bluuebunny/crossref_metadata_2025 huggingface dataset:
Non‐linear relationship between hyperpolarisation and relaxation enables long distance propagation of vasodilatation
Authors: Wölfle Stephanie E. , Chaston Daniel J. , Goto Kenichi , Sandow Shaun L. , Edwards Frank R. , Hill Caryl E.
Published: March 2011

Non‐technical summary  Microvascular dilatations initiated locally in metabolically active tissues spread rapidly upstream, with little attenuation, to larger vessels whose relaxation results in the necessary increases in local blood flow. While this rapidly spreading response occurs due to the propagation of hyperpolarisation through gap junctions, it is not understood why the dilatation does not attenuate unless a regenerative electrical mechanism is involved. We show in skeletal muscle arterioles in vivo that no such regenerative electrical phenomenon exists. Instead, the local dilatation spreads without attenuation because the initial hyperpolarisation is supramaximal and the impact of voltage on dilatation is restricted to a narrow voltage window near the resting membrane potential. Knowledge of this mechanism increases our understanding of the processes which control blood flow to organs and explains how these processes can be compromised in diseases in which endothelial function is reduced.
Calcium‐activated non‐selective cation currents are involved in generation of tonic and bursting activity in dopamine neurons of the substantia nigra pars compacta
Authors: Mrejeru Ana , Wei Aguan , Ramirez Jan Marino
Published: March 2011

Non‐technical summary  The loss of dopamine‐containing neurons within the substantia nigra has been implicated in Parkinson's disease. Thus, the question why these neurons are particularly vulnerable to excitotoxicity has received considerable attention. Under physiological conditions dopamine neurons can generate a burst of activity that seems to require NMDA receptors and that is activated by high frequency glutamatergic inputs. Here, we show in a brain slice preparation of mice that NMDA receptor activation further excites the neurons by recruiting a calcium‐activated non‐selective cation current (ICAN) and we hypothesize that ICAN is specifically mediated by a transient receptor potential (TRP) channel. We used RT‐PCR methods to confirm expression of TRPM2 and TRPM4 mRNA in substantia nigra pars compacta. We propose that ICAN is selectively activated during burst firing to boost NMDA currents and allow plateau potentials. This boost mechanism may render DA cells vulnerable to excitotoxicity.
Neural mechanism of activity spread in the cat motor cortex and its relation to the intrinsic connectivity
Authors: Capaday Charles , van Vreeswijk Carl , Ethier Christian , Ferkinghoff‐Borg Jesper , Weber Doug
Published: March 2011

Non technical summary  The motor cortex (MCx) is an important brain region that initiates and controls voluntary movements. Neurons in MCx are anatomically connected by recurrent (feedback) networks. This connectivity pattern allows neurons to communicate reciprocally with each other potentially over distances of 6–7 mm. However, how far such neural activity is actually communicated was not known. We found that the activity of a small cortical point, about 0.4 mm in radius, activates a surrounding territory of approximately 7.22 mm2 in area. This is smaller than the area covered by the anatomical connections, indicating the existence of mechanisms that limit the spread of activity. Nonetheless, such an area contains the representations of a variety of muscles spanning several joints, from digits to shoulder. These results support the hypothesis that the MCx controls the forelimb musculature in small synergistic groups, rather than singly and separately. Understanding motor cortical physiology is important for the design of neuro‐prosthesis to interface the brain to paralysed muscles.
The expression of thyroid hormone transporters in the human fetal cerebral cortex during early development and in N‐Tera‐2 neurodifferentiation
Authors: Chan S.‐Y. , Martín‐Santos A. , Loubière L. S. , González A. M. , Stieger B. , Logan A. , McCabe C. J. , Franklyn J. A. , Kilby M. D.
Published: March 2011

Non‐technical summary  Thyroid hormones are important in brain development and they enter cells through thyroid hormone transporters at the cell membrane. Thyroid hormone transporters are thought to play an important role since gene defects in one of these transporters, MCT8, have been associated with severe mental retardation. This paper describes the expression of a range of thyroid hormone transporters in the human fetal brain during early pregnancy, and suggests that these transporters could regulate the supply of thyroid hormones into brain cells from very early in development. Surprisingly, the reduction of thyroid hormones and MCT8 expression do not affect the differentiation of an unspecialised cell to a specialised human nerve cell in the brain. Thyroid hormones and MCT8 are thus likely to affect other processes during human brain development. To find out how thyroid hormones influence human fetal brain development requires further research.
Convective Heat Transfer Coefficients in a Building-Integrated Photovoltaic/Thermal System
Authors: Candanedo Luis M. , Athienitis Andreas , Park Kwang-Wook
Published: March 2011

