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OPTImIZATION OF THe SYNTHeSIS OF ACRYLAmIDe HYDROGeL BY γ-RAY IRRADIATION

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Chinese Journal of Polymer Science 2004年第3期22卷 253-258页

作者： m.A. Chowdhury m.m. Alam m.F. mina F. Akhtar S.e. Kabir Department of Chemistry Faculty of Science Jahangir Nagar University Dhaka BangladeshNRCD INST AERE GPO Box-3787 Dhaka Bangladesh NRCD INST AERE GPO Box-3787 Dhaka Bangladesh NRCD INST AERE GPO Box-3787 Dhaka Bangladesh Department of Chemistry Faculty of Science Jahangir Nagar University Dhaka Bangladesh

Hydrogels have been synthesized from 10%, 20%, 30%, 40%, 50% and 60% aqueous solutions of acrylamide monomer by gamma radiation employing doses in the range of 0.2-30 kGy from a Co-60 source. The effect of solution concentration, γ-ray dose, pH and time was studied in order to observe the optimizing conditions in the characterization of hydrogels. Gel fraction increases with dose for all concentrations indicating hundred-percentage conversion of gel at doses 5 kGy for homogenous solutions in the range of 20%-50% concentration. On the other hand, 10% solution provides conversion less than 86% even at 30 kGy, whereas 60% monomer makes an inhomogeneous solution which stile gives about 100% gel fraction. Swelling of hydrogels under water with respect to time varies with both the doses and concentrations due to the change of crosslinking density in the gels. The maximum volume change of hydrogels during swelling and water desorption mainly occurs within 24 h. Swelling is also enhanced with the rise of pH due to change of ionic content of the solvent. Considering the amount of gel fraction and the properties of hydrogel, the samples prepared from 20% solution at 5 kGy show better results. moreover, the effect of bacteria on hydrogel was found to be nil, suggesting a prohibition of growth of microorganism in it.

关键词： Hydrogel Acrylamide γ-radiation Swelling microorganism

Holmium Oxide Film as a Saturable Absorber for 2μm Q-Switched Fiber Laser

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Chinese Physics Letters 2017年第5期34卷 48-51页

作者： m.F.A.Rahman m.F.m.Rusdi m.Q.Lokman m.B.H.mahyuddin A.A.Latiff A.H.A.Rosol K.Dimyati S.W.Harun Department of electrical engineering University of Malaya Kuala Lumpur 50603 Malaysia Photonics Research Centre University of Malaya Kuala Lumpur 50603 Malaysia Faculty of electrical engineering University Teknologi Mara Shah Alam 40450 Malaysia

This work reports on the use of the holmium oxide （Ho2O3） polymer film as a saturable absorber （SA） for generating stable Q-switching pulses operating in a 2μm region in a thulium-doped fiber laser cavity. The SA is prepared by diluting a commercial Ho3O2 powder and then mixing it with polyvinyI alcohol （PVA） solution to form a Ho2O3-PVA film. A tiny part of the film about 1mm×1 mm in size is sandwiched between two fiber ferrules with the help of index matching gel. When incorporated in a laser cavity driven by a 1552-nm pump, stable Q-switching pulses are observed at 1955nm within the pump power range of 363 491 roW. As the pmnp power increases within this range, the repetition rate rises from 26 kHz to 39 kHz, as the pulse width drops from 4.22μs to 2.57μs. The laser operates with a signal-to-noise ratio of 47dB, and the maximum output power and the pulse energy obtained are 2.67mW and 69ng, respectively. Our results successfully demonstrate that the Ho2O3 film can be used as a passive SA to generate a 2μm pulse laser.

