bluuebunny/crossref_metadata_2025 huggingface dataset:
Deriving Metamodels to Relate Machine Learning Quality to Design Repository Characteristics in the Context of Additive Manufacturing
Authors: Williams Glen , Meisel Nicholas A. , Simpson Timothy W. , McComb Christopher
Published: November 2020

The widespread growth of additive manufacturing, a field with a complex informatic “digital thread”, has helped fuel the creation of design repositories, where multiple users can upload distribute, and download a variety of candidate designs for a variety of situations. Additionally, advancements in additive manufacturing process development, design frameworks, and simulation are increasing what is possible to fabricate with AM, further growing the richness of such repositories. Machine learning offers new opportunities to combine these design repository components’ rich geometric data with their associated process and performance data to train predictive models capable of automatically assessing build metrics related to AM part manufacturability. Although design repositories that can be used to train these machine learning constructs are expanding, our understanding of what makes a particular design repository useful as a machine learning training dataset is minimal. In this study we use a metamodel to predict the extent to which individual design repositories can train accurate convolutional neural networks. To facilitate the creation and refinement of this metamodel, we constructed a large artificial design repository, and subsequently split it into sub-repositories. We then analyzed metadata regarding the size, complexity, and diversity of the sub-repositories for use as independent variables predicting accuracy and the required training computational effort for training convolutional neural networks. The networks each predict one of three additive manufacturing build metrics: (1) part mass, (2) support material mass, and (3) build time. Our results suggest that metamodels predicting the convolutional neural network coefficient of determination, as opposed to computational effort, were most accurate. Moreover, the size of a design repository, the average complexity of its constituent designs, and the average and spread of design spatial diversity were the best predictors of convolutional neural network accuracy.
Numerical Investigation of Multi-Mode Guided Wave Focusing in Pipe–Like Structures Using Gradient Index Metamaterial Lens Design
Authors: Danawe Hrishikesh G. , Ozevin Didem , Tol Serife
Published: November 2020

This paper presents a numerical study on multi-mode focusing of guided elastic waves in pipe-like structures over a range of frequencies using a single metamaterial lens design. We explore focusing of the first two longitudinal (L(0,1) and L(0,2)) and the first torsional (T(0,1)) wave modes in steel pipe integrated with a metamaterial lens made of cylindrical steel stubs of varying heights attached to outer surface of the pipe. Proposed metamaterial lens design is based on gradient index (GRIN) theory with hyperbolic secant distribution of refractive index in circumferential direction. Amplification of multi-mode guided wave signals are achieved at focal points of the lens which is verified through numerical simulations. The focusing performance of proposed lens is studied at multiple frequencies for all the three modes and first two focal positions are verified with theoretical predictions of GRIN theory.
Towards Prospective Sustainability Life Cycle Assessment
Authors: Clarke-Sather Abigail R. , Mamun Saleh , Nolan Daniel , Schoff Patrick , Aro Matthew , Ulrich Bridget
Published: November 2020

Life cycle assessment (LCA) is a well-established tool for measuring environmental effects of existing technology. While the most recent LCA research has focused on environmental impacts, in particular on the effects of climate change, there is growing interest in how LCA can be used prospectively. A 2019 workshop in Duluth, Minnesota sought to define the needs and priorities of prospective life cycle assessment from a perspective that considers diverse viewpoints. In that workshop, participants outlined frameworks for how sustainability impacts might figure into a prospective LCA tool focused on assessing technologies currently under development. Those frameworks included social and economic impacts, which were characterized alongside environmental impacts, with the goal of predicting potential impacts and developing recommendations for improving technologies. Cultural perspective, in particular the roots of the German circular economy, was explored and held up as a reminder that different communities are influenced by different sustainability concerns, leading to diverse policy and cultural prerogatives. The purpose of this paper is to catalyze conversation about how to frame methodologies of existing LCA tools that could be used in a prospective sustainability context.
Statistical Analysis of Tensile Tests Performed on 316L Specimens Manufactured by Directed Energy Deposition
Authors: Iliopoulos A. P. , Thomas J. P. , Steuben J. C. , Saunders R. , Michopoulos J. G. , Bagchi A. , Birnbaum A. J.
Published: November 2020

The present work reports on the results of tension tests conducted on 316L stainless steel specimens extracted out of thin-walled boxes produced by powder jet additive manufacturing. The specimens were minimally processed to study the potential effects of the manufacturing process on the apparent mechanical properties rather than identifying the properties of the resulting bulk material. Statistical analysis is performed and presented in an attempt to identify correlations between the manufacturing parameters and the apparent mechanical properties. The mechanical properties of interest are Young’s modulus, the yield stress (measured at the 0.2% level), the ultimate stress, and the failure strain.
A Blockchain-Based Traceability System for Waste Management in Smart Cities
Authors: Gopalakrishnan Praveen Kumare , Hall John , Behdad Sara
Published: November 2020

