The reverse supply chain (RSC) recently attracted many Vietnamese authorities, enterprises and academia owing to the rise of concern on the environment and regulations of waste process. Along with rapid development, Vietnamese manufacturing network has become tightly strained when the end-of-life (EOL) items are not taken back by their manufacturers but end up being processed disorderly in different local businesses. A distressing example is the waste of imported solar panels in Vietnam. Since the number of solar panels has grown steadily in Vietnam recently, we speculate that the network flows of EOL solar panel of Vietnam will be very large and complex in a few years. In order to help Vietnamese government establish efficiently RSC, our paper will apply the mixed-integer linear programming (MILP) and demonstrate an optimized solution for the RSC of EOL solar panel in Ho Chi Minh City. Indeed, via our collected data from current financial market of Ho Chi Minh city, our MILP shows that the optimal cost-reduction is 11219 USD, even with limited constraints of only two landfills and very few collection facilities in Ho Chi Minh city at the moment. This result of our proposed RSC demonstrates that a significant profit is definitely possible when the number of collection facilities in Ho Chi Minh city increase in the future. Also, our MILP approach is flexible for decision-makers to achieve a satisfactory solution.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.

Flooding is one of the most common natural disasters in Vietnam. Although a hydrological monitoring system has been developed in Vietnam, the adoption of a Flood Warning and Monitoring System (FWMS) is still limited. A practical issue is that the river water levels is rarely flat, but undulating with flood water ripples, which makes the measurement inaccurate. In this paper, we will design a recursive Kalman estimation for fluctuating flood water level in the Node-Red IoT network. Indeed, the low complexity of the popular Kalman filter algorithm is very suitable for a low-cost IoT system like Node-Red. In our experiments, the accuracy of our Kalman algorithm is far superior to the standard Moving Average (MA) algorithm. To our knowledge, this is the first time that the Kalman filter has been used in a practical Node-Red IoT experiment. We will show that our novel Moving-update Kalman algorithm, which combines MA and Kalman methods, can track data recursively without prior knowledge of noise’s variance. Our novel algorithm is of linear complexity and, hence, fast enough for low cost IoT and FWMS systems in developing countries like Vietnam. We also included the industrial Message Queuing Telemetry Transport (MQTT) protocol in IoT network in our Node-Red system, which means our designed Node-Red proposal is capable of transferring data to any FWMS network via internet. 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.

Internet of things (IoT) is increasingly useful in connecting network of devices on the internet. A popular need of IoT in the industry is to measure the level of the liquid in a faraway tank of interest. The traditional measurement method uses float, pressure or ultrasonic sensor and provides reliable results. Nonetheless, the disadvantages of traditional methods are that their range of measurement is rather short and their maintenance on the field is also difficult. To solve these problems, we propose a novel method that combines the image processing algorithm with Node-Red IoT systems. The original idea of this paper is to use the image of the ruler on the tank for measuring the physical height of liquid level in standard units. Our experimental results on real-time collected images via IoT live-streaming show that our proposed method is very fast and robust with different size and shape of different rulers. Our method is also accurate enough to facilitate the application of liquid level measurement in practice.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 regular increase in COVID-19 cases and deaths has resulted in a worldwide lockdown, quarantine and some restrictions. Due to the lack of a COVID-19 vaccine, it is critical for developing and least developed countries like Vietnam to investigate the efficacy of non-pharmaceutical treatments like social distance or national lockdown in preventing COVID-19 transmission. To address this need, the goal of this study was to develop a clear and reliable model for assessing the impact of social distancing on the spread of coronavirus in Vietnam. For the case study, the Logistic Growth Curve (LGC) model, also known as the Sigmoid model, was chosen to fit COVID-19 infection data from January 23, 2020 to April 30, 2020 in Vietnam. To determine the optimal set of LGC model parameters, we used the gradient descent technique. We were pleasantly surprised to discover that the LGC model accurately predicted COVID-19 community transmission cases over this time period, with very high correlation coefficient value r = 0.993. The results of this study imply that using social distancing technique to flatten the curve of coronavirus disease infections will help minimize the surge in active COVID-19 cases and the spread of COVID-19 infections. 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.