| 51. |
- Aitomäki, Yvonne, et al.
(författare)
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Hydrogel state impregnation of cellulose fibre-phenol composites: Effects of fibre size distribution
- 2016
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Ingår i: ECCM 2016. - : European Conference on Composite Materials. - 9783000533877
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Konferensbidrag (refereegranskat)abstract
- Whilst it has been well established that cellulose nanofibres (CNF) networks produce films that have high stiffness and strength, they are difficult to impregnate. Investigated in this study is whether by controlling the degree of nanofibrillation of cellulose, composites based on micro- and nano-size cellulose fibres can be made that are more easily manufactured and have better impregnation than solely cellulose nano-fibre based composites. To evaluate this, cellulose at different stages of ultrafine grinding, extracted at time intervals of 30, 60 and 290 mins, were used to make composites. To achieve good impregnation a novel strategy was used based on impregnation with phenol resin whilst the fibrillated cellulose is in a hydrogel state. The composites were subsequently dried and consolidated by hot press. The current results show that this method of impregnation is successful and the phenol matrix greatly improves the properties of the cellulose with a low degree of fibrillation. In general, as the degree of fibrillation and the proportion of nanofibres increases, the mechanical properties of the networks and their composites increase. The addition of the matrix appears to restrict the deformation of CNF network, increasing the modulus and yield strength but decreasing the ultimate strength. The method also appears to restrict the consolidation and voids remain in the composite, which reduces the modulus when compared to theoretical maximum values for this material. More work on the consolidation process is necessary to achieve the full potential of these composites.
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| 52. |
- Aitomäki, Yvonne, et al.
(författare)
-
Light scattering in cellulose nanofibre suspensions : Model and experiments
- 2016
-
Ingår i: Computers in Chemistry Proceeding from ACS National Meeting San Diego. - : American Chemical Society (ACS). ; , s. 122-
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Here light scattering theory is used to assess the size distribution in a suspension of cellulose as it is fibrillated from micro-scaled to nano-scaled fibres. A model based on Monte carlo simulations of the scattering of photons by different sizes of cellulose fibres was used to predict the UV-IF spectrum of the suspensions. Bleached cellulose hardwood pulp was tested and compared to the visually transparent tempo-oxidised hardwood cellulose nanofibres (CNF) suspension. The theoretical results show that different diameter size classes exhibit very different scattering patterns. These classes could be identified in the experimental results and used to establish the size class dominating the suspension. A comparison to AFM/microscope size distribution was made and the results indicated that using the UV-IF light scattering spectrum maybe more reliable that size distribution measurement using AFM and microscopy on dried CNF samples. The UV-IF spectrum measurement combined with the theoretical prediction can be used even at this initial stage of development of this model to assess the degree of fibrillation when processing CNF.
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| 53. |
- Aitomäki, Yvonne, et al.
(författare)
-
Nanofibre distribution in composites manufactured with epoxy reinforced with nanofibrillated cellulose : model prediction and verification
- 2016
-
Ingår i: IOP Conference Series. - 1757-8981 .- 1757-899X. ; 139
-
Tidskriftsartikel (refereegranskat)abstract
- In this study a model based on simple scattering is developed and used to predict the distribution of nanofibrillated cellulose in composites manufactured by resin transfer moulding (RTM) where the resin contains nanofibres. The model is a Monte Carlo based simulation where nanofibres are randomly chosen from probability density functions for length, diameter and orientation. Their movements are then tracked as they advance through a random arrangement of fibres in defined fibre bundles. The results of the model show that the fabric filters the nanofibres within the first 20 µm unless clear inter-bundle channels are available. The volume fraction of the fabric fibres, flow velocity and size of nanofibre influence this to some extent. To verify the model, an epoxy with 0.5 wt.% Kraft Birch nanofibres was made through a solvent exchange route and stained with a colouring agent. This was infused into a glass fibre fabric using an RTM process. The experimental results confirmed the filtering of the nanofibres by the fibre bundles and their penetration in the fabric via the inter-bundle channels. Hence, the model is a useful tool for visualising the distribution of the nanofibres in composites in this manufacturing process.
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| 54. |
- Aitomäki, Yvonne, et al.
(författare)
-
Vacuum infusion of cellulose nanofibre network composites : Influence of porosity on permeability and impregnation
- 2016
-
Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 95, s. 204-211
-
Tidskriftsartikel (refereegranskat)abstract
- Addressing issues around the processing of cellulose nanofibres (CNF) composites is important in establishing their use as sustainable, renewable polymer reinforcements. Here, CNF networks of different porosity were made with the aim of increasing their permeability and suitability for processing by vacuum infusion (VI). The CNF networks were infused with epoxy using two different strategies. The permeability, morphology and mechanical properties of the dry networks and the resulting nanocomposites were investigated. Calculated fill-times for CNF networks with 50% porosity were the shortest, but are only less than the gel-time of the epoxy if capillary effects are included. In experiments the CNF networks were clearly wetted. However low transparency indicated that impregnation was incomplete. The modulus and strength of the dry CNF networks increased rapidly with decreasing porosity, but their nanocomposites did not follow this trend, showing instead similar mechanical properties to each other. The results demonstrated that increasing the porosity of the CNF networks to ≈ 50% gives better impregnation resulting in a lower ultimate strength, a higher yield strength and no loss in modulus. Better use of the flow channels in the inherently layered CNF networks could potentially reduce void content in these nanocomposites and thus increase their mechanical properties.
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| 55. |
- Akbar, Mariam, et al.
