bluuebunny/crossref_metadata_2025 huggingface dataset:
Follicular trachoma and trichiasis prevalence in an urban community in The Gambia, West Africa: is there a need to include urban areas in national trachoma surveillance?
Authors: Quicke E. , Sillah A. , Harding‐Esch E. M. , Last A. , Joof H. , Makalo P. , Bailey R. L. , Burr S. E.
Published: September 2013

Objectives

Urban areas are traditionally excluded from trachoma surveillance activities, but due to rapid expansion and population growth, the urban area of Brikama in The Gambia may be developing social problems that are known risk factors for trachoma. It is also a destination for many migrants who may be introducing active trachoma into the area. This study aimed to determine the prevalence and risk factors for follicular trachoma and trichiasis in Brikama.

Methods

A community‐based cross‐sectional prevalence survey including 27 randomly selected households in 12 randomly selected enumeration areas (EAs) of Brikama. Selected households were offered eye examinations, and the severity of trachoma was graded according to WHO's simplified grading system. Risk factor data were collected from each household via a questionnaire.

Results

The overall prevalence of trachomatous inflammation–follicular (TF) in children aged 1–9 years was 3.8% (95% CI 2.5–5.6), and the overall prevalence of trichiasis in adults aged ≥15 years was 0.46% (95% CI 0.17–1.14). EA prevalence of TF varied from 0% to 8.4%. The major risk factors for TF were dirty faces (P < 0.01, OR = 9.23, 95% CI 1.97–43.23), nasal discharge (P = 0.039, OR = 5.11, 95% CI 1.08–24.10) and residency in Brikama for <1 year (P = 0.047, OR = 7.78, 95% CI 1.03–59.03).

Conclusions

Follicular trachoma can be considered to have been eliminated as a public health problem in Brikama according to WHO criteria. However, as the prevalence in some EAs is >5%, it may be prudent to include Brikama in surveillance programmes. Trichiasis remains a public health problem (>0.1%), and active case finding needs to be undertaken.
Moduli of products of stable varieties
Authors: Bhatt Bhargav , Ho Wei , Patakfalvi Zsolt , Schnell Christian
Published: September 2013

We study the moduli space of a product of stable varieties over the field of complex numbers, as defined via the minimal model program. Our main results are: (a) taking products gives a well-defined morphism from the product of moduli spaces of stable varieties to the moduli space of a product of stable varieties; (b) this map is always finite étale; and (c) this map very often is an isomorphism. Our results generalize and complete the work of Van Opstall in dimension$1$. The local results rely on a study of the cotangent complex using some derived algebro-geometric methods, while the global ones use some differential-geometric input.
Three-Dimensional Chemiluminescence Imaging of Unforced and Forced Swirl-Stabilized Flames in a Lean Premixed Multi-Nozzle Can Combustor
Authors: Samarasinghe Janith , Peluso Stephen , Szedlmayer Michael , De Rosa Alexander , Quay Bryan , Santavicca Domenic
Published: September 2013

A tomographic image reconstruction technique has been developed to measure the 3D distribution of CH* chemiluminescence of unforced and forced turbulent premixed flames. Measurements are obtained in a lean premixed, swirl-stabilized multi-nozzle can combustor. Line-of-sight images are acquired at equally spaced angle increments using a single intensified charge-coupled device camera. 3D images of the flames are reconstructed by applying a filtered back projection algorithm to the acquired line-of-sight images. Methods of viewing 3D images to characterize the structure, dynamics, interaction and spatial differences of multi-nozzle flames are presented. Accuracy of the reconstruction technique is demonstrated by comparing reconstructed line-of-sight images to measured line-of-sight downstream-view images of unforced flames. The effect of the number of acquired projection images on the quality of the reconstruction is assessed. The reconstructed 3D images of the unforced multi-nozzle flames show the structure of individual flames as well as the interaction regions between flames. Forced flame images are obtained by phase-synchronizing the camera to the forcing cycle. The resulting 3D reconstructions of forced flames reveal the spatial and temporal response of the multi-nozzle flame structure to imposed velocity fluctuations, information which is essential to identifying the underlying mechanisms responsible for this behavior.
Non-Euclidean Stress-Free Configuration of Arteries Accounting for Curl of Axial Strips Sectioned From Vessels
Authors: Takamizawa Keiichi , Nakayama Yasuhide
Published: September 2013

