bluuebunny/crossref_metadata_2025 huggingface dataset:
Modification of a Simplified Hip Joint Simulator Into an ISO 14242-1 Compliant Design and a Comparison of Wear Test Results
Authors: Saikko Vesa , Morad Omar , Viitala Raine
Published: November 2021

The ISO 14242-1 standard for hip joint simulator wear testing specifies a set of test conditions for the simulation of normal level walking in optimal conditions. Since some of the established simulators, such as the 12-station HUT-4, are not ISO 14242-1 compliant, the present study was carried out to answer the following question. Does wear produced in ISO 14242-1 conditions differ from that obtained earlier with the simplified HUT-4 hip joint simulator for similar specimens in normal level walking, optimal conditions? The established HUT-4 hip joint simulator was made ISO compliant by an implementation of a number of modifications. One of the modifications was the design and construction of a novel servo-electric load actuator with a proven dynamic response. The other modifications were related to the Euler sequence of motions, acetabular abduction angle, enclosure of the lubricant chamber, and temperature control. A 5 million-cycle wear test with thin, large-diameter VEXLPE liners resulted in a wear rate close to that obtained earlier with the HUT-4. The burnished bearing surface in both tests was in agreement with clinical retrieval studies. It appeared that a more simple, inexpensive hip joint simulator can reproduce clinical wear mechanisms. However, the simulator must meet certain basic requirements. The most important of these is likely to be the correct type of multidirectional relative motion, for which biaxial motion is sufficient. It is emphasized that the present study was not intended to show a similarity in wear produced by the ISO 14242-1 and HUT-4 wear test systems.
Structural Identification Using Learning Vector Quantization Neural Network
Authors: Kozukue Wakae , Miyaji Hideyuki
Published: November 2021

The Learning Vector Quantization (LVQ) neural network is applied to the defect identification problem for structures, which is important when constructing the mathematical model of structures. In this study the eigenmodes of a plate obtained from FEM and the location of a defect contained in that plate are used as the training data for neural network and the position of the defect is identified by giving the unlearned input data to the trained network. As a result the better accuracy is obtained compared to the case when using the backpropagation neural network commonly used in the various studies.
The Effect of Uniaxial Cyclic Deformation on the Evolution of Phase Transformation Fronts in Pseudoelastic NiTi Wire
Authors: Iadicola Mark A. , Shaw John A.
Published: November 2021

Experiments are presented of the response of pseudoelastic NiTi wires subjected to displacement controlled cycles. A custom built thermo-mechanical testing apparatus is used to control the background temperature field of the wire specimen while allowing the evolution of transformation fronts to be tracked by full field infrared imaging. Two experiments under similar end-displacement histories, but at temperatures ≈8°C apart, are shown to give remarkably different cyclic responses. The mechanical response for the lower temperature experiment continued to soften but retained its shape through 43 partial transformation cycles, and the pattern of transformation fronts seemed to reach a steady state. The response for the higher temperature experiment showed a change in shape of the mechanical response and distinct changes in transformation front patterns over 31 partial transformation cycles.
Modelling of Shape Memory Alloy Springs for Passive Vibration Isolation
Authors: Lagoudas Dimitris C. , Khan Mughees M. , Mayes John J.
Published: November 2021

In this work, a basis is set forth for studying the effect of Shape Memory Alloy pseudoelasticity on the behavior of vibrating systems. A physically based model for Shape Memory Alloy psuedoelastic response is modified to predict the component level response of Shape Memory Alloy springs and is integrated into a numerical solution of the non-linear dynamic system that results from the inclusion of Shape Memory Alloy components in a dynamic structural system. The effect of pseudoelasticity on a dynamic system is investigated for various loading levels and system configurations, and the importance of large amplitude motion is discussed. Promising results from these investigations, and the application of these studies to experimental work in progress by the authors are briefly discussed.
Energy Analysis for a Twisting and Bending Coupled Piezoelectric Actuator for Miniature Unmanned Aerial Vehicles
Authors: Kwak Seung-Keon , Washington Gregory
Published: November 2021

In this research, we examine aircraft components based on their interaction with the system. This essentially asks the question is there enough energy available (without losses) in a candidate system to meet the energy required. The goal of this research is to highlight this design process with the design and construction of an active aircraft wing. A new twisting and bending coupled piezoelectric actuator based on the spatial aperture shading technique is introduced to build deformable wings. The shaped electrode twisting actuator consists of two layers of PZT-5H (lead zirconate titanate) and one middle layer of steel shim. The directionally shaped electrode technique is applied to achieve the both twisting and bending motions of the actuator. The comparison of an analytical model, a numerical analysis, and actual experimental results for the actuator are given.
Modeling of Large Amplitude Vibration Control of Beams and Cylindrical Deformations of Plates and Shells With Distributed Piezoelectric Actuators
Authors: Schmidt R.
Published: November 2021

