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The competitive and synergistic effect between adsorption enthalpy and capacity in D_(2)/h_(2)separation of m_(2)(m-dobdc)frameworks

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Chinese Chemical Letters 2021年第11期32卷 3562-3565页

作者： Fan Wu Liqiong Li Yanxi Tan el-Sayed m.el-Sayed Daqiang Yuan State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhou 350002China University of the Chinese Academy of Sciences Beijing 100049China College of Chemistry Fuzhou UniversityFuzhou 350108China Chemical Refining Laboratory Refining DepartmentEgyptian Petroleum Research InstituteNasr CityCairo 11727Egypt

hydrogen isotope separation is a challenging task due to their similar ***,based on the chemical affinity quantum sieve(CAQS)effect,the D_(2)/h_(2)separation performance of m_(2)(m-dobdc)(m=Co,Ni,mg,mn;m-dobdc^(4-)=4,6-dioxido-1,3-benzenedicarboxylate),a series of honeycomb-shaped mOFs with high stability and abundant open metal sites,are studied by gases sorption and breakthrough experiments,in which two critical factors,gas uptake and adsorption enthalpy,are taken into *** these mOFs,Co_(2)(m-dobdc)exhibits the longest D_(2)retention time of 180 min/g(h_(2)/D_(2)/Ne:1/1/98)at 77 K because of its second-highest adsorption enthalpy(10.7 kJ/mol for h_(2)and 11.8 kJ/mol for D_(2))and the best sorption capacity(5.22 mmol/g for h_(2)and 5.49 mmol/g for D_(2))under low pressure of 1 kPa and 77 K,which make it a promising material for industrial hydrogen isotope ***,the results indicate that h_(2)and D_(2)capacities under low pressure(about 1 kPa)dominate the final D_(2)/h_(2)separation property of mOFs.

关键词： Breakthrough experiment Open metal sites hydrogen isotope separation Sorption and separation Chemical affinity quantum sieve

EXACT EVALUATIONS OF FINITE TRIGONOmETRIC SUmS BY SAmPLING ThEOREmS

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Acta mathematica Scientia 2011年第2期31卷 408-418页

作者： m.h. Annaby R.m. Asharabi Department of mathematics Faculty of Science Cairo University Department of mathematics Faculty of Education Al-MahweetSana'a University

We use the sampling representations associated with Sturm-Liouville difference operators to derive generalized integral-valued trigonometric sums. This extends the known results where zeros of Chebyshev polynomials of the first kind are involved to the use of the eigenvalues of difference operators, which leads to new identities. In these identities Bernoulli＇s numbers play a role similar to that of Euler＇s in the old ones. Our technique differs from that of Byrne-Smith （1997） and Berndt-Yeap （2002）.

关键词： Trigonometric sums difference equations sampling theorem

Determination of Trace Amounts of Vanadium by Kinetic-Catalytic Spectrophotometric methods

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Chinese Journal of Chemistry 2006年第4期24卷 557-562页

作者： POURETEDAL, h.R. KEShAVARZ, m.h. Department of Chemistry Malek-ashtar University of Technology Shahinshahr Iran

Kinetic-catalytic spectrophotometric methods were proposed for the determination of trace amounts of vanadium element as vanadium（Ⅳ） and/or V（Ⅴ） ions. The vanadium（Ⅳ） as VO^2＋ ion and/or vanadium（Ⅴ） as VO3^- ion showed a catalytic effect on the kinetic reactions between a color reagent such as methylthymol blue （mTB） or SPADNS and bromate in acidic media. The rate of decrease in the absorbance of the reagent mTB at 440 nm or SPADNS at 510 nm was proportional to concentration of V（Ⅳ） and/or V（Ⅴ） ions in the solution. The linear ranges for determination of vanadium were obtained in the range of 1.0-150 and 5.0-100.0 μg/L by the fixed-time and slope methods, respectively, with using mTB as reagent. In the presence of SPADNS as reagent, the calibration curves were made in the amplitude 1.0-200.0 and 5.0-150 μg/L of vanadium ion by the fixed-time and slope methods, respectively. Using fixed-time method, the limits of detection were obtained to be 0.5 and 0.7 μg/L of vanadium in the presence of mTB and SPADNS as reagents, respectively. Detection limits of vanadium by slope method and reagents of SPADNS and mTB were obtained to be 3.5 and 3.8 μg/L of vanadium, respectively. The proposed methods were applied successfully to determination of vanadium in synthetic and real samples.

