| 51. |
- Al-Hamadandy, Raied, et al.
(författare)
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Oxygen vacancy migration in compressively strained SrTiO3
- 2013
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 113:2
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Tidskriftsartikel (refereegranskat)abstract
- The intrinsic properties of strontium titanate render it promising in applications such as gate dielectrics and capacitors. However, there is growing evidence that oxygen vacancies significantly impact upon its use, with the diffusion and deep donor level of the oxygen vacancy leading to electrical leakage. Where grown epitaxially on a lattice mismatched substrate, SrTiO 3 undergoes bi-axial strain, altering its crystal structure and electronic properties. In this paper, we present the results of first-principles simulations to evaluate the impact of strain in a (001) plane upon the migration of oxygen vacancies. We show that in the range of strains consistent with common substrate materials, diffusion energies in different directions are significantly affected, and for high values of strain may be altered by as much as a factor of two. The resulting diffusion anisotropy is expected to impact upon the rate at which oxygen vacancies are injected into the films under bias, a critical factor in the leakage and resistive switching seen in this material
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| 52. |
- Al-Hamadany, R., et al.
(författare)
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Impact of tensile strain on the oxygen vacancy migration in SrTiO3 : Density functional theory calculations
- 2013
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 113:22
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Tidskriftsartikel (refereegranskat)abstract
- Strontium titanate is a promising dielectric material for device applications including capacitors and gate dielectrics. However, oxygen vacancies, which are inevitable donor defects mobile under bias at room temperature, lead to undesirable leakage current in SrTiO3 thin films. Epitaxially grown SrTiO3 on lattice mismatched substrates leads to strained SrTiO3, inducing structural phase transitions from a cubosymmetric non-ferroelectric geometry to tetragonal and orthorhombic structures, depending upon the sign of the strain. In this study, density functional calculations have been performed to determine the impact of isotropic biaxial tensile strain in a (001) plane upon the phase of SrTiO3 and the activation energy for the migration of oxygen vacancies in such strained SrTiO3. The phase transition of the host material yields anisotropy in oxygen vacancy diffusion for diffusion within and between planes parallel to the strain. We found a general reduction in the barrier for diffusion within and normal to the plane of tensile strain. The inter-plane diffusion barrier reduces up to 25% at high values of strain. The variation in the barrier corresponding to in-plane diffusion is smaller in comparison to inter-plane diffusion. Finally, we reflect upon how the interplay between lattice strain with native defects plays a crucial role in the conduction mechanism of thin film, strained SrTiO3
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| 53. |
- Al-Rawabdeh, Abdulla M., et al.
(författare)
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A GIS-based drastic model for assessing aquifer vulnerability in Amman-Zerqa groundwater basin, Jordan
- 2013
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Ingår i: Engineering. - : Scientific Research Publishing, Inc.. - 1947-3931 .- 1947-394X. ; :5, s. 490-504
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Tidskriftsartikel (refereegranskat)abstract
- Amman-Zerqa Basin (AZB) is a major basin in Jordan. The concentration of economic, agricultural and social activities within the basin makes it of prime importance to Jordan. Intensive agricultural practices are widespread and located close to groundwater wells, which pose imminent threats to these resources. Groundwater contamination is of particular concern as groundwater resources are the principal source of water for irrigation, drinking and industrial activities. A DRASTIC model integrated with, and GIS tool has been used to evaluate the groundwater vulnerability of AZB. The Drastic index map showed that only 1.2% of the basin’s total area of 3792 km2 lies in the no vulnerable zone and about 69% is classified as having low pollution potential. The results also revealed that about 30% of the catchment area is moderately susceptible to pollution potential and slightly 1% is potentially under high pollution risk. These results suggest that almost one third of the AZB is at moderate risk of pollution potential. These areas are mainly in the north-east and central parts of the basin where the physical factors like gentle slope and high water table well support the chances of getting shallow aquifer water polluted. Areas with high vulnerable pollution are mainly the central of Amman old city.
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| 54. |
- Al-Rubaei, Ahmed, et al.
