The importance of catalyst oxidation for the growth of carbon nanotubes on Si substrates

Iron catalyst in the form of a thin layer was deposited directly onto silicon wafers in order to grow carbon nanotubes by a chemical vapor deposition process. The chemical and morphological transformations undergone during the process by the iron were monitored in situ by photoelectron spectroscopy and ex situ by SEM. We found that the growth of carbon nanotubes was successful only when the iron catalyst was previously oxidized. Metallic iron transformed to embedded iron silicide structures, unable to initiate nanotube growth. On the other hand, pre-oxidized iron led to the formation of superficial particles and showed only a partial conversion to silicide, which resulted in carbon nanotube growth, even at very low pressures.     

An accurate penalty-based approach for reliability-based design optimization

A typical reliability-based design optimization (RBDO) problem is usually formulated as a stochastic optimization model where the performance of a system is optimized with the reliability requirements being satisfied. Most existing RBDO methods divide the problem into two sub-problems: one relates to reliability analysis, the other relates to optimization. Traditional approaches nest the two sub-problems with the reliability analysis as the inner loop and the optimization as the outer loop. Such nested approaches face the challenge of prohibitive computational expense that drives recent research focusing on decoupling the two loops or even fundamentally transforming the two-loop structure into one deterministic optimization problem. While promising, the potential issue in these computationally efficient approaches is the lowered accuracy. In this paper, a new decoupled approach, which performs the two loops sequentially, is proposed. First, a deterministic optimization problem is solved to locate the means of the uncertain design variables. After the mean values are determined, the reliability analysis is performed. A new deterministic optimization problem is then restructured with a penalty added to each limit-state function to improve the solution iteratively. Most existing research on decoupled approaches linearizes the limit-state functions or introduces the penalty into the limit-state functions, which may suffer the approximation error. In this research, the penalty term is introduced to change the right hand side (RHS) value of the deterministic constraints. Without linearizing or transforming the formulations of limit-state function, this penalty-based approach effectively improves the accuracy of RBDO. Comparison experiments are conducted to illustrate how the proposed method obtains improved solutions with acceptable computational cost when compared to other RBDO approaches collected from literature.     

PAN‐based fibers modified with two‐component ceramic nanoparticles

The authors determined conditions for manufacturing PAN precursor fibers containing a system of two nanoadditives, montmorillonite (MMT), and hydroxyapatite (HAp) in their structure. The PAN precursor fibers thus obtained are characterized by a tenacity of more than 30 cN/tex and a total volume of pores at the level of 0.29 cm³/g. Furthermore, it was found that the use of nanoadditives entails the remodeling of the paracrystalline structure of PAN fibers into a strictly crystalline one. This is accompanied by a decrease in spacing between MMT layers combined with their partial exfoliation. The fibers thus obtained, after being carbonized, will be used for medical applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Estimation of water diffusivity parameters on grape dynamic drying

A computer program was developed, aiming at estimating water diffusivity parameters in a dynamic drying process with grapes, assessing the predictability of corresponding non-isothermal drying curves. It numerically solves Fick’s second law for a sphere, by explicit finite differences, in a shrinking system, with anisotropic properties and changing boundary conditions.     

‘Disruptive technologies’, ‘pedagogical innovation’: What’s new? Findings from an in-depth study of students’ use and perception of technology

The paper describes the findings from a study of students’ use and experience of technologies. A series of in-depth case studies were carried out across four subject disciplines, with data collected via survey, audio logs and interviews. The findings suggest that students are immersed in a rich, technology-enhanced learning environment and that they select and appropriate technologies to their own personal learning needs. The findings have profound implications for the way in which educational institutions design and support learning activities.     

Influence of oak woods of different geographical origins on quality of wines aged in barriques and using oak chips

Wine ageing in wood barrels is a traditional practice in quality wine-making areas. It is generally believed that the organoleptic characteristics of wines aged in barrels are deeply influenced by wood geographical origin, as well as by age of barrels (new or used).     

A clock-free chip set for high-sampling rate adaptive filters

As digital signal processing systems become larger and clock rates increase, the typical design approach using global clock synchronization will become increasingly difficult. The application of asynchronous clock-free designs to high-performance digital signal processing systems is one promising approach to alleviating this problem. To demonstrate this approach for a typical signal processing task, the system architecture and circuit design of a chip set for implementing high-rate adaptive lattice filters using the asynchronous design techniques is presented.This research was sponsored in part by the Semiconductor Research Corporation and by DARPA.     

Those who were born poor: A qualitative study of Philippine poverty.

This qualitative study investigated the psychological experience of poverty among 2 groups of Filipinos who were interviewed about the effects of being raised poor, 12 who became rich, and 13 who remained poor. Using constructivist and critical theories as research paradigms and grounded theory as methodology, the results of the study illustrated perceived causes, coping mechanisms, and cultural factors. Surprisingly, both groups were very similar in their experiences of not having basic needs met, of negative emotions, and of generally attributing their poverty to familial circumstances. The ways of coping with poverty, such as receiving and giving assistance and imploring God for help, and the cultural features of perseverance (pagpupunyagi) and reliance on others (pakikipagkapwa) were similarly influential in both groups. Because the main difference between both groups is the occurrence of chance events that provided access to education and opportunities to emigrate for those who have become rich, the oppressive structures of a society that perpetuate poverty are discussed. In developing countries such as the Philippines, the psychological experience of poverty is characterized by the impossibility of upward mobility. (PsycINFO Database Record (c) 2010 APA, all rights reserved)