bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Nonlinear Mode-Coupling in Ultra Precision Manufacturing Machines: Experimental and Analytical Analyses
Authors: Gupta Sunit K. , Bukhari Mohammad A. , Barry Oumar R. , Okwudire Chinedum E.
Published: November 2020

Recent studies in passively-isolated systems have shown that mode coupling is desirable for best vibration suppression, thus refuting the long-standing rule of mode decoupling. However, these studies have ignored the non-linearities in the isolators. In this work, we consider stiffness nonlinearity from pneumatic isolators and study the nonlinear free undamped vibrations of a passively-isolated ultra-precision manufacturing (UPM) machine. Experimental analysis is conducted to guide the mathematical formulation. The system comprises linearly and nonlinearly coupled in-plane horizontal and rotational motion of the UPM machine with quadratic nonlinear stiffness from the isolators. We present closed-form expressions using the method of multiple scales for two cases viz. the non-resonant case and the bounded internal resonance case. We validate our theoretical findings through direct numerical simulations. For the non-resonant case, we show that the system behaves similar to a linear system. However, for the nearly internal resonance case, we demonstrate strong energy exchange between the modes stemming from nonlinear mode coupling. We further study the effect of nonlinear mode coupling on the vibration isolation performance and demonstrate that mode coupling is not always desirable.
Generative Adversarial Networks With Synthetic Training Data for Enforcing Manufacturing Constraints on Topology Optimization
Authors: Greminger Michael
Published: November 2020

Topology optimization is a powerful tool to generate mechanical designs that use minimal mass to achieve their function. However, the designs obtained using topology optimization are often not manufacturable using a given manufacturing process. There exist some modifications to the traditional topology optimization algorithm that are able to impose manufacturing constraints for a limited set of manufacturing methods. These approaches have the drawback that they are often based on heuristics to obtain the manufacturability constraint and thus cannot be applied generally to multiple manufacturing methods. In order to create a general approach to imposing manufacturing constraints on topology optimization, generative adversarial networks (GANs) are used. GANs have the capability to produce samples from a distribution defined by training data. In this work, the GAN is trained by generating synthetic 3D voxel training data that represent the distribution of designs that can be created by a particular manufacturing method. Once trained, the GAN forms a mapping from a latent vector space to the space of manufacturable designs. The topology optimization is then performed on the latent vector space ensuring that the design obtained is manufacturable. The effectiveness of this approach is demonstrated by training a GAN on designs intended to be manufacturable on a 3-axis computer numerically controlled (CNC) milling machine.
Exploratory Assessment of Design Entrepreneurial Program New Venture Design Experience to Prune Program Activities
Authors: Lugo José E. , Muñoz-Soto Adriana M. , Ríos-Torres Manuel O.
Published: November 2020

The purpose of this paper is to explore the activities of the New Venture Design Experience (NVDE), an entrepreneurial program with an engineering design and marketing focus, and recommend which activities the students report more useful. Currently the entrepreneurial program synchronizes four courses between engineering and business school over the period of two semesters. All courses are to various degrees co-taught. The campus entrepreneurial ecosystem has extracurricular activities that can supplement and or substitute some of the NVDE activities. To explore the impact of entrepreneurial activities (NVDE or ecosystem) a semi-structure interview was designed to uncover which activities were more valuable for the students after the program. For this, fourteen former students from NVDE were interviewed, seven already graduated and seven are still undergraduate students. Initial recommendations are provided towards which activities to scale down.
An Adapted Ethnographic Approach to Social Cognition and Cognitive Apprenticeship in Design Learning Experience
Authors: Milojevic Hristina , Jin Yan , Patel Ananya , Chastain-Howley Perri , Brown Noah K.
Published: November 2020

Design is difficult to teach in traditional ways of lecturing and testing. One defined learning methodology that applies well to design education is project-based learning. In an attempt to better understand the patterns of project-based learning in different design-related programs, we studied three small groups of teachers and students at an innovative academy based out of Shanghai Institute of Visual Art, entitled De Tao Master’s Academy, and compared their education style to that of subjects in regular programs at Shanghai Institute of Visual Art. Our goal was to seek patterns of cognitive apprenticeship in our subjects’ education, and find out (a) if it’s more effective than the traditional approach, and (b) can modelling (i.e. direct replication of learned material) be excluded from a design curriculum.

The information gathered through surveys, interviews and observation were segmented into six categories: (1) self-regulation, (2) creative thinking and thinking styles, (3) incorporation of cognitive apprenticeship model into teaching style, (4) teaching hours vs. self-learning, (5) individual vs. team work preference, and (6) learning environment and teaching resources.

