Management of Urban Greenery System in Vietnam in the Era of Industry 4.0

Application of computer software and exploitation database systems bring great benefits and integrate many features in different fields of science and life for urban management including urban greenery management in cities. In Vietnam, they have been being more concerned due to the Vietnamese Government policies in development of e-Government and smart cities. This paper firstly focuses on discussion about the reality of urban greenery management in Vietnam to reveal the problems in management as well as opportunities of this field in application new technology in cities, such as artificial intelligent, information technology, internet of things, ... Secondly, it reviews the current application of science and technology in urban greenery management in the world as well as cities in Vietnam to evaluate the effectiveness, understand a broader context and eventually draw lessons, which can be learned for this field in Vietnamese circumstance. Finally, it discusses the potential to apply the management software and suggests some suitable solutions for the smart urban greenery management, that can provide effective tools and become components to develop and organize smart cities in Vietnam in the era of Industry 4.0

The time to shut down

At each time, a firm facing uncertainty over future market conditions have to make a decision whether they should continue to produce or stop the process? As the traditional principle, the firm will go out of production when the price of the typical unit does not cover the average variable cost that it must incur to produce the typical unit. In reality the firm can suffer losses today however it can get more gains tomorrow that is enough to make up the losses. It means that this rule seems not be suitable absolutely in an uncertainty environment. And it leads to a rule that the firm only stop producing if average variable costs of unit exceed the price of unit by a positive amount. This paper expects to find this exceeding amount and when a firm will stop producing. Under uncertainty, the price of unit and the average variables cost are assumed to follow a continuous time stochastic process. We wish to apply the optimal stopping time approach in order to solve it.

The influence of thermal effects on structural health monitoring of Attridge Drive overpass

Structural Health Monitoring (SHM) comprises a wide range of techniques for the condition and damage assessment of an existing structure. Vibration-based damage detection (VBDD) techniques, a class of SHM methods, use changes in the dynamic properties (i.e., natural frequencies, mode shapes and damping characteristics) of structures to detect deterioration or damage. The application of VBDD methods to simple structures in a well-controlled laboratory environment has gained some successful results. However, the practical field application of VBDD still faces significant challenges since vibration measurement is subject to the influences of high levels of uncertainty in environmental, structural and loading conditions. In this thesis, the influence of temperature variations on the application of VBDD methods to an in-service complex structure was experimentally and numerically studied. The structure studied was the Attridge Drive overpass in Saskatoon, Saskatchewan. The main objective of this research was to assess the influence of temperature variation on the dynamic properties (natural frequencies and mode shapes) of the overpass, and on the ability of VBDD methods to detect and locate damage. Field dynamic measurements were made on the bridge on numerous occasions under a wide variety of ambient temperatures, using high sensitivity accelerometers and a temperature sensor. Dynamic excitation was provided solely by ambient traffic loading. Finite element models of the overpass were also created and manually calibrated to measured field data. The models were used to simulate the dynamic behaviour of the bridge at a variety of temperatures and under various states of small-scale damage. Numerical analysis was conducted to study the effect of ambient temperature on structure’s dynamic characteristics and to differentiate the patterns of mode shape changes caused by damage and ambient temperature. It was concluded that the change of ambient temperature mainly affects the elastic modulus of the construction materials and therefore stiffness of the entire bridge. As a result, the eigenfrequencies and mode shapes of the structure are influenced. The dynamic properties extracted from measured experiment data showed an approximately bilinear relationship between the three first natural frequencies and the ambient temperature. The natural frequencies for all three modes increased when the temperature fell. It was also found that, conceptually, it is possible to distinguish the patterns of mode shape changes caused by small-scale damage from those due to thermal effects, but only if a sufficient number of sensors are used to measure the mode shapes; in addition, those sensors must be located close to the damage location

Influences of heating temperatures on physical properties, spray characteristics of bio-oils and fuel supply system of a conventional diesel engine

Alternative fuels need to satisfy the strict requirements of the use for diesel engines aiming at enhancing the performance and reducing pollutant emissions. The use of straight bio-oils for diesel engines entails improving their disadvantages such as high density, high surface tension and kinematic viscosity (tri-physical parameters). There have been some as-used methods for reduction of the above-mentioned negative effects related to straight bio-oil disadvantage, however, the adequately-heating method may be considered as a simple one helping the physical parameters of straight bio-oils to reach stable and highly-confident values which are close to those of traditional diesel fuel. As a consequence, the spray and atomization, combustion, performance, and emissions of diesel engines fueled with preheated bio-oils are improved. In this work, a study of the dependence of the density, surface tension and kinematic viscosity of coconut oil (a type of bio-oils) on temperatures (from 40-110oC) within a wide variety are conducted. In the first stage, the influence study of temperature on tri-physical parameters is carried out on the basis of experimental correlation and as-described mathematical equation. In the second stage, the influence study of tri-physical parameters on spray and atomization parameters including penetration length (Lb) and Sauter mean diameter (SMD), and the influence of tri-physical parameters on fuel supply system are investigated. The optimal range of temperature for the as-used bio-oils is found after analyzing and evaluating the obtained results regarding the physical properties and spray characteristics, as well as compared with those of diesel fuel. The confident level over 95% from the regression correlation equation between the above-mentioned tri-physical parameters and temperature is presented. Additionally, the measured spray parameters, the calculated values of frictional head loss and fuel flow rate are thoroughly reported. 

