In this paper, we establish variation of constant formulas for both Caputo and Riemann- Liouville fractional difference equations. The main technique is the Z -transform. As an application, we prove a lower bound on the separation between two different solutions of a class of nonlinear scalar fractional difference equations.

The transport system is considered the “backbone” of the urban development. Along with the rapid economic development, the urban road transport system is being paid attention and invested by Hanoi city. By the year 2050, The Hanoi municipal government is expected to complete and hand over for use about 317 urban road transport projects. Due to the high demands of social and economic efficiency, the urban road transport projects in Hanoi face many risks. In which, there are 13 high dangerous risks for the urban road transport project in Hanoi. These risks have the high probability and severity impacted on the outcome of the projects. The project participant’s risk management standpoint will determine the solutions to respond the respective risks, thereby affecting the results of the project. In this paper, the authors compare the risk management standpoint of three main project participants, including owner/project management board, consultant and main contractor/subcontractor. The difference of the risk management standpoint is shown clearly by the project participants’ assessments of 13 high dangerous risks.

The world has been implementing Building Information Modelling (BIM) successfully to construction projects from small to large scale. In Vietnam and many other countries, BIM is also widely applied in different fields of the construction industry. However, there are still many problems that need to be solved. One of those is to determine the necessary BIM competencies, thereby develop BIM personnel recruitment standards. The article identifies the competencies as well as evaluates their importance when supporting the recruitment of BIM personnel in construction enterprises in Vietnam. Through survey forms such as survey on online recruitment, expert interviews, and survey forms, the study is conducted with Likert scale, relative importance index (RII) for result analysis and ranking the importance of BIM competency for three distinct group of positions in Vietnam. With this result, the authors hope that the study will be an important reference, contributing to the development and concretization of the required competency criteria in the recruitment of BIM personnel in Vietnam and other similar countries.

Materials play an important role in determining the quality and cost of a building, especially in the context of Vietnam’s rapid urbanization today. This study aims to analyze the status quo for supplier selection for construction projects in a developing country, Vietnam. Questionnaires are designed to conduct a survey among several contractors to assess the current situation of how Vietnamese construction enterprises select their material suppliers. Senior managers, project managers, site commanders, site engineers, foreman, office staff of contractors were interviewed. Based on result analysis of 117 valid responses, the most important criteria to consider when selecting material suppliers have been identified, with the most influential ones being price, delivery time, and material quality. However, the supply of materials still reveals some constraints that must be overcome. Vietnamese construction firms should pay more attention to supplier selection to optimize material delivery efficiency. This research contributes to the understanding of the status quo for supplier selection for construction projects in a developing country. This means contractors can adopt suitable measures to select material suppliers for construction projects.