It is well known that arteries are subject to residual stress. In earlier studies, the residual stress in the arterial ring relieved by a radial cut was considered in stress analysis. However, it has been found that axial strips sectioned from arteries also curled into arcs, showing that the axial residual stresses were relieved from the arterial walls. The combined relief of circumferential and axial residual stresses must be considered to accurately analyze stress and strain distributions under physiological loading conditions. In the present study, a mathematical model of a stress-free configuration of artery was proposed using Riemannian geometry. Stress analysis for arterial walls under unloaded and physiologically loaded conditions was performed using exponential strain energy functions for porcine and human common carotid arteries. In the porcine artery, the circumferential stress distribution under physiological loading became uniform compared with that without axial residual strain, whereas a gradient of axial stress distribution increased through the wall thickness. This behavior showed almost the same pattern that was observed in a recent study in which approximate analysis accounting for circumferential and axial residual strains was performed, whereas the circumferential and axial stresses increased from the inner surface to the outer surface under a physiological condition in the human common carotid artery of a two-layer model based on data of other recent studies. In both analyses, Riemannian geometry was appropriate to define the stress-free configurations of the arterial walls with both circumferential and axial residual strains.
An Experimental and Numerical Investigation of Phase Change Electrodes for Therapeutic Irreversible Electroporation
Authors: Arena Christopher B. , Mahajan Roop L. , Nichole Rylander Marissa , Davalos Rafael V.
Published: September 2013

Irreversible electroporation (IRE) is a new technology for ablating aberrant tissue that utilizes pulsed electric fields (PEFs) to kill cells by destabilizing their plasma membrane. When treatments are planned correctly, the pulse parameters and location of the electrodes for delivering the pulses are selected to permit destruction of the target tissue without causing thermal damage to the surrounding structures. This allows for the treatment of surgically inoperable masses that are located near major blood vessels and nerves. In select cases of high-dose IRE, where a large ablation volume is desired without increasing the number of electrode insertions, it can become challenging to design a pulse protocol that is inherently nonthermal. To solve this problem we have developed a new electrosurgical device that requires no external equipment or protocol modifications. The design incorporates a phase change material (PCM) into the electrode core that melts during treatment and absorbs heat out of the surrounding tissue. Here, this idea is reduced to practice by testing hollow electrodes filled with gallium on tissue phantoms and monitoring temperature in real time. Additionally, the experimental data generated are used to validate a numerical model of the heat transfer problem, which is then applied to investigate the cooling performance of other classes of PCMs. The results indicate that metallic PCMs, such as gallium, are better suited than organics or salt hydrates for thermal management, because their comparatively higher thermal conductivity aids in heat dissipation. However, the melting point of the metallic PCM must be properly adjusted to ensure that the phase transition is not completed before the end of treatment. When translated clinically, phase change electrodes have the potential to continue to allow IRE to be performed safely near critical structures, even in high-dose cases.
Bilinear Model Predictive Control of Plasma Keyhole Pipe Welding Process
Authors: Qian Kun , Zhang YuMing
Published: September 2013

Controlled quasi-keyhole plasma arc welding process adjusts the amperage of the peak current to establish a keyhole in a desired time. This keyhole establishment time is the major parameter that controls the consistence of the weld penetration/quality and needs to be accurately controlled. This paper addresses the control of keyhole establishment time during pipe welding around the circumference, in which the gravitational force acting on the weld pool continuously changes. Because of this continuous change, the dynamic model of the controlled process, with the keyhole establishment time as the output and the amperage of the peak current as the input, varies around the circumference during welding. In addition, it is found that this dynamic model is nonlinear. To control this time varying nonlinear process, the authors propose an adaptive bilinear model predictive control (MPC) algorithm. A self-search algorithm is proposed to decouple the input and output in the model to apply the proposed MPC. Experiments confirmed the effectiveness of the developed control system including the adaptive bilinear MPC.
An Experimental Methodology for the Reconstruction of Three-Dimensional Acoustic Pressure Fields in Ducts
Authors: Ferrara Giovanni , Ferrari Lorenzo , Lenzi Giulio
Published: September 2013

The claim for low emission engines, imposed by strict environmental legislation, has prompted the aeronautical industry to reduce both noise emission and pollution by using lean combustion technology. These engines are often affected by acoustic instabilities that can compromise their correct functioning. A 3D acoustic wave field investigation is increasingly relevant for a correct design and comprehension of this kind of phenomena. Numerical codes are widely used for this type of analysis but an experimental validation is still required due to the complexity of the real phenomena involved in acoustic generation and propagation. While the wall acoustic pressure can be easily measured, very few examples of radial measurement for a 3D analysis can be found in research on this subject. This paper presents an example of a radial measurement of a 3D acoustic pressure field by means of a waveguide probe based on a 1/4" pressure microphone. In particular, several probe geometries were designed and calibrated on a specialized test rig. In order to verify the adopted methodology, the acoustic 3D pressure fields of two simplified geometries were measured and compared with those from a theoretical model describing the actual conditions of the test rig.
Infinite-Dimensional Pole-Optimization Control Design for Flexible Structures Using the Transfer Matrix Method
Authors: Krauss Ryan W.
Published: September 2013

