检索结果-南通市图书馆

Chinese Journal of Polymer Science 2014年第5期32卷 640-650页

作者： Tanissara Pinijmontree Visit Vao-soongnern Laboratory of Computational and Applied Polymer Science (LCAPS) School of Chemistry Institute of Science Suranaree University of Technology

The conformational and dynamic properties of polypropylene （PP） for both pure melts and blends with different chain tacticity were investigated by Monte Carlo simulation of isotactic （iPP）, atactic （aPP） and syndiotactic （sPP） polypropylenes. The simulation of coarse-grained PP models was performed on a high coordination lattice incorporating short- and long-range intramolecular interactions from the rotational isomeric state （RIS） model and Lennard-Jones （LJ） potential function of propane pairs, respectively. The dynamics of chains in binary PP/PP mixture were investigated with the composition of C150H302 with different chain taciticity. The diffusion rates of PP with different stereochemistry are generally in the order as： iPP 〉 aPP 〉〉 sPP. For PP/PP blends with 50：50 wt% binary mixtures, immiscibility was observed when sPP was introduced into the mixtures. The diffusion rate of iPP and aPP became slower after mixing, while sPP diffuses significantly faster in the binary mixtures. The mobility of PP chains depends on both intramolecular （molecular size and chain stiffness） and intermolecular （chain packing） interactions. The effect of intramolecular contribution is greater than that of intermolecular contribution for iPP and aPP chains in binary mixtures. For sPP chain, intermolecular interaction has greater influence on the dynamics than intramolecular contribution.

关键词： Binary blends of PP with different stereochemical sequences Dynamics Tacticity effect Monte Carlo Simulation.

Electrostatic Nonlinear Structures in Dissipative Electron-Positron-Ion Quantum Plasmas

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2008年第12期25卷 4329-4332页

作者： S. A. Khan Q. Haque Department of Physics COMSATS Institute of Information Technology Islamabad Pakistan and Department of Physics Government College Bagh 12500 AJK Pakistan Theoretical Plasma Physics Division PINSTECH P. O. Nilore Islamabad Pakistan

Low frequency （in comparison to ion plasma frequency） ion-acoustic shocks and solitons in superdense electronpositron-ion quantum plasmas are studied. The quantum hydrodynamic model is used incorporating quantum Bohm forces and Fermi-Dirac statistical corrections to derive the deformed Korteweg de Vries-Burgers （dKdVB） equation in weakly nonlinear limit. The travelling wave solution of dKdVB equation is presented and results are discussed in different limits. It is found that shock height increases with increase of quantum pressure, positron concentration and dissipation. Further, it is seen that the width of soliton decreases with increase of quantum pressure

关键词： Nonlinear Structure Ion Quantum Plasmas

Interactions of Cationic Surfactant Cetyl-trimethyl ammonium bromide with Ammonium nitrate:Surface and Thermodynamic Studies

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Physics 2021年第4期34卷 480-486,I0003,I0004页

作者： Noor Rehman Zia Ul Haq Hidayat Ullah Inamullah Mian Xian Li Department of Chemistry Shaheed BB UniversitySheringalDir(Upper)18050Pakistan Department of Chemistry Gomal UniversityD.I.Khan 27100Pakistan Key Laboratory of Coal Clean Conversion and Chemical Process Autonomous Region College of Chemistry and Chemical EngineeringXinjiang UniversityUrumqi 830000China

