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This study aims to present a low-cost, non-destructive microwave sensor implementation to monitor the real-time moisture content of rubber wood in industrial dehydration processes. The proposed sensor is based on the free-space measurement technique with magnitudes S11 and S21 only. The novelties of this study consist of the natural frequency determination of rubber wood and the design of a sensor system using devices available on the market with reasonable cost performance. The natural frequency was determined using a simulation and was equal to 1.25 GHz. It specified the sensor system design and device selection. The designed system was initially verified by measuring the moisture content of rubber wood in the laboratory. The measured S11 and S21 voltages correlating with moisture content percentages were obtained and programmed. The system was then installed to monitor the moisture content of rubber wood in the dehydration process. The measured results deviated from those obtained from a standard method in the range of 7.67–15.38%. The error compensation was analyzed to improve the measured results that provided the deviated moisture content in the range of 3.58–5.21%. It can be inferred that the proposed sensor system has the capability to be implemented in industrial dehydration processes.

This article presents the design of a low-cost Wireless Body Sensor Network (WBSN) for monitoring vital signs including a low-cost smart wristwatch that contains an ESP-32 microcontroller and three sensors: heart rate (HR), blood pressure (BP) and body temperature (BT), and an Internet of Things (IoT) platform. The vital signs data are processed and displayed on an OLED screen of the patient’s wristwatch and sent the data over a wireless connection (Wi-Fi) and a Cloud Thing Board system, to store and manage the data in a data center. The data can be analyzed and notified to medical staff when abnormal signals are received from the sensors based on a set parameters from specialists. The proposed low-cost system can be used in a wide range of applications including field hospitals for asymptotic or mild-condition COVID-19 patients as the system can be used to screen those patients out of symptomatic patients who require more costly facilities in a hospital with considerably low expense and installation time, also suitable for bedridden patients, palliative care patients, etc. Testing experiments of a 60-person sample size showed an acceptable accuracy level compared with standard devices when testing with 60 patient-samples with the mean errors heart rate of 1.22%, systolic blood pressure of 1.39%, diastolic blood pressure of 1.01%, and body temperature of 0.13%. According to testing results with 10 smart devices connected with the platform, the time delay caused by the distance between smart devices and the router is 10 s each round with the longest outdoor distance of 200 m. As there is a short-time delay, it does not affect the working ability of the smart system. It is still making the proposed system be able to show patient’s status and function in emergency cases.

To avoid problems related to a school bus service such as kidnapping, children being left in a bus for hours leading to fatality, etc., it is important to have a reliable transportation service to ensure students’ safety along journeys. This research presents a high accuracy child monitoring system for locating students if they are inside or outside a school bus using the Internet of Things (IoT) via Bluetooth Low Energy (BLE) which is suitable for a signal strength indication (RSSI) algorithm. The in/out-bus child tracking system alerts a driver to determine if there is a child left on the bus or not. Distance between devices is analyzed for decision making to affiliate the zone of the current children’s position. A simplified and high accuracy machine learning of least mean square (LMS) algorithm is used in this research with model-based RSSI localization techniques. The distance is calculated with the grid size of 0.5 m × 0.5 m similar in size to an actual seat of a school bus using two zones (inside or outside a school bus). The averaged signal strength is proposed for this research, rather than using the raw value of the signal strength in typical works, providing a robust position-tracking system with high accuracy while maintaining the simplicity of the classical trilateration method leading to precise classification of each student from each zone. The test was performed to validate the effectiveness of the proposed tracking strategy which precisely shows the positions of each student. The proposed method, therefore, can be applied for future autopilot school buses where students’ home locations can be securely stored in the system used for references to transport each student to their homes without a driver.

This study presents a simulation-driven optimization of thermochemical energy storage using SrCl2-based systems for integration with solar energy technologies. Thermochemical sorption systems offer promising potential for enhancing solar energy-storage efficiency by capturing both thermal and electrical energy. However, optimizing sorption processes remains crucial for maximizing energy storage capacity. This work utilized advanced simulation tools to analyze the heat and mass transfer dynamics within SrCl2-EG composites and evaluate system performance under varying compression ratios (CR), reactant temperatures, and heat transfer fluid (HTF) flow rates. The results demonstrate that adjusting CR enhances the overall system efficiency. CR = 4 yields the highest desorption rate of 93.8%, while reducing the required HTF mass flow by nearly tenfold compared to lower CR values. Higher CR contributes to a reduction in sensible heat loss, allowing a greater percentage of thermal energy to be captured. Simulations also show that optimized SrCl2-based systems can integrate effectively with solar energy conversion technologies, making them highly suitable for both energy storage and cooling applications. This research underscores the role of thermochemical energy storage systems in providing more sustainable and efficient solar energy solutions. By reducing energy losses and improving the reliability of the energy storage process, SrCl2-based systems offer significant advantages for renewable energy integration.

