An Experimental Study On Cryogenic Spray Quenching of a Circular Metal Disk I. Effects of Mass Flux, Spray Fluid Inlet Subcooling, and Gravity

This is the first part of a two-paper series that reports the design, experimentation, and results of a spray quenching experiment of a circular metal disk in terrestrial gravity conditions. The objective of this experiment is to provide experimental data and corresponding analysis on the heat transfer characteristics and chilldown performance of the cryogenic spray quenching process. In this paper, the presented continuous-flow spray quenching results include the spray-cone angle visualization, spray cooling heat transfer characteristics represented by chilldown curves and boiling curves, gravity effects, and Leidenfrost rewet point temperatures. Additionally, detailed discussion is given on the film boiling heat transfer and rewet temperature in terms of various contributing factors such as gravitational acceleration, spray mass flux, and radial position on the plate. Based on experimental data, empirical correlations for film boiling heat transfer coefficient and rewet temperatures are provided. We expect that, the current terrestrial study would offer invaluable information for the design of a robust in-space cryogenic propellant storage tank spray chilldown system.

Modeling of the nitrous oxide synthesis in a microchannel reactor: the effect of parameters on the temperature regimes and output

The study deals with the synthesis of nitrous oxide via selective oxidation of ammonia in a microreactor (MCR), which is a metal disk with cylindrical channels filled with the manganese-bismuth oxide catalyst. The proposed 3D mathematical model of MCR takes into account axial and radial heat and mass transfer, catalytic reactions and related changes of the reaction mixture volume, heat exchange between the disk and channels, and thermal conductivity of the disk. Parameters providing the maximum output of nitrous oxide were determined with allowance for restrictions on the temperature in MCR channels. The highest efficiency of the nitrous oxide synthesis is achieved at a temperature of the outer edge of reactor 370 °С and an inlet concentration of ammonia 20 vol.%. The output per unit catalyst volume in MCR is approximately 1.5 times higher as compared to a tubular reactor; the maximum temperature corresponds to the optimal one, which provides the best selectivity of the process with respect to nitrous oxide.

Underwater metastructure with broadband sound absorption capability in low-frequency range above 20 Hz

We present an underwater metastructure with excellent sound absorption effect below 50 Hz. The periodic metastructure unit consists of a conical cavity, rubber matrix, and two metal disks. FEM results show that, in the range of 20–300 Hz, the proposed metastructure demonstrates the excellent sound absorption within 279 Hz bandwidth when the reference absorption coefficient is considered to be 0.5. Displacement vibration diagrams illustrate the addition of two layers of metal disks break the propagation law of acoustic wave in rubber matrix. An anti-phase motion of the rubber matrix emerges due to the presence of the metal disks, then consumes the energy of incident acoustic waves. The geometric parameters of lattice constant [Formula: see text], the thickness [Formula: see text], and the height [Formula: see text] of the upper metal disk are positively correlated with the sound absorption coefficient, while the upper radius [Formula: see text] and the height [Formula: see text] of the conical cavity are negatively correlated with the sound absorption coefficient. The novel design presented in this study could have the potential applications in the realization of an acoustic underwater anechoic layer.

Opelt’s Siren and the Technologies of Musical Hearing

Friedrich Wilhelm Opelt (1794–1863) proposed a revolutionary music theory based on the recursive features of human hearing. Opelt based his theory on a recent invention, Charles Cagniard de la Tour’s mechanical siren (1819), which he expanded and improved. Cagniard’s model consists of a metal disk with holes in regular intervals that, when set in rotation and with air blown through them, produce a series of air puffs. Once their pulsation increases above 20Hz, this pulse is heard as a continuous, rising pitch. Opelt employed this device to test the properties of hearing against the parameters of music: he noted that more complex patterns of holes translate into intervals, chords, and harmonies and showed that every pitch event can be translated into a corresponding rhythmic event. Pitch and rhythm may be different perceptual parameters, but physically, they are both temporal events, which merely inhabit different dimensions of the time axis.

Calculating loads and life-time reduction of wind turbine gearbox and generator bearings due to shaft misalignment

During the last two decades, wind turbine industries have faced high failure rates, downtimes and costly repairs. Gearbox and generator have contributed to this, especially, because their high speed shaft bearings have often failed. In this article, an analytical method is proposed to calculate the reaction loads of flexible connecting couplings installed between wind turbine gearbox and generator. Raction loads are determined from joint kinematics and metal disk pack deformations as well as axial and angular shaft misalignment. The calculations are executed for both flexible connecting couplings and a universal joint shaft and applied to the gearbox high speed shaft. The performance of flexible connecting couplings and universal joint shaft is compared with respect to the bearing loads and life-time of the gearbox high speed shaft. It is shown that the early, unplanned bearing failures of gearbox and generator high speed shaft can often be attributed to the flexible connecting couplings installed between gearbox and generator.