The study of interactions between surfactant and salt in aqueous solutions has attracted significant interest in recent years because of their widespread applications and relatively complex *** work reports the systematic study of surface phenomenon and self-aggregation behavior of cationic surfactant cetyltrimethyl ammonium bromide(CTAB)with ammonium nitrate(NH_(4)NO_(3))*** and thermodynamic properties of cationic surfactant CTAB with NH_(4)NO_(3)were investigated at different temperatures using different techniques such as conductometry and surface *** surface tension measurement was carried out to find out the critical micelle concentration,free energy of adsorption,free energy of micellization,minimum area per molecule,and surface excess *** study reveals that the process of micellization is spontaneous and exothermic in *** measurement was carried out to determine critical micelle concentration,degree of ionization and degree of counter ion *** of NH_(4)NO_(3)to the surfactant solutions increase the values of degree of ionization and degree of counter ion binding,although it lowers the values of critical micelle concentration showing that the process of micellization is more favorable and *** study is very helpful to develop better understanding about interaction between electrolyte and surfactant,which are used in many applications and in different processes(e.g.,pharmaceutical,industrial foaming,drug solubilization,oil recovery,and medium for metal nanoparticle formation).

关键词： Surface tension Conductivity NH_(4)NO_(3)salt Cetyl-trimethyl ammonium bromide surfactant

Synthesis of Nanostructured Mg-Ni Alloy and Its Hydrogen Storage Properties

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2012年第5期28卷 401-406页

作者： N.A. Niaz I. Ahmad Waheed S. Khan S. Tajammul Hussain Department of Physics COMSATS Institute of Information Technology Islamabad Pakistan Research Centre of Materials Science School of Materials Science and Engineering Beijing Institute of Technology National Centre for Physics Qaid-a-Azam University Islamabad Pakistan

Nanostructured Mg–Ni alloy with the particle size in the range of 40–50 nm was synthesized by the thermal decomposition of bipyridyl complexes of Mg and Ni metals at 773 K for 24 h under dry argon gas ambient. The as-prepared nano-alloy was characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM） for compositional and structural analysis. The alloy exhibited superior hydrogen absorption and desorption behavior with 3.2 wt% absorption within 1 min at 573 K and about 3 wt% desorption within 5–10 min at 573 K. This favorable behavior of Mg–Ni compound for the hydrogen storage is due to the specific nanostructure of the material. The low activation energy values and favorable thermodynamics indicate that the prepared Mg–Ni alloy is an attracting material for hydrogen storage applications.

关键词： Mg-Ni alloy Hydrogen storage Pressure-composition-temperature (P-C-T) measurements Transmission electron microscopy

Energy Conditions and Conservation Laws in LRS Bianchi Type Ⅰ Spacetimes via Noether Symmetries

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2019年第3期71卷 298-306页

作者： Sumaira Saleem Akhtar Tahir Hussain Department of Mathematics University of Peshawar

In this paper, we have completely classified the locally rotationally symmetric(LRS) Bianchi Type Ⅰ spacetimes via Noether symmetries(NS). The usual Lagrangian corresponding to LRS Bianchi Type Ⅰ metric is used to find the set of determining equations. To achieve a complete classification, these determining equations are generally integrated to find the components of NS vector field and the metric coefficients. During this procedure, several cases arise which give different Noether algebras of dimension 5,..., 9, 11, and 17. A comparison is established between the obtained NS and the Killing and homothetic vectors. Corresponding to all NS generators, the conservation laws are stated by using Noether's theorem. The metrics which we have obtained as a result of our classification are shown to be anisotropic or perfect fluids which satisfy certain energy conditions.

关键词： Bianchi type Ⅰ model Noether symmetry conservation Laws energy conditions

Wheat-Exuded Organic Acids Influence Zinc Release from Calcareous Soils

在线全文

学校读者我要写书评

暂无评论

Pedosphere 2011年第5期21卷 657-665页

作者： M.A.MAQSOOD S.HUSSAIN T.AZIZ M.ASHRAF Institute of Soil and Environmental Sciences University of Agriculture Department of Soil Science University of Sargodha

