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.

Random access for machine-to-machine communication in LTE-advanced networks: issues and approaches

Abstract: Machine-to-machine communication, a promising technology for the smart city concept, enables ubiquitous connectivity between one or more autonomous devices without or with minimal human interaction. M2M communication is the key technology to support data transfer among sensors and actuators to facilitate various smart city applications (e.g., smart metering, surveillance and security, infrastructure management, city automation, and eHealth). To support massive numbers of machine type communication (MTC) devices, one of the challenging issues is to provide an efficient way for multiple access in the network and to minimize network overload. In this article, we review the M2M communication techniques in Long Term Evolution- Advanced cellular networks and outline the major research issues. Also, we review the different random access overload control mechanisms to avoid congestion caused by random channel access of MTC devices. To this end, we propose a reinforcement learning-based eNB selection algorithm that allows the MTC devices to choose the eNBs (or base stations) to transmit packets in a self-organizing fashion.

Insights into the Interplay of Lewis and Brønsted Acid Catalysts in Glucose and Fructose Conversion to 5‑(Hydroxymethyl)furfural and Levulinic Acid in Aqueous Media

Abstract: 5-(Hydroxymethyl)furfural (HMF) and levulinic acid production from glucose in a cascade of reactions using a Lewis acid (CrCl3) catalyst together with a Bronsted acid (HCl) catalyst in aqueous media is investigated. It is shown that CrCl3 is an active Lewis acid catalyst in glucose isomerization to fructose, and the combined Lewis and Bronsted acid catalysts perform the isomerization and dehydration/rehydration reactions. A CrCl3 speciation model in conjunction with kinetics results indicates that the hydrolyzed Cr(III) complex [Cr(H2O)5OH](2+) is the most active Cr species in glucose isomerization and probably acts as a Lewis acid-Bronsted base bifunctional site. Extended X-ray absorption fine structure spectroscopy and Car-Parrinello molecular dynamics simulations indicate a strong interaction between the Cr cation and the glucose molecule whereby some water molecules are displaced from the first coordination sphere of Cr by the glucose to enable ring-opening and isomerization of glucose. Additionally, complex interactions between the two catalysts are revealed: Bronsted acidity retards aldose-to-ketose isomerization by decreasing the equilibrium concentration of [Cr(H2O)5OH](2+). In contrast, Lewis acidity increases the overall rate of consumption of fructose and HMF compared to Bronsted acid catalysis by promoting side reactions. Even in the absence of HCl, hydrolysis of Cr(III) decreases the solution pH, and this intrinsic Bronsted acidity drives the dehydration and rehydration reactions. Yields of 46% levulinic acid in a single phase and 59% HMF in a biphasic system have been achieved at moderate temperatures by combining CrCl3 and HCl.

Doping single-layer graphene with aromatic molecules.

Abstract: Recently discovered single-layer graphene (SLG) has attracted great attention not only because this perfect 2-dimensional carbon crystalline structure enables unprecedented explorations of fundamental physics but also because of its exciting potentials in the post-silicon nanoeletronics 1-6 . As the electrical properties of SLG films are very sensitive to the local perturbations such as from surface charges 7-9 and adsorbed gas molecules 6 , it is plausible that the electronic structures, hence the performance, of SLG may be tailored by molecular doping on its surface. Herein, we demonstrated that the electronic structures of SLG can be differentially modulated by doping from various aromatic molecules. We also show that a simple spectroscopic method based on the Raman 2D and G band frequency sampling can be used to distinguish the n- and p-doped SLG. Raman spectroscopy is a powerful tool to rapidly and nondestructively examine intrinsic physical properties of various carbon nanostructures, including flat and one-atom thick carbon crystalline layer (graphene monolayer), stacked graphenes (graphite), and roll-up graphene monolayer (single-walled carbon nanotube–SWNT). The characteristic G (~1580-1590 cm -1 ) and 2D (~2690-2710 cm -1 ) Raman bands are able to reveal the number of stacked graphene layer 10-12 and the changes in charge carrier concentration (or Fermi energy shift) induced by static electrical field 13-14 .

Recent Progress in Energy-Driven Water Splitting

Abstract: Hydrogen is readily obtained from renewable and non-renewable resources via water splitting by using thermal, electrical, photonic and biochemical energy. The major hydrogen production is generated from thermal energy through steam reforming/gasification of fossil fuel. As the commonly used non-renewable resources will be depleted in the long run, there is great demand to utilize renewable energy resources for hydrogen production. Most of the renewable resources may be used to produce electricity for driving water splitting while challenges remain to improve cost-effectiveness. As the most abundant energy resource, the direct conversion of solar energy to hydrogen is considered the most sustainable energy production method without causing pollutions to the environment. In overall, this review briefly summarizes thermolytic, electrolytic, photolytic and biolytic water splitting. It highlights photonic and electrical driven water splitting together with photovoltaic-integrated solar-driven water electrolysis.