bluuebunny/crossref_metadata_2025 huggingface dataset:
A Parametric Investigation of Integrated Gasification Combined Cycles With Carbon Capture
Authors: Li Xuewei , Wang Ting
Published: July 2013

IGCC (Integrated Gasification Combined Cycle) technology is being developed to enable electricity to be generated at high efficiency and low emissions. Continuous improvement is essential to make IGCC reliable and cost-effective. As environmental concerns over carbon emissions escalate, development of a practical carbon capture and storage (CCS) technology has become an important issue. Combining IGCC and CCS has become a promising technology to reduce the cost of CCS. This study investigates the pros and cons of different methods used to put together an approximately 250 MW IGCC plant with and without CCS by using the commercial software Thermoflow. Seven different IGCC plants have been designed with various parameters examined, including: oxygen-blown vs. air-blown, with/without integration, with/without CCS, sour vs. sweet water shift for carbon capture, and dry- vs. slurry-fed. This study is based on technologies that are commercially available or close to commercialization. The results show that:

(a) integration between the gas turbine and the air separation unit (ASU) can boost the cycle efficiency about 4.5% (1.6 percentage points);

(b) dry-feeding increases the CO content, the syngas heating value (19%), and the efficiency about 11% (4.7 percentage points);

(c) carbon capture reduces the power output by 2.7% and efficiency by 10% (or 4.5 percentage points) and the slurry-fed system takes a heavier toll on power output and efficiency than the dry-fed system;

(d) air-blown systems do away with the ASU, resulting in syngas with a 50% lower heating value and a small reduction in efficiency, but harvesting savings on reduced capital, operating, and maintenance costs;

(e) for CO2, sweet water shift results in 5.5% (2 percentage points) higher cycle efficiency than sour shift.
Design of an Economical Counter Rotating Fan: Comparison of the Calculated and Measured Steady and Unsteady Results
Authors: Lengyel-Kampmann Timea , Bischoff Andreas , Meyer Robert , Nicke Eberhard
Published: July 2013

Within the framework of the EU funded Project VITAL, SNECMA (Group Safran), as the work package leader, developed a counter rotating low-speed fan-concept for a high bypass ratio engine. The detailed aerodynamic and mechanical optimization of one blading version (CRTF2.b) was carried out at the German Aerospace Center (DLR), by applying one of the newest design methods featuring a multi-objective automatic optimization method based on an Evolutionary Algorithm [1].

The final design goals were high efficiency, a sufficient stall margin and adequate acoustic performances for the given cycle parameters. The fan stage developed was tested in an anechoic test facility at CIAM in Moscow. The test routine included the measurement of the performance map based on total pressure and total temperature measurements at the inlet and the outlet of the test rig and acoustic measurement as well.

The unsteady flow field of the low speed Contra-Rotating Turbo Fan has been measured with four hot-wire probes at different axial positions.

In the evaluation the measured data are compared with high resolution CFD results. Special emphasis was given to the comparison of the radial distribution of total pressure and total temperature in the bypass channel, the comparison of the measured and the calculated fan maps and to the comparison of the hot-wire measurements with high resolution, unsteady CFD results. The tests and the URANS-results confirmed the design goals.
Jet-Surface Interaction Test: Far-Field Noise Results
Authors: Brown Clifford
Published: July 2013

Many configurations proposed for the next generation of aircraft rely on the wing or other aircraft surfaces to shield the engine noise from the observers on the ground. However, the ability to predict the shielding effect and any new noise sources that arise from the high-speed jet flow interacting with a hard surface is currently limited. Furthermore, quality experimental data from jets with surfaces nearby suitable for developing and validating noise prediction methods are usually tied to a particular vehicle concept and, therefore, very complicated. The Jet/Surface Interaction Test was intended to supply a high quality set of data covering a wide range of surface geometries and positions and jet flows to researchers developing aircraft noise prediction tools. During phase one, the goal was to measure the noise of a jet near a simple planar surface while varying the surface length and location in order to: (1) validate noise prediction schemes when the surface is acting only as a jet noise shield and when the jet/surface interaction is creating additional noise, and (2) determine regions of interest for more detailed tests in phase two. To meet these phase one objectives, a flat plate was mounted on a two-axis traverse in two distinct configurations: (1) as a shield between the jet and the observer (microphone array) and (2) as a reflecting surface on the opposite side of the jet from the observer. The surface was moved through axial positions 2 ≤ xTE/Dj ≤ 20 (measured at the surface trailing edge, xTE, and normalized by the jet diameter, Dj) and radial positions 1 ≤ h/Dj ≤ 20. Far-field and phased array noise data were acquired at each combination of axial and radial surface location using two nozzles and at 8 different jet exit conditions across several flow regimes (subsonic cold, subsonic hot, underexpanded, ideally expanded, and overexpanded supersonic cold). The far-field noise results, discussed here, show where the surface shields some of the jet noise and, depending on the location of the surface and the observer, where scrubbing and trailing edge noise sources are created as a surface extends downstream and approaches the jet plume.
Evaluation of the Impact of Alternative Fuel Use on the Emissions and Performance of a Service-Exposed T56 Engine
Authors: Chalmers Jennifer L. Y. , Davison Craig R. , Chishty Wajid Ali , Bird Jeff W. , Chan Tak , Barton Peter , Dagenais Rod , Pham Vinh , Poitras Pierre
Published: July 2013

