Effect of extraction conditions on yield and degree of esterification of durian rind pectin: An experimental design

The effect of time (1 and 4 h), pH (2.0 and 2.5) and temperature (80 and 90 °C) on yield and degree of esterification (DE) of durian rind pectin was investigated. The yield and DE of the extracted pectin ranged from 2.1 to 10.3% (w/w, based on dry weight of durian rind) and 45.6–64.8% respectively. Yield was significantly affected by time, temperature and pH, and interactions between temperature and pH, and heating time and pH. DE was significantly affected by heating time and pH, and interactive effects of temperature and pH, and heating time and pH. The extraction yield was not related to DE. By considering pectin yield and DE, the acid extraction of durian rind pectin at 80 °C, for 4 h and at pH 2.5 could be suitable.     

Incorporating Nano-silica as a Binder to Improve Corrosion Resistance of High Alumina Refractory Castables

In this study, four types of castables as calcium-aluminate cement (CAC)-bonded and nano-silica (NS)-bonded castables based on tabular-alumina and bauxite aggregates were prepared to investigate the replacement of the calcium-aluminate cement by NS. All samples were allowed to dry at 110 °C then fired at 800 and 1200 °C. Bulk density and apparent porosity of samples were measured. The molten aluminum static corrosion test (cup test) results showed that NS-bonded specimens had higher resistance to corrosion compared to CAC-bonded samples (based on the measured average aluminum penetration depth into the refractory texture). However no penetration was observed in bauxite NS-bonded samples. The results were consistent with dynamic corrosion test in aluminum melt carried out at 800 °C for 100 h. The small pore size in NS-bonded castables was found to be the main cause for high corrosion resistance as micro-pores prevented the melt to penetrate into the refractory.     

Formulation and release of doxycycline HCL from an ion activated in situ gelling delivery system for the treatment of periodontal disease

This study reports on the formulation of doxycycline HCL in an ion activated in situ gelling delivery system and its implications for the treatment of periodontal disease. The system is based on the use of alginate as the gelling agent and hydroxypropyl methylcellulose (HPMC) as a viscosity enhancing agent. The ion activated gelling mechanism in this system is based on the concept of interaction with the divalent calcium ions present in the gingival crevicular fluid (GCF). The gelling capacity of the prepared formulations was assessed visually and by investigating their rheological behavior upon mixing with human blood serum since it has the same composition as the GCF. The rheological behavior of all formulations was not affected by incorporation of the drug. In vitro release studies showed that the alginate/HPMC mixture, upon gelling after mixing with serum, can sustain the release of doxycycline HCL for an extended period of time which was more than 12 days. These results indicated that this system can be used as an in situ gelling local delivery system for the treatment of periodontal disease. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Identifying the period of a step change in high‐yield processes

Quality control charts have proven to be very effective in detecting out‐of‐control states. When a signal is detected a search begins to identify and eliminate the source(s) of the signal. A critical issue that keeps the mind of the process engineer busy at this point is determining the time when the process first changed. Knowing when the process first changed can assist process engineers to focus efforts effectively on eliminating the source(s) of the signal. The time when a change in the process takes place is referred to as the change point. This paper provides an estimator for a period of time in which a step change in the process non‐conformity proportion in high‐yield processes occurs. In such processes, the number of items until the occurrence of the first non‐conforming item can be modeled by a geometric distribution. The performance of the proposed model is investigated through several numerical examples. The results indicate that the proposed estimator provides a reasonable estimate for the period when the step change occurred at the process non‐conformity level. Copyright © 2009 John Wiley & Sons, Ltd.     

Influence and mechanism of dissolved oxygen on the performance of Ammonia-Oxidation Microbial Fuel Cell

Based on inorganic fuel, an Ammonia-Oxidation Microbial Fuel Cell (AO-MFC) had been developed, and the influence and mechanism of dissolved oxygen (DO) on the performance of nitrification and electricity generation were investigated. The results showed that the maximum conversion percentage of ammonium–nitrogen (NH₄⁺–N) was 99.7%. The output voltage and the power density were 98.5 ± 1.41 mV and 9.70 ± 0.27 mW m⁻² in the stable phase of electricity generation. In the AO-MFC, the electrons originated from ammonia and flowed to ammonia monooxygenase (AMO, which catalyzes the conversion of ammonia to hydroxylamine), Cyt aa₃ oxidase (which catalyzes the reduction of oxygen) and electrode, which were used for triggering ammonia oxidation, synthesizing ATP and generating electricity. Molecular oxygen played a key role in the electron distribution among these three acceptors. DO concentration too high (>6.45 mg L⁻¹) or too low (<0.5 mg L⁻¹) could exert a great negative influence on the performance of electricity generation.     

An innovative method of die design and evaluation of flow balance for thermoplastics extrusion profiles

In this article, a computational and experimental method for flow balancing of a U‐shaped die profile with nonuniform thicknesses is presented. The approach was to implement a flow restricting mechanism along the melt flow path. A parametric study based on the restrictor dimensions was carried out to attain a preliminary optimal design. Simulations were performed using Fluent software to analyze the flow velocity at the die exit. Experimental study was then carried out at various restrictor positions for the purpose of attaining a desirable flow balance. The velocity at various segments of the die exit was measured utilizing an innovative procedure by implementing the “separating blades.” Experimental findings were compared with those of simulations which showed an acceptable agreement. The results suggest that a flexible die can be designed to achieve a flow balance under various processing conditions. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Six-Phase Voltage Source Inverter Driven Induction Motor

A six-phase six-step voltage-fed induction motor is presented. The inverter is a transistorized six-step voltage source inverter, while the motor is a modified standard three-phase squirrel-cage motor. The stator is rewound with two three-phase winding sets displaced from each other by 30 electrical degrees. A model for the system is developed to simulate the drive and predict its performance. The simulation results for steady-state conditions and experimental measurements show very good correlation. It is shown that this winding configuration results in the elimination of all air-gap flux time harmonics of the order (6v ±1, v = 1,3,5,...). Consequently, all rotor copper losses produced by these harmonics as well as all torque harmonics of the order (6v, v = 1,3,5,...) are eliminated. A comparison between-the measured instantaneous torque of both three-phase and six-phase six-step voltage-fed induction machines shows the advantage of the six-phase system over the three-phase system in eliminating the sixth harmonic dominant torque ripple.     

同构计算环境中一种新的静态任务调度算法

延伸了TTIG模型并提出新的算法．在模拟实验中，将此算法与MATE和其它同构环境中基于DAG的调度算法，在不同测试条件下进行了比较，结果显示该算法性能明显优于MATE，与基于DAG模型的调度算法比较而言，在性能方面各有千秋，但在算法时间复杂度方面具有显著的优势．     

The prediction of the combustion and heat transfer performance of a refinery heater

Predictions have been obtained for the flow, combustion, and heat transfer within a refinery process heater. The flow and combustion in the highly three-dimensional geometry are handled by a numerical solution technique and physical modeling which have an estab;ished two-dimensional predictive history. The radiation transfer is handled by the more recent and very flexible “discrete transfer” technique. Special grids and computational procedures are employed in the interests of computational economy, with the burner region and the main combustion chamber region being handled in separate subcodes. The predictions of the wall heat transfer distribution are compared with measurements and the agreement is remarkably good.