关键词： m Q-Switched Fiber Laser SA FeSem

mathematical modeling for dynamic stability of sandwich beam with variable mechanical properties of core

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Applied mathematics and mechanics(english edition) 2016年第10期37卷 1361-1374页

作者： m.GRYGOROWICZ e.mAGNUCKA-BLANDZI Institute of Applied mechanics Poznan University of Technology Institute of mathematics Poznan University of Technology

The paper is devoted to mathematical modelling of static and dynamic stability of a simply supported three-layered beam with a metal foam core. mechanical properties of the core vary along the vertical direction. The field of displacements is for- mulated using the classical broken line hypothesis and the proposed nonlinear hypothesis that generalizes the classical one. Using both hypotheses, the strains are determined as well as the stresses of each layer. The kinetic energy, the elastic strain energy, and the work of load are also determined. The system of equations of motion is derived using Hamilton＇s principle. Finally, the system of three equations is reduced to one equation of motion, in particular, the mathieu equation. The Bubnov-Galerkin method is used to solve the system of equations of motion, and the Runge-Kutta method is used to solve the second-order differential equation. Numerical calculations are done for the chosen family of beams. The critical loads, unstable regions, angular frequencies of the beam, and the static and dynamic equilibrium paths are calculated analytically and verified numerically. The results of this study are presented in the forms of figures and tables.

关键词： mathematical modelling dynamic stability metal foam core with variable mechanical property static and dynamic equilibrium path angular frequency

Analytical solution for laminar flow through leaky tube

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Applied mathematics and mechanics(english edition) 2011年第1期32卷 69-74页

作者： m.GORJI m.ALIPANAH m.SHATeRI e.FARNAD Department of mechanical engineering Babol University of Technology Water and Westwater Company

The laminar flow through a leaky tube is investigated, and the momentum and conservation of energy equations are solved analytically. By using the Hagen-Poiseuille velocity profile and defining unknown functions for the axial and radial velocity compo- nents, the pressure and mass transfer equations are obtained, and their profiles are plotted according to different parameters. The results indicate that the axial velocity, the radial velocity, the mass transfer parameter, and the pressure in the tube decrease as the fluid moves along the tube.

关键词： leaky tube permeability mass transfer laminar flow analytical solution

Seismic assessment of unanchored steel storage tanks by endurance time method

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earthquake engineering and engineering Vibration 2011年第4期10卷 591-603页

作者： m. Alembagheri H.e. estekanchi Department of Civil engineering Sharif University of Technology (SUT)

Liquid storage tanks are essential structures that are often located in residential and industrial areas; thus an assessment of their seismic performance is an important engineering issue. In this paper, the seismic response ofunanchored steel liquid storage tanks is investigated using the endurance time （eT） dynamic analysis procedure and com.a.e. to responses obtained for anchored tanks under actual ground motions and intensifying eT records. In most cases, the results from ground motions are properly obtained with negligible differences using eT records. It is observed that uplifting of the tank base, which is closely related to the tank aspect ratio, has the greatest significance in the responses of the tank and can be predicted with reasonable accuracy by using currently available eT records.

关键词： steel liquid storage tanks endurance time method seismic assessment intensifying dynamic excitation tank base uplifting

modelling, parameter estimation and assessment of partial shading conditions of photovoltaic modules

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Journal of modern Power Systems and Clean energy 2019年第1期7卷 55-64页

作者： S.LYDeN m.e.HAQUe School of engineering University of Tasmania School of engineering Deakin University

This paper proposes a method for assessing the effect that different features of partial shading conditions(PSC) may have on the operation of a photovoltaic(PV)*** studies, based on an experimentally validated model of a PV system, are used to assess the influence of *** classifications of PSC are defined based on the timescale of their influence on the irradiance experienced by the PV module and the relative location of the voltage at which the global maximum power point occurs is *** case studies are presented to illustrate the application of the proposed PSC assessment *** results have implications for the design of future maximum power point tracking methods.