The paper deals with the geometrically nonlinear theory and finite element method for the simulation of large amplitude vibration control of straight and curved beams, or what is equivalent, cylindrical deformations of plates and shells, consisting of a master structure with integrated thin piezoelectric layers or patches. The theory is based on the Bernoulli or Kirchhoff-Love hypothesis, respectively, and constitutes an entirely Lagrangean displacement formulation for small strains with no restrictions imposed on the magnitude of rotations or displacements. Based on modified strain measures the strain-displacement relations are only quadratic in terms of displacements and their gradients. Work-conjugate stress resultants and stress couples are derived from the internal virtual work associated with the first approximation of the strain energy density. Based on the principle of virtual displacements the FE equations for the simulation of static and dynamic response control are derived.
A Simplified Experimental Model to Simulate an Air Conditioner
Authors: Rosario Luis , Rahman Muhammad M. , Porteiro Jose L. F.
Published: November 2021

A simplified model based on experimental data has been developed for applications in air-conditioning systems simulations. Cycle thermodynamic relationships, along with experimental data, were used to mathematically model the air-conditioning system. Characteristic parameters of the equipment were determined from the results of a limited number of test points. The following parameters were used: the clearance factor C, the piston displacement PD, the efficiency of the compressor ηcomp, the sensible heat factor SHF and the product of the overall heat transfer coefficient times area (UA) for the heat exchangers. Component performance simulation data was validated using experimental data from a 3-ton air conditioner. The model calculates the following parameters: coefficient of performance (COP), system capacity (qe), system heat rejection (qc), and compressor power (W) at any operating condition. The simulation model consists of work and energy balance relationships for the evaporator, condenser, expansion device, and compressor. The model predicted system heat rejection (qc) and system capacity (qe) within 10% of experimental data. The required compressor power (W) was predicted within 5% of uncertainty. However, the coefficient of performance (COP) had an uncertainty slightly higher than ±13% when compared to experimental data. The simulation model can be used as an effective tool for much faster equipment certification minimizing the required number of testing points.
The Effect of Roll Waves on the Hydrodynamics of Falling Films Observed in Vertical Column Absorbers
Authors: Miller William A. , Keyhani Majid
Published: November 2021

A thin falling film is well suited to simultaneous heat and mass transfer because of the small thermal resistance through the film and because of the large contact surface achievable at low flow rates. The film enters as a smooth laminar flow and quickly transitions into small-amplitude wavy flow. The waves grow in length and amplitude and are identified as roll waves. This flow regime is termed “wavy-laminar flow,” and modern heat and mass transfer equipment operate in this complicated transition regime. Research published in open literature has shown the mass flow rate in the roll waves to be about 10 to 20 times greater than that in the laminar substrate. As the film fully develops, the waves grow in mass and the film substrate thins because fluid is swept from the substrate by the secondary flows of the roll wave.

Many studies have been conducted to measure and correlate the film thickness of wavy-laminar flows. Literature data show that Nusselt’s theory for smooth laminar flow can over predict the film thickness by as much as 20% for certain wavy-laminar flow conditions. The hydrodynamics of falling films were therefore studied to measure the film thickness of a free-surface falling film and to better understand the parameters that affect the variations of the film thickness.

A flow loop was set up for measuring the thickness, wave amplitude, and frequency of a film during hydrodynamic flow. Decreasing the pipe diameter caused the amplitude of the wavy flow to diminish. Measurements monitored from stations along the falling film showed a thinning of film thickness. Fully developed flow required large starting lengths of about 0.5 m. The film thickness increases as the Reynolds number (Re) increases. Increasing the Kapitza number (Ka) causes a decrease in the film thickness. Regression analysis showed that the Re and Ka numbers described the data trends in wavy-laminar flow. Rather than correlating the Re number in discrete ranges of the Ka number as earlier researchers have done, this research made the Ka number an independent regression variable along with the Re number. The correlation explains 96% of the total variation in the data and predicts the experimental data within an absolute average deviation of ±4.0%. The correlation supports the calculation of a fully developed film thickness for wavy-laminar falling films.
Single Stage Heat Transformer Used to Recover Energy in an Oil Distillation Column
Authors: Rivera W. , Cerezo J.
Published: November 2021

This paper presents the theoretical analysis of the use of a single stage absorption heat transformer operating with the water-lithium bromide mixture coupled to an oil distillation column installed in a Mexican refinery.

The distillation column is used to produce mainly C5H12-1 and C5H12.2. Actually, the heat load in the condenser column is delivered to the atmosphere at 82°C while heat is supplied to the reboiler of the column at 115°C to distill the oil products.

In order to reduce the heat load supplied to the reboiler a single stage heat transformer may be coupled of the way that the heat delivered in the condenser may be used as heat input in the generator and evaporator of the heat transformer which increases the heat to a more useful level in the absorber to preheat the stream entering to the reboiler.

To do this, a mathematical model of a heat transformer was developed in FORTRAN and introduced to the software ASPEN PLUS. Both components coupled were modelled on steady state conditions.

The results showed that the coefficient of performance of the heat transformer which is directly related with the energy saving in the column is highly dependent of the condenser and absorber temperatures of the heat transformer.

