Patrick Uche Okafor

Bio: Patrick Uche Okafor is an academic researcher from Enugu State University of Science and Technology. The author has contributed to research in topics: Overshoot (signal) & Settling time. The author has co-authored 4 publications.

Investigating the Effects of Temperature, Paste Height, and Time on Solder Paste to Its Printing Performance

Abstract: Due to pressure to meet consumer requirements, miniaturization, reliability, and increased functionality have become more important. To achieve good assembly of electronic devices, there must be smooth deposition of tiny and consistent paste deposits on the board which must be up to an acceptable height and volume based on desirable process parameters in the output. The printing performance of the solder paste is dependent on conditions such as paste deformation behavior, good paste roll, complete aperture filling, and paste release onto the substrate pads. Eighteen tests were performed using two types of lead-free solder paste. Three temperatures were investigated under three different time intervals. Results analysis showed that variability of the paste distribution was lowest and more uniform for paste stored at 25˚C for 48 hours. From the analysis, it is obvious that temperature has tremendous effects on the printing performance of solder paste. This study recommends 25˚C as a good temperature for solder paste printing.

Development of Solar-Powered Microcontroller-Relay-Based Control System Omnidirectional Wheelchair

Abstract: A solar-powered omnidirectional wheelchair is implemented for physically challenged persons. The framework was mounted on the wheels that were connected with two direct current (DC) motors. The ratings of the battery and solar module were determined using system voltage (12V). A 7,805-voltage regulator was used to supply 5VDC to the AT89352 microcontroller. The microcontroller was programmed to provide a reference signal to the motor. The motor provides the needed torque to drive the wheels through interconnected relays. The relays are energized by the microcontroller and omnidirectional movement achieved through relays connected with microprocessor and micro switches, eliminating the need for joysticks and complex control mechanisms. System performance test result showed that the auxiliary solar power supply of the wheelchair increased the travel range by approximately 86% compared with that of a wheelchair powered by battery alone.

Reducing overshoot in process control for efficient recovery of natural gas liquid (ngl) using model predictive control scheme (mpc)

Abstract: This presents a methodological approach at reducing overshoot in process control for efficient recovery of Natural Gas Liquid (NGL), using the MPC scheme. Reducing process variability to achieve energy-efficient recovery of NGL requires a robust control system. Process variables such as overshoot, rise time, settling time, steady-state error, etc., are controlled to improve system stability, speed of response and prevent mechanical oscillations in control systems. Here, the control problem was formulated in state space, in which a quadratic cost function was used. Kalman filter was used for state estimation with all information necessary to predict future plant behavior. The quadratic cost function was achieved using a genetic algorithm to obtain the optimal control signal. The control system was modeled and implemented in Simulink. A simulation was carried out using the proposed scheme and Proportional Integral Derivative (PID) controller to determine improvement. Results showed that the adaptive MPC scheme outperformed the PID controller at set point following and also, the MPC controller achieved an average of 46.31% overshoot than the PID controller in the reduction of variability in inlet gas flow to the turbo expander

The Adverse Effect of Electromagnetic Radiation From Cellular Base Stations in Nigeria

Abstract: On a global scale, the telecommunication industry is experiencing tremendous growth in mobile phones. Mobile phones communicate with base stations that are erected by the telecommunication industry. The base station produces radio frequency and exposes the people near the base stations to radiation. The effect of electromagnetic radiation from four base stations located at the residential area was studied by measuring their electric field strength and calculating their magnetic field strength and power density at different distances covering a frequency range of 900MHz to 2100MHz. The obtained values showed that the four cellular base stations are operating above the standard values of the International Commission on Non-Ionizing Radiation Protection Electromagnetic Field Radiation. The specific absorption rate was measured to determine the amount of radio frequency electromagnetic radiation absorbed by the human body. The result which is in the range of 3.22-3.70 W/kg is higher than the acceptable 2 W/kg for localized specific absorption rate.