An in-vitro experiment was conducted to assess the interaction between biochar and algae on a problem soil. Experiments were performed with and without algae to observe the effectiveness of algae for overcoming the ch...An in-vitro experiment was conducted to assess the interaction between biochar and algae on a problem soil. Experiments were performed with and without algae to observe the effectiveness of algae for overcoming the challenges posed by problem soils. At the end of incubation periods, the adsorption and desorption of phosphorus (P) on a problem soil vis-á-vis algal inoculation were determined. Our results showed that different types of biochars adsorbed different amounts of P suggesting that the source of biochar played a crucial role in determining its behavior towards P. Tannery waste biochar significantly adsorbed 147% and 35% more P compared to that of the chicken litter and orange peel biochars respectively. Significant reductions in adsorption were observed when the biochar was used in combination with the algae which could be due to the beneficial effects of algae leading to the amelioration of the problem soil. Adsorption was reduced to 34%, 24% and 20% for the orange peel biochar + algae, chicken litter biochar + algae and tannery waste biochar + algae, respectively compared to the corresponding biochars present as a single solid. Phosphorus (P) desorption was also reduced significantly in presence of algal inoculation. Overall our findings suggest that the application of algae along with biochar in the problem soil could reduce the adsorption of P which would influence the availability of P.展开更多
The possibilities of the particle finite element method(PFEM)for modeling geotechnical problems are increasingly evident.PFEM is a numerical approach to solve large displacement and large strain continuum problems tha...The possibilities of the particle finite element method(PFEM)for modeling geotechnical problems are increasingly evident.PFEM is a numerical approach to solve large displacement and large strain continuum problems that are beyond the capabilities of classical finite element method(FEM).In PFEM,the computational domain is reconfigured for optimal solution by frequent remeshing and boundary updating.PFEM inherits many concepts,such as a Lagrangian description of continuum,from classic geomechanical FEM.This familiarity with more popular numerical methods facilitates learning and application.This work focuses on G-PFEM,a code specifically developed for the use of PFEM in geotechnical problems.The article has two purposes.The first is to give the reader an overview of the capabilities and main features of the current version of the G-PFEM and the second is to illustrate some of the newer developments of the code.G-PFEM can solve coupled hydro-mechanical static and dynamic problems involving the interaction of solid and/or deformable bodies.Realistic constitutive models for geomaterials are available,including features,such as structure and destructuration,which result in brittle response.The solutions are robust,solidly underpinned by numerical technology including mixedfield formulations,robust and mesh-independent integration of elastoplastic constitutive models and a rigorous and flexible treatment of contact interactions.The novel features presented in this work include the contact domain technique,a natural way to capture contact interactions and impose contact constraints between different continuum bodies,as well as a new simplified formulation for dynamic impact problems.The code performance is showcased by the simulation of several soil-structure interaction problems selected to highlight the novel code features:a rigid footing insertion in soft rock,pipeline insertion and subsequent lateral displacement on over-consolidated clay,screw-pile pull-out and the dynamic impact of a free-falling spherical penetrometer into clay.展开更多
Continuous monoculture problems, or replanting diseases, are one of the key factors affecting productivity and quality of Chinese medicinal plants. The underlying mechanism is still being explored. Most of the studies...Continuous monoculture problems, or replanting diseases, are one of the key factors affecting productivity and quality of Chinese medicinal plants. The underlying mechanism is still being explored. Most of the studies on continuous monoculture ofRehmannia glutinosa L. are focused on plant nutritional physiology, root exudate, and its autotoxieity. However, the changes in the diversity of microflora in the rhizosphere mediated by the continuous monoculture pattern have been remained unknown. In this study, terminal restriction fragment length polymorphism （T-RFLP） technique was used for fingerprinting fungal diversity in the rhizosphere soil sampled from the fields ofR. glutinosa monocultured for 1 and 2 yr. The results showed that the structure of fungal community in consecutively moncultured rhizosphere soil was different from that in control soil （no cropping soil）, and varied with the consecutive monoeulture years （1 and 2 yr）. The comprehensive evaluation index （D） of fungal community estimated by principal component analysis of fragment number, peak area, Shannon-Weiner index, and Margalef index was higher in 1 yr monoculture soil than that in 2 yr monoculture soil, suggesting that consecutive monoculture of R. glutinosa could be a causative agent to decrease the diversity of fungal community in the rhizosphere soil.展开更多