This paper presents an experimental study for the development of convective heat transfer correlations for an open loop air-based building-integrated photovoltaic/thermal (BIPV/T) system. The BIPV/T system absorbs solar energy on the top surface, which includes the photovoltaic panels and generates electricity while also heating air drawn by a variable speed fan through a channel formed by the top roof surface with the photovoltaic modules and an insulated attic layer. The BIPV/T system channel has a length/hydraulic diameter ratio of 38, which is representative of a BIPV/T roof system for 30–45 deg tilt angles. Because of the heating asymmetry in the BIPV/T channel, two average Nusselt number correlations are reported as a function of Reynolds number: one for the top heated surface and the other for the bottom surface. For the top heated surface, the Nusselt number is in the range of 6–48 for Reynolds numbers ranging from 250 to 7500. For the bottom insulated surface, the Nusselt number is in the range of 22–68 for Reynolds numbers ranging from 800 to 7060. This paper presents correlations for the average Nusselt number as a function of Reynolds number; this correlation is considered adequate for the design of BIPV/T systems where forced convection dominates. Local Nusselt number distributions are also presented for laminar and turbulent flow conditions.
Performance Analysis of Full-Film Textured Surfaces With Consideration of Roughness Effects
Authors: Qiu Y. , Khonsari M. M.
Published: March 2011

A mass-conservative algorithm that implements the Jakobsson–Floberg–Olsson cavitation theory is used to predict the performances of seal-like structures and thrust bearings with a dimpled surface texture. The results of a series of simulations for load-carrying capacity, film thickness, dimple depth, dimple density, cavitation pressure, leakage, and friction force are presented, and the relationship between these performance parameters is studied. It is shown that, under the conditions simulated, surface roughness can improve the load-carrying capacity, but its effect is limited.
A Model Based Estimator for Cylinder Specific Air-to-Fuel Ratio Corrections
Authors: Meyer Jason A. , Yurkovich Stephen , Midlam-Mohler Shawn
Published: March 2011

One of the most overlooked and oversimplified components of an engine model used for model based air-to-fuel ratio (AFR) control and/or diagnostics is the exhaust gas dynamics model. Without a proper model of the exhaust system, the mixing of exhaust gases and the dynamic transport delays are challenging to capture accurately, even with a meticulous experimental calibration. By representing the exhaust system with a finite impulse response (FIR) model whose coefficients are based on physical properties, these effects can be predicted accurately and smoothly across the complete range of operating conditions. Through on-line and off-line techniques, this model can markedly improve the performance of both open loop and closed loop AFR control. Because a FIR model has a linear relationship between the input and the output, the input error trajectory can be identified from a single precatalyst oxygen sensor measurement. This technique can be used to supplement the calibration of either the feed-forward or feedback portion of the AFR controller. Additionally, the FIR model can be used for on-line estimation of cylinder imbalance errors. This model based approach to cylinder imbalance estimation has several advantages over the current empirically based methods including robustness and ease of calibration.
Parametric Estimation for Delayed Nonlinear Time-Varying Dynamical Systems
Authors: Deshmukh Venkatesh
Published: March 2011

A constructive algorithm is proposed and illustrated for parametric estimation in delayed nonlinear time-varying dynamic system models from available data. The algorithm uses Chebyshev spectral collocation and optimization. The problems addressed are estimations with complete state vector and incomplete state vector availability. Using an equivalent algebraic description of dynamical systems by Chebyshev spectral collocation and data, a standard least-squares residual cost function is set up for complete and incomplete information cases. Minimization of this cost yields the unique solution for the unknown parameters for estimation with complete state availability, only owing to the fact that the cost function is quadratic and positive definite. Such arguments cannot be made for estimation with incomplete state availability as the cost function is positive definite albeit a nonlinear function of the unknown parameters and states. All the algorithms are presented stepwise and are illustrated using suitable examples.
Spatially Varying Extinction Coefficient for Direct Absorption Solar Thermal Collector Optimization
Authors: Otanicar Todd P. , Phelan Patrick E. , Taylor Robert A. , Tyagi Himanshu
Published: March 2011

Direct absorption solar thermal collectors have recently been shown to be a promising technology for photothermal energy conversion but many parameters affecting the overall performance of such systems have not been studied in depth, yet alone optimized. Earlier work has shown that the overall magnitude of the extinction coefficient can play a drastic role, with too high of an extinction coefficient actually reducing the efficiency. This study investigates how the extinction coefficient impacts the collector efficiency and how it can be tuned spatially to optimize the efficiency, and why this presents a unique design over conventional solar thermal collection systems. Three specific extinction profiles are investigated: uniform, linearly increasing, and exponentially increasing with the exponentially increasing profile demonstrating the largest efficiency improvement.
Analysis of Heat Storage and Delivery of a Thermocline Tank Having Solid Filler Material
Authors: Van Lew Jon T. , Li Peiwen , Chan Cho Lik , Karaki Wafaa , Stephens Jake
Published: March 2011

