bluuebunny/crossref_metadata_2025 huggingface dataset:
Feasibility of Describing Joint Nonlinearity in Exhaust Components With Modal Iwan Models
Authors: Roettgen Daniel R. , Allen Matthew S. , Osgood Dan , Gerger Stuart
Published: January 2015

Segalman recently proposed a model for joint nonlinearity in a built up structure in which each mode is treated independently (orthogonality is assumed to be preserved) and with an Iwan model added to each modal degree of freedom to capture the nonlinearity of all of the joints that are active in that mode. Recent works have shown that this type of model can faithfully describe the nonlinearity in simple laboratory structures and in simulations of structures with several Iwan joints in the micro-slip regime. This work explores the validity of these concepts for more complicated structures, each of which is part of a production automotive exhaust system. Where possible, factory gaskets were used and the bolted joints were tightened per the manufacturer’s specifications. Tests were performed on different subassemblies of the exhaust using a modal hammer to excite the structure and accelerometers to measure its response. Mayes & Allen’s ZEFFT algorithm was used to determine which modes were behaving nonlinearly. Then an algorithm based on the Hilbert transform was used to extract the instantaneous frequency and damping for the modes of interest and to fit the behavior to a modal Iwan model. The results show several modes that exhibit small frequency shifts and damping that changes by as much as a factor of two over the range of forces that were employed.
Gyroscope-Free Link Parameter Measurement Using Accelerometers and Magnetometer
Authors: Vikas Vishesh , Crane Carl D.
Published: January 2015

Knowledge of joint angles, angular velocities is essential for control of link mechanisms and robots. The estimation of joint angles and angular velocity is performed using combination of inertial sensors (accelerometers and gyroscopes) which are contactless and flexible at point of application. Different estimation techniques are used to fuse data from different inertial sensors. Bio-inspired sensors using symmetrically placed multiple inertial sensors are capable of instantaneously measuring joint parameters (joint angle, angular velocities and angular acceleration) without use of any estimation techniques. Calibration of inertial sensors is easier and more reliable for accelerometers as compared to gyroscopes.

The research presents gyroscope-less, multiple accelerometer and magnetometer based sensors capable of measuring (not estimating) joint parameters. The contribution of the improved sensor are four-fold. Firstly, the inertial sensors are devoid of symmetry constraint unlike the previously researched bio-inspired sensors. However, the accelerometer are non-coplanarly placed. Secondly, the accelerometer-magnetometer combination sensor allows for calculation of a unique rotation matrix between two link joined by any kind of joint. Thirdly, the sensors are easier to calibrate as they consist only of accelerometers. Finally, the sensors allow for calculation of angular velocity and angular acceleration without use of gyroscopes.
Vibration of a Square Hyperelastic Plate Around Statically Pre-Loaded State
Authors: Breslavskyi Ivan D. , Legrand Mathias , Amabili Marco
Published: January 2015

Static deflection and free nonlinear vibrations of thin square plate made of biological material are investigated. The involved physical nonlinearity is described through Neo-Hookean, Mooney-Rivlin and Ogden hyperelastic laws; geometrical nonlinearity is modeled by Novozhilov nonlinear shell theory. The problem is solved by sequentially constructing the local models that describe the behavior of plate in the vicinity of a certain static configuration. These models are the systems of ordinary differential equations with quadratic and cubic nonlinear terms in displacement, which allows application of techniques used in analysis of thin-walled structures of physically linear materials. The comparison of static and dynamic results obtained with different material models is carried out.
Analytic Solution for Planar Indeterminate Multiple Point Impact Problems With Coulomb Friction
Authors: Rodriguez Adrian , Bowling Alan
Published: January 2015

This work analyzes the effects of the stick-slip transition of planar rigid body systems undergoing simultaneous, multiple point impact with Coulomb friction. A discrete, algebraic approach is used in conjunction with an event-driven scheme which detects impact events. The system equations of motion for the examples considered are indeterminate with respect to the impact forces. Constraints consistent with rigid body assumptions are implemented to overcome the indeterminacy. The post-impact velocities of a system are determined by exploiting the work-energy relationship of a collision and using an energetic coefficient of restitution to model energy dissipation. These developments lead to a unique and energetically consistent solution to the post-impact velocities. A frictionless rocking block example is analyzed as a benchmark case and compared to experimental results to demonstrate the accuracy of the proposed method. Simulation results are also presented for a planar ball example with friction.
Spectral and Modal Behaviour of 3D Timoshenko Gyroelastic Beams
Authors: Hassanpour Soroosh , Heppler G. R.
Published: January 2015

Gyricity is a continuous distribution of embedded angular momentum that is considered intrinsic to the constitutive material of the structure. Gyroelastic beams, a special case of general gyroelastic systems, are analyzed in this paper where the governing equations for a gyrobeam are formulated by employing the simple longitudinal deformation theory, Duleau torsion theory, and Timoshenko bending theory to model the beam elasticity. The obtained gyrobeam model is used to study the spectral and modal behaviour of thick gyroelastic beams.
Mechanical Design and Control of a 2 Degree of Freedom Robotic Hand Rehabilitation Device
Authors: Murphy Patrick , Kong Qing Chao , Mavroidis Constantinos
Published: January 2015

