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- 검색키워드
- 저자 : Obaid, M. (검색결과 52 건)
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Obaid, M.,Kang, Yesol,Wang, Sungrok,Yoon, Myung-Han,Kim, Chang-Min,Song, Jun-ho,Kim, In S. The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.25
<P>Although forward osmosis (FO) technology is considered to be a sustainable solution for the water and energy shortage, it has not been commercialized yet due to a few factors. Internal concentration polarization (ICP) is one of the most important barriers preventing the commercialization of the technology. To overcome the ICP obstacle, novel high-performance thin-film nanocomposite (TFN) membranes were successfully fabricated <I>via</I> interfacial polymerization on robust freestanding graphene oxide (GO) incorporated polyvinylidene fluoride (PVDF) nanofiber substrates. Compared to the pristine PVDF nanofiber substrate, the incorporation of GO (ranging from 0.1-15 wt%) significantly alters the chemical structure, porosity, wettability, morphology, and mechanical properties of the substrate, leading to an enhancement in the TFN membrane performance. The results showed that TFN5 (containing 5% GO) membrane possesses the lowest structural parameter of 85.5 μm (one of the best values in the literature), indicating a low internal concentration polarization (ICP) effect, resulting in a remarkably heightened water permeability (<I>A</I>; 2.96 L m<SUP>−2</SUP> h<SUP>−1</SUP> bar<SUP>−1</SUP>, enhanced by 167% compared to TFC). As a result, the membrane achieved the highest FO water flux at all draw solution concentrations (0.5-2 M NaCl), and the maximum FO water flux was 80.9 L m<SUP>−2</SUP> h<SUP>−1</SUP> (LMH) with a comparable specific salt flux (<I>J</I>s/<I>J</I>v) of 0.41 g L<SUP>−1</SUP> in the active layer facing the deionized feed water (AL-FS) when 2 M NaCl was applied as a draw solution. Interestingly, TFN5 was found to be the strongest material, with outstanding flexibility and strength over that of the TFC membrane. Furthermore, it showed high stability and durability during long-term FO operation. More importantly, the interaction mechanism between PVDF and GO was proposed schematically. Overall, the obtained results show highly efficient and promising TFN membranes that may overcome the drawbacks of the aforementioned FO membranes.</P>
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Obaid Ur Rahman,Jeena Kim,Caroline Mahon,Musharraf Jelani,강창수 한국유전학회 2021 Genes & Genomics Vol.43 No.5
Background Amyloidosis cutis dyschromica (ACD) is a rare variant of cutaneous amyloidosis. This disorder often clusters in families, and it has been suggested that genetic factors might be involved in its development. Objective To identify the genetic causes of ACD, we recruited a consanguineous Pakistani family with multiple cases of ACD that display a recessive mode of inheritance. Methods We performed whole-exome sequencing of samples from 7 members of this family, followed by bioinformatic and in silico analyses to identify the causative variant. For the replication study, we recruited a British family with Pakistani ancestry, and sequenced all exons of glycoprotein non-metastatic melanoma protein b (GPNMB) to identify mutations. We also investigated efects of the mutations on the stability of the GPNMB protein using the I-TASSER three-dimensional modeling tool. Results We found a novel homozygous mutation, p.Gly363Val (c.1088 G>T), in GPNMB in all afected cases. In a replication study, another homozygous missense mutation in GPNMB, pIle174Met (c.522 C>G), was carried by the afected son. The two mutations were not observed in our in-house data set comprising 217 healthy Pakistani individuals or in The Genome Aggregation Database. Our structural modeling of GPNMB suggested that p.Gly363Val enhanced its stability, whereas p.Ile174Met caused instability. Conclusions This study reports two novel missense mutations in two Pakistani families that cause ACD. The mutations appear to infuence GPNMB stability, as revealed by protein modeling.
