Showing papers by "Nanyang Technological University published in 2008"
TL;DR: Hollow micro-/nanostructures are of great interest in many current and emerging areas of technology as discussed by the authors, and a comprehensive overview of synthetic strategies for hollow structures is presented.
Abstract: Hollow micro-/nanostructures are of great interest in many current and emerging areas of technology. Perhaps the best-known example of the former is the use of fly-ash hollow particles generated from coal power plants as partial replacement for Portland cement, to produce concrete with enhanced strength and durability. This review is devoted to the progress made in the last decade in synthesis and applications of hollow micro-/nanostructures. We present a comprehensive overview of synthetic strategies for hollow structures. These strategies are broadly categorized into four themes, which include well-established approaches, such as conventional hard-templating and soft-templating methods, as well as newly emerging methods based on sacrificial templating and template-free synthesis. Success in each has inspired multiple variations that continue to drive the rapid evolution of the field. The Review therefore focuses on the fundamentals of each process, pointing out advantages and disadvantages where appropriate. Strategies for generating more complex hollow structures, such as rattle-type and nonspherical hollow structures, are also discussed. Applications of hollow structures in lithium batteries, catalysis and sensing, and biomedical applications are reviewed.
2,767 citations
TL;DR: This review critically identifies the shortcomings in current research on LDHs, such as the common weaknesses in the adopted methodology, discrepancies among reported results and ambiguous conclusions.
1,445 citations
TL;DR: In this article, Zhao et al. used uniaxial tensile strain to tune the 2D and G bands of graphene and obtained a band gap opening of ∼300 meV under 1% tensile tensile stress.
Abstract: Graphene was deposited on a transparent and flexible substrate, and tensile strain up to ∼0.8% was loaded by stretching the substrate in one direction. Raman spectra of strained graphene show significant red shifts of 2D and G band (−27.8 and −14.2 cm−1 per 1% strain, respectively) because of the elongation of the carbon−carbon bonds. This indicates that uniaxial strain has been successfully applied on graphene. We also proposed that, by applying uniaxial strain on graphene, tunable band gap at K point can be realized. First-principle calculations predicted a band-gap opening of ∼300 meV for graphene under 1% uniaxial tensile strain. The strained graphene provides an alternative way to experimentally tune the band gap of graphene, which would be more efficient and more controllable than other methods that are used to open the band gap in graphene. Moreover, our results suggest that the flexible substrate is ready for such a strain process, and Raman spectroscopy can be used as an ultrasensitive method to ...
1,367 citations
TL;DR: In this article, Raman spectroscopy and imaging can be used as a quick and unambiguous method to determine the number of layers of a single-layer graphite compared to graphite.
Abstract: Graphene has many unique properties that make it an ideal material for fundamental studies as well as for potential applications. Here we review recent results on the Raman spectroscopy and imaging of graphene. We show that Raman spectroscopy and imaging can be used as a quick and unambiguous method to determine the number of graphene layers. The strong Raman signal of single layer graphene compared to graphite is explained by an interference enhancement model. We have also studied the effect of substrates, the top layer deposition, the annealing process, as well as folding (stacking order) on the physical and electronic properties of graphene. Finally, Raman spectroscopy of epitaxial graphene grown on a SiC substrate is presented and strong compressive strain on epitaxial graphene is observed. The results presented here are highly relevant to the application of graphene in nano-electronic devices and help in developing a better understanding of the physical and electronic properties of graphene.
1,157 citations
TL;DR: Nonylphenol is a toxic xenobiotic compound classified as an endocrine disrupter capable of interfering with the hormonal system of numerous organisms and is found often in matrices such as sewage sludge, effluents from sewage treatment works, river water and sediments, soil and groundwater.
1,047 citations
15 Sep 2008
TL;DR: This paper reviews the ten-year development of the work presented at the ISMAR conference and its predecessors with a particular focus on tracking, interaction and display research, providing a roadmap for future augmented reality research.
Abstract: Although Augmented Reality technology was first developed over forty years ago, there has been little survey work giving an overview of recent research in the field. This paper reviews the ten-year development of the work presented at the ISMAR conference and its predecessors with a particular focus on tracking, interaction and display research. It provides a roadmap for future augmented reality research which will be of great value to this relatively young field, and also for helping researchers decide which topics should be explored when they are beginning their own studies in the area.