At a condenser temperature of 22°C (cooling water temperature of 14°C and ΔT = 8°C) which can be obtained in winter time in that part of Mexico, up to 43% of the energy supplied to the reboiler of the distillation column may be saved by using the heat transformer, but in general at a condenser temperature of 30°C, which is a more representative temperature during a whole year, up to 30% of the energy may be saved.

Also, it was shown that the reboiler’s area may be reduce considerably if the distillation column was built since the beginning integrating a heat transformer, which may helps to reduce the extra capital costs caused by the use of the heat transformer.
Combined Space-Heating/Water-Heating System Performance
Authors: Baskin Evelyn , Spears John
Published: November 2021

With increasing fuel prices, various energy-saving techniques have been considered for residential appliances. Space heating accounts for the largest energy use in residential applications. One method proposed by manufacturers to keep operating cost low is to combine residential water-heating and space-heating functions into a single system. This paper presents the field test results of the performance of a combined water-heating/space-heating system under actual usage conditions. The system was installed in an 1187 ft2 (110 m2) home (Green Home) located in the Washington DC area. Data were collected for a one-year period. The water-heating performance was established by evaluating the hot water usage data during the test period. Water-heating/space-heating performance was established by using hot water data plus the amount of hot water circulated for space heating during the winter months. Analysis of the data indicated that the system produces hot water at an efficiency averaging 48% for water heating in the summer months and produces hot water at an efficiency ranging between 63.5–69.4% for combined water-heating/space-heating during the winter months. The relative humidity was maintained in the home at substantially lower level than that of the outside air, and the inside temperature was kept at the desired setting.
Design and Experimental Results of Small-Scale Rotary Engines
Authors: Fu Kelvin , Knobloch Aaron J. , Martinez Fabian C. , Walther David C. , Fernandez-Pello Carlos , Pisano Al P. , Liepmann Dorian , Miyaska Kenji , Maruta Kaoru
Published: November 2021

A research project is currently underway to develop small-scale internal combustion engines fueled by liquid hydrocarbons. The ultimate goal of the MEMS Rotary Internal Combustion Engine Project is to develop a liquid hydrocarbon fueled MEMS-size rotary internal combustion micro-engine capable of delivering power on the order of milli-watts. This research is part of a larger effort to develop a portable, autonomous power generation system with an order of magnitude improvement in energy density over alkaline or lithium-ion batteries. The rotary (Wankel-type) engine is well suited for the fabrication techniques developed in the integrated chip (IC) community and refined by the MicroElectroMechanical Systems (MEMS) field. Features of the rotary engine that lend itself to MEMS fabrication are its planar construction, high specific power, and self-valving operation.

The project aims at developing a “micro-rotary” engine with an epitrochoidal-shaped housing under 1 mm3 in size and with a rotor swept volume of 0.08 mm3. To investigate engine behavior and design issues, larger-scale “mini-rotary” engines have been fabricated from steel. Mini-rotary engine chambers are approximately 1000 mm3 to 1700 mm3 in size and their displacements range from 78 mm3 to 348 mm3.

A test bench for the mini-rotary engine has been developed and experiments have been conducted with gaseous-fueled mini-rotary engines to examine the effects of sealing, ignition, design, and thermal management on efficiency. Preliminary testing has shown net power output of up to 2.7 W at 9300 RPM. Testing has been performed using hydrogen-air mixtures and a range of spark and glow plug designs as the ignition source. Iterative design and testing of the mini-engine has lead to improved sealing designs. These particular designs are such that they can be incorporated into the fabrication of the micro-engine.

Design and fabrication of a first generation meso-scale rotary engine has been completed using a SiC molding process developed at Case Western Reserve University. The fabrication of the micro-rotary engine is being conducted in U.C. Berkeley’s Microfabrication Laboratory.

Testing of the mini-engine has lead to the conclusion that there are no fundamental phenomena that would prevent the operation of the micro-engine. However, heat loss and sealing issues are key for efficient operation of the micro-engine, and they must be taken into account in the design and fabrication of the micro-rotary engine. The mini-rotary engine design, testing, results and applications will be discussed in this paper.
Exergoeconomic Optimization of a Heat Exchanger With a Two-Phase Refrigerant
Authors: D’Accardia Massimo Dentice , Fichera Alberto , Sasso Maurizio , Vidiri Margherita
Published: November 2021

In this paper, the exergoeconomic theory is applied to a heat exchanger for optimization purposes. The investigation was referred to a tube-in-tube condenser with the single-phase fluid to be heated flowing in the inner annulus and the two-phase refrigerant flowing in the external annulus. First, the irreversibility due to heat transfer across the stream-to-stream temperature difference and to frictional pressure drops is calculated as a function of two design variables: the inner tube diameter and the saturation temperature of the refrigerant, on which the heat-exchange area directly depends. Then, a cost function is introduced, defined as the sum of two contributions: the amortization cost of the condenser under study and the operating cost of the conventional electric-driven heat pump in which this component will have to work. The latter contribution is directly related to the overall exergy destruction rate in the plant, whereas the amortization cost mainly depends on the heat-exchange area. So, design optimization of the device can be performed by minimising this cost function with respect to the selected design variables. The so-called structural approach (Coefficients of Structural Bond) is used in the optimization, in order to relate the local irreversibility in the condenser to the overall exergy destruction rate in the heat-pump plant. A numerical example is discussed, in which, for a commercial heat exchanger, the design improvements needed to obtain a cost-optimal configuration are investigated. The results show that significant improvements can be obtained with respect to devices based on conventional values of the design parameters.
The Exergy of Lift, and Aircraft Exergy Flow Diagrams
Authors: Paulus David M. , Gaggioli Richard A.
Published: November 2021

