Weight evaluation of factors influencing road flood risk in Mekong river delta
Trang: 1-9 Thai Thi Kim Chi, Thai Thi Kim ChungTóm tắtThe Mekong River Delta is one of the most vulnerable areas in the world. Because of climate change, the risk of road flooding in the Mekong River Delta is increasing. Road flood disaster is considered as a series of damage processes affecting a road under the effect of different factors such as natural and social factors. Thus, index weight evaluation is a critical part in multi-index evaluation as well as road flood risk management. Some main flood-causative factors considered in this paper are road characteristics, climatic factors, hydrological characteristics, geology environmental factors and social factors. The significant criteria of road flood vulnerability are identified. The weight of different criteria was determined using the subjective method based on the Analytic Hierarchy Process (AHP). The obtained weights can be used for the flood risk evaluation and classification, providing valuable information for decision-making process in the road flood management to prevent and decrease the losses of roads during natural disaster like flooding
Moment modification factors for the buckling design of steel beams – new recommendations
Trang: 10-19 Tien Nguyen Duy, Phe Van PhamTóm tắtWhen a unbraced flexural steel beam is subjected to a ununiform moment distribution, a simplified moment modification factor (denoted as Cb) should be evaluated for the design of the buckling resistance of that member. However, typical standards for the buckling design of steel structures (e.g., American AISC A360, Australian AS-4100, Canadian CSA S16, Eurocode 3 and Japanese standards) currently recommend different design equations for the factor. Also, such equations are based on simplified expressions those are not exact solutions. Thus, the present study firstly revise the standard equations to discuss their advantages and disadvantages in application. Also, a numerical solution based on a finite element analysis package is then conducted in the present study to predict the Cb factor. The numerical solution is successfully validated against available research results. Based on the comparison of the modification factors between of the present numerical study and those based on the design standards, it is observed that the modification factors based on the current design standards maybe not safety enough to predict the buckling resistances in several loading cases. The present study finally recommends a new modification more on the safe side for the Cb factor to ensure a conservative design
Trang: 20-34 Vu Ba ThanhTóm tắtThe phase-field method has become a robust tool to describe the complex crack nucleation and propagation in heterogeneous materials. In these materials, an interaction between bulk brittle damage and interfacial damage through the splitting the strain tensor into a bulk strain part and a jump strain part at the interfaces. Moreover, the material response of the heterogeneous materials in tension and compression, the bulk strain part needs to be decomposed into a positive part and a negative part. However, most of the previous works, these decompositions do not verify the negative part be orthogonal the positive part, which lead to the inaccuracy in the material mechanical behavior. To solve the shortcomings, the strain orthogonal decompositions problem that is applied to decompose the bulk strain in our work. In the present work, author combined the phase-field modeling taking into account interfacial damage with the problem of the bulk strain orthogonal decompositions by two proposed solutions. The successful prediction of the crack propagation for the inclusion-matrix structures and the multi-phases materials of X-ray computed tomography (XR-CT) images by two proposed solutions will be demonstrated in several numerical examples.
