| 1. |
- Hossain, Mohammad, et al.
(författare)
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Strategic approach for up-scaling safe water access considering hydrogeological suitability and social mapping in Matlab, southeastern Bangladesh
- 2013
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Konferensbidrag (refereegranskat)abstract
- In recent years, there has been a significant progress in understanding the source and mobilization process, sediment-water interactions, and distributions of arsenic in groundwater environment in Bangladesh. However, the impacts of arsenic mitigation are still very limited. A social survey conducted during 2009-2011 in 96 villages in Matlab revealed that only 18% of total tubewells provide As-safe water. The safe water access also varied between 0 and 90 percent in the region due to lack of knowledge about the local geology and unplanned tubewell development. SASMIT, an initiative of KTH-International Groundwater Arsenic Research Group has developed a method for safe tubewell installation considering hydrogeological suitability, safe water access and other relevant social and demographic information into account.Piezometers installed at 15 locations over an area of 410 km2, using local boring techniques allowed to delineate the hydrostratigraphy, characterize the aquifers in terms of sediment characteristics, water chemistry and hydraulic head distribution, which ultimately led to the identification of the suitable aquifers for tapping safe water. The piezometer locations with safe drinking water quality were then targeted for safe well installation based on the determination of safe buffer distances in a cluster of a few villages (mouzas). Social mapping of all the villages within the mauzas were done using GIS to evaluate the availability of safe water options for a cluster of households (bari). For safe well installations, priority was given to regions with safe water access, greater number of beneficiaries especially in poor households, and easy access to the site from a cluster of households. Through this approach, it was thus possible to make 95% of the newly installed wells As-safe thus scaled up the safe water access upto 40% in some mauzas. Thus the as a strategy to improve safe water access, the SASMIT study recommends investigating the hydrogeological suitability through installation of few piezometers with a minimum effort and based on the results the implementation plan can be made using GIS based social mappings for relatively uniform distribution and to maximize the safe water access.
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| 2. |
- Hossain, M., et al.
(författare)
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Potentiality of intermediate depth aquifer as a source of arsenic and manganese safe tubewells in Bangladesh
- 2012
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Ingår i: Understanding the Geological and Medical Interface of Arsenic, As 2012 - 4th International Congress: Arsenic in the Environment. - : Taylor & Francis Group. - 9780415637633 ; , s. 71-73
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Konferensbidrag (refereegranskat)abstract
- Shallow tubewells excepting those installed in red/off-white sediments are mostly contaminated with high arsenic. Social survey conducted in 96 villages of Matlab, a worse-affected area of Bangladesh, reveals that only 18% of tubewells provide As-safe water. In such a condition, high Manganese in many wells is found to be an additional problem. Based on monitoring in depth-specific piezometers, drinking water wells were installed in intermediate depth aquifer around 120 m. Ninety percent of the wells installed in light grey medium sand, had arsenic concentrations below the Bangladesh standard of 50 ÎŒg/L and manganese was within the previous WHO guideline (0.4 mg/L). Availability of similar sand over this depth range could be targeted by local drillers to tap safe water at a reasonable cost. Replication trials and periodical monitoring are emphasized for validation and sustainability.
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| 3. |
- Kibria, M. G., et al.
(författare)
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Hydrogeochemistry and microbial geochemistry on different depth aquifer sediments from Matlab, Bangladesh
- 2014
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Ingår i: One Century of the Discovery of Arsenicosis in Latin America (1914-2014). - : CRC Press. - 9781138001411 ; , s. 101-103
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Konferensbidrag (refereegranskat)abstract
- Arsenic (As) poses the greatest hazard towards drinking water quality in Bangladesh. Tubewell drinking water is one of the main sources for household based water options in rural Bangladesh. Our study area is in Matlab Upazila, in Bangladesh. The overall objective of this research and the SASMIT project is to develop a community based initiative for sustainable As mitigation by developing a sediment color based tool for the local drillers prioritizing on the hydrogeological and biogeochemical investigations. For this purpose we analyzed different depth colored sediments and water for find out the sustainable low Arsenic contaminated aquifer.
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| 4. |
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| 5. |
- Månsson, Kristofer, 1983-, et al.
(författare)
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A new liu type of estimator for the restricted SUR estimator
- 2019
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Ingår i: Journal of Modern Applied Statistical Methods. - : Wayne State University Press. - 1538-9472. ; 18:1
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Tidskriftsartikel (refereegranskat)abstract
- A new Liu type of estimator for the seemingly unrelated regression (SUR) models is proposed that may be used when estimating the parameters vector in the presence of multicollinearity if the it is suspected to belong to a linear subspace. The dispersion matrices and the mean squared error (MSE) are derived. The new estimator may have a lower MSE than the traditional estimators. It was shown using simulation techniques the new shrinkage estimator outperforms the commonly used estimators in the presence of multicollinearity.
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| 6. |
- Kibria, G., et al.