Aside from incidental, auxiliary loads, in level flight the principal load on the aircraft propulsion engine is the power required to provide the continuous lift. To construct an exergy flow diagram for an aircraft — for example, for the purpose of exergy costing — an expression is needed for the exergy delivered to (and by) the wings. That is, an expression is needed for the exergy of lift. In this paper an expression is developed for this quantity, applicable not only in level flight but in other modes of flight as well. Then, three exergy flow diagrams are presented for a light aircraft, operating under three conditions: climb, level economy cruise, and level maximum power. The expression for lift exergy and these exergy flow diagrams are relevant to the optimal design of aircraft subsystems [1].
One-Dimensional, Transient Model of Heat, Mass, and Charge Transfer in a Proton Exchange Membrane
Authors: Eaton Brandon , von Spakovsky Michael R. , Ellis Michael W. , Nelson Douglas J. , Olsommer Benoit , Siegel Nathan
Published: November 2021

A transient, one-dimensional, model of the membrane of a proton exchange membrane fuel cell is presented. The role of the membrane is to transport protons from the anode to cathode of the fuel cell while preventing the transport of other reactants. The membrane is modeled assuming mono-phase, multi-species flow. For water transport, the principle driving forces modeled are a convective force, an osmotic force (i.e. diffusion), and an electric force. The first of these results from a pressure gradient, the second from a concentration gradient, and the third from the migration of protons from anode to cathode and their effect (drag) on the dipole water molecules. Equations are developed for the conservation of protons and water, the conservation of thermal energy, and the variation of proton potential within the membrane.

The model is solved using a fully implicit finite difference approach. Results showing the effects of current density, pressure gradients, water and heat fluxes, and fuel cell start-up on water concentration, temperature, and proton potential across the membrane are presented.
Operating State Historical Data Analysis to Support Gas Turbine Malfunction Detection
Authors: Pinelli M. , Venturini M.
Published: November 2021

The paper describes a methodology to determine gas turbine operating state based on the analysis of normalized field data. This methodology consists in normalizing measured value with respect to that expected, calculated in the actual boundary conditions and working point. The normalization procedure, if applied on line, provides useful information to support the machine Health State determination.

In this paper, the methodology has been applied to field measurements taken on a 5 MW gas turbine running in a natural gas compression plant. The first results of field measurements analysis along a two year period are presented. Relations between compressor performance drops and the probable causes of malfunctioning have been identified. Some significant results are then presented.
Comparison Between Speco-Based and Functional Exergoeconomic Approaches
Authors: Lazzaretto Andrea , Tsatsaronis George
Published: November 2021

Various exergoeconomic approaches have been developed in the last 20 years. These approaches include the ones by Frangopoulos, Lazzaretto, Tsatsaronis, Valero, von Spakovsky and their co-workers. The paper discusses exergoeconomic approaches based on specific costs (SPECO), thermoeconomic functional analysis (TFA) and engineering functional analysis (EFA). Simple examples are used to demonstrate the differences among these approaches.
A Diagnosis Procedure for Energy Conversion Plants: Part I — Description of the Method
Authors: Stoppato Anna , Carraretto Cristian , Mirandola Alberto
Published: November 2021

In order to achieve the “best” use of energetic and economic resources, not only the design of a power plant has to be “optimized”, but also its operation and management according to users demand and boundary conditions. So, the availability of procedures and tools able to perform diagnosis activities is important in both locating the causes of malfunctions and evaluating their influence on the plant performances.

The Part I of this paper presents a diagnosis method, whose target is to evaluate the deviations of the plant performances from “reference values”, identify their causes and quantify their influence.

The method is based on the exergetic and the exergoeconomic analyses and supplies some indicators of performance related to energetic and economic aspects; the use of these indicators helps the analyst plan proper operation or maintenance actions.

