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Immobilization of radioactive corrosion products by cold sintering of pure hydroxyapatite
ul Hassan, Muhmood,Iqbal, Sajid,Yun, Jong-Il,Ryu, Ho Jin Elsevier 2019 Journal of hazardous materials Vol.374 No.-
<P><B>Abstract</B></P> <P>An efficient method for the consolidation of cobalt (Co(II)) adsorbed calcium hydroxyapatite was investigated to develop a simplified route for decontamination of the coolant system of nuclear power plants and direct immobilization of as-spent adsorbent. Calcium hydroxyapatite nano-powder synthesized by a wet precipitation method was used as an adsorbent and 94% Co(II) surrogate removal from simulated water was measured. The as-spent adsorbent was sintered at 200 °C, a temperature significantly lower than conventional sintering temperatures (900–1300 °C) for hydroxyapatite, under a uniaxial pressure of 500 MPa for 10 min. The relative density after the cold sintering was >97% and sintered samples displayed good compressive strength (175 MPa). The normalized leaching rate of the Co(II) was measured as per ASTM-C1285 standard and found to be 2.5 × 10<SUP>−5</SUP> g/m<SUP>2</SUP>/day. ANSI/ANS-16.1 test procedure was used to analyze the leachability of the sintered matrices and the measured leaching index value was 6.5. Thus, the use of pure calcium hydroxyapatite nano-powder as adsorbent and its cold sintering offers a mean by which radioactive waste form can be processed in an environment friendly manner.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Very low temperature, binder-free consolidation of calcium hydroxyapatite. </LI> <LI> Cold sintered Co-adsorbed hydroxyapatite presented good leaching resistance. </LI> <LI> Cold sintering of hydroxyapatite can be an energy-efficient processing of waste forms. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Rana, Abu ul Hassan Sarwar,Chang, Seung-Bo,Chae, Hyun Uk,Kim, Hyun-Seok Elsevier 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.729 No.-
<P><B>Abstract</B></P> <P>Previous studies on solution concentration, density, coating time, and annealing temperature of sol-gel ZnO seeds have underrated the growth of ZnO nanostructures. However, these details are quite vital and central to growth of vertically aligned ZnO nanorods (ZNRs). The current study investigates ZNR structure and growth dependence upon solution concentration, thickness, density, diameter, annealing time, annealing temperature, and crystalline quality of sol-gel spin coated ZnO seeds. For growth optimization, we used 0.02, 0.04, and 0.09 M zinc acetate seeds in n-propanol coated two and five times on a p-Si substrate. We found that seed thickness and density depend upon successive coats and the seed solution concentration. The morphology, alignment, density, aspect ratio, crystalline quality, and optical properties of ZNRs are directly related to the seed parameters. The defect centers in seeds and ZNRs are independent of each other. We also studied the electrical characteristics of spin coated seeds, which is a hallmark in the research and development of seed oriented growth of ZnO nanostructures.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Structural, optical, electrical, and morphological properties of different concentration sol-gel ZnO seeds are presented. </LI> <LI> The ZnO nanorod (ZNR) growth depends upon the concentration, thickness, and crystalline quality of seeds. </LI> <LI> The ZNR structural and optical properties confide in the structural and optical properties of seeds. </LI> <LI> The seed layer defect density and carrier concentration are directly proportional to seed solution concentration. </LI> <LI> Annealing temperature and time are of paramount importance in seed layer stability. </LI> </UL> </P>
Naqvi Furqan Ul Hassan,Naqvi Furqan Ul Hassan,Kim Tae Heon,Ahn Chang Won,Hwang Younghun 한국물리학회 2022 Current Applied Physics Vol.44 No.-
Structural and vibrational characteristics of methylammonium(MA) halide perovskite MAPbBr3-xClx single crystals (x = 0–3) were investigated by using powder X-ray diffraction and Raman scattering experiments. The lattice constant in the cubic phase obtained from powder X-ray diffraction peaks at room temperature showed nearly a linear dependence as a function of composition. On the other hand, some of the Raman mode frequencies obtained from single crystals exhibited substantial changes in both frequency shifts and half widths over the investigated composition range. Especially, the MA torsional mode showed a significant change from 325 to 485 cm 1 and mode splitting as Cl was replaced by Br. This mode splitting was more clearly seen at low temperatures reflecting the symmetry lowering of the local structure. The contrast between the linear change in the lattice constant and the substantial change in the vibrational frequencies and half widths of the MA torsional mode in the intermediate composition range indicates the local heterogeneous environment for the MA cations caused by the substitutional disorder.