We found that self-regulation was uniformly low throughout the sample, but that De Tao curriculum aimed to increase it over the course of their programs. Most students preferred small teams, with less than 5 students to do assignments and projects with, instead of individually working or working in large teams. Curriculum and interviews indicated De Tao programs had a higher focus on teaching creative thinking and independence, which reflected on design self-efficacy scores of their students when compared with SIVA students. Learning spaces at De Tao were observed to be better, and their instruction constructed close to cognitive apprenticeship. Coaching, scaffolding, articulation and exploration were evident in the design education methods adopted at De Tao. The ethnographic findings were related into an evolved social cognitive design framework, which allowed us to preliminarily contextualize design learning influencers.
Medical Assessment Test of Extrapersonal Neglect Using Virtual Reality: A Preliminary Study
Authors: Lanzoni Daniel , Vitali Andrea , Regazzoni Daniele , Rizzi Caterina
Published: November 2020

The research work presents a preliminary study to create a virtual reality platform for the medical assessment of spatial extrapersonal neglect, a syndrome affecting human awareness of a hemi-space that may be caused by cerebral lesions. Nowadays, the extrapersonal neglect is assessed by using real objects positioned in the space around the patient, with a poor capability of repetition and data gathering. Therefore, the aim of this research work is the introduction of a virtual reality solution based on consumer technology for the assessment of the extrapersonal neglect. By starting from the needs of the involved medical personnel, an online serious-game platform has been developed, which permits to perform a test and a real-time evaluation by means of objective data tracked by exploited technologies, i.e. an HTC Vive Pro head mounted display and ad-hoc IT solutions. The test is based on a virtual environment composed by a table on which twenty objects have been placed, ten on the right side and ten on the left side. The whole 3D virtual environment has been developed using low-cost and free development tools, such as Unity and Blender.

The interaction with the virtual environment is based on voice recognition technology, therefore the patient interact with the application by pronouncing the name of each object aloud. The VR application has been developed according to an online gaming software architecture, which permits to share the 3D scene by exploiting a Wi-Fi hotspot network. Furthermore, the on-line gaming software architecture allows sending and receiving data between the doctor’s laptop and the VR system used by the patient on another laptop. The therapist can see through his/her personal computer a real time faithful replica of the test performed by the patient in order to have a fast feedback on patient’s field of view orientation during the evaluation of 3D objects.

A preliminary test has been carried out to evaluate the ease of use for medical personnel of the developed VR platform. The big amount of recorded data and the possibility to manage the selection of objects when the voice commands are not correctly interpreted has been greatly appreciated. The review of the performed test represents for doctors the possibility of objectively reconstructing the improvements of patients during the whole period of the rehabilitation process. Medical feedback highlighted how the developed prototype can already be tested involving patients and thus, a procedure for enrolling a group of patients has been planned. Finally, future tests have been planned to compare the developed solution with the Caterine Bergero Scale to define a future standardization.
Investigating How Additively Manufactured Parts in Traditionally Manufactured Systems Affect the System Dynamic Properties
Authors: Funke Lawrence , Hylton Blake , Brown Kyle , Sommer Mallory
Published: November 2020

Additive manufacturing (AM) sits poised to make a large impact on the manufacturing sector. Expanding from their original application in rapid prototyping, AM parts are increasingly appearing in full production systems. Using AM parts as replacement parts has recently been touted as a way to save money and increase efficiencies in supply chains. While much work has been done exploring the properties of individual AM parts and how they might affect supply chains, very little has been done to investigate the impact of AM parts as components in a larger system. In fact, there appears to be a lack of research into how AM components affect the system vibrational properties when used as replacement parts. This work sought to answer this question by investigating the effects of replacing a steel bar in a four-bar mechanism with an AM polylactic acid (PLA) bar. Both static and dynamic testing were performed on the system when it was entirely steel, and when one part was replaced with an AM PLA bar. The static results indicated that the dominant modal frequencies of the system were not significantly impacted by the change, possibly suggesting that AM components may be used as replacement parts without concern for shifting modes of vibration. The dynamic data showed that the reduction of mass in the link helped reduce vibrations during operation, suggesting that some care should be taken in matching part properties between AM components and the ones they are replacing. The authors do urge caution in applying and interpreting these results, though, as they are preliminary and require further investigation. Because of this, the paper concludes with suggestions on how to expand and extend these results to fill the gap in the literature identified herein.
A Cable-Driven Parallel Robot With Full-Circle End-Effector Rotations
Authors: Métillon Marceau , Lessanibahri Saman , Cardou Philippe , Subrin Kévin , Caro Stéphane
Published: November 2020

