Papers by Việt Hào Nguyễn
Vietnam Journal of Science, Technology and Engineering, Jun 15, 2023
Plant-based beverages have become very popular in recent emerging markets. Brown rice milk offers... more Plant-based beverages have become very popular in recent emerging markets. Brown rice milk offers several important health benefits because of its various nutritional ingredients such as proteins, carbohydrates, gammaaminobutyric acid (GABA), and essential vitamins and minerals. Brown rice milk is also low in fats and cholesterol and free of lactose. In this study, japonica brown rice J02 from Thanh Hoa Province presented high nutrition with high protein (8.6% dm) and lipid (2.2% dm) contents as calculated from dry matter and GABA contents of 32 mg/100 g, which is suitable for the plant-based milk processing. J02 rice is also capable of hydrolysis to obtain high molecular sugar in the liquor with slow digestion ability (dextrose equivalent-DE<40) and high hydrolysis efficiency (up to more than 90%). The results obtained from HPLC analysis indicated that the hydrolysis conditions for the rice drink at 75 o C and 150 g/l starch produced Spezyme alpha concentrations at 0.024%w/w and low content in low molecular oligosaccharide (DP<10) in the solution. The results indicated that Japonica rice J02 is a good candidate for the production of a rice-based drink.
Extend Theory of Planned Behaviour Model to Explain Rooftop Solar Energy Adoption in Emerging Market. Moderating Mechanism of Personal Innovativeness
Journal of open innovation, Jun 1, 2023
Journal of Sol-Gel Science and Technology, Aug 14, 2023
In this work, we prepared visible-light active, rhodium and antimony co-doped rutile TiO 2 nanoro... more In this work, we prepared visible-light active, rhodium and antimony co-doped rutile TiO 2 nanorod (Rh-Sb:TiO 2 NR) for the degradation of organic pollutants and inactivation of microbial pathogens. Rh-Sb:TiO NR sample showed a shift in the absorption band in the visible light region (650 nm). Initially, photocatalytic activity of the Rh-Sb:TiO 2 NR was hindered due to its poor surface properties. To improve the surface quality of the less active Rh-Sb:TiO 2 NR photocatalyst, the effect of the acid treatment and Cu x O impregnation on the Rh-Sb:TiO 2 NR were evaluated (Cu x O/A-Rh-Sb:TiO 2 NR). The photocatalytic activity of Cu x O/A-Rh-Sb:TiO 2 NR photocatalyst was remarkably higher than that of the as-prepared sample. The improved photocatalytic activity of less active Rh-Sb:TiO 2 NR is due to the synergistic effect of acid treatment and finely dispersed Cu x O nanoparticles which improve the charge transfer near the interface of A-Rh-Sb:TiO 2 NR photocatalyst toward Cu x O nanoparticles. Deconvolution of Cu result indicated that Cu x O have mixed phase of 2+ and 1+ oxidation state which facile the charge transfer at the conduction band of photocatalyst. The optimization of Cu x O loading was achieved by measuring the photocatalytic degradation efficiencies at controlled Cu concentrations on the A-Rh-Sb:TiO 2 NRs. Furthermore, the optimized Cu x O sample was used for photocatalytic degradation of bisphenol A (BPA) and inactivation of L. monocytogenes pathogen. This work provides an efficient visible light photocatalyst for a broad range of environmental applications, such as pathogenic bacterial inactivation and decomposition of organic pollutants.
Multi-level Antecedents of Social Capital and its Performance Consequences
Proceedings - Academy of Management, 2014
This study applies the social capital, expectancy and the hierarchical linear modeling (HLM) appr... more This study applies the social capital, expectancy and the hierarchical linear modeling (HLM) approach to examine the multilevel antecedents and performance consequences of employees’ internal and e...
Journal of Economic Behavior & Organization, 2018
Consumptor economicus, the economic consumer, is more complex than homo economicus. We find consu... more Consumptor economicus, the economic consumer, is more complex than homo economicus. We find consumers form monthly expectations on inflation, unemployment and economic conditions based on coherent evaluations of relevant news. Relevant information is incorporated gradually, leading to a transient bias in consumer expectations, an established result. But expectations are also based on emotional responses to irrelevant events. We borrow the partisan bias from the political science and social psychology literature to identify exogenously emotional responses. Our results demonstrate that consumers also incorporate irrelevant emotive events immediately, leading to a persistent emotional bias in expectations, a new result.
