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1

Partitioning of solar radiation in Arctic sea ice during melt season

Lu P., Cheng B., Leppäranta M., Li Z.

Oceanologia

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2018

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No. 60 (4)

464--477

EN

The partitioning of solar radiation in the Arctic sea ice during the melt season is investigated using a radiative transfer model containing three layers of melt pond, underlying sea ice, and ocean beneath ice. The wavelength distribution of the spectral solar irradiance clearly narrowed with increasing depth into ice, from 350-900 nm at the pond surface to 400-600 nm in the ocean beneath. In contrast, the net spectral irradiance is quite uniform. The absorbed solar energy is sensitive to both pond depth (Hp) and the underlying ice thickness (Hi). The solar energy absorbed by the melt pond (Ψp) is proportional only to Hp. However, the solar energy absorbed by the underlying ice (Ψi) is more complicated due to the counteracting effects arising from the pond and ice to the energy absorption. In September, Ψp decreased by 10% from its August value, which is attributed to more components in the shortwave band (<530 nm) of the incident solar radiation in September relative to August. The absorption coefficient of the sea ice only enhances the absorbed energy in ice, while an increase in the ice scattering coefficient only enhances the absorbed energy in the melt pond, although the resulted changes in Ψp and Ψi are smaller than that in the albedo and transmittance. The energy absorption rate with depth depends strongly on the incident irradiance and ice scattering, but only weakly on pond depth. Our results are comparable to previous field measurements and numerical simulations. We conclude that the incident solar energy was largely absorbed by the melt pond rather than by the underlying sea ice.

2

Free boundary of journal bearing with spiral groove in HDD

Lu P., Xiao D., Zhou G.

International Journal of Applied Mechanics and Engineering

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2002

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Vol. 7, no 3

859-874

EN

In a self-sealing journal bearing with spiral grooves, the bearing gap is not actually fully filled with lubricant. Specially at the seal interfaces, the so-called free boundary between the lubricant and ambient air is formed. A free boundary does not only influence the load-capacity and stability of a bearing, more importantly, it affects the bearing dynamic sealing capability. In this paper, an analytical model and numerical procedure is developed to investigate the free boundary of a journal bearing with spiral grooves. The simulation results are discussed on how the bearing parameters may affect free boundary and its impact on the bearing leakage. The approach establishes a base for precise calculation of performance parameters and optimization design of a journal bearing with spiral grooves in HDD.

3

The golfball model and the purpose of drumlin formation

Smalley J., Lu P., Jefferson F.

Studia Quaternaria

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2000

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Vol. 17

29-33

EN

The purpose of drumlin formation is to facilitate glacier flow. Drumlins form in a deforming layer between ice and ground, they produce a pimpled ground surface which causes less drag in the flowing system, after the fashion of the Prandtl effect which reduces boundary layer detachment (as in the flying golf ball). This pimpled surface has self-organising properties and this causes the development of a low drag situation. The drumlin field is the critical phenomenon; the formation of individual drumlins is a small part of the overall effect.