Cable-Driven Parallel Robots (CDPRs) offer high payload capacities, large translational workspace and high dynamic performances. The rigid base frame of the CDPR is connected in parallel to the moving platform using cables. However, their orientation workspace is usually limited due to cable/cable and cable/moving platform collisions. This paper deals with the designing, modelling and prototyping of a hybrid robot. This robot, which is composed of a CDPR mounted in series with a Parallel Spherical Wrist (PSW), has both a large translational workspace and an unlimited orientation workspace. It should be noted that the six degrees of freedom (DOFs) motions of the moving platform of the CDPR, namely, the base of the PSW, and the three-DOFs motion of the PSW are actuated by means of eight actuators fixed to the base. As a consequence, the overall system is underactuated and its total mass and inertia in motion is reduced.
Can Design Teams Be Empathically Creative? A Simulation-Based Investigation on the Role of Team Empathy on Concept Generation and Selection
Authors: Alzayed Mohammad Alsager , Miller Scarlett R. , Menold Jessica , Huff Jacquelyn , McComb Christopher
Published: November 2020

Research on empathy has been surging in popularity in the engineering design community since empathy is known to help designers develop a deeper understanding of the users’ needs. Because of this, the design community has been invested in devising and assessing empathic design activities. However, research on empathy has been primarily limited to individuals, meaning we do not know how it impacts team performance, particularly in the concept generation and selection stages of the design process. Specifically, it is unknown how the empathic composition of teams, average (elevation) and standard deviation (diversity) of team members’ empathy, would impact design outcomes in the concept generation and selection stages of the design process. Therefore, the goal of the current study was to investigate the impact of team trait empathy on concept generation and selection in an engineering design student project. This was accomplished through a computational simulation of 13,482 teams of noninteracting brainstorming individuals generated by a statistical bootstrapping technique drawing upon a design repository of 806 ideas generated by first-year engineering students. The main findings from the study indicate that the elevation in team empathy positively impacted simulated teams’ unique idea generation and selection while the diversity in team empathy positively impacted teams’ generation of useful ideas. The results from this study can be used to guide team formation in engineering design.
Designing Conformal Ferromagnetic Soft Actuators Using Extended Level Set Methods (X-LSM)
Authors: Tian Jiawei , Zhao Xuanhe , Gu Xianfeng David , Chen Shikui
Published: November 2020

Ferromagnetic soft materials (FSM) can generate flexible movement and shift morphology in response to an external magnetic field. They have been engineered to design products in a variety of promising applications, such as soft robots, compliant actuators, or bionic devices, et al. By using different patterns of magnetization in the soft elastomer matrix, ferromagnetic soft matters can achieve various shape changes. Although many magnetic soft robots have been designed and fabricated, they are limited by the designers’ intuition. Topology optimization (TO) is a systematically mathematical method to create innovative structures by optimizing the material layout within a design domain without relying on the designers’ intuition. It can be utilized to architect ferromagnetic soft active structures. Since many of these ‘soft machines’ exist in the form of thin-shell structures, in this paper, the extended level set method (X-LSM) and conformal mapping theory are employed to carry out topology optimization of the ferromagnetic soft actuator on manifolds. The objective function consists of a sub-objective function for the kinematics requirement and a sub-objective function for minimum compliance. Shape sensitivity analysis is derived using the material time derivative and adjoint variable method. Two examples, including a circular shell actuator and a flytrap structure, are studied to demonstrate the effectiveness of the proposed framework.
Optimization of the Compliant Drive Mechanism for a Prosthetic Ankle
Authors: Morrison Tyler , Trainor Dylan , Su Haijun
Published: November 2020

Designers of powered ankle prosthetics face the challenge of synthesizing a suitable means of actuating the ankle joint while keeping prosthetic mass low. The mass of the motor can be reduced by decreasing the amount of torque it must provide which can be accomplished by the design of an effective driving mechanism. In this paper, we outline a method for designing a compliant four-bar mechanism for minimizing the maximum torque required of the motor. We demonstrate a workflow for using human subject walking data to create a prosthetic drive mechanism tailored to the specific bio-mechanics of the dataset, and that the algorithm can be applied across a variety of gaits to create a prosthetic appropriate for both walking and running.
Survey of Digital Tools for the Generation of Ideas
Authors: Rossoni Marco , Bolzan Patrizia , Colombo Giorgio , Bordegoni Monica , Carulli Marina
Published: November 2020

During the concept phase of the industrial design process drawings are used to represent designer’s ideas. More specifically, the designer’s goal is to put the characteristics of ideas on paper so that they can later act as pivotal points in the development of a project. Sketching is also the ideal tool to continue developing an idea: because it is imprecise, the sketch guarantees a high degree of freedom, allowing for changes to made and new ideas to be added.