Rhizosphere drives plant uptake of sparingly soluble soil zinc(Zn).An investigation with three experiments was conducted to study organic acid exudation by two contrasting wheat genotypes(Sehar-06 and Vatan),Zn fractions in 10 different calcareous soils from Punjab,Pakistan,and release of different soil Zn fractions by organic *** two genotypes differed significantly in biomass production and Zn accumulation under deficient and optimum Zn levels in nutrient *** a deficient Zn level,Sehar-06 released more maleic acid in the rhizosphere than *** soils used in the present study had very different physicochemical properties;their total Zn and Zn distribution among different fractions varied *** release behaviour was determined by extracting the soils with 0.005 mol L-1 citric acid or maleic *** parabolic diffusion model best described Zn release as a function of *** diffusion model fitting indicated more maleic acid-driven than citric acid-driven soil Zn mobility from different *** Zn release in six consecutive extractions during 24 h ranged from 1.85 to 13.58 mg kg-1 using maleic acid and from 0.37 to 11.84 mg kg-1 using citric *** the selected calcareous soils,the results of stepwise linear regression indicated significant release of Fe-Mn oxide-bounded soil Zn by maleic acid and its availability to the Zn-effcient ***,release of maleic acid by plants roots played an important role in phytoavailability of Zn from calcareous soils.

关键词： citric acid maleic acid phytoavailability plant uptake rhizosphere

Pyridine-Thiourea Based High Performance Polymers: Synthesis and Characterization

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2015年第1期33卷 49-60页

作者： Ghulam Waris Humaira Masood Siddiqi Department of Chemistry Quaid-i-Azam University Islamabad Pakistan Department of Chemistry University of SheffieldUK

A novel diamine monomer, pyridine-2, 6-bis（（4-aminophenyl）thioureido）carbonyl（PATC） was synthesized efficiently and polymerized with various aromatic dianhydrides. Consequently, poly（pyridine thiourea-imide）s（PPTIs） with good thermal properties and flame retardancy were fabricated. The structures of PATC and PPTIs were characterized by FTIR, 1H-NMR, 13C-NMR spectroscopy along with elemental analysis, crystallinity, organosolubility, inherent viscosity and gel permeation chromatographic measurements. PPTIs containing C=S, CONH and meta substituted pyridine moieties in the polymer backbone showed amorphous nature and were readily soluble in highly polar organic solvents and even in less polar solvents such as tetrahydrofuran（THF）. Polymers had inherent viscosities in the range of 0.91-1.16 d L/g and molecular weight was found between 68000-77000 g/mol. The electrical properties of the PPTIs were estimated in terms of dielectric constant over a range of frequencies. Their thermal stability was determined by 10% weight loss temperature found in the range of 519-563 °C under inert atmosphere. The glass transition temperature of the polyimides varied between 247 °C and 267 °C. The flame retardant properties of PPTIs were investigated in terms of limiting oxygen index（LOI） which was found in the range of 38.26-39.95. Introduction of thiourea in the polymer backbone is an effective way to improve the thermal stability and flame retardancy. Thus PATC can be considered as an excellent candidate for the synthesis of high performance polymers.

关键词： Poly(pyridine thiourea-imide)s Crystallinity Flame retardancy GPC measurements.

Comprehensive screening and selection of okra (Abelmoschus esculentus) germplasm for salinity tolerance at the seedling stage and during plant ontogeny

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2012年第7期13卷 533-544页

作者： Ikram-ul-HAQ Asif Ali KHAN Iqrar Ahmad KHAN Muhammad Abubakkar AZMAT Department of Plant Breeding and Genetics University of AgricultureFaisalabadPakistan Institute of Horticultural Sciences University of AgricultureFaisalabadPakistan

The okra germplasm was screened for salinity tolerance at the seedling stage and during plant ontogeny. Substantial variation existed in okra for salinity tolerance at the seedling stage. An 80 mmol/L NaCI concentration was suitable for discriminating tolerant and non-tolerant okra genotypes. The pooled ranking of the genotypes, based on individual rankings for each trait （root and shoot length, germination percentage, and relative Na^＋ and K%＋） in individual NaCI concentrations, was effective for selecting tolerant genotypes. Genotypes selected at the seedling stage maintained their tolerance to NaCI during plant ontogeny, suggesting that screening of the germplasm entries and advanced breeding materials for salt tolerance at the seedling stage is effective. Among 39 okra genotypes, five were identified as the most tolerant genotypes and showed potential for use in breeding programs that focus on the development of salt-tolerant, high-yield okra cultivars.

