More Like this

1. CFD–DEM Analysis of Internal Soil Erosion Induced by Infiltration into Defective Buried Pipes

   https://doi.org/10.3390/geosciences15070253  

   Xu, Jun; Wang, Fei; Vaughan, Bryce (July 2025, Geosciences)

   Internal soil erosion caused by water infiltration around defective buried pipes poses a significant threat to the long-term stability of underground infrastructures such as pipelines and highway culverts. This study employs a coupled computational fluid dynamics–discrete element method (CFD–DEM) framework to simulate the detachment, transport, and redistribution of soil particles under varying infiltration pressures and pipe defect geometries. Using ANSYS Fluent (CFD) and Rocky (DEM), the simulation resolves both the fluid flow field and granular particle dynamics, capturing erosion cavity formation, void evolution, and soil particle transport in three dimensions. The results reveal that increased infiltration pressure and defect size in the buried pipe significantly accelerate the process of erosion and sinkhole formation, leading to potentially unstable subsurface conditions. Visualization of particle migration, sinkhole development, and soil velocity distributions provides insight into the mechanisms driving localized failure. The findings highlight the importance of considering fluid–particle interactions and defect characteristics in the design and maintenance of buried structures, offering a predictive basis for assessing erosion risk and infrastructure vulnerability. 

   more » « less
2. High-pressure, high-temperature molecular doping of nanodiamond

   https://doi.org/10.1126/sciadv.aau6073  

   Crane, M. J.; Petrone, A.; Beck, R. A.; Lim, M. B.; Zhou, X.; Li, X.; Stroud, R. M.; Pauzauskie, P. J. (May 2019, Science Advances)

   The development of color centers in diamond as the basis for emerging quantum technologies has been limited by the need for ion implantation to create the appropriate defects. We present a versatile method to dope diamond without ion implantation by synthesis of a doped amorphous carbon precursor and transformation at high temperatures and high pressures. To explore this bottom-up method for color center generation, we rationally create silicon vacancy defects in nanodiamond and investigate them for optical pressure metrology. In addition, we show that this process can generate noble gas defects within diamond from the typically inactive argon pressure medium, which may explain the hysteresis effects observed in other high-pressure experiments and the presence of noble gases in some meteoritic nanodiamonds. Our results illustrate a general method to produce color centers in diamond and may enable the controlled generation of designer defects. 

   more » « less
3. Arc-Phase Spark Plug Energy Deposition Characteristics Measured Using a Spark Plug Calorimeter Based on Differential Pressure Measurement

   https://doi.org/10.3390/en13143550  

   Kim, Kyeongmin; Hall, Matthew J.; Wilson, Preston S.; Matthews, Ronald D. (July 2020, Energies)

   null (Ed.)

   A spark plug calorimeter is introduced for quantifying the thermal energy delivered to unreactive gas surrounding the spark gap during spark ignition. Unlike other calorimeters, which measure the small pressure rise of the gas above the relatively high gauge pressure or relative to an internal reference, the present calorimeter measured the differential rise in pressure relative to the initial pressure in the calorimeter chamber. By using a large portion of the dynamic range of the chip-based pressure sensor, a high signal to noise ratio is possible; this can be advantageous, particularly for high initial pressures. Using this calorimeter, a parametric study was carried out, measuring the thermal energy deposition in the gas and the electrical-to-thermal energy conversion efficiency over a larger range of initial pressures than has been carried out previously (1–24 bar absolute at 298 K). The spark plug and inductive ignition circuit used gave arc-type rather than glow-type discharges. A standard resistor-type automotive spark plug was tested. The effects of spark gap distance (0.3–1.5 mm) and ignition dwell time (2–6 ms) were studied for an inductive-type ignition system. It was found that energy deposition to the gas (nitrogen) and the electrical-to-thermal energy conversion efficiency increased strongly with increasing gas pressure and spark gap distance. For the same ignition hardware and operating conditions, the thermal energy delivered to the gap varied from less than 1 mJ at 1 atm pressure and a gap distance of 0.3 mm to over 25 mJ at a pressure of 24 bar and a gap distance of 1.5 mm. For gas densities that might be representative of those in an engine at the time of ignition, the electrical-to-thermal energy conversion efficiencies ranged from approximately 3% at low pressures (4 bar) and small gap (0.3 mm) to as much as 40% at the highest pressure of 24 bar and with a gap of 1.5 mm. 

   more » « less
4. Controlling process instability for defect lean metal additive manufacturing

   https://doi.org/10.1038/s41467-022-28649-2  

   Qu, Minglei; Guo, Qilin; Escano, Luis I.; Nabaa, Ali; Hojjatzadeh, S. Mohammad H.; Young, Zachary A.; Chen, Lianyi (February 2022, Nature Communications)

   Abstract The process instabilities intrinsic to the localized laser-powder bed interaction cause the formation of various defects in laser powder bed fusion (LPBF) additive manufacturing process. Particularly, the stochastic formation of large spatters leads to unpredictable defects in the as-printed parts. Here we report the elimination of large spatters through controlling laser-powder bed interaction instabilities by using nanoparticles. The elimination of large spatters results in 3D printing of defect lean sample with good consistency and enhanced properties. We reveal that two mechanisms work synergistically to eliminate all types of large spatters: (1) nanoparticle-enabled control of molten pool fluctuation eliminates the liquid breakup induced large spatters; (2) nanoparticle-enabled control of the liquid droplet coalescence eliminates liquid droplet colliding induced large spatters. The nanoparticle-enabled simultaneous stabilization of molten pool fluctuation and prevention of liquid droplet coalescence discovered here provide a potential way to achieve defect lean metal additive manufacturing. 

   more » « less
5. A nanofluidics study on nanoscale gas bubble defects in dispensing-based nanoimprint lithography

   https://doi.org/10.1109/NANO.2017.8117426  

   Li, Da; Ma, Xiaobai; Li, Nan; Hossein, Rokbi; Lu, Wei; Yu, Zhaoning; Liang, Xiaogan (July 2017, Proceedings of the 17th IEEE International Conference on Nanotechnolog)

   Detrimental nanoscale gas bubble defects seriously hinder the practical applications of nanoimprint lithography in manufacturing of nanoelectronic devices. Here, we present a nanofluidics study on the formation and evolution mechanisms of nanoscale bubble defects in dispensing-based UV-curable nanoimprint lithography processes. Our work indicates that the formation of nanoscale bubble defects is mainly attributed to the pinning of resist spreading edges at the nanostructures or contaminants on the mold/substrate surfaces. Such pinning-induced nanoscale gas bubbles undergo an evolution process governed by the combinational effect of surface pinning and gas dissolution into resist. Such an evolution process results in a prominent drop of the gas pressure inside bubbles and therefore prevents nanoscale gas bubble defects from the complete dissolution into resists. This work identifies the critical mechanisms responsible for the formation of detrimental nanoscale bubble defects and provides important insights for the ultimate elimination of such defects 

   more » « less