This paper deals mainly to study and solve field drainage problems in Kamal El-Den Hessen new reclaimed area (1650 hectares), North Sinai Egypt, where many farmers complain about the formation of water ponds in their ...This paper deals mainly to study and solve field drainage problems in Kamal El-Den Hessen new reclaimed area (1650 hectares), North Sinai Egypt, where many farmers complain about the formation of water ponds in their lands, bad soil drainage, soil salinity, and low yields rate. Intensive field investigations were carried out regarding, topographic survey, digging 22 boreholes, instilling observation wells, measuring groundwater salinity and assessing the existing drainage network. The results showed that ground surface levels were ranging from 1.5 m to 4.28 m above mean sea level, predominated soil was sandy with a permeability coefficient ranged from 0.82 to 2.68 m/day, an impervious clay layer lies at 6.0 to 7.0 m below ground surface, and the groundwater salinity ranges from 4 to 12 dS/m high salinity for water ponds were observed at the observation wells that lay in the lift side of Kamal El-Den Hessen Canal. Lands surrounding Kamal El-Den Hessen Canal have high levels. The measured groundwater depths of the western observation wells were 0.50 m below ground surface and in the eastern wells ranging from 1.0 to 1.50 m. The analysis of results showed that field drainage problems that increased groundwater levels were: 1) infiltration water coming from the high-cultivated areas at the lift bank of Kamal El-Den Hessen Canal, 2) the impervious clay layers increasing the horizontal infiltration towards low lands and increase ponds areas. 3) Main Gelbana Drain cross-section needs dredging. It is recommended to dredge the Main Gelbana Drain and modified its cross-section to collect water from water ponds, filling the lowland areas utilizing sandy soil in the high lands, adopting types of crops grown to match with crop salt tolerant levels and soil and water salinity levels and constructing subsurface drainage network to decrease groundwater levels.展开更多
One-dimensional non-Darcy flow in a semi-infinite porous media is investigated. We indicate that the non-Darcy relation which is usually determined from experimental results can always be described by a piecewise line...One-dimensional non-Darcy flow in a semi-infinite porous media is investigated. We indicate that the non-Darcy relation which is usually determined from experimental results can always be described by a piecewise linear function, and the problem can be equivalently transformed to a multiphase implicit Stefan problem. The novel feature of this Stefan problem is that the phases of the porous media are divided by hydraulic gradients, not the excess pore water pressures. Using the similarity transformation technique, an exact solution for the situation that the external load increases in proportion to the square root of time is developed. The study on the existence and uniqueness of the solution leads to the requirement of a group of inequalities. A similar Stefan problem considering constant surface seepage velocity is also investigated, and the solution, which we indicate to be uniquely existent under all conditions, is established. Meanwhile, the relation between our Stefan problem and the traditional multiphase Stefan problem is demonstrated. In the end, computational examples of the solution are presented and discussed. The solution provides a useful benchmark for verifying the accuracy of general approximate algorithms of Stefan problems, and it is also attractive in the context of inverse problem analysis.展开更多
文摘An in-vitro experiment was conducted to assess the interaction between biochar and algae on a problem soil. Experiments were performed with and without algae to observe the effectiveness of algae for overcoming the challenges posed by problem soils. At the end of incubation periods, the adsorption and desorption of phosphorus (P) on a problem soil vis-á-vis algal inoculation were determined. Our results showed that different types of biochars adsorbed different amounts of P suggesting that the source of biochar played a crucial role in determining its behavior towards P. Tannery waste biochar significantly adsorbed 147% and 35% more P compared to that of the chicken litter and orange peel biochars respectively. Significant reductions in adsorption were observed when the biochar was used in combination with the algae which could be due to the beneficial effects of algae leading to the amelioration of the problem soil. Adsorption was reduced to 34%, 24% and 20% for the orange peel biochar + algae, chicken litter biochar + algae and tannery waste biochar + algae, respectively compared to the corresponding biochars present as a single solid. Phosphorus (P) desorption was also reduced significantly in presence of algal inoculation. Overall our findings suggest that the application of algae along with biochar in the problem soil could reduce the adsorption of P which would influence the availability of P.
基金financial support by Severo Ochoa Centre of Excellence (2019-2023) Grant No. CEX2018-000797-Sfunded by MCIN/AEI/10.13039/501100011033+1 种基金research projects BIA2017-84752-RPID2020-119598RB-I00
文摘The possibilities of the particle finite element method(PFEM)for modeling geotechnical problems are increasingly evident.PFEM is a numerical approach to solve large displacement and large strain continuum problems that are beyond the capabilities of classical finite element method(FEM).In PFEM,the computational domain is reconfigured for optimal solution by frequent remeshing and boundary updating.PFEM inherits many concepts,such as a Lagrangian description of continuum,from classic geomechanical FEM.This familiarity with more popular numerical methods facilitates learning and application.This work focuses on G-PFEM,a code specifically developed for the use of PFEM in geotechnical problems.The article has two purposes.The first is to give the reader an overview of the capabilities and main features of the current version of the G-PFEM and the second is to illustrate some of the newer developments of the code.G-PFEM can solve coupled hydro-mechanical static and dynamic problems involving the interaction of solid and/or deformable bodies.Realistic constitutive models for geomaterials are available,including features,such as structure and destructuration,which result in brittle response.The solutions are robust,solidly underpinned by numerical technology including mixedfield formulations,robust and mesh-independent integration of elastoplastic constitutive models and a rigorous and flexible treatment of contact interactions.The novel features presented in this work include the contact domain technique,a natural way to capture contact interactions and impose contact constraints between different continuum bodies,as well as a new simplified formulation for dynamic impact problems.The code performance is showcased by the simulation of several soil-structure interaction problems selected to highlight the novel code features:a rigid footing insertion in soft rock,pipeline insertion and subsequent lateral displacement on over-consolidated clay,screw-pile pull-out and the dynamic impact of a free-falling spherical penetrometer into clay.