关键词： Salinity tolerance Okra Growth stage Genetic variation Mechanism Potassium to sodium ion ratio (K^+/Na^+)

Thermal, Mechanical and Electrical Studies of Novel Shape Memory Polyurethane/Polyaniline Blends

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2015年第9期33卷 1313-1324页

作者： Rabia Sattar Ayesha Kausar Muhammad Siddiq Department of Chemistry Quaid-i-Azam University Nanosciences and Catalysis Division National Centre for Physics Quaid-i-Azam University Campus

Shape memory polymer （SMP） blends based on polyurethane （PU） and polyaniline （PANI） were prepared via chemical in situ polymerization process. The thermal, mechanical, electrical and shape memory properties were investigated. The structural characterization and morphology of the polymer blends were inspected by Fourier transform infrared （FTIR） and scanning electron microscopy （SEM）, respectively. The 1 wt% of PANI loading enhanced the thermal stability of the system up to 339 ~C. According to differential scanning calorimetry （DSC）, the glass transition temperature （Tg） and melting temperature （Tm） of PU/PANI blends increased with the polyaniline loading （0.1 wt%-l wt%）. Improved mechanical properties such as tensile strength and Young＇s modulus of PU matrix were also observed with PANI. Moreover, the electrical conductivity of PU/PANI blends was also found to be a function of PANI loading. Remarkable recoverability of thermally triggered shape memory （SM） behavior to the extent of 96% was achieved for 1 wt% PANI blend.

关键词： Shape memory Polyurethane Polyaniline Blends Conductivity.

Static and adaptive feedback control for synchronization of different chaotic oscillators with mutually Lipschitz nonlinearities

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2014年第11期23卷 223-231页

作者： Muhammad Riaz Muhammad Rehan Keum-Shik Hong Muhammad Ashraf Haroon Ur Rasheed Department of Electrical Engineering Pakistan Institute of Engineering and Applied Sciences (PIEAS) Islamabad Pakistan Department of Electronics Engineering Mohammad Ali Jinnah University Department of Cogno-Mechatronics Engineering and School of Mechanical Engineering Pusan National University 2 Busandaehak-ro Geumjeong-gu Busan 609-735 Republic of Korea Department of Electronics Engineering Mohammad Ali Jinnah University Islamabad Pakistan

This paper addresses the control law design for synchronization of two different chaotic oscillators with mutually Lipschitz nonlinearities. For analysis of the properties of two different nonlinearities, an advanced mutually Lipschitz condition is proposed. This mutually Lipschitz condition is more general than the traditional Lipschitz condition. Unlike the latter, it can be used for the design of a feedback controller for synchronization of chaotic oscillators of different dynamics. It is shown that any two different Lipschitz nonlinearities always satisfy the mutually Lipschitz condition. Applying the mutually Lipschitz condition, a quadratic Lyapunov function and uniformly ultimately bounded stability, easily designable and implementable robust control strategies utilizing algebraic Riccati equation and linear matrix inequalities, are derived for synchronization of two distinct chaotic oscillators. Furthermore, a novel adaptive control scheme for mutually Lipschitz chaotic systems is established by addressing the issue of adaptive cancellation of unknown mismatch between the dynamics of different chaotic systems. The proposed control technique is numerically tested for synchronization of two different chaotic Chua＇s circuits and for obtaining identical behavior between the modified Chua＇s circuit and the R6ssler system.

关键词： control theory and feedback synchronization mutually Lipschitz nonlinearity adaptive controlsystem