The Application of Calcium Carbonate CaCO3 and Titania TiO2 for Color Homogeneity and Luminous Flux Enhancement in PC-LEDs

This article studies the development method of pc-LED, a phosphor-converted lighting emitting diode, with scattering enhancement particles (SEPs) at 7000 K correlated color temperature. The pc-LED is an advanced lighting solution that has been applied in many different categories; nonetheless, to keep up with the demands of modern lighting, the pc-LEDs need to enhance the color homogeneity and luminous flux. The detailed experiments on the two SEPs used in the articles are also presented. The experiments include combining each of these SEPs with a yellow phosphor Y3Al5O12:Ce3+ to test their properties and influences on the lighting of pc-LEDs. The scattering coefficients, the anisotropic scattering, the reduced scattering, and the scattering amplitudes at 450 nm and 550 nm are the subjects of SEPs study. The LightTools program is used to create the simulation of pc-LED, the results of the optical simulation will then be verified with the Mie-scattering theory. The findings of the research conclude that TiO2 particles are the best for the growth of color homogeneity while CaCO3 particles are effective in limiting the color deviation in correlated color temperature. Even though the SEPs benefit the lighting performance, their concentration must be managed to be under an acceptable amount to ensure desired results and avoid unwanted damages.This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

Determination of the Effect of Soil Particle Size Distribution on the Shear Behavior of Sand

Many geotechnical problems require the determination of soil engineering properties such as shear strength. Therefore, the determination of the reliable values for this parameter is essential. For this purpose, the direct shear test, as one of the oldest tests to examine the shear strength of soils, is the most common way in laboratories to determine the shear parameters of soil. There are far too many variables that influence the results of a direct shear test. In this paper, a series of 10 × 10 cm direct shear tests were carried out on four different poorly graded sands with different particle size distributions to determine their shear behaviors. Four different poorly graded sands with a different median diameter or medium value of particle size distribution (D50) (0.2, 0.53, 1.3, and 2.3 mm) has been selected, and about 40 direct shear tests were conducted. It was concluded that a soil’s friction angle is affected by coarse-grained material. Accordingly, sandy soils with bigger particle sizes record a higher friction angle than soils containing small particles. The investigations also showed that sand with bigger particle sizes has a higher dilation angle. In addition, a non-linear regression analysis was performed to establish the exact relationship between the friction angle of the soil and the characteristics of the soil particles. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

Sliding Mode Load Frequency Regulator for Different-Area Power Systems with Communication Delays

In this article, a sliding mode control (SMC) is proposed to deal with the frequency deviation problem in interconnected time-delay power systems (ITDPS) with two source power generations. First, the proportional and integral switching surface is used for each area to guarantee the frequency deviation reach zero in normal operating conditions. Then, the stability of the system is ensured with a new Linear Matrix Inequality (LMI) via Lyapunov stability theory. In addition, the SMC law is designed to guarantee the finite time eachability of the system. Finally, impacts of certain physical constraints affecting dynamic performance of the power network such as time-delay is proposed to consider the signal delay in the controller. Effectiveness of the suggested method is validated by simulation studies on the load frequency control under time-delays in the two-area, the step load disturbance and the mismatched uncertainty.This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

Optimum Design for Soil Nailing to Stabilize Retaining Walls Using FLAC3D

The behavior of a reinforced soil system depends on parameters such as the structural geometry, execution steps, density and mechanical properties of the soil, density of reinforcement materials, deformation, and flexural stiffness of reinforcement materials. A critical parameter in the design of a soil-nailed system is the optimal use of materials with respect to cost. It is necessary to find an optimal design that is cost-effective within the parameters affecting the behavior of the nailed system. A common problem in nailed excavations is an increase in the excavation depth beyond the initial design of the wall, which will require more reinforcements. In this research, we used one approach not used before the method is placing one and two rows of long nails placed at the appropriate depth. In this study, a comparison between safety factor, horizontal displacement, and lateral pressure behind the wall has been made at two nail placement depths using FLAC3D finite difference software that reveals the optimal depth for efficiency is approximately at the middle of the finished wall height. When the number of reinforcement nails with the same lengths was considered, the installation of two rows of nails in comparison with 5 or 3 rows of nails reduced the maximum wall displacement to a greater extent. A greater factor of safety was achieved. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

An Improving Hysteresis Current Control Method Based on FOC Technique for Induction Motor Drive

The paper presents an improving speed control method using a field-oriented control (FOC) technique for the hysteresis current (HC) controller in the induction motor drive. The basic principle of a controller applying hysteresis band current is comparing reference currents and the measured currents to generate switching pulses for controlling an inverter. In the typical FOC for the HC controller, the rotor flux angle’s value will increase to infinity due to the integral algorithm’s error accumulation. This problem can lead to the faulty operation of the induction motor drive (IMD) system. In this paper, a current model with the advantage of precisely determining the periodic rotor flux angle is used in the FOC technique to provide reference currents for the current controller. The rotor flux angle will periodically change according to the motor speed in the range [-π π] during the operation of IMD. The operation of the induction motor drive is implemented and tested by MATLAB/SIMULINK software. The simulation results have demonstrated the effectiveness of the HC control method-based FOC technique with periodic rotor flux angle in controlling motor speed. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

The Firm’s Performance in Relation to Capital Structure and Foreign Ownership: Evidence from Vietnam