基金supported by the National Natural Science Foundation of China (30772729, 30671201, and81072983)the Key Technologies R&D Programof China during the 11th Five-Year Plan period(2006BAI09B03 and 2006BAI06A12-06)
文摘Continuous monoculture problems, or replanting diseases, are one of the key factors affecting productivity and quality of Chinese medicinal plants. The underlying mechanism is still being explored. Most of the studies on continuous monoculture ofRehmannia glutinosa L. are focused on plant nutritional physiology, root exudate, and its autotoxieity. However, the changes in the diversity of microflora in the rhizosphere mediated by the continuous monoculture pattern have been remained unknown. In this study, terminal restriction fragment length polymorphism （T-RFLP） technique was used for fingerprinting fungal diversity in the rhizosphere soil sampled from the fields ofR. glutinosa monocultured for 1 and 2 yr. The results showed that the structure of fungal community in consecutively moncultured rhizosphere soil was different from that in control soil （no cropping soil）, and varied with the consecutive monoeulture years （1 and 2 yr）. The comprehensive evaluation index （D） of fungal community estimated by principal component analysis of fragment number, peak area, Shannon-Weiner index, and Margalef index was higher in 1 yr monoculture soil than that in 2 yr monoculture soil, suggesting that consecutive monoculture of R. glutinosa could be a causative agent to decrease the diversity of fungal community in the rhizosphere soil.
文摘This paper deals mainly to study and solve field drainage problems in Kamal El-Den Hessen new reclaimed area (1650 hectares), North Sinai Egypt, where many farmers complain about the formation of water ponds in their lands, bad soil drainage, soil salinity, and low yields rate. Intensive field investigations were carried out regarding, topographic survey, digging 22 boreholes, instilling observation wells, measuring groundwater salinity and assessing the existing drainage network. The results showed that ground surface levels were ranging from 1.5 m to 4.28 m above mean sea level, predominated soil was sandy with a permeability coefficient ranged from 0.82 to 2.68 m/day, an impervious clay layer lies at 6.0 to 7.0 m below ground surface, and the groundwater salinity ranges from 4 to 12 dS/m high salinity for water ponds were observed at the observation wells that lay in the lift side of Kamal El-Den Hessen Canal. Lands surrounding Kamal El-Den Hessen Canal have high levels. The measured groundwater depths of the western observation wells were 0.50 m below ground surface and in the eastern wells ranging from 1.0 to 1.50 m. The analysis of results showed that field drainage problems that increased groundwater levels were: 1) infiltration water coming from the high-cultivated areas at the lift bank of Kamal El-Den Hessen Canal, 2) the impervious clay layers increasing the horizontal infiltration towards low lands and increase ponds areas. 3) Main Gelbana Drain cross-section needs dredging. It is recommended to dredge the Main Gelbana Drain and modified its cross-section to collect water from water ponds, filling the lowland areas utilizing sandy soil in the high lands, adopting types of crops grown to match with crop salt tolerant levels and soil and water salinity levels and constructing subsurface drainage network to decrease groundwater levels.
基金supported by the Fundamental Research Funds for the Central Universities(Grant 2015XKMS014)
文摘One-dimensional non-Darcy flow in a semi-infinite porous media is investigated. We indicate that the non-Darcy relation which is usually determined from experimental results can always be described by a piecewise linear function, and the problem can be equivalently transformed to a multiphase implicit Stefan problem. The novel feature of this Stefan problem is that the phases of the porous media are divided by hydraulic gradients, not the excess pore water pressures. Using the similarity transformation technique, an exact solution for the situation that the external load increases in proportion to the square root of time is developed. The study on the existence and uniqueness of the solution leads to the requirement of a group of inequalities. A similar Stefan problem considering constant surface seepage velocity is also investigated, and the solution, which we indicate to be uniquely existent under all conditions, is established. Meanwhile, the relation between our Stefan problem and the traditional multiphase Stefan problem is demonstrated. In the end, computational examples of the solution are presented and discussed. The solution provides a useful benchmark for verifying the accuracy of general approximate algorithms of Stefan problems, and it is also attractive in the context of inverse problem analysis.
