Performance of Concrete Beams Reinforced with Various Ratios of Hybrid GFRP/Steel Bars

This paper aims to study the flexural behavior of concrete beams reinforced with hybrid combinations of GFRP/steel bars. To this purpose an experimental program was carried out on four concrete beams reinforced with Glass Fiber Reinforced Polymer (GFRP) and twelve hybrid GFRP/steel Reinforced Concrete (RC) beams. Flexural behavior of the tested beams such as stages of response, failure modes, crack patterns, stiffness, toughness and ductility were analyzed. The experimental results showed that depending on GFRP/steel reinforcement configurations, the behavior of hybrid GFRP/steel RC beams undergoes three or four stages, namely: pre-cracking stage; after concrete cracking and before steel yielding; post-yield stage of the steel bar until peak load and failure stage. Totally six failure modes of hybrid RC beams are reported depending on reinforcement rations and configuration. The effect of reinforcement configuration and ratio of GFRP to steel (ρg) on the crack patterns, stiffness, ductility and toughness of hybrid RC beams are significant. Based on the non-linear deformation model, an analytical model has been developed and validated to determine the steel yielding moment and ultimate moment of hybrid GFRP/steel RC beams. It could be seen that the experimental values were in good agreement with the predicted values

NOVEL HPLC-UV METHOD USING VOLATILE BUFFER FOR SIMULTANEOUS DETERMINATION OF AMLODIPINE BESYLATE AND ATORVASTATIN CALCIUM

Objective: The purpose of this work was to develop and validate a novel HPLC-UV method using triethylamine (TEA) as a volatile buffer for simultaneous determination of amlodipine besylate (AML) and atorvastatin calcium (ATV).Methods: System suitability, linearity, limit of detection (LOD), limit of quantification (LOQ), selectivity, accuracy, and precision was validated using Hitachi L-2000 system with detector: DAD L-2455 at a detected wavelength of 245 nm. Stationary phase: Phenomenex Luna RP-C18 (250 mm x 4.6 mm, 5 µm) and mobile phase: acetonitrile-methanol-TEA pH 4.0 (ratio 52:18:30 v/v/v) were used. Samples' volume of 20 µl was run at room temperature with the flow rate at 1 ml/min.Results: The linearity demonstrated good correlation in the concentration range at 2-40 ppm and 4-80 ppm for AML and ATV, respectively. The method was repeatable with relative standard deviation (RSD) of the intermediate precision test less than 1%. The recovery rate was 100.03% and 99.58% for AML and ATV, respectively. The method was also validated for dissolution studies with excellent compatibility.Conclusion: A new, simple and easy HPLC-UV method was successfully developed and validated for the determination of AML and ATV in both quantification test and dissolution test.Keywords: Amlodipine, Atorvastatin, Simultaneous, Dissolution, HPLC, Quantification, Volatile buffe

Long-term Deflections of Hybrid GFRP/Steel Reinforced Concrete Beams under Sustained Loads

One of the solutions to improve the flexural behavior of Glass fiber reinforced polymer (GFRP) reinforced concrete (RC) beams is the addition of tensile longitudinal steel reinforcement. The numerous studies to date on hybrid GFRP/steel RC elements have mainly focused on the static and short-term responses, very little work has been done regarding the long-term performance. This paper presents experimental results of time-dependent deflections of cracked GFRP and hybrid GFRP/steel RC beams during a 330-day-period in natural climate conditions. Three hybrid GFRP/steel and one GFRP RC beams with dimensions 100×200×2000 mm were tested in four-point bending. Different steel reinforcement ratios were used to evaluate the effect of the steel reinforcement on the long-term behavior of the beams. Experimental results show that the immediate deflections are inversely proportional to the additional steel reinforcement. With the same initial instantaneous deflection, the total deflection increases when increasing the steel reinforcement ratio. Also, temperature (T) and relative humidity (RH) significantly affect the long-term deflection of the tested beams. The measured long-term deflections were found to be in good agreement with the theoretical values calculated from the proposed method. However, there was an overestimation when using ACI 440.1R-15 or CSA-S806-12 procedures

Concrete beams using seawater and sea sand reinforced with steel and GFRP rebars exposed to marine environment: An experimental study