Waste tracking is becoming an important concern for developed countries as well as developing regions, where municipalities aim to assure proper waste management considering environmental and economic objectives. Waste tracking is important not only for a transparent reporting system compatible with environmental regulations but also for economically viable waste collection and recovery solutions. In this paper, a waste tracking system based on the blockchain technology is introduced where different entities involved in the system will be able to retrieve required data from the platform and decide on their level of contributions. The conventional technologies do not provide a sufficient level of transparency and coordination among different entities. With the introduction of blockchain as a tamper-proof technology, municipalities can enhance the efficiency of their waste management efforts. The proposed blockchain technology can connect proper stakeholders towards collaboration and sharing information. The concept of a smart contract for waste management is discussed and further, a decision-making framework is developed to guide users of the system select proper services available to them, depending on the level of data sharing, cost, reliability, and the security level that they expect from the system.
Analyzing the Characteristics of Cognitive-Assistant-Facilitated Ideation Groups
Authors: Maier Torsten , Soria Zurita Nicolas F. , Starkey Elizabeth , Spillane Daniel , Menold Jessica , McComb Christopher
Published: November 2020

The rapid digitalization of the world has affected engineering and design in a variety of ways, including the introduction of new computer-aided ideation tools. Cognitive assistants (CA), an increasingly common digital technology, use natural-language processing and artificial intelligence to provide computational support. Because cognitive assistants are capable of emulating humans in some tasks, they may be suited to support brainstorming activities when trained coaches or facilitators are not available. This study compared co-located brainstorming groups facilitated by human facilitators and a CA facilitator. Interaction Dynamics Notation was used to code the sessions, and Hidden Markov Models were used to define the group’s states. We found that human facilitation was associated with blocks/interruptions and responding to those while cognitive assistant facilitation was associated with deviations and silence. Human facilitation was also found to produce a more equal distribution of speaking time.
Free Vibration of Bistable Clamped-Clamped Beams: A Preliminary Study
Authors: Song Xiaolei , Liu Haijun
Published: November 2020

We present a preliminary study on bistable clamped-clamped beams both analytically and experimentally relating the linear post-buckling vibrations to the generated sound. In the analytical study, closed-form natural frequencies and mode shapes around the first buckled configuration are derived from an eigenvalue problem. It is found that as the static deflection of the buckled beam increases, the natural frequencies of the anti-symmetric vibrational modes stay constant, while those of the symmetric vibrational modes increase asymptotically. In the experimental study, a bistable clamped-clamped buckled beam made of steel is switched quasi-statically by hand between the two stable configurations. The generated sound is measured by a microphone and analyzed in both temporal and frequency domains, which agrees well with the analytical results. This work lays the foundation for using bistable beams in a variety of applications such as actuators, resonators, energy harvesters, and vibration reduction.
A Simple and Effective Methodology to Perform Multi-Objective Bayesian Optimization: An Application in the Design of Sandwich Composite Armors for Blast Mitigation
Authors: Valladares Homero , Tovar Andres
Published: November 2020

Bayesian optimization is a versatile numerical method to solve global optimization problems of high complexity at a reduced computational cost. The efficiency of Bayesian optimization relies on two key elements: a surrogate model and an acquisition function. The surrogate model is generated on a Gaussian process statistical framework and provides probabilistic information of the prediction. The acquisition function, which guides the optimization, uses the surrogate probabilistic information to balance the exploration and the exploitation of the design space. In the case of multi-objective problems, current implementations use acquisition functions such as the multi-objective expected improvement (MEI). The evaluation of MEI requires a surrogate model for each objective function. In order to expand the Pareto front, such implementations perform a multi-variate integral over an intricate hypervolume, which require high computational cost. The objective of this work is to introduce an efficient multi-objective Bayesian optimization method that avoids the need for multi-variate integration. The proposed approach employs the working principle of multi-objective traditional methods, e.g., weighted sum and min-max methods, which transform the multi-objective problem into a single-objective problem through a functional mapping of the objective functions. Since only one surrogate is trained, this approach has a low computational cost. The effectiveness of the proposed approach is demonstrated with the solution of four problems: (1) an unconstrained version of the Binh and Korn test problem (convex Pareto front), (2) the Fonseca and Fleming test problem (non-convex Pareto front), (3) a three-objective test problem and (4) the design optimization of a sandwich composite armor for blast mitigation. The optimization algorithm is implemented in MATLAB and the finite element simulations are performed in the explicit, nonlinear finite element analysis code LS-DYNA. The results are comparable (or superior) to the results of the MEI acquisition function.
Agent Based Resilient Transportation Infrastructure With Surrogate Adaptive Networks
Authors: Apostol Andre A. , Turner Cameron J.
Published: November 2020

Connected autonomous intelligent agents (AIA) can improve intersection performance and resilience for the transportation infrastructure. An agent is an autonomous decision maker whose decision making is determined internally but may be altered by interactions with the environment or with other agents. Implementing agent-based modeling techniques to advance communication for more appropriate decision making can benefit autonomous vehicle technology.

