Modification of polysulfone with pendant carboxylic acid functionality for ultrafiltration membrane applications

p-Carboxyphenoxymethyl polysulfone (CPMPSF) was synthesized in two steps: (i) chloromethylation of polysulfone (PSF) by in situ generated chloromethyl radical in presence of stannic chloride in tetrachloroethane and (ii) reaction of chloromethylated PSF with p-hydroxybenzoic acid in presence of potassium carbonate in dimethylformamide. The structures of the modified PSFs were confirmed by elemental analysis, IR, ¹H–NMR and $^{{13}}$ C–NMR techniques. The PSF and CPMPSF based ultrafiltration membranes were prepared according to phase–inversion process using water as nonsolvent at 4° and 15 °C, employing casting dope having different amounts of polymer (PSF or CPMPSF), polyvinylpyrrolidone (PVP) and solvent, dimethylformamide (DMF). The membranes were characterized for their pore size, pure water flux and flux and rejection for the permeation of different molecular weight poly(ethylene glycol) (PEG) solutions and sodium chloride (NaCl) solution. The pore radius of the CPMPSF membrane which was prepared without PVP in the casting dope was about 222 Å, whereas, that of the membrane prepared in the presence of PVP (6 wt%) in the casting dope was about 124 Å. For the PSF membranes, pore radii were 80 Å (without PVP) and 176 Å (with PVP 6 wt%). The CPMPSF-based membranes exhibited higher flux and rejections for PEG and NaCl solutions, as compared to the PSF membranes, due to the presence of hydrophilic carboxylic acid group. The CPMPSF membrane exhibited about 48% rejection of NaCl when tested for 5000 ppm feed solution at 400 psi.     

Ce_(1-x)Dy_(x-y)Sr_yO_(2-δ)导电体的制备与表征(英文)

在Ce1-x Dyx-y Sry O2-δ体系中,研究了Dy和Se对总离子电导率的影响。在该体系中,使用麦芽糖和果胶作为有机前驱体,通过改性溶胶-凝胶工艺,在x=0.15,y=0.015,0.03和0.045的条件下,制备不同组分的导电体。采用X射线衍射谱的Rietveld拟合验证了导电体具有空间群Fmm的立方结构。从SEM像可以看到具有明显晶界、相对均匀的晶粒。在150～500°C的温度范围和40 Hz～1 MHz的频率范围内,采用四探针交流阻抗法测量导电体的总离子电导率。与单掺杂的二氧化铈样品相比,Ce0.85Dy0.12Sr0.03O2-δ具有更高的电导率。     

Microstructure and corrosion behaviour of gas tungsten arc welds of maraging steel

Superior properties of maraging steels make them suitable for the fabrication of components used for military applications like missile covering, rocket motor casing and ship hulls. Welding is the main process for fabrication of these components, while the maraging steels can be fusion welded using gas tungsten arc welding(GTAW) process. All these fabricated components require longer storage life and a major problem in welds is susceptible to stress corrosion cracking(SCC). The present study is aimed at studying the SCC behaviour of MDN 250(18% Ni) steel and its welds with respect to microstructural changes. In the present study, 5.2 mm thick sheets made of MDN 250 steel in the solution annealed condition was welded using GTAW process. Post-weld heat treatments of direct ageing(480 C for 3 h), solutionizing(815 C for 1 h) followed by ageing and homogenizing(1150 C for 1 h) followed by ageing were carried out. A mixture of martensite and austenite was observed in the microstructure of the fusion zone of solutionized and direct aged welds and only martensite in as-welded condition. Homogenization and ageing treatment have eliminated reverted austenite and elemental segregation. Homogenized welds also exhibited a marginal improvement in the corrosion resistance compared to those in the as-welded, solutionized and aged condition. Constant load SCC test data clearly revealed that the failure time of homogenized weld is much longer compared to other post weld treatments, and the homogenization treatment is recommended to improve the SCC life of GTA welds of MDN 250 Maraging steel.     

Transportation planning from remote sensing—a case study of the Tuni region in Andhra Pradesh,India

Abstract

Transportation planning deals with the generation and distribution of activity along a road network. A safe, convenient and efficient movement of goods and people requires an integration of engineering, economic, environmental, political and social aspects and an optimal allocation of these activities needs to be carefully planned. Even when geotechnical aspects cause a constraint it is possible to plan a route which optimally utilises the land. Remote sensing data acquired from airbourne space platforms and engineering surveys have offered the planner a complete picture of the land and helped to identify the location and quantity of activity from method of the Moments/Trip polygon method and the allocation technique. Cost modelling technique has been used to identify the optimum route for the user, system, non-user, government and region point of view.     