Thermal storage has been considered as an important measure to extend the operation of a concentrated solar power plant by providing more electricity and meeting the peak demand of power in the time period from dusk to late night everyday, or even providing power on cloudy days. Discussed in this paper is thermal energy storage in a thermocline tank having a solid filler material. To provide more knowledge for designing and operating of such a thermocline storage system, this paper firstly presents the application of method of characteristics for numerically predicting the heat charging and discharging process in a packed bed thermocline storage tank. Nondimensional analysis of governing equations and numerical solution schemes using the method of characteristics were presented. The numerical method proved to be very efficient, accurate; required minimal computations; and proved versatile in simulating various operational conditions for which analytical methods cannot always provide solutions. Available analytical solutions under simple boundary and initial conditions were used to validate the numerical modeling and computation. A validation of the modeling by comparing the simulation results to experimental test data from literature also confirmed the effectiveness of the model and the related numerical solution method. Finally, design procedures using the numerical modeling tool were discussed and other issues related to operation of a thermocline storage system were also studied.
An Energy Approach to Static Balancing of Systems With Torsion Stiffness
Authors: Radaelli Giuseppe , Gallego Juan A. , Herder Just L.
Published: March 2011

Static balance can be applied to improve energy efficiency of mechanisms. In the field of static balancing, a lack of knowledge and design methods exists that are capable of dealing with torsional stiffness. This paper presents a design approach for statically balanced mechanisms, with the focus on mechanisms with torsional stiffness. The approach is graphical of nature and it is based on the requirement of constant potential energy. The first achievements of the presented approach are presented as five conceptual designs of four different types of mechanisms. One of them is developed further into a prototype, which has been tested. The prototype has a correlation coefficient of 0.96 and a normalized mean squared error of 0.12 with respect to the mechanical model of the conceptual design.
Towards a More Complete Understanding of PMN-PT 4 Point Bend Specimen Behavior
Authors: DeGiorgi Virginia G. , Wimmer Stephanie A.
Published: March 2011

ASTM Standard C1161 is often used to determine fracture performance of piezoelectric materials. The basic geometry of C1161 is a four-point beam subjected to mechanical loading. When single crystal PMN-PT was recently subjected to this test unexpected results were observed. Fracture did not occur at the defects incorporated into the specimens nor did failure occur at locations of where maximum stress or strain was predicted by mechanical analyses. Computational tools were then applied to determine piezoelectric material response in this geometry with applied mechanical loading. Conventional finite element codes with piezoelectric material constitutive response using linear behavior models were used. Rather than duplicate the experimental work, the goal of this analysis was to provide insight into the electric fields that would be generated due to mechanical loading of the four-point bend specimen and the resulting variations in stress and deformations. Variation in poling directions is examined. Three different four-point bend configurations are considered. In each specimen the poling direction is aligned with one of the axes of the geometry. The computational study was done as a pre-screening analysis to determine if further understanding of the piezoelectric phenomenon could be expected in a series of experiments of similar design. Experimental work is currently under development based on the computational results of this study. The intent is to used computational analysis to advance understanding to enhance experimental design.
Closing the Loops Without Human Subjects: A Survey of Control Approaches in Simulation of Human-Artifact Interaction
Authors: van der Vegte Wilhelm “Wilfred” F. , Horva´th Imre
Published: March 2011

To include interactions with human users in simulations of the use of products, the most common approach is to couple human subjects to the behavioral product model in the simulation loop using interfaces based on VR and haptics. Replacing human subjects by human models with simulation capabilities could offer a cost-saving alternative. Currently available human models have not yet been deployed this way. This paper explores the possibilities to achieve mutual closed-loop coupling between human models and artifact models for enabling fully software-based interaction simulations. We have not only investigated human control in simulations, but also solutions to include embedded control in artifacts. The paper critically reviews existing (partial) solutions to simulate or execute control behaviors, and to close the control loops we identified in human-artifact interaction simulation. We concluded that closed-loop control of interaction simulations can be achieved by selectively combining existing partial solutions. Inclusion of decision-making appears to be the biggest challenge. Promising solutions are (i) cognitive simulation and (ii) execution of conjectured interactions specified as logical instructions, typically in the form of scenarios. Based on scenarios, which we expect to be more intuitive for designers, a new approach is now being developed.
Design Emerging System by Applying Consumer’s Preference to Designer’s Idea
Authors: Ohshima Kentarou , Aoyama Hideki
Published: March 2011

In recent years, aesthetic design is given increasing importance in the development of products industry with the growing maturity of product functions. The designer is required to reflect consumer needs in the aesthetic design while giving consideration to use and function. Effective techniques enabling design creation based on consumer preference and needs are indispensable. This study thus aims to construct a design support system which can identify various consumer needs and provide ideas to the designer at an early stage in the design process. In the identification of the consumer preferences, it is necessary to also expose vague consumer preferences. The design support system thus also aims to reduce burden on the consumers during consumer survey and expose consumer preference by using the genetic algorithm (a type of Interactive Evolutionary Computing) for the extraction of consumer preference. The authors also propose the use of rough sets and decision rules for analyzing the acquired consumer preference data specifically and effectively, and formulate consumer preference rules. Furthermore, the constructed system is able to generate multiple design solutions automatically by reflecting the consumer preference rules in design solutions created by the designer, and display the generated solutions to the designer.
The Automated Planning for Fixture Location Based on Process Requirement
Authors: Wu Yuguang , Li C. G.
Published: March 2011

