Process Optimization by Response Surface Methodology and Characteristics Investigation of Corn Extrudate Fortified with Yam (Dioscorea alata L.)

Response surface methodology was used to investigate the optimum operation conditions of a single screw extruder and to analyze the effects of extrusion processing variables, including yam flour contents (10–30 %), moisture content (10–18 %), and screw speed (250–350 rpm) on characteristics of the corn–yam extrudates. Quadratic polynomial equations were also obtained by multiple regression analysis. The predicted models were adequate based on the lack-of-fit test and coefficient of determination obtained. By superimposing individual contour plots of the different responses, regions meeting the optimum conditions were also derived. The moisture content had critical effect on all responses variables. All the characteristic of the corn–yam extrudates evaluated were significantly affected by three process variables. Feed moisture content was the most significant variable with on most of characteristics. Increasing moisture content caused increase in bulk density, water absorption index and hardness, but decrease in radial expansion ratio. However, graphical optimization studies resulted in 21–23 %, 12–13 %, and 305–320 rpm of yam flour level, moisture content, and screw speed, respectively. The results suggested that corn extrudates fortified with yam produced by using the single-screw extruder are suitable for snack food development.     

Formation mechanism of LiFePO4/C composite powders investigated by X-ray absorption spectroscopy

The local structure and oxidation states for both the precursors and the LiFePO₄/C composite powders were investigated by X-ray absorption spectroscopy (XAS) to provide a deep insight into their formation mechanism. It was found that the local structure and oxidation states of the precursors and the synthesized LiFePO₄/C powders as well as the electrochemical properties of the synthesized powders were strongly influenced by the R ratio (R: molar ratio of citric acid to total metal ions). The oxidation states of iron ions of the precursors for R = 1 and 0.75 consist mainly of Fe(II) and traces of Fe(III). However, the oxidation state of iron ions of the precursor for R = 0.5 comprises mainly of Fe(III). The oxidation state of iron ions of all the synthesized powders is Fe(II). The structure of the precursors and the synthesized powders for R = 1 and 0.75 is more ordering than that for R = 0.5. It is in good agreement with the observation of the cation mixing obtained from the Riteveld analysis of the XRD data. The better the electrochemical performance is, the more ordering the structure or the less the cation mixing. However, the effect of the R values on the carbon content is also essential for the electrochemical properties of the synthesized LiFePO₄/C composite powders. Increasing the carbon content leads to the increase in the electronic conductivity but impedes the Li⁺ ion diffusion of the composite materials. Consequently, the powders synthesized at the optimal R ratio of 0.75 exhibited the highest initial capacity, about 150 mAh g⁻¹ when cycled at 1/40 C rate at room temperature. The structural scheme of the precursors and the synthesized powders and the formation mechanism of the LiFePO₄/C composite powders are also addressed in this work.     

Template-free reverse micelle process for the synthesis of a rod-like LiFePO4/C composite cathode material for lithium batteries

The synthesis of rod-like LiFePO₄/C cathodes using template-free reverse micelle process is reported for high performance lithium batteries. We have demonstrated that the size of the primary particles could be controlled based on sintering temperature and sintering time and size of the large aggregates is adjustable based on the carbon content of the sample. Thermogravimetry and differential thermal analysis have been used to propose a possible mechanism for the formation rod-like LiFePO₄/C cathode material. X-ray diffraction, scanning electron microscopy, impedance spectroscopy and charge-discharge measurements have been used to characterize the material. Electrochemical performance of rod-like LiFePO₄/C cathode material offers higher initial capacity and excellent rate capability than that obtained by loose porous LiFePO₄/C material due to unique rod-like composite material formed by primary nanoparticles. Hence, it can be suggested that that the rod-like nanostructured morphology improves structural stability, lithium ion diffusion and electronic conductivity of the LiFePO₄/C composite material. The template-free reverse micelle process for the synthesis of the rod-like LiFePO₄/C cathode material opens up a new route to synthesize lithium transition metal oxides with controlled morphologies for applications in high power lithium batteries.     

Composition of flavonoids and phenolic acids in Glycin tomentella Hayata cultivated in various soils

A high-performance liquid chromatography (HPLC) method was developed to simultaneously separate 12 phenolic acids and 21 flavonoids. The separation was performed with a C₁₈ column and a binary gradient solvent system consisting of methanol and water with 9% glacial acetic acid. The peak resolutions (Rs) were 0.51–12.41 and separation factors (α) were all higher than 1. The method was used to survey these phenolic components in Glycin tomentella Hayata. Diadzein was the major flavonoid in the leaves and roots, and gentisic acid and ferulic acid were the major phenolic acids in the leaves. Amounts of phenolic acids and flavonoids in the leaves from varied soil cultivations were in the order: loam > sand > red loamy sand. Flavonoid amounts in the roots also showed the same trend; however, phenolic acid amounts were low and did not present significant differences. Overall, the roots had much higher phenolic contents than the leaves.     