This research examines vehicle to vehicle (V2V), vehicle to infrastructure (V2I), and infrastructure to infrastructure (I2I) communication strategies that use gathered data to ensure these agents make appropriate decisions under operational circumstances. These vehicles and signals are modeled to adapt to the common traffic flow of the intersection to ultimately find an traffic flow that will minimizes average vehicle transit time to improve intersection efficiency. By considering each light and vehicle as an agent and providing for communication between agents, additional decision-making data can be transmitted. Improving agent based I2I communication and decision making will provide performance benefits to traffic flow capacities.
Design of an Ankle Rehab Robot With a Compliant Parallel Kinematic Mechanism
Authors: Jalgaonkar Nishant , Kim Adam , Awtar Shorya
Published: November 2020

In this paper, we present the design of a novel ankle rehabilitation robot (ARR), called the Flex-ARR, that employs a compliant parallel kinematic mechanism (PKM) with decoupled degrees of freedom. The Flex-ARR is designed to collocate the biological center of rotation of the ankle with that of the robot’s center of rotation to allow natural ankle motion. While multiple ARR designs have been developed in research labs and some are commercially available, their clinical adoption has been limited because they do not emulate the natural motion of the ankle. The Flex-ARR leverages a unique PKM design that uses compliance to absorb minor misalignments between the center of rotation of the ankle and the robot, thereby allowing natural ankle motion. Also, because of its unique design, the PKM inherently accommodates variations in user foot sizes with minimal adjustments. The Flex-ARR is designed to provide multiple training modes that allow for both rehabilitation and assessment modalities. This paper provides a review of the literature to identify the key factors that have limited the clinical adoption of existing ARRs. Based on this, functional requirements and design specifications for an optimal ARR are defined. This is then used to develop a design strategy, followed by conceptual and detailed design.
Structure, Process, and Material Influences for 3D Printed Lattices Designed With Mixed Unit Cells
Authors: Briguiet Gabriel , Egan Paul F.
Published: November 2020

Emerging 3D printing technologies are enabling the design and fabrication of novel architected structures with advantageous mechanical responses. Designing complex structures, such as lattices, with a targeted response is challenging because build materials, fabrication process, and topological design have unique influences on the structure’s mechanical response. Changing any factor may have unanticipated consequences, even for simpler lattice structures. Here, we conduct mechanical compression experiments to investigate varied lattice design, fabrication, and material combinations using stereolithography printing with a biocompatible polymer. Mechanical testing demonstrates that a higher ultraviolet curing time increases elastic modulus. Material testing demonstrated that anisotropy does not strongly influence lattice mechanics. Designs were altered by comparing homogenous lattices of single unit cell types and heterogeneous lattices that combine two types of unit cells. Unit cells for heterogeneous structures include a Cube design for a high elastic modulus and Cross design for improved shear response. Mechanical testing of three heterogeneous layouts demonstrated how unit cell organization influences mechanical outcomes, therefore enabling the tuning of an elastic modulus that surpasses the law of averages designed for application-dependent mechanical needs. These findings provide a foundation for linking design, process, and material for engineering 3D printed structures with preferred properties, while also facilitating new directions in design automation and optimization.
Is Verifying Frequently an Optimal Strategy? A Belief-Based Model of Verification
Authors: Kulkarni Aditya U. , Salado Alejandro , Wernz Christian , Xu Peng
Published: November 2020

Verification activities increase an engineering team’s confidence in its system design meeting system requirements, which in turn are derived from stakeholder needs. Conventional wisdom suggests that the system design should be verified frequently to minimize the cost of rework as the system design matures. However, this strategy is based more on experience of engineers than on a theoretical foundation. In this paper, we develop a belief-based model of verification of system design, using a single system requirement as an abstraction, to determine the conditions under which it is cost effective for an organization to verify frequently. We study the model for a broad set of growth rates in verification setup and rework costs. Our results show that verifying a system design frequently is not always an optimal verification strategy. Instead, it is only an optimal strategy when the costs of reworking a faulty design increase at a certain rate as the design matures.
How Engineering Design Students’ Psychological Safety Impacts Team Concept Generation and Screening Practices
Authors: Cole Courtney , Marhefka Jacqueline , Jablokow Kathryn , Mohammed Susan , Ritter Sarah , Miller Scarlett
Published: November 2020

Psychological safety has been shown to be a consistent, generalizable, and multilevel predictor of outcomes in performance and learning across fields. While work in this field has suggested that psychological safety can impact the creative process, particularly in the generation of ideas and in the discussions surrounding idea development, there has been limited investigations of psychological safety in the engineering domain. Without this knowledge we do not know when fostering psychological safety in a team environment is most important. This study provides the first attempt at answering this question through an empirical study with 53 engineering design student teams over the course of a 4- and 8-week design project. Specifically, we sought to identify the role of psychological safety on the number and quality (judged by goodness) of ideas generated. In addition, we explored the role of psychological safety on ownership bias and goodness in the concept screening process. The results of the study identified that while psychological safety was not related to the number of ideas a team developed, it was positively related to the quality (goodness) of the ideas developed. In addition, while no relationship was found between psychological safety and ownership bias during concept screening, the results showed that teams with high psychological safety selected a higher percentage of their team members ideas.
Kinematic Analysis of a 5-DOF Positioner for Precision Additive Manufacturing
Authors: Saadatzi Mohammad Hossein , Popa Dan O.
Published: November 2020