Robotic neurorehabilitation is a rapidly growing field in both research and industry. Robotics offer the ability to create less labor-intensive rehabilitation for therapists, while providing an interactive experience for patients. Furthermore, the ability to implement assistive robotic therapy in the home setting has the potential to increase the frequency of patient rehabilitation sessions while decreasing the overall cost of therapy. Therefore, the design, control, and initial testing of an actuated 2 degree of freedom hand rehabilitation device is presented.

A 2 degree of freedom hand rehabilitation device, named the Navigator, is mechanically capable of assistive or resistive mode exercise for flexion and extension of the fingers, as well as pronation and supination of the wrist. A series elastic actuator incorporating a rack and pinion provides actuation to flexion and extension of the fingers. A belt drive is used to provide actuation to pronation and supination of the wrist. Position and load sensors are integrated into both actuators to provide feedback for the control system.

The implementation of an impedance control system utilizing position, force, and torque feedback is also presented. Automated control results as well as preliminary pilot data of resistive mode exercises are presented. The impedance controller interacts with a virtual environment. Preliminary results of the controller confirm the efficacy of the device’s mechanical design.
Model Based Development of a 3D Printed Biped Robot
Authors: Kim Won Young , Pochiraju Kishore
Published: January 2015

As 3D printing technology becomes more ubiquitous and pervasive, printed robot structures are likely to become popular. However, these 3D printed structures have inherent flexibility which causes link deflections and vibrations that lead to difficulties in maintaining gait and produce instabilities during motion. In this paper a biped robot, realized with 3D printing techniques, was modeled and its gait was simulated under position control. Spring and damper elements are used within powered joints to model the link flexibility. Servos were placed at the joints and an open-loop gait trajectory was executed by posing the robot through a series of servo angles. The gait of the printed robot was designed using the model. The printed robot’s stability and accelerations during the motion were characterized with 3-axis accelerometers and gyroscopes mounted on the robot. The acceleration measurements from the printed robot are then compared with the model behavior.
Dynamic Behavior of Carbon Nanotubes Using Nonlocal Rayleigh Beam
Authors: Askari Hassan , Esmailzadeh Ebrahim , Younesian Davood
Published: January 2015

Forced vibration of carbon nanotubes based on the Rayleigh beam theory in conjunction with Eringen’s nonlocal elasticity is investigated. The governing equation of vibration of carbon nanotube using the above theories is developed. The carbon nanotube is rested on a nonlinear Winkler and Pasternak foundation with the simply-supported boundary conditions. The Gelerkin procedure is utilized to find the nonlinear ordinary differential equation of vibration of system. The differential equation is solved using the multiple scales method in order to investigate the primary resonance of the considered system. The frequency response of the system is obtained and the effects of different parameters, such as the surface effect, position and magnitude of applied force and Pasternak and Winkler foundation, on the vibration behavior of the system are studied. The sensitivity of the amplitude of oscillation of carbon nanotube is depicted with respect to the surface effect. It is shown that the surface effect plays an important role in the forced vibration of the nano-scale structure.
In-Vivo Obstetric Pressure Measurements for Patient-Specific Epidural Simulator
Authors: Vaughan Neil , Dubey Venketesh N. , Wee Michael Y. K. , Isaacs Richard
Published: January 2015

The aim of this study was to measure changing pressures during Tuohy epidural needle insertions for obstetric parturients of various BMI. This has identified correlations between BMI and epidural pressure. Also we investigated links between BMI and the thicknesses and depths of ligaments and epidural space as measured from MRI and ultrasound scans. To date there have been no studies relating epidural pressure and ligament thickness changes with varying Body Mass Indices (BMI).

Further goals following measurement of pressure differences between various BMI patients, were to allow a patient-specific epidural simulator to be developed, which has not been achieved before. The trial has also assessed the suitability of our in-house developed wireless pressure measurement device for use in-vivo. Previously we conducted needle insertion trial with porcine for validation of the measurement system.

