8 research outputs found
DEM Analysis of Railtrack Ballast Degradation under Monotonic and Cyclic Loading
No full textAbstractThe deformation and the degradation of ballast significantly affect the performance of the railway track. In this study, the discrete element method (DEM) was used to investigate the deformation behavior and degradation characteristics of ballasts under monotonic and cyclic loading. The ballasts were simulated as crushable aggregate which is modeled by bounded discrete elementary particles together and it can be crushed under external forces. The flaw of the aggregate was also modeled by randomly distributed void. Conventional monotonic and cyclic triaxial tests were carried out to investigate the crushing of the aggregates and the associated mechanical behaviors. The effects of confining on the crushing of aggregates and the mechanical behavior were also analyzed. It was found that the permanent deformation of the aggregates significantly increases when particle crushing is considered. The crushing of aggregate is most significant in the first two or three cycles
Sulfolane in contaminated sites: Environmental toxicity and bioremediation technologies
No full textSulfolane is widely used around the world as an industrial solvent for purifying sour natural gas. However, due to accidental spillage and improper on-site storage/disposal procedures, reports of groundwater, aquifer, and soil contaminations have raised concerns about its potential impacts on humans and the ecosystem. As a contaminant of emerging concern, there is a lack of information on the human toxicity of sulfolane. Several bioremediation technologies have been conducted to assess the biodegradation potential of sulfolane in contaminated groundwater and soils. This review presents and discusses the available literature on the toxicity of sulfolane which could be useful for developing proper sulfolane guidelines in different media. The oral LD50 of sulfolane varied from 0.6 to 3.5 g/kg body weight for different mammalian species including guinea pig, mouse, rabbit, and rat. In addition, a review of various sulfolane bioremediation studies to date is also presented highlighting the efficacy of aerobic versus anaerobic bioremediation of sulfolane at contaminated sites. The zero-order biodegradation rate of sulfolane varied from 0.033 to 190 mg/L/day depending on the initial sulfolane concentration, nutrients, oxygen levels, temperature and other parameters. Effective aerobic treatment technologies can lead to the complete mineralization of sulfolane with sulfuric acid as its major end by-product. Furthermore, the application of aerobic granulation as a promising biotechnology for sulfolane biodegradation is also discussed. This review further discusses the significance of utilizing sulfolane degrading bacteria to reduce treatment times and presents information for future researchers and scientists on specific isolates recorded.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
Polyhedral Oligomeric Silsesquioxane (POSS) as Reinforcing Agent for Waterborne Polyurethane Coatings on Wood
No full textPolyhedral oligomeric silsesquioxane (POSS) was added as a reinforcing agent in waterborne polyurethane (WPU)-based coatings to improve their properties. The morphology, structure, thermal stability as well as mechanical properties of the resulting WPU and WPU/POSS hybrid films were investigated. The good compatibility of POSS in the WPU matrices was demonstrated by transmission electron microscopy. Furthermore, Fourier-transform infrared spectroscopy analysis (FTIR) suggested the successful bonding of POSS and WPU matrices. The thermal stability of WPU/POSS hybrids was improved than that of pure WPU according to thermal gravimetric analysis (TGA). The results also revealed the enhancement of the pencil hardness and abrasion resistance of the hybrid films compared with WPU. However, the pull-off adhesion slightly decreased from Grade 0 to Grade 2.</div
High-speed/reliability multilevel FeFET memory with atomic-layer-deposited TiO
No full textAtomic-layer-deposited TiO2-/hafnium zirconium oxide (HZO)-based ferroelectric field-effect transistors (FeFETs) have been fabricated for non-volatile memory applications through a single-step post-device annealing process. In this work, the TiO2 layer serves as both the conductive channel and capping layer, promoting the formation of ferroelectric phase in HZO after annealing at ≥ 350 °C. A memory window of 2 V is obtained under optimized annealing temperature of 600 °C, accompanied by a minimum subthreshold swing and a maximum drain current, and the resulting maximum double remanent polarization (2 ) is 25.2 μC/cm2. Further, the TiO2 FeFET memory with a channel length of 80 nm shows fast program/erase speeds (10 ns under 3 V /4.5 V ), yielding a current window over 102. Stable 2-bit retention and endurance exceeding 109 cycles at 85 °C are achieved. These results suggest the TiO2/HZO FeFET memory is promising for low-power embedded non-volatile memory (eNVM) and monolithic three-dimensional (3D) integration applications
Image Acquisition of Critical Bridge Components Using Vision-guided Autonomous Vehicle