This paper presents a high-frequency pulse-density-modulated (PDM) soft-switching series load resonant inverter for use in induction heating (IH) fixed roller applications, which is used in copy and printing machines. The proposed simple high-frequency resonant inverter uses an asymmetrical pulse pattern PDM control scheme to achieve complete zero-current soft-switching commutations over a wide output range of input power regulation. Additionally, when the printer toner requires operation in very light load conditions, this causes difficulty in achieving zero-voltage or zero-current soft-switching operations in the IH high-frequency resonant inverters with pulse frequency modulation or pulse width modulation control schemes. The proposed resonant inverter demonstrates the capability to accomplish highly efficient power conversions. In this work, a fixed roller for printing machines is developed for doing experiments to verify the efficiency of the proposed circuit topology and its PDM control schemes. The inverter’s steady-state and transient operating principles are analyzed based on the proposed control strategy at a high-frequency PDM. Operating conditions such as power loss analysis, power conversion efficiency and temperature rise characteristics of the proposed inverter are presented and analyzed through experimental results. Finally, from a practical viewpoint, a comparative study of a conventional halogen lamp heater and the proposed IH fixed roller is deliberated.

This study presents a simulation-driven optimization of thermochemical energy storage using SrCl[sub.2]-based systems for integration with solar energy technologies. Thermochemical sorption systems offer promising potential for enhancing solar energy-storage efficiency by capturing both thermal and electrical energy. However, optimizing sorption processes remains crucial for maximizing energy storage capacity. This work utilized advanced simulation tools to analyze the heat and mass transfer dynamics within SrCl[sub.2]-EG composites and evaluate system performance under varying compression ratios (CR), reactant temperatures, and heat transfer fluid (HTF) flow rates. The results demonstrate that adjusting CR enhances the overall system efficiency. CR = 4 yields the highest desorption rate of 93.8%, while reducing the required HTF mass flow by nearly tenfold compared to lower CR values. Higher CR contributes to a reduction in sensible heat loss, allowing a greater percentage of thermal energy to be captured. Simulations also show that optimized SrCl[sub.2]-based systems can integrate effectively with solar energy conversion technologies, making them highly suitable for both energy storage and cooling applications. This research underscores the role of thermochemical energy storage systems in providing more sustainable and efficient solar energy solutions. By reducing energy losses and improving the reliability of the energy storage process, SrCl[sub.2]-based systems offer significant advantages for renewable energy integration.

(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) A temperature-compensated high-frequency CMOS integrated relaxation oscillator with low frequency variations is presented. A current-controlled oscillator topology is employed with a resistive source-degenerated transconductor and a current comparator to achieve high oscillation frequency and low power dissipation. The proposed oscillator was designed with process parameters from a standard 0.35-...m CMOS technology and a 2.5-V single power supply voltage. At a nominal oscillation frequency of 21 MHz, the total power dissipation of the circuit was 201 ...W. Post-layout simulation results showed that the frequency variations were less than ... over a temperature range of ... to ...

(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).A temperature-compensated high-frequency CMOS integrated relaxation oscillator with low frequency variations is presented. A current-controlled oscillator topology is employed with a resistive source-degenerated transconductor and a current comparator to achieve high oscillation frequency and low power dissipation. The proposed oscillator was designed with process parameters from a standard 0.35-...m CMOS technology and a 2.5-V single power supply voltage. At a nominal oscillation frequency of 21 MHz, the total power dissipation of the circuit was 201 ...W. Post-layout simulation results showed that the frequency variations were less than ... over a temperature range of ... to ...

A temperature-compensated high-frequency CMOS integrated relaxation oscillator with low frequency variations is presented. A current-controlled oscillator topology is employed with a resistive source-degenerated transconductor and a current comparator to achieve high oscillation frequency and low power dissipation. The proposed oscillator was designed with process parameters from a standard 0.35- μ m CMOS technology and a 2.5-V single power supply voltage. At a nominal oscillation frequency of 21 MHz, the total power dissipation of the circuit was 201 μ W. Post-layout simulation results showed that the frequency variations were less than 34.16 ppm / ∘ C over a temperature range of - 40 to + 120 ∘ C .