On the electrochemical impedance spectroscopy of direct methanol fuel cell

The direct methanol fuel cell (DMFC) was operated under a variety of current densities to monitor the electrochemical impedance spectroscopy (EIS) for understanding its reaction mechanism. Based on the EIS analysis, the impedance of the cell reaction is divided into three components, two of them are current dependent and the remainder is current independent. Through detailed exploration of the impedance components, the high-frequency impedance was attributed to interfacial behavior, the medium-frequency impedance to electrochemical reactions, and the low-frequency impedance to the adsorption/relaxation of CO. Based on EIS analysis, a qualitative model is proposed to delineate the reaction mechanisms of DMFC, which is confirmed quantitatively by one set of equivalent circuit elements. The experimental data are satisfactorily consistent with the results simulated from the proposed model.     

Numerical generation and grid controls of boundary‐fitted conformal grids in multiply connected regions

Based on the study of grid generation methods in a simply connected region (Int. J. Numer. Meth. Engng 1997; 40 :343), with the aid of a new transformation from a multiply connected region to a simply connected domain, the grid generation in a multiply connected domain is carried out in this paper. 2‐D conformal and orthogonal grids are generated in a multiply connected region, mostly involving a multiple‐blocks method developed in the present study. To avoid grid distortion on the degenerated boundary caused by physical singularities, controls of grids through specified points are implemented, without losing the conformal properties. Further applications of this grids‐controlling technique for points inside the region, the nested grids, and the multiple‐blocks method are introduced and discussed comprehensively. Numerical examples are taken to demonstrate the validity and applicability of the theorems. Copyright © 2006 John Wiley & Sons, Ltd.     

Citation analysis of Ted Nelson’s works and his influence on hypertext concept

This study investigates Ted Nelson’s works and the influence of his hypertext concept through citation analysis, including citation counting, characteristics of citing articles on language, document type, citing year, discipline, and citation content. The selection of the Nelson’s works was based on searching Library Literature & Information Science, Library and Information Science Abstracts, Google and Yahoo search engines. The citation data were compiled from the database of Web of Science. The results of the study reveal that hypertext has directly great impact on information retrieval and world wide web; therefore, the concept has had profound influence on information, library and computer science disciplines. Moreover, the influence of Nelson’s works spreads to other disciplines variously, especially on education, literature, business and economics, engineering, sociology, psychology, etc. The citation context analysis of citing articles on information and library science reveals that (1) definition, orientation and general introduction of hypertext; (2) relation of Vannevar Bush and Ted Nelson in terms of hypertext; (3) Nelson’s Xanadu system and its component of hypertext; (4) the application of hypertext in information science and library science are four most citing purpose.     

Enhanced performance for photocatalytic hydrogen evolution using MoS2/graphene hybrids

A MoS₂/graphene hybrid (MSG) is synthesized by microwave hydrothermal method. Both of the charge transfer resistance and the photocurrent are tuned in graphene modified MoS₂ by enhancing photocatalytic nature, where the charge transfer resistance significantly decreases from 36,000 Ω–8.49 Ω and the photocurrent promotes from 0.29 mA cm^?2 to 16.47 mA cm^?2. In this article, the result reveals that the appropriate modification of graphene can reach the maximum yield of hydrogen gas. In addition, the appropriate conditions, such as the concentration of 0.32 M formic acid and the MoS₂ photocatalyst with 0.8 wt% graphene (MSG_0.8) dose of 0.013 g L^?1, can complete the outstanding photocatalytic hydrogen evolution, where the hydrogen evolution using MSG_0.8 composite photocatalyst has the maximum yield of 667.2 μmol h^?1 g^?1.     

Integrating process and power grid models for optimal design and demand response operation of giga-scale green hydrogen

Electrolysis-based hydrogen production can play a significant role in industrial decarbonization, and its economic competitiveness can be promoted by designing demand response operating schemes. Nevertheless, the scale of industrial supply plants may be significantly large (on the order of gigawatts), meaning that electricity prices cannot be treated as an input for scheduling problems, that is, the “price taker” approach. This article presents a framework for the optimization of a large-scale, electricity-powered hydrogen production facility considering its integration with the power grid. Using a computational case study, we present an iterative scheme for integrating the process model with a model for power grid optimization and capacity expansion, taking the popular GenX model as an example.