Although the effects of kinetics on crystal growth are well understood, the role of substrate curvature is not yet established. We studied rigid, two-dimensional colloidal crystals growing on ...spherical droplets to understand how the elastic stress induced by Gaussian curvature affects the growth pathway. In contrast to crystals grown on flat surfaces or compliant crystals on droplets, these crystals formed branched, ribbon-like domains with large voids and no topological defects. We show that this morphology minimizes the curvature-induced elastic energy. Our results illustrate the effects of curvature on the ubiquitous process of crystallization, with practical implications for nanoscale disorder-order transitions on curved manifolds, including the assembly of viral capsids, phase separation on vesicles, and crystallization of tetrahedra in three dimensions.
Supercapacitor fibers, with short charging times, long cycle lifespans, and high power densities, hold promise for powering flexible fabric‐based electronics. To date, however, only short lengths of ...functioning fiber supercapacitors have been produced. The primary goal of this study is to introduce a supercapacitor fiber that addresses the remaining challenges of scalability, flexibility, cladding impermeability, and performance at length. This is achieved through a top‐down fabrication method in which a macroscale preform is thermally drawn into a fully functional energy‐storage fiber. The preform consists of five components: thermally reversible porous electrode and electrolyte gels; conductive polymer and copper microwire current collectors; and an encapsulating hermetic cladding. This process produces 100 m of continuous functional supercapacitor fiber, orders of magnitude longer than any previously reported. In addition to flexibility (5 mm radius of curvature), moisture resistance (100 washing cycles), and strength (68 MPa), these fibers have an energy density of 306 μWh cm−2 at 3.0 V and ≈100% capacitance retention over 13 000 cycles at 1.6 V. To demonstrate the utility of this fiber, it is machine‐woven and used as filament for 3D printing.
A flow‐based preform‐to‐fiber (top‐down) thermal drawing process is used in which a preform of macroscale dimensions, assembled with all the five component materials, is thermally drawn into 100 m lengths of fully functional supercapacitor fiber. The cell architecture is designed to address the mechanical, environmental, electrical, and storage requirements of a textile and 3D printed energy‐storage device.
Stability of a bulk-optical resonator is a very important factor in the cavity analysis. The stability of a resonator depends on the properties and arrangement of the optical components, basically ...the curvature of reflecting surfaces, other focusing effects, and the distances between the components. When a parameter such as cavity length or the radius of curvature of the focusing element in the resonator is varied, the cavity stability also changes. This paper presents a concise and very simplified design and modeling of a ‘L’ shaped cavity, with reflecting and refracting elements along with two curved mirrors (cavity mirrors) using ABCD matrix and also the importance of an optical element used in L-cavity. The stability is calculated from the ABCD matrix and analyzed using cavity parameters like cavity length and radius of curvature. The stability of the L-cavity is analyzed by varying the length of the cavity from 100 mm to 1500 mm. The L-cavity is stable up to 1500 mm for mirror as intra cavity element and is stable beyond 1500 mm also for TIR (Total internal reflection) prism as intra cavity element. Similarly, the radius of curvatures of mirror and prism also varied from 100 mm to 2500 mm. The L-cavity is stable from 300 mm in mirror case and further also. The L-cavity is stable from 100 mm in TIR prism case and further also. The power distribution of laser beam is also simulated and analyzed for both mirror and TIR prism L-cavity using ZEMAX tool in non sequential mode. From the stability point and other properties of an optical element used in the L-cavity, the importance of the mirror and TIR prism is also studied and also which optical element is preferred for further ring cavity applications.
•Impact of cavity length and radius of curvature on state of the stability analyzed.•L-cavity is stable up to 1500 mm for mirror and stable beyond 1500 mm for prism case.•For the mirror the power distribution is 66 W/cm2 and for the prism 97 W/cm2.•The backscattering in the prism is lower than that of the mirrors.•refracting element is the best optical intra cavity element for cavity applications.
•Detailed local thermal-hydraulic performance of the simplified PCHE with zigzag channels is obtained.•Fully-developed flow condition is not observed in the PCHE with zigzag channels.•The global heat ...transfer coefficient is considerably different from the local heat transfer coefficient.•Thermal boundary conditions play an important role in the PCHE heat transfer.•Effects of thermophysical properties and geometrical parameters on PCHE’s performance are analyzed.
