Researchers who lead the trends

Xuan-Hung Doan, Phuong-Tram T. Nguyen, Viet-Phuong La, Hong-Kong T. Nguyen (2019). Chapter 5. Researchers who lead the trends. In Quan-Hoang Vuong, Trung Tran (Eds.), The Vietnamese Social Sciences at a Fork in the Road (pp. 98–120). Warsaw, Poland: De Gruyter. DOI:10.2478/9783110686081-010 Online ISBN: 9783110686081 © 2019 Sciend

Form and Function: X-Ray Scattering and Spectroscopy of Transition Metal-Based Nanoparticles

In recent decades, nanoparticles have been found to possess unique, tunable properties with an enormous variety of applications. The atomic and nanoscale structures govern these functional properties, and structural deviations from the bulk, in part, are responsible for the vast technological uses of nanoparticles. This dissertation tackles the understanding of structure in a number of metal, metal phosphide, and metal oxide nanoparticle systems. Additionally, the syntheses of monodispersed nanoparticle systems allow for correlating their structure with functional properties. Real space analysis using pair distribution functions of monometallic (Ni, Pd) nanoparticles of less than 5 nm in diameter revealed a deviation from the bulk face-centered cubic structure. Their local atomic packing disorder and lack of long-range order resemble that of bulk metallic glasses, which often consist of complex mixtures of a multitude of elements. Bulk metallic glasses have high mechanical strength and can sustain elastic deformations. The significant connection between these two seemingly disparate systems lie in the short-range ordering of their atomic packing motifs, which consist of icosahedral symmetry as seen in their pair distribution functions. Cobalt phosphide (Co2P) nanorods are promising as inexpensive, earth abundant catalysts for the oxygen reduction reaction in fuel cells. Additionally, their 1-D structures demonstrated greater stability as compared to conventional Pt catalysts. Their structure was investigated using high-resolution electron microscopy and a suite of X-ray scattering and absorption techniques. The dynamic structural nature of the solid-solid phase transition in vanadium dioxide (VO2) thin films was investigated using X-ray absorption fine structure spectroscopy. Substitution of transition metal dopants into lattice sites revealed the structurally-driven depression of the metal-to-insulator transition temperature. Bridging form and function, this dissertation reports the colloidal synthesis of monodispersed nanoparticles alongside structural investigations and functional testing

APMEC: An Automated Provisioning Framework for Multi-access Edge Computing

Novel use cases and verticals such as connected cars and human-robot cooperation in the areas of 5G and Tactile Internet can significantly benefit from the flexibility and reduced latency provided by Network Function Virtualization (NFV) and Multi-Access Edge Computing (MEC). Existing frameworks managing and orchestrating MEC and NFV are either tightly coupled or completely separated. The former design is inflexible and increases the complexity of one framework. Whereas, the latter leads to inefficient use of computation resources because information are not shared. We introduce APMEC, a dedicated framework for MEC while enabling the collaboration with the management and orchestration (MANO) frameworks for NFV. The new design allows to reuse allocated network services, thus maximizing resource utilization. Measurement results have shown that APMEC can allocate up to 60% more number of network services. Being developed on top of OpenStack, APMEC is an open source project, available for collaboration and facilitating further research activities

An Experiment on a CO2 Air Conditioning System with Copper Heat Exchangers

This paper presented an experiment on a CO2 air conditioning system with copper heat exchangers. In this study, the compressor and cooler were tested with hydraulic method to determine the deformed and torn temperatures. The results show that conventional compressor is not suitable for using high pressure, due to the COP of cycle is very low (0.5 only). With CO2 compressor, the cycle can be achieved COP of 3.07 at the evaporative temperature of 10C. This value equals with COP of commercial air conditioning system presently

The spindle of oocytes observed by polarized light microscope can predict embryo quality

