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For artificial materials, desired properties often conflict. For example, engineering materials often achieve high energy dissipation by sacrificing resilience and vice versa, or desired auxeticity by losing their isotropy, which limits their performance and applications. To solve these conflicts, a strategy is proposed to create novel mechanical metamaterial via 3D space filling tiles with engaging key‐channel pairs, exemplified via auxetic 3D keyed‐octahedron–cuboctahedron metamaterials. This metamaterial shows high resilience while achieving large mechanical hysteresis synergistically under large compressive strain. Especially, this metamaterial exhibits ideal isotropy approaching the theoretical limit of isotropic Poisson's ratio, ‐1, as rarely seen in existing 3D mechanical metamaterials. In addition, the new class of metamaterials provides wide tunability on mechanical properties and behaviors, including an unusual coupled auxeticity and twisting behavior under normal compression. The designing methodology is illustrated by the integral of numerical modeling, theoretical analysis, and experimental characterization. The new mechanical metamaterials have broad applications in actuators and dampers, soft robotics, biomedical materials, and engineering materials/systems for energy dissipation.

 

This paper discusses the instructional design experiences and processes shared by a multi-disciplinary group—including more than a dozen faculty, staff, and students—while developing a series of online courses on Model-based Systems Engineering (MBSE) for professional engineers, a project sponsored by the National Science Foundation. The team size, the complexity and uniqueness of the subject matter, the targeted learners, and the pre-determined research questions created a rare situation in which the team members collaborated and/or negotiated outside the realm of the traditional instructional design process. Over time the team went through two different types of instructional design processes, beginning with a waterfall-type process where the communication between the subject matter experts (SME) and the design team was somewhat limited and finally evolving to a collaborative process where the interaction between the two teams was more direct and immediate. The evolution of the design process and the dynamics between the SMEs and the design team resulted in several major design revisions implemented to improve the quality of the online courses.

 

In the study, a series of wind tunnel tests were conducted to investigate wind effects acting on dome structures (1/60 scale) induced by straight-line winds at a Reynolds number in the order of 106. Computational Fluid Dynamics (CFD) simulations were performed as well, including a Large Eddy Simulation (LES) and Reynolds-Averaged Navier–Stokes (RANS) simulation, and their performances were validated by a comparison with the wind tunnel testing data. It is concluded that wind loads generally increase with upstream wind velocities, and they are reduced over suburban terrain due to ground friction. The maximum positive pressure normally occurs near the base of the dome on the windward side caused by the stagnation area and divergence of streamlines. The minimum suction pressure occurs at the apex of the dome because of the blockage of the dome and convergence of streamlines. Suction force is the most significant among all wind loads, and special attention should be paid to the roof design for proper wind resistance. Numerical simulations also indicate that LES results match better with the wind tunnel testing in terms of the distribution pattern of the mean pressure coefficient on the dome surface and total suction force. The mean and root-mean-square errors of the meridian pressure coefficient associated with the LES are about 60% less than those associated with RANS results, and the error of suction force is about 40–70% less. Moreover, the LES is more accurate in predicting the location of boundary layer separation and reproducing the complex flow field behind the dome, and is superior in simulating vortex structures around the dome to further understand the unsteadiness and dynamics in the flow field.

 

This full research paper presents the exploratory factor analysis (EFA) results for the Professional Skill Opportunities survey (PSO) we designed to measure undergraduate engineering students’ opportunities to develop and practice important nontechnical professional skills. We use Dall’alba’s “ways of being” as the theoretical framework for the survey development and generated construct definitions based on past literature, expert review, and cognitive think-aloud interviews. We administered the survey in an engineering class at the beginning of the Spring 2022 semester. After comparing the three EFA models based on goodness-of-fit indices and model interpretability aligned to the theoretical model, the researchers selected a five-factor model. The EFA result and literature on leadership and teamwork showed these two skills are highly interrelated and could be combined into one construct to stress the “sharedness” of leadership responsibilities in teams. The result allowed our team to refine our item pool, revise construct definitions, and generate new items. In future work, we will administer the revised PSO survey to the same population at the end of the same semester as further validation. We also plan to explore the relationship between professional skill development opportunities and students’ social support. We hope the PSO survey can provide educators and institutions a means to offer scaffoldings and more opportunities for professional skill development and better prepare students for the engineering workforce. 

As the need for interdisciplinary collaboration increases, industry needs engineers who are not only affluent in technical engineering skills but also efficient in skills such as communication, problem-solving, engineering ethics, and business management. As a result, engineering programs are tasked with providing students with sufficient opportunities to develop non-technical professional skills to better prepare them for the workforce. Previous research has focused on exploring how and where students tend to develop profession skills and assessments have been established to measure the level of professional skills. However, without a means to measure whether students are getting sufficient opportunities for development, it is hard for educators and engineering programs to determine whether or where scaffolding are needed. We developed an instrument to assess undergraduate engineering students’ opportunities for professional skill development. To increase content validity, we conducted 20 think-aloud interviews with students from a large Midwestern university. The aim of this WIP is two-fold. We present the preliminary results of the think-aloud interview to determine what changes need to be made to existing items and what emerging themes appear regarding to participants’ professional skill development opportunities. After thematic analysis of the interview transcripts, we revised 10 items by simplifying the grammar or altering certain words that tend to confuse participants or carry negative connotations. We found that, compared to students who have only been involved in class projects, those with co-curricular experiences tend to report more opportunities in skills related to business management principles and problem-solving skills. Co-curricular activities were also the most referenced in building communication skills. Our next step will be piloting the instrument across multiple institutions and conducting validation analysis. 

We demonstrate a silicon photonic passive PT-symmetric structure operating at an exceptional point, with dynamic mode-splitting tunability enabled by a local heater.