This paper presents an approach to control design for flexible structures based on the transfer matrix method (TMM). The approach optimizes the closed-loop pole locations while working directly on the infinite-dimensional TMM model. The approach avoids spatial discretization, eliminating the possibility of modal spillover. The design strategy is based on an iterative process of optimizing the closed-loop pole locations using a Nelder-Mead simplex algorithm and then performing hardware-in-the-loop experiments to see how the pole locations are affecting the closed-loop step response. The evolution of the cost function used to optimized the pole locations is discussed. Contour plots (three dimensional Bode plots) in the complex s-plane are used to visualize the pole locations. A computationally efficient methodology for finding the closed-loop pole locations during the optimization is presented. The technique is applied to a single-flexible-link robot and experimental results show that the optimization procedure improves upon an initial, Bode-based compensator design, leading to a lower settling time.
Side Weld and Bend Method of Manufacturing Compliant Plate Seals
Authors: Adis William E. , Mack Michael , Deo Hrishikesh V.
Published: September 2013

Compliant plate seals are being developed for various turbomachinery sealing applications including gas turbines, steam turbines, aircraft engines, and oil and gas compressors. These seals consist of compliant plates attached to a stator in a circumferential fashion around a rotor. The compliant plates have a slot that extends radially inward from the seal outer diameter and an intermediate plate extends inward into this slot from the stator. This design is capable of providing passive hydrostatic feedback forces acting on the compliant plates that balance at a small tip clearance. Due to this self-correcting behavior, this seal is capable of providing high differential pressure capability and low leakage within a limited axial span, and robust noncontact operation even in the presence of large rotor transients. Manufacturing of compliant plate seals is a challenging problem and in this paper we describe the development of a novel manufacturing technique called side weld and bend (SWAB). The compliant plates are tightly packed with alternating spacer shims in a straight line fixture and welded to a top plate from the side along a straight line. After removal of the spacer shims, the welded assembly is bent to form an arcuate seal of a desired diameter. The side weld and bend (SWAB) manufacturing method reduces distortion, deformity, differential shrinkage, and other associated problems with welding across gaps between adjacent compliant plate seals as is typical in current manufacturing processes.
Interaction Between Swirl Number Fluctuations and Vortex Shedding in a Single-Nozzle Turbulent Swirling Fully-Premixed Combustor
Authors: Bunce Nicholas A. , Quay Bryan D. , Santavicca Domenic A.
Published: September 2013

Flame response to imposed velocity fluctuations is experimentally measured in a single-nozzle turbulent swirling fully-premixed combustor. The flame transfer function is used to quantify the flame's response to imposed velocity fluctuations. Both the gain and phase of the flame transfer function are qualitatively similar for all operating conditions tested. The flame transfer function gain exhibits alternating regions of decreasing gain with increasing forcing frequency followed by regions of increasing gain with increasing forcing frequency. This alternating behavior gives rise to gain extrema. The flame transfer function phase magnitude increases quasi-linearly with increasing forcing frequency. Deviations from the linear behavior occur in the form of inflection points. Within the field, the current understanding is that the flame transfer function gain extrema are caused by the constructive/destructive interference of swirl number fluctuations and vortex shedding. Phase-synchronized images of forced flames are acquired to investigate the presence/importance of swirl number fluctuations, which manifest as fluctuations in the mean flame position and vortex shedding in this combustor. An analysis of phase-synchronized flame images reveals that mean flame position fluctuations are present at forcing frequencies corresponding to flame transfer function gain minima but not at forcing frequencies corresponding to flame transfer function gain maxima. This observation contradicts the understanding that flame transfer function gain maxima are caused by the constructive interference of mean flame position fluctuations and vortex shedding, since mean flame position fluctuations are shown not to exist at flame transfer function gain maxima. Further analysis of phase-synchronized flame images shows that the variation of the mean flame position fluctuation magnitude with forcing frequency follows an inverse trend to the variation of flame transfer function gain with forcing frequency, i.e., when the mean flame position fluctuation magnitude increases, the flame transfer function gain decreases and vice versa. Based on these observations it is concluded that mean flame position fluctuations are a subtractive effect. The physical mechanism through which mean flame position fluctuations decrease flame response is through the interaction of the flame with the Kelvin–Helmholtz instability of the mixing layer in the combustor. When mean flame position fluctuations are large the flame moves closer to the mixing layer and damps the Kelvin–Helmholtz instability due to the increased kinematic viscosity, fluid dilatation, and baroclinic production of vorticity with the opposite sign associated with the high temperature reaction zone.
Reconfiguration and Unified Kinematics Analysis of a Metamorphic Parallel Mechanism With Bifurcated Motion
Authors: Gan Dongming , Dai Jian S. , Seneviratne Lakmal D.
Published: September 2013

This paper introduced a new metamorphic parallel mechanism consisting of four reconfigurable rTPS limbs. Based on the reconfigurability of the reconfigurable Hooke (rT) joint, the rTPS limb has two phases while in one phase the limb has no constraint to the platform, in the other it constrains the spherical joint center to lie on a plane. This results in the mechanism to have ability of reconfiguration between different topologies with variable mobility. Geometric constraint equations of the platform rotation matrix and translation vector are set up based on the point-plane constraint, which reveals the bifurcated motion property in the topology with mobility 2 and the geometric condition with mobility change in altering to other mechanism topologies. Following this, a unified kinematics limb modeling is proposed considering the difference between the two phases of the reconfigurable rTPS limb. This is further applied for the mechanism modeling and both the inverse and forward kinematics is analytically solved by combining phases of the four limbs covering all the mechanism topologies.
Application of Pontryagin’s Maximum Principle to Statistical Process Control Optimization
Authors: Glizer Valery Y. , Turetsky Vladimir , Bashkansky Emil
Published: September 2013