No full textThis research proposes a vision-guided autonomous navigation framework for unmanned vehicles performing image acquisition for bridge inspection. The proposed framework integrates visual SLAM with RGB-D image input with semantic segmentation to detect and localize critical structural components like columns. The detected components are converted to the parametric map to generate navigation goals for image collection. The proposed approach is first validated in the synthetic bridge inspection environment using an unmanned ground vehicle. The feasibility of the framework is further studied by the laboratory-scale prototyping and validation using TurtleBot3 equipped with Jetson TX2 onboard computer. In the simulation environment, the proposed framework can achieve autonomous navigation to up to 6 columns and acquisition of image data with 90% success rate for 3 columns. Furthermore, the performance evaluation in the real-world environment shows that the developed hardware-software prototype can navigate and collect image data of up to 2 columns, with more than 60% success rate navigating to the first column. The results indicate the significant potential of achieving autonomous navigation and image acquisition with limited onboard computational resources, contributing to the enhanced efficiency and reliability of bridge management
Ultrasensitive and fast photoresponse in graphene/silicon-on-insulator hybrid structure by manipulating the photogating effect
No full textThe hybrid structures of graphene with semiconductor materials based on photogating effect have attracted extensive interest in recent years due to the ultrahigh responsivity. However, the responsivity (or gain) was increased at the expense of response time. In this paper, we devise a mechanism which can obtain an enhanced responsivity and fast response time simultaneously by manipulating the photogating effect (MPE). This concept is demonstrated by using a graphene/silicon-on-insulator (GSOI) hybrid structure. An ultrahigh responsivity of more than 107 A/W and a fast response time of 90 µs were obtained. The specific detectivity D* was measured to be 1.46 ⨯ 1013 Jones at a wavelength of 532 nm. The Silvaco TCAD modeling was carried out to explain the manipulation effect, which was further verified by the GSOI devices with different doping levels of graphene in the experiment. The proposed mechanism provides excellent guidance for modulating carrier distribution and transport, representing a new route to improve the performance of graphene/semiconductor hybrid photodetectors
Bioactive Scaffold Fabricated by 3D Printing for Enhancing Osteoporotic Bone Regeneration
No full textWe develop a poly (lactic-co-glycolic acid)/β-calcium phosphate (PLGA/TCP)-based scaffold through a three-dimensional (3D) printing technique incorporating icaritin (ICT), a unique phytomolecule, and secretome derived from human fetal mesenchymal stem cells (HFS), to provide mechanical support and biological cues for stimulating bone defect healing. With the sustained release of ICT and HFS from the composite scaffold, the cell-free scaffold efficiently facilitates the migration of MSCs and promotes bone regeneration at the femoral defect site in the ovariectomy (OVX)-induced osteoporotic rat model. Furthermore, mechanism study results indicate that the combination of ICT and HFS additively activates the Integrin–FAK (focal adhesion kinase)–ERK1/2 (extracellular signal-regulated kinase 1/2)–Runx2 (Runt-related transcription factor 2) axis, which could be linked to the beneficial recruitment of MSCs to the implant and subsequent osteogenesis enhancement. Collectively, the PLGA/TCP/ICT/HFS (P/T/I/S) bioactive scaffold is a promising biomaterial for repairing osteoporotic bone defects, which may have immense implications for their translation to clinical practice
Ultrahigh Photogain Short-Wave Infrared Detectors Enabled by Integrating Graphene and Hyperdoped Silicon
No full textHighly sensitive short-wave infrared (SWIR) detectors,
compatible
with the silicon-based complementary metal oxide semiconductor (CMOS)
process, are regarded as the key enabling components in the miniaturized
system for weak signal detection. To date, the high photogain devices
are greatly limited by a large bias voltage, low-temperature refrigeration,
narrow response band, and complex fabrication processes. Here, we
demonstrate high photogain detectors working in the SWIR region at
room temperature, which use graphene for charge transport and Te-hyperdoped
silicon (Te–Si) for infrared absorption. The prolonged lifetime
of carriers, combined with the built-in potential generated at the
interface between the graphene and the Te–Si, leads to an ultrahigh
photogain of 109 at room temperature (300 K) for 1.55 μm
light. The gain can be improved to 1012, accompanied by
a noise equivalent power (NEP) of 0.71 pW Hz–1/2 at 80 K. Moreover, the proposed device exhibits a NEP of 4.36 pW
Hz–1/2 at 300 K at the wavelength of 2.7 μm,
which is exceeding the working region of InGaAs detectors. This research
shows that graphene can be used as an efficient platform for silicon-based
SWIR detection and provides a strategy for the low-power, uncooled,
high-gain infrared detectors compatible with the CMOS process