Another possibility is to translate ideas into sketches on computer tools. This approach can allow the designer to use the created 3D model as the basis for further developing ideas. At the present moment, however, this type of solution is not extensively used by designers during the concept phase. Some researchers have identified technical problems as the reason why these instruments have been unsuccessful on the market, while for others this is related to systems still too rigid to be adapted to the often-diverse needs of designers.

The research presented in this position paper aims at analyzing what has so far been understood with respect to the process of generating ideas, their initial representation in the concept phase and the tools that have been developed so far to support this phase. Consequently, a discussion on these themes and some hypotheses from which develop new research lines will be presented.
Designing Developable Mechanisms From Flat Patterns
Authors: Hyatt Lance P. , Lytle Amanda , Magleby Spencer P. , Howell Larry L.
Published: November 2020

This paper presents tools and methods to design cylindrical and conical developable mechanisms from flat, planar patterns. Equations are presented that relate the link lengths and link angles of planar and spherical mechanisms to the dimensions in a flat configuration. These flat patterns can then be formed into curved, developable mechanisms. Guidelines are established to determine if a mechanism described by a flat pattern can exhibit intramobile or extramobile behavior. A developable mechanism can only potentially exhibit intramobile or extramobile behavior if none of the links extend beyond half of the flat pattern. The behavior of a mechanism can change depending on the location of the cut of the flat pattern. Different joint designs are discussed including lamina emergent torsional (LET) joints. Physical examples are presented.
How Should We Measure Creativity in Design Studies? A Comparison of Social Science and Engineering Approaches
Authors: Miller Scarlett R. , Hunter Samuel T. , Starkey Elizabeth , Ramachandran Sharath , Ahmed Faez , Fuge Mark
Published: November 2020

Design researchers have long sought to understand the mechanisms that support creative idea development. However, one of the key challenges faced by the design community is how to effectively measure the nebulous construct of creativity. The social science and engineering communities have adopted two vastly different approaches to solving this problem, both of which have been deployed throughout engineering design research. The goal of this paper was to compare and contrast these two approaches using design ratings of nearly 1000 engineering design ideas paired with a qualitative study with expert raters. The results of this study identify that while these two methods provide similar ratings of idea quality, there was a statistically significant negative relationship between these methods for ratings of idea novelty. Qualitative analysis of recordings from expert raters’ think aloud concept mapping points to potential sources of disagreement. In addition, the results show that while quasi-expert and expert raters provided similar ratings of design novelty, there was not significant agreement between these groups for ratings of design quality. The results of this study provide guidance for the deployment of idea ratings in engineering design research and evidence for the development and potential modification of engineering design creativity metrics.
Simulation Informed Effects of Solidification Rate on 316L Single Tracks Produced by Selective Laser Melting
Authors: Rawlings A. L. K. , Birnbaum A. J. , Michopoulos J. G. , Steuben J. C. , Iliopoulos A. P. , Ryou H.
Published: November 2020

The formation of sub-grain cellular structures generated during the rapid solidification associated with selective laser melting (SLM) typically yields enhanced mechanical properties in terms of yield stress without considerable loss in ductility when compared with those of wrought material. The extent to which the sub-grain structure appears under standard metallographic preparation shows dependence on multiple systematic conditions. This study identifies the effects of solidification and cooling rate on the grain and sub-grain structure in stainless steel through varying the processing parameters (laser power, scan velocity and spot size) of single tracks on both as-received, small grain and annealed, giant grain substrates. The process parameters, in conjunction with the initial substrate microstructure, are key components in understanding the resulting microstructure. Process parameters, particularly scan velocity, dictate the solidification rate and primary regrowth directions while the initial microstructure and its thermomechanical history dictate the propensity for stored strain energy density. Modeling the thermal process allows for experimental analysis within the context of predicted location within processing space as it pertains to local interface velocity and temperature gradient. Furthermore, it highlights the fact that this specific material system behaves in a manner that is inconsistent with classical solidification theory.
Response Characteristics of Systems With Parametric Excitation Through Damping and Stiffness
Authors: Afzali Fatemeh , Feeny Brian F.
Published: November 2020

