Science & Technology Development Journal - Engineering and Technology

An experimental research to determine the fluidized bed regime of pepper in the fluidized bed drying process

2021-12-25T13:50:50+00:00

This is an experimental study to determine that the minimum fluidization velocity, the fluidized bed height, and the pressure loss through the grain layer depend on the thickness of grain layers and moisture content of materials. The drying materials used in this study are fresh pepper and dried pepper of which moisture content is 54.2% and 12%, respectively. All the experiments are conducted with the thickness of the pepper layer ranging from 4mm to 44mm while the wind speed ranging from 5 m/s to 11m/s. From the result of experimental analysis, it can be seen that the minimum fluidization velocity of an air stream through fresh pepper ranges from 5.2m/s to 6,5m/s. The pressure drop of air stream through the fresh pepper is 225Pa while 147Pa for dry pepper, corresponding to the grain thickness of 37mm layer. By comparing the results determined from these experiments with computational models and some available correlations, the computational models of Fedorov, Baeyens-Geldart and Leva all match the experimental data collected from the pepper material. The correlation between the calculated and experimental results has a negligible error, the tendency to increase pressure loss depends on the thickness of grain layer is also quite similar. From the experimental data results obtained by determining the pressure drop through the pepper layers which depends on the thickness of both fresh pepper and dried pepper, the linear equations of the first order are established with high credibility.

Analysis of Eye Tracking images to identify children with Autism Spectrum Disorder

2021-12-25T20:38:16+00:00

A number of children with Autism Spectrum Disorder (ASD) are growing to become a big problem in society at the present time. Autism is the neurological disorder that makes the children feel inferior in social communication. Identifying individuals with early autism (under 3 years of age) is difficult and there is still not any medical test for rapid detection of autism. Currently, the clinical diagnosis is mainly based on the observed behavior of the child, and besides, educational and psychological tests are also applied. Eye movements have an important role in an individual's perception and attention in social activities. Non-invasive detection and tracking techniques of the eye movement have been developed over many decades. Nowadays, the Eye Tracking is a technological process that enables the measurement of eye movements, eye positions, and points of gaze. In other words, eye tracking identifies and collects a person’s visual data of the eyes in terms of location, objects and duration. It is applied for a variety of different research methods to investigate human behavior. In particular, the Eye Tracking method makes an application for identifying people with Autism Spectrum Disorder (ASD), it has been not only a wide study but also a great interest in recent years. This article provided an overview of children's visual attention with Autism Spectrum Disorder and children with Typical Development (TD). The study has focused on exploring the difference in observed behavior of ASD children and TD children. This study used the DBSCAN (Density-Based Spatial Clustering of Applications with Noise) clustering algorithm for grouping a set of Eye Tracking data, which were collected by the test of children’s visual attention to a variety of images. The classification of Eye Tracking data was based on the feature parameters, which were extracted from analyzing data. Moreover, a model for classification and identification of Eye Tracking image data of children groups with ASD and TD was built on Deep Learning algorithms. In this study, the chosen algorithm was Multilayer Perceptron. The children's eye movements dataset was extracted from the paper "A dataset of eye movements for the children with autism spectrum disorder" by Huiyu Duan et al. The results showed that using the Eye Tracking data is highly promising in identifying children with ASD by analyzing the observed behavior of children on images, especially on human images.

Assisting in design of marine propeller using genetic algorithm

2021-12-25T20:52:20+00:00

Research on selecting marine propellers suitable for the main engine and ship hull form plays an essential role in designing transportation vessels, especially container ships operating at low-speed range. In the preliminary design stage, the experimental marine propeller Wageningen (B-series) were selected because they are suitable for the transportation vessels and have reliable experimental data for thrust and torque coefficient. Experimental propeller selection schemes are often based on the recommendations of the graph and data; the design engineer's decision is restricted in the selection of propeller geometrical parameters. For propulsion equipment for transportation vessels, thrust characteristic and torque characteristic play an essential role in ensuring the speed according to the design mission and economic efficiency during the marine vehicle operation. In this study, the thrust coefficient and torque coefficient are integrated with the optimization technique based on the genetic algorithm, thereby successfully constructing an algorithm to support the recommendation of specific geometrical parameters of the marine propeller considering the influence of the main engine and ship hull form. The calculation results show that the calculated thrust coefficient and torque factor satisfy the design characteristics and improve the overall performance of the propeller and transportation vessels.