Printed circuit heat exchanger (PCHE) is one of the leading candidates to be employed in advanced nuclear reactors and next generation concentrated solar power applications due to its compactness and capability for high-temperature, high-pressure applications with high effectiveness. In the current study, thermal-hydraulic performance of a zigzag-channel PCHE with high-pressure, high-temperature helium on both the hot and cold sides was simulated using a computational fluid dynamics (CFD) software package STAR-CCM + . Comparisons between the experimental data and CFD simulation results showed good agreement with some discrepancies in the pressure drop and heat transfer results. Local thermal-hydraulic performance analyses indicated that a fully-developed flow condition was not observed in the PCHE, mainly due to the nature of the zigzag channels, leading to periodic flow disturbance at each of the zigzag bends. It was also found that the local and global heat transfer coefficients were considerably different in the PCHE. Furthermore, thermal boundary conditions showed that the fluid temperatures and heat fluxes were not uniform along the azimuthal direction of a cross section of the flow channel and that the helium temperature distribution for each segment along the flow direction presented a wavy profile. However, the distribution of the helium bulk temperature along the flow direction was approximately linear. For the heat flux distributions, although they were significantly different at different segments, the trend of the heat flux for each segment along the fluid flow direction was similar. Finally, effects of several parameters on the thermal-hydraulic performance of the PCHE were investigated, including the fluid and solid thermophysical properties, radius of curvature at zigzag bends, channel configuration, channel length pitch in the flow direction, and zigzag pitch angle. No considerable enhancement in the Nusselt numbers was observed when the zigzag pitch angles were greater than 30°.
Accommodative intraocular lens concepts Eppig, Timo
Acta ophthalmologica (Oxford, England),
December 2019, 2019-12-00, 20191201, Letnik:
97, Številka:
S263
Journal Article
Recenzirano
The restoration of accommodation still remains the biggest challenge of cataract surgery. The desire for real pseudophakic accommodation remains unchanged although modern multifocal lenses provide ...acceptable presbyopic correction and visual quality. Numerous concepts for accommodative intraocular lenses have been presented during the last decades but none of these were as successful as multifocal lenses are today. These concepts can be divided into three principles: Optic shift moves a single lens or a set of lenses along the optical axis such as the, for example, the 1CU (HumanOptics), the Crystalens (Bausch & Lomb) and the Synchrony (Visiogen/AMO). Varying radius of curvature changes refraction oft he lens such as, for example, the Juvene (LensGen). Replacement of the or refilling of the capular bag remains an interesting option but refilling has not reached the stage of human clinical trials. We will present an overview on the various concepts for the restoration of accommodation in the pseudophakic eye and the current clinical status.
•A spiral with small radius of curvature has better mixing performance.•Stronger chaotic advection is induced by small radius of curvature.•Vortices degradation arising from counter-rotating Dean ...vortices suppresses mixing.•Vortices periodically vary along the flow path in the single spiral structure.•Vortices advection intensity proposed can reliably characterize chaotic advection.
With significant centrifugal effects and Dean vortices, the spiral microchannels are being widely used in microfluidic systems, especially for high-efficiency mixing. However, the spirals are with various shapes and their radii continuously vary along the spiral, which causes the flow fields and mixing process complicated. This research focused on the flow behaviors and mixing performance of spiral micromixers with various spiral structures. Five classical spirals of Archimedean, Logarithmic, Hyperbolic, Golden and Fibonacci spirals, and two structures of centrosymmetric spiral structure and single spiral structure were investigated. Numerical simulation and experimental validation were conducted with Re from 0.1 to 100. The results showed that the Archimedean spiral presented the best mixing performance among the five spirals, since its radius of curvature kept a small value in the whole flow path which brought about stronger Dean vortices. Moreover, it was found that Dean vortices was inapplicable to characterize chaotic advection in the centrosymmetric spiral structure due to vortices degradation. Vortices degradation resulted from the counter-rotating Dean vortices, which suppressed the chaotic advection and the mixing process. The results also revealed that vortices varied periodically along the flow path in single spiral structure. Increasing the Reynolds number accelerated the periodical variation of vortices, and therefore mixing developed more rapidly. Moreover, a novel parameter named vortices advection intensity (Vai) was proposed to characterize chaotic advection. The calculated results of Vai agreed well with the results of mixing performance under the condition of chaotic advection dominated mixing. The parameter Vai could reliably characterize chaotic advection.