Applied Ecology and Environmental Research, 2020
Surface soil samples were collected from different land use types of the agricultural land in Nam... more Surface soil samples were collected from different land use types of the agricultural land in Nam Dinh province, Vietnam to determine the level of heavy metal contamination and identifying potential sources. The farming areas of rice and cereal show similar heavy metal contents, however, the index shows that the content of heavy metals in the aquacultural area is lower compared to the other types. The mean enrichment factor (EF) values of Cr, Cu, Pb, and Zn are less than 1.5, suggesting that these are not a major concern in the research area; whereas, the mean EF values for Cd is higher than 2 and As varies from 5-20 suggest that the pollution of these heavy metals is present in agricultural soil. The data analysis indicates that Cr mainly originates from a natural source; Cd and As have a significant anthropogenic input; Cd, Pb and Zn have a mixed source.
Nanomaterials, 2020
Nanostructures of titanium nitride (TiN) have recently been considered as a new class of plasmoni... more Nanostructures of titanium nitride (TiN) have recently been considered as a new class of plasmonic materials that have been utilized in many solar energy applications. This work presents the synthesis of a novel nanostructure of TiN that has a nanodonut shape from natural ilmenite ore using a low-cost and bulk method. The TiN nanodonuts exhibit strong and spectrally broad localized surface plasmon resonance absorption in the visible region centered at 560 nm, which is well suited for thermoplasmonic applications as a nanoscale heat source. The heat generation is investigated by water evaporation experiments under simulated solar light, demonstrating excellent solar light harvesting performance of the nanodonut structure.
The Baltic Journal of Road and Bridge Engineering, 2018
Principal Component Analysis is used for damage detection in structures excited by harmonic force... more Principal Component Analysis is used for damage detection in structures excited by harmonic forces. Time responses are directly analysed by Singular Value Decomposition to deduct two dominant Proper Orthogonal Values corresponding to two Proper Orthogonal Modes. Damage index is defined by the concept of subspace angle that a subspace is built from the two Proper Orthogonal Modes. A subspace angle reflects the coherence between two different structural health states. An example is given through the application on a part of a real prestressed concrete bridge in Luxembourg where different damage states were created by cutting a number of prestressed tendons in four scenarios with increasing levels. Results are better by using excitation frequency close to an eigenfrequency of the structure. The technique is convenient for practical application in operational bridge structures.
RAIRO - Operations Research, 2019
Let G = (V, E) be an undirected graph where the edges in E have non-negative weights. A star in G... more Let G = (V, E) be an undirected graph where the edges in E have non-negative weights. A star in G is either a single node of G or a subgraph of G where all the edges share one common end-node. A star forest is a collection of vertex-disjoint stars in G. The weight of a star forest is the sum of the weights of its edges. This paper deals with the problem of finding a Maximum Weight Spanning Star Forest (MWSFP) in G. This problem is NP-hard but can be solved in polynomial time when G is a cactus [Nguyen, Discrete Math. Algorithms App. 7 (2015) 1550018]. In this paper, we present a polyhedral investigation of the MWSFP. More precisely, we study the facial structure of the star forest polytope, denoted by SFP(G), which is the convex hull of the incidence vectors of the star forests of G. First, we prove several basic properties of SFP(G) and propose an integer programming formulation for MWSFP. Then, we give a class of facet-defining inequalities, called M-tree inequalities, for SFP(G)....
Optimization Methods and Software, 2016
We investigate a variant of the Graph Partitioning Problem with capacity constraints imposed on t... more We investigate a variant of the Graph Partitioning Problem with capacity constraints imposed on the clusters, giving rise to quadratic constraints in 0-1 formulations. Several compact linearized models of the problem are proposed and analyzed: a) a model featuring O(n 3) binary variables which results from the application of the standard Fortet linearization technique; b) a more compact model featuring only O(n 2) binary variables, obtained by linearization after reformulation of the quadratic constraints as bilinear constraints; c) a strengthened version of the latter model, still featuring O(n 2) variables. Computational experiments comparing the relative strength and efficiency of the various models on a series of test instances involving complete graphs with up to 50 nodes are reported and discussed.