The optimization of a statistical process control with a variable sampling interval is studied. A control performance index is the expected loss, caused by delay in detecting process change. It is to be minimized by a proper choice of a sampling interval. The mathematical model of this problem is a nonstandard variational calculus problem with two types of constraints, an isoperimetric constraint and two geometric constraints. The integrands in the cost functional and the isoperimetric constraint are independent of the derivative of the minimizing function. Therefore, the classical Euler-Lagrange equation approach is not applicable when analyzing this extremal problem. The optimization problem depends on the signal-to-noise ratio parameter. The original problem is transformed to an equivalent optimal control problem. Based on the value of the parameter, the latter is decomposed into two simpler problems, solved by application of Pontryagin’s Maximum Principle. The theoretical results are evaluated by numerical simulations.
Multi-Pulse Chaotic Dynamics of Six-Dimensional Non-Autonomous Nonlinear System for a Composite Laminated Piezoelectric Rectangular Plate
Authors: Hao Wuling , Zhang Wei , Wang Qian
Published: September 2013

The global bifurcation and multi-pulse chaotic dynamics of the four-edge simply supported composite laminated piezoelectric rectangular plate under in-plane and transversal excitations are studied. Based on the model of von Karman type equations for the geometric nonlinearity and the Reddy’s third-order shear deformation theory, the formulas of motion for composite laminated piezoelectric rectangular plate subjected to the in-plane and transversal excitations are derived. Then the Galerkin method is employed to discretize the partial differential equations and the non-autonomous ordinary differential equations with three-degree-of-freedom are derived. The extended Melnikov method is improved to investigate the six-dimensional non-autonomous nonlinear dynamical system in mixed coordinate and the global bifurcation and multi-pulse chaotic dynamics of the composite laminated piezoelectric rectangular plate are studied. The multi-pulse chaotic motions of the composite laminated piezoelectric rectangular plate are found from the numerical simulation which further verifies the result of theoretical analysis.
Free Vibration Analysis of a Beam Under Axial Load Carrying a Mass-Spring-Mass
Authors: Barry O. R. , Zhu Y. , Zu J. W. , Oguamanam D. C. D.
Published: September 2013

This paper deals with the free vibration analysis of a beam subjected to an axial tensile load with an attached in-span mass-spring-mass system. The equations of motion are derived by means of the Hamilton principle and an explicit expression of the frequency equation is presented. The formulation is validated with results in the literature and the finite element method. Parametric studies are done to investigate the effect of the axial load, the magnitude and location of the mass-spring-mass system on the lowest five natural frequencies and mode shapes. The results indicate that the fundamental mode is independent of the tension and the in-span mass. However, a significant change in all modes is observed when the position of the mass-spring-mass is varied.
Nonplanar Dynamics of Fixed-Free Beams With Low Torsional Stiffness
Authors: Carvalho Eulher Chaves , Gonçalves Paulo Batista , del Prado Zenon J. G. N.
Published: September 2013

The three-dimensional motions of a clamped-free, inextensible beam subject to lateral harmonic excitation are investigated in this paper. Special attention is given to the nonlinear oscillations of beams with low torsional stiffness and its influence on the bifurcations and instabilities of the structure, a problem not tackled in the previous literature on this subject. For this, the nonlinear integro-differential equations describing the flexural-flexural-torsional couplings of the beam are used, together with the Galerkin method, to obtain a set of discretized equations of motion, which are in turn solved by numerical integration using the Runge-Kutta method. Both inertial and geometric nonlinearities are considered in the present analysis. By varying the beam stiffness parameters, and using several tools of nonlinear dynamics, a complex dynamic behavior of the beam is observed near the region where a 1:1:1 internal resonance occurs. In this region several bifurcations leading to multiple coexisting solutions, including planar and nonplanar motions are obtained. Finally, the paper shows how the tools of nonlinear dynamics can help in the understanding of the global integrity of the model, thus leading to a safe design.
Coupled Fluidic Vibration Isolators for Rotorcraft Pitch Link Loads Reduction
Authors: Kurczewski Nicolas A. , Scarborough Lloyd H. , Rahn Christopher D. , Smith Edward C.
Published: September 2013

