Soymilk concentration by ultrafiltration: effects of pore size and transmembrane pressure on filtration performance

The effects of membrane pore size and operating pressure on filtration flux, membrane fouling and solute rejections of soymilk during ultrafiltration were studied. Soymilk was concentrated from an initial level of 6.5% solid content to 20% solid content using ultrafiltration membranes. Hollow fibre cross‐flow type cartridges having molecular weight cut‐off (MWCO) as 1, 10 and 30 kDa were used in the experiments. Filtration data were satisfactorily fitted to De La Garza and Boulton's exponential model to find the exponential fouling coefficient (k) and the membrane resistance (R_m). The permeate fluxes obtained in 10 and 30‐kDa MWCO membranes were found to be approximately four times higher than that of 1‐kDa MWCO membrane, at transmembrane pressure between 100 and 240 kPa. The average flux obtained was 0.7, 3.15 and 2.7 L m^?2‐h for 1, 10 and 30‐kDa MWCO membranes, respectively. The R_m value of membranes was found to decrease as the MWCO of membranes increased and transmembrane pressure decreased. The total solid content of permeates obtained by these membranes was between 0.45% and 1.4%. Membrane‐concentrated soymilk was found to have lighter colour and almost half the value of viscosity compared with evaporated milk.     

Characterisation and modelling of parasitic effects and failure mechanisms in AlGaN/GaN HEMTs

This work is a study of the degradations of AlGaN/GaN HEMTs induced by 2000 h of ageing tests. The methodology is based on cross-characterisation analysis.The life tests (HTO 150 °C, HTO 175 °C and HTRB 175 °C and Idq 90 °C) have mainly induced a decrease of the saturation drain current, occurring during the first 50 h, followed by a stabilisation. There is a shift of the pinch-off voltage in the range of 0.1–0.2 V while the Schottky contact is rather stable after ageing. The evolution of the electrical characteristics after ageing does not depend on the bias conditions but rather more on the channel temperature. It seems to be neither field nor current driven. Low frequency drain current noise demonstrates that there is no trap creation and the weak evolution of the 1/f noise confirms that there is no degradation in the channel. Moreover, pulsed I–V measurements show a weak evolution of gate lag and drain lag rates after ageing. The same degradation mode is demonstrated for all life tests with rather high activation energy of 1.6 eV. The weak evolution of electrical characteristics observed during the life tests cannot be obviously explained by a single physical mechanism and results from a combination of trap-related effects before stabilisation.     

Impact of chemical cleaning and air-sparging on the critical and sustainable flux in a flat sheet membrane bioreactor for municipal wastewater treatment.

The paper discusses the experimental optimisation of both chemical and mechanical cleaning procedures for a flat-sheet submerged membrane bioreactor fed with municipal wastewater. Fouling was evaluated by means of the critical flux concept, which was experimentally measured by short-term flux-stepping tests. By keeping constant most important parameters of the biological process (MLSS, sludge age), two different chemical cleaning protocols (2,000 mg L(-1) NaOCl and 200 mg L(-1) NaOCl) were applied with different frequency and, after approximately 9 months of operation, the criticality threshold was determined under different values of SAD(m) (specific aeration demand per unit of membrane surface area). The weaker and more frequent chemical cleaning regime (200 mg L(-1), monthly) proved much more effective than the stronger and less frequent strategy (2,000 mg L(-1), once every three months). The improvement of performances was quantified by two TMP-based parameters, the fouling rate and the DeltaTMP (difference between TMP values during the increasing and decreasing phase of hysteresis). The best performing configuration was then checked over a longer period by running four long-term trials showing an exponential trend of the sub-critical fouling rate with the imposed flux.     

Studies on characterization and variation in triglyceride fatty acids from punt/us sarana body lipids

Body lipids of P. sarana of four different sizes were fractionated into phospholipids, neutral lipids, nonsaponifiables, total fatty acids, polyunsaturated, monounsaturated and saturated fatty acid fractions. Percentage composition of each fraction was determined. The triglyceride fatty acids were identified by thin layer and gas liquid chromatography. C₈ to C₂₃ fatty acids including both odd numbered and branched chain acids were detected. The major constituents were C₁₄, C₁₅, C₁₆, C_16:1, C₁₈ C_18:1, C_18:2, C_18:3; forty-three other acids were detected in lower proportions. Composition of each fatty acids and their variation with size have been discussed.tP. sarana body lipids in general showed a behavior typical of fresh water fish by having a higher percentage of saturated C₁₆ and unsaturated C₁₈ acids and a lower percentage of unsaturated C₂₀ acid.     