Results showed that for each group average pressures during insertion decrease as BMI increases. Pressure measurements obtained from the patients were matched to tissue thickness measurements from MRI and ultrasound scans. The mean Loss of Resistance (LOR) pressure in each group reduces as BMI increases. Variation in the shape of the pressure graphs was noticed between two epiduralists performing the procedure, suggesting each anaesthetist may have a signature graph shape. This is a new finding which offers potential use in epidural training and assessment. It can be seen that insertions performed by the first epiduralist have a higher pressure range than insertions performed by second epiduralist.
Design and Testing of a Novel Stepless Lockable Joint for Use in Reconfigurable Fixtures
Authors: Lu Shengnan , Zoppi Matteo , Zlatanov Dimiter , Ahmad Zeshan , Molfino Rezia
Published: January 2015

Reconfigurable or flexible fixtures, an important element in automotive body-welding assembly lines, can be designed as mechanisms with lockable joints. This paper proposes a new flexible fixture using stepless lockable joints allowing infinitely many configurations, and hence a broad application range and potential. Several conceptual designs of the key component, the lockable joint, are presented. Unlike existing mechanisms, which can lock the joint in a finite number of positions, the proposed solution is a stepless device. Once locked, the joint can resist high torque in both directions. These characteristics of the lockable joint guarantee the performance of the reconfigurable fixture that employs it. The load testing has been performed on the prototype of a revolute joint that can sustain 800 Nm, and the stiffness of a lockable arm which employs two lockable joints is detected.
Development of a Multi-Body Model to Predict the Settling Point of a Seat-Occupant System
Authors: Azizi Yousof , Bajaj Anil K. , Davies Patricia
Published: January 2015

The location of the hip-joint (H-Point) of a seat occupant is an important design specification which directly affects the seat comfort. Most car seats are made of polyurethane foam so the location of the H-Point is dependent on the quasi-static behavior of foam. In this study a multi-body seat-occupant model is developed which incorporates a realistic polyurethane foam model. The seat-occupant model consists of two main components: the seat model and the occupant model. In this study the seat is represented by a series of discrete nonlinear viscoelastic elements. The nonlinear elastic behavior of these elements is expressed by a higher order polynomial while their viscoelastic behavior is described by a global hereditary type model with the parameters which are functions of the compression rate. The nonlinear elastic and viscoelastic model parameters were estimated previously using the data obtained from conducting a series of quasi-static compression tests on a car seat foam sample. The occupant behavior is described by a two-dimensional multi-body model with 5 degrees of freedom. A Lagrangian formulation is used to derive the governing equations for the seat occupant model. These differential equations are solved numerically to obtain the H-Point location. These results are then used to calculate the force distribution at the seat and the occupant interfaces. The effects of different system parameters on the system response and the interfacial pressure distribution are also studied.
Improving Irrigation in Remote Areas: Multi-Objective Optimization of a Treadle Pump
Authors: Santaeufemia Pablo S. , Johnson Nathan G. , McComb Christopher , Shimada Kenji
Published: January 2015

Water-lifting technologies in rural areas of the developing world have enormous potential to stimulate agricultural and economic growth. The treadle pump, a human-powered low-cost pump designed for irrigation in developing countries, can help farmers maximize financial return on small plots of land by ending their dependency on rain-fed irrigation systems. The treadle pump uses a suction piston to draw groundwater to the surface by way of a foot-powered treadle attached to each suction piston. Current treadle pump designs lift water from depths up to 7 meters at a flow-rate of 1–5 liters per second. This work seeks to optimize the design of the Dekhi style treadle pump, which has gained significant popularity due to its simplicity. A mathematical model of the working fluid and treadle pump structure has been developed in this study. Deterministic optimization methods are then employed to maximize the flow rate of the groundwater pumped, maximize the lift height, and minimize the volume of material used for manufacturing. Design variables for the optimization included the dimensions of the pump, well depth, and speed of various parts of the system. The solutions are subject to constraints on the geometry of the system, the bending stress in the treadles, and ergonomic factors. Findings indicate that significant technical improvements can be made on the standard Dekhi design, such as increasing the size of the pump cylinders and hose, while maintaining a standard total treadle length. These improvements could allow the Dekhi pump to be implemented in new regions and benefit additional rural farmers in the developing world.
Identifying Glenoid Geometries Through Radial Basis Functions for Implant Design
Authors: de Vries Charlotte , Parkinson Matthew B.
Published: January 2015

Total Shoulder Arthroplasty is performed on patients to restore range of motion of the shoulder and decrease pain caused by osteoarthritis at the glenohumeral joint. The glenohumeral joint is a slightly unstable ball and socket joint, where muscles hold the humerus in contact with the glenoid, located on the scapula. Improper sizing or alignment of the implant can cause the surgery to fail to restore mobility to the shoulder or only restore mobility for a limited time. Additionally, placement of the glenoid implant on the scapula is complicated by the limited view available during surgery and the deformation of the glenoid caused by osteoarthritis. Implant designs must take into account the large amount of variability present in both intact and osteoarthritic joints. The purpose of this research is to provide a morphable glenoid representation for the scapula to assist with preoperative planning and implant design. CT scans of healthy and osteoarthritic glenoids were provided by Hershey Medical Center for this study. Principal component analysis and radial basis functions are used to represent a range of potential glenoid geometries, both with and without osteoarthritis. This parametric model can be used to guide the design and sizing of implants. This approach should be extensible to the modeling of other bony surfaces, which can improve both implant design and surgical procedure.
ROM Based Problem Formulation in Conceptual Design: Algorithm and Case Study
Authors: Gutierrez Ronaldo , Zeng Yong , Sun Xuan , Tan Suo , Deng Xiaoguang , Zhou Fayi
Published: January 2015