Alternative fuel sources are becoming an operational reality; these fuels have the potential to reduce emissions, improve combustion characteristics and to increase fuel supply security. A test with a T56 turboprop engine was performed to demonstrate that a CHEFA/JP8 (Camelina Hydroprocessed Ester and Fatty Acids and standard JP8) fuel blend would meet operational requirements. The primary test objective was to assess whether a fuel change had an immediate impact on the engine condition, performance, emissions or vibration characteristics. This paper presents test results comparing engine performance with JP8 and a 50/50 blend of JP8 and CHEFA. Comparison runs were conducted before and after a 20 hour ground durability test with the CHEFA fuel blend. A nearly time-expired, nacelle-dressed T56 on an outdoor test stand was tested. The engine was equipped with minimally-intrusive non-standard pressure, temperature and emissions monitoring equipment, and a field vibration assessment suite in addition to the standard flight instrumentation. This paper discusses the test plan, data acquisition methods, results and data repeatability. The performance and emissions results are compared to the changes predicted theoretically from the fuel properties. Observations from the borescope inspections before, during and after the 20 hour durability test are also presented. The lessons learned in this test could be applied to future fuel or process-change tests, and the results provide a performance baseline for engine health assessment.
Simulation of the Laminar Flow in a PRIMIX Static Mixer
Authors: Mudde R. F. , Van Pijpen C. , Beugels R.
Published: July 2013

The PRIMIX helical static mixer has been investigated using numerical simulations. The flow is in the laminar regime (Re = 1 to 1000). The simulations concentrate on the pressure drop and on the use of particle tracking for mixing studies. For the pressure drop, experimental validation is provided. It is found that the pressure drop can be simulated with high accuracy for Re < 350. For higher Re-values no grid independent solution could be obtained and the experimental results no longer agree with those of the simulations. The simulated pressure drop results scaled to the empty pipe pressure drop, can be well summarized as K = 4.99 + Re/31.4. Using Particle Tracking it has been possible to reproduce literature data. However, it has been shown that the obtained results are rather sensitive to the choice of the time step. This limits the direct use of particle tracking techniques for studying the mixing of static mixers in the laminar regime.
Tubular Structure Deformation Under the Thermal Loads of Two Fluids
Authors: Suresh Krishnamurty , Dagba Yves , Tripathi Amita
Published: July 2013

The fluid/structure/thermal interaction as performed in the commercial code fluidyn-CHT consists of coupling the finite volume approach for fluids to the finite element method for structures inside the same solver. Meshes for the two media are independent and boundary conditions are exchanged iteratively until convergence. Thus, the complex response of combined fluid and solid media is solved efficiently. As a typical industrial test case, a thick steel pipe presenting a 90° elbow is modelled. Initially the fluid in the pipe is at a temperature of 423 K and at 157 bar of pressure. At the inlet, two streams enter the pipe at 423 K and 523 K respectively. The fluids start to mix after the elbow. As a consequence, the thermal load exerted on the structure result in a deformation of the structure at the elbow. This deformation could end up in a catastrophic failure.
Effects on Prandtl Number and Transpiration Parameter on a Certain MHD Free Convection Flow With Visco-Elastic Fluid Along an Infinite Vertical Porous Plate
Authors: Islam M. N.
Published: July 2013

The effect of prandtl number and transpiration parameter variable viscosity on a MHD free convection flow with visco-elastic fluid along an infinite vertical porous plate. The governing partial differential equations have been solved numerically using Local non-similarity method. An analysis is presented to study the effect of prandtl number and transpiration parameter result for the zero order perturbation velocity profile, the first order perturbation velocity and temperature profiles.
Modeling the Airflow Around Cooling Towers With Multi-Block CFD
Authors: Zhai Zhiqiang , Fu Song
Published: July 2013

This paper describes the development of a multi-block, structured grid system in a computational fluid dynamics (CFD) program, instead of the conventional single-block, structured grid system, to study the flow and heat transfer in complex geometries. The study used experimental data from a three-dimensional, cube-channel turbulent flow to validate the multi-block CFD program. Then the program was used to study the influence of wind on the dry cooling tower performance. By dividing the whole computational domain into five blocks, this investigation successfully modeled the airflow and heat transfer in and around two in-line cooling towers under a wind speed of 10 m/s. The computational results show that the crosswind has a significant adverse influence on the performance of dry cooling towers.
Numerical Calculations of Wing Tip Vortices and Effects of Suction at Wing Tip
Authors: Okada S. , Arai N. , Hiraoka K.
Published: July 2013

In three-dimensional wing, the induced drag occurs by wing tip vortices. So it is important to study the characteristics of wing tip vortices in order to reduce the induced drag. In this paper, at first comparing the numerically calculated results of three-dimensional incompressible flow using several turbulence models and the law speed wind tunnel experimental results using a two-dimensional hot wire anemometer, the characteristics of wing tip vortices are studied. In the numerical calculations, the multipurpose fluid analysis software FLUENT and the pre-processor GAMBIT are used on popular PC. The numerical results that were obtained by using the RNG k-ε turbulence model is good agreement with the experimental results. Then controlling the flow near the wing tip by suction, the effects against wing tip vortices are studied by numerically and experimentally. It is shown by numerical calculation and experiment that the strength of wing tip vortices decrease by appropriate suction at the wing tip.
Numerical Simulation of Asymmetric Exhaust Flows Using an Actuator Disc Blade Row Model
Authors: Liu Jianjun
Published: July 2013