Background: The aim is to evaluate spindle position of metaphase II oocyte and the development of embryos originated from oocytes with spindle and without spindle.Methods: Cross-sectional analysis Research: 250 MII oocytes were analyzed with polarized microscope in Military Institute of Clinical Embryology and Histology, Vietnam Military Medical University.Results: Spindles were detected in 170 (77.98%) of 218 metaphase II oocytes, 115 spindles (67.65%) of MII oocytes is beneath or adjacent to the first polar body, 55 oocytes had the spindle located between 300 and 1800 away from the first polar body. Fertilization rate and the rate of good quality embryos in oocytes with a visible spindle (77.98% and 61.02%) were higher than those in oocytes without a visible spindle (22.02% and 36.84%), the difference was statistically significant with p <0.001 and p <0.05.Conclusions: The spindle position of metaphase II oocytes is not always beneath or adjacent to the first polar body. Fertilization rate and the rate of good quality embryos in oocytes with a visible spindle were higher than those in oocytes without a visible spindle

Distributed two-time-scale methods over clustered networks

In this paper, we consider consensus problems over a network of nodes, where the network is divided into a number of clusters. We are interested in the case where the communication topology within each cluster is dense as compared to the sparse communication across the clusters. Moreover, each cluster has one leader which can communicate with other leaders in different clusters. The goal of the nodes is to agree at some common value under the presence of communication delays across the clusters. Our main contribution is to propose a novel distributed two-time-scale consensus algorithm, which pertains to the separation in network topology of clustered networks. In particular, one scale is to model the dynamic of the agents in each cluster, which is much faster (due to the dense communication) than the scale describing the slowly aggregated evolution between the clusters (due to the sparse communication). We prove the convergence of the proposed method in the presence of uniform, but possibly arbitrarily large, communication delays between the leaders. In addition, we provided an explicit formula for the convergence rate of such algorithm, which characterizes the impact of delays and the network topology. Our results shows that after a transient time characterized by the topology of each cluster, the convergence of the two-time-scale consensus method only depends on the connectivity of the leaders. Finally, we validate our theoretical results by a number of numerical simulations on different clustered networks

One-pot preparation of alumina-modified polysulfone-graphene oxide nanocomposite membrane for separation of emulsion-oil from wastewater

In recent years, polysulfone-based nanocomposite membranes have been widely used for contaminated water treatment because they comprise properties such as high thermal stability and chemical resistance. In this study, a polysulfone (PSf) nanocomposite membrane was fabricated using the wet-phase inversion method with the fusion of graphene oxide (GO) and alumina (Al2O3) nanoparticles. We also showed that GO-Al2O3 nanoparticles were synthesised successfully by using a one-pot hydrothermal method. The nanocomposite membranes were characterised by Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), nitrogen adsorption-desorption isotherms, energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), and water contact angle. The loading of GO and Al2O3 was investigated to improve the hydrophilic and oil rejection of the matrix membrane. It was shown that by using 1.5 wt.% GO-Al2O3 loaded in polysulfone, ~74% volume of oil was separated from the oil/water emulsion at 0.87 bar and 30 min. This figure was higher than that of the process using the unmodified membrane (PSf/GO) at the same conditions, in which only ~60% volume of oil was separated. The pH, oil/water emulsion concentration, separation time, and irreversible fouling coefficient (FRw) were also investigated. The obtained results suggested that the GO-Al2O3 nanoparticles loaded in the polysulfone membrane might have potential use in oily wastewater treatment applications

Designing a novel heterostructure AgInS₂@MIL-101(Cr) photocatalyst from PET plastic waste for tetracycline degradation

Semiconductor-containing porous materials with a well-defined structure could be unique scaffolds for carrying out selective organic transformations driven by visible light. We herein introduce for the first time a heterostructure of silver indium sulfide (AgInS(2)) ternary chalcogenide and a highly porous MIL-101(Cr) metal–organic framework (MOF) synthesised from polyethylene terephthalate plastic waste. Our results demonstrate that AgInS(2) nanoparticles were uniformly attached to each lattice plane of the octahedral MIL-101(Cr) structure, resulting in a nanocomposite with a high distribution of semiconductors in a porous media. We also demonstrate that the nanocomposite with up to 40% of AgInS(2) doping exhibited excellent catalytic activity for tetracycline degradation under visible light irradiation (∼99% tetracycline degraded after 4 h) and predominantly maintained its performance after five cycles. These results could promote a new material circularity pathway to develop new semiconductors that can be used to protect water from further pollution