Floquet theory is combined with harmonic balance to study parametrically excited systems with combination of both time varying damping and stiffness. An approximated solution having an exponential part with unknown exponents and a periodic term consisting of a truncated Fourier series is considered. When applied to a system with parametric damping and stiffness the analysis shows that combination of parametric damping and stiffness alters stability characteristics, particularly in the primary and superharmonic instabilities comparing to the system with only parametric damping or stiffness. We also look at the initial conditions response and its frequency content. The second excitation harmonic in the system with parametric damping is seen to disrupt the coexistence phenomenon which is observed in the parametric damping case.
Motivating Sustainable Behavior Using Cognitive Interventions in Product Design
Authors: Saadi Jana I. , Yang Maria C.
Published: November 2020

Designing products to encourage sustainable behavior during their use can have significant influence on their total environmental impact. Cognitive interventions can be used to inform users of the importance of sustainable behavior and make users aware of the resources they consume while evoking positive or negative emotions. The first part of this study investigated two methods of cognitive interventions, information (positively and negatively framed) and feedback, and their effectiveness in encouraging users to reduce their napkin consumption in cafés. The number of napkins per transaction illustrated a short-term behavior change for positive information, a longer-term behavior change for negative information, and no change for feedback. In the second phase of this study, a survey was conducted to understand environmental concerns around napkin consumption and emotions and perceived effectiveness of each intervention. Results from 295 valid survey responses showed that the positively framed informative design reminded users to use less napkins in order to save trees and was dominated by positive emotions such as feeling encouraged. The negative information message informed users to use fewer napkins due to the consequences on the environment and was related to negative emotions such as guilt and worry. The feedback intervention’s message was more informative, reminding users that napkins come from trees and the emotions evoked from the intervention closely resembled that of the control. These findings suggest that information and feedback interventions that evoke emotions can be used to promote sustainable behavior.
Structure Synthesis of Parallel Manipulators With Fully Decoupled Projective Motion and Any Degrees of Freedom
Authors: Kuo Chin-Hsing , Dai Jian S.
Published: November 2020

This paper presents the structure synthesis of a special class of parallel manipulators with motion decoupleability. The manipulator is synthesized by grouping a motion constraint leg and a set of constraint-free legs. The desired motion, i.e., the output degrees of freedom (DOFs), of the end-effector is expressed by a projective angle representation. It was found that the fully decoupled design for parallel manipulators with any DOFs is achievable when the output motion is described by the projective angles. A synthesis procedure is proposed based on the reasoning of the screw systems and reciprocal screws of the decoupled motion. Several design examples of fully decoupled 2-, 3-, 4-, 5-, and 6-DOF parallel manipulators are provided.
The Influence of Gait Stance and Vehicle Type on Pedestrian Kinematics and Injury Risk
Authors: Pak Wansoo , Grindle Daniel , Untaroiu Costin
Published: November 2020

Pedestrians are one of the most vulnerable road users. In 2018 the USA reported the highest number of pedestrian fatalities number in nearly three decades. Government safety agencies and car manufacturers have started paying greater attention towards pedestrian protection. The pre-impact conditions of Car-to-Pedestrian Collisions (CPC) varies significantly in terms of the characteristics of vehicles (e.g. front-end geometry, stiffness, etc.) and pedestrians (e.g. anthropometry, posture, etc.). The influence of vehicle type and pedestrian gait has not been analyzed. The purpose of this study was to numerically investigate the changes in pedestrian kinematics and injuries across various gait postures and two different car types. Five finite element (FE) human body models, representing 50th percentile male in gait cycle, were developed and used to perform CPC simulations with two generic vehicle FE models representing a family car (FCR), and a sport utility vehicle (SUV). In the impacts with the high-profile vehicle (SUV), the pedestrian models usually slide above the bonnet leading edge and report shorter wrap around distances (WAD) than in low-profile vehicle (FCR) impacts. The pedestrian postures influenced the post-impact rotation of the pedestrian and consequently, the impacted head region. The pedestrian posture also influenced the risk of injuries in the lower extremities. Higher risk of bone fractures was observed in the stance phase posture compared to the swing phase. The findings of this study should be taken into consideration when examining pedestrian protection protocols. In addition, the results of this study can be used to improve the design of active safety systems used to protect pedestrians in collisions.
A Computational Framework for the Inverse Identification of Temperature-Dependent Dielectric Permittivity of Materials at Giga-Hertz Frequencies
Authors: Iliopoulos A. P. , Graber B. D. , Michopoulos J. G. , Steuben J. C. , Birnbaum A. J. , Gorzkowski E. P. , Patterson E. A. , Fischer R. P. , Johnson L. A. , Bernhardt P. A. , Coombs J. M.
Published: November 2020