Experimental study on thermal performance of ethanol loop heat pipe with flat evaporator under gravity – assisted condition

2021-12-25T21:17:19+00:00

Nowadays, extreme growing of telecommunication and information technology causes the significant changes in the electronics belonging to the high-performance computer, data centers that are miniaturizing in their size and increasing the heat power dissipation. As a result, it is important to study on new cooling methods rather than conventional air cooling to warrant electronic device operate durably and stably. Besides, saving electricity power consumed by cooling systems is another considerable concern. Loop heat pipe, a passive heat transfer device which functions based on phase change processes and natural forces like gravity or capillary force, has been being one of potential solutions for the above challenges. In this paper, a loop heat pipe with flat evaporator was fabricated to investigate its cooling characteristics during start-up, stable operating period at different heat loads under gravity–assisted condition. This loop heat pipe was charged with ethanol whereas sintered stainless steel wick was the capillary structure. Time for successful start-up shortened from 13 minutes to 4 minutes as heat load increased from 30 W to 225 W. When heating power supplied to loop heat pipe’s evaporator was adjusted from 30 W to 400 W (14.8 W/cm2), the heating block surface’s temperature increased from 33oC to 133oC. This temperature could be maintained below 85oC, electronics limitation temperature in industry, if heat power released from the heating block is smaller than 220 W (8.14 W/cm2). Besides, the change of different types of thermal resistance such as total thermal resistance, evaporator and condenser thermal resistances with heating power is discussed detail in this paper.

Settling behaviour of irregular-shaped polystyrene microplastics

2021-12-25T21:33:59+00:00

Microplastics are emerging pollutants that can pose threats to aquatic ecosystems by carrying toxic additives to the food web. Their abundance has been reported in many waterways globally, including the Sai Gon River, Vietnam. A good understanding of microplastic sinking behaviours can help predict the distribution and removal of these pollutants in water. Microplastic dynamics are still mostly assumed to be similar to that of suspended sediment. However, MPs possess many artificial properties that can make them move distinctly in the water from suspended sediment like densities, structures, shapes, and surface properties. This research, therefore, aims to investigate the correlation of the polystyrene microplastic size and irregular shapes with its vertical movement. The experiments employed the Particle Tracking Velocimetry (PTV) method and an automatic image processing algorithm to simultaneously measure MP geometrical properties and settling velocity while freely settling in a still water column. We found that the circumscribed diameter is the most appropriate geometrical parameter to represent MP size. The settling velocity of irregular-shaped polystyrene microplastics in size of 0.2 to 0.9 mm is mostly between 0.5 and 2 mm/s, half of the sediment but four-fold that of biological aggregates at the same size. The settling velocity increases two-fold when MP size enlarges from 0.2 to 0.9 mm. The shape irregularity can slow down the sinking of large microplastics but do not affect the vertical movement of microplastics smaller than 0.32 mm. The ratio between microplastic projected area and the area of the smallest circumscribed circle was found to be the two-dimensional representation of three-dimensional shapes in the correlation between size and settling velocity. Therefore, the fitting curve equations suggested herein can be used as a simple tool to estimate the settling velocity of irregular-shaped polystyrene microplastics found in many in-situ sampling campaigns.