Additive manufacturing, as a viable industrial-production technology, requires multi-DOF positioning with high precision and repeatability for either the printer head, or the part being printed. In this paper we present a novel methodology to analyze the error propagation informing the design of a high-precision robotic 5-DOF positioner for applications in additive manufacturing. We designed our positioner through serial attachment of linear and rotational stages by comparing the precision of three different kinematic arrangements of stages. Within order to minimize positioning errors in Cartesian space, the kinematic sensitivity of the mechanisms end-effector relative to the maximum expected error of each joint was computed, and the kinematic configuration with smallest 6D positioning error at the end-effector was selected. The methodology employed in this paper for the error propagation analysis of serial kinematic chains has a great level of generality and can facilitate the design and optimization of a wide-class of multi-DOF positioners.
“You Cannot Test It Before It Is Verified. When It Is Verified You Cannot Change It”: Prototyping Challenges in Industry
Authors: Arndt Hansen Camilla , Özkil Ali Gürcan
Published: November 2020

In a new product development process, multiple decisions must be made regarding the selection of concepts to pursue and how a product should be constructed. In many companies, these decisions are informed by the results from prototype tests.

In this research, we investigate which challenges practitioners experience when they prototype, the opportunities they see for overcoming such challenges, and the current trends and developments that affect prototyping in industry.

Data were collected from eight practitioners from the Danish industry through a mixed methods research approach consisting of a small survey and focus group discussions. A qualitative content analysis resulted in the identification of 23 prototyping challenges, 15 opportunities for future improvement, and 5 prototyping trends.

Practitioners feel challenged when they have to make decisions from a few prototypes with limited properties and they seek guidance on the proper use of prototyping strategies during the development process. Additionally, challenges arise due to gaps between virtual and physical prototyping, regulations in the medical industry, and unexpected misinterpretations of prototypes.

These results contribute to our understanding of prototyping in industry and helps us identify areas where the research community can focus their future efforts for the benefit of practitioners.
Analysis of the Rigid Motion of a Developable Conical Mechanism
Authors: Woodland McKell , Hsiung Michelle , Matheson Erin L. , Safsten C. Alex , Greenwood Jacob , Halverson Denise M. , Howell Larry L.
Published: November 2020

We demonstrate analytically that it is possible to construct a developable mechanism on a cone that has rigid motion. We solve for the paths of rigid motion and analyze the properties of this motion. In particular, we provide an analytical method for predicting the behavior of the mechanism with respect to the conical surface. Moreover, we observe that the conical developable mechanisms specified in this paper have motion paths that necessarily contain bifurcation points which lead to an unbounded array of motion paths in the parameterization plane.
Bayesian Optimization for Simulation-Based Design of Multi-Model Systems
Authors: Tao Siyu , van Beek Anton , Apley Daniel W. , Chen Wei
Published: November 2020

We address the problem of simulation-based design using multiple interconnected expensive simulation models, each modeling a different subsystem. Our goal is to find the globally optimal design with minimal model evaluation costs. To our knowledge, the best existing approach is to treat the whole system as a single expensive model and apply an existing Bayesian optimization (BO) algorithm. This approach is likely inefficient due to the need to evaluate all the component models in each iteration. We propose a multi-model BO approach that dynamically and selectively evaluates one component model per iteration based on linked emulators for uncertainty quantification and the system knowledge gradient (KG) as acquisition function. Building on this, we resolve problems with constraints and feedback couplings that often occur in real complex engineering design by penalizing the objective emulator and reformulating the original problem into a decoupled one. The superior efficiency of our approach is demonstrated through solving an analytical problem and a multidisciplinary design problem of electronic packaging optimization.
METASET: An Automated Data Selection Method for Scalable Data-Driven Design of Metamaterials
Authors: Chan Yu-Chin , Ahmed Faez , Wang Liwei , Chen Wei
Published: November 2020

Data-driven design of mechanical metamaterials is an increasingly popular method to combat costly physical simulations and immense, often intractable, geometrical design spaces. Using a precomputed dataset of unit cells, a multiscale structure can be quickly filled via combinatorial search algorithms, and machine learning models can be trained to accelerate the process. However, the dependence on data induces a unique challenge: An imbalanced dataset containing more of certain shapes or physical properties than others can be detrimental to the efficacy of the approaches and any models built on those sets. In answer, we posit that a smaller yet diverse set of unit cells leads to scalable search and unbiased learning. To select such subsets, we propose METASET, a methodology that 1) uses similarity metrics and positive semi-definite kernels to jointly measure the closeness of unit cells in both shape and property space, and 2) incorporates Determinantal Point Processes for efficient subset selection. Moreover, METASET allows the trade-off between shape and property diversity so that subsets can be tuned for various applications. Through the design of 2D metamaterials with target displacement profiles, we demonstrate that smaller, diverse subsets can indeed improve the search process as well as structural performance. We also apply METASET to eliminate inherent overlaps in a dataset of 3D unit cells created with symmetry rules, distilling it down to the most unique families. Our diverse subsets are provided publicly for use by any designer.
Advisory and Adaptive Communication Improves Trust in Autonomous Vehicle and Pedestrian Interaction
Authors: She Jinjuan
Published: November 2020