Hassan, Najam ul,Kim, Yoon-Jae,Han, Byung-Moon,Lee, Jun-Young The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.1
This paper proposes a dc/dc converter for electric vehicle onboard chargers using a secondary resonant tank. To attain soft switching characteristics, such as zero voltage switching, magnetizing inductance has been used at the primary side of the transformer. The leakage inductance of the transformer is used as a resonant inductor on the secondary side to avoid the use of a separate inductor as resonance. The proposed converter is applicable for a wide load range. A 6.6KW prototype has been implemented for a wide range of load variations (250V, 330V, 360V, and 413V). A maximum efficiency of 97.4% is achieved at 413V.
Hassan Aisar Ul,Jadoon Zeeshan Ali Safdar,Kim Jin-Tae,노흥렬 한국물리학회 2023 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.82 No.9
In this study the efects of neighboring transitions through Doppler broadening on electromagnetically induced absorption and transparency of degenerate two-level system in Rb atoms with respect to circular orthogonal polarization confguration (σ+ − σ−) of coupling and probe lasers have been investigated. The dominance of closed Fg = 3 → Fe = 4 of 85Rb (Fg = 2 → Fe = 3 of 87Rb) D2 transition results in the observation of asymmetric and split electromagnetically induced absorptions at all of transitions regardless of the openness or closing of the transitions even in low intensity regime. Slight diferences between the spectra of 85Rb and 87Rb are analyzed by investigating the variation of the spectra of 85Rb with an artifcial increase of the hyperfne splittings and accordingly with a decreasing of the neighboring efects.
Hassan, Rizwan Ul,Jo, Soohwan,Seok, Jongwon World Scientific Publishing Company 2018 Functional materials letters Vol.11 No.2
<P>The feasibility of fabrication of shape memory polymers (SMPs) was investigated using a customized 3-dimensional (3D) printing technique with an excellent resolution that could be less than 100 microns. The thermorheological effects of SMPs were adjusted by contact and non-contact triggering, which led to the respective excellent shape recoveries of 100% and 99.89%. Thermogravimetric analyses of SMPs resulted in a minor weight loss, thereby revealing good thermal stability at higher temperatures. The viscoelastic properties of SMPs were measured using dynamic mechanical analyses, exhibiting increased viscous and elastic characteristics. Mechanical strength, thermal stability and viscoelastic properties, of the two SMPs were compared [di(ethylene) glycol dimethacrylate (DEGDMA) and poly (ethylene glycol) dimethacrylate (PEGDMA)] to investigate the shape memory behavior. This novel 3D printing technique can be used as a promising method for fabricating smart materials with increased accuracy in a cost-effective manner.</P>
Learning-Based Caching in Cloud-Aided Wireless Networks
Tamoor-ul-Hassan, Syed,Samarakoon, Sumudu,Bennis, Mehdi,Latva-aho, Matti,Hong, Choong Seon IEEE 2018 IEEE COMMUNICATIONS LETTERS Vol.22 No.1
<P>This letter studies content caching in cloud-aided wireless networks, where small cell base stations with limited storage are connected to the cloud via limited capacity fronthaul links. By formulating a utility (inverse of service delay) maximization problem, we propose a cache update algorithm based on spatio-temporal traffic demands. To account for the large number of contents, we propose a content clustering algorithm to group similar contents. Subsequently, with the aid of regret learning at small cell base stations and the cloud, each base station caches contents based on the learned content popularity subject to its storage constraints. The performance of the proposed caching algorithm is evaluated for sparse and dense environments, while investigating the tradeoff between global and local class popularity. Simulation results show 15% and 40% gains in the proposed method compared to various baselines.</P>
Najam ul Hassan,Yoon-Jae Kim,Byung-Moon Han,Jun-Young Lee 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.1
This paper proposes a dc/dc converter for electric vehicle onboard chargers using a secondary resonant tank. To attain soft switching characteristics, such as zero voltage switching, magnetizing inductance has been used at the primary side of the transformer. The leakage inductance of the transformer is used as a resonant inductor on the secondary side to avoid the use of a separate inductor as resonance. The proposed converter is applicable for a wide load range. A 6.6KW prototype has been implemented for a wide range of load variations (250V, 330V, 360V, and 413V). A maximum efficiency of 97.4% is achieved at 413V.