43 research outputs found
Data associated with publication: "Separating geometric and diffusive contributions to the surface nucleation of dislocations in nanoparticles" by R. Ding, S. Azadehranjbar, I.M. Padilla Espinosa, A. Martini, and T.D.B. Jacobs, published in ACS Nano, 2024
No full textData associated with publication: "Separating geometric and diffusive contributions to the surface nucleation of dislocations in nanoparticles" by R. Ding, S. Azadehranjbar, I.M. Padilla Espinosa, A. Martini, and T.D.B. Jacobs, published in ACS Nano, 202
Data associated with publication: "Mechanical behavior and size–dependent strength of small noble-metal nanoparticles" by R. Ding, A. Martini, T.D.B. Jacobs, published in Acta Materialia, 2025
No full textWhile metal nanoparticles are foundational to many advanced technologies, the instability of small particles limits their performance and lifetime. Extensive prior work has demonstrated size-dependent behavior, including “smaller-is-stronger”, “smaller-is-weaker”, and “liquid-like deformation”. However, mechanistic understanding of deformation processes has been hampered by the difficulty of characterizing nanoparticles as they fail. Here, we have compressed nanoparticles to failure with in situ transmission electron microscopy, linking their strength to direct observation of failure mechanisms. More than 250 tests, conducted on particles of Au, Ag, and Pt with sizes ranging from 3 to 130 nm, reveal a complex, non-monotonic dependence of strength on particle size. Deformation in larger particles (130 nm down to approximately 15 nm) is carried by dislocations nucleating from the surface. Without any observable change in mechanism, the nanoparticles first exhibit strengthening with decreasing size, reach a peak strength at around 30–60 nm, then show weakening. Deformation in intermediate-size particles (15 to approximately 5 nm) exhibits a mix of plasticity and diffusive deformation. Finally, the very smallest particles, with single-digit-nanometer sizes, exhibit homogeneous diffusive deformation that contradicts recent theories, and is instead well described by the zero-creep analysis. Overall, this work reveals the regimes and mechanisms underlying nanoparticle failure, across sizes and across materials
Mechanical characterization of tissue mimicking phantoms by broadband surface acoustic waves
No full textSurface acoustic waves (SAWs) shows great potential in non-destructive mechanical characterization, it promises a non-invasive method of diagnosis of cirrhosis cutaneous and subcutaneous tissues. This paper explores a rapid way to evaluate the elastic property of soft tissue mimicking phantom by the analysis of SAWs phase velocity. An electromagnetic shaker with a line source was used to generate SAWs by square wave stimulus. A laser-vibrometer with displacement decoding mode was used to detect the SAWs. The phase velocities on agar phantoms were estimated. The result showed that the evaluation of SAWs phase velocity could be served as an accurate and rapid estimation of elasticity properties of soft materials
A Security Authentication Protocol for Trusted Domains in an Autonomous Decentralized System
Get PDFabstract: Software Defined Network (SDN) architecture has been widely used in various application domains. Aiming at the authentication and security issues of SDN architecture in autonomous decentralized system (ADS) applications, securing the mutual trust among the autonomous controllers, we combine trusted technology and SDN architecture, and we introduce an authentication protocol based on SDN architecture without any trusted third party between trusted domains in autonomous systems. By applying BAN predicate logic and AVISPA security analysis tool of network interaction protocol, we can guarantee protocol security and provide complete safety tests. Our work fills the gap of mutual trust between different trusted domains and provides security foundation for interaction between different trusted domains.View the article as published at http://journals.sagepub.com/doi/10.1155/2016/532794
Positive-definite conditions of elastic constants of two-dimensional quasicrystals with noncrystallographic symmetries
No full textIn the present work, the positive-definite conditions of the elastic constants of two-dimensional (2D) quasicrystals with non-crystallographic symmetries have been derived. These results are necessary for studying elastic and mechanical properties of two-dimensional quasicrystals both in theory and in experiment.</jats:p
Going beyond traditional roughness metrics for floor tiles: Measuring topography down to the nanoscale