Replacing rigid pitch links on rotorcraft with coupled fluidic devices has the potential to reduce the aerodynamic blade loads transmitted from the blade root to the swashplate. An analytical model of two coupled fluidic isolators is derived and experimentally validated for even and odd harmonic pitch link loads. The system consists of two elastomeric pumpers with fluid chambers that are coupled by an inertia track. This passive fluidic device can be tuned to reduce the transmitted force at a particular odd harmonic of the rotor speed by tailoring the fluid inertance in the inertia track. Benchtop experimental results agree with theory, demonstrating a reduction in odd harmonic pitch link loads of up to 90% compared to the system without fluid. The coupled fluidic isolators also significantly reduce transmitted loads relative to a rigid pitch link over a wide frequency range. Simulation of a UH-60 Blackhawk retrofit example shows potential for targeted odd harmonic excitation loads reduction up to 94% for multiple frequencies without affecting the even harmonic excitation response.
Parametric Modeling: A New Paradigm for Mechanisms Education?
Authors: Mirth John A.
Published: September 2013

The evolution of engineering education is driven, in part, by the tools available. This paper examines how a relatively new tool, that of parametric modeling, can be implemented in the presentation of an introductory course in the design and analysis of mechanisms. The combined graphical and computational power of a parametric modeling system provides an ideal starting point to introduce a variety of common concepts. This paper examines how parametric modeling can be used to analyze mechanism mobility (including degrees-of-freedom, Grashof type, transmission angles, and limits of motion), and velocity (including mechanical advantage) in planar linkages. The use of parametric modeling as a tool for teaching linkage synthesis is also reviewed.

The primary purpose of the paper is to briefly demonstrate the power of parametric modeling and how this tool can form a foundation for mechanism education. The ability to rapidly create and change parametric sketches of mechanisms allows the student much more opportunity to study “what if” scenarios and recognize trends in mechanism analysis and design. The visual and interactive nature of the tool also has excellent compatibility with the highly computer literate background of the modern student. Parametric modeling has the necessary capability to become the paradigm for mechanisms instruction in the 21st century.
Vibration Control of 2DOF Structures Utilizing Sloshing in Square Tanks
Authors: Ikeda Takashi , Harata Yuji , Ninomiya Shota
Published: September 2013

This paper investigates the vibration control of a tower-like structure utilizing a square tuned liquid damper (TLD) when the structure is subjected to horizontal, harmonic excitation. In the theoretical analysis, when the tuning condition, 1:1:1:1, is satisfied, the natural frequencies of the 2DOF structure and two predominate sloshing modes are nearly equal. Galerkin’s method is used to derive the modal equations of motion for sloshing. The nonlinearity of the hydrodynamic force due to sloshing is considered in the equations of motion for the 2DOF structure. Linear viscous damping terms are incorporated into the modal equations to consider the damping effect of sloshing. Van der Pol’s method is employed to determine the frequency response curves which are compared to the numerical simulation. The influences of the excitation frequency, the tank installation angle, and the aspect ratio of the tank cross-section on the response curves are examined. The theoretical results show that whirling motions and amplitude modulated motions (AMMs) including chaotic motions may occur in the structure because swirl motions and Hopf bifurcations followed by AMMs appear in the tank. It is also found that square TLDs work more efficiently than conventional rectangular TLDs, and its performance is further improved when the aspect ratio is slightly increased and the installation angle is equal to zero. Experiments were conducted in order to confirm the validity of the theoretical results.
Fuel Flexible Distributed Combustion for Gas Turbine Engines
Authors: Khalil Ahmed E. E. , Gupta Ashwani K.
Published: September 2013

Distributed Combustion provides significant performance improvement of gas turbine combustors including uniform thermal field in the entire combustion chamber (improved pattern factor), ultra low emission of NOx and CO, low noise, enhanced stability and higher efficiency. Distributed combustion with swirl have been investigated to determine the beneficial aspects of such flows on clean and efficient combustion under simulated gas turbine combustion conditions with close focus on NOx emission. Near Zero emissions of NO and CO have been demonstrated using methane under distributed combustion conditions with heat release intensities commensurable to gas turbine applications. In this paper, distributed combustion is further investigated using both gaseous and liquid fuels with emphasis on pollutants emission and combustor performance with each fuel. Performance evaluation with the different fuels is established to outline the flexibility of the combustor in handling a wide range of fuels with different calorific values and phases with focus on ultra-low pollutants emission. Results obtained on pollutants emission and OH* chemiluminescence for the specific fuels examined at various equivalence ratios are presented. Near distributed combustion conditions with less than 5 PPM of NO emission were demonstrated under novel premixed conditions for the various fuels tested thus outlining the combustor ability to handle different fuels with high performance. Further reduction of NOx can be made with true distributed combustion condition.
DoD Design Cloud Analysis: Securing the Integrated Circuit Design Process
Authors: Gomez Mario N.
Published: September 2013