This research carries out a systematic investigation on the automation of fixture location planning. A novel classification and representation method of constrained degrees of freedom (DOF) is proposed. Constrained DOFs are classified into four types: linear translation DOF, linear rotation DOF, planar translation DOF and planar rotation DOF, and they are represented in the form of vector. On the basis of the classification and representation, constrained DOFs are automatically obtained from process requirement. By analyzing datum constraint DOF capability and datum location ability, the operation rules of constrained DOF: union, decomposition and coordinate transformation, are established. The approach to the evaluation of datum location ability and the judgment of datum conflict is explored, and the solution of datum conflict and datum location problem is presented. Eventually, the rules of location point layout are formalized.
Performance Indices for Collaborative Serial Robots With Optimally Adjusted Series Clutch Actuators
Authors: Lauzier Nicolas , Gosselin Cle´ment
Published: March 2011

Safety is the first priority when designing robots that are intended to physically interact with humans. New robotics standards state as a condition for collaboration that the robot should be designed so that it cannot exert forces larger than 150[N] at its tool centre point. An effective and reliable way of guaranteeing that this force cannot be exceeded is to place a torque limiter in series with each actuator, thus forming Series Clutch Actuators (SCAs). Since the relationship between the joint limit torques and the achievable end-effector forces is configuration dependent, it is preferable to use adjustable torque limiters. This paper presents a method to optimally control the limit torques of a serial manipulator equipped with adjustable series clutch actuators. It also introduces two performance indices to evaluate the quality of the relationship between the joint limit torques and the achievable end-effector forces. The first one is the ratio of the minimum and maximum force thresholds. Even if it has a strong physical meaning, it is not differentiable everywhere in the workspace and is thus difficult to use in an optimization process based on its gradient. A second index, smooth and expressed in a closed-form, is therefore introduced which is the determinant of the normalized Jacobian matrix post-multiplied by its transposed. Examples of redundant manipulator motion optimization and of collaborative robot architecture optimization using the second index are shown. Finally, the main limitations of the proposed methods and indices are discussed.
Control of a Pneumatic Gantry Robot With Adaptive Neural Network Compensation
Authors: Taghizadeh Sasan , Surgenor Brian , Abu-Mallouh Mohammed
Published: March 2011

In a previous paper, the application of a pneumatic gantry robot to contour tracking was examined. A hybrid controller was structured to control the contact force and the tangential velocity, simultaneously. Performance was found to be limited by system lag and Coulomb friction. A neural network (NN) compensator was subsequently developed to counter both effects. Simulation results for straight and curved edge workpieces demonstrated the effectiveness of the NN compensator. This paper validates the results experimentally, highlights the tuning issues associated with an adaptive NN compensator, and confirms the capabilities of a pneumatic gantry robot.
Multivariable Control of an Over-Head Crane System Based on Entire Eigen-Structure Assignment
Authors: Moradi Hamed , Hajikolaei K. Haji , Bakhtiari-Nejad Firooz , Alasty Aria
Published: March 2011

Motion and stabilization control strategies are required to improve positioning accuracy, transportation time and swing angle of an overhead crane system. In this paper, a controller is designed to enhance both efficiency and safety and to extend the system application to other engineering fields. An over-head crane is modeled as a linear time invariant (LTI) system with two degrees of freedom. Trolley position and cable angle are the controlled outputs while the force exerted on trolley and torque on the load are the control inputs of the system. After state-space representation of the problem, feedback control is designed for tracking objective. An increase in the overall speed of the system time response corresponds to an increase in the control signal and leads to additional cost. Therefore, developing a code in MATLAB, eigenvalues and eigenvectors of the system are chosen optimally until an appropriate response is achieved; while the gains of control signal remain small.
Static Analysis of a Lumped Mass Cable System
Authors: Masciola Marco D. , Nahon Meyer , Driscoll Frederick R.
Published: March 2011

In this paper, we advance a methodology for obtaining the statics solution of lumped mass cable system. The method presented here is general enough for most cable configurations (slack or taut), and works well for a broad range of cable elasticity. The forces considered acting on the cable are due to elasticity, weight, buoyancy and aero/hydrodynamics. A shooting method is used to generate the statics solution for the lumped mass model and thus find the equilibrium position of all the cable nodes. This approach converges onto a solution more efficiently compared to other conventional approaches. In particular, for the two-dimensional problem, the solution is obtained from a set of two equations, regardless of how fine the cable discretization is.
Addressing Data Collection Problems in Web-Mediated Surveys
Authors: Meese Nicholas , Swart Juani , Vidgen Richard , Powell Philip , McMahon Chris
Published: March 2011