Trang: 35-46 Van Hung Bui, Anh Vu Ngo, Quang Son KhuongTóm tắtThe abrasive water jet (AWJ) is a non-traditional process that can be employed to machine a variety of materials that are significantly difficult to machine using conventional machining processes. This paper presents an experimental investigation conducted to evaluate the influence of the jet tilt angle, a kinematic process parameter, on the characteristics of the milled pocket as milling aluminium alloy 6065. The influences of this parameter are assessed by measuring differences in the depth of the milled pocket, the width, and the slope of the pocket wall. It is found that as the jet tilt angle decreases, it has a significant influence on characteristics of the milled pocket due to changing the material removal mechanism during the erosion process. Insight the influence of the jet tilt angle, this work paves a good fundamental for developing strategies for controlled 3D AWJ machining of complex shapes and improving the quality of the milled surfaces
Structural and thermal investigations of rolling tires in a flat road
Trang: 47-57 Thanh Cong Nguyen, Khanh Duy Do Cong, Cong Truong DinhTóm tắtRubber is an essential component of a pneumatic tire. In general, the tire, or the rubber part, is heated by the hysteresis effects caused by the deformation of the rubber part during the operation. Besides, the tire temperature depends on many factors, such as inflation pressure, vehicle loading, car speed, road tire, environment condition, and tire geometry, etc. This study focuses on the finite element approach to compute by simulating the temperature distributions of a steady-state rolling tire. For simplicity, the tire is assumed to be composed of rubber, body-ply, wire, and rim only. The nonlinear mechanical behavior of the rubber is characterized by a Mooney–Rivlin model, while the other parts are assumed to be a linear elastic material. The coupled effects of the inflation pressure and vehicle loading are investigated. Hysteresis energy loss is used as a bridge to link the strain energy density to the heat source in rolling tires. The steady-state thermal analysis may obtain the temperature distribution of rolling tires. On the other hand, an efficient computational process is being introduced to decrease the time for coupled 3D dynamic rolling simulation of the tire. The simulation results show that loading is the main factor in determining the temperature field
Trang: 58-71 Minh Ngoc Ngo, Le Ha Phuong Hoang, Duc Manh Nguyen, Anh Duong Khuc, Thanh Tung Tran, Van Hao Hoang, Minh Hieu NguyenTóm tắtTo sustain the development of urban transportation, electrifying private motorized vehicles is a top goal besides the development of public transport. This study aims at investigating the influential factors of continuance intention to use electric motorcycles based on an extension of Expectation Confirmation Theory (ECT). To empirically test the proposed conceptual framework, Partial Least Squares Structural Equation Modeling (PLS-SEM) and the data of 394 students in Hanoi collected in August 2022 are used. The results show that perceived usefulness and satisfaction directly facilitate the continuance intention while perceived ease of use and expectation confirmation have indirect positive effects. Female students tend to have less intention to continue using electric motorcycles while those living in non-urban districts seem to have a higher continuance intention. The prediction capacity of the model is high with over 65% of the variance of continuance intention being explained by (independent) constructs. Based on the findings of influential factors, the authors propose practical implications for triggering the use of electric motorcycles among students
Trang: 72-80 Van Kha Pham, Thi Thu Ha TranTóm tắtModel for energy and exergy analysis of absorption refrigeration using waste heat from textile factory has been built. The analysis that uses different models of heat exchangers are the overall heat conductance (UA) model, and the effectiveness model. The result show that the exergy loss in the generator and absorber are the larger than condenser and evaporator. Therefore, it is necessary to focus on improving these two important devices in absorption chiller. For the convenience of system operation, the research analyzed the effects of generator inlet temperature and solution pump mass flow rate on the energetic and exergetic performance of the absorption chiller. The study results indicated that the exergy efficiency of the absorption chiller decrease from 0.2776 to 0.2146 when increasing the solution pump mass flow rate from 1.5 kg/s to 2.5 kg/s and the generator inlet temperature from 80 oC to 98 oC. Meanwhile, energy efficiency will increase slightly initial from 0.769 to 0.779 and then decrease from 0.779 to 0.776 as the generator inlet temperature increases from 80 oC to 98 oC when solution mass flow rate is 1.5 kg/s. And energy efficiency decreases from 0.769 to 0.734 when the solution pump mass flow rate increase from 1.5 kg/s to 2.5 kg/s
Exploring factors associated with riding attitudes of motorcyclists in Vietnam
Trang: 81-96 Vuong Xuan Can, Mou Rui fang, Vu Trong Thuat, Cu Thi Thuc AnhTóm tắtThe riding attitude of motorcyclists is an important key in the investigation and analysis of motorcyclists' behaviors in traffic flow. The main aims of this study are to explore factors associated with the riding attitudes of motorcyclists in Vietnam using a self‐reported questionnaire with Exploratory Factor analysis (EFA) and Confirmatory Factor Analysis (CFA) approaches. This study was conducted from January to March 2019, surveying randomly selected motorcyclists at least the age of 16 years in Hanoi, the capital of Vietnam. A sample consisting of 716 motorcyclists was used to analyze EFA and CFA. The results presented 11 items that were confirmed to compose the Vietnamese motorcyclists’ riding attitudes. Three factors, including attitude towards traffic flow, attitude towards rule obedience and speeding, and attitude towards fun riding were explored in this study. Besides, the study also showed that there were differences in riding attitudes among groups by age group, education level, riding experience, related to accidents in the last three years, and involvement in near-accidents in the last three years. The results of this study can inform the future study of the risky behaviors of Vietnamese motorcyclists
