Practical Provably Secure Multi-node Communication

We present a practical and provably-secure multimode communication scheme in the presence of a passive eavesdropper. The scheme is based on a random scheduling approach that hides the identity of the transmitter from the eavesdropper. This random scheduling leads to ambiguity at the eavesdropper with regard to the origin of the transmitted frame. We present the details of the technique and analyze it to quantify the secrecy-fairness-overhead trade-off. Implementation of the scheme over Crossbow Telosb motes, equipped with CC2420 radio chips, shows that the scheme can achieve significant secrecy gain with vanishing outage probability. In addition, it has significant overhead advantage over direct extensions to two-nodes schemes. The technique also has the advantage of allowing inactive nodes to leverage sleep mode to further save energy.Comment: Proceedings of the IEEE International Conference on Computing, Networking and Communications (ICNC 2014

The Roles of Different Committees in ABET Accreditation Process for Engineering Programs

Different engineering degree programs are accredited by the Engineering Accreditation Commission (EAC).  This commission is considered one among the four commissions of the Accreditation Board for Engineering and Technology (ABET).  All programs seeking accreditation from the Engineering Accreditation Commission of ABET must demonstrate that they satisfy all of the eight General Criteria for Baccalaureate Level Programs.  Therefore, to execute these different ABET criteria and guidelines, any engineering program must establish different committees.  In this paper, we nominate different committees and clearly mention their tasks in details. Moreover, the time schedules for the different activities of these committees during both fall and spring semesters are proposed.  Another contribution of this article is to present a robust scheme for continuous improvement process.   The roles of the contribution of some program committees in this scheme are described clearly.  Therefore, the authors thought that the proposed scheme can serve as a strong reference in continuous improvement process for all engineering programs

Electro-chemo-mechanical effects of lithium incorporation in zirconium oxide

Understanding the response of functional oxides to extrinsic ion insertion is important for technological applications including electrochemical energy storage and conversion, corrosion, and electronic materials in neuromorphic computing devices. Decoupling the complicated chemical and mechanical effects of ion insertion is difficult experimentally. In this work, we assessed the effect of lithium incorporation in zirconium oxide as a model system, by performing first-principles based calculations. The chemical effect of lithium is to change the equilibria of charged defects. Lithium exists in ZrO_{2} as a positively charged interstitial defect, and raises the concentration of free electrons, negatively charged oxygen interstitials, and zirconium vacancies. As a result, oxygen diffusion becomes faster by five orders of magnitude, and the total electronic conduction increases by up to five orders of magnitude in the low oxygen partial pressure regime. In the context of Zr metal oxidation, this effect accelerates oxide growth kinetics. In the context of electronic materials, it has implications for resistance modulations via ion incorporation. The mechanical effect of lithium is in changing the volume and equilibrium phase of the oxide. Lithium interstitials together with zirconium vacancies shrink the volume of the oxide matrix, release the compressive stress that is needed for stabilizing the tetragonal phase ZrO_{2} at low temperature, and promote tetragonal-to-monoclinic phase transformation. By identifying these factors, we are able to mechanistically interpret experimental results in the literature for zirconium alloy corrosion in different alkali-metal hydroxide solutions. These results provide a mechanistic and quantitative understanding of lithium-accelerated corrosion of zirconium alloy, as well as, and more broadly, show the importance of considering coupled electro-chemo-mechanical effects of cation insertion in functional oxides

Predicting point defect equilibria across oxide hetero-interfaces: model system of ZrO2/Cr2O3

We present a multi-scale approach to predict equilibrium defect concentrations across oxide/oxide hetero-interfaces. There are three factors that need to be taken into account simultaneously for computing defect redistribution around the hetero-interfaces: the variation of local bonding environment at the interface as epitomized in defect segregation energies, the band offset at the interface, and the equilibration of the chemical potentials of species and electrons via ionic and electronic drift-diffusion fluxes. By including these three factors from the level of first principles calculation, we build a continuum model for defect redistribution by concurrent solution of Poisson's equation for the electrostatic potential and the steady-state equilibrium drift-diffusion equation for each defect. This model solves for and preserves the continuity of the electric displacement field throughout the interfacial core zone and the extended space charge zones. We implement this computational framework to a model hetero-interface between the monoclinic zirconium oxide, m-ZrO[subscript 2], and the chromium oxide Cr[subscript 2]O[subscript 3]. This interface forms upon the oxidation of zirconium alloys containing chromium secondary phase particles. The model explains the beneficial effect of the oxidized Cr particles on the corrosion and hydrogen resistance of Zr alloys. Under oxygen rich conditions, the ZrO[subscript 2]/Cr[subscript 2]O[subscript 3] heterojunction depletes the oxygen vacancies and the sum of electrons and holes in the extended space charge zone in ZrO[subscript 2]. This reduces the transport of oxygen and electrons thorough ZrO[subscript 2] and slows down the metal oxidation rate. The enrichment of free electrons in the space charge zone is expected to decrease the hydrogen uptake through ZrO[subscript 2]. Moreover, our analysis provides a clear anatomy of the components of interfacial electric properties; a zero-Kelvin defect-free contribution and a finite temperature defect contribution. The thorough analytical and numerical treatment presented here quantifies the rich coupling between defect chemistry, thermodynamics and electrostatics which can be used to design and control oxide hetero-interfaces

Doping in the Valley of Hydrogen Solubility: A Route to Designing Hydrogen-Resistant Zirconium Alloys

