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1. A Whisker-inspired Fin Sensor for Multi-directional Airflow Sensing

   https://doi.org/10.1109/IROS45743.2020.9341723  

   Kim, Suhan; Kubicek, Regan; Paris, Aleix; Tagliabue, Andrea; How, Jonathan P.; Bergbreiter, Sarah (October 2020, 2020 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS))

   null (Ed.)

   This work presents the design, fabrication, and characterization of an airflow sensor inspired by the whiskers of animals. The body of the whisker was replaced with a fin structure in order to increase the air resistance. The fin was suspended by a micro-fabricated spring system at the bottom. A permanent magnet was attached beneath the spring, and the motion of fin was captured by a readily accessible and low cost 3D magnetic sensor located below the magnet. The sensor system was modeled in terms of the dimension parameters of fin and the spring stiffness, which were optimized to improve the performance of the sensor. The system response was then characterized using a commercial wind tunnel and the results were used for sensor calibration. The sensor was integrated into a micro aerial vehicle (MAV) and demonstrated the capability of capturing the velocity of the MAV by sensing the relative airflow during flight. 

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2. Stiffness Perception using Transcutaneous Electrical Stimulation during Active and Passive Prosthetic Control

   https://doi.org/10.1109/EMBC44109.2020.9176078  

   Vargas, Luis; Huang, Helen; Zhu, Yong; Hu, Xiaogang (July 2020, International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC))

   null (Ed.)

   Haptic feedback allows an individual to identify various object properties. In this preliminary study, we determined the performance of stiffness recognition using transcutaneous nerve stimulation when a prosthetic hand was moved passively or was controlled actively by the subjects. Using a 2×8 electrode grid placed along the subject's upper arm, electrical stimulation was delivered to evoke somatotopic sensation along their index finger. Stimulation intensity, i.e. sensation strength, was modulated using the fingertip forces from a sensorized prosthetic hand. Object stiffness was encoded based on the rate of change of the evoked sensation as the prosthesis grasped one of three objects of different stiffness levels. During active control, sensation was modulated in real time as recorded forces were converted to stimulation amplitudes. During passive control, prerecorded force traces were randomly selected from a pool. Our results showed that the accuracy of object stiffness recognition was similar in both active and passive conditions. A slightly lower accuracy was observed during active control in one subject, which indicated that the sensorimotor integration processes could affect haptic perception for some users. 

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3. 7.5 kV, 6.2 GW cm−2 NiO/β-Ga2O3 vertical rectifiers with on–off ratio greater than 1013

   https://doi.org/10.1116/6.0002580  

   Li, Jian-Sian; Chiang, Chao-Ching; Xia, Xinyi; Wan, Hsiao-Hsuan; Ren, Fan; Pearton, S. J. (May 2023, Journal of Vacuum Science & Technology A)

   Vertical geometry NiO/β n-Ga2O/n+ Ga2O3 heterojunction rectifiers with contact sizes from 50 to 200 μm diameter showed breakdown voltages (VB) up to 7.5 kV for drift region carrier concentration of 8 × 1015 cm−3. This exceeds the unipolar 1D limit for SiC and was achieved without substrate thinning or annealing of the epi layer structure. The power figure-of-merit, VB2/RON, was 6.2 GW cm−2, where RON is the on-state resistance (9.3–14.7 mΩ cm2). The average electric field strength was 7.56 MV/cm, approaching the maximum for β-Ga2O3. The on–off ratio switching from 5 to 0 V was 2 × 1013, while it was 3 × 1010–2 × 1011 switching to 100 V. The turn-on voltage was in the range 1.9–2.1 V for the different contact diameters, while the reverse current density was in the range 2 × 10−8–2 × 10−9 A cm−2 at −100 V. The reverse recovery time was 21 ns, while the forward current density was >100 A/cm2 at 5 V. 

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4. Effects of Needle Lift and Fuel Type on Cavitation Formation and Heat Transfer Inside Diesel Fuel Injector Nozzle

   Zeidi, Javad SM; Dulikravich, George S; Reddy, Sohail R; Darvish, Shadi (May 2017, International Symposium on Advances in Computational Heat Transfer, paper CHT-17-102, Naples, Italy, May 28-June 1, 2017)

   In the present study, the flow inside a real size Diesel fuel injector nozzle was modeled and analyzed under different boundary conditions using ANSYS-Fluent software. A validation was performed by comparing our numerical results with previous experimental data for a rectangular shape nozzle. Schnerr-Sauer cavitation model, which was selected for this study, was also validated. Two-equation k-ε turbulence model was selected since it had good agreement with experimental data. To reduce the computing time, due to symmetry of this nozzle, only one-sixth of this nozzle was modeled. Our present six-hole Diesel injector nozzle was modeled with different needle lifts including 30 μm, 100 μm and 250 μm. Effects of different needle lifts on mass flow rate, discharge coefficient and length of cavitation were evaluated comprehensively. Three different fuels including one Diesel fuel and two bio-Diesel fuels were also included in these numerical simulations. Behavior of these fuels was investigated for different needle lifts and pressure differences. For comparing the results, discharge coefficient, mass flow rate and length of cavitation region were compared under different boundary conditions and for several fuel types. The extreme temperature spike at the center of an imploding cavitation bubble was also analyzed as a function of time and initial bubble size. 

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5. Optimization of batch and packed-bed column Cr( vi ) adsorption of an amine-rich chitosan/polyethyleneimine composite: application in electroplating wastewater treatment

   https://doi.org/10.1039/d4ew00123k  

   Ansari, Ali; Silva_Jacovone, Raynara Maria; Nadres, Enrico Tapire; Đỗ, Minh; Rodrigues, Debora Frigi (June 2024, Environmental Science: Water Research & Technology)

   Toxic oxyanions of Cr(VI) can be potentially removed by adsorbents with positively charged surfaces. In this study, we synthesized a stable and insoluble amine-rich polymer composite (CS–PEI–GLA) by crosslinking polyethyleneimine (PEI), a soluble amine-rich synthetic polymer, and chitosan (CS) with glutaraldehyde (GLA). The positively charged amine groups were the main adsorption sites. The batch investigation demonstrated that the adsorbent was able to remove ≥90% of chromium at pH ranging from 2 to 8. Due to deprotonation of the amine groups, chromium removal decreased at higher pH values. The adsorption was fast and reached equilibrium after 45 min. The maximum adsorption capacity was 500 mg g−1 according to the Langmuir isotherm and did not decrease in the presence of monovalent anions. In the column study, the adsorption capacity was the highest when the flow rate was the lowest (5 mL min−1), influent concentration was medium (225 mg L−1), and the bed height was the shortest (3.5 cm). NaOH was the best recovery reagent with recovery of 67% in batch and 31% in the column. The CS–PEI–GLA composite was able to remove 97.1 ± 0.1% chromium in batch and treat 750 mL of electroplating wastewater with a 3.5 cm packed-bed column. 

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