关键词： kinetic-catalytic method SPADNS methylthymol blue vanadium

Effect of substitution group on dielectric properties of 4h-pyrano [3,2-c] quinoline derivatives thin films

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Chinese Physics B 2016年第7期25卷 440-449页

作者： h m Zeyada F m el-Taweel m m el-Nahass m m el-Shabaan Department of Physics Faculty of Science Damietta University Department of Chemistry Faculty of Science Damietta University Department of Physics Faculty of Education Ain Shams University

The AC electrical conductivity and dielectrical properties of 2-amino-6-ethyl-5-oxo-4-（3-phenoxyphenyl）-5,6-dihydro-4h-pyrano[3, 2-c]quinoline-3-carbonitrile（Ph-hPQ） and 2-amino-4-（2-chlorophenyl）-6-ethyl-5-oxo-5,6-dihydro-4h-pyrano [3, 2-c] quinoline-3-carbonitrile（Ch-hPQ） thin films were determined in the frequency range of 0.5 k hz–5 mhz and the temperature range of 290–443 K. The AC electrical conduction of both compounds in thin film form is governed by the correlated barrier hopping（CBh） mechanism. Some parameters such as the barrier height, the maximum barrier height, the density of charges, and the hopping distance were determined as functions of temperature and frequency. The phenoxyphenyl group has a greater influence on those parameters than the chlorophenyl group. The AC activation energies were determined at different frequencies and temperatures. The dielectric behaviors of Ph-hPQ and Ch-hPQ were investigated using the impedance spectroscopy technique. The impedance data are presented in Nyquist diagrams for different temperatures. The Ch-hPQ films have higher impedance than the Ph-hPQ films. The real dielectric constant and dielectric loss show a remarkable dependence on the frequency and temperature. The Ph-hPQ has higher dielectric constants than the Ch-hPQ.

关键词： thin films quinoline derivatives dielectrical properties correlated barrier hopping

An empirical study on vortex-generator insert fitted in tubular heat exchangers with dilute Cu–water nanofluid flow

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Chinese Journal of Chemical Engineering 2016年第6期24卷 728-736页

作者： m. Khoshvaght-Aliabadi m.h. Akbari F. hormozi Department of Chemical Engineering Shahrood Branch Islamic Azad University Shahrood lran School of Chemical Petroleum and Gas Engineering Semnan University Semnan lran

The heat transfer enhancement(hTE) in tubular heat exchangers fitted with vortex-generator(VG) inserts is experimentally investigated. The studied four parameters and ranges are: winglets-pitch ratio(1.33, 2.67, and 4),winglets-length ratio(0.33, 0.67, and 1), winglets-width ratio(0.2, 0.4, and 0.6), and Reynolds number(5200to 12200). The testing fluids are the water and Cu–water nanofluid at the volumetric fraction of 0.2%. The results obtained on hTE, pressure drop, and performance evaluation criterion(PEC) are compared with those for water in a smooth tube. It is found that the VG inserts with lower winglets-pitch ratio and higher winglets-length/width ratios present higher values of hTE and pressure drop. Over the range studied, the maximum PEC of 1.83 is detected with the Cu–water nanofluid inside the tube equipped with a VG insert at the winglets-width ratio of0.6 for the maximum Reynolds number, when the heat transfer rate and pressure drop are 1.24 times and 2.03 times of those in the smooth tube. Generalized regression equations of the Nusselt number, friction factor, and PEC are presented for the tubular heat exchangers with the VG inserts for both water and Cu–water *** is concluded that the main advantage of the VG inserts is their simple fabrication and considerable performance, particularly at higher Reynolds number.

关键词： heat transfer enhancementVortex-generator insertNanofluid Turbulent flowCorrelation

REAL-TImE FLOOD FORECASTING mODelING OF 1D UNSTEADY ChANNel FLOW AND KALmAN FILTER

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Journal of hydrodynamics 2001年第1期13卷 64-69页

作者： Li, Z.J. Weng, m.h. Coll. of Water Res. and Environ. Hohai Univ. Nanjing 210024 China

The model of 1D unsteady channel flow combined with the Kalman filter for real-time channel flood forecasting was attempted. The suitable upstream and downstream boundary conditions were suggested. The system equation was given by the linearization of the finite difference equations of the mass conservation and momentum equations as well as the boundary conditions. In the Kalman filter updating model, because the number of measurement variable is less than that of state-space variables, the measurement error covariance matrix could be estimated in real time through the innovation sequence, and the system error covariance matrix needs to be estimated preliminarily. A real example of flood forecasting in the huaihe River was given to explain how the method works. The results show that the model is reasonable and effective.

关键词： Channel flow Computer simulation Kalman filtering Unsteady flow

Effect of thermomechanical treatment on microstructure and hardness behavior of AZ63 magnesium alloy

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Acta metallurgica Sinica(English Letters) 2009年第6期22卷 401-407页

作者： h. Jafari m.h. Idris A. Ourdjini G. Payganeh Department of materials Engineering Faculty of Mechanical EngineeringUniversiti Teknologi Malaysia Department of materials Engineering Faculty of Mechanical EngineeringShahid Rajaee Teacher Training University Department of materials Engineering Faculty of Mechanical Engineering Shahid Rajaee Teacher Training University

