Investigation of some new solid cation exchange membrane electrodes for activity determination of mono-valent cations

Solid cation exchange membrane electrodes prepared by incorporating weak cation exchangers stilbite, bentonite clay and ammonium phosphomolybdate in cellulose nitrate inert matrix, have been characterized by determination of their thermodynamic effective charge densities. Null potentiometry method has been used for the determination of activities of Na⁺, K⁺ and NH⁺₄ cations in their chloride solutions separately and in the mixture of two cations using these electrodes. The selectivity of these electrodes for cations has been interpreted on the basis of Thermodynamic effective charge density of the membrane electrode and the results have been confirmed by determining the selectivity coefficients of these electrodes for the investigated cations by an IUPAC method. The error in the determination of activities of cations and response time (t/min) of electrode have been correlated with the thermodynamic effective charge density of the electrode. It has been found that the electrodes with low thermodynamic effective charge density are more suitable for this purpose and that selectivity of an electrode for a particular cation in mixture depends upon the characteristics of both cation and electrode.     

Leaching of nitrate from cropped rainfed terraces in the mid-hills of Nepal

Intensification of crop production in the mid-hills of Nepal has led to concerns that nitrogen loss by leaching may increase. This study estimated the amount of N leached during two years from rainfed terraces (bari-land) at three locations in Nepal. Maize or upland rice grown in the monsoon season was given either no nutrient inputs or inputs via either nitrogen fertilizer or farmyard manure. Nitrate concentration in soil solution was measured regularly with porous ceramic cup samplers and drainage estimated from a simple soil water balance. Estimated losses of nitrogen by leaching ranged from 0 to 63.5 kg N ha^–1 depending on location and the form of nitrogen applied. Losses from plots receiving no nutrient inputs were generally small (range: 0–35 kg N ha^–1) and losses from plots where nitrogen was applied as manure (range: 2–41 kg N ha^–1) were typically half those from plots with nitrogen applied as fertilizer. Losses during the post-monsoon crops of finger millet were small (typically <5% of total loss) although losses from the one site with blackgram were larger (about 13%). The highest concentrations of nitrate in solution were measured early in the season as the monsoon rains began and immediately following fertilizer applications. Leaching losses are likely to be minimised if manure is applied as a basal nutrient dressing followed by fertilizer nitrogen later in the season.     

Developments in Ozone-Based Bleaching of Pulps

ABSTRACT

This paper summarizes the review of developments in the area of ozone-based elemental chlorine free (ECF) and total chlorine free (TCF) bleaching of wood and non-wood pulps. Focused areas of review are reaction mechanism of ozone with carbohydrates and lignin, effect of process conditions maintained during ozone bleaching on pulp properties, effect of using different cellulose protectors, effect of alkaline extraction after ozone bleaching of pulps, effect of ozone bleaching on final bleached pulp properties, ECF and TCF bleaching sequences used along with ozone for of wood and non-wood pulps, and commercial scale utilization of ozone for pulp bleaching.     

Electrical transport in light rare-earth orthochromites

Electrical conductivity, , Seebeck coefficient, S, and dielectric constant, , measurements on the pressed pellets of six light rare-earth orthochromites, RCrO₃, where R = La, Pr, Nd, Sm, Eu and Gd, have been carried out in the temperature range 300 to 1000 K. These are essentially electronic conductors, exhibiting p-type extrinsic semiconducting nature in the studied temperature range. The extrinsic charge carriers (holes) originate from Cr⁴⁺ centres which are present due to native defects in these solids. Their room-temperature electrical conductivities lie in the range 10^–7 to 10^{–5 –1} cm^–1, which become of the order of 10^{–2 –1} cm^–1 near 1000 K. The conductivity is a maximum in LaCrO₃ and drops across the RCrO₃ series, with SmCrO₃ being an exception. The mechanism involved in the electrical transport is the hopping of holes from Cr⁴⁺ centres to neighbouring Cr³⁺ ions. The activation energy of transport is nearly 0.3 eV. Typical hopping mobility of the holes is of the order of 10² cm^–2 V^–1 sec^–1 at 325 K and of the order of 10 cm² V^–1 sec^–1 at 1000 K. The mobility activation energy of the holes in a typcial RCrO₃ decreases with temperature due to the smoothing of the potential barriers between Cr⁴⁺ and Cr³⁺ sites. Several discontinuities are observed in the T against T ^–1 and S against T ^–1 plots of RCrO₃. The anomalies which these discontinuities reflect here have also been indicated.     