Part II of the paper will discuss the results obtained by checking the actual operation of some power and cogenerative plants.
Proton Exchange Membrane (PEM) Fuel Cell System Model for Automotive Vehicle Simulation and Control
Authors: Boettner Daisie D. , Paganelli Gino , Guezennec Yann G. , Rizzoni Giorgio , Moran Michael J.
Published: November 2021

This paper describes a Proton Exchange Membrane (PEM) fuel cell system model for automotive applications that includes an air compressor, cooling system, and other auxiliaries. The fuel cell system model has been integrated into a vehicle performance simulator that determines fuel economy and allows consideration of control strategies. Significant fuel cell system efficiency improvements may be possible through control of the air compressor and other auxiliaries. Fuel cell system efficiency results are presented for two limiting air compressor cases: ideal control and no control. Extension of the present analysis to hybrid configurations consisting of a fuel cell system and battery is currently under study.
Product Design and Development of Automated Waste Removal System for the Handicapped
Authors: McGrath Thomas P. , Butler Daniel T. , Matthews Daniel C. , Latgis Jason , Zink Laurie E. , King Russell T.
Published: November 2021

This paper describes the product design and development process for an electrically operated residential waste removal system. The objective of the project is to provide an alternative method for elderly or handicapped persons to remove household trash, without the difficulties of lifting, tying, and disposing or the cost of complicated trash compacting systems. The ultimate goal of the system is to increase the quality of life for the physically handicapped. Automatically removing household trash from the home will increase the self-sufficiency of the handicapped, and decrease the chance of injury associated with everyday tasks.
A Smith Machine for Exercise in Micro-Gravity
Authors: House Audrey S. , Taylor Jenny L. , Lee Daina L. , Jones G. Marshall , Todd Beth A. , Lee Thomas B. D. , Wilson Kristin L. , Lancaster Bethany R. , Wear Richard
Published: November 2021

In a zero-gravity environment, astronauts exhibit Bone Mineral Density (BMD) loss in their spine and lower extremities with no net changes in the upper extremities [1]. Astronauts use their upper extremities for locomotion in flight by pushing off of the walls of the spacecraft, but since their lower extremities are not supporting their mass, as in gravitational loading, there is significant BMD loss in these areas.
The Influence of Experiment Conditions on Osteon Pushout Tests
Authors: Dong X. Neil , Guo X. Edward
Published: November 2021

Cement lines are boundaries between secondary osteons and the surrounding interstitial bone tissue in cortical bone as well as between trabecular packets in trabecular bone tissue. The interfacial properties of cement lines have been determined by performing an osteon pushout test [1]. It supported the hypothesis that the cement line is a weak interface.
In Vitro Comparison of a Translational Anterior Cervical Plate With a Constrained Anterior Cervical Plate
Authors: DiAngelo Denis J. , Liu Weiqiang , Olney Kristine M. , Foley Kevin T.
Published: November 2021

Cervical spondylosis is the most common degenerative disorder affecting the cervical spine and is often treated surgically to prevent further neurological deterioration. However, clinical experience has shown that anterior cervical plating does not prevent construct failure in multi-level cervical corpectomy (Vaccaro et al., 1998). We have previously shown that anterior cervical plating reverses the load transfer through multi-level strut-grafts and may promote pistoning of these grafts (DiAngelo et al., 2000). The design of the anterior cervical plate (ACP) may contribute to this phenomenon. The purpose of this study was to compare the graft loading mechanics of two different anterior cervical plating systems; one with a constrained plate-screw interface versus another with a semi-constrained, translational plate-screw interface.
An Experimental Model of Adult-Onset Slip Progression in Isthmic Spondylolisthesis
Authors: Patwardhan Avinash G. , Simonds James , Ghanayem Alexander J. , Voronov Leonard , Ali Arif , Hodges Scott D. , Paxinos Odysseas , Havey Robert M. , Phillips Frank , Gavin Thomas M. , Meade Kevin P.
Published: November 2021

Spondylolisthesis is defined as a slippage of a vertebral body on the one below. Isthmic spondylolisthesis, caused by stress fracture or a developmental anomaly at the pars interarticularis, is the most common type of lumbar spondylolisthesis with a 6% incidence in adults. Isthmic lumbar spondylolisthesis is a frequent cause of disabling low-back and leg pain. The goal of this study is to improve the quality of treatment of these patients.
Vertebral Bone Compression Fracture Analysis With and Without Synthetic Materials
Authors: Higgins Kathryn B. , Langrana Noshir A. , Harten Robert D. , Cuitino Alberto M. , Reiter Mitchell F.
Published: November 2021

The vertebral body is a mass of spongy bone contained in a dense cortical shell. The cancellous core is comprised of vertical and horizontal trabeculae. The shape and orientation of these trabeculae is referred to as the microarchitecture of the cancellous bone. A great deal of information on the function of vertebral bodies can be determined by analyzing the biomechanics and morphology of cancellous bone. [1] A model for analysis must accurately represent the trabecular pattern of the vertebral body. That model can then be used to predict mechanical properties of bone under various conditions.
Three-Dimensional Dynamic Modeling of the Human Knee to Include Tibio-Femoral and Patello-Femoral Joints
Authors: Caruntu Dumitru , Hefzy Mohamed Samir
Published: November 2021

Most of the anatomical mathematical models that have been developed to study the human knee are either for the tibio-femoral joint (TFJ) or patello-femoral joint (PFJ). Also, most of these models are static or quasistatic, and therefore do not predict the effects of dynamic inertial loads, which occur in many locomotor activities. The only dynamic anatomical model that includes both joints is a two-dimensional model by Tumer and Engin [1]. The model by Abdel-Rahman and Hefzy [2] is the only three dimensional dynamic model for the knee joint available in the literature; yet, it includes only the TFJ and allows only for rigid contact.
A Model Based Approach for Efficient Segmentation of Knee Cartilage From MR Image Data
Authors: Alexander Eugene J. , Andriacchi Thomas P.
Published: November 2021