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Obaid Aldosari,Luciano A. Garcia Rodriguez,David Carballo Rojas,Juan Carlos Balda 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
The main objective of this research work is to develop a new low-cost isolated three-level ac-dc power converter topology that is suitable for applications having high input ac voltages and high output currents; for example, hybrid (ac-dc) microgrids or offshore wind farms. Existing three-level converter topologies convert ac power to dc power while maintaining requirements set by international standards for power conversion. These types of converters have significant conduction losses due to high currents in the low-voltage side and high costs, particularly when using several devices in series or in parallel to achieve high-voltage and high-power levels. The proposed topology replaces the conventional three-level converters in the low-voltage side by only two controlled devices and four diodes while still maintaining the basic functionality of a three-level converter. Simulation results for a 87.5-kW case study and experimental results on a 250-W scale-down prototype demonstrate the feasibility of the proposed ideas.
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Longitudinal and transverse form factors from 65Cu and 71Ga nuclei
Obaid Sarah M.,Majeed Fouad A. 한국물리학회 2023 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.82 No.4
In the present work, the inelastic electron scattering for longitudinal and transverse form factors of 65Cu and 71Ga nuclei lies in the fp-shell region are studied in the framework of the shell model. The calculation is performed in the (1f5/2, 2p3/2, 2p1/2, 1g9/2) model space using jun45 efective interaction. The wavefunctions employed to conduct the shell model calculations are extracted from the jun45 efective interaction for these nuclei with the jj44 shell model space and (Sk35−Skzs ∗) residual interaction to evaluate the interactions matrix element between initial and fnal states. The efective charges used to account for the core-polarization (CP) efect are created using calculations of microscopic perturbations that include intermediate one-particle, one-hole excitation from the core and the model space (MS) orbits into all upper orbits with nℏ� excitations following the same approach done in [Radhi et al. in Euro. Phys. J. A 50:1–9, 2014]. To account for the (CP) efects contribution, the inelastic form factor is obtained by employing the shape of Tassie and Bohr–Mottelson models with appropriate proton and neutron efective charges. The calculated form factors were compared with available experimental data.
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Obaid, M.,Ghouri, Zafar Khan,Fadali, Olfat A.,Khalil, Khalil Abdelrazek,Almajid, Abdulhakim A.,Barakat, Nasser A. M. American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.7
<P>Novel amorphous silica nanoparticle-incorporated poly(vinylidine fluoride) electrospun nanofiber mats are introduced as effective membranes for forward osmosis desalination technology. The influence of the inorganic nanoparticle content on water flux and salt rejection was investigated by preparing electrospun membranes with 0, 0.5, 1, 2, and 5 wt % SiO2 nanoparticles. A laboratory-scale forward osmosis cell was utilized to validate the performance of the introduced membranes using fresh water as a feed and different brines as draw solution (0.5, 1, 1.5, and 2 M NaCl). The results indicated that the membrane embedding 0.5 wt % displays constant salt rejection of 99.7% and water flux of 83 L m(-2) h(-1) with 2 M NaCl draw solution. Moreover, this formulation displayed the lowest structural parameter (S = 29.7 mu m), which represents approximately 69% reduction compared to the pristine membrane. Moreover, this study emphasizes the capability of the electrospinning process in synthesizing effective membranes as the observed water flux and average salt rejection of the pristine poly(vinylidine fluoride) membrane was 32 L m(-2) h(-1) (at 2 M NaCl draw solution) and 99%, respectively. On the other hand, increasing the inorganic nanoparticles to 5 wt % showed negative influence on the salt rejection as the observed salt flux was 1651 mol m(-2) h(-1) Besides the aforementioned distinct performance, studies of the mechanical properties, porosity, and wettability concluded that the introduced membranes are effective for forward osmosis desalination technology.</P>
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Obaid, M.,Yang, Euntae,Kang, Dong-Hee,Yoon, Myung-Han,Kim, In S. Elsevier 2018 Separation and purification technology Vol.200 No.-