Problem formulations in natural language imply imprecision, ambiguity, incompleteness, conflict and inconsistency between requirements in a design problem. Recursive Object Model (ROM) based problem formulation in conceptual design extracts complete product requirement from design problems structured initially in natural language. Since ROM carries certain semantic and syntactic information implied in natural language, it is used to formulate a design problem through a question asking approach. The scope of this paper is to present an updated algorithm, question templates, rules and detailed procedures to ask generic questions based on ROM representations. Generic questions are needed for the clarification and extension of the meaning of a design problem in order to overcome the imprecisions, ambiguities, conflicts and inconsistencies of problem descriptions in natural language. The updated algorithm, question templates, rules and detailed procedures for asking generic questions are used in a case study to formulate the development of a Total Quality Management system (TQMS).
Correlating Student Motivation to Course Performance in Capstone Design
Authors: Bessette Amanda , Okafor Vitalis , Morkos Beshoy
Published: January 2015

This paper presents the preliminary results of a motivational study of students enrolled in their capstone design course during their senior year in mechanical engineering at the Florida Institute of Technology. Student teams are assigned a project and teams are tasked with completing a design project over a one-year (2 semesters) span. Data is collected during the beginning of the fall semester and during the end of the spring semester. Two methods were used to collect the data of the class. A live interview was conducted for each of the capstone teams. Within this interview, a range of questions are asked to facilitate an understanding of what motivates the student. An adaptation of the Motivated Learning Strategies Questionnaire (MSLQ) survey instrument was also administered to the students to collect quantitative data. The MSLQ framework divides the instruments into two sets of questions to address motivation and learning. Motivation is comprised of three factors: test anxiety, self-efficacy, and intrinsic value. Statistical analysis is performed on the quantitative data to determine significance or correlation between student motivation and performance. Performance is measured through the student’s grade (evaluated by instructor) and peer evaluation (evaluated by team). The analysis is performed through segmenting the sample into international versus domestic, and males versus females; to identify any differences in motivation between the groups. Results indicate there are differences between international and domestic students along all motivational factors. Further, differences are identified between males and females for intrinsic anxiety motivational factors.
Contrast of Repair Capabilities Between Laser Metal Deposition and TIG Welding on Ti-6Al-4V
Authors: Karnati Sreekar , Palepu Sai Aravind , Sparks Todd , Liou Frank , Nedic Cedo
Published: January 2015

Ti-6Al-4V is a popular aerospace alloy employed in various aerospace structures and their critical components. Irrespective of cause, a defect of few cubic millimeters in volume could declare the disposal of a component making it a costly affair. In the current effort, a hybrid approach of additive and subtractive processes was adopted to repair material removal and plastic deformation defects. Laser metal deposition and welding were the additive processes chosen for repair of the defects, and mini-tensile testing was employed as the characterization technique. A two-way statistical analysis was performed on the outputs obtained from the testing to establish the superiority in repair capability for each of the additive processes. The avg. yield strength obtained from laser repaired samples was found to be around 25% more than weld repaired specimens and avg. grain size for the laser repaired specimens was found to be approximately 1/3rd the size from weld repair.
Buckybot: A Robot Based on the Geometry of a Truncated Icosahedron
Authors: Kutzer Michael D. M. , Brown Christopher Y. , Chirikjian Gregory S. , Armand Mehran
Published: January 2015

This paper introduces Buckybot, a novel mobile platform, and investigates its kinematics and preliminary control algorithms. Buckybot is a ground-based platform whose geometry is based on a truncated icosahedron, i.e. a soccer ball with flattened sides. The platform has 20 passive hexagonal faces on which it can stably rest, and 12 rounded pentagonal faces which can be extended linearly to tilt Buckybot. The symmetric geometry of the robot makes it operational in any configuration which is ideal for a variety of deployment scenarios including throwing or dropping. Buckybot currently locomotes using a semi-static tipping gait to move between adjacent hexagonal faces. In this work, we present the design and low-level control of the Buckybot platform, explore the kinematics associated with Buckybot’s method of locomotion, experimentally characterize tipping, and investigate trajectory planning for this new mobile robot. Results demonstrate effective trajectory planning accounting for plan uncertainty.
Incremental Geometric Modeling and Mask Synthesis for Surface Micromachined MEMS
Authors: Li Jianhua , Ling Hao , Du Zhengchun
Published: January 2015