A novel algorithm was developed to facilitate segmentation of the articular cartilage of the knee from magnetic resonance (MR) image data. The new approach uses a model of the bone and cartilage elements of the knee as a template. The operator initializes the template by aligning certain bony anatomic landmarks. The inner cartilage surface (ICS) is determined through a standard seed growing segmentation approach; the bone elements of the template are then fit to the ICS through an elastic registration technique. The deformation fields thus obtained are subsequently applied to the appropriate cartilage templates. The deformed templates and ICS normals, in conjunction with a gaussian probability distribution function and the subject image data, are used to produce the final estimate of the cartilage surfaces.
The Influence of Depth-Dependent Inhomogeneity on the Contact Response of Human Patellar Cartilage
Authors: Krishnan Ramaswamy , Park Seonghun , Soltz Michael A. , Pawluk Robert J. , Ateshian Gerard A.
Published: November 2021

One of the aims of modeling articular cartilage is to determine its ability to sustain its physiological loading environment and the mechanisms by which this functional response might be compromised. It has long been hypothesized that excessive stresses in cartilage might initiate osteoarthritis, thus a determination of the state of stress within the tissue has been an important objective. It has also been hypothesized that the interstitial water of articular cartilage plays a primary role in producing low friction and wear as well as shielding the collagen-proteoglycan solid matrix from a significant portion of the loads applied across joints [1]. Furthermore, cartilage exhibits inhomogeneity through its depth, both in its tensile and compressive properties, though the significance of this inhomogeneity on the functional response of cartilage remains to be elucidated. The specific aims of the current study are to (a) experimentally determine the depth-dependent tensile and compressive properties of human patellar articular cartilage; (b) determine the response of cartilage to loading under a contact configuration using finite element models which employ these experimentally determined material properties; and (c) compare the response of the tissue to a hypothetical homogeneous distribution of material properties through the depth. The first hypothesis is that the inhomogeneity of articular cartilage acts to maximize the interstitial fluid load support at the articular surface. The second hypothesis is that the depth-dependent inhomogeneous distribution of cartilage properties acts to produce a more homogeneous state of stress than would be achieved had the properties been constant through the depth. This study extends our previous contact analyses of homogeneous cartilage layers [2,3].
The Strain-Softening of Bovine Articular Cartilage Under Infinitesimal Deformation in Unconfined Compression
Authors: Wang Christopher C.-B. , Chahine Nadeen O. , Kelly Terri-Ann N. , Lai W. Michael , Hung Clark T. , Ateshian Gerard A.
Published: November 2021

Significant strain-softening of articular cartilage along its depth direction has been observed in several studies [1,2], where the free-swelling equilibrium state of the tissue was taken to be the reference configuration for subsequent deformation. Microstructural models have been proposed to interpret this softening as buckling of pre-stressed collagen fibers [3,4]. In this study, we propose that a constitutive model which accounts for the disparity in tensile and compressive moduli of cartilage as well as the osmotic swelling response, can explain this experimentally observed strain-softening mechanism. The strain-softening behavior of the tissue is investigated experimentally and theoretically along three mutually perpendicular directions: directions parallel and perpendicular to the split line direction (1- and 2-direction), and normal to the articular surface (3-direction). A conewise nonlinear elasticity model is incorporated into the triphasic theory [5] to interpret this strain-softening in the context of Donnan osmotic swelling [6].
How Simplifying Assumptions Affect the Computation of Three-Dimensional Knee Loads in Cycling
Authors: Gregersen Colin S. , Hull M. L.
Published: November 2021

Determining the force and moment components transmitted by the knee is useful both to understand the etiology of over-use knee injuries common in cycling [1] and also to assess how well different interventions protect against over-use injury. Because the loads thought to be primarily responsible for over-use knee injury are the non-driving moments (varus/valgus and internal/external axial moments) transmitted by the knee [2], a 3-D model is necessary for calculating these loads. To our knowledge, no study has developed a model that includes complete 3-D kinematics of the segments to calculate these loads. Consequently one objective of this study was to develop a complete, 3-D model to calculate the intersegmental knee loads during cycling. A second objective was to use this model to examine how simplifying assumptions affect the 3-D knee loads.
Mechanical Factors Can Influence the Gender Differences in the Incidence of Non-Contact Injuries
Authors: Andriacchi Thomas , Camarillo David , Alexander Eugene , Dyrby Chris
Published: November 2021