Get PDFSlipping is a major cause of injury and hospitalization in the United States and globally. Slipping occurs when the instantaneous friction between the shoe and floor is less than the required friction. While floor roughness is a key factor contributing to friction, prior investigations have primarily used stylus profilometry, which is incapable of measuring roughness at small scales, below approximately 1 micron in lateral size. In the present research, the small-scale roughness was quantified using cross-section scanning electron microscopy (SEM). Three different flooring materials were investigated, including tiles of ceramic and two different types of quarry stones, whose friction coefficients had been previously characterized. The surfaces were cross-sectioned, imaged at magnifications from 250 to 100,000 times, and then the surface profiles were extracted using image analysis. The SEM topography was combined with stylus profilometry measurements, using the power spectral density (PSD), to achieve multi-scale characterization of features ranging from a scan size of 4 mm down to a resolution of 10 nm. The results demonstrate meaningful differences in topography at different length scales, where surfaces with widely varying roughness at one scale were indistinguishable at another. The measurements further showed that floor-tile roughness has self-affine fractal-like character, with hierarchical roughness extending from the micron-scale down to the nanoscale, much of which is undetectable using conventional techniques. Overall, this research supports the investigation of small-scale roughness as a potential missing factor in the understanding of floor topography and its causal effect on slip-and-fall accidents
Investigation of parameters affecting the presence of airborne indoor particles and the resulting exposures
No full textAdverse health effects caused by exposure to indoor airborne particulate matter (PM) drive the need to understand the behavior of indoor PM and be able to measure the presence of and exposure to indoor PM. The overall goal of this dissertation was to improve our understanding of factors affecting indoor particle concentrations and related human exposures. To achieve this goal, the work presented in this dissertation used various tools, including consumer-grade and professional-grade air quality monitors. Consumer-grade air quality monitors provide an easier and more affordable way to simultaneously measure particle concentrations in multiple locations, providing new capabilities to investigate PM. In contrast, professional-grade air quality monitors provide more accurate and robust particle concentration readings. The goal of the dissertation was accomplished through the following aims. Aim 1: Compare the performance of two consumer-grade monitors (Foobot and AirVisual Node) with a professional-grade instrument DustTrak DRX (TSI Inc.). The devices were compared in two laboratory environments and one residential apartment when measuring five types of aerosols (0.72 and 2.00 µm polystyrene latex (PSL) spheres, Arizona Road Dust (ARD), nanosilver-based surface cleaner, and particles created by a cooking event). The low-cost monitors were highly correlated with the DustTrak DRX for most aerosol types (r > 0.78), except when measuring nanosilver spray, where the r value decreased to 0.55. AirVisual showed lower precision errors than Foobot for most types of aerosols. Both consumer monitors showed high accuracy and precision when measuring temperature and humidity compared to the professional-grade IAQ Meter (TSI Inc.). AirVisual showed high accuracy and precision when measuring CO2 compared to the IAQ meter, while Foobot didn't report accurate CO2 concentrations.
Aim 2: Investigate the effect of heatwaves on indoor PM2.5 levels and analyze modifying factors. Heatwaves are known to result in negative health effects, and the increase in temperature and air pollution plays an important role in the increasing mortality and morbidity during heatwaves. However, the effect of high outdoor temperatures on indoor air quality is largely unknown. Thus, we hypothesized that heatwaves (i.e., high outdoor temperatures) increase indoor PM2.5 levels. Here, we examined the PM2.5 levels in apartments of the low-income elderly population using consumer-grade air quality monitors (AirVisual selected from Aim 1) from July to September 2017. We found that the average hourly indoor PM2.5 levels varied substantially among apartments, and apartments with smokers showed much higher indoor PM2.5 levels than apartments with non-smokers. Days with high temperatures (heatwave days) showed statistically significantly higher PM2.5 levels than non-heatwave days for both smokers’ and non-smokers’ apartments. During heatwave days, average hourly PM2.5 levels increased by 33.4 μg/m3 in smokers’ units and 5.0 μg/m3 in non-smokers’ units compared to non-heatwave days. Moreover, we separated the data into an active period (6:00 a.m. to 10:00 p.m.) and the rest period (10:00 p.m. to the next day 6:00 a.m.) and found that the PM2.5 during heatwaves was statistically significantly higher than during non-heatwave days for both periods.