This paper describes the numerical simulation of the asymmetric exhaust flows by using a 3D viscous flow solver incorporating an actuator disc blade row model. The three dimensional Reynolds-Averaged Navier-Stokes equations are solved by using the TVD Lax-Wendroff scheme. The convergence to a steady state is speeded up by using the V-cycle multigrid algorithm. Turbulence eddy viscosity is estimated by the Baldwin-Lomax model. Multiblock method is applied to cope with the complicated physical domains. Actuator disc model is used to represent a turbine blade row and to achieve the required flow turning and entropy rise across the blade row. The solution procedure and the actuator disc boundary conditions are described. The stream traces in various sections of the exhaust hood are presented to demonstrate the complicity of the flow patterns existing in the exhaust hood.
Semi-Empirical Approach to Predicting Temperatures of a Non-Opaque Surface
Authors: Bush Bob , Li Shu
Published: July 2013

The methods used in predicting the thermal profile of a high-pressure mercury arc lamp housed in an electronics enclosure are discussed. These types of enclosures are typically operated in harsh environments. High temperature and low pressure air is typically used to cool the electronics inside. A lamp, which dissipates roughly one half of the total power within the box, must be cooled sufficiently so as to not affect the performance of the circuit cards. Since the majority of the heat being transferred from the lamp’s center arc tube to its surrounding atmosphere (to the lamp housing and then to the circuit cards inside the electronics box) is via radiation, a Computational Fluid Dynamics (CFD) code with a radiation solver was essential to drive the design. Fluent Icepak was chosen as a capable code for electronic box type problems. However, lcepak does not account for radiative transfer through non-opaque surfaces. Since the lamp housing is very transmissive in the infrared at certain wavelengths, the energy equations could not be solved using only analytical techniques. Therefore, tests were conducted that first characterized the thermal performance of the lamp and then predicted the energy that was conducted and absorbed by the glass housing (made up of a reflector and front cover). The remaining power was then assumed to be transmissive in nature. In the computational model, powers were iteratively applied to various locations on the lamp housing until the model matched the empirical results. Once the lamp model was characterized, it could be used to drive the design of any type of enclosure in any type of environment.
A Technique for Developing a Precise Thermal Compact Model
Authors: Okamoto Keishi , Koyamada Kohji , Kuzuno Masanori , Nishio Toshihiko , Kotera Hidetoshi
Published: July 2013

In this paper, we propose a technique to select an appropriate convergence criterion for developing precise thermal compact model. It is known that the compact modeling in thermal simulation can reduce the computing cost for a system level of thermal simulation. We have used the Response Surface Methodology (RSM) to identify parameters of the compact model. However the resulting RSM model is not accurate enough, because the fitness function in thermal simulation has many peak points. We find that this is due to the insufficient convergence of thermal simulation, by investigating temperature results in thermal simulation with the change in thermal conductivities. To solve this problem caused by the insufficient convergence, we optimize the convergence criteria of temperature.
Quantification of Abdominal Aortic Aneurysm Disease Progression Using Small Animal Magnetic Resonance Imaging
Authors: Barr Kyla N. , Goergen Craig J. , Hedehus Maj , Azuma Junya , Taylor Charles A. , Tsao Philip S. , Greve Joan M.
Published: July 2013

Abdominal aortic aneurysm (AAA) disease, defined as a pathological dilation of the vessel wall, is responsible for 15,000 deaths per year in the United States. Human AAA are often asymmetric, typically expanding anteriorly as the posterior region is supported by the vertebral column [1]. Other work has shown that healthy thoracic aortic motion is also asymmetric in pigs and humans [2]. Two commonly used murine models induce AAA growth with either the infusion of angiotensin II (angII) [3] or intra-arterial perfusion of porcine pancreatic elastase (PPE) into the aortic lumen [4]. The purpose of this study was to determine the relationship between vessel motion, circumferential cyclic strain, and aneurysm growth in two different murine models of AAA disease using small animal magnetic resonance imaging (MRI).
Lumbar Spine Capsule Strain After Total Disc Replacement
Authors: Takigawa Tomoyuki , Espinoza Orías Alejandro A. , An Howard S. , Simon Peter , Sugisaki Keizo , Natarajan Raghu N. , Wimmer Markus A. , Andersson Gunnar B. J. , Inoue Nozomu
Published: July 2013

Degenerative disc disease is a common cause for low back pain, and sometimes requires surgical treatment. Total disc replacement (TDR) is one such surgical option performed to remove the painful disc and preserve segmental motion. However, TDR clinical results are not always satisfactory. Altered kinematics and residual low back pain have been reported as frequent poor outcomes. The facet joint is a pure articular joint and can be a pain generator. Although the effect of TDR on ROMs (ranges of motion) and facet contact force is relatively well studied, the influence of TDR on facet capsules has not been clarified yet. The purpose of this study was to evaluate the effect of TDR on facet joint capsule strain.
Effect of Annular Micro Tear on Lumbar Intervertebral Disc Biomechanics
Authors: Natarajan Raghu N. , Qasim Mohammed , An Howard , Andersson Gunnar B. J.
Published: July 2013

