Non-Uniform Circumferential Expansion of Cylindrical Li-Ion Cells—The Potato Effect

This paper presents the non-uniform change in cell thickness of cylindrical Lithium (Li)-ion cells due to the change of State of Charge (SoC). Using optical measurement methods, with the aid of a laser light band micrometer, the expansion and contraction are determined over a complete charge and discharge cycle. The cell is rotated around its own axis by an angle of α=10° in each step, so that the different positions can be compared with each other over the circumference. The experimental data show that, contrary to the assumption based on the physical properties of electrode growth due to lithium intercalation in the graphite, the cell does not expand uniformly. Depending on the position and orientation of the cell coil, there are different zones of expansion and contraction. In order to confirm the non-uniform expansion around the circumference of the cell in 3D, X-ray computed tomography (CT) scans of the cells are performed at low and at high SoC. Comparison of the high resolution 3D reconstructed volumes clearly visualizes a sinusoidal pattern for non-uniform expansion. From the 3D volume, it can be confirmed that the thickness variation does not vary significantly over the height of the battery cell due to the observed mechanisms. However, a slight decrease in the volume change towards the poles of the battery cells due to the higher stiffness can be monitored.

Effects of Refractive Accommodation on Subfoveal Choroidal Thickness in Silicone Oil-Filled Eyes

PURPOSE: To investigate the effects of refractive accommodation on subfoveal choroidal thickness (SFCT) in silicone oil (SO)-filled eyes.METHODS: This retrospective, self-comparative study was conducted on 40 patients with unilateral macula-on rhegmatogenous retinal detachment, who underwent vitrectomy and SO tamponade. The SFCT of SO-filled eyes and the fellow control eyes were measured using optical coherence tomography at their one-month visit after surgery. The patients wore soft contact positive lenses for 24 hours in the SO-filled eyes, to correct their refractive error. SFCT and choroidal vascularity index (CVI) were measured before and after wearing the contact lenses. Mean SFCT was compared between SO-filled eyes and the fellow control eyes, and SFCT and CVI were compared before and after refractive error correction in the SO-filled eyes.RESULTS: Mean SFCT of SO-filled eyes (221.52±38.41 um) was less than that of the fellow eyes (273.41±31.30 um) (P<0.001). After refractive error correction, the mean SFCT increased to 269.28±36.90 um(P <0.001). However, CVI decreased from 57.01±2.41 to 55.39±2.39 (P<0.05).CONCLUSION: SFCT reduction in SO-filled eyes was primarily due to the hyperopia status. The non-uniform change in CVI suggests that changes in CT are mainly attributed to a greater expansion of the stromal area instead of the choroidal vascular area.

Interference Torque of a Gas-Dynamic Bearing Gyroscope Subject to a Uniform Change of the Specific Force and the Carrier Angular Velocity

The work is devoted to an analysis of interference torque of a gas-dynamic bearing gyroscope, while a condition with uniformly changed specific force and carrier angular velocity are taken into account. A five-degrees-of-freedom (5-DOF) model is established considering the translation and tilt of the rotor, which solves dynamic rotor equations and the Reynolds equation simultaneously. The model makes it possible to obtain the rotor trajectory under time-transient specific force and carrier angular velocity. The interference torque of the gyroscope is analyzed based on the rotor trajectory. Results indicate that the gas-dynamic bearings show a significant hysteresis effect with a perturbation of bearing force or bearing moment, which indicates the necessity of transient research. Interference torque is large when the carrier angular velocity starts to change or stops to change, and when the specific force stops to change. When the specific force change rate is less than 8.4 km/s3 with no change of the carrier angular velocity, the condition could be simplified as a steady state, which is consistent with the previous study.

Application Research of NC Machining of Circular-Arc Aligned Gear

numerical control system is used to control the gear hob and gear blank in autorotation and linkage generative movement, to realize the machining of teeth shape and teeth dividing; and at the same time it controls the vertical displacement of the gear hob and the horizontal displacement of gear blank, to make a circular arc track whose radius is the sum of gear blank’s radius and gear hob’s radius, thus realizing the NC machining of circular-arc aligned gear. Before and after the machining of teeth form, transition arc is used to finish the trimming and thinning of the teeth thickness at the teeth end; on the prerequisite of machining the circular-arc aligned gear, this method successfully solves the puzzle of gear chamfering, and discharges all gear burr into the lower end of the teeth. The advantage of this machining method lies in that when the hob cuts deeper, as the both side-blades are cutting the work-piece at the same time, the thinning on both sides are quite symmetrical, and the fine symmetry remains during the uniform change of the teeth thickness. So, the machining precision of the parts is prior to the requirements in the drawing, and this method yields good effect, which broadens the application of NC technology.