Aim 3: Quantify the resuspension of particles from the nanotechnology-based sprays and determine factors that affect the resuspension of such particles. The release, deposition, and resuspension of particles from nano-enabled consumer products are becoming an important indoor particle source. However, there was a lack of data on the resuspension of particles from such sprays. We hypothesized that settled particles from nanotechnology-based consumer sprays could be resuspended by human walking and that the resuspension could be affected by the spray type, flooring type, and resuspension force. To achieve this goal, we investigated particle concentrations during the spraying and resuspension of nanotechnology-based consumer sprays using professional-grade air quality monitors. We also examined the effect of product type, flooring material, and resuspension force on particle resuspension. The measured resuspension rates ranged from 10−4 to 5 × 10−1 h−1, depending on the product (seven products were investigated), flooring material (e.g., carpet and vinyl), and resuspension force (e.g., a walking adult and a moving child; the latter was simulated by a robotic sampler). The resuspension rate from the carpet was statistically significantly higher than that from vinyl flooring, while the resuspension rate caused by the adult was statistically significantly higher than that by the robot.
Aim 4: Estimate personal exposures and area exposure of adults and children to the releases and resuspended particles from nano-enabled consumer sprays and estimate factors affecting the exposures. Indoor exposures are often estimated using stationary samplers; however, they might not accurately predict personal exposures. The latter should be measured using personal samplers. We hypothesized that personal exposures due to spraying and resuspension of nanotechnology-based consumer sprays differ from exposure estimates based on stationary samplers and that exposure of children to said particles is higher than that of adults. The investigated factors affecting exposures included the spray type, flooring material type, resuspension force, and measurement heights. A robotic sampler was used to simulate the movement of young children. The results showed that children could be exposed to higher particle mass concentrations than adults during spraying and resuspension of consumer sprays. The resuspension from the carpet led to higher exposure of both adults and children than resuspension from vinyl. Compared to particle resuspension by the robot, walking by an adult led to higher exposure to resuspended particles for adults and children. Ph.D.Includes bibliographical reference
A Combination of Ilizarov Frame, Externalized Locking Plate and Tibia Bridging for an Adult with Large Tibial Defect and Severe Varus Deformity Due to Chronic Osteomyelitis in Childhood: A Case Report
No full textBackground: Various techniques have been reported to treat large, segmental tibial defects, such as autogenous bone graft, vascularized free fibula transfer and bone transport. We present a case of a 24-year-old male with a 17-year history of chronic osteomyelitis with obvious lower limb length discrepancy and severe varus deformity of the tibia secondary to osteomyelitis in childhood. Aim: The aim of this work is to provide an alternative choice for treating patients in developing countries with severe lower limb deformity caused by chronic osteomyelitis. Case Presentations: Without surgical intervention for a prolonged period of time, the patient was admitted in our institute for corrective surgery. Corrective surgery consisted of three stages: lengthening with Ilizarov frame, removal of Ilizarov frame and fixation with externalized locking plate, and removal of externalized locking plate. Tibia bridging was achieved at the distal and proximal junction. The range of motion (ROM) of the knee joint was nearly normal, but the stiffness of the ankle joint was noticeable. The remaining leg discrepancy of 0.1 cm required no application of a shoe lift. Moreover, the patient could engage in daily activities without noted limping. Conclusions: Distraction–compression osteogenesis using the Ilizarov apparatus is a powerful tool to lengthen the shortened long bone and adjust the deformity of the lower limbs. Externalized locking plates provide an alternative to the traditional bulky external fixator, as its low profile makes it more acceptable to patients without compromising axial and torsional stiffness. In all, a combination of Ilizarov frame, externalized locking plate and tibia bridging is an alternative for patients in similar conditions
AllTheDocks road safety dataset: A cyclist's perspective and experience
Get PDFActive travel is an essential component in intelligent transportation
systems. Cycling, as a form of active travel, shares the road space with
motorised traffic which often affects the cyclists' safety and comfort and
therefore peoples' propensity to uptake cycling instead of driving. This paper
presents a unique dataset, collected by cyclists across London, that includes
video footage, accelerometer, GPS, and gyroscope data. The dataset is then
labelled by an independent group of London cyclists to rank the safety level of
each frame and to identify objects in the cyclist's field of vision that might
affect their experience. Furthermore, in this dataset, the quality of the road
is measured by the international roughness index of the surface, which
indicates the comfort of cycling on the road. The dataset will be made
available for open access in the hope of motivating more research in this area
to underpin the requirements for cyclists' safety and comfort and encourage
more people to replace vehicle travel with cycling