1,040 citations
TL;DR: In this paper, a combined experimental and theoretical study on the effective thermal conductivity and viscosity of nanofluids is conducted and two static mechanisms-based models are presented to predict the enhanced thermal conductivities of nanoparticles having spherical and cylindrical nanoparticles.
968 citations
TL;DR: In this article, the authors attempted to offer a better understating of representative biosorption isotherms, kinetics and thermodynamics with special focuses on theoretical approaches for derivation of combined Langmuir-Freundlich isotherm as well as the pseudo-first-and second-order kinetic equations and general rate law equation.
917 citations
TL;DR: The proposed enhanced I-ELM works for the widespread type of piecewise continuous hidden nodes and is proposed as a universal approximator for constructive feedforward networks.
867 citations
TL;DR: In this paper, an empirical formula is proposed for the calculation of the viscosity of glycerol−water mixture for mass concentrations in the range of 0−100% and temperatures varying from 0 to 100 °C.
Abstract: An empirical formula is proposed for the calculation of the viscosity of glycerol−water mixture for mass concentrations in the range of 0−100% and temperatures varying from 0 to 100 °C. It compares well with three databases available in the literature, and its application procedure is also simpler than other previously developed correlations.
769 citations
TL;DR: An up-to-date review on recent research development in aerobic biogranulation technology and applications in treating toxic industrial and municipal wastewaters and attempts to shed light on the fundamental understanding in aerobic granulation by newly employed confocal laser scanning microscopic techniques and microscopic observations of granules.
TL;DR: The aim of these applications is to improve the mechanical properties of soil so that it will be more suitable for construction or environmental purposes, and two notable applications, bioclogging and biocementation, have been explored.
Abstract: Microbial Geotechnology is a new branch of geotechnical engineering that deals with the applications of microbiological methods to geological materials used in engineering. The aim of these applications is to improve the mechanical properties of soil so that it will be more suitable for construction or environmental purposes. Two notable applications, bioclogging and biocementation, have been explored. Bioclogging is the production of pore-filling materials through microbial means so that the porosity and hydraulic conductivity of soil can be reduced. Biocementation is the generation of particle-binding materials through microbial processes in situ so that the shear strength of soil can be increased. The most suitable microorganisms for soil bioclogging or biocementation are facultative anaerobic and microaerophilic bacteria, although anaerobic fermenting bacteria, anaerobic respiring bacteria, and obligate aerobic bacteria may also be suitable to be used in geotechnical engineering. The majority of the studies on Microbial Geotechnology at present are at the laboratory stage. Due to the complexity, the applications of Microbial Geotechnology would require an integration of microbiology, ecology, geochemistry, and geotechnical engineering knowledge.
TL;DR: In this article, the effect of substrate on the atomic/electronic structures of monolayer graphene is investigated and it is shown that the Raman features are independent of the substrate used.
Abstract: Graphene has attracted a lot of interest for fundamental studies as well as for potential applications. Till now, micromechanical cleavage (MC) of graphite has been used to produce high-quality graphene sheets on different substrates. Clear understanding of the substrate effect is important for the potential device fabrication of graphene. Here we report the results of the Raman studies of micromechanically cleaved monolayer graphene on standard SiO2 (300 nm)/Si, single crystal quartz, Si, glass, polydimethylsiloxane (PDMS), and NiFe. Our data suggests that the Raman features of monolayer graphene are independent of the substrate used; in other words, the effect of substrate on the atomic/electronic structures of graphene is negligible for graphene made by MC. On the other hand, epitaxial monolayer graphene (EMG) on SiC substrate is also investigated. Significant blueshift of Raman bands is observed, which is attributed to the interaction of the graphene sheet with the substrate, resulting in the change o...
TL;DR: In this paper, the authors reviewed and updated the development, understanding, and achievements of the LSM-based materials in solid oxide fuel cell (SOFC), and in particular the relation between the microstructure, their properties (electrical, thermal, mechanical, chemical, and interfacial), and electrochemical performance and performance stability.