Using fresh water and river sand in concrete mix composition makes a lot of negative impacts on resources and the environment while the source of sea sand and sea water is abundant and less harmful to the environment. However, sea sand and seawater in concrete can cause severe corrosion of the reinforcement, reducing the durability and bearing capacity of the structure. This paper illustrates the results of a comparative study on the flexural behavior of six corroded seawater sea-sand concrete (SWSSC) beams. The corrosion process of two concrete beams reinforced with traditional steel bars and four concrete beams reinforced with a combination of glass fiber reinforced polymer (GFRP) and steel bars was coupled by the effect of seawater exposure and sustained load. It was found that after exposure to a marine environment during the period of 60 months the GFRP bar retains surface integrity, meanwhile, the steel bars were significantly corroded with a cross-sectional area loss of approximately 13.93%. The decrease in bending stiffness, yield load, and ultimate load of the RC beams was found due to the deterioration of SWSSC and corrosion of steel bars.

Concrete beams using seawater and sea sand reinforced with steel and GFRP rebars exposed to marine environment: An experimental study

Using fresh water and river sand in concrete mix composition makes a lot of negative impacts on resources and the environment while the source of sea sand and sea water is abundant and less harmful to the environment. However, sea sand and seawater in concrete can cause severe corrosion of the reinforcement, reducing the durability and bearing capacity of the structure. This paper illustrates the results of a comparative study on the flexural behavior of six corroded seawater sea-sand concrete (SWSSC) beams. The corrosion process of two concrete beams reinforced with traditional steel bars and four concrete beams reinforced with a combination of glass fiber reinforced polymer (GFRP) and steel bars was coupled by the effect of seawater exposure and sustained load. It was found that after exposure to a marine environment during the period of 60 months the GFRP bar retains surface integrity, meanwhile, the steel bars were significantly corroded with a cross-sectional area loss of approximately 13.93%. The decrease in bending stiffness, yield load, and ultimate load of the RC beams was found due to the deterioration of SWSSC and corrosion of steel bars.

LAKESCAPE UNDER URBAN DEVELOPMENT IN DONG DA DISTRICT, HANOI CITY

Joint Research on Environmental Science and Technology for the Eart

Parameter Identification Method for a 3-phase Induction Heating System

This paper describes a new method for the on-line parameter estimation of an induction heating system. Simulations and experiments are presented in order to measure its impedance matrix for more exact control in closed loop. In previous papers, various parameter identification methods including off-line methods were introduced and compared for current inverters. It has been demonstrated that parameter identification is necessary to achieve good control of the inductor currents. A “pseudo-energy” method for a simple and fast implementation is compared to a classical “V/I with phase shift” method. They are experienced on a reduced power 3-phase coupled resonant system supplied with voltage inverters with satisfying results

The acceptance of mobile applications for accommodation booking in Vietnam: Case of gen Z

The development of technology and smart mobile devices such as phones and tablets has changed the behavior of tourists when booking tourism services. Based on the technology acceptance model, this study aims to explore the factors influencing the intention to use mobile applications for accommodation booking among GENZ in Vietnam. The analysis of 218 users revealed that four factors influence the behavior of using mobile applications for booking: performance expectancy, effort expectancy, social influence, and hedonic motivation. In addition to identifying the factors affecting usage intention, this study also proposes implications to assist developers and providers in improving their applications and developing suitable product strategies for the future

XGV-BERT: Leveraging Contextualized Language Model and Graph Neural Network for Efficient Software Vulnerability Detection

With the advancement of deep learning (DL) in various fields, there are many attempts to reveal software vulnerabilities by data-driven approach. Nonetheless, such existing works lack the effective representation that can retain the non-sequential semantic characteristics and contextual relationship of source code attributes. Hence, in this work, we propose XGV-BERT, a framework that combines the pre-trained CodeBERT model and Graph Neural Network (GCN) to detect software vulnerabilities. By jointly training the CodeBERT and GCN modules within XGV-BERT, the proposed model leverages the advantages of large-scale pre-training, harnessing vast raw data, and transfer learning by learning representations for training data through graph convolution. The research results demonstrate that the XGV-BERT method significantly improves vulnerability detection accuracy compared to two existing methods such as VulDeePecker and SySeVR. For the VulDeePecker dataset, XGV-BERT achieves an impressive F1-score of 97.5%, significantly outperforming VulDeePecker, which achieved an F1-score of 78.3%. Again, with the SySeVR dataset, XGV-BERT achieves an F1-score of 95.5%, surpassing the results of SySeVR with an F1-score of 83.5%