The microwave sintering of ceramics and other materials has emerged as an attractive method of manufacturing solid objects though volumetric approaches. The accurate modeling of such processes requires the knowledge of the dielectric constant, and particularly the real and imaginary parts of the permittivity, of these materials as they vary with temperature. This particular measurement becomes very challenging as the temperature rises. In this work, an experimental apparatus and an inverse approach are proposed, based on the coupling of the thermo-mechano-electromagnetic physics that can be used to measure the real and imaginary parts of the dielectric constant at high temperatures.
Zero Moment Control for Lead-Through Teach Programming on a Collaborative Robot
Authors: Canfield Stephen L. , Owens Joseph S. , Zuccaro Stephen G.
Published: November 2020

Robots are commonly used for automated welding in many industries such as automotive manufacturing. The complexity and time of programming presents an obstacle in using robotic automation in welding or other tasks for small to medium enterprises that lack resources for training or expertise in traditional robot programming strategies. It also dictates a high level of repeated parts to offset the cost of weld programming. Collaborative Robots or Cobots are robots designed for more collaborative operations with humans. Cobots permit new methods of task instruction (programming) through direct interaction between the operator and robot. This paper presents a model and calibration strategy for a collaborative robot to aid intuitive teaching methods for tasks such as welding. The method makes use of a torque estimation model based on robot momentum to create an observer to evaluate external forces. The torque observer is first used to characterize the friction that exists within the robot joints. This data is used to define the parameters of a friction model that combines static, Coulomb and viscous friction properties with a sigmoid function to represent transition between motion states and a second level Fourier series to represent position dependency of the Coulomb friction terms. The friction model is then integrated into the robot control and used to provide a mode in which the robot can be easily dragged around the workspace to provide weld path training.
Enhanced Particle Swarm Optimization via Reinforcement Learning
Authors: Wu Di , Wang G. Gary
Published: November 2020

Particle swarm optimization (PSO) method is a well-known optimization algorithm, which shows good performance in solving different optimization problems. However, PSO usually suffers from slow convergence. In this paper, a reinforcement learning method is used to enhance PSO in convergence by replacing the uniformly distributed random number in the updating function by a random number generated from a well-selected normal distribution. The mean and variance of the normal distribution are estimated from the current state of each individual through a policy net. The historic behavior of the swarm group is learned to update the policy net and guide the selection of parameters of the normal distribution. The proposed algorithm is tested with numerical test functions and the results show that the convergence rate of PSO can be improved with the proposed Reinforcement Learning method (RL-PSO).
Defining Function: How Student Definitions Compare to Literature and Function Model Generation
Authors: Patel Apurva , Summers Joshua D. , Davenport Brian
Published: November 2020

The concept of “function” serves various purposes in engineering design, resulting in a variety of definitions for the same term. This paper presents an analysis of function definitions provided by mechanical engineering students as part of a larger protocol study on function modeling behaviors. This work investigates the relationships between student definitions of function and their corresponding completed function models. Student definitions are also compared to those found in literature using a topical analysis. Student definitions tend to skew towards one topic, whereas definitions in literature are found to be more likely to contain a combination of topics. Subsequently, student definitions are compared to the function models generated by students based on the size and completeness evaluation of models. Larger function models are found to be correlated to definitions that include terms such as “input/output” and “process”. Definitions that use terms such as “task” and “action” are found to have higher evaluation scores, but the differences are small in magnitude. In general, the activity of creating a function model was found to influence how students define function. Finally, limitations of the work are discussed along with future research directions.
Unification of Poincaré and Floquet Theory for Time Periodic Systems
Authors: Subramanian Susheelkumar C. , Redkar Sangram
Published: November 2020

As per Floquet theory, a transformation matrix (Lyapunov Floquet transformation matrix) converts a linear time periodic system to a linear time-invariant one. Though a closed form expression for such a matrix was missing in the literature, this method has been widely used for studying the dynamical stability of a time periodic system. In this paper, the authors have derived a closed form expression for the Lyapunov Floquet (L-F) transformation matrix analytically using intuitive state augmentation, Modal Transformation and Normal Forms techniques. The results are tested and validated with the numerical methods on a Mathieu equation with and without damping. This approach could be applied to any linear time periodic systems.
Nonlinear Dynamic Response of an Isolation System With Negative Stiffness and Shape Memory-Based Damping
Authors: Salvatore Andrea , Carboni Biagio , Lacarbonara Walter
Published: November 2020