Web-based approaches are increasingly being used for carrying out surveys, for example in research or to obtain user feedback in product and systems development. However, the drawbacks of web surveying are often overlooked. Errors in web surveys can be related to sampling, coverage, measurement, and non-response issues. Low response rates and non-response bias are particularly important for web-based surveys. This paper reports on a web-based survey in an international engineering consultancy, aimed at eliciting feedback on the development of systems to support sustainable engineering, that produced a low response rate. To investigate the reasons for this, a follow-up survey was conducted by telephone. The majority of those questioned were unaware of the original survey. The telephone survey showed that reasons for non-completion by those who were aware may be categorized as resources issues, relevance, and fatigue. Differences between those who were aware of the original survey and those who were not are explored and a gap is found between action and intention, i.e. good intentions to complete a survey are very unlikely to translate into action and completed surveys. The paper concludes with practical guidance for administering web-based surveys and observations on the merits of telephone surveys.
Investigation of Wire Failure Effect on Stiffness Maps of Planar Wire-Actuated Parallel Manipulators
Authors: Moradi Amir , Notash Leila
Published: March 2011

In the work presented, the complete form of stiffness of planar wire-actuated parallel manipulators is formulated. The differential form of the static force and moment equations is used to formulate the symmetric stiffness matrix of the manipulator. Stiffness maps over the workspace of manipulators about and along different directions are developed and the effect of wire failure on the stiffness maps is investigated. Some strategies for retrieving the lost stiffness after the wire failure are discussed. The effects of the presented strategies on stiffness maps over the workspace of example planar wire-actuated manipulators are presented.
Prioritizing Engineering Characteristics of Product-Service System Using Analytic Network Process and Data Envelopment Analysis
Authors: Geng Xiuli , Chu Xuening , Xue Deyi , Zhang Zaifang
Published: March 2011

Product-service system (PSS) approach has emerged as a competitive strategy to impel manufacturers to offer a set of products and services as a whole. A new three-domain PSS conceptual design framework supporting engineering design methodology is proposed in this research. Identification of the critical parameters in these domains plays an important role. Engineering characteristics (ECs) in the functional domain, which include product-related ECs (P-ECs) and service-related ECs (S-ECs), are identified by translating customer requirements (CRs) in the customer domain. Quality function deployment (QFD) is used to implement this translation process. Prioritizing ECs is a crucial issue in achieving the optimal PSS planning. First, to consider complex dependency relationships between and within CRs, P-ECs and S-ECs, the analytic network process (ANP) approach is integrated in QFD to determine the initial importance weights of ECs. Second, the data envelopment analysis (DEA) approach is applied to adjust the initial weights of ECs considering requirements of the manufacturers. In order to deal with the vagueness, uncertainty and diversity in decision-making, the fuzzy set theory and group decision-making technique are used in the supermatrix approach of ANP in the first phase. A case study is carried out to demonstrate the effectiveness of the developed prioritizing approach for ECs in PSS conceptual design.
Direct Displacement Synthesis Method for Shape Morphing Skins Using Compliant Mechanisms
Authors: Berglind Luke A. , Summers Joshua D.
Published: March 2011

This paper presents a direct displacement synthesis method for the design of shape morphing skin structures using compliant mechanisms. The objective of this method is to design a skin structure that will deform to a desired final shape when acted on by a specific load. The method utilizes a ground structure geometry which can facilitate variable bending stiffness along the length of the skin using compliant spring members. Synthesis procedures involve the use of direct displacement to determine how the bending stiffness of the skin must vary to produce the desired shape change. The direct displacement synthesis method differs from other compliant mechanism synthesis methods found in literature, such as pseudo-rigid-body and continuum structure optimization, in the approach taken to solve for the unknown variables in the system. By using direct displacement to determine how the structure must respond to a specific load to achieve the desired shape change, the unknown variables within the system can be extracted directly without the use of optimization techniques.
Basic Study of Autologous-Bone-Replaceable Artificial Bone Fabrication With Porosity Distribution Using Electrolysis
Authors: Murakami Tamotsu , Hamasaki Yuki
Published: March 2011