Abstract: The high-temperature solid oxide fuel cell (SOFC) is the most efficient and environmentally friendly energy conversion technology to generate electricity from fuels such as hydrogen and natural gas as compared to the traditional thermal power generation plants. In the last 20–30 years, there has been significant progress in the materials development and stack technologies in SOFC. Among the electrode materials, lanthanum strontium manganite (LSM) perovskites, till today, are the most investigated and probably the most important electrode materials in SOFCs. The objective of this article is to review and update the development, understanding, and achievements of the LSM-based materials in SOFC. The structure, nonstoichiometry, defect model, and in particular the relation between the microstructure, their properties (electrical, thermal, mechanical, chemical, and interfacial), and electrochemical performance and performance stability are critically reviewed. Finally, challenges and prospects of LSM-based materials as cathodes for intermediate and low-temperature SOFCs are discussed.
TL;DR: In this paper, various aspects of nanofluids including synthesis, potential applications, experimental and analytical studies on the effective thermal conductivity, effective thermal diffusivity, convective heat transfer, and electrokinetic properties are critically reviewed.
24 Aug 2008
TL;DR: This paper proposes a novel context-aware query suggestion approach which is in two steps, and outperforms two baseline methods in both coverage and quality of suggestions.
Abstract: Query suggestion plays an important role in improving the usability of search engines. Although some recently proposed methods can make meaningful query suggestions by mining query patterns from search logs, none of them are context-aware - they do not take into account the immediately preceding queries as context in query suggestion. In this paper, we propose a novel context-aware query suggestion approach which is in two steps. In the offine model-learning step, to address data sparseness, queries are summarized into concepts by clustering a click-through bipartite. Then, from session data a concept sequence suffix tree is constructed as the query suggestion model. In the online query suggestion step, a user's search context is captured by mapping the query sequence submitted by the user to a sequence of concepts. By looking up the context in the concept sequence sufix tree, our approach suggests queries to the user in a context-aware manner. We test our approach on a large-scale search log of a commercial search engine containing 1:8 billion search queries, 2:6 billion clicks, and 840 million query sessions. The experimental results clearly show that our approach outperforms two baseline methods in both coverage and quality of suggestions.
TL;DR: This article studied managers' risk-taking behavior and how it is affected by equity-based compensation and found that managers lower firm risk by 6% in response to an exogenous increase in takeover protection in Delaware during the mid-1990s.
Abstract: I study managers' risk-taking behavior and how it is affected by equity-based compensation. I find that in response to an exogenous increase in takeover protection in Delaware during the mid-1990s, managers lower firm risk by 6%. I also find that the decrease in firm risk is concentrated among firms with low managerial equity-based incentives, in particular, firms with low CEO portfolio sensitivity to stock return volatility. Furthermore, firms respond to the increased protection accorded by the regime shift by providing managers with greater incentives for risk-taking.
TL;DR: In this article, the Raman spectroscopy was used to study the structure of epitaxial graphene (EG) and its interaction with SiC substrate, which was attributed to the compressive strain induced by the substrate.
Abstract: The fabrication of epitaxial graphene (EG) on SiC substrate by annealing has attracted a lot of interest as it may speed up the application of graphene for future electronic devices The interaction of EG and the SiC substrate is critical to its electronic and physical properties In this work, the Raman spectroscopy was used to study the structure of EG and its interaction with SiC substrate All the Raman bands of EG blueshift from that of bulk graphite and graphene made by micromechanical cleavage, which was attributed to the compressive strain induced by the substrate A model containing $13\ifmmode\times\else\texttimes\fi{}13$ honeycomb lattice cells of graphene on carbon nanomesh was constructed to explain the origin of strain The lattice mismatch between graphene layer and substrate causes the compressive stress of $227\phantom{\rule{03em}{0ex}}\mathrm{GPa}$ on graphene We also demonstrate that the electronic structures of EG grown on Si- and C-terminated SiC substrates are quite different Our experimental results shed light on the interaction between graphene and SiC substrate, which are critical to the future applications of EG
TL;DR: This article examined and reviewed the existing research on students' questions and explored ways of advancing future work into this area, highlighting the importance and role of student's questions from the perspectives of both the learner and the teacher.