The kinematics and kinetics of running to a stop and running and cutting were analyzed in the context of identifying mechanisms for non-contact injury to the anterior cruciate ligament of the knee. The study addressed the hypothesis that gender influences the mechanics of the way individuals perform running to a cut and running to a stop. The results demonstrate a difference during the early landing phase of the maneuver. Two patterns of limb loading were identified during the landing phase (foot strike to 200msec) of the run to cut maneuver. The results of this study suggest a potential injury mechanism associated with the biomechanics of landing in preparation for a run to stop or run to cut maneuver. Nine of ten male subjects in this population tended to land in a manner that produced a greater magnitude of the force component along the axis of the tibia. These findings provide new information that can be applied towards understanding gender difference patterns in non-contact ACL injuries.
Implant Technology: Knee Design for Improved Function and Wear
Authors: Bartel Donald , Edidin Av , Johnson Todd , Sculco Thomas , Wright Timothy
Published: November 2021

Total knee replacement has become an accepted treatment for diseased and damaged joints with over 150,000 surgeries performed annually in the United States alone. The popularity of knee replacement stems from the excellent clinical results, which in some reported series exceeded ninety percent at twenty years follow-up [1]. The high level of clinical success in elderly populations has spurred surgeons to extend the indications to younger patients; today, about a third of total knee replacements are implanted in individuals under sixty-five years of age.
A Method for the Rapid Prototyping of Custom Contoured Cushions
Authors: Parkinson Matthew B. , Huggins Jane E.
Published: November 2021

Decubitous ulcers (“pressure sores”) are a significant concern for people using wheelchairs. In fact, results published by the University of Kansas [1] indicate that over half of those using wheelchairs will develop a pressure sore at some point. This susceptibility is due to the conditions under which these ulcers develop: shear stress and pressure work together to cut off the blood supply to the surface tissue, which subsequently dies. Heat and moisture can increase the likelihood of this necrosis and the rate at which it occurs. Although sores can develop quickly (onset can occur in as few as fifteen minutes), they may take months to heal.

Appropriate seat cushion selection helps to mitigate the causative factors [2]. In particular, custom-contoured cushions (CCC) can offer dramatic improvements. Research has shown that CCC’s offer the best distribution of pressure and reduction of shear stress, reducing these factors by as much as 80% [3]. CCC’s are not commonly used, however, because the cost and time involved in design, manufacture, and delivery are prohibitive.

The obstacles of cost, time, and inconvenience, can be overcome by applying mass-customization and rapid-prototyping principles to the process used to create CCC’s. This involves automating the basic steps of the process: creating an electronic representation of the seating surface and machining that surface using a computer-controlled (CNC) mill. Similar systems have been put in place to automate a variety of processes, from the creation of custom orthotics for footwear to the design and creation of impeller wheels [4]. Such a system would be capable of producing a suitable custom-contoured cushion in minutes or hours rather than weeks or months.
Side Impact Pediatric Injury Studies
Authors: Sances Anthony , Harcourt John , Kumaresan Srirangam
Published: November 2021

Side impact injury and intrusion has been studied for many decades. According to the National Highway Traffic Safety Administration (NHTSA) side impacts account for 30% of all fatalities and 34% of all serious injuries to passenger car occupants [1,2]. A discussion of the Federal Motor Vehicle Safety Standard (FMVSS) 214 on the impactor, impacted vehicle and occupant motion is reported [3].
Applications of a Microfluidic Amplifier As a Bi-Stable Device in an Oxygen Delivery System
Authors: Macia Narciso F.
Published: November 2021

This paper presents the application of a planar, fluid amplifier which has been used as a bi-stable element in an intermittent, oxygen delivery device. The proportional fluid amplifier is made bi-stable by positive feedback: by connecting its outputs to its inputs, through a fluid resistor network. The fluidic fluid amplifier is the device that gave birth to the fluidics technology, in 1959, at the former Harry Diamond Laboratories (U.S. Army).
Mechanical Loading Modulates Gene Expression in Chondrocyte-Seeded Agarose Hydrogels
Authors: Lo Sansan S. , Mauck Robert L. , Seyhan Sara L. , Palmer Glyn D. , Mow Van C. , Hung Clark T.
Published: November 2021

A successful tissue engineered articular cartilage construct needs to possess mechanical, biochemical, and histological features similar to that of native cartilage in order to serve its load-bearing function. Agarose is a suitable scaffold material for chondrocyte cultures (1,2), allowing long-term maintenance of cell phenotype and the elaboration of a functional cartilage-like matrix. This culture system facilitates further elucidation of the roles of matrix and cell-matrix interactions in the regulation of chondrocyte response to mechanical loads. We have previously shown (3) that mechanical loading at a physiologic frequency can increase the rate of matrix deposition, increasing mechanical properties of the tissue engineered constructs (∼21 fold increases in HA over day 0 with loading vs. ∼4 fold increases for free swelling controls). We have also shown that dynamic loading of transiently transfected chondrocytes in agarose hydrogels for 1 hour at 10% strain increased aggrecan promoter activity by ∼1.5 fold (4). In this study we sought to further characterize the short term response of chondrocytes to static load (by measuring aggrecan promoter activity) and the effects of dynamic compression on aggrecan gene expression over a longer (3 day) culture period (by monitoring mRNA levels). Monitoring matrix gene expression during early times of culture, when there is little matrix accumulation and the cells deform directly with the matrix (5), may provide insights into cellular responses to strain and allow for the optimization of cartilage bioreactor conditions.
Genetic Manipulation of Adhesion Protein Expression to Regulate Tissue Remodeling
Authors: Phillips Jonathan A. , Roy Kanaklata , Imbalzano Anthony N. , Bonassar Lawrence J.
Published: November 2021