The use of unsecure foundries has allowed and is still providing a pathway for counterfeit microelectronics into U.S. defense systems. As a result, the Warfighter has been put at risk and a solution is needed. To counter this dilemma, this study looks into the feasibility of creating a Department of Defense (DoD) - wide design cloud that would provide circuit designers with a more secure and economical way of designing and fabricating circuits. The design cloud would include secure communication to trusted foundries along with needed circuit design software. Factors such as security, costs, benefits, and issues are taken into consideration in determining whether the use of the cloud would actually aid the integrated circuit design process.
Measurement of the Scatter of Underplatform Damper Hysteresis Cycle: Experimental Approach
Authors: Gola Muzio M. , dos Santos Marcelo Braga , Liu Tong
Published: September 2013

This work presents the design and the calibration of a test rig specially developed to measure the in-plane forces transferred between the blade platforms through the under-platform damper and their relative displacement. This device is composed of two distinct parts each one representing a platform. One is static and accommodates the load cells which measure the forces in two perpendicular directions; the other produces the in-plane motion, actuated by two piezoelectric stacks. The device reproduces any in-plane relative displacement between two adjacent platforms and measures both the relative motion between platforms and the forces they reciprocally transmit. The damper, placed between the two platform simulators, is loaded by thin wires pulled by dead weights, a way to apply the equivalent of the centrifugal force.

The mechanical features of the rig are described and discussed with their influence on the measurements.

An example application is given. Tests aim at assessing the role of “outer” measured parameters (such as frequency and amplitude of platform-to-platform relative displacement, damper external load (simulating the in-service centrifugal load), damper geometry) on the shape and area of the hysteresis cycle and therefore the damper real and imaginary stiffness components. It is found that equal values for the supposedly governing “outer” parameters may lead to a multiplicity of markedly different hysteresis cycles. The same happens if platform-to-platform force is considered rather than displacement. It is shown how the system evolves through the many possible equilibrium conditions.

It is also shown how the forces between damper and underplatforms are calculated. It is suggested that the measurement of platform-to-platform hysteresis cycles is an effective way to synthetically approach the problem of elastic coupling and energy dissipation between adjacent blades, while detailed knowledge of forces exchanged between the underplatform and damper contact surfaces will be a valuable tool toward the better knowledge of damper micromechanics, perhaps opening a better way to finding damper geometries capable of reducing the scatter of hysteresis cycle shape and area.

Two dampers are investigated, at this stage, in order to assess the dependence of the above said behavior on the damper geometry. Results show that dampers exhibit multiple behaviors under the same input conditions. They may be alarming because they show that the damper-platforms system always converges to the solution with the lowest hysteresis area, a fact which deserves of course deeper investigations.
Expectation Management in a Global Collaboration Project Using a Deterministic Design Approach
Authors: Ito Teruaki , Ichikawa Tetsuo , Hanumara Nevan C. , Slocum Alexander H.
Published: September 2013

Expectation management in product engineering design aims at setting achievable goals for both customers and designers, while leaving room for creativity and passion. This is especially challenging in the global workplace. Using an example of a design project, the Dental Headrest project (DHR), this paper reviews how expectations were managed in a successful, collaborative project between the University of Tokushima (UT) and Massachusetts Institute of Technology (MIT).

The goal of the project was to design an innovative mechanism for the positioning a dental chair headrest so satisfy both the needs of a patient for comfort and a clinician for flexibility and access. The design team was formed with six students from the MIT MechE’s Precision Machine Design class, while the challenge proposed by a UT team of dentists and design engineers.

The team followed a deterministic design procedure inducing understating the challenge and reviewing prior art, strategy and concept generation, detailed module design and fabrication and testing, culminating in presentation and documentation. Through the process was coordinated by online communication and collaborative working spaces which ensured real-time information transfer between the continents. The conclusion was a face-to-face meeting between the two institutions.

This DHR project resulted in an innovative design of headrest adjusting mechanism that was implemented in a prototype. Moreover, the students, faculty and clinicians benefitted from the experience of innovative design collaboration in a multidisciplinary, global team.
In-Vitro Allergy Detection Using a Silver Nanoparticle Modified Nanostructured Biosensor
Authors: Wang Gou-Jen , Liu Yi-Fen , Wu Chia-Che
Published: September 2013

IgE (Immunoglobulin E) in the serum of an asthma patient is a useful index for allergy diseases. In this study, a nanostructured biosensor having uniformly deposited gold nanoparticles (GNPs) as the sensing electrode was used for fast and low serum consuming detection of the IgE in allergy patients’ serum. To enhance the charge transferring efficiency of the biosensor, silver nanoparticles (SNPs) were deposited on the GNP layer. The group 2 allergen, Der p2, was used as the probe to detect IgE. To ensure the specificity of detection, the affinity purified goat anti-Human IgE antibody was further immobilized to the IgE. After immobilizing the anti-IgE on the sensor, the electrochemical impedance spectroscopy (EIS) analysis was implemented to examine the concentration of the target IgE in terms of a Nyquist plot. Blood serum samples with known allergy levels detected by the commercially available ImmunoCAP were used for the verification of the sensor. It is observed that the difference of the charge transfer resistance (ΔRet) between the Der p2 immobilized electrode and the anti-IgE bonded electrode for each individual serum sample closely correlates to its ImmunoCAP class. The blood serum detection results indicate that the presented nanostructured biosensor is able to detect a patient’s allergy level with low sample consumption, short sample preparation time, and quick processing.
The Skewboid Method: A Simple and Effective Approach to Pareto Relaxation and Filtering
Authors: Campbell Matthew I.
Published: September 2013