Due to their high specific strength and low density, magnesium alloys are widely used in many weight-saving applications. This research is aimed at investigating the microstructure and hardness of commercial AZ63 alloy specimens subjected to two different thermomechanical treatments （TmTs）. For the first TmT, after solution treated at the temperature of 380 ℃ for 20 h, AZ63 alloy specimens were 5% cold worked by rolling process followed by ageing at the temperatures of 150 ℃and 250 ℃ for 3, 9 and 25 h. In the second TmT, the specimens were solution treated at the temperature of 380 ℃ for 20 h, underwent 2% cold worked and quenched in water of 0 ℃. half of the specimens were then 2% cold worked whilst the rest were rolled to 8% cold worked. All the specimens were then aged at the temperatures of 150 ℃ and 250 ℃ for 3, 9 and 25 h. Optical microscope was used to analyze the microstructures of the specimens. hardness test was too conducted to measure the effect of the treatments on the specimens. Results show that two-step aging enhances the hardness of the specimens due to the distribution of fine β-phase （mglTA112） in the alloy matrix. The results also reveal that, the best hardness from the first TmT was produced by specimen that was pre-aged at 150 ℃ whereas, in the second TmT, aging at 250 ℃ exhibited the best hardness values.

关键词： Thermomechanical treatment magnesium alloys Cold work Aging AZ63

heavy metal concentrations in edible bivalves and gastropods available in major markets of the Pearl River Delta

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Journal of Environmental Sciences 2001年第2期13卷 210-217页

作者： FANG Zhan-qiang ChEUNG R.Y.h. WONG m.h. Department of Biology South China Normal UniversityGuangzhou 510631China Department of Biology and Chemistry City University of Hong Kong83 Tat Chee AvenueKowloonHong Kong Institute for Natural Resources and Waste management and Department of BiologyHong Kong Bapt ist UniversityKowloon TongHong Kong

molluscs are able to accumulate heavy metals and impose health hazard to consumers. The main objective of the present study is to investigate the heavy metal concentrations in edible bivalves and gastropods available in major markets of the Pearl River Delta. Fourteen species of edible molluscs were purchased from six markets in hong Kong and Guangdong Province. The fresh of these biota were tested for their cadmium (Cd), copper (Cu), zinc (Zn), lead (Pb), nickel (Ni), chromium (Cr), antimony (Sb) and tin (Sn) concentrations (based on wet weight). The results indicated that amongst the 14 edible molluscs, only Cd, Pb, Ni, Cr, Sb and Sn concentrations in three species (Ruditapes philippinarum, Perna viridis and hemifusus tuba) were within the local regulatory limits. Over 60% of bivalve species exceeded maximum permitted levels of Cd (2 mug/g) and Cr (1 mug/g), while over 40% of gastropod species exceeded the maximum levels of Sb (1 mug/g) and Cr (1 mug/g). most of the samples collected from.h.ng Kong had significantly higher contents of Pb and Sb, but similar levels of Cd, Cu and Zn when compared with samples collected across the border ( p ely). In general, the molluscs purchased in Guangdong markets had higher metal contents than those purchased from the hong Kong markets. When compared with the Provisional Tolerable Weekly Intake or maximum Acceptable Daily Load recommended by FAO/WhO Expert Committee on Food Additives, Cd levels of five species (Anadara ferruginea, Pinna pectinata, Chlamys nobilis, Babylonia lutosa and hemifusus terntanus) and Cr levels of seven species ( Anadara ferruginea, Paphia undulata, Pinna pectinata, Babylonia lutosa, hemifusus terntanus, Cymbium melo and Cipangopaludina chinensis) were higher than both the human daily acceptable limits (for Cd and Cr respectively) and the local regulatory levels (for Cd and Cr respectively).

关键词： heavy metals edible molluscs human health Pearl River Delta

electrical properties of ^(70)Ge:Ga near the metal–insulator transition

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Journal of Semiconductors 2015年第6期36卷 1-5页

作者： m Errai A el kaaouachi h el idrissi Laboratoire mSTI Ecole Supérieure de tecchnologie d'Agadir B.P: 33/S University Ibn ZohrFaculty of Sciences AgadirMorocco Laboratoire electronique électrotechnique Automatique et Traitement de l'Information Département Génie Electrique Faculté des Sciences et Techniques de Mohammedia Université Hassan II Mohammedia CasablancaBP 146 Quartier YasminaMohammedia

The results of the metal-insulator transition （mIT） induced by impurity concentration are presented in the case of metallic and insulating samples 70Ge：Ga p-type. The eight samples studied have Ga concentrations N ranging from 1.848 × 1017 to 1.912 × 10^17 cm-3. The conductivity measurements were carried out at low temperature in the range 1 to 0.019 K. We provide physical explanations to explain the behaviors of the temperature dependence of the electrical conductivity in both sides of the mIT. The data are for a 70Ge：Ga sample prepared and reported by Itoh et aL in Ref. [Itoh K m, Watanabe m, Ootuka Y, et al. J Phys Soc Jpn, 2004, 73（1）： 173].

关键词： 70Ge: Ga semiconductor low temperature impurity concentration metal-insulator variable rangehopping conductivity transport properties