Civil Engineering Design, 2019
Structural Health Monitoring with analysis of dynamic characteristics intends to detect stiffness... more Structural Health Monitoring with analysis of dynamic characteristics intends to detect stiffness changes caused by damage. It can be performed by vibrational tests resulting to modal parameters, that is, eigenfrequencies, damping, modeshapes, or modal masses. Those parameters are themselves informational and even allow often deducing the stiffness matrix. Based on that, it is possible to identify and to localize changes in the stiffness matrix due to damage, that is, localization and quantification of damage. However, changing test conditions, like ambient temperature or excitation force or existing nonlinearities of concrete, show important influence on damage indicators and hence need compensation prior to damage detection. Considering this background, this article focuses on comparing ambient excitation to forced excitation including appropriate exciters. Furthermore, continuous monitoring is discussed vs discrete testing in distinct time‐intervals. The intention of the comparis...
Australian Economic Review, 2019
Economic activity in Australia continued to improve in 2017-2018 with growth spreading across the... more Economic activity in Australia continued to improve in 2017-2018 with growth spreading across the mainland state economies. Labour market conditions in Australia improved markedly in 2017-2018 while the inflation rate was steady around the lower end of the Reserve Bank of Australia's 2-3 per cent target band. Real wage growth was weak and is likely to remain weak in 2018-2019, putting downward pressure on household consumption. Output growth in 2018-2019 is likely to be solid with prospects of the Chinese economy and trade tensions between China and the United States posing the greatest downside risk to the Australian economy. ... [A]bstracting from the cyclical dynamics, there is a longer-run trend towards more similarity, rather than more divergence, in the underlying economic structure across the country.
Engineering, 2017
This paper discusses the influence of environmental factors and of normal material aging on the e... more This paper discusses the influence of environmental factors and of normal material aging on the eigenfrequencies of concrete bridges based on monitoring data registered during 4 years of a specific bridge. It is a new composite steel-concrete bridge built in 2006 in Luxembourg. The measurements are analyzed and compared to literature data. The final objective is the use of real monitored eigenfrequencies for structural health monitoring and damage detection based on identification of stiffness losses in practical applications. Therefore, it is very important to identify and compensate for outdoor influences namely temperature, excitation force level and normal aging effects, like creep and shrinkage of concrete and their impact on material properties. The present paper aims at describing these effects in order to separate them from damage effects. It is shown that temperature change rates and temperature gradients within the bridge have an influence on the eigenfrequencies. Hence the key idea for assessment from the full database is to select only measurements with small temperature differences and slow temperature change rates.
Networks, 2016
Given a graph with and , we consider the metric cone and the metric polytope defined on . These p... more Given a graph with and , we consider the metric cone and the metric polytope defined on . These polyhedra are relaxations of several important problems in combinatorial optimization such as the max‐cut problem and the multicommodity flow problem. They are known to have non‐compact formulations via the cycle inequalities in the original space and compact (i.e., polynomial size) extended formulations via the triangle inequalities defined on the complete graph . In this article, we show that one can reduce the number of triangle inequalities to and still have extended formulations for and . This is particularly interesting for sparse graphs when , since formulations of size variables and constraints are thus obtained. Moreover, the possibility of achieving further reduction in size for special classes of sparse graphs is investigated; it is shown that for the case of series‐parallel graphs, for which the max‐cut problem can be solved in linear time (Barahona, Discr Appl Math 13 (1986),...
SSRN Electronic Journal, 2016
The objective of this work is to address the problem of damage detection in civil engineering str... more The objective of this work is to address the problem of damage detection in civil engineering structures using non-destructive techniques and dynamic measurements. To this purpose, time-or frequency-domain methods are used for the diagnostics. It consists in practical output-only techniques as Stochastic Subspace Identification (SSI) for modal identification or Enhanced Principal Component Analysis (EPCA) for detecting the presence of damage. The use of the Hankel matrix instead of the observation matrix improves effectively the robustness of these methods. Damage localization is based on Frequency Response Functions (FRFs) and sensitivity analysis of PCA results. The efficiency of the above-mentioned methods has been demonstrated in earlier studies mainly on numerical models and small-scale laboratory experiments [3, 4]. It was also tested successfully on industrial examples to perform machine condition monitoring using a reduced set of sensors [2]. In this work, the investigation is performed on precast prestressed and nonprestressed concrete slabs. Successive damages were artificially introduced in the slabs by loading heavy weights and by cutting steel wires, which induced cracks in the structure. The examples show the consequences of the considered techniques for damage identification. The results that are very different between prestressed and non-prestressed slabs may be used as input for the condition control of this kind of structures.