关键词： Photovoltaic modelling Partial shading maximum power point

effect of Y^(3+), Gd^(3+) and La^(3+) dopant ions on structural, optical and electrical properties of o-mullite nanoparticles

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Journal of Rare earths 2014年第1期32卷 37-42页

作者： m.m.S.Sanad m.m.Rashad e.A.Abdel-Aal m.F.el-Shahat K.Powers Central metallurgical R & D Institute Particle engineering Research Center University of Florida Faculty of Science Ain Shams University

Dielectric ceramics of m（x）Al6（1-x）Si2O13 doped mullite were synthesized via co-precipitation technique. The X-ray diffrac-tion profiles revealed that these nanoparticles were crystallized well and the volume of mullite unit cell was increased as a function of the ionic radius of dopant ion. Tem images showed regular orthorhombic crystal morphology for the pure mullite sample. meanwhile, the doped samples exhibited slightly distorted crystal morphology of larger particle sizes. DSC thermograms evinced that the exo-thermic peak temperature of mullite was shifted to the lower value with m3＋ion insertion. The photoluminescence spectra were stud-ied for mullite samples, and it was found that the intensity of the emission spectra was affected by the m3＋ion type. It was found that, Y3＋doped mullite achieved the minimum dielectric loss value of 0.01 in the radio wave frequency region （1 mHz）. meanwhile, Gd3＋doped mullite achieved the minimum dielectric loss value of 0.09 in the microwave frequency region （1 GHz）.

关键词： rare earths doped mullite photoluminescence crystallization temperature dielectric ceramics

Sintering behaviour of feldspar and influence of electric charge effects

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International Journal of minerals,metallurgy and materials 2011年第2期18卷 132-137页

作者： W.Gallala m.e.Gaied earth Sciences Department Faculty of Sciences GabesCité RiadhZirig

The characterization of feldspar for electric porcelain and the behaviour of these materials after heating at 1230°C were studied. X-ray diffraction （XRD） and scanning electronic microscopy （Sem） were used to identify the present phases and the densification level. Feldspar sand was treated by flotation. The floated feldspar is constituted by microcline, quartz, and minor amounts of albite. The micro-structure of sintered feldspar at 1230°C is essentially vitreous with open microporosities. The dielectrical properties of composites were characterized by using the induced courant method （ICm）, which indicates that the charge trapping capacity depends on the mineralogical and chemical composition of feldspar.

关键词： potash ore treatment feldspar sintering microstructure dielectric properties

exploring tree diversity and stand structure of savanna woodlands in southeastern Sudan

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Journal of Arid Land 2020年第4期12卷 609-617页

作者： Ahmed m m HASOBA Ahmed A H SIDDIG Yousif e YAGOUB Faculty of Forest Sciences and Technology University of GeziraMadani 22212Sudan Faculty of Forestry University of KhartoumKhartoum North 13314Sudan Department of environmental Conservation University of Massachusetts AmherstAmherst 01003USA

Savanna woodlands in Sudan host great biodiversity, provide a plethora of ecosystem goods and services to local communities, and sustain numerous ecological functions. Although the importance of the Acacia trees in these areas is well known, up-to-date information about these woodlands' diversity is limited and changes in their woody vegetation composition, density, diversity and relative frequency are not monitored over time. This study explored tree diversity and stand stage structure in Nuara Reserved Forest, a typical savanna woodland ecosystem in southeastern Sudan. A total of 638 circular sample plots(1000 m^2 for each) were established using a systematic sampling grid method. The distance between plots was 200 m. In each plot, all living trees with diameter at breast height(DBH) ≥5.00 cm were identified and counted, and their DBH values were recorded. From these data, tree composition, diversity, density and stage structure were assessed. There were 12,259 individual trees representing four species(Acacia seyal, Balanites aegyptiaca, Acacia Senegal and Acacia mellifera) that belong to two families. The dominant species was Acacia seyal. Average tree density was 191 trees/hm^2 and the Shannon-Weiner index for trees diversity was 0.204. Overall, young trees comprised 86.30% of the forest. The state of tree richness and density in the study area was low com.a.e. to other similar environments in the region and around the world. We recommended adoption of a proper management system that includes monitoring of woody vegetation diversity in this forest, and management actions to enhance tree diversity and sustain ecosystem services to local communities. In addition to care for the dominant Acacia seyal stands, more attention and conservation should be devoted to reestablishing Acacia senegal and Acacia mellifera trees because of their high ecological and economic values for local communities.

关键词： species diversity stand structure savanna woodland ecosystem forest monitoring forest management ecosystem services Nuara Reserved Forest