(författare)
-
Efficient Data Gathering in 3D Linear Underwater Wireless Sensor Networks Using Sink Mobility
- 2016
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Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 16:3
-
Tidskriftsartikel (refereegranskat)abstract
- Due to the unpleasant and unpredictable underwater environment, designing an energy-efficient routing protocol for underwater wireless sensor networks (UWSNs) demands more accuracy and extra computations. In the proposed scheme, we introduce a mobile sink (MS), i.e., an autonomous underwater vehicle (AUV), and also courier nodes (CNs), to minimize the energy consumption of nodes. MS and CNs stop at specific stops for data gathering; later on, CNs forward the received data to the MS for further transmission. By the mobility of CNs and MS, the overall energy consumption of nodes is minimized. We perform simulations to investigate the performance of the proposed scheme and compare it to preexisting techniques. Simulation results are compared in terms of network lifetime, throughput, path loss, transmission loss and packet drop ratio. The results show that the proposed technique performs better in terms of network lifetime, throughput, path loss and scalability
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| 56. |
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| 57. |
- Al-Anbari, Mohammad, et al.
(författare)
-
Estimation of Domestic Solid Waste Amount and Its Required Landfill Volume in Najaf Governorate-Iraq for the Period 2015-2035
- 2016
-
Ingår i: Engineering. - : Scientific Research Publishing, Inc.. - 1947-3931 .- 1947-394X. ; 8:6, s. 339-346
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Tidskriftsartikel (refereegranskat)abstract
- Solid waste management is one of the most important challenges facing the local administration in the governorate of Najaf. This paper investigates the domestic amount generated in Najaf gover- norate for period 2015-2035 and the required landfill volume for the disposal of the waste. The daily per capita waste generation in Al-Najaf is 0.42 kg, the humidity content about 43% and the ound 473 kg/m3. The total amount was about 5,914,415 ton and the required landfill volume is 11,828,829 m3.
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| 58. |
- Al-Anbari, Mohammad, et al.
(författare)
-
Landfill Site Selection in Al-Najaf Governorate, Iraq
- 2016
-
Ingår i: Journal of Civil Engineering and Architecture. - : David Publishing Company. - 1934-7359 .- 1934-7367. ; 10:6, s. 651-660
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Tidskriftsartikel (refereegranskat)abstract
- Solid waste management aspect is one of the most important challenges facing the local administration in the Governorate of Najaf. Therefore, this study aims to provide for solid waste management problem by choosing the best locations for the establishment of sanitary landfills in the governorate. In this study, GIS (geographic information system) and MCDA (multi-criteria decision analysis) were used based on 17 environmental, economic and geological criteria converted to input digital map layers. These were urban centres, cemetery, airports, electrical power lines, oil pipes, railways, roads, slope, historical sites, main rivers,industrial areas, religion sites, wells, military area, electrical power plants, nature reserves and national borders to select most importance sites in the governorate. AHP (analytic hierarchy process) method was used in weighting the criteria used. All layers’ maps were graded from 0 (not suitable) to 5 (most suitable) using spatial information scale then SAW (simple additive weighting)method was integrated in GIS used to calculate the suitability index for the studied area. The results indicated that 4.4% of the study region is suitable for land¿ll siting with grading values greater than 4.0. This included five sites distributed in three qadhaas of governorate.
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| 59. |
- Al-Anbari, Mohammad, et al.
(författare)
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Ranking Landfill Sites in Najaf Governorate, Iraq Using AHP and Fuzzy TOPSIS Methods
- 2016
-
Ingår i: Journal of Civil Engineering and Architecture. - : David Publishing Company. - 1934-7359 .- 1934-7367. ; 10:8, s. 815-821
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Tidskriftsartikel (refereegranskat)abstract
- In Najaf Governorate, Iraq, there are five landfill sites. This study aims to rank these sites based on their criteria which are site capacity, land elevation and land price. AHP (analytic hierarchy process) method was used to weight the criteria and the technique for order preference by similarity to ideal solution. Fuzzy TOPSIS (technique for order of preference by similarity to ideal solution) method was used to rank these sites from best to worst. Based on AHP method, the site capacity criterion was the most important than land price and land elevation.
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| 60. |
- Al-Ansari, Nadhir
(författare)
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Hydro-Politics of the Tigris and Euphrates Basins
- 2016
-
Ingår i: Engineering. - : Scientific Research Publishing, Inc.. - 1947-3931 .- 1947-394X. ; 8:3, s. 140-172
-
Tidskriftsartikel (refereegranskat)abstract
- The supply of fresh water is essential to life, socioeconomic development, and political stability in Middle East. Turkey, Syria and Iraq are the main riparian countries in the Tigris-Euphrates basin. Turkey is the riparian hegemon for a long time due to its structural power and dominant river position. Iraq and Syria are the lower countries in the basin and for this reason they always like toensure the quantity of water required to satisfy their requirements. The conflict between riparian countries is due to several factors. These are: population growth rate and food security, energy security, economic and technological development, political fragmentation, international water laws, water and management availability and public awareness. There have been a number of attempts to find a common ground on water issues between the main three riparian countries since 1920 but no agreement signed yet. Present situation is very bad in Syria and Iraq where thousands of people have no access to water and farmers are leaving their land because of draught. Such situation will definitely raise tension and might lead to war. To avoid this, a mediator that has the capability to bring all countries concerned to the negotiation table is required. In addition, Syria and Iraq are to adopt prudent strategic plan based on resources development theory to ensure good water management and minimum water loses.
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