Abstract: Students' questions play an important role in meaningful learning and scientific inquiry. They are a potential resource for both teaching and learning science. Despite the capacity of students' questions for enhancing learning, much of this potential still remains untapped. The purpose of this paper, therefore, is to examine and review the existing research on students' questions and to explore ways of advancing future work into this area. The paper begins by highlighting the importance and role of students' questions from the perspectives of both the learner and the teacher. It then reviews the empirical research on students' questions, with a focus on four areas: (1) the nature and types of these questions; (2) the effects of teaching students questioning skills; (3) the relationship between students' questions and selected variables; and (4) teachers' responses to, and students' perceptions of, students' questions. Following this, some issues and implications of students' questions for classroom instru...
TL;DR: A theoretical model of the displacement measurement accuracy of DIC can be accurately predicted based on the variance of image noise and Sum of Square of Subset Intensity Gradients (SSSIG), which leads to a simple criterion for choosing an optimal subset size for the DIC analysis.
Abstract: Digital Image Correlation (DIC) has been established as a flexible and effective technique to measure the displacements on specimen surface by matching the reference subsets in the undeformed image with the target subsets in the deformed image. With the existing DIC techniques, the user must rely on experience and intuition to manually define the size of the reference subset, which is found to be critical to the accuracy of measured displacements. In this paper, the problem of subset size selection in the DIC technique is investigated. Based on the Sum of Squared Differences (SSD) correlation criterion as well as the assumption that the gray intensity gradients of image noise are much lower than that of speckle image, a theoretical model of the displacement measurement accuracy of DIC is derived. The theoretical model indicates that the displacement measurement accuracy of DIC can be accurately predicted based on the variance of image noise and Sum of Square of Subset Intensity Gradients (SSSIG). The model further leads to a simple criterion for choosing a proper subset size for the DIC analysis. Numerical experiments have been performed to validate the proposed concepts, and the calculated results show good agreements with the theoretical predictions.
TL;DR: In this article, the authors examined the attitudes towards use of computers among pre-service teachers and found significant associations between years of computer use and level of confidence, and computer attitudes among teachers.
Abstract: The aim of this study is to examine the attitudes towards use of computers among pre-service teachers. A sample of 139 pre-service teachers was assessed for their computer attitudes using a Likert type questionnaire with four factors: affect (liking), perceived usefulness, perceived control, and behavioural intention to use the computer. The results of this study showed no gender or age differences among pre-service teachers on computer attitudes. However, there were significant differences for computer attitudes by the subject areas that pre-service teachers had been trained during their university education: Humanities, Sciences, Languages and General (Primary). Correlation analyses revealed significant associations between years of computer use and level of confidence, and computer attitudes. Implications for teacher training and suggestions for further research are provided.
TL;DR: In this paper, a new, slack, and uniformly porous TiO2 material is synthesized by a simple, carbon nanotube (CNT) template-assisted hydrothermal method and further explored for protein immobilization and biosensing.
Abstract: A new, slack, and uniformly porous TiO2 material is synthesized by a simple, carbon nanotube (CNT) template-assisted hydrothermal method and is further explored for protein immobilization and biosensing. Results demonstrate that the material has a large specific surface area and a unique nanostructure with a uniform pore-size distribution. Glucose oxidase (GOD) immobilized on the material exhibits facile, direct electrochemistry and good electrocatalytic performance without any electron mediator. The fabricated glucose oxidase sensor shows good stability and high sensitivity, which indicates that the slack porous TiO2 is an attractive material for use in the fabrication of biosensors, particularly enzymatic sensors, because of its direct electrochemistry, high specific surface area, and unique nanostructure for efficient immobilization of biomolecules.
TL;DR: In this paper, uniform crystalline WO3 nanorods and their assembly without any surfactants were synthesized by using a facile hydrothermal process without employing lithium ions and sulfates.
Abstract: We report the synthesis of uniform crystalline WO3 nanorods and their assembly without any surfactants. WO3 nanorods have been synthesized by using a facile hydrothermal process without employing lithium ions and sulfates. Transparent WO3 nanorod film has been prepared by assembled coating of the as-synthesized WO3 nanorods suspension onto ITO coated glass. It is found that the assembly was not affected by the surface properties of substrates, but dependent on the drying rate of the film, the concentration of suspension, and the aspect ratio of nanorods. The assembly process is proposed to follow an aggregation−deposition mechanism. The resulting WO3 nanorod film exhibits high electrochromic stability and comparable color display, contrast, and coloration/bleaching response.