Optimization Letters, 2015
We consider a variant of the graph partitioning problem involving knapsack constraints with Gauss... more We consider a variant of the graph partitioning problem involving knapsack constraints with Gaussian random coefficients. In this new variant, under this assumption of probability distribution, the problem can be traditionally formulated as a binary SOCP for which the continuous relaxation is convex. In this paper, we reformulate the problem as a binary quadratic constrained program for which the continuous relaxation is not necessarily convex. We propose several linearization techniques for latter: the classical linearization proposed by Fortet (Trabajos de Estadistica, 1960, Vol. 11) and the linearization proposed by Sherali and Smith (Optimization Letters, 2007, Vol. 1). In addition to the basic implementation of the latter, we propose an improvement which includes, in the computation, constraints coming from the SOCP formulation. Numerical results show that an improvement of Sherali-Smith's linearization outperforms largely the binary SOCP program and the classical linearization when investigated in a branch-and-bound approach.
Shock and Vibration, 2014
The aim of this paper is to apply both time- and frequency-domain-based approaches on real-life c... more The aim of this paper is to apply both time- and frequency-domain-based approaches on real-life civil engineering structures and to assess their capability for damage detection. The methodology is based on Principal Component Analysis of the Hankel matrix built from output-only measurements and of Frequency Response Functions. Damage detection is performed using the concept of subspace angles between a current (possibly damaged state) and a reference (undamaged) state. The first structure is the Champangshiehl Bridge located in Luxembourg. Several damage levels were intentionally created by cutting a growing number of prestressed tendons and vibration data were acquired by the University of Luxembourg for each damaged state. The second example consists in reinforced and prestressed concrete panels. Successive damages were introduced in the panels by loading heavy weights and by cutting steel wires. The illustrations show different consequences in damage identification by the conside...
Damage identification for two real big bridges in Luxembourg is carried out in this paper. Vibrat... more Damage identification for two real big bridges in Luxembourg is carried out in this paper. Vibration responses were captured from different types of excitation such as measurable and adjustable harmonic swept sine excitation and hammer impact. Before, different analysis methods were applied to the data measured from these structures showing interesting results. However, some difficulties are faced, especially due to environmental influences (temperature and soil-behaviour variations) overlaid to the structural changes caused by damage. These environmental effects are investigated in detail in this work. First, the modal parameters are identified from the response data by means of Wavelet Transform. In the next step, they are stochastically collected and processed through Principal Component Analysis. Damage index is based on outlier analysis.
SSRN Electronic Journal, 2015
The introduction of the panel and global VAR frameworks and the increasing sophistication of larg... more The introduction of the panel and global VAR frameworks and the increasing sophistication of large simulated systems provides opportunities to analyse international linkages in unprecedented depth. However, the considerable volume of statistical output generated by such models introduces a secondary curse of dimensionality, whereby the limits of the modeller's ability to process the output become a binding constraint. This paper develops a family of Generalized Connectedness Measures (GCMs) which provide a simple means to summarise the linkages embodied in such models non-selectively either with recourse to geographic aggregation or aggregation into desired groups of similar variables. These GCMs are derived from generalized forecast error variance decompositions in a manner that extends the connectedness measures developed by Diebold and Yilmaz (2009, 2011). Our GCMs preserve information across horizons and are robust both to the reordering of variables and to aggregation. We apply our approach using the 26 country 176 variable GVAR model developed by Greenwood-Nimmo, Nguyen and Shin (2012, Journal of Applied Econometrics) and derive vivid representations of the linkages embodied in the model. Our results indicate that the US, the Eurozone and the crude oil market are hot-spots for the transmission of shocks in the global economy and that shocks transmitted through equity markets can strongly affect real magnitudes.
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Papers by Việt Hào Nguyễn