In the design of surface micromachined microelectromechanical systems (MEMS), there is a lack of effective modeling methods to refine the geometry of a MEMS device. This paper presents a method of incremental geometric modeling and mask synthesis for surface micromachined MEMS. In this method, propagation-mapping graphs are introduced to label all the affected entities in one variation operation, according to the characteristic of surface micromachining. Based on the propagation-mapping graphs constructed from a 3D geometric model and its process model, variation propagation and mapping are used to update these models. In order to keep manufacturability of these models, four manufacturability problems caused by variation propagation are analyzed and a manufacturability maintenance method is discussed. Variation propagation and mapping achieve incremental modeling for the geometric model and process model of a MEMS device. This method enables designers to modify a MEMS device in a quick and intuitive way. Finally the method is implemented and some test results are given.
Effects of Mechanical Flexibility and Clearance Size on the Wear at Revolute Joint in the Flexible Multibody Systems
Authors: Zhao Bo , Dai Xudong , Wu Shihao
Published: January 2015

By integrating the procedures of wear prediction with multibody dynamics, this paper proposed a numerical approach for the modeling and prediction of wear at revolute clearance joint in flexible multibody mechanical systems. In the approach, the flexible component was modeled by using absolute nodal coordinate formulation (ANCF)-based element. The clearance joint was modeled as a dry contact pair, in which the continuous contact force model proposed by Lankanrani and Nikravesh was applied to evaluate the normal contact force, and the friction effect was considered using the LuGre friction model. The calculation of wear was performed by an iterative wear prediction procedure based on Archard’s wear model. Using this approach, a planar slider-crank mechanism including a flexible rod and clearance joint was numerically investigated as a demonstrative example. Furthermore, the effects of the flexibility of the mechanism and the clearance size on the wear at clearance joint were also studied.
Regulating Bearing Reactions in Spring-Aided Static Balancing of Linkages Under Constant Loads
Authors: Singh Gaurav , Jorapur Nikhil S. , Ananthasuresh G. K.
Published: January 2015

Minimizing the bearing reactions in statically balanced linkages reduces the loads experienced by the frame; and making the bearing reactions constant in all configurations makes the linkages run smoothly. Current techniques for static balancing of a linkage using only springs and no auxiliary bodies have free parameters to be chosen by the designer. We describe methods that utilize these free parameters to impose additional conditions that make the magnitude of all bearing reactions constant in all configurations. We also show additional conditions that also minimize the constant bearing reactions. The conditions required for constant bearing reactions for a statically balanced planar 1R crank and a statically balanced planar 2R linkage are derived in this paper. These results are then generalized for any planar linkage with revolute joints.

The main contribution of this paper is in overcoming inherent disadvantages of static balancing using only springs. One disadvantage is concerned with large bearing reactions that vary with the configuration of the linkage. The second disadvantage is large pre-load in the balancing springs. The former is addressed in this paper and the latter was addressed in a prior work. In this paper, we show that simultaneous minimization of constant bearing reactions and pre-loads is not always possible. Hence, we discuss a tradeoff between the two as a practical way to regulate bearing reactions and spring loads. Practical examples of linkages are used to illustrate the application of the proposed methods.
Temporally Consistent Simulation of Robots and Their Controllers
Authors: Taylor James R. , Drumwright Evan M. , Parmer Gabriel
Published: January 2015

Researchers simulate robot dynamics to optimize gains, trajectories, and controls and to validate proper robot operation. In this paper, we focus on this latter application, which allows roboticists to verify that robots do not damage themselves, the environments they are situated within, or humans. In current simulations, robot control code runs in lockstep with the dynamics integration. This design can result in code that appears viable in simulation but runs too slowly on physical systems. Addressing this problem requires overcoming significant challenges that arise due both to the speed of dynamic simulation running time (simulations may run 1/10 or 1/100 of real-time or slower) and to the variability of the running times (e.g., the speed of collision detection algorithms depends on pairwise object proximities). These difficulties imply that one must not only slow the control software but also scale controller running speeds dynamically. We describe the numerous architectural and OS-level technical challenges that we have overcome to yield temporally consistent simulation for modeling robots that use only real-time processes, and we show that our system is superior to the status quo using simulation-based experiments.
MR Based Brake-by-Wire System With Self-Energizing and Brake Energy Harvesting Capability
Authors: Yu Liangyao , Liu Xuhui , Ma Liangxu , Zuo Lei , Song Jian
Published: January 2015

Brake-by-wire system is a more compact, more efficient brake system using electromechanical actuators instead of conventional hydraulic actuators. Magneto-rheological (MR) fluid is widely used in damping control due to its outstanding controllable properties. In this paper, an MR based Brake-by-wire system with self-energizing and brake energy harvesting capability was proposed and designed. It combined a typical single-disk-type MR brake with a wedge mechanism for self-energizing purpose, and a generator is employed to conduct regenerative braking and harvest brake energy. The MR brake and generator are located at the inner side of the wheel rim and coupled by compact linkage and axle mechanism. According to the torque analysis of the proposed MR brake, the brake torque was significantly amplified, which means MR fluid can be applied in automotive Brake-by-Wire system with less power consumption. Meanwhile, about 46W output power of the generator can be achieved when braking at an initial vehicle speed of 50km/h. Using a DC/DC convertor, the output power can be used to power the MR brake control circuit or other in-vehicle electronic devices, or charge the on-board low-voltage battery. Simulation results are given according to the proposed design.
Design of Experimental Procedure and Analysis Methods of Small Scale Wind Turbine Blades With Different Geometries
Authors: Alsultan Abdulrahman , Block Andrew Ryan , Burg Trevor James , Vriesman Joshua Neal , Amano R. S.
Published: January 2015