Strain pattern of each ligamentous band of the superficial deltoid ligament: a cadaver study

BackgroundThere are few reports on the detailed biomechanics of the deltoid ligament, and no studies have measured the biomechanics of each ligamentous band because of the difficulty in inserting sensors into the narrow ligaments. This study aimed to measure the strain pattern of the deltoid ligament bands directly using a Miniaturization Ligament Performance Probe (MLPP) system.MethodsThe MLPP was sutured into the ligamentous bands of the deltoid ligament in 6 fresh-frozen lower extremity cadaveric specimens. The strain was measured using a round metal disk (clock) fixed on the plantar aspect of the foot. The ankle was manually moved from 15° dorsiflexion to 30° plantar flexion, and a 1.2-N-m force was applied to the ankle and subtalar joint complex. Then the clock was rotated every 30° to measure the strain of each ligamentous band at each endpoint.ResultsThe tibionavicular ligament (TNL) began to tense at 10° plantar flexion, and the tension becomes stronger as the angle increased; the TNL worked most effectively in plantar flex-abduction. The tibiospring ligament (TSL) began to tense gradually at 15° plantar flexion, and the tension became stronger as the angle increased. The TSL worked most effectively in abduction. The tibiocalcaneal ligament (TCL) began to tense gradually at 0° dorsiflexion, and the tension became stronger as the angle increased. The TCL worked most effectively in pronation (dorsiflexion-abduction). The superficial posterior tibiotalar ligament (SPTTL) began to tense gradually at 0° dorsiflexion, and the tension became stronger as the angle increased, with the SPTTL working most effectively in dorsiflexion.ConclusionOur results show the biomechanical function of the superficial deltoid ligament and may contribute to determining which ligament is damaged during assessment in the clinical setting.

Darkfield colors from multi-periodic arrays of gap plasmon resonators

We present results on colors of metal disk arrays viewed under a darkfield microscope and show that the darkfield colors can be manipulated independently of the brightfield colors. We investigate the appearance of colors as disks are clustered to form a new array with double the pitch and a basis of four disks. These structures of aluminum disks on aluminum oxide on aluminum have resonances in the visible spectrum, so by arranging them in small tight clusters, a coupled plasmon resonant mode is produced at shorter wavelengths. This feature causes a reflectance minimum and leads to an increase in the gamut of darkfield colors produced. These colors are tuned by changing the size of the disk and the inter-disk gap within the clusters. Interestingly, the intensities of the reflectance peaks also demonstrate good agreement with the Fourier series coefficients for square waves. Polarization-tunable colors are also demonstrated by designing rectangular arrays that have dissimilar periods along the two orthogonal axes of the array, and a four-level security tag is fabricated that encodes images for viewing under brightfield, darkfield (both x and y polarization), and infrared illumination.

Strain pattern of each ligamentous band of the superficial deltoid ligament

Background There are few reports in terms of detailed biomechanics of the deltoid ligament, and no reports have measured the biomechanics of each ligamentous band, due to the difficulty in inserting sensors into the narrow ligaments. This study aims to measure the strain pattern of the deltoid ligament bands using a miniaturization ligament performance probe (MLPP) system. Methods The MLPP was sutured into the ligamentous bands of the deltoid ligament in 6 fresh-frozen lower extremity cadaveric specimens. The strain was measured using a round metal disk (clock) fixed on the plantar aspect of the foot. The ankle was manually moved from 15° of dorsiflexion to 30° plantar flexion, and a 1.2-N-m force was applied to the ankle and subtalar joint complex. The clock was then rotated every 30° to measure the strain of each ligamentous band at each endpoint. Results The tibionavicular ligament (TNL) begins to tense at 10° plantar flexion and the tension becomes stronger as the angle increases; the TNL works most effectively in plantar flex-abduction. The tibiospring ligament (TSL) begins to tense gradually at 15° plantar flexion and the tension becomes stronger as the angle increases. The TSL works most effectively in the abduction. The tibiocalcaneal ligament (TCL) begins to tense gradually at 0° dorsiflexion, and the tension becomes stronger as the angle increases. The TCL works most effectively in pronation (dorsiflexion-abduction). The superficial posterior tibiotalar ligament (SPTTL) begins to tense gradually at 0° dorsiflexion, and the tension becomes stronger as the angle increases, with the SPTTL working most effectively in dorsiflexion. Conclusion Our results provide a better understanding of the biomechanical function of the superficial deltoid ligament and could help in improving repair and reconstruction procedures.