The negative stiffness offered by bi-stable mechanisms can improve the dynamic performance of a structure. In this work the effects of adding negative stiffness and shape memory alloy (SMA) damping in base-isolated structures are explored through the study of the stationary response for different values of negative stiffness and SMA hysteretic damping ratio. The frequency response curves of the isolated structure, with and without the negative stiffness contribution, are numerically obtained for different levels of excitation amplitude in order to evaluate the acceleration and displacement transmissibility curves. The benefits of negative stiffness, damping amplification and reduced transmissibility of accelerations and displacements, as well as the existence of dynamic instabilities, are illustrated.
Mirroring Neurostimulation Outcomes Through Behavioral Interventions to Improve Creative Performance
Authors: Sahar A. , Farb N. A. S. , Shu L. H.
Published: November 2020

Creativity, a key component of engineering design, is not a static trait, but a skill that can be strategically enhanced. Neurostimulation methods, e.g., using electrical current to stimulate brain areas, have been reliably shown to improve creative performance. However, safety and ethical concerns present obstacles to the direct implementation of such methods in the engineering-design process. Thus, the current work explores whether creative performance can be enhanced using behavioral tasks that recruit the same brain regions targeted in neurostimulation studies.

Study participants were 30 undergraduate students enrolled in an introductory psychology course. Two intervention tasks, a Stroop task and a finger-tapping pattern-matching task, each with easy and hard versions, were used in a 2 (task type) x 3 (task difficulty) within-subjects design. Relative to the pretest period, difficulty was manipulated by using versions of tasks with 1) predictable responses (easy) and 2) unpredictable responses (hard). Creativity in each experimental condition was assessed via the well-validated Alternative Uses Test (AUT).

A multilevel analysis revealed a significant increase in fluency (number of alternative uses) as task difficulty increased regardless of task type. Flexibility (number of alternative-uses categories) also increased with task difficulty, but the effect was stronger for the Stroop task. These results suggest that high-difficulty versions of the selected tasks may be more effective in increasing AUT performance. Between the two tasks studied, the Stroop task has greater potential as a candidate to adapt as a behavioral intervention to improve creativity. Beyond the Stroop task, other behaviors, which activate brain regions that respond favorably to neurostimulation, may also be explored as the bases of interventions to improve creative performance in engineering design.
Experimental Study of Mullins Effect in Natural Rubber for Different Stretch Conditions
Authors: Gkouti Elli , Yenigun Burak , Jankowski Krystof , Czekanski Aleksander
Published: November 2020

We subjected rubber coupons to cyclical uniaxial tension to investigate the softening effect, where the primary loading at its initial position was followed by additional unloading and reloading. Less stress was required upon reloading than that required in the previous loading for the same degree of stretch, reached on the first loading. This stress softening is significant when reloading follows virgin loading. The magnitude of stress softening is related to the maximum stretch elastomers can achieve in each cycle. To investigate this phenomenon, rubber coupons were subjected to four cycles of simple tension until the desired stretch was reached. We expected that several tests under the same conditions would provide almost identical results. However, we observed different stress requirements for different degrees of stretch when multiple cycles of the same stretch were performed. For three different experimental tests of the same amount of stretch, we saw huge differences in each cycle of loading-relaxation-reloading, a phenomenon that was more obvious during stress relaxation.
Data Driven Model Identification for a Chaotic Pendulum With Variable Interaction Potential
Authors: Yesilli Melih C. , Khasawneh Firas A.
Published: November 2020

Data driven model identification methods have grown increasingly popular due to enhancements in measuring devices and data mining. They provide a useful approach for comparing the performance of a device to the simplified model that was used in the design phase. One of the modern, popular methods for model identification is Sparse Identification of Nonlinear Dynamics (SINDy). Although this approach has been widely investigated in the literature using mostly numerical models, its applicability and performance with physical systems is still a topic of current research. In this paper we extend SINDy to identify the mathematical model of a complicated physical experiment of a chaotic pendulum with a varying potential interaction. We also test the approach using a simulated model of a nonlinear, simple pendulum. The input to the approach is a time series, and estimates of its derivatives. While the standard approach in SINDy is to use the Total Variation Regularization (TVR) for derivative estimates, we show some caveats for using this route, and we benchmark the performance of TVR against other methods for derivative estimation. Our results show that the estimated model coefficients and their resulting fit are sensitive to the selection of the TVR parameters, and that most of the available derivative estimation methods are easier to tune than TVR. We also highlight other guidelines for utilizing SINDy to avoid overfitting, and we point out that the fitted model may not yield accurate results over long time scales. We test the performance of each method for noisy data sets and provide both experimental and simulation results. We also post the files needed to build and reproduce our experiment in a public repository.
Automated Layout Generation Methods for 2D Spatial Packing
Authors: Peddada Satya R. T. , Rodriguez Samanta B. , James Kai A. , Allison James T.
Published: November 2020