The renewable energy is a promising field, which shows a lot of potential for future energy solutions. The design of the blade shows a lot effects on the efficiency of the wind turbine, and the design parameters governs the performance characteristics. This paper addresses a number of innovative blade designs that was developed by alterations made to the existing conventional straight blade. These blades were extensively studied using computational fluid dynamics (CFD) software, and showed promising results, which was the motive behind this study. We are designing an experiment to study small scale wind turbines, which will enable us to gather data that will explain some differences in power and torque output. These steps will help us to come to a better understanding of some aerodynamic aspects that will impact the performance of each individual blade design. The comparing criteria for this study was the torque generation at the axes of rotation, which can be translated to several parameters, such as energy output, using some theoretical basis equations.
Nonlinear Dynamics of a Beam-Rigid Body Microgyroscope
Authors: Lajimi S. A. M. , Heppler G. R. , Abdel-Rahman E.
Published: January 2015

The nonlinear dynamics of a cantilever-beam-rigid-body MEMS gyroscope near primary resonance are studied by using a shooting method and long time integration. The microsensor includes a square beam carrying an eccentric end-rigid-body rotating about the longitudinal axis and under an electrostatic force. The mathematical model of the system is reduced by using the method of assumed modes. Using a shooting method and long time integration, the dynamic characteristics of the system are investigated and presented in terms of frequency-response plots and force-response curves. The bifurcation points are discussed and the regions of instability are characterized.
Motion Detection Strategies for Epileptic Seizure Patients Based on Inertial Sensor Data
Authors: Asokanthan Samuel F. , Kamalizonouzi Babak , Valiathan Ajay
Published: January 2015

Inquiry of inertial sensory data to monitor and detect seizure sequences in epileptic patients is investigated via experiments and response analysis as well as classification. Experimental motion data incurred from a patient suffering from epileptic seizure as well as a healthy subject employing inertial measurement sensors formed a basis for proposing a suitable detection scheme. The method based on discrete-time Poincare maps in conjunction with third moment has shown promising results. This detection scheme forms the basis of a scheme that can be employed in the classification of activities that encompass an epileptic seizure.
A Mechanical Comparison of Traditional and Minimally Invasive Acetabular Reamers for Total Hip Arthroplasty
Authors: Puma Kari L. , Ehrensberger Mark T.
Published: January 2015

Minimally invasive (MIS) total hip arthroplasty is a recently advanced and popularized technique in orthopaedic surgery. The smaller incision site requires the use of small surgical instruments. The purpose of this study was to perform a biomechanical comparison of the cutting efficiency of traditional acetabular reamers and newly designed minimally invasive reamers for use in total hip arthroplasty. Both types of reamers were tested in two different sample materials, Bonesim™ and RenShape®. This study concluded that the new MIS and the traditional acetabular reamers are comparable in their mechanical performances with respect to the force and torque produced while reaming.
Continuous production of nanostructured particles using spatial atomic layer deposition
Authors: van Ommen J. Ruud , Kooijman Dirkjan , Niet Mark de , Talebi Mojgan , Goulas Aristeidis
Published: January 2015

In this paper, the authors demonstrate a novel spatial atomic layer deposition (ALD) process based on pneumatic transport of nanoparticle agglomerates. Nanoclusters of platinum (Pt) of ∼1 nm diameter are deposited onto titania (TiO2) P25 nanoparticles resulting to a continuous production of an active photocatalyst (0.12–0.31 wt. % of Pt) at a rate of about 1 g min−1. Tuning the precursor injection velocity (10–40 m s−1) enhances the contact between the precursor and the pneumatically transported support flows. Decreasing the chemisorption temperature (from 250 to 100 °C) results in more uniform distribution of the Pt nanoclusters as it decreases the reaction rate as compared to the rate of diffusion into the nanoparticle agglomerates. Utilizing this photocatalyst in the oxidation reaction of Acid Blue 9 showed a factor of five increase of the photocatalytic activity compared to the native P25 nanoparticles. The use of spatial particle ALD can be further expanded to deposition of nanoclusters on porous, micron-sized particles and to the production of core–shell nanoparticles enabling the robust and scalable manufacturing of nanostructured powders for catalysis and other applications.
Method to control deposition rate instabilities—High power impulse magnetron sputtering deposition of TiO2
Authors: Kossoy Anna , Magnusson Rögnvaldur L. , Tryggvason Tryggvi K. , Leosson Kristjan , Olafsson Sveinn
Published: January 2015