The paper examines the impact of capital structure in the context of foreign ownership on firm performance on non-financial companies in Vietnam between 2008 and 2018. The study employs Pooled OLS, Fixed effect, random effect, and Generalized Least Square to analyze the data. The study finds a non-linear relationship of foreign ownership and firm performance, so that the relationship, which is at first a positive one, becomes negative beyond a certain level of foreign ownership (30-45% ownership depending on the measure of performance). This insight is then combined with a generally inverse relationship between capital structure and performance. Besides, we find that the firm’s size (SIZE) has a positive influence on profitability and financial leverage, while both financial leverage (LEV) and the number of listed years of company (AGE) impact negatively on firm performance. Furthermore, growth of sales (GROWTH) has a positive effect on the debt ratio, and growth rate (GDP) has a negative effect on financial leverage. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

Load Frequency Control for Power System using Generalized Extended State Observer

This study investigates load frequency control based generalized extended state observer (GESO) for interconnected power systems subject to multi-kind of the power plant. First, the mathematical model of the interconnected power system is proposed based on the dynamic model of thermal power plant with reheat turbine and hydropower plant. Second, the GESO is designed to estimate the system states and disturbances. In addition, the problem of unmeasurable system states in the interconnected power network due to lack of sensor has been solved by using the proposed load frequency control based GESO. The numerical experiments are carried out by using MATLAB/ SIMULINK simulation. The simulation results point out that the proposed control approach has the capacity to handle the uncertainties and disturbances in the interconnected power system with better transient performances in comparison with the existing control approach. The relevant dynamic models have already been used for the simulation of the physical constraints of the governor dead band (GDB) and generation rate constraint (GRC) effect in the power plants. It is evident that the robustness of the suggested controller in terms of stability and effectiveness of the system. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

Performance Analysis of a SWIPT Enabled UAV-Assisted Relaying

In the recent era, unmanned aerial vehicle (UAV) plays an important role in numerous application fields related to the wireless communication system. Due to its precise control, efficient deployment, and affordable cost, UAV-assisted communication attracts significant attention to all the sectors including the defense sector, agriculture sector, and security purpose, and so on. Though UAVassisted relaying has enormous advantages but there are potential challenges while UAV deploys as a relay. For example, deploying UAV in the wireless communication field, its battery life is the main concern due to its limited battery size and storage capacity. To get significant benefits from UAV while deployed in the cooperative communication network, the battery status of the UAV is an unavoidable issue. To minimize the aforementioned problem, energy harvesting (EH) techniques can be an efficient solution. The UAV can harvest energy from the transmitted power by the source and with the help of this harvested energy UAV can retransmit the signal to the destination. However, there are several parameters that also significantly influence the UAV-based cooperative system performance such as UAV’s position, time allocation factor and power allocation factor, and UAV’s height. Considering the importance of the aforementioned parameters, in this paper, we have considered simultaneous wireless information and power transfer (SWIPT) enabled UAV-assisted relaying network and evaluate the system outage performance with different parameters aspects. We have provided some insight about the parameters such as the UAV’s position, the power allocation factor and the time allocation factor and the UAV’s height by providing simulation results such as the outage probability versus transmit power in the different urban scenario, the outage probability versus time allocation factor and power allocation factor and the outage probability versus UAV’s height. These simulation results clearly show the significance of the abovementioned parameters in wireless-powered UAVassisted cooperative communication. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

Research on Redesign and Manufacturing of an Automatic Roll Cutting Machine

Textile-and-garment industry is one of the largest economic sectors in Vietnam, with 4000 enterprises and a turnover of 20 billion USD/year. Therefore, designing and manufacturing are essential tasks for roll fabric cutting machines to serve the textile and garment industry. First of all, theoretical calculations are formulated for an automatic roll cutting machine. Then, simulations are conducted by a combination of MITcalc and Catia software. A prototype of a fabric cutting machine is manufactured and experiments are implemented. The experimental results show that the machine stably works and overcomes the disadvantages of the popular cutting machines with the core-free roll on the market. The results also found that the size tolerance is achieved about ± 0.5 mm, and this ensures good working quality. The designed machine has a significant contribution to the textile and garment area in decreasing the cost of the cutting process. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

Assessment of Longstanding Effects of Fly Ash and Silica Fume on the Compressive Strength of Concrete Using Extreme Learning Machine and Artificial Neural Network

Compressive Strength (CS) is an important mechanical feature of concrete taken as an essential factor in construction. The current study has investigated the effect of fly ash and silica fume replacement content on the strength of concrete through Artificial Neural Networks (ANNs) and Extreme Learning Machine (ELM). In this study, different ratios of fly ash with (out) extra quantity of silica fume have been tested. Water cement (w/c) ratio varies during the test. Eight input parameters including Total Cementitious Material (TCM), Silica Fume (SF) replacement ratio, coarse aggregate (ca), fly ash (FA) replacement ratio, Sewage Sludge Ash (SSA) as a combination of cement and fine aggregate replacement, water-cement ratio, High Ratio Water Reducing Agent (HRWRA) and Age of Samples (AS) and one output parameter as the CS of concrete have been investigated through ANN and ELM. Up to now, numerous experimental studies have been used to analyze the compressive strength of concrete while retrofitted with fly ash or silica fume, however, the novelty of this study is in its use of AI models (ELM, ANN). The models have been developed and their outcomes were compared through six statistical indicators (MAE, RMSE, RRMSE, WI, RMAE and R2). Subsequently, both methods were shown as reliable tools for assessing the influence of cementitious material on compressive strength of concrete, however, ANN remarkably was better than ELM. As a result, FA showed less contribution to the strength of concrete at short times, but much at later ages. As a result, the enhanced influence of low amount of SF on CS was not significant. Adding fly ash has reduced the compressive strength in short term, but increased the compressive strength in long term. Adding silica fume raises the strength in short term, but decreases the strength in longterm. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.