(författare)
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Long-term hydraulic performance of porous asphalt pavements in northern Sweden
- 2013
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Ingår i: Journal of irrigation and drainage engineering. - 0733-9437 .- 1943-4774. ; 139:6, s. 499-505
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Tidskriftsartikel (refereegranskat)abstract
- The effect of clogging on the long-term infiltration capacity and porosity of two 18- and 24-year-old porous asphalts was examined by using replicate double-ring infiltrometer tests and analyzing asphalt core samples. Tests were carried out to see if high pressure washing and vacuum cleaning could restore the hydraulic performance. The infiltration capacity of the porous asphalts decreased substantially, primarily due to surficial clogging (0.50 +/- 0.26 in Lulea, Sweden, and 0.22 +/- 0.12 in Haparanda, Sweden, compared to initially > 290 mm min(-1)). In Lulea, washing and vacuum cleaning could partially restore the infiltration capacity (3.48 +/- 3.00 mm min(-1)), but in Haparanda, no effect was measured. The porosity was constantly between 16 and 18%. The difference of the long-term behavior and effect of cleaning in Lulea and Haparanda is primarily attributable to different street maintenance, age, and winter maintenance (application of fine gravel and/or sand). Although the infiltration capacity in Lulea was far below initial values, the asphalt still has the capacity to infiltrate an intense design rainfall (100 year average return interval, 15 min duration), underlining that porous asphalt can be a resilient feature also under nonfavorable conditions
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| 55. |
- Al-Rubaei, Ahmed, et al.
(författare)
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Long-term hydraulic performance of stormwater infiltration systems : a field survey
- 2013
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Ingår i: NOVATECH 2013.
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Konferensbidrag (refereegranskat)abstract
- This paper examined the factors influencing the long-term hydraulic performance of some stormwater infiltration systems (swale and two types of permeable pavements) in Växjö, southern Sweden. The infiltration capacities of 9 permeable pavements and 2 swales sites, all with different ages ranging from 1 year to 14 years, were measured using replicate double ring infiltrometers. The sites were either constructed of swale (2), interlocking concrete pavers (ICP) filled with gravel (2), concrete grid pavers (CGP) filled with gravel (3), or concrete grid pavers (CGP) filled with grass (4). The results of this study showed that the long-term behaviour of the infiltration capacity relies largely on the type and age of the system and the type of joint filling (gravel and grass). Furthermore, the study showed that the 11 year old concrete grid pavers filled with grass had the highest infiltration capacity (4.80 + 2.46 mm/min), whilst the 9 and 14 year old swales had the lowest infiltration capacity (0.10 + 0.00 mm/min).
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| 56. |
- Al-Taie, Entidhar, et al.
(författare)
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Foundation assessment in different parts of Iraq using STAAD Pro v8i
- 2013
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Ingår i: Journal of Civil Engineering and Architecture. - : David Publishing Company. - 1934-7359 .- 1934-7367. ; 7:3, s. 273-281
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Tidskriftsartikel (refereegranskat)abstract
- Foundation is considered as one of the main parts of any structure such as buildings, railways, bridges, etc. The type of foundation used is highly dependent on the type and properties of soil. The design of foundations requires many factors that should be defined such as the load that the foundation is going to hold, geological conditions of the soil under the foundation, type of soil and the local building code criteria.There are number of differences in the geological and soil conditions in Iraq. As a consequence, these differences are reflected on the type of foundation to be used. Despite these differences, same materials and style of buildings are used all over Iraq. The main problems of Iraqi soil are high gypsum content, salinity and shallow water table depth. These factors that influence the foundations are the soil properties and the amount of loads that transmitted by the superstructure.The situation had been analysed through a case study which illustrated the link between soil and foundation types in three different parts of Iraq (Mosul, Baghdad and Basra). One building was analysed using STAAD. Pro software in these regions. It is evident that Iraqi designers and engineers require local code to define all the loads, materials and design of the foundation to be used. The use of local materials might be very effective from both engineering and economic perspectives.
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| 57. |
- Al-Taie, Entidhar
(författare)
-
Foundations of educational buildings in Iraq : past, present and future
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Foundation is considered as one of the main parts of any structure such as buildings, railways, bridges, etc. The type of foundation used is highly dependent on the type and properties of soil. The design of foundations requires many factors that should be defined such as the load that the foundation is going to hold, geological conditions of the soil under the foundation, type of soil and the local building code criteria.There are number of differences in the geological and soil conditions in Iraq. As a consequence, these differences are reflected on the type of foundation to be used. Despite these differences, same materials and style of buildings are used all over Iraq. To have good information about the materials and the required design of the foundation, a comprehensive historical review was executed to highlight the progress of the materials and types of foundation that was used since the dawn of civilization up to the present (ancient, Islamic, Ottoman and British occupation till after independent). Present day situation had been analysed through a case study which illustrated the link between soil and foundation types in three different parts of Iraq (Mosul, Baghdad and Basrah). One building was analysed using STAAD. Pro software in these regions. Furthermore, the same building was analysed using local materials, which were historically used and was compared with present day materials used.It is evident that Iraqi designers and engineers require local code to define all the loads, materials and design of the foundation to be used. The use of local materials might be very effective from both engineering and economic perspectives.