The authors describe how changes in shutter state (open/closed) affect sputter plasma conditions and stability of the deposition rate of Ti and TiO2 films. The films were grown by high power impulse magnetron sputtering in pure Ar and in Ar/O2 mixture from a metallic Ti target. The shutter state was found to have an effect on the pulse waveform for both pure Ar and reactive sputtering of Ti also affecting stability of TiO2 deposition rate. When the shutter opened, the shape of pulse current changed from rectangular to peak-plateau and pulse energy decreased. The authors attribute it to the change in plasma impedance and gas rarefaction originating in geometry change in front of the magnetron. TiO2 deposition rate was initially found to be high, 1.45 Å/s, and then dropped by ∼40% during the first 5 min, while for Ti the change was less obvious. Instability of deposition rate poses significant challenge for growing multilayer heterostructures. In this work, the authors suggest a way to overcome this by monitoring the integrated average energy involved in the deposition process. It is possible to calibrate and control the film thickness by monitoring the integrated pulse energy and end growth when desired integrated pulse energy level has been reached.
Parametric study of Y-doped BaZrO3 thin film deposited via pulsed laser deposition
Authors: Chang Ikwhang , Paek Jun Yeol , Cha Suk Won
Published: January 2015

This study investigates the microstructure morphologies of Y-doped barium zirconate (BZY) thin films via a pulsed laser deposition (PLD) process. BZY thin film crystallinity was investigated at different substrate temperatures in a PLD chamber. BZY thin films deposited under 0.013 mbar of oxygen pressure are highly dense regardless of the substrate temperature (25 °C ≤ T ≤ 600 °C), while those deposited at low temperature (T ≤ 200 °C) have porous structures at an oxygen partial pressure of 0.13 mbar. In addition, BZY thin films deposited at 0.26 mbar in low/intermediate temperature ranges (25 °C ≤ T ≤ 400 °C) have porous and columnar structures. Regardless of the chamber pressures, BZY thin films with dense structures can be obtained when the substrate temperature exceeds 500 °C.
A damage constitutive model for rock mass with persistent joints considering joint shear strength
Authors: Liu Hongyan , Yuan Xiaoping
Published: January 2015

Microcracks and joints, two types of flaws that appear in a rock mass, affect both the rock mass strength and deformability. A model that can simultaneously reflect the effect of these two types of flaws on the mechanical behavior of a rock mass with persistent joints is not yet available. This study focusses on a microcracked rock mass with persistent joints and establishes a mechanical model, accounting for the anisotropy in the rock mass strength and deformability induced by the existence of the joints. Firstly, the compound damage variable from the coupling macroscopic and mesoscopic flaws is deduced based on the Lemaitre strain equivalence hypothesis. Secondly, the corresponding damage constitutive model for a jointed rock mass is set up. Thirdly, the joint shear failure criterion is incorporated into the constitutive model to extend the model. Finally, the results of the calculation examples show that the existence of the joint will reduce the strength, enlarge the deformability, and lead to anisotropy of the rock mass. A series of calculation examples and comparisons validate that the proposed model is capable of presenting the joint-induced anisotropy in rock mass strength and deformability, determining its possible failure modes, and reasonably simulating its complete stress–strain relationship.
Comment on “Widespread declines in woodland caribou (Rangifer tarandus caribou) continue in Alberta”
Authors: Harron Donald
Published: January 2015

The 2013 study by Hervieux et al. outlining population trends of Boreal woodland caribou (Rangifer tarandus caribou (Gmelin, 1788)) in Alberta, Canada, utilizes statistical analysis in nonconformance with this analytical method’s limitations and applied data manipulations that biases the result toward a finding of decreasing population trends. The analysis is also based on orders-of-magnitude exaggerations in the precision of field data and failed to take into account the potential for bias toward elevated annual mortality risk associated with the nonrandomized method of selection for collaring female Boreal woodland caribou, and the potential for elevated mortality as a result of the collars themselves. Due to its numerous limitations, it is unlikely that the predictive model outlined in the study is representative of actual trends in populations and is not an approach that can produce reliable population trend estimates.
Identification of Reference Genes in Human Myelomonocytic Cells for Gene Expression Studies in Altered Gravity
Authors: Thiel Cora S. , Hauschild Swantje , Tauber Svantje , Paulsen Katrin , Raig Christiane , Raem Arnold , Biskup Josefine , Gutewort Annett , Hürlimann Eva , Unverdorben Felix , Buttron Isabell , Lauber Beatrice , Philpot Claudia , Lier Hartwin , Engelmann Frank , Layer Liliana E. , Ullrich Oliver
Published: January 2015

