| 1. |
- Ackermann, N.L., et al.
(författare)
-
Local scour around circular piers under ice covers
- 2002
-
Ingår i: Ice in the environment. - Dunedin : Dep. of Physic, Univ. of Otago. - 1877139521 ; , s. 149-155
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a laboratory investigation on the effect of ice cover on local scour around circular bridge piers. Experiments were performed in a 12-meter flume with recirculating sediment discharge. Both smooth and rough artificial covers were used. The bed material consisted of uniform ripple-forming sand. The tests were run for both clear water as well as live bed conditions. The results showed that for equivalent averaged flow velocities the existence of an ice cover could increase the local scour depth scour by 25 to 35 % from the free surface condition. The largest difference occurs at a live bed condition when the flow velocity, U, is in the rage of 1.5 to 2 times of the critical velocity for bed movement, U (sub c) . A rough cover gives slightly larger scour depth than a smooth cover. The movement of bed forms led to variations of scour depth with time.
|
|
| 2. |
- Bhalla, Aditya, et al.
(författare)
-
Engineered Lignin in Poplar Biomass Facilitates Cu-Catalyzed Alkaline-Oxidative
- 2018
-
Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 6:3, s. 2932-2941
-
Tidskriftsartikel (refereegranskat)abstract
- Both untransformed poplar and genetically modified “zip-lignin” poplar, in which additional ester bonds were introduced into the lignin backbone, were subjected to mild alkaline and copper-catalyzed alkaline hydrogen peroxide (Cu-AHP) pretreatment. Our hypothesis was that the lignin in zip-lignin poplar would be removed more easily than lignin in untransformed poplar during this alkaline pretreatment, resulting in higher sugar yields following enzymatic hydrolysis. We observed improved glucose and xylose hydrolysis yields for zip-lignin poplar compared to untransformed poplar following both alkaline-only pretreatment (56% glucose yield for untransformed poplar compared to 67% for zip-lignin poplar) and Cu-AHP pretreatment (77% glucose yield for untransformed poplar compared to 85% for zip-lignin poplar). Compositional analysis, glycome profiling, and microscopy all supported the notion that the ester linkages increase delignification and improve sugar yields. Essentially no differences were noted in the molecular weight distributions of solubilized lignins between the zip-lignin poplar and the control line. Significantly, when zip-lignin poplar was utilized as the feedstock, hydrogen peroxide, catalyst, and enzyme loadings could all be substantially reduced while maintaining high sugar yields.
|
|
| 3. |
- Ji, Cheng, et al.
(författare)
-
Crystallography of low Z material at ultrahigh pressure : Case study on solid hydrogen
- 2020
-
Ingår i: Matter and Radiation at Extremes. - : American Institute of Physics (AIP). - 2468-2047 .- 2468-080X. ; 5:3
-
Tidskriftsartikel (refereegranskat)abstract
- Diamond anvil cell techniques have been improved to allow access to the multimegabar ultrahigh-pressure region for exploring novel phenomena in condensed matter. However, the only way to determine crystal structures of materials above 100 GPa, namely, X-ray diffraction (XRD), especially for low Z materials, remains nontrivial in the ultrahigh-pressure region, even with the availability of brilliant synchrotron X-ray sources. In this work, we perform a systematic study, choosing hydrogen (the lowest X-ray scatterer) as the subject, to understand how to better perform XRD measurements of low Z materials at multimegabar pressures. The techniques that we have developed have been proved to be effective in measuring the crystal structure of solid hydrogen up to 254 GPa at room temperature [C. Ji et al., Nature 573, 558–562 (2019)]. We present our discoveries and experiences with regard to several aspects of this work, namely, diamond anvil selection, sample configuration for ultrahigh-pressure XRD studies, XRD diagnostics for low Z materials, and related issues in data interpretation and pressure calibration. We believe that these methods can be readily extended to other low Z materials and can pave the way for studying the crystal structure of hydrogen at higher pressures, eventually testing structural models of metallic hydrogen.
|
|