TL;DR: A large-scale self-etching approach for the synthesis of monodispersed mesoporous F-TiO2 hollow microspheres exhibited ease for the concurrent membrane filtration and photocatalysis, providing high potential for engineering application in advanced water treatment.
Abstract: We report a large-scale self-etching approach for the synthesis of monodispersed mesoporous F−TiO2 hollow microspheres. The self-etching derived from HF was elucidated by the morphology, chemical composition, and crystal size evolutions from solid to hollow microspheres with the increase in the concentration of H2SO4. The resulting TiO2 hollow microspheres exhibited ease for the concurrent membrane filtration and photocatalysis, providing high potential for engineering application in advanced water treatment, for not only increasing water production but also improving water quality.
TL;DR: A novel bioassay strategy is designed to detect small-molecule targets such as cocaine, potassium, and adenosine, based on gold nanoparticles (AuNPs) and engineered DNA aptamers, which is shown to be generic and applicable to the detection of several other small-mitecule targets.
Abstract: A novel bioassay strategy is designed to detect small-molecule targets such as cocaine, potassium, and adenosine, based on gold nanoparticles (AuNPs) and engineered DNA aptamers. In this design, an aptamer is engineered to be two pieces of random, coil-like single-stranded DNA, which reassembles into the intact aptamer tertiary structure in the presence of the specific target. AuNPs can effectively differentiate between these two states via their characteristic surface-plasmon resonance-based color change. Using this method, cocaine in the low-micromolar range is selectively detected within minutes. This strategy is also shown to be generic and applicable to the detection of several other small-molecule targets.
TL;DR: A unique nanostructured polyaniline (PANI)/mesoporous TiO(2) composite was synthesized and explored as an anode in Escherichia coli microbial fuel cells and has great potential to be used as the anode for a high-power MFC and may also provide a new universal approach for improving different types of MFCs.
Abstract: A unique nanostructured polyaniline (PANI)/mesoporous TiO(2) composite was synthesized and explored as an anode in Escherichia coli microbial fuel cells (MFCs). The results of X-ray diffraction, morphology, and nitrogen adsorption-desorption studies demonstrate a networked nanostructure with uniform nanopore distribution and high specific surface area of the composite. The composite MFC anode was fabricated and its catalytic behavior investigated. Optimization of the anode shows that the composite with 30 wt % PANI gives the best bio- and electrocatalytic performance. A possible mechanism to explain the excellent performance is proposed. In comparison to previously reported work with E. coli MFCs, the composite anode delivers 2-fold higher power density (1495 mW/m(2)). Thus, it has great potential to be used as the anode for a high-power MFC and may also provide a new universal approach for improving different types of MFCs.
TL;DR: The contributions of individual components in extracellular polymeric substances (EPSs) on structural stability of phenol-fed, aerobic granules were examined via their selective hydrolysis using enzymes and the structural changes of granule were probed using in situ fluorescent staining and confocal laser scanning microscopy.
TL;DR: Experimental results show that composite dispatching rules generated by the genetic programming framework outperforms the single dispatches rules and composite dispatch rules selected from literature over five large validation sets with respect to minimum makespan, mean tardiness, and mean flow time objectives.
TL;DR: It is shown that AdaBoost incorporating properly designed RBFSVM (SVM with the RBF kernel) component classifiers, which is called AdaBoostSVM, can perform as well as SVM and demonstrates better generalization performance than SVM on imbalanced classification problems.
TL;DR: The reconstructed images illustrate improvement in identification of embedded malignant tumors over the delay-and-sum algorithm and successful detection and localization of tumors as small as 2 mm in diameter are demonstrated.
Abstract: A new image reconstruction algorithm, termed as delay-multiply-and-sum (DMAS), for breast cancer detection using an ultra-wideband confocal microwave imaging technique is proposed. In DMAS algorithm, the backscattered signals received from numerical breast phantoms simulated using the finite-difference time-domain method are time shifted, multiplied in pair, and the products are summed to form a synthetic focal point. The effectiveness of the DMAS algorithm is shown by applying it to backscattered signals received from a variety of numerical breast phantoms. The reconstructed images illustrate improvement in identification of embedded malignant tumors over the delay-and-sum algorithm. Successful detection and localization of tumors as small as 2 mm in diameter are also demonstrated.