Recently, the use of bioresorbable materials (e.g., β-tricalcium phosphate (β-TCP)) has enabled the development of autologous-bone-replaceable artificial bones that are degraded and resorbed, i.e., replaced with autologous bone, when placed inside the human body for a sufficiently long duration. Although such autologous-bone replaceability requires high porosity of the artificial bone to promote the ingression of blood vessels and cells, the high porosity reduces the mechanical strength, which leads to disadvantages such as possible fracture after bone substitution surgery. One solution to this problem is to optimally arrange low-porosity portions for mechanical strength and high-porosity portions for autologous-bone replaceability in solid artificial bones. Commercially available artificial bones typically have fixed shapes such as a rectangular parallelepiped or cylinder. The use of recent solid freeform fabrication technologies, however, has enabled solid artificial bones with various shapes to be customized for individual medical cases. In this paper, the authors propose a solid freeform fabrication method for autologous-bone-replaceable artificial bones with a porosity distribution. A β-TCP porous artificial bone can be fabricated by placing a slurry consisting of β-TCP powder, water, a peptization reagent and a frother in a mold, drying it to form a solid shape and then sintering it. This β-TCP slurry contains ammonium polyacrylate as the peptization reagent, which is an electrolyte, and ammonia, hydrogen and oxygen gases are produced from its electrolysis. The authors conceived the idea of controlling the foaming of the β-TCP slurry by electrolysis, and of designing and implementing a fabrication system consisting of a fine nozzle with a microscrew for extruding β-TCP slurry as a filament and electrodes for controlling the electrolysis of the slurry. Using this system, we can fabricate a solid shape by drawing two-dimensional sections with the slurry filament and stacking each section, and at the same time vary the porosity by controlling the electric current applied for the electrolysis of the slurry. Using the experimental system, three β-TCP porous samples (approximately 18mm × 18mm × 9mm) of high (71.8%), medium (59.5%) and low (54.6%) porosity are successfully fabricated by applying electric currents of 20mA, 10mA and 0mA, respectively. Then a β-TCP porous sample (approximately 40mm × 10mm × 10mm) with a gradient porosity distribution (from 72.3% to 56.1%) is successfully fabricated by varying the electric current from 0mA to 20mA in a continuous fabrication process. From these results, the authors confirm the efficacy and potential of the proposed approach.
On the Validation of a Differential Variational Inequality Approach for the Dynamics of Granular Material
Authors: Melanz Dan , Tupy Martin , Smith Bryce , Turner Kevin , Negrut Dan
Published: March 2011

The validation of a DVI approach for the dynamics of granular material focuses on comparing the experimental and simulation results of granular flow for two tests in the Chrono::Engine simulation environment. A macro scale validation was previously carried out through examination of granular flow in PBR reactors [1]. For this work, an aluminum rig was designed and fabricated to measure the flow rate of a given amount of micro scale granular material flowing due to gravity through a slit. The flow was initiated by using a Newport UMR8.25 translational stage and Newport LTA-HL precision linear actuator to open and close the slit steadily. Once the slit was open, the weight of the granular material was transmitted to the processor via a router connected to a Cooper LFS242 Tension/Compression Cell (Serial No. 286284) and graphed over time. A model of the flow meter was created in Chrono::Engine and the results were matched to experimental runs by changing the friction coefficient between particles. After the friction coefficient of the particles was determined to be 0.15, several experimental runs with differing slit sizes were run. These flow rates were compared to the weight versus time data that Chrono::Engine output for the corresponding slit size. Runs for gap sizes of 1.5mm, 2.0mm, 2.5mm and 3.0mm were performed with 0.0624 N of granular material, which amounted to approximately 39,000 spheres with 500μm in diameter. These gap sizes corresponded to an experimental flow rate of 1.41E-2 N/s, 2.59E-2 N/s, 4.00E-2 N/s, and 4.44E-2 N/s, and a simulated flow rate of 1.40E-2 N/s, 2.62E-2 N/s, 4.05E-2 N/s, and 4.48E-2 N/s, respectively. Based on this experiment, Chrono::Engine had less than a 2% error in calculating the flow rate of the granular material through a slit. In addition to comparing flow rates, the pile repose angle from the experimental runs was compared to the simulation results. A description of the GPU execution model along with its memory spaces is provided to illustrate its potential for parallel scientific computing. The equations of motion associated with the dynamics of many rigid bodies are introduced and a solution method is presented. The solution method is designed to map well on the parallel hardware, which is demonstrated by an order of magnitude reductions in simulation time for large systems that concern the dynamics of granular material.
The Incredible Egg: Investigating the Design Education Challenges and Complexity of the Egg Drop Project
Authors: Ferguson Scott , Klumpe Heidi , Turner John
Published: March 2011

Designing a system that will protect an egg dropped from a predefined height is a common experience for many K-12 students and undergraduates in engineering. Often presented in the context of the scientific method, results from these experiments are used to teach concepts of impulse, acceleration, and impact modeling. When done in the classroom, students are usually given a box of pre-defined supplies and a small time frame with which to complete the design. But what educational challenges and outcomes can be gathered from this experience when the problem is tackled using the systematic design process? In this paper, outcomes from the various steps of the design process conducted over a six-week research project by two high school students are presented. Results include the generation of a requirements list, the creation of a functional model, results of brainstorming sessions, concept analysis, model validation through experimentation, optimization, and final design testing. Challenges faced during each step of the design process, and the surprising complexity of the problem, are also discussed. Additionally, the challenges associated with teaching design principles to high school students for a multidisciplinary and multiobjective problem are addressed.
Sustainable Distribution Design: Contrasting Disposable, Recyclable, and Reusable Strategies for Packaging Materials Using a Total Cost Analysis With an Illustration of Milk Distribution
Authors: Jayanty Sri Satya Kanaka Nagendra , Sawaya William J. , Johnson Michael D.
Published: March 2011