Hydrogen pickup and embrittlement pose a challenging safety limit for structural alloys used in a wide range of infrastructure applications, including zirconium alloys in nuclear reactors. Previous experimental observations guide the empirical design of hydrogen-resistant zirconium alloys, but the underlying mechanisms remain undecipherable. Here, we assess two critical prongs of hydrogen pickup through the ZrO[subscript 2] passive film that serves as a surface barrier of zirconium alloys; the solubility of hydrogen in it—a detrimental process—and the ease of H[subscript 2] gas evolution from its surface—a desirable process. By combining statistical thermodynamics and density-functional-theory calculations, we show that hydrogen solubility in ZrO[subscript 2] exhibits a valley shape as a function of the chemical potential of electrons, μ[subscript e]. Here, μ[subscript e], which is tunable by doping, serves as a physical descriptor of hydrogen resistance based on the electronic structure of ZrO[subscript 2]. For designing zirconium alloys resistant against hydrogen pickup, we target either a dopant that thermodynamically minimizes the solubility of hydrogen in ZrO[subscript 2] at the bottom of this valley (such as Cr) or a dopant that maximizes μ[subscript e] and kinetically accelerates proton reduction and H[subscript 2] evolution at the surface of ZrO[subscript 2] (such as Nb, Ta, Mo, W, or P). Maximizing μ[subscript e] also promotes the predomination of a less-mobile form of hydrogen defect, which can reduce the flux of hydrogen uptake. The analysis presented here for the case of ZrO[subscript 2] passive film on Zr alloys serves as a broadly applicable and physically informed framework to uncover doping strategies to mitigate hydrogen embrittlement also in other alloys, such as austenitic steels or nickel alloys, which absorb hydrogen through their surface oxide films.United States. Dept. of Energy. Energy Innovation Hub for Modeling and Simulation of Nuclear Reactors. Consortium for Advanced Simulation of Light Water Reactors (Contract DE-AC05-00OR22725)MIT-China Scholarship Council (Fellowship

Performance of Isolated Footing with Several Corrosion Levels under Axial Loading

This research aims to illustrate the corrosion process and its effect on the deterioration of reinforced concrete (RC) isolated footings using a small-scale model (1/8) and present the results of a prototype-scale study using a numerical model with different concrete depths and corrosion levels under axial load. The experimental program consisted of testing five small-scale (1/8) model RC isolated footings under axial loading after subjecting them to accelerated corrosion tests with a constant current. The main variable in the small-scale sample test was the corrosion level. This study presents an experimental approach, using the constant current method and the finite element method (FEM) with the ABAQUS package, to examine its effect on the axial load behavior under different corrosion ratios, which were 0%, 4.21%, 9.11%, 24.56%, and 30.67%. On the prototype scale, the variables were the corrosion level and the RC depths of 300 mm, 400 mm, and 500 mm. The results indicated that the average deviation in ultimate load between the experimental and FEM outcomes for the small-scale was below 5.6%, while the average deflection deviation was 6.8%. Also, the study found that an increase in the depth of the RC footing and corrosion ratio led to a more pronounced impact of the cracking pattern in the concrete and corroded bars, as well as a greater difference in the failure load. The experimental results suggest that the proposed numerical model is accurate and effective. These findings have important implications for the evaluation of isolated footings affected by corrosion damage using FEM, and can help inform decisions related to their design and maintenance. The failure loads of non-corroded footings with different depths were compared with the ECP-203 provisions of the 2018 Egyptian Code, and how corrosion ratios can be simulated by numerical models. The percentage variation between the design loads by code and the numerical loads by ABAQUS for controlled footings with thicknesses of 300, 400, and 500 mm was found to be 73%, 80%, and 78%, respectively. Using the derived relationship, the equivalent corrosion ratio percentages were 23.8%, 20.2%, and 32%, respectively. Doi: 10.28991/CEJ-2023-09-06-011 Full Text: PD

Enhanced Torsion Mechanism of Small-Scale Reinforced Concrete Beams with Spiral Transverse Reinforcement

The nonlinear torsional behaviour of small-scale reinforced concrete (RC) beams with continuous staggered spiral as transverse reinforcement stirrups is experimentally investigated. Twelve miniatures RC beams were tested under torsion load considering the closed shape of stirrups and compared with continuous staggered spiral ones. All miniatures beams were scaled down to be one-eighth the prototype beam size. The main parameters considered in this research are stirrup spacing and its configurations. Small scale RC beams were taken into account in the existing study because of their construction simplicity and financial feasibility. Mortar without coarse aggregate was applied instead of concrete to reduce the size effect of applying small scale models. Ongoing research trials have been carried out to obtain an efficacious approach to boost torsion failure mechanisms because brittle torsion failure of RC structural elements should be avoided. This study emphasized boosted torsion capacity, dissipated energy, and helical crack propagation. During testing, the primary cracking torsion moment, ultimate torsion moment, peak twist angle, and failure mechanism of the beams were inspected. The use of spiral stirrups showed great enhancement of the torsional behaviour of samples. It was observed that using spiral stirrups rather than closed stirrups could result in a substantial increase in torsion capacity and dissipated energy of 87.7% and 89.8%, respectively. As a result, the predicted capacities of the RC beams prototype were estimated in detail, taking account the scale down factor implemented by the authors. Values obtained based on international specifications and guidelines were used to compare the experimental results. Doi: 10.28991/CEJ-2022-08-11-019 Full Text: PD