The concept of Pareto optimality is the default method for pruning a large set of candidate solutions in a multi-objective problem to a manageable, balanced, and rational set of solutions. While the Pareto optimality approach is simple and sound, it may select too many or too few solutions for the decision-maker’s needs or the needs of optimization process (e.g. the number of survivors selected in a population-based optimization). This inability to achieve a target number of solutions to keep has caused a number of researchers to devise methods to either remove some of the non-dominated solutions via Pareto filtering or to retain some dominated solutions via Pareto relaxation. Both filtering and relaxation methods tend to introduce many new adjustment parameters that a decision-maker (DM) must specify.

In the presented Skewboid method, only a single parameter is defined for both relaxing the Pareto optimality condition (values between −1 and 0) and filtering more solutions from the Pareto optimal set (values between 0 and 1). This parameter can be correlated with a desired number of solutions so that this number of solutions is input instead of an unintuitive adjustment parameter. A mathematically sound derivation of the Skewboid method is presented followed by illustrative examples of its use. The paper concludes with a discussion of the method in comparison to similar methods in the literature.
Genetic Algorithms Applied to Affordance Based Design
Authors: Nguyen Manh Tien , Fadel Georges M. , Guarneri Paolo , Mata Ivan
Published: September 2013

Affordance based design (ABD) theory has been presented in several papers and has interested several researchers in the field of design. One criticism of ABD is that the number of affordances identified can be very large, and therefore, the approach may not be amenable for automation. This paper presents a computer based implementation of a process to improve design using affordances.

The Affordance Structure Matrix (ASM) design tool is used to identify relevant relationships between the design parameters of an artifact and the affordances (positive and negative) identified by the user. This initial work investigates multiple existing solutions. A user assigns values to critical affordances that are listed in an ASM by visualizing the possible solutions. The parameter values that describe the architecture of the artifact are encoded and fed to a computer code in addition to the multiple affordance values. A Genetic Algorithm is then used to find an optimal combination of design parameters based on the multiple criteria, the affordances, generating new and better concepts.

The approach is applied to the redesign of a steering wheel. Multiple variants of steering wheels available in the literature are presented to the user. After twenty generations of the genetic algorithm, using an additive weighting method, an optimal solution is found and presented.
Kinematic Synthesis of Planar, Shape-Changing Compliant Mechanisms Using Pseudo-Rigid-Body Models
Authors: Zhao Kai , Schmiedeler James P. , Murray Andrew P.
Published: September 2013

This paper presents a procedure using Pseudo-Rigid-Body Models (PRBMs) to synthesize partially compliant mechanisms capable of approximating a shape change defined by a set of morphing curves in different positions. To generate a single-piece compliant mechanism, flexural pivots and flexible beams are both utilized in the mechanism. New topologies defined by compliant mechanism matrices are enumerated by modifying the components that make up a single degree-of-freedom (DOF) rigid-body mechanism. Because of the introduction of the PRBM for flexural pivots and the simplified PRBM for flexible beams, torsional springs are attached at the characteristic pivots of the 1-DOF rigid-body mechanism in order to generate a corresponding pseudo-rigid-body mechanism. A multi-objective genetic algorithm is employed to find a group of viable compliant mechanisms in the form of candidate pseudo-rigid-body mechanisms that tradeoff minimizing shape matching error with minimizing actuator energy. Since the simplified beam model is not accurate, an optimization loop is established to find the position and shape of the flexible beam using a finite link beam model. The optimal flexible beams together with the pseudo-rigid-body mechanism define the solution mechanism. The procedure is demonstrated with an example in which a partially compliant mechanism approximating two closed-curve profiles is synthesized.
Numerical Bifurcation Analysis of Multimode Impact Oscillations Between a Pantograph and a Rigid Conductor Line
Authors: Yamashita Kiyotaka , Nakayama Tomoaki , Sugiura Toshihiko , Yabuno Hiroshi
Published: September 2013

This paper deals with the numerical bifurcation analysis of the contact loss between a pantograph and an overhead rigid conductor line in a railway current collection system. In the previous study, we modeled this problem as impact oscillations of an intermediate spring-supported beam excited by an oscillating plate. We have already derived the modal interaction relationship equations that describe the velocities immediately after an impact as functions of the velocities before impact for each vibration mode. A numerical calculation using these relationship equations was performed to clarify the impact oscillations with multiple vibration modes. In this paper, we propose a numerical technique based on maps that transform the state of the system at the impact to the subsequent state at the next impact. This numerical method produces stability analyses of the fixed points of the map that describes an impact oscillation with multiple modes. These results can differ surprisingly from the expectations based on a single-mode solution. These results are compared with experiments undertaken in our laboratory, utilizing a thin stainless steel beam. The typical features of impact oscillations, which were theoretically predicted, were confirmed qualitatively.
Nonlinear Dynamics of a Spar Platform
Authors: Gavassoni Elvidio , Gonçalves Paulo Batista , Roehl Deane M.
Published: September 2013

