Revista Facultad de Ingenieria

Since 1991, preprints have increasingly been distributed over the Internet, as opposed to paper copies. Preprints date back to at least the early 1960s, when the National Institutes of Health (NIH) in the United States began circulating preprints in the biological sciences. After six years, journals stopped accepting submissions shared via these channels. Then, in 2017, the Medical Research Council and the Wellcome Trust began accepting citations of preprints in grant and fellowship applications [1], [2].

A vehicle is more stable when the geometric center, center of gravity, and stagnation point are in line. However, the inflow direction and velocity magnitude of the operational environment of road vehicles are varying. This study aims to investigate the aerodynamic behavior of a water-drop-shaped vehicle under side wind conditions. Some essential aerodynamic performances of the vehicle are numerically and graphically analyzed at 0 deg, 10 deg, and 20 deg of side wind directions. The value of the coefficient of drag, drag force, coefficient of lift, and lift force exponentially increases as the yaw angle elevates. The lower part on the area of the front-wheel compartment becomes the critical location indicated by the results on pressure coefficient, friction coefficient, and total wall shear stress distribution along the vehicle surface. Increasing the side wind angle triggers more significant vortex regions generated around the wheel compartment and on the leeward side of the vehicle.

The objective of this paper is to measure seven factors, including Labor, Capital & Scale, Physical Infrastructure, Information Technology Infrastructure, Institutions, Openness to the Economic Environment, and Emission. Furthermore, another objective is to assess which factors impact on Labor Productivity, Capital Productivity, and Gross Domestic Product (GDP) of the Transportation Logistics Industry in Ho Chi Minh. It will also assess how GDP is impacted by Labor Productivity and Capital Productivity. The Methodology used includes Cronbach’s Alpha, Exploratory Factor Analysis, Pearson Correlation and Multivariate regression. Highlight results are Transportation Logistics Industry’s Scale, such as total enterprises of Transportation Logistics Industry impacts on Labor Productivity at Sig. < .001 and Beta = 0.706, impacts on Capital Productivity at Sig. < .001 and Beta = 1.728, and impacts on Transportation Logistics Industry’s GDP at Sig. < .001 and Beta = 0.712, which impacts all in the positive direction. Besides, while Labor Productivity impacts in the same direction on GDP at Beta = 1.006 and Sig. < .001, Capital Productivity does not impact on GDP. Therefore, to develop Transportation Logistics Industry, there is a need to focus on Transportation Logistics Industry’s GDP by boosting its Labor Productivity. Also, there is a need to focus on the Transportation Logistics Industry’s Scale in the direction of increasing total enterprises is important and necessary.

Undrained instability is a failure mode that has been observed in many sandy slopes. However, the highly anisotropic stress states caused by the geometry of the slope have not been duly considered from the experimental point of view. This article studies the influence of the initial stress anisotropy of laboratory samples on the static undrained instability of the Colombian reference sand. Forty-five consolidated undrained triaxial tests were performed, prescribing combinations of different initial void ratios, mean confining pressure, and initial stress ratios. Experimental results allow concluding that: a. the size of the instability zone on the p′ − q plane becomes smaller for larger initial anisotropic stress ratios; b. a novel undrained instability plane can be proposed in the p′ − q − e space to set a boundary between stable and unstable undrained loading conditions; c. mean confining pressure plays a vital role in the estimation of undrained instability for Guamo sand samples under low and medium confining stresses; d. despite multiple factors that influence the onset of undrained instability, a relation can be derived between the undrained instability susceptibility of sandy slopes and the initial stress ratio η0.

In this research, a diesel engine lubricant, modified with Multi-Walled Carbon Nanotubes (MWCNTs) was evaluated. Carboxylic group functionalized MWCNTs were dispersed in 15W40 mineral oil for Diesel engines and retaining ring and cylinder sleeve materials from F300 diesel engine were used for tribological tests. The Nanofluid (0.1 0.5 and 1% wt.) rheological behavior was characterized. Nanolubricants with 1% wt and base oil were evaluated on a Pin-on-Disk test. Results suggest both wear rate and coefficient of friction reduction when MWCNTs are used, while no significant rheological properties changes were observed.