(författare)
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A rapid, automated surface protein profiling of single circulating exosomes in human blood
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Circulating exosomes provide a promising approach to assess novel and dynamic biomarkers in human disease, due to their stability, accessibility and representation of molecules from source cells. However, this potential has been stymied by lack of approaches for molecular profiling of individual exosomes, which have a diameter of 30-150 nm. Here we report a rapid analysis approach to evaluate heterogeneous surface protein expression in single circulating exosomes from human blood. Our studies show a differential CD47 expression in blood-derived individual circulating exosomes that is correlated with breast cancer status, demonstrating a great potential of individual exosome profiles in biomarker discovery. The sensitive and high throughput platform of single exosome analysis can also be applied to characterizing exosomes derived from other patient fluids.
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| 7. |
- Kibria, M.G., et al.
(författare)
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Arsenic mitigation by developing a tool based on gray and brown sediment solid phase characterization
- 2013
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Konferensbidrag (refereegranskat)abstract
- Arsenic (As) poses the greatest hazard towards drinking water quality in Bangladesh. Tubewell drinking water is one of the main sources for household based water options in rural Bangladesh. Our study area is in Matlab Upazila, in Bangladesh. The local drillers in this area are the only ones who have been utilized by the community to identify safe aquifer depths. The overall objective of this and the SASMIT project is to develop a community based initiative for sustainable As mitigation by developing a sediment color based tool for the local drillers prioritizing on the hydrogeological and geochemical investigations as to (a) why red/brown to off-white sediments produces As-safe water but contains high Mn; (b) as to why light gray sediment produce low As and Mn free water; and (c) why dark gray sediments produce high As bearing water. Shallow tubewells excepting those installed within off-white sediments are mostly contaminated with high As. High Mn in many wells is also an additional problem in some shallow aquifer depths. In our field studies we find the wells installed within light grey medium sand the As concentration was found below 50μg/L and Mn is within WHO guideline value of 0.4 mg/L.This study focuses on the adsorption behavior of oxidized reddish-red-brown sediments from Matlab region, and their capacity to attenuate As. Sediment extractions indicate a relatively low amount of As in the oxidized sediments. Reductive dissolution of Fe(III)-oxyhydroxides and release of its adsorbed As is considered to be the principal mechanism responsible for mobilization of As. Groundwater abstracted from oxidized reddish sediments, in contrast to reducing grayish sediments, contains significantly lower amount of dissolved As and can be a source of safe water. This study describes the lithofacies, mineralogy and results of adsorption experiments on the sediments within ~85m depth and establishes a relationship between aqueous and solid phase geochemistry along these intermediate depths of the aquifer.Core samples have been analyzed by petrographic microscopy, microtopography and distribution of elements within sediment grains by FESEM-EDX and clay and bulk mineralogy by XRD. Synchrotron aided μXANES and μXRD studies conducted for solid state As speciation (As3+ and As5+) in different depth core samples. The projected outcome is to incorporate detailed sediment characteristics of the different aquifers including all possible color variations available in the exploited intermediate depths within Matlab. This study would have a wider implication towards a broader scale regional remediation project that incorporates the enquiry of efficiency of sediment color as a simple and easy tool for identifying safe aquifers in major As risk prone areas. Knowing sediments more accurately would also enrich and strengthen the field based tools for identifying As-safe and As-Mn safe aquifers for tubewell installation.
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| 8. |
- Lei, L., et al.
(författare)
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Beam Illumination Pattern Design in Satellite Networks : Learning and Optimization for Efficient Beam Hopping
- 2020
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Ingår i: IEEE Access. - : Institute of Electrical and Electronics Engineers (IEEE). - 2169-3536. ; 8, s. 136655-136667
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Tidskriftsartikel (refereegranskat)abstract
- Beam hopping (BH) is considered to provide a high level of flexibility to manage irregular and time-varying traffic requests in future multi-beam satellite systems. In BH optimization, adopting conventional iterative heuristics may have their own limitations in providing timely solutions, and directly using data-driven technique to approximate optimization variables may lead to constraint violation and degraded performance. In this paper, we explore a combined learning-and-optimization (LO) approach to provide an efficient, feasible, and near-optimal solution. The investigations are from the following aspects: 1) Integration of BH optimization and learning techniques; 2) Features to be learned in BH design; 3) How to address the feasibility issue incurred by machine learning. We provide numerical results and analysis to show that the learning component in LO significantly accelerates the procedure of identifying promising BH patterns, resulting in reduced computing time from seconds/minutes to milliseconds level. The identified learning feature enables high accuracy in predictions. In addition, the optimization component in LO guarantees the solution's feasibility and improves the overall performance with around 5% gap to the optimum.
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| 9. |
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| 10. |
- Lukman, A. F., et al.
(författare)
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A new estimator for the multicollinear Poisson regression model : simulation and application
- 2021
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- The maximum likelihood estimator (MLE) suffers from the instability problem in the presence of multicollinearity for a Poisson regression model (PRM). In this study, we propose a new estimator with some biasing parameters to estimate the regression coefficients for the PRM when there is multicollinearity problem. Some simulation experiments are conducted to compare the estimators' performance by using the mean squared error (MSE) criterion. For illustration purposes, aircraft damage data has been analyzed. The simulation results and the real-life application evidenced that the proposed estimator performs better than the rest of the estimators.
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