Spar floating platforms have been largely used for deep water drilling, oil and natural gas production and storage of these fluids. In extreme weather conditions such structures may exhibit a highly nonlinear dynamic behavior. In this paper a 2-DOF model is used to study the heave and pitch coupled response in free and forced vibration. Special attention is given to the determination of the nonlinear vibration modes (NNMs). Non-similar and similar NNMs are obtained analytically by direct application of asymptotic methods and the results show important NNM features such as instability and multiplicity of modes. The NNMs are used to generate reduced order models that consist of 1-DOF nonlinear oscillators. It facilitates the parametric analysis and the derivation of important features of the system such as the frequency-amplitude relation associated to each nonlinear mode and resonance curves. The stability is analyzed by the Floquet theory. Bifurcation diagrams and Mathieu charts are used to identify the unstable regions in the force parameter space. The analytical results show good agreement with the numerical solution obtained by direct integration of the equation of motion.
On the Design of a Recumbent Bicycle With a Perspective on Handling Qualities
Authors: Schwab A. L. , Kooijman J. D. G. , Nieuwendijk J.
Published: September 2013

A novel approach to bicycle design for handling qualities is presented. The design method is introduced through a case study in which a new front-wheel drive recumbent bicycle is developed. Since there exists no proper definition nor assessment for bicycle handling qualities, design process is based on comparing the uncontrolled dynamics of the new concepts to an existing design, known to handle well. A prototype was built and road test were conducted to compare the handling before being taken into production. The new design shows comparable handling.
Integrating Immersive Computing Technology With Mixed-Integer Nonlinear Programming for Disassembly Sequence Planning Under Uncertainty
Authors: Behdad Sara , Berg Leif P. , Thurston Deborah , Vance Judy
Published: September 2013

Disassembly sequence planning at the early conceptual stage of design leads to enormous benefits including simplification of products, lower assembly and disassembly costs, and design modifications which result in increased potential profitability of end-of-life salvaging operations. However, in the early design stage, determining the best disassembly sequence is challenging. First, the required information is not readily available and very time-consuming to gather. In addition, the best solution is sometimes counterintuitive, even to those with experience and expertise in disassembly procedures. Integrating analytical models with Immersive Computing Technology (ICT) can help designers overcome these issues. A two-stage procedure for doing so is introduced in this paper. In the first stage, a stochastic programming model together with the information obtained through immersive simulation is applied to determine the optimal disassembly sequence, while considering uncertain outcomes, such as time, cost and the probability of causing damage. In the second stage, ICT is applied as a tool to explore alternative disassembly sequence solutions in an intuitive way. The benefit of using this procedure is to determine the best disassembly sequence, not only by solving the analytic model, but also by capturing human expertise. The designer can apply the obtained results from these two stages to analyze and modify the product design. An example of a Burr puzzle is used to illustrate the application of the method.
The Meaning of “Near” and “Far”: The Impact of Structuring Design Databases and the Effect of Distance of Analogy on Design Output
Authors: Fu Katherine , Chan Joel , Cagan Jonathan , Kotovsky Kenneth , Schunn Christian , Wood Kristin
Published: September 2013

This work lends insight into the meaning and impact of “near” and “far” analogies. A cognitive engineering design study is presented that examines the effect of the distance of analogical design stimuli on design solution generation, and places those findings in context of results from the literature. The work ultimately sheds new light on the impact of analogies in the design process and the significance of their distance from a design problem. In this work, the design repository from which analogical stimuli are chosen is the U.S. patent database, a natural choice, as it is one of the largest and easily accessed catalogued databases of inventions. The “near” and “far” analogical stimuli for this study were chosen based on a structure of patents, created using a combination of Latent Semantic Analysis and a Bayesian based algorithm for discovering structural form, resulting in clusters of patents connected by their relative similarity. The findings of this engineering design study are contextualized with the findings of recent work in design by analogy, by mapping the analogical stimuli used in the earlier work into similar structures along with the patents used in the current study. Doing so allows the discovery of a relationship between all of the stimuli and their relative distance from the design problem. The results confirm that “near” and “far” are relative terms, and depend on the characteristics of the potential stimuli. Further, although the literature has shown that “far” analogical stimuli are more likely to lead to the generation innovative solutions with novel characteristics, there is such a thing as too far. That is, if the stimuli are too distant, they then can become harmful to the design process. Importantly, as well, the data mapping approach to identify analogies works, and is able to impact the effectiveness of the design process. This work has implications not only in the area of finding inspirational designs to use for design by analogy processes in practice, but also for synthesis, or perhaps even unification, of future studies in the field of design by analogy.