Development of a computationally-tractable design method for combined multi-physics optimization of packing and routing problems, at a relevant scale, within compact packaging volumes, will offer benefits across several engineering domains. But for performing multi-physics packing and routing optimization, the generation of spatially feasible initial layouts is essential. Three new and computationally efficient methods are demonstrated in this article to produce automatically interference-free 2D geometric layouts. First, a novel 2D force-directed layout method (FDLM) is proposed that implicitly ensures noninterference between components and/or the interconnect network by utilizing spring force theory without using explicit geometric constraints. Second, the A* algorithm, a well-established 2D shortest path algorithm (SPA), has been modified significantly to perform efficient routing of complex interconnect systems. Third, a new geometric topology (GT) enumeration algorithm is presented that produces all unique interconnect routing configurations for given multi-component system architecture. These layout generation methods are then compared with respect to average computational efficiencies and average success rates in attaining feasible layouts for a restricted class of topologies, including evaluation of how the methods scale to problems with an increased number of components. Limitations and future work items for each method are discussed. These methods are presented as an important step toward solution strategies that are compatible with the currently unmet challenges of real-world 2D and 3D combined packing and routing problems, including efficient navigation of the space of discrete options for interconnect geometric topology, as well as scaling to more complex problems.
A Narrow-Track Tilting Tricycle With Variable Stability That the Rider Can Control Manually
Authors: Pierson A. M. , Shortreed A. K. , Van Asten P. D. , Dressel A. E.
Published: November 2020

Many health, environmental, and quality-of-life benefits due to cycling have been identified, including exercise, zero-emissions, reduced pavement requirements compared to cars and busses, and nearly silent operation. A significant fraction of the population, however, is unable to join in this activity with traditional upright bicycles, including people with balance or joint limitations caused by injury, disease, or age.

One solution to these ergonomic difficulties is the recumbent bicycle, but many riders find them difficult to balance and steer because of several factors, including center of mass location and distribution. Another solution, the recumbent tricycle, must have a wide axle track and/or low center of mass for lateral stability when turning, which requires more pavement and creates more aerodynamic drag than the bicycle equivalent.

We present a solution that aims to combine the best attributes of these vehicles and eliminate the drawbacks: a tilting tricycle with variable stability that the rider can control manually. It balances and leans into corners like a bicycle when going fast, and it balances and stays upright like a tricycle when stopped or going slow to reduce the steering burden on the rider. Between these two extremes, the rider can finely adjust exactly how docile a bicycle it mimics.
Improving the Accuracy and Diversity of Feature Extraction From Online Reviews Using Keyword Embedding and Two Clustering Methods
Authors: Park Seyoung , Kim Harrison M.
Published: November 2020

In product design, it is essential to understand customers’ preferences for product features. Traditional methods including the survey and interview are time-consuming and costly. As an alternative, research on utilizing online data for user analysis has been actively conducted. Although various methods have been proposed in this domain, most of them focus on the main features or usages of the product. However, from the manufacturer’s perspective, sub-features are as crucial as main features or usages, because the preference for sub-features is necessary for component configuration in actual product development. As the first step to solve this problem, this paper proposes a methodology to extract and cluster sub-features by incorporating phrase embedding into the previous word embedding. Also, the presented methodology increases the accuracy and diversity of the clustering result by using X-means clustering as a noise filter and adopting spectral clustering.
Structural Design Synthesis Through a Sequential Decision Process
Authors: Ororbia Maximilian E. , Warn Gordon P.
Published: November 2020

This article illustrates that structural design synthesis can be achieved through a sequential decision process, whereby a sparsely connected seed configuration is sequentially altered through discrete actions to generate the best design solution, with respect to a specified objective and constraints. Specifically, the generative design synthesis is mathematically formulated as a finite Markov Decision Process. In this context, the states correspond to a specific structural configuration, the actions correspond to the available alterations that can be made to a given configuration, and the immediate rewards are constructed to be proportional to the improvement in the altered configuration’s performance. In the context of generative structural design synthesis, since the immediate rewards are not known at the onset of the process, reinforcement learning is employed to obtain an approximately optimal policy by which to alter the seed configuration to synthesize the best design solution. The approach is applied for the optimization of planar truss structures and its utility is investigated with three numerical examples, each with unique domains and constraints.