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Microscale Geomembrane-Granular Material Interactions
J. David Frost,Duhwan Kim,이석원 대한토목학회 2012 KSCE JOURNAL OF CIVIL ENGINEERING Vol.16 No.1
By quantifying the evolution of void ratio in granular soils of different angularity under different normal stress levels adjacent to geomembranes of varying roughness at different stages of shearing, the effect of geomembrane surface roughness on the interface shear mechanisms between granular materials and geomembranes was investigated. The extent of the shear zone thickness at the interfaces between combinations of round/angular particles and smooth/textured geomembrane surfaces were evaluated. For smooth geomembranes, the interface shear strength is developed by sliding and plowing of sand particles, while for textured geomembranes,the strength results from the interlocking and dilation of sand particles. Study on the effect of particle angularity showed that more angular sand particles resulted in larger plowing effects with smooth geomembranes which in turn yielded higher residual friction angles than with rounded to sub-rounded sand. Higher normal stress produced larger plowing effects for a given sand sheared against a smooth geomembrane and reduced the amount of dilation adjacent to textured geomembranes.
Quantitative Analysis of Microstructure Properties and their Influence on Macroscale Response
J. David Frost,Nimisha Roy,Chien-Chang Chen,박진영,Deh-Jeng Jang,Ye Lu,Jie Cao 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.9
The shear behavior of soils is typically related to the state of the soil in terms of the initial global void ratio and effective confining stress. However, laboratory tests on reconstituted sand specimens have shown that the shear behavior is also dependent upon the specimen preparation method. This paper describes the findings of a series of studies, which quantitatively evaluated the differences in the inherent microstructure of dilatant sand specimens prepared by air pluviation, moist tamping and water deposition. Quantitative measures such as local void ratio distribution, local void ratio distribution entropy and particle orientation entropy were found to be dependent on the preparation method. Microstructure evolution in the sand specimens during triaxial compression testing was also investigated. Measuring global properties of the specimens was shown to mask the complex and evolving internal conditions during shear. The global response was found to be strongly dependent on the shear induced microstructure which in turn was directly influenced by the preparation method dependent inherent microstructure.
Brain mu-opioid receptor binding: relationship to relapse to cocaine use after monitored abstinence.
Gorelick, David A,Kim, Yu Kyeong,Bencherif, Badreddine,Boyd, Susan J,Nelson, Richard,Copersino, Marc L,Dannals, Robert F,Frost, J James Springer-Verlag 2008 Psychophamacology Vol.200 No.4
<P>Cocaine users have increased regional brain mu-opioid receptor (mOR) binding which correlates with cocaine craving. The relationship of mOR binding to relapse is unknown.</P>
Duenas-Osorio, Leonardo,Park, Joonam,Towashiraporn, Peeranan,Goodno, Barry J.,Frost, David,Craig, James I.,Bostrom, Ann Techno-Press 2004 Structural Engineering and Mechanics, An Int'l Jou Vol.17 No.3
Consequence-Based Engineering (CBE) is a new paradigm proposed by the Mid-America Earthquake Center (MAE) to guide evaluation and rehabilitation of building structures and networks in areas of low probability - high consequence earthquakes such as the central region of the U.S. The principal objective of CBE is to minimize consequences by prescribing appropriate intervention procedures for a broad range of structures and systems, in consultation with key decision makers. One possible intervention option for rehabilitating unreinforced masonry (URM) buildings, widely used for essential facilities in Mid-America, is passive energy dissipation (PED). After the CBE process is described, its application in the rehabilitation of vulnerable URM building construction in Mid-America is illustrated through the use of PED devices attached to flexible timber floor diaphragms. It is shown that PED's can be applied to URM buildings in situations where floor diaphragm flexibility can be controlled to reduce both out-of-plane and in-plane wall responses and damage. Reductions as high as 48% in roof displacement and acceleration can be achieved as demonstrated in studies reported below.