A novel five-level neutral-point-clamped inverter with an auxiliary DC source

2021-12-25T21:51:55+00:00

Multi-level inverters have drawn much intention from researchers and industry, in which 3-level inverters have been widely used in practice. One of the most interesting issues is to increase the number of levels to achieve higher performances such as large power, high voltage and low harmonic distortion. Basic multilevel inverter configurations such as neutral point clamping diodes, flying capacitor clamping, and cascaded inverters have their own disadvantages when increasing the number of levels. To overcome these problems, different hybrid multilevel inverters have been proposed. As results, there are a lot of five-level hybrid inverters designed for practical applications. This paper proposes a new hybrid 5-level neutral point clamped inverter by adding auxiliary DC source. The novel hybrid inverter shows its performances comparable to the ideal NPC inverter fed by 4 ideal DC sources, and requires hardware simpler than cascaded and flying multilevel inverters. It has a good ability of self-balancing of the voltages across the DC capacitors. Consequently, simple and effective PWM control strategies can be utilized that enables achieving high working performances. The paper content consists of analyzing of the proposed hybrid inverter configuration, investigating the voltage balance on the DC capacitors, validating control characteristics and studying output performance when applying the carrier based pulse width modulation control. The analysis and characteristics of the proposed configuration are verified through simulation results using MATLAB/SIMULINK.

Structural damage detection in steel frames using modal strain energy method and genetic algorithm

2021-12-27T04:10:33+00:00

In recent years, the field of structural health monitoring (SHM) has been receiving the attention of many researchers. In particular, vibration-based structural damage detection methods have proven to be highly effective in civil engineering, mechanical engineering, aerospace engineering, … This paper presents a two-step procedure for damage detection in steel plane frame structures. In the first step, the damage locations in the frame are detected by Modal Strain Energy Index (MSEBI). This index is calculated on the difference from the modal strain energy value of every element before and after damage. In the second step, the damage extents are identified by Genetic Algorithm (GA). The objective function is established on the basis of the change of modal strain energy. A plane steel frame model is built by the finite element method. The results of the frame’s free vibration analysis are the input data of the proposed damage detection procedure. In order to improve the accuracy of the damage localization, the MSEBI is determined using the combination of the frame's first four bending mode shapes. The proposed method gives highly accurate results in detecting the damage’s location and extent for various damage scenarios.

A novel PWM technique to eliminate common-mode voltage for single-phase three-level T-NPC inverter

2022-01-14T11:10:18+00:00

This paper presents a new pulse width modulation (PWM) technique in order to eliminate common mode voltage for a single-phase full H-bridge T-NPC inverter. Three-level NPC inverters are commonly used in grid connected applications or as UPS backup power for industry. In addition to abilities such as to withstand high voltage, and reach output voltage and current with low harmonic distortion, three-level NPC inverter is advantageous for mitigating common mode voltage and leakage current. The new proposed PWM technique is based on the switching state table of the three-level H-bridge T-NPC inverter that containing many switching states with zero common mode voltage. Furthermore, implementation of PWM control for single-phase three-level T-NPC inverter configuration can decrease voltage stress on the output and reduce output voltage distortion compared with bipolar PWM control technique for two-level H-bridge inverter. In this paper, the sine wave carrier PWM technique is analyzed, designed and modelled based on the switching table. The analytical analysis will be evaluated using MATLAB/SIMULINK. Simulation results of the proposed PWM technique for three-level T-NPC inverter are compared with conventional techniques without common mode voltage elimination; the quality of the three-level T-NPC inverter is also compared to that of traditional two-level inverter. The power loss content is evaluated using PLECS software. The obtained results confirm the advantages of the eliminated common mode voltage PWM technique in the three-level T-NPC inverter configuration.