Self-assembled nanofilm of 1,2-dihydro-3-(octadecylthio)benzotriazine on copper for corrosion protection

The self-assembled nanofilm of 1,2-dihydro-3-(octadecylthio)benzotriazine (DOTBT) was formed on fresh copper surface obtained by etching with 7 N nitric acid at a room temperature of 30 °C. The conditions for formation of the DOTBT nanofilm have been optimized by electrochemical impedance and electrochemical quartz crystal nanobalance (EQCN) studies. The DOTBT nanofilm on copper surface was characterized by contact-angle measurement, X-ray photoelectron spectra (XPS), reflection absorption FTIR spectra and atomic force micrographs (AFM). It is inferred that formation of DOTBT film is due to chemisorption of DOTBT on copper surface through nitrogen and subsequent complex formation between DOTBT and Cu ⁺ ions. Corrosion protection ability of DOTBT nanofilm was evaluated in dilute aqueous NaCl solution using electrochemical impedance, potentiodynamic polarization, weight-loss and XPS studies. These studies inferred that the DOTBT film protects effectively copper from corrosion. Potentiodynamic polarization studies revealed that the DOTBT film inhibits corrosion by controlling the cathodic reaction. The mechanism of corrosion protection of copper by DOTBT nanofilm is discussed in this paper.     

Single pass kernel k-means clustering method

In unsupervised classification, kernel k-means clustering method has been shown to perform better than conventional k-means clustering method in identifying non-isotropic clusters in a data set. The space and time requirements of this method are O(n ²), where n is the data set size. Because of this quadratic time complexity, the kernel k-means method is not applicable to work with large data sets. The paper proposes a simple and faster version of the kernel k-means clustering method, called single pass kernel k -means clustering method. The proposed method works as follows. First, a random sample $\mathcal{S}$ is selected from the data set $\mathcal{D}$ . A partition $\Pi_{\mathcal{S}}$ is obtained by applying the conventional kernel k-means method on the random sample $\mathcal{S}$ . The novelty of the paper is, for each cluster in $\Pi_{\mathcal{S}}$ , the exact cluster center in the input space is obtained using the gradient descent approach. Finally, each unsampled pattern is assigned to its closest exact cluster center to get a partition of the entire data set. The proposed method needs to scan the data set only once and it is much faster than the conventional kernel k-means method. The time complexity of this method is O(s ²?+?t?+?nk) where s is the size of the random sample $\mathcal{S}$ , k is the number of clusters required, and t is the time taken by the gradient descent method (to find exact cluster centers). The space complexity of the method is O(s ²). The proposed method can be easily implemented and is suitable for large data sets, like those in data mining applications. Experimental results show that, with a small loss of quality, the proposed method can significantly reduce the time taken than the conventional kernel k-means clustering method. The proposed method is also compared with other recent similar methods.     

Transient analysis of the complementary MOS IC inverter†

A set of transient equations for rise and fall times of a complementary MOS IC inverter is developed. These equations utilize fully the device-processing parameters extracted from the fabrication technology. The current-voltage relationship of the inverter is used in developing the transients equations. An argument is presented in this analysis that takes into account the grounded substrate case and provides an accurate value of threshold voltage under strong back gate bias when the MOS transistor is in saturation. The rise and fall time equations provide the necessary information for a worst-case design. Sample calculations are also included and the results of the calculations are summarized.     

SUPPLEMENTATION OF WHEAT MUFFINS WITH DRIED DISTILLERS GRAIN FLOUR

The use of dried distillers grain (DDG) flour as an ingredient for preparing wheat muffins was investigated. DDG can be incorporated up to 10% in wheat muffins without significant changes in appearance, texture, flavor, and overall acceptability. Addition of either raisins or blueberries to wheat muffins allowed for an increase in the incorporation level of DDG to 15%. Wheat muffins supplemented with DDG had a higher protein, amino acids, and certain minerals content than wheat muffins without DDG.     

Modelling spatial density using continuous wavelet transforms

Due to increase in the satelite launch activities from many countries around the world the orbital debris issue has become a major concern for the space agencies to plan a collision-free orbit design. The risk of collisions is calculated using the in situ measurements and available models. Spatial density models are useful in understanding the long-term likelihood of a collision in a particular region of space and also helpful in pre-launch orbit planning. In this paper, we present a method of estimating model parameters such as number of peaks and peak locations of spatial density model using continuous wavelets. The proposed methodology was experimented with two line element data and the results are presented.     

Cocoa butter substitutes from sal (Shorea robusta) fat

Commercial sal fats vary in solidification properties and are unsuitable for use as cocoa butter extenders without further processing. Solvent and melt fractionation processes were used and the fractions were evaluated. One type could be satisfactorily fractionated by solvent or by melt fractionation at 23°C to obtain a stearin (yield 75–85%) of satisfactory quality, but the other could only be satisfactorily processed by melt fractionation at 38°C, removing about 10% stearin. The processing requirement of the fat can be assessed easily by determining the cooling curve.