Nanyang Technological University

About: Nanyang Technological University is a education organization based out in Singapore, Singapore. It is known for research contribution in the topics: Computer science & Catalysis. The organization has 48003 authors who have published 112815 publications receiving 3294199 citations. The organization is also known as: NTU & Universiti Teknologi Nanyang.

Optimization models in emergency logistics: A literature review

Abstract: Optimization modeling has become a powerful tool to tackle emergency logistics problems since its first adoption in maritime disaster situations in the 1970s. Using techniques of content analysis, this paper reviews optimization models utilized in emergency logistics. Disaster operations can be performed before or after disaster occurrence. Short-notice evacuation, facility location, and stock pre-positioning are drafted as the main pre-disaster operations, while relief distribution and casualty transportation are categorized as post-disaster operations. According to these operations, works in the literature are broken down into three parts: facility location, relief distribution and casualty transportation, and other operations. For the first two parts, the literature is structured and analyzed based on the model types, decisions, objectives, and constraints. Finally, through the content analysis framework, several research gaps are identified and future research directions are proposed.

Construction of hierarchical Ni–Co–P hollow nanobricks with oriented nanosheets for efficient overall water splitting

Abstract: Complex nano-architectures with ordered two-dimensional (2D) building blocks are a class of promising electrocatalysts for different electrochemical technologies. In this work, a novel template-engaged strategy followed by sequential etching and phosphorization treatments is demonstrated to fabricate open and hierarchical Ni–Co–P hollow nanobricks (HNBs) via the assembly of oriented 2D nanosheets. Benefiting from the unique nano-architectures with large electrolyte-accessible surface and abundant mass diffusion pathways, the as-prepared Ni–Co–P HNBs exhibit high electrocatalytic activity, which affords the current density of 10 mA cm−2 at low overpotentials of 270 mV and 107 mV for oxygen and hydrogen evolution reactions respectively, and excellent stability in an alkaline medium. Remarkably, when used as both the anode and cathode, a low cell voltage of 1.62 V is required to reach the current density of 10 mA cm−2, making the Ni–Co–P HNBs an efficient bifunctional electrocatalyst for overall water splitting.

Machine Learning in Wireless Sensor Networks: Algorithms, Strategies, and Applications

Abstract: Wireless sensor networks (WSNs) monitor dynamic environments that change rapidly over time. This dynamic behavior is either caused by external factors or initiated by the system designers themselves. To adapt to such conditions, sensor networks often adopt machine learning techniques to eliminate the need for unnecessary redesign. Machine learning also inspires many practical solutions that maximize resource utilization and prolong the lifespan of the network. In this paper, we present an extensive literature review over the period 2002–2013 of machine learning methods that were used to address common issues in WSNs. The advantages and disadvantages of each proposed algorithm are evaluated against the corresponding problem. We also provide a comparative guide to aid WSN designers in developing suitable machine learning solutions for their specific application challenges.

SnO2‐Based Nanomaterials: Synthesis and Application in Lithium‐Ion Batteries

Abstract: The development of new electrode materials for lithium-ion batteries (LIBs) has always been a focal area of materials science, as the current technology may not be able to meet the high energy demands for electronic devices with better performance. Among all the metal oxides, tin dioxide (SnO₂) is regarded as a promising candidate to serve as the anode material for LIBs due to its high theoretical capacity. Here, a thorough survey is provided of the synthesis of SnO₂-based nanomaterials with various structures and chemical compositions, and their application as negative electrodes for LIBs. It covers SnO₂ with different morphologies ranging from 1D nanorods/nanowires/nanotubes, to 2D nanosheets, to 3D hollow nanostructures. Nanocomposites consisting of SnO₂ and different carbonaceous supports, e.g., amorphous carbon, carbon nanotubes, graphene, are also investigated. The use of Sn-based nanomaterials as the anode material for LIBs will be briefly discussed as well. The aim of this review is to provide an in-depth and rational understanding such that the electrochemical properties of SnO₂-based anodes can be effectively enhanced by making proper nanostructures with optimized chemical composition. By focusing on SnO₂, the hope is that such concepts and strategies can be extended to other potential metal oxides, such as titanium dioxide or iron oxides, thus shedding some light on the future development of high-performance metal-oxide based negative electrodes for LIBs.

Lattice dynamics in mono- and few-layer sheets of WS2 and WSe2

Abstract: Thickness is one of the fundamental parameters that define the electronic, optical, and thermal properties of two-dimensional (2D) crystals. Phonons in molybdenum disulfide (MoS2) were recently found to exhibit unique thickness dependence due to the interplay between short and long range interactions. Here we report Raman spectra of atomically thin sheets of WS2 and WSe2, isoelectronic compounds of MoS2, in the mono- to few-layer thickness regime. We show that, similar to the case of MoS2, the characteristic A1g and E2g1 modes exhibit stiffening and softening with increasing number of layers, respectively, with a small shift of less than 3 cm−1 due to large mass of the atoms. Thickness dependence is also observed in a series of multiphonon bands arising from overtone, combination, and zone edge phonons, whose intensity exhibit significant enhancement in excitonic resonance conditions. Some of these multiphonon peaks are found to be absent only in monolayers. These features provide a unique fingerprint and rapid identification for monolayer flakes.