Structural alterations of the disc are accompanied by changes in disc tissue structure and composition during degeneration processes. Human cadaver studies have shown that the probability of presence of annular tear is 0.6 in the age group 30 to 34 which increases to 0.85 in the 60 year age group. Among different phenomena that occur during disc degeneration, annular radial tears are commonly associated with disc herniations. The effect of increase in size of radial micro tear in the lumbar discs on the change in biomechanics of the disc is an area where there is very little information currently in the literature.
Measurement of Pulmonary Impedance in Live Mice and Changes With Chronic Hypoxia
Authors: Tabima Diana M. , Vanderpool Rebecca , Hacker Timothy A. , Chesler Naomi C.
Published: July 2013

Pulmonary arterial impedance offers the most complete characterization of right ventricular afterload, which is crucial for the proper function of the right ventricle. Impedance can be calculated in either the time or frequency domain from pulsatile pressure-flow relationships. Here we compared impedance metrics calculated in the time domain to those computed in the frequency domain under normal conditions and after induction of hypoxic pulmonary hypertension (HPH) (10 and 21 days). In C57BL6/J mice, pulmonary arterial pressure was measured invasively with a high fidelity catheter while pulmonary arterial flow was measured with Doppler ultrasound. Input impedance (Z0) and characteristic impedance (ZC) were calculated from the resulting pressure-flow relationships. Our results demonstrate that Z0 increased with 10 days of hypoxia as expected but surprisingly returned toward normal after 21 days; the values obtained were not different for the two methods (R2 = 0.99, P <0.0001). ZC increased slightly but not significantly with 10 days of hypoxia and remained at control levels after a 21 day exposure; here the values did depend on the method used: ZC was 1.73 times larger when calculated in the frequency domain versus the time domain (R2 = 0.86, P <0.0001). We conclude that both time and frequency domain analyses can be used to calculate important metrics of pulmonary vascular impedance, which lend insight into the changes in arterial structure and function that occur with pulmonary vascular disease.
Skin Movement for Individuals With ACL-Deficient and ACL-Reconstructed Knees
Authors: Wang Hongsheng , Zheng Naiquan Nigel
Published: July 2013

The anterior cruciate ligament reconstructed (ACL-R) knees suffer from a higher risk for osteoarthritis (OA) which is the major leading cause of disability[1]. In order to understand the mechanism of knee injury and the development of OA, precise 3-D knee joint motion is often determined by invasive, or radioactive approaches[2]. For studying daily activities like walking which has larger range of motion (ROM), the skin marker-based technique remains the only feasible way[3].
A Bamboo Wheelchair for Disabled Zambians: Phase 1—Design and Material Selection
Authors: Gilbreath Kyle B. , Nelson Jacob A. , Oliver Tina G. , Eberhardt Alan W.
Published: July 2013

In the country of Zambia, located in southeast Africa, roughly 80% of the population lives off of less than 1 USD per day (Shaoul, 2002). There is little basic healthcare and the area is particularly disease-ridden. HIV is prevalent and various forms of infections are complicated by insufficient means to properly care for wounds and by HIV’s toll on the immune system (USAID, 2009). Infections can progress far enough to lead to amputations. Many Zambians are unable to walk after an injury that might be considered minimal in more developed countries, and most cannot afford any currently-marketed options to compensate for the loss of leg function.
Alterations in Tricuspid Valve Mechanics as a Result of Annular Dilatation and Papillary Muscle Displacement: An In Vitro Study
Authors: Spinner Erin M. , Buice Dana , Lerakis Stamatios , Yoganathan Ajit P.
Published: July 2013

Current information as to the mechanism which causes malcoaptation of the tricuspid leaflets and leads to regurgitation is lacking. This study investigated the effect isolated and combined annular dilatation and PM displacement on valve mechanics. 3D echocardiography was used to quantify the changes in valve mechanics in relation to changes in tricuspid regurgitation.
Collagen Fiber Alignment and Maximum Principle Strain in the Axillary Pouch Predict Location of Failure During Uniaxial Extension
Authors: Voycheck Carrie A. , McMahon Patrick J. , Debski Richard E.
Published: July 2013

The glenohumeral joint is frequently dislocated in the anterior direction causing injury to the anteroinferior (axillary pouch, anterior band of the inferior glenohumeral ligament (AB-IGHL)) capsule. [1, 2] When unloaded, the axillary pouch consists of randomly oriented collagen fibers. These fibers play a pertinent role in its function to resist loading in multiple directions during dislocation at the extreme ranges of motion. [3] Maximum principle strain directions in the anteroinferior capsule have been shown to align with the AB-IGHL during increasing external rotation, suggesting that the collagen fibers may become more aligned with loading as well. [4] In addition, at positions of increased external rotation, the peak maximum principle strains in the capsule correspond to the location of a common capsular failure known as the Bankart lesion. [4] Further, an increase in collagen fiber alignment with load in the supraspinatus tendon has been shown in the toe region of the load-elongation curve. [5] Therefore, it was hypothesized that increases in the collagen fiber alignment and maximum principle strain would correlate with the location of tissue failure. The objective of this work was to determine the collagen fiber alignment and maximum principle strain in the axillary pouch during uniaxial extension to failure and to determine if these parameters could predict the location of tissue failure.
A Novel Method for Magnetic Isolation and Characterization of Polycarbonate-Urethane Wear Particles
Authors: Elsner Jonathan J. , Hakshur Keren , Shterling Avi , Linder-Ganz Eran , Eliaz Noam
Published: July 2013