Application of fuzzy TOPSIS in evaluating sustainable transportation systems

Sustainable transportation systems are the need of modern times. There has been an unexpected growth in the number of transportation activities over years and the trend is expected to continue in the coming years. This has obviously associated environmental costs like air pollution, noise, etc. which is degrading the quality of life in modern cities. To cope us this crisis, municipal administrations are investing in sustainable transportation systems that are not only efficient, robust and economical but also friendly towards environment. The challenge before the transportation decision makers is how to evaluate and select such sustainable transportation systems. In this paper, we present a multicriteria decision making approach for selecting sustainability transportation systems under partial or incomplete information (uncertainty). The proposed approach comprises of three steps. In step 1, we identify the criteria for sustainability assessment of transportation. In step 2, experts provide linguistic ratings to the potential alternatives against the selected criteria. Fuzzy TOPSIS is used to generate aggregate scores for sustainability assessment and selection of best alternative. In step 3, sensitivity analysis is performed to determine the influence of criteria weights on the decision making process. A numerical illustration is provided to demonstrate the applicability of the approach.The strength of the proposed work is its practical applicability and the ability to generate good quality solutions under uncertainty.     

Peristaltic transport of fractional Maxwell fluids in uniform tubes: Applications in endoscopy

This paper presents the effect of endoscope on peristaltic transport of fractional Maxwell fluids through the gap between two concentric uniform tubes under the assumptions of large wavelength and low Reynolds number. The inner tube is an endoscope and the outer tube has a sinusoidal wave traveling down its wall, i.e. the inner tube is rigid and outer tube is flexible. Solutions for the problem are obtained by two numerical methods named as homotopy perturbation method and variational iteration method. The impacts of endoscope, relaxation time and fractional parameters on pressure per wavelength and friction force (on inner and outer tubes) per wavelength are discussed with the help of computational results which are presented in graphical form. On the basis of the present study, it is revealed that pressure diminishes with increase in the magnitude of first fractional parameter, ratio of tube radii and relaxation time whereas it enhances with increasing the magnitude of second fractional parameter and amplitude ratio. The study further reveals the important fact that the effects of all pertinent parameters (except ratio of tube radii) on friction force at inner tube are similar in magnitude but opposite in direction to that of pressure and the effects of same parameters on friction force at outer tube are similar in magnitude but opposite in direction to that of pressure.     

Crystallization kinetics in glassy Ge20Se80−x In x alloys

Crystallization kinetics is studied in glassy Ge₂₀Se_80–xIn_x (0 x 20) using isothermal annealing at temperatures between the glass transition and melting. D.c. conductivity is taken as a parameter to estimate the extent of crystallization (). The activation energy of crystallization (E) and the order parameter (n) are calculated by fitting the values of in the Avrami equations of isothermal crystallization. The results indicate that E is highly composition-dependent, which is explained in terms of the stable phases in the Ge-Se-In system.     

Correlation study between structural, magnetic and transport properties of annealed Co thin films

This paper presents structural, magnetization and transport properties measurements carried out on as-deposited Co (400 Å) thin film as well as samples annealed in the temperature range 100-500 °C in steps of 100 °C for 1 h. The samples used in this work were deposited on float glass substrates using ion beam sputtering technique. The magnetization measurements carried out using MOKE technique, clearly indicates that as-deposited as well as annealed samples up to 500 °C show well saturation magnetization with applied magnetic field. The as-deposited sample shows coercivity value (H_c) of 26 Oe, and it is increased to 94 Oe for 500 °C-annealed sample. A minimum coercivity value of 15 Oe is obtained for 200 °C annealed sample. The XRD measurements of as deposited films show microcrystalline nature of Co film, which becomes crystalline with increase in annealing temperature. The corresponding resistivity measurements show gradual decrease in resistivity. AFM technique was employed to study the surface morphology of as deposited film as well as annealed thin films. Observed magnetization, and resistivity behaviour is mainly attributed to the (i) change in crystal structure (ii) increase in grain size and (iii) stress relaxation due to the annealing treatment.     

钢包使用次数对钢水中非金属夹杂物形成的影响

瑞典Hagfors的Uddeholm Tooling进行了一项实验研究,以检验钢包釉面对钢水中非金属夹杂物形成的影响.钢水样取自不同处理阶段和不同使用次数的钢包.在光学显微镜下计算夹杂物数量时发现,脱氧前和钢包处理结束时,夹杂物总数随钢包使用次数的增加而增多,钢包使用18次以上时,增加明显.其中大部分是尺寸极小的夹杂物.钢水试样内总氧含量和溶解氧含量间的差值进一步证实了这一观察结果,也证明了夹杂物数量随钢包使用次数的增长而增多的结论.SEM-EDX分析表明,浇铸前有两种类型夹杂物,即一种是与3CaO*Al2O3成分极相近的氧化物夹杂,另一种是与第一种相似的氧化物及MgO相组成的夹杂.这一结果与钢包釉面渣渗透层内存在3CaO*Al2O3和MgO的报告结果一致.由此得出结论,钢包釉面是钢包处理过程中,工具钢内非金属夹杂的最主要来源.