Gene expression studies are indispensable for investigation and elucidation of molecular mechanisms. For the process of normalization, reference genes (“housekeeping genes”) are essential to verify gene expression analysis. Thus, it is assumed that these reference genes demonstrate similar expression levels over all experimental conditions. However, common recommendations about reference genes were established during 1 g conditions and therefore their applicability in studies with altered gravity has not been demonstrated yet. The microarray technology is frequently used to generate expression profiles under defined conditions and to determine the relative difference in expression levels between two or more different states. In our study, we searched for potential reference genes with stable expression during different gravitational conditions (microgravity, normogravity, and hypergravity) which are additionally not altered in different hardware systems. We were able to identify eight genes (ALB, B4GALT6, GAPDH, HMBS, YWHAZ, ABCA5, ABCA9, and ABCC1) which demonstrated no altered gene expression levels in all tested conditions and therefore represent good candidates for the standardization of gene expression studies in altered gravity.
The Use of a Dehydrated Amnion/Chorion Membrane Allograft in Patients Who Subsequently Undergo Reexploration after Posterior Lumbar Instrumentation
Authors: Subach Brian R. , Copay Anne G.
Published: January 2015

Background Context. Products that can reduce development of epidural fibrosis may reduce risk for ongoing pain associated with development of scar tissue and make subsequent epidural reexploration easier.Purpose. To evaluate the use of dehydrated human amnion/chorion membrane (dHACM) on the formation of soft tissue scarring in the epidural space.Study Design. Case series.Patient Sample. Five patients having transforaminal lumbar interbody lumbar fusion (TLIF) with posterior instrumentation and implantation of dHACM in the epidural space and subsequent epidural reexploration.Outcome Measures. Degree of scar tissue adjacent to the epidural space at reexploration. Intraoperative and postoperative complications related to dHACM and patient reported outcomes.Methods. The degree of scar tissue adjacent to the epidural space was assessed during the reexploration surgery. Patients’ outcomes were collected using standard validated questionnaires.Results. Four of 5 cases had easily detachable tissue during epidural reexploration. Angiolipoma of 10% was noted in 1 case and 5% in 2 cases. Significant improvements in patient reported outcomes were observed. No intraoperative or postoperative complications occurred.Conclusions.Our findings suggest that dHACM implant during TLIF may have favorable effects on epidural fibrosis and is well tolerated. Further studies with larger cohorts are required to prove our results.
RCCS Bioreactor-Based Modelled Microgravity Induces Significant Changes onIn Vitro3D Neuroglial Cell Cultures
Authors: Morabito Caterina , Steimberg Nathalie , Mazzoleni Giovanna , Guarnieri Simone , Fanò-Illic Giorgio , Mariggiò Maria A.
Published: January 2015

We propose a human-derived neuro-/glial cell three-dimensionalin vitromodel to investigate the effects of microgravity on cell-cell interactions. A rotary cell-culture system (RCCS) bioreactor was used to generate a modelled microgravity environment, and morphofunctional features of glial-like GL15 and neuronal-like SH-SY5Y cells in three-dimensional individual cultures (monotypic aggregates) and cocultures (heterotypic aggregates) were analysed. Cell survival was maintained within all cell aggregates over 2 weeks of culture. Moreover, compared to cells as traditional static monolayers, cell aggregates cultured under modelled microgravity showed increased expression of specific differentiation markers (e.g., GL15 cells: GFAP, S100B; SH-SY5Y cells: GAP43) and modulation of functional cell-cell interactions (e.g., N-CAM and Cx43 expression and localisation). In conclusion, this culture model opens a wide range of specific investigations at the molecular, biochemical, and morphological levels, and it represents an important tool forin vitrostudies into dynamic interactions and responses of nervous system cell components to microgravity environmental conditions.
The Roads to Mitochondrial Dysfunction in a Rat Model of Posttraumatic Syringomyelia
Authors: Hu Zhiqiang , Tu Jian
Published: January 2015

The pathophysiology of posttraumatic syringomyelia is incompletely understood. We examined whether local ischemia occurs after spinal cord injury. If so, whether it causes neuronal mitochondrial dysfunction and depletion, and subsequent energy metabolism impairment results in cell starvation of energy and even cell death, contributing to the enlargement of the cavity. Local blood flow was measured in a rat model of posttraumatic syringomyelia that had received injections of quisqualic acid and kaolin. We found an86±11% reduction of local blood flow at C8 where a cyst formed at 6 weeks after syrinx induction procedure(P<0.05), and no difference in blood flow rate between the laminectomy and intact controls. Electron microscopy confirmed irreversible neuronal mitochondrion depletion surrounding the cyst, but recoverable mitochondrial loses in laminectomy rats. Profound energy loss quantified in the spinal cord of syrinx animals, and less ATP and ADP decline observed in laminectomy rats. Our findings demonstrate that an excitotoxic injury induces local ischemia in the spinal cord and results in neuronal mitochondrial depletion, and profound ATP loss, contributing to syrinx enlargement. Ischemia did not occur following laminectomy induced trauma in which mitochondrial loss and decline in ATP were reversible. This confirms excitotoxic injury contributing to the pathology of posttraumatic syringomyelia.