Ferrography is a method for separating wear particles onto a slide. The method is based on the interaction between an external magnetic field and the magnetic moments of the particles suspended in a flow stream. It is advantageous in providing high detectability rate for a relatively large range of particle sizes (0.5–200 μm) [1]. A newer generation of ferrography, known as Bio-Ferrography, allows particles from five fluid samples to be isolated simultaneously on one slide and analyzed in terms of their number, chemistry, shape, dimensions, surface morphology, structure, etc. Since magnetization does not naturally occur in polymeric and biological materials, wear particles of such origins must be magnetized prior to Bio-Ferrography. This can be done, for instance, by binding to a ferromagnetic element, such as Er+3, originating from erbium chloride (ErCl3) solution. Such Bio-Ferrography technology has already been applied successfully in hip wear simulations for the separation of ultrahigh molecular weight polyethylene (UHWPE) wear debris suspended in bovine serum as lubricant [2].
A Numerical Investigation of Blood Damage in the Hinge Area of BMHV
Authors: Wu Jingshu , Fallon Anna , Simon Helene , Aidun Cyrus , Yoganathan Ajit
Published: July 2013

Bileaflet mechanical heart valves (BMHVs) have been widely used to replace native valves. Unfortunately, the design of bileaflet MHVs produces flow fields that may cause damage to blood elements, especially at the hinge area. The objectives of this study are to analyze the flow properties around the hinge area and through the valve, to further understand the cause of blood damage and provide improved designs to reduce the adverse hemodynamic effects of valves that cause platelet activation and damage blood elements. An important part of this improvement is to understand the hemodynamic effects produced by different valve designs, and how the surrounding flow fields affect thromboembolic formation. The hemodynamics of the valve flow is characterized by complex spatial and temporal three-dimensional structures that arise from the pulsatility of the flow, the complexity of the geometry and the flow-dependent motion of the valve leaflets. High fidelity simulations of the valve flow fields throughout the cardiac cycle is required to improve and refine existing valve designs so as to ultimately develop bileaflet MHVs with minimal thromboembolic complications.
Regenerated Contracting Myocardium May Improve Post-Surgery Right Ventricle Function: Patch Comparison Using MRI-Based Two-Layer Anisotropic Models of Human Right and Left Ventricles
Authors: Tang Dalin , Yang Chun , Geva Tal , Gaudette Glenn , del Nido Pedro J.
Published: July 2013

Patients with repaired Tetralogy of Fallot (ToF), a congenital heart defect which includes a ventricular septal defect and severe right ventricular outflow obstruction, account for the majority of cases with late onset RV failure. The current surgical approach, which includes pulmonary valve replacement/insertion (PVR), has yielded mixed results. One reason for the unpredictable results is that the PVR surgery only addresses pulmonary regurgitation. New surgical options including scar tissue reduction and RV remodeling have been proposed in order to improve RV function recovery [1]. Various RV reconstruction techniques are being investigated, including patch design (materials, sizes, and shapes) and myocardium regeneration techniques which have the potential that viable myocardium may be regenerated or placed in the patch area [2,4]. Wald and Geva et al. investigated effects of regional dysfunction on global RV function in patients with repaired ToF and reported that localized dysfunction in the region of the RV outflow tract patch adversely affects global RV function and regional measures, and may have important implications for patient management [5]. Recent advances in computational modeling have made it possible for computer-simulated procedures (virtual surgery) to be used in clinical decision-making process to replace empirical and often risky clinical experimentation to examine the efficiency and suitability of various reconstructive procedures and patch design in diseased hearts [4]. In this paper, cardiac magnetic resonance imaging (CMR)-based two-layer active anisotropic models of human right and left ventricles (RV/LV) were constructed to compare three different patch materials and investigate the potential improvement of regenerated contracting myocardium on RV function after PVR surgery: Patch 1 – Dacron scaffold; Patch 2 – pericardium treated with gluteraldehyde; Patch 3 – viable contracting myocardium (not currently available but represents future direction). The 3D CMR-based RV/LV/Patch combination models were solved to obtain 3D ventricular deformation and stress/strain distributions for accurate assessment of RV mechanical conditions and function. The computational models were validated by CMR data and then used to assess the effect of patch material properties with the ultimate goal of improving recovery of RV function after surgery.
Assessment of Radiographic Parameters for Adequate Reduction Following Syndesmotic Injury Causing Fibular Malrotation
Authors: Marmor Meir , Hansen Erik N. , Han Hyun Kyu , Buckley Jenni M. , Matityahu Amir
Published: July 2013