<P><B>Abstract</B></P> <P>A superoleophobic underwater modified electrospun membrane is produced via a novel effective modification method, to overcome the hydrophobicity and fouling propensity of the electrospun polysulfone (PSf) membrane. In which the fabricated PSf electrospun membranes were immersed in different NaOH concentrations (0, 0.1, 0.5, and 1 M) at different temperatures (25, 50, 75, and 100 °C) for different time (1, 3, 5, 7 h) to produce 64 modified membranes. Based on the characterization of the modified membranes, the best-modified membrane was chosen and was investigated in the oil-water separation system.</P> <P>More importantly, the best-modified membrane (M64) exhibits underwater superoleophobic feature and it could effectively separate soybean oil and hexane-water mixtures with a superior water flux of 11,865 and 14,016 LMH after the 5th cycle under a gravity-driven process, respectively. Moreover, the membrane possesses remarkable oil-water separation efficiency with more than 99.99% of oil rejection, where soybean oil and hexane content in the filtrate after the 5th cycle were less than 3 and 1 ppm, respectively, which is lower than the acceptable limit of 10 ppm. Also, the modified membrane exhibited antifouling properties with a water flux recovery ratio of 94 and 96.8% after the 5th filtration cycles of soybean oil and hexane-water mixtures. Overall, this study introduces a simple and effective method to overcome the hydrophobicity of the PSf electrospun membrane and enhance the antifouling property.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Underwater superoleophobic PSf electrospun membrane is introduced. </LI> <LI> The effective modified electrospun PSf membrane attained ultrafast water flux. </LI> <LI> The modified membrane exhibited improved antifouling properties (94% FRR). </LI> <LI> Excellent oil rejection with more than 99.99% was achieved. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Stable and effective super-hydrophilic polysulfone nanofiber mats for oil/water separation
Obaid, M.,Barakat, Nasser A.M.,Fadali, Olfat A.,Al-Meer, Saeed,Elsaid, Khalid,Khalil, Khalil Abdelrazek Elsevier 2015 Polymer Vol.72 No.-
<P><B>Abstract</B></P> <P>Hydrophobicity of polysulfone is the main constraint facing wide application in the most important field; water treatment, although this polymer shows promising characteristics to be used in different separation technologies. In this study, super-hydrophilic polysulfone nanofiber mats are introduced using novel modifications. The introduced nanofibers were synthesized by electrospinning of polysulfone/NaOH/DMF electrospun solution. The prepared electrospun nanofibers have been activated by deposition of a polyamide layer using interfacial polymerization (IP) reaction between m-phenylenediamine and 1,3,5-benzenetricarbonyl chloride. Three different heat treatment methodologies were investigated to enhance the characteristics of the activated nanofiber mats; normal drying at 70 °C, and soaking in boiled water followed by either normal drying at 70 °C or storing in the water. Investigation of the mechanical properties indicated that incorporation of NaOH improves the tensile stress by 40% compared to the pristine polysulfone nanofibers. Interestingly, treatment of the activated nanofiber mats in the boiled water followed by storing in water led to produce super-hydrophilic mats with water contact angle of 3° due to enhancing the IP reaction on the surface of the individual nanofibers. In oil/water separation process, the proposed heat treatment for the modified nanofiber mats resulted in increase the water flux from 8 to 12.21 m<SUP>3</SUP>/m<SUP>2</SUP> day with oil rejection of 99.976%.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Super-hydrophilic membrane based on PSF nanofibers is introduced. </LI> <LI> The membrane was modified using simple and effective heat treatment process. </LI> <LI> The corresponding water flux is very high; 12.21 m<SUP>3</SUP>/m<SUP>2</SUP> day. </LI> <LI> The fabrication process is simple, cheap and applicable. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Foam concrete made with micro and nano silica sand: Pore structure and properties
Obaid, Hawaa A.,Hilal, Ameer A. Techno-Press 2021 Advances in concrete construction Vol.12 No.3
A study has been undertaken to investigate the possibility of using filler as fine aggregate, with different fineness and grading, instead of a conventional fine sand used in producing foam concrete. A conventional sand was replaced by micro silica sand and a comparison has been done to examine the pore structure and properties of investigated foam concrete mixes. Two ways were adopted to incorporate the nano silica sand into the mixture: with part of mixing water and with pre-formed foam bubbles. Compared to conventional foam concrete, it was found that using micro silica sand helped in improving strength (169%), reducing absorbed water (38%) and reducing shrinkage (40%) by enhancing both cement paste microstructure and pore structure. This pore structure enhancement was achieved by reducing pores merging leading to making a narrow pore size distribution and more circular pores with large spaces between them. On the other hand, increasing fineness of normal sand and using nano silica sand resulted in less enhancing in foam concrete properties compared with using the silica sand as its own (at micro level). It was noticed that incorporating the nano particles into mixture with foam bubbles was more effective than the conventional way; with mixing water.
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