skip to main content

Search for: All records

Creators/Authors contains: "Xu, Z."

Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?

Some links on this page may take you to non-federal websites. Their policies may differ from this site.

  1. Free, publicly-accessible full text available March 25, 2024
  2. Current best practices for the assessment of the cyclic response of plastic silts are centered on the careful sampling and cyclic testing of natural, intact specimens. Side-by-side evaluation of in-situ and laboratory element test responses are severely limited, despite the need to establish similarities and differences in their characteristics. In this paper, a coordinated laboratory and field-testing campaign that was undertaken to compare the strain-controlled cyclic response of a plastic silt deposit at the Port of Longview, Longview, WA is described. Following a discussion of the subsurface conditions at one of several test panels, the responses of laboratory test specimens to resonant column and cyclic torsional shear testing, and constant-volume, strain-controlled cyclic direct simple shear testing are described in terms of shear modulus nonlinearity and degradation, and excess pore pressure generation with shear strain. Several months earlier, the in-situ cyclic response of the same deposit was investigated by applying a range of shear strain amplitudes using a large mobile shaker. The in-situ response is presented and compared to the laboratory test results, highlighting similarities and differences arising from differences in mechanical (e.g., constant-volume shearing; strain rate-effects) and hydraulic (e.g., local drainage) boundary conditions and the spatial variability of natural soil deposits. 
    more » « less
  3. This convergent mixed method study investigates learner engagement during a blended, transmedia curriculum called CryptoComics which is designed to teach 3rd-5th graders about cryptology and cybersecurity. Curriculum design is presented through the lens of four engagement facilitators: (1) anchoring the curriculum with a comic book, (2) blending digital and unplugged media, (3) supporting situational interest via a transmedia narrative and (4) designing for social-cultural relevance. Latent profile analysis is used to develop profiles of learner engagement using quantitative indicators of cognitive and emotional engagement collected across 204 students at 13 implementation sites in the Eastern U.S. Qualitative indicators of engagement include teacher weekly check-ins submitted by 17 teachers working at the 13 implementation sites, student interviews, and classroom observations of 26 students participating in the curriculum at two local sites. Quantitative and qualitative results converge to suggest the majority of the students participating in the curriculum were highly engaged cognitively and emotionally. Qualitative data (1) suggest some third graders may be less cognitively engaged due to challenging content, (2) provide evidence for how design of the blended, transmedia curriculum supported, and some cases hindered, engagement, (3) highlight the importance of transitions between blended learning components in facilitating engagement and (4) uncover questions regarding one of the quantitative measures selected as an indicator of cognitive engagement. 
    more » « less
  4. K-12 teachers and students are vulnerable to cybersecurity attacks and mostly ill-prepared to deal with them. The CO- VID-19 pandemic has only increased these risks because of the reliance on digital technology in education and increased free time young children and adolescents spend online. Simultaneously, the U.S. is facing an extreme shortage of cybersecurity professionals. Given the rise of cyberattacks and the need for cybersecurity professionals, a concerted effort to prepare preservice teachers to integrate cybersecurity education across the K-12 curriculum is needed. In our vision for 2025, all preservice teachers across the country are prepared to integrate age-appropriate cybersecurity concepts, skills and career awareness in the curriculum regardless of their content area or grade level specialization. We propose a repository of stand-alone activities and full curricula developed through collaboration among K-12 educators, teacher educators, and cybersecurity experts that could be adopted across teacher education programs. We use the elementary grades as a con- text for providing examples of some activities that might be included in the repository. We also provide recommendations for developing such a repository and for individual teacher educators who want integrate cybersecurity education in pre-service teacher education right now. 
    more » « less
  5. Filipe, J. ; Ghosh, A. ; Prates, R. O. ; Zhou, L. (Ed.)
    This paper considers a parallel wireless network in which multiple individuals exchange confidential information through independent sender-receiver links. An eavesdropper can intercept encrypted information through a degraded channel of each sender-receiver link. A friendly jammer, by applying interference to the eavesdropping channels, can increase the level of secrecy of the network. The optimal power allocation strategy of the friendly jammer under a power constraint is derived. A convex optimization model is used when all channels are under the threat of an eavesdropping attack and a non-zero sum game model is analyzed when the eavesdropper can only attack a limited quantity of channels. 
    more » « less