Rotational ankle injuries are one of the most common musculoskeletal problems treated by orthopaedic surgeons. The distal tibio-fibular syndesmosis may be disrupted during injury resulting in ankle instability. The goal of surgery is to restore anatomic relation of tibia, fibula, and talus. Any malreduction including that of the syndesmosis may result in poor clinical outcomes [1]. While currently accepted radiographic criteria can adequately detect tibio-fibular diasthesis or translation malreductions, it is not yet clear if the currently these criteria are equally suited for detection of rotational malreductions of the tibio-fibular syndesmosis [2]. The goal of this study is to quantify the sensitivity of fluoroscopic measurements of tibio-fibular overlap (TFO) and tibio-fibular clear space (TCS) to rotational malreductions of the syndesmosis. Standard x-ray imaging will be compared with a 3D fluoroscan which will simulate postoperative CT [3].
A Finite Element Study of Blast Overpressure on the Skull With and Without Helmet
Authors: Zhang Jiangyue , Pintar Frank A.
Published: July 2013

The use of advanced personal armor, especially the helmet, during combat has significantly reduced the incidence and severity of life threatening penetrating injuries from gunshot and blast shrapnel to the head and improved the overall survival rate of soldiers in combat [1]. On the other hand, the number of blast related injuries (68%) has increased to more than 4 times that of gunshot wounds (15%) and other injuries (17%), among which blast-induced traumatic brain injury (bTBI) has became the signature wound of the U.S. armed forces in Iraq and Afghanistan due to increased use of improvised explosive devices (IED) and rocket-propelled grenades (RPG) by the insurgents [2–4]. It is well known in detonation physics that the presence of a close proximity surface will increase the overpressure on the target due to blast wave reflection [5, 6]. The helmet, which has saved many lives from otherwise fatal penetration and blunt impact injuries, may unfortunately also serve as a reflecting surface and pose increased blast injury threat to the head. Consequently, the current study was designed to compare blast overpressures on the skull with and without helmet using a human head computational model.
Effect of Preconditioning on Collagen Fiber Recruitment: Inhomogeneous Properties of Rat Supraspinatus Tendon
Authors: Miller Kristin S. , Edelstein Lena , Soslowsky Louis J.
Published: July 2013

Cyclic preconditioning is a commonly accepted initial component of any tendon testing protocol. Preconditioning provides tendons with a consistent “history” and stress-strain results become repeatable allowing for rigorous evaluation and comparison. While it is widely accepted that preconditioning is important, changes that occur during preconditioning are not well understood. Micro-structural alterations, such as re-arrangement of collagen fibers, is one proposed mechanism of preconditioning [1,4]. However, this mechanism has not been examined. Therefore, the objective of this study is to locally measure: 1) fiber re-alignment during preconditioning, stress relaxation and tensile testing and 2) corresponding mechanical properties, to address mechanisms of preconditioning as well as tissue nonlinearity and inhomogeneity in the rat supraspinatus tendon. We hypothesize that 1) fiber re-alignment will be greatest in the toe region, but will also occur during preconditioning and 2) mechanical properties and initial collagen fiber alignment will be greater in the midsubstance location of the tendon compared to the tendon-to-bone insertion site.
Functional Role of the Superior Articular Facets of the Atlas in the Enhancement of Craniovertebral Junction Stability
Authors: Hallgren Richard C. , Cattrysse Erik , Zrull Jesse M.
Published: July 2013

Whiplash distortions of the cervical spine, occurring during the retraction phase of a rear end automobile accident, are known to cause posterior translation of the head relative to the chest and shoulders [1,2]. This anteroposterior shear produces sagittal plane rotation of the cervical spine which results in relative flexion between the occiput and the atlas (Fig. 1). This study demonstrates that there is a significant difference between the average angles of the anterior aspects and the posterior aspects of the superior facets of the atlas with respect to a horizontal (transverse) plane at P<0.01. We hypothesize that developmental variations in some individuals will allow excessive posterior translation of the head during rear end automobile accidents, and that this excessive motion may increase the risk of sustaining a whiplash-type injury for some individuals.
Effects of Age and Speed on Peak Lower Extremity Joint Torques During Gait When Controlling Speed and Step Length
Authors: Anderson Dennis E. , Madigan Michael L.
Published: July 2013

Significant age differences in self-selected gait kinetics have been reported in the literature. These include reduced torque and power at the ankle and increased work at the hip in older adults as compared to young adults [1, 2]. The reasons for these differences are complex and not fully understood. It is possible older adults adapt their gait to a safer, more stable gait pattern [3]. However, differences in gait may also be due to age-related neuromuscular changes such as reduced muscle strength in older adults [4].
Optimal Screw Placement for Reverse Total Shoulder Arthroplasty
Authors: Nguyen Thuc-Quyen D. , DiStefano James Guido , Park Andrew Y. , Diederichs Gerd , Buckley Jenni M. , Montgomery William H.
Published: July 2013

The reverse design of the total shoulder arthroplasty has been utilized for elderly patients with severely degenerated glenohumoral joints that are rotator cuff deficient. One of the most common causes of failure in shoulder arthroplasty involves loosening or catastrophic failure of the glenoid component. Such problems can be related to suboptimal fixation due to bone loss from fractures, severe degenerative changes and from previous failed arthroplasty surgery [1]. This emphasizes the need to secure the glenoid component with sound screw purchase beyond the glenoid vault. However, such fixation can often be tenuous as scapula bone quality is heterogeneous with a wide variation across short distances [2, 3]. Moreover, it can be difficult to identify regions with the best bone stock intraoperatively. This often requires multiple passes with the drill, which leads to further bone loss and potential decreased screw purchase. Thus, it is important for the surgeon to have a firm understanding of scapular anatomy with potential screw trajectories in mind.
The Influence of Trabecular Microstructure on Mechanical Properties and the Pullout Strength of Suture Anchors
Authors: Poukalova Mariya , Yakacki Christopher M. , Guldberg Robert E. , Lin Angela , Gall Ken
Published: July 2013