Autonomous vehicle (AV) is considered to be a significant part of the future of the automotive industry, with advantages such as higher transportation safety, less greenhouse gas emission, and wider transportation accessibility. However, the fruit of this technology cannot meet with much success in the market without an appropriate level of human trust, which might lead to refusing to adopt it, or using it in a wrong way. Therefore, except for improving safety of the technology itself, interactions between AV and human around it, such as pedestrians, are also paramount, especially effective communication. It is expected that certain communication could improve trust, and enable people to respond and act towards it accurately. This paper conducted a preliminary online study for a proof of concept that communication style (informative, advisory, and commanding) and communication strategy (single communication, adaptive communication) could affect pedestrian crossing decision process. The results demonstrate that advisory style improves trust in AVs when a Cross decision is expected by AVs, while both commanding and advisory styles improve trust in AVs when a Not Cross decision is expected by AVs. In addition, adaptive communication strategy improves trust significantly when AVs expect pedestrians to cross. This study helps understanding the communication between AV and pedestrians and is instrumental in developing more advanced AV communication mechanisms.
Memory and Idea Generation Applied to Product Repurposing
Authors: Arabian K. , Addis D. R. , Shu L. H.
Published: November 2020

Many engineering problems still require novel solutions, e.g., the repurposing of retired wind-turbine blades. Increasing evidence suggests that the recall of episodic memories enhances idea generation, but its application to engineering problems has been limited. The current work investigates the effectiveness of a memory induction on generating ideas. Engineering undergraduate students in a fourth-year design course (N = 38) completed a study under both of two conditions, a memory induction and a control (non-episodic-memory) induction. Participants underwent the induction before generating ideas on the Alternate Uses Task (AUT), a standard test of divergent thinking, and a wind-turbine-blade repurposing task (WRT).

AUT responses following the memory induction were deemed significantly more flexible (p = .045) and elaborate (p = .041) than responses following the control induction. No difference in response fluency (p = 0.205) followed the two inductions, possibly due to limited time allotted for the AUT. In line with this explanation, fluency was inversely related to elaboration. In the WRT, more appropriate (p = 0.009) and more feasible (p = 0.015) ideas for repurposing wind-turbine blades were generated following the memory than the control induction.

These results suggest that strategies increasing access to episodic memory may improve generation of alternative-use ideas for both common objects and wind-turbine blades.
Period-1 to Period-2 Motions in a Discontinuous Oscillator
Authors: Guo Siyu , Luo Albert C. J.
Published: November 2020

In this paper, grazing bifurcations on bifurcation trees in a discontinuous dynamical oscillator are discussed. Once the grazing bifurcation occurs, periodic motions switches from the old motion to a new one. Thus, grazing bifurcations on a bifurcation tree of period-1 to period-2 motions varying spring stiffness are presented in a discontinuous oscillator with three domains divided by circular boundaries. The stability and bifurcations of period-1 and period-2 motions are discussed. From analytical predictions, periodic motions are simulated numerically. Stiffness effects on the periodic motions are discussed. Such studies will help one understand parameter effects in discontinuous dynamical systems, which can be applied for system design and control.
Unified Motion Synthesis of Spatial Seven-Bar Platform Mechanisms and Planar-Four Bar Mechanisms
Authors: Sharma Shashank , Purwar Anurag
Published: November 2020

A unified motion generation algorithm that combines Spatial and Planar mechanism synthesis has been a hard problem in kinematics. In this paper, we present a new method to generate planar RRRR mechanisms and spatial 5-SS mechanisms using a unified algorithm. For a generalized spatial pose problem where all the poses fall on a plane, we show that there exist 1-∞ plane constraint solutions and 3-∞ planar-spherical solution dyads. We also show that for a spatial five pose problem where all poses lie on a plane, there exists a 2-∞ solution space of spherical and planar constraints. This multiplicity of solutions are intelligently constrained to find up to four circle constraints representing planar four-bar mechanism. Finally, examples are presented testing the proposed algorithm and verified using results from past publications.
Propulsion Dynamic Requirements Analysis for Multi-Axle Skid-Steer Wheeled Vehicles
Authors: Yacoub Mostafa , Ali Ahmed
Published: November 2020

Multi-axle skid-steer wheeled vehicles have the advantages of simplicity and enhanced traction. That’s why they are used in off-road environments and also in mobile robots. In the present work, a dynamic analysis of the propulsion system requirements for multi-axle wheeled vehicles is investigated. As the multi-axle wheeled vehicle differentially steers at a smaller turning radius, the driving torque requirements approach their peak. The adhesion at each tire of the multi-axle vehicle and its relation to the contact patches are analyzed. The analysis presented starts with four wheel drive, six wheel drive and eight wheel drive vehicles, then it is widened to n-wheel drive vehicles. A generic formula for obtaining the propulsion torque requirements for multi-axle skid-steer wheeled vehicles is presented. The analysis is extended to include experimental validation of the obtained analytical results. The experimental work includes three small electrically driven skid-steer vehicles; four wheel drive vehicle, six wheel drive vehicle and eight wheel drive vehicle. The selection of the drive motors for each of those vehicles was based on the proposed formula. Each of the three vehicles was tested in the worst case adhesion torque requirement. The experimental results showed that the proposed formula is capable, to a great extent, to predict the torque requirements for the multi-axle skid-steer wheeled vehicles in the design phase.
Path Synthesis of Defect-Free Spatial 5-SS Mechanisms Using Machine Learning
Authors: Sharma Shashank , Purwar Anurag
Published: November 2020

