A review on microalgae and cyanobacteria in biofuel production

Today, fossil fuel shortages and climate change impacts have led mankind to the search for an alternative energy. With many advantages, bioenergy is a promising source to replace conventional energy. However, biofuel productions in the first and second generation are likely to add more concerns to the problems in water scarcity and threats to food security. Meanwhile, third generation biofuels obtained from microalgae and cyanobacteria are able to overcome existing challenges thanks to their rapid growth rates, abilities to fix CO 2 , high yields in lipid extraction and capabilities to be grown in non-arable lands. Microalgae and cyanobacteria appear to be the only ones among renewable sources that are capable of producing a wide range of biofuels including biohydrogen, biomethane, bioethanol and biodiesel.In this study, we present an overview about microalgae and cyanobacteria use for the production of biofuels in fundamentals, including their biology, cultivation systems taking into account the hydrodynamic conditions, harvesting, and processing. The review also provides a general picture at the current status of this renewable energy industry

Exact polynomial optimization strengthened with Fritz John conditions

Let $f,g_1,\dots,g_m$ be polynomials with real coefficients in a vector of variables $x=(x_1,\dots,x_n)$. Denote by $\text{diag}(g)$ the diagonal matrix with coefficients $g=(g_1,\dots,g_m)$ and denote by $\nabla g$ the Jacobian of $g$. Let $C$ be the set of critical points defined by \begin{equation} C=\{x\in\mathbb R^n\,:\,\text{rank}(\varphi(x))< m\}\quad\text{with}\quad\varphi:=\begin{bmatrix} \nabla g\\ \text{diag}(g) \end{bmatrix}\,. \end{equation} Assume that the image of $C$ under $f$, denoted by $f(C)$, is empty or finite. (Our assumption holds generically since $C$ is empty in a Zariski open set in the space of the coefficients of $g_1,\dots,g_m$ with given degrees.) We provide a sequence of values, returned by semidefinite programs, finitely converges to the minimal value attained by $f$ over the basic semi-algebraic set $S$ defined by \begin{equation} S:=\{x\in\mathbb R^n\,:\,g_j(x)\ge 0\,,\,j=1,\dots,m\}\,. \end{equation} Consequently, we can compute exactly the minimal value of any polynomial with real coefficients in $x$ over one of the following sets: the unit ball, the unit hypercube and the unit simplex. Under a slightly more general assumption, we extend this result to the minimization of any polynomial over a basic convex semi-algebraic set that has non-empty interior and is defined by the inequalities of concave polynomials.Comment: 32 pages and 2 tables, merged with arXiv:2205.0845

A Nichtnegativstellensatz on singular varieties under the denseness of regular loci

Let $V$ be a real algebraic variety with singularities and $f$ be a real polynomial non-negative on $V$. Assume that the regular locus of $V$ is dense in $V$ by the usual topology. Using Hironaka's resolution of singularities and Demmel--Nie--Powers' Nichtnegativstellensatz, we obtain a sum of squares-based representation that characterizes the non-negativity of $f$ on $V$. This representation allows us to build up exact semidefinite relaxations for polynomial optimization problems whose optimal solutions are possibly singularities of the constraint sets.Comment: 20 pages, 1 table, fixed typo

Practical polynomial optimization through positivity certificates with and without denominators