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| 58. |
- Al-Taie, Laith, et al.
(författare)
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Hazardous wastes problems in Iraq:a suggestion for an environmental solution
- 2013
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Ingår i: Journal of Earth Sciences and Geotechnical Engineering. - : Scienpress Ltd. - 1792-9040 .- 1792-9660. ; 3:3, s. 81-91
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Tidskriftsartikel (refereegranskat)abstract
- Iraq passed through many destructive wars where the country infrastructures have been destroyed. Consequently, various types of hazardous wastes generated from 1991 and 2003 wars are exposed in different parts of Iraq without any aspect of human and environment considerations. Contaminants are found in the form of contaminated rubble with depleted uranium (DU). Landfill disposal is still an economical and vital solution that should serve between 300-1000 years for confining hazardous wastes like DU. The longevity of a hazardous waste landfill is mainly controlled by clay based liners. There are many factors affecting the performance of clay liners. These factors were discussed. The main requirements of hazardous waste landfills were listed according to USEPA and German regulations. Finally, the main aspects of landfill siting criteria in Iraq were suggested.
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| 59. |
- Al-Taie, Laith, et al.
(författare)
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Hydraulic properties of smectite clays from Iraq with special respect to landfills of DU-contaminated waste
- 2013
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Ingår i: Journal of Earth Sciences and Geotechnical Engineering. - : Scienpress Ltd. - 1792-9040 .- 1792-9660. ; 3:3, s. 109-125
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Tidskriftsartikel (refereegranskat)abstract
- Landfills of material contaminated by depleted uranium and other low-level radioactive waste must be isolated from the biosphere for a sufficiently long time. This can be effectively made in desert climate by collecting contaminated waste in suitable areas confined by tight embankments and covering them with very tight clay liners protected from desiccation and erosion by suitably composed filters and coarse rock fill. Examples of design principles and construction are described in the paper. The clay liners are made of air-dry expanding clay that can be found in sufficient quantities in Iraq and that provide very good tightness at low cost. The construction technique is well known from various projects.
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| 60. |
- Alakangas, Lena, et al.
(författare)
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Literature review on potential geochemical and geotechnical effects of adopting paste technology under cold climate conditions
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this literature review is to summarize the recent research regarding geochemical and geotechnical stability of paste tailings, identify knowledge gaps and future research needs. The present study has been conducted by the Division of Geosciences and Environmental Engineering together with the Division of Mining and Geotechnical Engineering at Luleå University of Technology on behalf of Boliden Mineral, LKAB and Outotec.A survey conducted by MEND (Mine Environment Neutral Drainage) in 2006 on the environmental effects related to the use of paste tailings summarizes that only a few studies had been performed about long-term effects on the surface and groundwater quality. Instead, the focus had been on the additives and the strength of the paste. It is still uncertain how the paste technology affects the long-term environmental stability from a geochemical point of view. Concerns regarding the stability of paste with high sulphide content are still relevant. Studies performed indicate that sulphide oxidation occurs within cemented paste as well as on the surface of non-cemented paste and cracks formed on the surfaces could induce oxidation. For cemented paste, metals released by sulphide oxidation might be sequestered due to high pH induced by the alkaline additives, but anion such as Se has been shown to be mobilized. The leachate has been shown to be near-neutral initially, but the neutrality decreases with time and probably metals sequestered in the matrix will also be released. Again, it should be noted that no long term study was performed on leaching of paste, cemented or uncemented. The longest leaching study was performed for one year. Arsenic has been proven to be retained in Ca-arsenates in cemented paste, but the long term stability of these precipitates is relatively unknown. Expanded secondary phases e.g. gypsum and ettringite have been observed to form when there is sulphate in the process or drainage of water. These phases could crack the paste, but, on the other hand, can also fill former cracks when deposited in layers. The effects of the formation of these phases are relatively uncertain in a long-term perspective. Presence of different elements such as ammonium, sulphates and metals in the water has been shown to negatively affect the curing process and therefore water is suggested to be treated before use. The presence of carbon dioxide during the paste formation could also affect the curing process, but could sequester metals in carbonate phases.Geotechnical and rheological properties of paste is well defined and documented. Several case studies have been found in literature providing valuable information about the details of the works being carried out. However, a difficulty has been noted during the investigation of the effects of cold climate conditions when current practice is applied in the colder parts of the world. It is not certain how some specific and vital parameters are going to be affected by cold temperatures. Parameters such as deposition slopes and deposition scheme, strength development of the paste are expected to be responsive to cold climate conditions. There are predictions about which properties are going to be affected in what way, but there is also a need to establish a scientific base for discussion. These have been highlighted as research needs and information gaps at the end of the report.
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