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Abstract In this paper, based on the accumulation pattern of particles flowing through the bend, the Dunes are designed to be placed in curves with different radii of curvature in a ...horizontal-vertical pneumatic conveying system, and the movement characteristics of the particles entering the vertical pipeline due to with Dunes are analyzed based on CFD-DEM. Compared to the case of No Dune, the Gas-solid two-phase velocities with Dune are almost evenly distributed in the pipe and are larger than the corresponding case of No Dune. At the same time, the particle axial velocities with Dunes are larger than the case without Dunes, the number of collisions of particles in vertical tubes is reduced due to Dunes, and the particles diverge sufficiently throughout the vertical tube from the particle flow patterns. The results show the effect of Dunes can increase the velocity of particles and reduce the impact of particles on the pipe wall, it is conducive to the transport of particles. Meanwhile, The experiment known as particle image velocimetry (PIV) verifies the accuracy of the numerical simulation results.
Flexible thermoresponsive polymeric microjets are formed by the self‐folding of polymeric layers containing a thin Pt film used as catalyst for self‐propulsion in solutions containing hydrogen ...peroxide. The flexible microjets can reversibly fold and unfold in an accurate manner by applying changes in temperature to the solution in which they are immersed. This effect allows microjets to rapidly start and stop multiple times by controlling the radius of curvature of the microjet. This work opens many possibilities in the field of artificial nanodevices, for fundamental studies on self‐propulsion at the microscale, and also for biorelated applications.
Micro jet boating: Flexible thermoresponsive polymer microjets can be fabricated. These self‐propelled microjets can reversibly fold and unfold in an accurate manner by applying changes in temperature to the solution in which they are immersed. This effect allows them to start and stop multiple times by controlling the radius of curvature of the microtube.
The economic and engineering importance of additive drag reduction (DR) has provided motivation and wealth of data on the phenomena in straight conduit flows. Study into the effect of drag-reducing ...additives (DRAs) on complex and under-developed flows in and after bends is very limited. Novel results of DR in and around U-bends is presented in this work. Three polymer types were tested and the radii of curvature (R) of the U-bends were 100 and 200 mm with pipe diameter of 19 mm . DR increased with polymer concentration and flow rate up to certain thresholds. DR differed among the different sections considered with the highest value recorded for developed flows upstream of the bend and the least values recorded in the bend. DR increased with flow development after the bend and increased with polymer molecular weight before and after the bend. The effect of bend curvature ratio on DR was predominant after the U-bend. For R = 100 mm, the highest DR recorded upstream of bend, in the bend, immediately after and further downstream of the bend were 57, 31, 36 and 33% respectively.
Ultrastable sensing characteristics of the ionic chemiresistor skin (ICS) that is designed by using an intrinsically stretchable thermoplastic polyurethane electrolyte as a volatile organic compound ...(VOC) sensing channel are described. The hierarchically assembled polymer electrolyte film is observed to be very uniform, transparent, and intrinsically stretchable. Systematic experimental and theoretical studies also reveal that artificial ions are evenly distributed in polyurethane matrix without microscale phase separation, which is essential for implementing high reliability of the ICS devices. The ICS displays highly sensitive and stable sensing of representative VOCs (including toluene, hexane, propanal, ethanol, and acetone) that are found in the exhaled breath of lung cancer patients. In particular, the sensor is found to be fully operational even after being subjected to long‐term storage or harsh environmental conditions (relative humidity of 85% or temperature of 100 °C) or severe mechanical deformation (bending to a radius of curvature of 1 mm, or stretching strain of 100%), which can be an effective method to realize a human‐adaptive and skin‐attachable biosensor platform for daily use and early diagnosis.
An ultrastable performance of an ionic chemiresistor skin (ICS) sensor is created using intrinsically stretchable solid‐state polymer electrolyte. The ICS sensor displays highly sensitive and stable sensing of volatile organic compound gases even after being subjected to long‐term storage, harsh environmental conditions, or severe mechanical deformation, indicating its potential as a human‐adaptive, skin‐attachable biosensor platform.
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