The Application of Triclosan in antibacterial finishing on 100% cotton fabric

2022-01-14T13:03:57+00:00

The demand for antibacterial fabric has been recently increasing in the medical textiles. The fibers used in textile products, especially those made from natural fibers with a large surface area and good moisture-retention capacity, provide a favorable condition for microbial growth. They are present almost everywhere and multiply rapidly, depending on moisture, nutrients, and the environment in which they live. The growth of microorganisms on textile products has caused a series of undesirable effects, not only on the product but also on the user of the products. Cotton fabric is easy to wrinkle. When exposed to a humid environment, it is susceptible to damage caused by microorganisms. Therefore, antibacterial treatment for Cotton fabric 100% is a important requirement in the textiles and garments depending on the intended use and is a prerequisite for fabric products in the medical field. Many antibacterial agents for textiles are already known such as organo-metallics, phenols, quaternary ammonium salts. Triclosan is a popular antibacterial chemical. Triclosan is present everywhere in life from consumer products such as toothpaste, soap, detergents, toys, household appliances to cosmetics. Especially Triclosan is an antibacterial agent used quite a lot in the textile industry. Triclosan with chlorinated phenol, a synthetic chemical, is common and potential antibacterial agent. In this study, The technical parameters were investigated include Triclosan concentration, dipping time, drying temperature, citric acid concentration to evaluate the effects of treated parameters on the antimicrobial efficiencies of the 100% cotton fabrics. The results show that cotton fabrics after finishing treatment with Triclosan and applying citric acid (CA) as important bonding chemical have good antibacterial ability and also have improved durable antibacterial properties after 5 launderings. The antibacterial properties of treated cotton fabrics was evaluated based on ASTM E2149-01 standard, the experiment was done with E.Coli ATCC 25922 and S. Aureus ATCC 6538.

Finite element modeling of tapered concrete filled steel tubular columns under axial compression

2022-01-14T13:20:16+00:00

Concrete filled steel tubular (CFST) column is a kind of composite structure, in which a concrete core is confined within a steel tube. Thanks to the interaction between the steel tube and the concrete core, the compressive load carrying capacity of concrete is increased. This phenomenon is usually referred to as the ``confinement effect''. Correctly modeling the confinement effect, i.e. how the confined concrete behaves under certain types of loadings, is essential in analysis and design of CFST columns. Most of the current works focus on straight columns. In this paper, a novel finite element model is developed in ABAQUS software to analyze the nonlinear behaviors of CFST columns under axial compression, which is suitable for both uniform columns (i.e. the crosssectional area is constant) and tapered columns (i.e. the cross-sectional is continuously varied with respect to the length of the column). The tapered columns are approximated as columns with piecewise constant cross sections, linearly varying from one end to the other end. Geometrically, as the number of piecewise constant cross sections increases, the model converges to the tapered column. In each segment of constant cross-sections, the material behavior of straight column is assumed. Thus, the current model is an extension to existing models for straight CFST columns. Two types of cross sections are investigated: circular shape and rectangular shape. These two cross sections are also the most popular ones in real life. Pre-processing in ABAQUS, i.e. setup of the model, is conducted via a subroutine written in Python script. The ability of the proposed numerical model in load carrying prediction is demonstrated through comparison with experimental data previously reported in the literatures by other authors.

Overview of lightning location systems

2022-01-14T10:49:53+00:00

Lightning location systems provide valuable and vital data for study of lightning on the earth. Developed nations already built not only one but aslo many lightning location networks in their territories in order to collect highly reliable national dataset of lightning. Moreover, these national lightning detection systems are linked together to increase both the collecting range and the accuracy. However, in Vietnam, lightning location systems are not payed enough attention on. Therefore, the authors attempt to provide an overiew of lightning location systems and their importance to the field of lightning protection in this research. The paper provides an overview of the operating principles of popular lightning location systems in the world. Besides, typical lightning activity data extracted from Blitzortung lightning location system in Vietnam are presented. In addition, a number of studies around the world using lightning data from these location systems to improve the lightning protection performance of transmission lines are briefly introduced. These results and information show the vital role of lightning location systems not only in lightning protection but also in analyzing the causes of failures on power systems.