Evaluation of municipal waste management options by circular prevention tools to give better ways for sustainable transition – A case study of Hanoi

The transition management approach can help to improve municipal solid waste management in individual cities and city regions. The obsolete technological solutions of waste management cannot support efficient and sustainable urban waste management processes. We would like to present a possible solution to development of the municipal solid waste management system in a high population density megapolis, Hanoi (Vietnam). We examined the development opportunities at three strategic levels (governmental, enterprise and personal levels). We have analyzed the system at strategic, tactical, operational and reflexive levels also, using a transition matrix. Five development aspects and technological directions have been identified, and all of them could be applied at the three decision levels. We came to the conclusion that intervention is needed at all three levels. Based on our results, we have made proposals for the transformation of Hanoi solid waste management structure in the overall organizational structure

Rapid Prototyping for Sheet Metal Products

The aim of this chapter is to evaluate and predict forming limit and then to improve and develop the incremental sheet metal forming (ISMF) processes for complex surface products of sheet metal. The theoretical study was first overviewed and synthesized in order to recognize the effect of geometry, technology parameters, and processing conditions on ISMF process. Finite element method (FEM) simulation study was then used to compare the accuracy of constitutive material models and fracture criteria and propose new equations in order to improve the prediction of FEM simulation for incremental sheet metal forming process. To develop a new technique for improving the formability of sheet metal using ISMF, FEM was also adopted to reduce the cost and time of research. The basic experimental studies were performed to determine the input data for FEM simulation such as tensile data, fracture parameters, and so on. To investigate and compare the simulation results, the incremental sheet metal forming processes for complex shapes were also conducted

The Relationship between Foreign Direct Investment, Current Account and Economic Growth in Vietnam: A Framework for International Capital Flow Management

The relationship between foreign direct investment (FDI), current account, and economic growth is a subject that always attracts the attention of researchers with studies that focus on both developed and developing countries. Many studies have shown that FDI has a positive effect on the growth of countries. However, this capital also brings some risks. Therefore, this study evaluates the relationship between foreign direct investment, current account, and economic growth in Vietnam. Using the VECM method combined with the Bayesian stability test, the research results have shown that, in both the short and long term, FDI and current accounts positively affect Vietnam’s economic growth. Based on research results, we propose policy implications to minimize the negative effects of FDI inflows and make the most of this capital source for the sustainable economic development of Vietnam

On Armstrong relations for strong dependencies

The strong dependency has been introduced and axiomatized in [2], [3], [4], [5]. The aim of this paper is to investigate on Armstrong relations for strong dependencies. We give a necessary and sufficient condition for an abitrary relation to be Armstrong relation of a given strong scheme. We also give an effective algorithm finding a relation r such that r is Armstrong relation of a given strong scheme G = (U,S) (i.e. Sr = S+, where Sr is a full family of strong dependencies of r, and S+ is a set of all strong dependencies that can be derived from S by the system of axioms). We estimate this algorithm. We show that the time complexity of this algorithm is polynomial in |U| and |S|

Investigation on the effect of cross beams in single span bridges under dynamic aspect by using finite element method

In the 1980s and 1990s, most bridges in Vietnam employed simple beam for short-span river crossings that did not need navigation and mainly used the reinforced concrete T-beams or pre-stressed concrete. While the T-frame structure that has hang single span is widely applied for rivers that require navigation...The single girder is a basic span made of pre-stressed reinforced concrete T or I cross section, with spacing ranging from 2.2m to 2.6m, and the absence of diaphragms was a common feature of bridges built during this time period. All horizontal crashes almost have happened on the spans that did not have diaphragms. As a result, the impact force is concentrated mostly on the lateral girders, leading to total damage. Thus, researches to evaluate the effect of diaphragms in the distribution of horizontal impact forces as well as minimizing the damage in the span structures are crucial. This study focuses on simulating and studying the influence of the number and position of the diaphragms in terms of stress, deformation and damage when a collision occurs in order to propose additional and repair solutions to enhance the horizontal resistance of span

Some results related to dense families of database relations

The dense families of database relations were introduced by Järvinen [7]. The aim of this paper is to investigate some new properties of dense families of database relations, and their applications. That is, we characterize functional dependencies and minimal keys in terms of dense families. We give a necessary and sufficient condition for an abitrary family to be R— dense family. We prove that with a given relation R the equality set ER is an R—dense family whose size is at most m(m-1)/2, where m is the number of tuples in R. We also prove that the set of all minimal keys of relation R is the transversal hypergraph of the complement of the equality set ER. We give an effective algorithm finding all minimal keys of a given relation R. We also give an algorithm which from a given relation R finds a cover of functional dependencies that holds in R. The complexity of these algorithms is also esimated

Some problems related to keys and the Boyce-Codd normal form

The aim of this paper is to investigate the connections between minimal keys and antikeys for special Sperner-systems by hypergraphs. The Boyce-Codd normal form and some related problems are also studied in this paper