Synthesis of glycosides in which the aglycon is an N-(hydroxymethyl)amino-1,3,5-triazine derivative

The synthesis of analogues of the anti-tumour drug 2-[N-(hydroxymethyl)methylamino]-4,6-bis(dimethylamino)-1,3,5-triazine (HMPMM) in which the OH or a dimethylamino group is replaced by a carbohydrate has been explored. Triazinyl beta-glycosides were readily prepared by reaction of sugars with trimethyl-triazinylammonium salts. These were made with one or two methylamino groups on the triazine for reaction with formaldehyde to give the cytotoxic NMeCH2OH group. However, reaction of the triazinyl glycosides with formaldehyde gave complex intractable mixtures. When the carbohydrate portion was changed to the fully protected 2,3,4,6-tetra-O-acetyl glucose a good yield of the 2-[N-(hydroxymethyl)methylamino]-4-(dimethylamino)-1,3,5-triazin-2 -yl tetra-O-acetyl beta-glucoside was obtained. However, de-acetylation using sodium methoxide also removed the N-CH2OH group. We are investigating protection of the base-sensitive N-CH2OH group as trialkylsilyl and benzyl ethers and are looking at de-acetylation methods that are more selective. We have prepared glycosides in which the sugar is joined through the oxygen of the NMeCH2OH group. Coupling of acetobromoglucose with HMPMM catalysed by silver salts was not successful. Although methyl and cyclohexyl derivatives of HMPMM may be produced in high yields by reaction of HMPMM with methyl and cyclohexyl alcohols under acidic catalysis, production of glycosides in this way gave poor yields. MNDO calculations on reactions of HMPMM helped us devise improved reaction conditions for the condensation of 2,3,4,6-tetra-O-acetyl glucose with HMPMM and its derivatives. The best procedure to generate one of the target glycosides is to react 2,3,4,6-tetra-O-acetyl glucose and formaldehyde with 2-methylamino-4,6-bis(dimethylamino)-1,3,5-triazine. The beta-glycoside product was de-acetylated using potassium carbonate in dry methanol.     

Covalent immobilization of ascorbate oxidase onto polycarbonate strip for l-ascorbic acid detection

Herein, a simple and rapid method is described for detection of l-ascorbic acid by ascorbate oxidase immobilized onto polycarbonate strip pre-activated by 1-fluoro-2-nitro-4-azidobenzene in photochemical reaction. Covalent attachment of ascorbate oxidase was confirmed by XPS studies. The immobilized-ascorbate oxidase shows higher pH, thermal and storage stability in comparison to free enzyme.     

Application of Firefly Algorithm for Load Frequency Control of Multi-area Interconnected Power System

Abstract—In this article, a firefly algorithm is proposed for load frequency control of multi-area power systems. Initially a two equal area non-reheat thermal system is considered and the optimum gains of the proportional integral/proportional integral derivative controller are optimized employing the firefly algorithm technique. The superiority of the proposed approach is demonstrated by comparing the results with some recently published techniques such as genetic algorithm, bacteria foraging optimization algorithm, differential evolution, particle swarm optimization, hybrid bacteria foraging optimization algorithm-particle swarm optimization, and Ziegler–Nichols-based controllers for the same interconnected power system. Further, the proposed approach is extended to a three-unequal-area thermal system considering generation rate constraint and governor dead-band. Investigations reveal on comparison that proportional integral derivative controller provides much better response compared to integral and proportional integral controllers. Additionally, robustness analysis is carried out by varying the operating load condition and time constants of speed governor, turbine, and inertia constant in the range of +50 to –50% from their nominal values as well as the size and position of step load perturbation to demonstrate the robustness of the proposed firefly algorithm optimized proportional integral derivative controller.     

Soil aquifer treatment using advanced primary effluent

Soil aquifer treatment (SAT) using primary effluent (PE) is an attractive option for wastewater treatment and reuse in many developing countries with no or minimal wastewater treatment. One of the main limitations of SAT of PE is rapid clogging of the infiltration basin due to high suspended solid concentrations. Some pre-treatment of PE before infiltration is likely to reduce this limitation, improve performance of SAT and help to implement this technology effectively. The effects of three pre-treatment options namely sedimentation (SED), coagulation (COAG) and horizontal roughing filtration (HRF) on SAT were analyzed by conducting laboratory-scale batch and soil column experiments. The sedimentation and coagulation pre-treatments led to less head loss development and reduction of clogging effect. The head loss development in soil column using PE + COAG and PE + SED was reduced by 85 and 72%, respectively, compared to PE alone without any pretreatment. The overall dissolved organic carbon (DOC) removal of pre-treatments and soil column collectively were 34, 44, 51 and 43.5% for PE without any pre-treatment, PE + SED, PE + COAG and PE + HRF, respectively. Coagulation pre-treatment of PE was found to be the most effective option in terms of suspended solids, DOC and nitrogen removal. Sedimentation pre-treatment of PE could be attractive where land is relatively less expensive for the construction of sedimentation basins.