The synthesis of spatial mechanisms for defect-free path generation has not received a lot of attention. In this paper, we focus on the synthesis of 5-SS mechanisms and use a machine learning based approach. First, we create a coupler path database using a solver based on the iterative Newton-Raphson optimization algorithm. Subsequently, a data cleanup, normalization, balancing, and augmentation pipeline is established based on intrinsic properties of space curves namely curvature and torsion. Finally, we use an unsupervised learning algorithm based on Variational Autoencoder combined with K-means clustering to find a multiplicity of defect-free 5-SS mechanisms and examples are presented.
Analysis of Virtual Communication Within Engineering Design Teams and its Impact on Team Effectiveness
Authors: Adolphe Lauren , Van de Zande Georgia D. , Wallace David , Olechowski Alison
Published: November 2020

Online communication and collaboration tools are changing the way teams design products. The tools also generate a rich data source from which to study trends in communication. This paper focuses on how engineering teams utilize Slack, a popular team messaging software platform. We aim to better understand communication and coordination in product design teams via analysis of team social network dynamics, unique patterns of chat-like messaging (emoji usage), and the evolution of communication topics over time.

Our study analyzes the online interactions of 32 teams, sent during a 3-month senior undergraduate product design course. These 400,000+ messages represent the team communications from 4 years of teams, with 17–20 students per team.

We find that 1) Slack communications resulted in high density network maps, 2) network analysis of teams reveals that leaders have more central positions in the network, 3) strong teams have lower average centrality among members, equivalent to less public channel membership per person, 4) stronger teams use emojis at a higher rate, and 5) emojis are used most by leaders and highly connected members.

These findings represent preliminary foundations for best practices in online messaging, which may lead to more effective collaboration in product design.
Design of a Large Workspace Passive Spherical Joint via Contact Edge Design
Authors: Bajaj Neil M. , Dollar Aaron M.
Published: November 2020

This paper presents the design of a compact ball and socket type spherical joint that makes use of passive elements to increase the range of motion to greater than a hemisphere with infinite roll capacity. We discuss the limitations of typical spherical joints due to simple geometric considerations, and how the addition of redundancy, passive elements, and multiple contacting surfaces of differing geometry can increase the workspace of these joints. We discuss the relationship between kinematics, mechanical conditions (e.g. friction and contact forces) under quasistatic motion, and geometry required to achieve the increased range of motion. Furthermore, we provide a metric for assessing the viability or benefit of a potential design. Finally, we validate one of our designs with a physical prototype and demonstrate its achievable range of motion.
On the response of gamma irradiation on atomic layer deposition-grown β-Ga2O3 films and Au-β-Ga2O3-Au deep ultraviolet solar-blind photodetectors
Authors: Huang Chun-Ying , Lin Guan-Yu , Liu Yen-Yang , Chang Fu-Yuan , Lin Pei-Te , Hsu Feng-Hsuan , Peng Yu-Hsiang , Huang Zi-Ling , Lin Tai-Yuan , Gong Jyh-Rong
Published: November 2020

β-Ga2O3 films are deposited on (0001) sapphire substrates using triethylgallium (TEGa) and nitrous oxide (N2O) under high N2O/TEGa ratios by atomic layer deposition (ALD). Au-β-Ga2O3-Au metal/semiconductor/metal (MSM) solar-blind deep ultraviolet (DUV) photodetectors (PDs) are prepared using Au interdigitated electrodes deposited by thermal evaporation. The ALD-grown β-Ga2O3 films and Au-β-Ga2O3-Au DUV MSM PDs are irradiated with gamma ray to explore the response of gamma irradiation on the β-Ga2O3 films and β-Ga2O3 DUV MSM PDs. It is found that gamma irradiation tends to deteriorate the structural properties of the β-Ga2O3 films and dark current of the β-Ga2O3 DUV MSM PDs. Nevertheless, it also results in an increase in the 254 nm illuminated photocurrent of the Au-β-Ga2O3-Au DUV MSM PD. Energy band diagram schematics of the biased Au-β-Ga2O3-Au DUV MSM PDs are presented to interpret the influence of gamma irradiation-induced defects on the performances of the Au-β-Ga2O3-Au DUV MSM PDs.
Mammalian lipid droplets are innate immune hubs integrating cell metabolism and host defense
Authors: Bosch Marta , Sánchez-Álvarez Miguel , Fajardo Alba , Kapetanovic Ronan , Steiner Bernhard , Dutra Filipe , Moreira Luciana , López Juan Antonio , Campo Rocío , Marí Montserrat , Morales-Paytuví Frederic , Tort Olivia , Gubern Albert , Templin Rachel M. , Curson James E. B. , Martel Nick , Català Cristina , Lozano Francisco , Tebar Francesc , Enrich Carlos , Vázquez Jesús , Del Pozo Miguel A. , Sweet Matthew J. , Bozza Patricia T. , Gross Steven P. , Parton Robert G. , Pol Albert
Published: November 2020

Cells drop a bomb on pathogens

Lipid droplets (LDs) accumulate in cells to serve as lipid storage organelles. They are also an attractive source of nutrients for many pathogens. Bosch
et al.
show that various proteins involved in innate immunity form complexes on LDs in response to bacterial lipopolysaccharide (see the Perspective by Green). Upon activation, LDs became physically uncoupled from mitochondria, driving a shift in cells from oxidative phosphorylation to aerobic glycolysis. This work highlights the ability of LDs both to kill pathogens directly and to establish a metabolic environment conducive to host defense. This may inform future antimicrobial strategies in the age of antibiotic resistance.