Engineers, policy makers, and managers have shown increasing interest in increasing the sustainability of products over their complete lifecycles and also from the ‘cradle to grave’ or from production to the disposal of each specific product. However, a significant amount of material is disposed of in landfills rather than being reused in some form. A sizeable proportion of the products being dumped in landfills consist of packaging materials for consumable products. Technological advances in plastics, packaging, cleaning, logistics, and new environmental awareness and understanding may have altered the cost structures surrounding the lifecycle use and disposal costs of many materials and products resulting in different cost-benefit trade-offs. An explicit and well-informed economic analysis of reusing certain containers might change current practices and results in significantly less waste disposal in landfills and in less consumption of resources for manufacturing packaging materials. This work presents a method for calculating the costs associated with a complete process of implementing a system to reuse plastic containers for food products. Specifically, the different relative costs of using a container and then either disposing of it in a landfill, recycling the material, or reconditioning the container for reuse and then reusing it are compared explicitly. Specific numbers and values are calculated for the case of plastic milk bottles to demonstrate the complicated interactions and the feasibility of such a strategy.
Integrating End-of-Life and Initial Profit Considerations in Product Life Cycle Design
Authors: Zhao Yuan , Thurston Deborah
Published: March 2011

Growing concerns from customers and the government about product disposal highlight the necessity of improving product take-back systems to retain the embedded values in disposed products. Progress has been made towards minimizing the cost of the disassembly process. While some progress has been made in improving end-of-life (EOL) value through decision making in the early design stage, contradictive objectives make it difficult to simultaneously optimize initial sales profits and EOL value. In this paper, a mathematical model is developed to integrate end-of-life recovery value considerations with product design decisions. The improvement of component reuse value or recycling value is achieved by linking design decisions in the early design stage with end-of-life decisions in order to maximize total product value across the span of the life cycle. A matrix based representation that can group components into several end-of-life modules with similar end-of-life decisions is also presented. The results are discussed to compare different design alternatives to understand their influence on product lifecycle value. The proposed method is illustrated through an example involving cell phone product design decisions and end-of-life strategies.
Motion and Constraint Ruled Surfaces of the Schatz Linkage
Authors: Cui Lei , Dai Jian S. , Lee Chung-Ching
Published: March 2011

This paper investigates the motion and constraint ruled surfaces of the Schatz linkage by examining their geometric characteristics based on screw system analysis. The paper starts by revealing two assembly configurations in accordance with previous literature and examines the cycle phases of the coupler link. This leads to analysis of the motion ruled surface generated by the directrix along the coupler link with Euclidean invariants. The paper further investigates the screw system and its corresponding reciprocal screw and generates the constraint ruled surface in studying its geometry. The study is based on Euclidean invariants and presents intrinsic characteristics between motion and constraint rules surfaces and geometric parameters, revealing the special property of the Schatz linkage.
Fast, Accurate Models for Predicting the Compliance of Elastic Flexure-Jointed Robots
Authors: Odhner Lael , Dollar Aaron
Published: March 2011

Robot manipulators having elastic links or flexure joints have a number of advantages, especially in simplifying the control of contact with other objects. However, current simplified parametric models of flexure motion do not accurately predict the behavior of these mechanisms under large deflections. This paper presents a “smooth curvature model” of flexure behavior that describes the curvature of a highly flexible member such as a flexure joint using a basis of three orthogonal polynomials. Using this model, we show that it is possible to predict the planar stiffness these mechanisms, even in cases where the deformation of the hinge is too large for the linear Euler-Bernoulli beam bending model. Using both finite element methods and the much less computationally expensive proposed model, numerical results will demonstrate that it is possible to accurately predict the in-plane compliance of a highly flexible mechanism in the presence of an external load. The results of this work are significant because they demonstrate that the behavior of flexure-based robotic mechanisms can be modeled quickly and with few parameters, enabling their use in closed-loop control for situations where collision safety is a concern, and rigorous model-based path planning for obstacle avoidance, among other applications.
Towards Risk as a Tradeable Parameter in Complex System Design Trades
Authors: Van Bossuyt Douglas L. , Wall Stephen D. , Tumer Irem Y.
Published: March 2011