Physical forces play an essential role in life. Stimulating living cells or tissues with mechanical cues can conjure a myriad of biochemical and biophysical responses. [1,2,3] It is well known that mechanical cues, such as gravity, are important in proper tissue development and maintenance. [4] Likewise, mechanical cues have proven to be essential when engineering living tissue. [5] It has been shown that giving mechanical input to engineered load-bearing tissues will often result in a product more closely resembling the native tissue. [5,6] In contrast, studies done in the microgravity environment of outer space have shown that a loss of the constant mechanical input of gravity will result in loss of tissue mass. [7,8,9] Tissue engineering in microgravity systems has also resulted in “mechanically inferior” tissue. [10] It is now know that feedback from cellular mechanoreceptors is critical for proper development, maintenance, and remodeling of tissues. Actual mechanisms and biochemical pathways involved in mechanotransduction have not been fully elucidated and are subjects of intensifying research.
A Novel Approach to Modeling Mechanical Response of a Cell to External Loading
Authors: Venkatesan Vidhyashankar , Mukherjee Nilay
Published: November 2021

The cell is modeled as a fluid filled bag. The cytoskeletal elements radiate out from the center of the cell and attach to the cell membrane. The fluid pressure in the cell causes the membrane and the cytoskeletal elements to be in pretension. Using finite element methods, we show that by relatively small changes in the membrane dimensions, cytoskeletal properties and by reorganizing cytoskeletal structure, a cell can change its bulk modulus by two orders of magnitude. This approach combined with appropriate experiments can be used to model how cells respond and remodel in response to mechanical loads.
Nanomechanics Studies of Biomolecules Using Optical Tweezers
Authors: Stott Shannon , Williams Carrie , Bao Gang
Published: November 2021

Although many proteins in human cells have been identified, the structure-function relationships for most of them remain unknown. For example, protein motors such as kinesin and dynein were identified a long time ago but the exact mechanisms driving the motors are still elusive. Further, many protein molecules exhibit complex conformational dynamics which plays an important regulatory role in their functions. While it was common knowledge that DNA forms a double helix and that the helix is unwound by enzymes for transcription, the forces required to untwist the DNA was uncovered just recently. In carrying out nanomechanics studies of biomolecules such as DNA and proteins, we hope to answer some of the fundamental questions and more generally, to characterize the mechanical behavior of single molecules. The characteristics we wish to define include how a protein molecule deforms, unfolds, responds to a force and generates a force. Most proteins are small (1–100 nm) and the amplitudes of their deformation are even smaller, preventing them from being visible to a light microscope. Atomic force microscopy (AFM) can be used to measure the force-extension curves of proteins but the use of AFM is limited by the relatively high thermal noise. Thus, we elected to build an optical tweezers, a measurement system that can accurately measure forces in the range of 0.5–50 pN.
Constrained Multi-Body Dynamic Analysis of Shaft and Bearing Systems
Authors: Hoffmann F. , Rahnejat H.
Published: November 2021

A generic method of formulation for shaft and bearing systems in Lagrangian dynamics is described. The method incorporates combined lateral, axial and rotational rigid body dynamics of such systems, incorporating the restraining action of bearing supports through rolling element to races contact forces. For an example, the case of a horizontal dry vacuum pump is used. The vibration spectra obtained agree well with those encountered in practice.
On the Hamiltonian Formulation of Thin Free Liquid Sheets
Authors: Li Zhi
Published: November 2021

A Hamiltonian model is used to study the nonlinear distortion of thin free planar liquid sheets. A systematic asymptotic expansion procedure with the fluctuating value of the sheet velocity as the small parameter is developed for the propagation of long waves on liquid sheets. The first and second order systems of nonlinear evolution equations are derived.
Application of Neural Network Friction Component Model in Automotive Drivetrain Simulations
Authors: Cao M. , Wang K. W. , Fujii Y. , Tobler W. E.
Published: November 2021

In this research, an advanced hybrid neural network (AHNN) friction component model is integrated with an automotive drivetrain model for system simulations. The AHNN model accurately predicts the dynamic behaviors of transmission friction components over a broad operating range. It also allows variable sampling time steps in a numerical integration process. The AHNN model is trained using experimental data obtained from a powertrain dynamometer test stand. Since typical dynamometer measurements are acquired at locations away from friction components, a backtracking algorithm is developed to evaluate friction component torque during engagement. The trained AHNN model, together with a comprehensive drivetrain model, is implemented to simulate up-shifting process of an automatic transmission system under various operating conditions, including different oil temperature and engine throttle levels. Simulation results demonstrate that the AHNN friction component model can be effectively utilized as a part of drivetrain model to accurately predict transmission shift dynamics.