Science
, this issue p.
eaay8085
; see also p.
294
Cartilage-inspired, lipid-based boundary-lubricated hydrogels
Authors: Lin Weifeng , Kluzek Monika , Iuster Noa , Shimoni Eyal , Kampf Nir , Goldberg Ronit , Klein Jacob
Published: November 2020

Slippery surfaces using lipids

In engineered systems, a reduction in friction can come from the use of lubricants or through surface coatings that are inherently slippery. For most hydrogels, which are cross-linked polymers heavily swelled with water, surface lubrication typically comes from trapped liquids that help to form a slippery surface. Drawing inspiration from articular cartilage that in part uses a lipid boundary layer, Lin
et al.
designed hydrogels with small concentrations of lipids that are continuously exuded toward the surface to make a slippery layer (see the Perspective by Schmidt). Friction and wear of the hydrogels was reduced by up to a factor of 100, and the effect was observed even after the hydrogels were dried and rehydrated.

Science
, this issue p.
335
; see also p.
288
Advancing limb neural prostheses
Authors: Raspopovic Stanisa
Published: November 2020

Neurotechnology can overcome communication difficulties between prostheses and amputees
Zeptosecond birth time delay in molecular photoionization
Authors: Grundmann Sven , Trabert Daniel , Fehre Kilian , Strenger Nico , Pier Andreas , Kaiser Leon , Kircher Max , Weller Miriam , Eckart Sebastian , Schmidt Lothar Ph. H. , Trinter Florian , Jahnke Till , Schöffler Markus S. , Dörner Reinhard
Published: November 2020

The travel time of light in a molecule

There is currently considerable interest in experimental studies of various ultrafast processes. Of particular interest are the real-time dynamics of photoionization, one of the most fundamental processes caused by the light-matter interaction, in which the absorption of a photon leads to the ejection of an electron and the formation of anion. Using an electron interferometric technique, Grundmann
et al.
report a birth time delay on the order of a few hundred zeptoseconds between two electron emissions from the two sides of molecular hydrogen, which is interpreted as the travel time of the photon across the molecule. The proposed technique is generally applicable to more complex systems, and further studies are necessary to support this interpretation.

Science
, this issue p.
339
Structural and spectroscopic characterization of an Fe(VI) bis(imido) complex
Authors: Martinez Jorge L. , Lutz Sean A. , Yang Hao , Xie Jiaze , Telser Joshua , Hoffman Brian M. , Carta Veronica , Pink Maren , Losovyj Yaroslav , Smith Jeremy M.
Published: November 2020

Nitrogen lifts iron to hexavalence

The myriad ways that iron can interact with oxygen have been amply studied in biochemical and geochemical contexts. More recently, chemists have explored the extent to which nitrogen can likewise stabilize iron in high oxidation states. Martinez
et al.
now report that an iron center coordinated by carbene ligands can react with an organic azide to form a pentavalent bis(imido) complex with two Fe=N bonds. One-electron oxidation then accessed the Fe(VI) oxidation state. Both compounds were sufficiently stable for crystallographic characterization.

Science
, this issue p.
356
A cellular sense of space and pressure
Authors: Shen Zhouyang , Niethammer Philipp
Published: November 2020

The nucleus measures cell confinement with a mechanosensitive phospholipase
Immiscible immunity
Authors: Green Douglas R.
Published: November 2020

Mammalian metabolism meets immunity at mitochondria-adjacent lipid droplets
Structural and Cellular Insights into the
l
,
d
-Transpeptidase YcbB as a Therapeutic Target in Citrobacter rodentium,
Salmonella
Typhimurium, and
Salmonella
Typhi Infections
Authors: Caveney N. A. , Serapio-Palacios A. , Woodward S. E. , Bozorgmehr T. , Caballero G. , Vuckovic M. , Deng W. , Finlay B. B. , Strynadka N. C. J.
Published: November 2020

The bacterial cell wall plays a key role in viability and is an important drug target. The cell wall is made of elongated polymers that are cross-linked to one another to form a load-bearing mesh. An alternative cell wall cross-linking mechanism used by the
l
,
d
-transpeptidase YcbB has been implicated in the stress-regulated roles of β-lactam resistance, outer membrane defect rescue, and typhoid toxin release. The role for this stress-linked cross-linking in the context of a host infection was unclear.
Approach to Assessment of New Swabs and Viral Transport Media for SARS-CoV-2 Testing
Authors: Locher Kerstin , Velapatino Billie , Caza Mélissa , Li Lisa , Porter Charlene , Charles Marthe
Published: November 2020