Suture anchors provide soft-tissue fixation, often tendons and ligaments, to bone. The most common type of surgery in which suture anchors are used is in rotator cuff repairs, where the anchor is implanted into the humerus to create a point of fixation for the supraspinatus.[1–2] Pullout strength, or the force necessary to pull the anchor from the bone, has been previously used as a metric to compare suture anchor performance. In investigating suture anchor performance, it has been suggested that pullout strength is positively correlated to bone mineral density (BMD).[2]
Effects of Tensile Stimulation on Gene Expression and In Vitro Stiffness of Murine Tissue Engineered Constructs
Authors: Dyment Nathaniel A. , Chokalingam Kumar , Shoemaker Amanda , Gooch Cynthia , Wylie Christopher , Shearn Jason T. , Butler David L.
Published: July 2013

Tendon and ligament injuries account for ∼45% of the 32.8 million musculoskeletal injuries that occur in the US every year [1]. Natural adult healing of these injuries is often inadequate and can diminish the quality of life for the patient. Tissue engineers, including those in our lab, have attempted to augment the natural healing process through a variety of methods including mechanical simulation of tissue engineered constructs (TECs) to improve repair outcome [2]. Building on our successes with mechanical stimulation, we now seek to modulate genes expressed during normal development in our TECs in culture to improve repair outcome in vivo. An initial step in this process is to determine if our TECs express genes within pathways of normal tendon development.
Comparison of Mechanical Characteristics of Deployment for Expandable vs. Fixed Interbody Cages: Implications for Premature Clinical Failures
Authors: Cheng Liu C. , Currey Jovauna M. , Modak Ashin , Han Hyun Kyu , McClellan R. Trigg , Pekmezci Murat , Buckley Jenni M. , Ames Christopher P.
Published: July 2013

Both expandable and non-expandable interbody cage designs are available to surgeons for cases involving spinal reconstruction and stabilization following single level lumbar corpectomy [1]. Different expandable cage designs are on the market [2], but all involve a manual mechanism to intraoperatively adjust the compressive load applied by the cage against the vertebral body endplates. Non-expandable cages do not have such a mechanism, and surgeons rely on cutting the cage to the appropriate length to achieve a “press-fit.” The clinical reasoning behind the expandable cage design is that the adjustability of the device will allow the surgeon to achieve the maximum contact area between the cage and the vertebral endplate without “overstuffing” the interbody space and thus causing a sagittal-plane deformity.
Biomechanical Analysis of Cervicothoracic Junction Osteototomy in Cadaveric Model of Ankylosing Spondylitis: Effect of Rod Material and Diameter
Authors: Scheer Justin K. , Tang Jessica A. , Deviren Vedat , Buckley Jenni M. , Pekmezci Murat , McClellan R. Trigg , Ames Christopher P.
Published: July 2013

Ankylosing spondylitis is a genetic condition [1] that frequently results in spinal sagittal plane deformity of thoracolumbar or cervicothoracic junction. Generally, a combination of osteotomy and spinal fixation is used to treat severe cases of ankylosing spondylitis to restore spinal balance and horizontal gaze [2]. This study investigates the biomechanics of opening wedge osteotomy at the cervicothoracic junction. Although surgical techniques for traumatic injury across the cervicothoracic junction have been well characterized in the clinical and biomechanical literature, the specific model of instrumented opening wedge ostetomy in autofused ankylosing spondylitis has not been studied biomechanically.
Revision Strategies in Spinal Deformity With Hardware Failure: A Biomechanical Study
Authors: Scheer Justin K. , Tang Jessica A. , Deviren Vedat , Buckley Jenni M. , Pekmezci Murat , McClellan R. Trigg , Ames Christopher P.
Published: July 2013

Failure of the posterior rods in long thoracolumbar deformity correction cases often requires revision surgery to treat the pseudoarthrosis and prevent loss of correction. While the entire rod can be replaced, this involves opening the entire incision which can lead to increased morbidity. Other clinically advantageous options include minimally invasive surgical approaches such as percutaneous insertion of connectors and additional rods.
Reduction in the Knee Adduction Moment During Walking Using Laterally-Wedged Shoes With and Without Ankle Support
Authors: Erhart Jennifer , Andriacchi Thomas
Published: July 2013