Les certificats de positivité ou Positivstellens"atze fournissent des représentations de polynômes positifs sur des ensembles semialgébriques de basiques, c'est-à-dire des ensembles définis par un nombre fini d'inégalités polynomiales. Le célèbre Positivstellensatz de Putinar stipule que tout polynôme positif sur un ensemble semialgébrique basique fermé $S$ peut être écrit comme une combinaison pondérée linéaire des polynômes décrivant $S$, sous une certaine condition sur $S$ légèrement plus forte que la compacité. Lorsqu'il est écrit comme ceci, il devient évident que le polynôme est positif sur $S$, et donc cette description alternative fournit un certificat de positivité sur $S$. De plus, comme les poids polynomiaux impliqués dans le Positivstellensatz de Putinar sont des sommes de carrés (SOS), de tels certificats de positivité permettent de concevoir des relaxations convexes basées sur la programmation semidéfinie pour résoudre des problèmes d'optimisation polynomiale (POP) qui surviennent dans diverses applications réelles, par exemple dans la gestion des réseaux d'énergie et l'apprentissage automatique pour n'en citer que quelques unes. Développée à l'origine par Lasserre, la hiérarchie des relaxations semidéfinies basée sur le Positivstellensatz de Putinar est appelée la emph{hiérarchie Moment-SOS}. Dans cette thèse, nous proposons des méthodes d'optimisation polynomiale basées sur des certificats de positivité impliquant des poids SOS spécifiques, sans ou avec dénominateurs.Positivity certificates or Positivstellens"atze provide representations of polynomials positive on basic semialgebraic sets, i.e., sets defined by finitely many polynomial inequalities. The famous Putinar's Positivstellensatz states that every positive polynomial on a basic closed semialgebraic set $S$ can be written as a linear weighted combination of the polynomials describing $S$, under a certain condition on $S$ slightly stronger than compactness. When written in this it becomes obvious that the polynomial is positive on $S$, and therefore this alternative description provides a certificate of positivity on $S$. Moreover, as the polynomial weights involved in Putinar's Positivstellensatz are sums of squares (SOS), such Positivity certificates enable to design convex relaxations based on semidefinite programming to solve polynomial optimization problems (POPs) that arise in various real-life applications, e.g., in management of energy networks and machine learning to cite a few. Originally developed by Lasserre, the hierarchy of semidefinite relaxations based on Putinar's Positivstellensatz is called the emph{Moment-SOS hierarchy}. In this thesis, we provide polynomial optimization methods based on positivity certificates involving specific SOS weights, without or with denominators

RELATIONSHIP BETWEEN GEOCHEMICAL CHARACTERISTICS OF THE LATE PLEISTOCENE-HOLOCENE SEDIMENTS AND GROUND WATER QUALITY IN THE SOUTHERN AREA OF HANOI

Joint Research on Environmental Science and Technology for the Eart

Simulation of Storm Surges in the South Central Coast of Vietnam Under Climate Change

The research was supported by National Research Project Program of Vietnam: science and technology in response to climate change, natural resources and environmental management in the 2016-2020 period (program number: BĐKH/16-20), Developing a sustainable socio-economic model adapting to extreme natural disasters under climate change in the South Central region of Viet Nam. A case study of Ninh Thuan province (grant number: BĐKH.04/16-20). Abstract This paper presents the results of storm surge simulation in the South Central region of Vietnam using the Mike 21-FM HD model. Wind pressure fields of typical storms were first identified in period of 1986-2005 using the parametric wind field model. Storm surge risk was then simulated based on the rare 10, 50 and 100-year frequency corresponding to 2030, 2050, and 2100 scenarios. Storm surge model was finally calibrated and validated using the level of water measured in the November 2009 Typhoon Mirinae and October 2013 Typhoon Nari. The results show that storm surges were consistent with water level variation and amplitude; the maximum and minimum storm surges were 2.34m in the Binh Thuan coastal area and 0.78m in the Khanh Hoa coastal area, respectively. The results of this study demonstrated the use of MIKE 21-FM HD model for the simulation of storm surges in the future plays an important role in damage risk reduction caused by storm surges. Keywords: storm surge simulation, climate change, Mike 21-FM HD model, South Central coast of Vietnam. DOI: 10.7176/JEES/9-6-08 Publication date:June 30th 201

Level of Determinants Impact on Buyer’s Purchasing Intention in Motor Liability Insurance: Case of Vietnam

Motor liability insurance has been included in the compulsory insurance category that each vehicle owner of every type of motor vehicle must participate in in Vietnam. However, in fact, the participation in this type of insurance is not popular and not strictly managed. This paper presents an approach to modeling and analyzing the possible determinants that may affect the intention to buy motor liability insurance for motor vehicle owners in the North of Vietnam. The target audience of this study is motorcycle owners. Based on the theories of buying intention, buying behavior and the specific characteristics of this insurance, this study has proposed a model with 4 factors influencing intention to participate in the insurance: Attitudes towards risk and insurance, subjective standards, Insurance Perceptions, and Product Accessibility. Taken together, these factors model a consumer's tendency toward insurance intentions for motorbike owners. The results show that all of the above factors have influence on the intention of motorcycle owners to participate in insurance. Keywords: Motor liability insurance, Buying intention, Purchase decision DOI: 10.7176/EJBM/13-8-11 Publication date: April 30th 202