Global precipitation products from remote sensing observations or numerical models enable us to understand hydrological processes, especially in remote and ungauged watersheds. However, previous studies have shown that there is significant inconsistency among the products especially in arid and semi-arid areas. GPCC, WM, and TRMM products where investigated over the UAE over a time period of 11 years using observation from 6 stations. WM products were found to be the least accurate product over all with range of RSME 9.44 to 19.52mm. The most accurate product was found to be the GPCC with RSME ranging from 3.82mm to 9.98mm. The result showed an overestimation of the observed values across all products. However, the coefficient of correlation was found to be very high for TRMM and GPCC ranging from 0.8450 - 0.9494. This indicates that they are potentially good sources when applied with accurate correction factor.
Direct Contact Membrane Distillation has received much attention due to its total salt rejections and low operational energy demand. There are however many parameters influencing the process demanding a tedious effort to study each parameter individually. High fidelity numerical simulation is the applicable answer particularly when utilizing the advantages of the multiphasic and algorithm in the field of CFD and the advancements in computer speed, memory and storage. In this work, a numerical simulation of the conjugated heat transfer of the feed-membrane-permeate system is developed. Following the initial evaluation of the temperature, pressure and mass flux, the associated latent heat are coupled to compensate for the variability in heat addition or reduction at the feed and permeate membrane surfaces. An updated temperature profile is produced, which endures a slight change from the uncoupled profile. Results suggest the accuracy of conjugated heat model and its reliability in carrying further parametrical studies.
Membrane distillation (MD) is a viable alternative to conventional desalination processes due to its mild operating condition requirements, high fouling resistance and high efficiency in rejection of ions and macromolecules from seawater. Even though MD has advantages over reverse osmosis and thermally driven processes, membranes used in MD process suffer especially from membrane pore wetting and low permeate flow rate issues. Moreover, once a membrane gets wet, it is not possible to achieve desired performance and process would lose its reliability. The aim of this study is to investigate the effects of pore geometry on liquid entry pressure (LEP) as well as wetting phenomena in membrane pores under vacuum membrane distillation (VMD) conditions. Computational fluid dynamics (CFD) simulations were performed for water, membrane, and gas phases by using COMSOL Multiphysics.
The United Arab Emirates (UAE) is a young country located in the arid region of the world. The limited fresh water resources is one of the most burning issues in the country. However, this fact with the harsh desert environmental conditions are the place of birth for the essential oil-bearing plant species. The main purpose of this work is to highlight the main three reasons, that will attract the attention of the decision makers and the whole community, to focus on the indigenous essential oils plant species in the UAE. This will be done, based on representing the environmental, economical and social perspectives.
Prosopis cineraria, a popular and useful ornamental tree of UAE is highly saline and drought tolerant. For further enhancement of the saline and water deficit tolerance of P. cineraria, double rooted grafts were attempted among P. cineraria, and P. cineraria vs P. juliflora. Approach grafting was performed in vivo, using four month old, or one year old plants. In addition, in-vitro grafting was tested on seedlings. Only two grafts were successful among the 50 in-vitro grafting approaches. All others failed to produce true unions. Our results indicate a high level of graft incompatibility within Prosopis sp. and the reasons have to be investigated.
Dynamic soil-vegetation-atmosphere-transport (SVAT) models are important tools to assess the impact of changes in agricultural management practices, irrigation scheduling and changing environmental conditions. Inverse modeling is one approach to calibrate the numerous parameters of those complex models, but dependents in its performance on informative calibration data (observations of the system under study) to achieve a reliable model calibration. We combine global sensitivity analysis and SVAT models to gain a-priori information about the most informative processes regarding the individual model parameters and the required temporal resolutions of the measurements to achieve an optimal design of the field experiments and selection of the environmental variables.
This study aims at optimizing self-consolidated concrete mixes (SCC) under hot weather conditions. The ultimate goal of the research is to have the concrete with superior fresh and mechanical properties, but yet greener. The experiments in this investigation were conducted at Abu Dhabi University Construction materials lab outdoor during summer. The SCC mixtures were continuously mixed for 2 hours at 35 oC to simulate concrete in a concrete truck during transportation to a construction site. All SCC mixtures were mixed in a drum mixer. Polycarboxylate-based high-range water-reducing admixture (PC) and fly ash were incorporated in SCC mixtures. The results showed that both the compressive strength and durability were influenced by fly ash dosage.
Microbially Induced Calcite Precipitation has been brought into focus as a natural cementation mechanism for soils and it is studied for its potential to offer an alternative grouting technique, providing sustainable solutions to geotechnical problems. In this study we focus on the fabric characteristics of bio-cemented sand, obtained after applying a treatment process including multiple injections of bacteria and chemical solutions inducing the formulation of calcium carbonate particles that are responsible for endowing granular geo-materials with cohesion. The cemented sand samples with an improved structure of varying calcite content are subjected to undrained triaxial shearing. Results show an increase in peak strength up to five times with respect to that of the untreated material. The main focus of this study is put on associating the prescribed Calcium Chloride concentration with the yielded precipitation and finally on distinguishing some predominant characteristics of the new structure based on the treatment method adopted.
In this paper the effect of temperature change on one-story reinforced concrete frame buildings allocated in the UAE is studied. Thirty four finite element models with different story heights and slab lengths were developed in ETAB to carry out this study. The effect of temperature change and the variation of the story height and slab length on the top displacement and horizontal reactions were identified in this paper.
Simultaneous mode and wavelength division multiplexing is proposed using integrated asymmetric directional coupler and multimode interference waveguides. The device is compact (6?m x 100?m) and exhibits low insertion loss of 1.2dB and a cross-talk of -18dB.