A high maximum adduction moment at the knee during walking has been associated with an increased rate of progression [1] and worse treatment outcome [2] of medial compartment osteoarthritis (OA) of the knee. Laterally-wedged insoles and shoes have been shown to reduce the knee adduction moment in healthy and osteoarthritic populations [3,4]. However, the mechanism of the effectiveness of such interventions is not well understood. Toda et al. showed that subtalar strapping with laterally wedged insoles in osteoarthritic subjects can improve valgus correction, but the authors did not look at the dynamic effects of walking [5]. A second study looked at the effects of lateral wedges with both semi-rigid ankle support and a rigid ankle-foot-orthosis and found a reduction in the adduction moment only with ankle support and a 10° lateral wedge. The wedge alone did not produce a reduction in the adduction moment [6]. Thus, it seems that the mechanism of action of the lateral wedge may be influenced by ankle motion.
Intervertebral Disc Residual and Equilibrium Viscoelastic Parameters Specific to Location and Degeneration Severity
Authors: Ellingson A. M. , Nuckley D. J.
Published: July 2013

Chronic low back pain affects an estimated 15–65% of the U.S. population. Disc degeneration is often accredited as the origin of low back pain. With degeneration comes the breakdown of proteoglycans, loss of water content, and a decrease in the height of the intervertebral disc (IVD). These changes likely affect the disc’s viscoelastic response, making modeling and subsequent prediction of degeneration mechanics difficult. Unfortunately, much of the previous mechanical testing of IVD tissues has involved excision of the tissue and disruption of annular fibers. To gain insight into the in situ viscoelastic material properties, we have developed a new methodology of hybrid confined / in situ compression. This technique also allows for the quantification of the residual stress and strain that the IVD experiences in vivo and improved viscoelastic modeling parameters. Residual measurements, to the knowledge of the authors, have yet to be reported in previous studies. Therefore, the purpose of this study was to define the viscoelastic properties of the intact intervertebral disc as well as the residual stress/strain specific to degeneration grade and location.
The Relationship Between Wall Stress and 3D Asymmetry in Repaired and Ruptured Abdominal Aortic Aneurysms
Authors: Doyle Barry J. , McGloughlin Tim M.
Published: July 2013

Abdominal aortic aneurysm (AAA) is a permanent dilation of the infrarenal aorta and is defined as having a diameter 50% greater than the original diameter. If left untreated, an AAA will continue to expand until rupture. The maximum diameter is currently the primary indicator of rupture-risk with AAAs > 5.5 cm deemed a likely to rupture. There have, however, been many reports identifying the inadequacies of the maximum diameter criterion to accurately determine the threat of rupture. It is believed by many researchers that there is a need to review the decision of surgical intervention based solely on aneurysm diameter, and rather include other relevant risk factors. These additional risk factors could, for example, include, AAA wall stress, AAA expansion rate, degree of asymmetry, presence of intraluminal thrombus (ILT), and hypertension. The addition of these parameters may aid the surgical decision-making process. A previous report by our group identified the relationship between asymmetry and posterior wall stress in patient-specific cases [1,2] and as over 80% of ruptures occur on the posterior wall [3] this finding may have significant clinical relevance. In this previous report, the study group was limited to 15 cases and asymmetry was only measured in the anterior-posterior plane. This current paper furthers this previous work by increasing the cohort to 40 cases of electively repaired AAAs and also examines 8 cases of ruptured AAAs. The methodology has been improved to now measure asymmetry in all three dimensions (3D).
Mechanical Assistance for the Fontan Circulation Using an Intravascular Axial Flow Blood Pump
Authors: Bhavsar Sonya S. , Moskowitz William B. , Throckmorton Amy L.
Published: July 2013

Research indicates that an afterload reducing agent improves ventricular-vascular interactions and Fontan hemodynamics [1]. Few such therapeutic alternatives exist for the failing Fontan patient beyond conventional pharmacologic therapy. To address this need for therapeutic options, we are developing an intravascular, magnetically levitated axial flow blood pump to support the total cavopulmonary connection (TCPC) of a failing Fontan in adolescent and adult patients [1,2]. Our pump is designed to provide mechanical pressure augmentation of blood flow from the inferior vena cava (IVC) to the lungs, thus improving systemic venous pressure and increasing ventricular filling.
µCT/HR-pQCT Image Based Plate-Rod Microstructural Finite Element Model Efficiently Predicts the Elastic Moduli and Yield Strength of Human Trabecular Bone
Authors: Liu X. Sherry , Fields Aaron J. , Keaveny Tony M. , Shane Elizabeth , Guo X. Edward
Published: July 2013

Osteoporosis is an age-related disease characterized by low bone mass and architectural deterioration, which affects primarily the trabecular sites and causes millions of fractures. High-resolution image voxel-based finite element (FE) models with the detailed 3D microstructure have been widely utilized to assess the mechanical properties of trabecular bone [1, 2]. However, the very large size of the voxel-based FE model, in general, limits its application to linear elastic cases. Despite the great potential it has shown in studying trabecular bone failure, iterative nonlinear analysis is still hard to be performed efficiently. Therefore, there is an apparent need for an alternative approach, which maintains the advantages of the voxel-based FE models in capturing details of trabecular microstructure, while allowing faster computation. Based on the individual trabeculae segmentation (ITS) technique [3], a specimen-specific plate-rod (P-R) microstructural FE model was developed by substituting the individual beam/shell element for 3D volume of trabecular plate/rod of μCT images of trabecular bone (21 μm resolution) (Fig. 1). The first goal of this study is to validate both linear and nonlinear predictions based on the P-R models for in vitro μCT images of human trabecular bone samples. The prediction accuracy and computational speed of the P-R model were examined by comparing with those of the voxel-based FE model.