Complex system conceptual design trade studies traditionally consider risk after a conceptual design has been created. Further, one person is often tasked with collecting risk information and managing it from each subsystem. This paper proposes a method to explicitly consider and trade risk on the same level as other important system-level variables during the creation of conceptual designs in trade studies. The proposed risk trading method advocates putting each subsystem engineer in control of risk for each subsystem. A risk vector is proposed that organizes many different risk metrics for communication between subsystems. A method of coupling risk models to dynamic subsystem models is presented. Several risk visualization techniques are discussed. An example is presented based upon a simplified spacecraft model. The risk trading method discussed offers an approach to more thoroughly consider risk during the creation of conceptual designs in trade studies.
A Smart Wheel for Improving the Active Safety of Road Vehicles
Authors: Gobbi M. , Mastinu G. , Rocca G.
Published: March 2011

A new smart wheel has been designed and tested. The smart wheel is able to measure the three forces and the three moments acting at the wheel-ground interface. The wheel is based on an original structural concept and it appears to be simple enough to be implemented in future automobiles. The paper presents the concept, the design issues and the experimental testing of the smart wheel. The structural part is composed basically by three spokes whose deformations (depending on the forces applied to the wheel) are sensed by means of strain gauges. The strain gauges signals can be filtered, amplified and digitally converted before they are transmitted to a remote receiver. Multi-Objective Programming has been used to design the system in order to reduce its mass and to maximise the sensor accuracy. After an accurate calibration phase, a series of experimental tests have been performed. First, the dynamic testing of the sensor has been completed through indoor tests, then the smart wheel has been fitted to a production passenger car. The performance of the smart wheel fits well the need of improving the active safety of automobiles. In other terms, the information given by the wheel, allowing to sense the three forces and the three moments, should lead to considerable improvement of the ABS and ESP/VDC performance with respect to today control logics.
The M1: A Custom Mechatronics Platform for Robotics Education
Authors: Fiene Jonathan P.
Published: March 2011

This paper presents the details of a compact embedded-computing module designed to meet a variety of pedagogical objectives within mechatronics, controls, and robotics. Built around an ATmega32U4 microcontroller, the 1.8 × 4.0 centimeter module has flash memory for program and data storage, 25 general-purpose input/output lines, four timer/counters, 12 channels of 10-bit analog-to-digital conversion, and support for a variety of serial communications protocols, including USB. The unit adapts easily to a solderless breadboard for quick prototyping, and requires only an external 5-volt power source for operation. Furthermore, it can be programmed directly over a USB connection to a computer, thereby eliminating the need for a separate programming device. As a member of the AVR family of microcontrollers, the development tools for the processor are freely available for Windows, Mac, and Linux. When assembled in sufficient quantity, the part cost for each module is approaching $10US, making it a low-cost solution for a variety of tasks. To enable students and professors to explore both the module and the host of application principles, we have chosen to post the design files and documentation on a publicly-accessible wiki, leaving room for collaborative improvements and the sharing of technology with other educational institutions.
Exploring the Meaning of Success in Outsourced Product Development
Authors: Palm William J. , Whitney Daniel E.
Published: March 2011

Research on outsourced product development has focused primarily on the motives behind firms’ decisions to outsource, with less attention paid to the outcomes of those decisions. The few existing academic studies have reported high failure rates, but there is little consensus as to what is meant by “project success” and “failure” and some do not define success at all. Such ambiguity makes comparisons difficult and hinders explanation of observed variation in project outcomes. This paper explores the many meanings of project success in outsourced product development, based on in-depth interviews of thirty design consultants and clients. After reviewing the merits and limitations of each metric, we propose that the client’s willingness to recommend the consultant may be a suitable outcome variable for assessing project outcomes and comparing success rates across diverse projects, companies, and industries. We present preliminary data that suggests client willingness to recommend varies widely and is multimodal in distribution. Finally, we identify several commonly encountered failure modes, i.e., sequences of events that generate discrepancies between client expectations and project deliverables, thereby producing client dissatisfaction.
Compositional Mapping in Dynamic Atomic Force Microscopy in High-Q vs. Low-Q Environments: Effects of Cantilever Nonlinear Dynamics
Authors: Melcher John , Raman Arvind
Published: March 2011

The ability to simultaneously map variations in topography and composition (local stiffness, adhesion, charge, hydrophillicity/phobicity, viscoelasticity) of samples in ambient and liquid environments has made dynamic atomic force microscopy (dAFM) a powerful tool for nanoscale metrology. In ambient and vacuum environments, quality factors (Q-factors) of the fundamental resonance are typically large, and the contrast channels in dAFM are relatively well understood. In liquid environments, however, Q-factors are typically low due to cantilever interactions with the surrounding viscous liquid, which introduces a new class of nonlinear dynamics that is accompanied by new contrast channels, such as, higher harmonic amplitudes and phases. In particular, we find that the interpretation of the traditional contrast channels is quite different in low-Q environments compared to high-Q environments. We present a theoretical investigation of the contrast channels in dAFM in the context of frequency modulation and tapping mode dAFM with an emphasis on low-Q environments.