◽  
Adda Athanasopoulos-Zekkos
Keyword(s):  
Ground Motion ◽  
Response Spectrum ◽  
Time History ◽  
Peak Ground Velocity ◽  
Spectral Matching ◽  
Predictive Equations ◽  
Earthquake Scenarios ◽  
Cumulative Absolute Velocity ◽  
Motion Characteristics ◽  
The Impact

Spectral matching, the process of modifying a seed acceleration time history in intensity and frequency content until its acceleration response spectrum matches a target spectrum, is used extensively in practice. Predictive equations that quantify the impact of spectral matching on the peak ground velocity, peak ground displacement, Arias intensity, and cumulative absolute velocity of a scaled seed time history have been developed and validated on the basis of thousands of matched motions, three different earthquake scenarios, and numerous target spectra. It is found that spectral mismatch is the most critical factor affecting the changes in ground motion characteristics. The technique used for modification (e.g., time domain or frequency domain) is in many cases not critical. Based on the results, recommendations in order to minimize the impact of matching on the ground motion characteristics are provided.

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