Is Nonfarm Diversification a Way Out of Poverty for Rural Households? Evidence from Vietnam in 1993-2006

school. Using the four high quality household living standards surveys available to date this paper reveals that Vietnam’s rural labour force has been markedly diversifying toward nonfarm activities in the doi moi (renovation) reform period. The employment share of the rural nonfarm sector has increased from 23 percent to 58 percent between the years 1993 and 2006. At the individual level, the results indicate that participation in the rural nonfarm sector is determined by a set of individual-, household-, and community-level characteristics. Gender, ethnicity, and education are reported as main individual-level drivers of nonfarm diversification. Lands as most important physical assets of rural households are found to be negative to nonfarm employment. It is also evident that both physical and institutional infrastructure exert important influences on individual participation in the nonfarm sector. At the household level, a combination of parametric and semi-parametric analysis is adopted to examine whether nonfarm diversification is a poverty exit path for rural households. This paper demonstrates a positive effect of nonfarm diversification on household welfare and this effect is robust to different estimation techniques, measures of nonfarm diversification, and the usage of equivalent scales. However, the poor is reported to benefit less than the non-poor from nonfarm activities. Though promoting a buoyant nonfarm sector is crucial for rural development and poverty reduction, it needs to be associated with enhancing access to nonfarm opportunities for the poor.Rural nonfarm sector, nonfarm diversification, household welfare, Vietnam

Observations millimétriques/submillimétriques de galaxies lentillées gravitationellement à haut redshift

Nous présentons une étude détaillée d'observations faites de la galaxie hôte d'un quasar lointain (z~2.8), RX J0911. La détection de l'émission des molécules CO a été possible grâce au lentillage gravitationnel dû à la présence d'une galaxie plus proche sur la ligne de vue et à la qualité de l'interféromètre du Plateau de Bure. On a obtenu de très bonnes résolutions tant en fréquence, permettant une mesure précise de la largeur de raie, qu'en direction, permettant de résoudre la source aussi bien sur la raie que dans le continu, donc à la fois pour le gaz et pour la poussière. Nous avons discuté en détail le mécanisme de lentillage gravitationnel. Comme souvent lorsqu'il s'agit de grandissements importants, la source est proche de la caustique de la lentille, dans le cas précis elle la chevauche. Il en résulte une dépendance importante du grandissement sur la position précise des sources ponctuelles à l'intérieur de la galaxie, donc des grandissements différents pour le gaz, la poussière et le quasar. D'autre part, les images sont non seulement aggrandies mais aussi déformées. Les données illustrent les avantages offerts par le lentillage en termes de sensibilité en même temps que les complications de l'analyse qui en découlent, source d'incertitudes sur les mesures. La raie CO(7-6) sort clairement du continu, permettant des mesures fiables des luminositées associées au gaz et à la poussière. Des études détaillées des quatre images ont permis de résoudre la source tant sur la raie que dans le continu, avec des rayons de 106±15 et 39±18 mas respectivement. Dans le cas de la raie, la qualité des données a permis de mettre en évidence une excentricité à 3.3 déviations standard et un gradient de vitesse à 4.5 déviations standards. La largeur très étroite de la raie implique une masse dynamique basse et les évaluations faites des masses de gaz et de poussière sont elles aussi très au dessous de ce qu'on mesure généralement pour des quasars à fort décalage vers le rouge. La valeur élevée de l'efficacité de formation d'étoiles situe la galaxie dans la partie haute de la distribution des galaxies, qu'elles soient à haut ou bas z: une fraction importante du volume gazeux semble avoir été épuisée à la suite d'une période de formation d'étoiles intense, laissant la galaxie à la frontière des galaxies hôtes de quasar à haut et bas z.The thesis gives a detailed account of observations of the host galaxy of a distant quasar, RX J0911. Detailed observations of the CO emission have been made possible thanks to the gravitational lensing offered by the presence of a galaxy in the foreground and to the quality of the Plateau de Bure Interferometer. High resolutions have been obtained both in frequency, allowing for a precise measurement of the line width, and in space, allowing for resolving spatially the source both on the line and in the continuum, namely both in its dust and gas content. The mechanism of gravitational lensing has been discussed in detail. As is often the case with large magnifications, the source happens to be in the vicinity of the lens caustic, in fact to overlap it. A consequence is a strong dependence of the magnification on the precise position of point sources in the galaxy, resulting in significantly different magnifications for the gas, the dust and the central QSO. Moreover, the morphology of the observed images is distorted in addition to being amplified. The data illustrate the advantage offered by the strong lensing in terms of increased sensitivity as well as the complication that results, causing an additional source of uncertainties on the quantities that are accessible to measurement. The CO(7-6) line stands out clearly above continuum, allowing for reliable measurements of the gas and dust luminosities. Detailed studies of the four lensed images have made it possible to resolve the source in both the line and the continuum with rms radii of 106±15 and 39±18 mas respectively. In the line case, the quality of the data have provided evidence for an ellipticity of the source, 3.3 standard deviations away from circular, and for a velocity gradient correlated with the source ellipticity, at the level of 4.5 standard deviations. The very narrow CO(7-6) line implies a low dynamical mass and both gas and dust mass evaluations fall on the low side of the normal high-z quasar host population. The large star formation efficiency is on the high side of both low-z and high-z galaxies: much of the gas has been exhausted after an intense star formation period, leaving the galaxy at the border between high-z and low-z quasar hosts