In light of the present pandemic of novel coronavirus disease 2019 (COVID-19) and the unprecedented high demand for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) testing worldwide, there are shortages of established specimen collection devices for respiratory viral testing for diagnostic microbiology laboratories. This creates the need to validate unverified collection devices from manufacturers that may not be a registered supplier for medical devices.
A Multiplex Microsphere IgG Assay for SARS-CoV-2 Using ACE2-Mediated Inhibition as a Surrogate for Neutralization
Authors: Cameron Andrew , Porterfield Claire A. , Byron Larry D. , Wang Jiong , Pearson Zachary , Bohrhunter Jessica L. , Cardillo Anthony B. , Ryan-Muntz Lindsay , Sorensen Ryan A. , Caserta Mary T. , Angeloni Stephen , Hardy Dwight J. , Zand Martin S. , Pecora Nicole D.
Published: November 2020

The coronavirus disease 2019 (COVID-19) pandemic has highlighted the challenges inherent to the serological detection of a novel pathogen such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Serological tests can be used diagnostically and for surveillance, but their usefulness depends on their throughput, sensitivity, and specificity. Here, we describe a multiplex fluorescent microsphere-based assay, 3Flex, that can detect antibodies to three major SARS-CoV-2 antigens—spike (S) protein, the spike ACE2 receptor-binding domain (RBD), and nucleocapsid (NP).
Evaluation of a SARS-CoV-2 Surrogate Virus Neutralization Test for Detection of Antibody in Human, Canine, Cat, and Hamster Sera
Authors: Perera Ranawaka A. P. M. , Ko Ronald , Tsang Owen T. Y. , Hui David S. C. , Kwan Mike Y. M. , Brackman Christopher J. , To Esther M. W. , Yen Hui-ling , Leung Kathy , Cheng Samuel M. S. , Chan Kin Ho , Chan Karl C. K. , Li Ka-Chi , Saif Linda , Barrs Vanessa R. , Wu Joseph T. , Sit Thomas H. C. , Poon Leo L. M. , Peiris Malik
Published: November 2020

Surrogate neutralization assays for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that can be done without biosafety level 3 containment and in multiple species are desirable. We evaluate a recently developed surrogate virus neutralization test (sVNT) in comparison to 90% plaque reduction neutralization tests (PRNT
90
) in human, canine, cat, and hamster sera. With PRNT
90
as the reference, sVNT had sensitivity of 98.9% and specificity of 98.8%. Using a panel of immune sera corresponding to other coronaviruses, we confirm the lack of cross-reactivity to other coronaviruses in SARS-CoV-2 sVNT and PRNT
90
, except for cross-reactivity to SARS-CoV-1 in sVNT.
Middle East Respiratory Syndrome Coronavirus Gene 5 Modulates Pathogenesis in Mice
Authors: Gutierrez-Alvarez Javier , Wang Li , Fernandez-Delgado Raul , Li Kun , McCray Paul B. , Perlman Stanley , Sola Isabel , Zuñiga Sonia , Enjuanes Luis
Published: November 2020

Middle East respiratory syndrome coronavirus (MERS-CoV) is a zoonotic virus causing human infections with high mortality rate (∼35%). Animal models together with reverse-genetics systems are essential to understand MERS-CoV pathogenesis. We developed a reverse-genetics system for a mouse-adapted MERS-CoV that reproduces the virus behavior observed in humans. This system is highly useful to investigate the role of specific viral genes in pathogenesis. In addition, we described a virus lacking gene 5 expression that is more virulent than the parental one. The data provide novel functions in IFN modulation for gene 5 in the context of viral infection and will help to develop novel antiviral strategies.
Dissemination and Stability of the
bla
NDM-5
-Carrying IncX3-Type Plasmid among Multiclonal Klebsiella pneumoniae Isolates
Authors: Zhu Wenjun , Wang Xing , Qin Juanxiu , Liang Wei , Shen Zhen
Published: November 2020

The emergence and spread of New Delhi metallo-β-lactamase (NDM)-producing
Enterobacteriaceae
have been a serious challenge to public health, and NDM-5 shows increased resistance to carbapenems compared with other variants. NDM-5 has been identified mostly in
E. coli
but has rarely been described in
K. pneumoniae
and other
Enterobacteriaceae
isolates. Here, we present the dissemination of highly similar 46-kb IncX3
bla
NDM-5
-carrying plasmids among multiclonal
K. pneumoniae
strains in children, highlighting the horizontal gene transfer of
bla
NDM-5
among
K. pneumoniae
strains via the IncX3 plasmid. Moreover, the IncX3
bla
NDM-5
-carrying plasmids displayed strong stability in clinical strains when cultured in antibiotic-free medium, and the plasmid maintenance was attributed partly to conjugal transfer. Plasmid conjugation is mediated by the type IV secretion system (T4SS), and T4SS is conserved among all epidemic IncX3
bla
NDM-5
-carrying plasmids. Therefore, combining conjugation inhibition and promotion of plasmid loss would be an effective strategy to limit the conjugation-assisted persistence of IncX3
bla
NDM-5
-carrying plasmids.