Search

Your search keyword '"Hong, Ki-Nam"' showing total 40 results
Start Over Author "Hong, Ki-Nam"
40 results on '"Hong, Ki-Nam"'

20. Stability Formula for Rakuna-IV Armoring Rubble-Mound Breakwater

Author

Kyung-Duck Suh, Hong Ki Nam, Tae Hoon Lee, and Hiroshi Matsushita

Subjects
business.industry, Iribarren number, Breakwater, Stability coefficient, Rubble, engineering, Geotechnical engineering, Function (mathematics), engineering.material, Significant wave height, business, Stability (probability), Physics::Geophysics
Abstract

In this study, a total of 51 cases of hydraulic model tests has been conducted for various wave conditions and slope angles of breakwater to develop a stability formula for Rakuna-IV armoring a rubble-mound breakwater. The stability number of the formula is expressed as a function of relative damage, number of waves, structural slope, and surf similarity parameter. The stability formula is derived separately for plunging and surging waves, the greater of which is used. The transitional surf similarity parameter from plunging waves to surging waves is also presented. Lastly, to explain the stability of Rakuna-IV to the engineers who are familiar with the stability coefficient in the Hudson formula, the required weight of Rakuna-IV is calculated for varying significant wave height for typical plunging and surging wave conditions, which is then compared with those of the Hudson formula using several different stability coefficients.

Published
2013

40. Effect of the Hammett substituent constant of para -substituted benzoic acid on the perovskite/SnO 2 interface passivation in perovskite solar cells.

Author

Hong KN, Lee SU, Zhang C, Cho SH, and Park NG

Abstract

It is critical to design bifunctional passivation molecules to simultaneously passivate the charge transport layer and perovskite layer at the charge transport layer/perovskite interface in perovskite solar cells (PSCs). In this study, we investigate the effect of para -substituted benzoic acid with different Hammett constants ( σ ) on the photovoltaic performance of PSCs. Two passivation molecules 4-aminomethylbenzoic acid (4-AMBA) and 4-sulfamoylbenzoic acid (4-SABA) are used to passivate the SnO 2 surface with carboxylic acid and the perovskite with para -substituent electron-donating -CH 2 NH 2 ( σ = ca. -0.02) and electron-withdrawing -SO 2 NH 2 ( σ = ca. +0.60). Compared with non-passivated PSC, the passivation improves the power conversion efficiency (PCE) mainly due to the increased open-circuit voltage ( V OC ) and fill factor (FF), where the -SO 2 NH 2 substituent is better in improving the photovoltaic performance than the -CH 2 NH 2 one. The trap density is more reduced and the charge extraction ability is more improved by 4-SABA than by 4-AMBA, which indicates that the weak electron-withdrawing nature of a para -substituent such as -SO 2 NH 2 is better for the passivation of the bottom perovskite than a weak electron-donating -CH 2 NH 2 substituent. Consequently, the passivation with 4-SABA enhances the PCE from 22.27% to 23.64%, along with improved long-term stability. This work highlights for the first time the role of the Hammett constant in the surface passivation of PSCs.

Published
2024
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results