A Novel Hexagonal-Shaped Multilevel Inverter with Reduced Switches for Grid-Integrated Photovoltaic System

To date, the grid-connected solar photovoltaic (PV) system has drawn consideration from researchers and academicians due to the speedy improvement and the declining price of solar panels. The proficiency and dependability of a grid integrated PV system rest mainly on the power conversion unit and the proper controlling mechanism. This paper introduces a novel asymmetric hexagonal-shaped fifteen-level inverter designed to feed a grid-integrated solar PV system. First, it aims to reduce the number of components and thereby decrease the installation space and cost of the multilevel inverter. Moreover, it has a low total blocking voltage (TBV) and total device rating (TDR) and uses few switching devices for generating per level of output voltage. The proposed topology utilizes only eight switching devices for generating fifteen levels at the output, which is lower than conventional multilevel inverter topologies. Here, a low-frequency modulation scheme using the half-height (HH) method generates switching pulses to minimize the complexity. The proposed multilevel inverter topology is also validated through the simulations in the MATLAB SIMULINK environment. The proposed inverter need for filters is illustrated according to different grid codes for integrating PV systems to the grid.

Usage of Biomass-based Carbon Materials as Lubricant Additive: Effects on Rheological and Tribological Properties

Lubricating oils are thick and sticky fluids used for greasing moving parts of machines and engines. This paper expresses key advances in surface engineering and the use of biomass materials as lubricant additives. In order to enhance the lubrication characteristics of base oil, the biochar lubricant additives were successfully prepared. The tribological behaviors of biochar (biomass and hybrid) lubricant additives in two types of base oils (SN500 and SN900) were evaluated. In the current study, biomass-based carbon materials (biochar and hybrid) from a thermochemical conversion unit were employed as a lubricant additive. The rheological and tribological behavior of the base oil modified with biochar additives were experimentally determined. Surface analyses via SEM confirmed the surface enhancement of the worn exterior plane via the effect produced by the biochar additives. It was also observed that the biomass biochar using SN900 improved the kinematic viscosities of the base oil more than the hybrid biochar. This may be attributed to the chars' fundamental composition, which makes the fluid’s internal resistance flow under gravitational force. With SN500, the viscosity index improves with the biochar from 106 to108 but is reduced for SN900 from 102 to 97.09.

Design of Efficient Floating-Point Convolution Module for Embedded System

The convolutional neural network (CNN) has made great success in many fields, and is gradually being applied in edge-computing systems. Taking the limited budget of the resources in the systems into consideration, the implementation of CNNs on embedded devices is preferred. However, accompanying the increasingly complex CNNs is the huge cost of memory, which constrains its implementation on embedded devices. In this paper, we propose an efficient, pipelined convolution module based on a Brain Floating-Point (BF16) to solve this problem, which is composed of a quantization unit, a serial-to-matrix conversion unit, and a convolution operation unit. The mean error of the convolution module based on BF16 is only 0.1538%, which hardly affects the CNN inference. Additionally, when synthesized at 400 MHz, the area of the BF16 convolution module is 21.23% and 18.54% smaller than that of the INT16 and FP16 convolution modules, respectively. Furthermore, our module using the TSMC 90 nm library can run at 1 GHz by optimizing the critical path. Finally, our module was implemented on the Xilinx PYNQ-Z2 board to evaluate the performance. The experimental results show that at the frequency of 100 MHz, our module is, separately, 783.94 times and 579.35 times faster than the Cortex-M4 with FPU and Hummingbird E203, while maintaining an extremely low error rate.

Identification and Ranking of Noise Control Solutions by Using Fuzzy Delphi approach, Fuzzy Analytic Hierarchy Analysis (FAHP) and Fuzzy Vikor in an Oil Refinery

Background: The aimed of this study was to identify and ranking noise control solutions by using fuzzy Delphi approach and FAHP-fuzzy vikor method in an oil refinery. Methods: This descriptive-analytical study was conducted in the catalytic conversion unit in an oil refinery. First, noise measurement was performed based on the standard to identify the sources of noise generating factors. Second, the criteria and initial solutions were identified by reviewing the texts and conducting interviews with experts and the most significant criteria and solutions for noise control were selected using the fuzzy Delphi method. Then, the criteria were weighed using the fuzzy analytic hierarchy method. Finally, the control solutions were prioritized using fuzzy Vikor method. Results: The results of FAHP method indicated that cost with final weight (0.2796) had the highest weight and non-interference in the process with final weight (0.1107) had the lowest weight among the identified criteria. The ranking of noise control solutions with fuzzy Vickor method indicated that the construction of an acoustic room for workers exposed to weights (Q = 0) as the most appropriate solution for noise control and the method of modifying or changing the work process with the final weight (Q = 1) is the last noise control solution among the solutions identified in the studied refinery. Conclusion: The use of multi-criteria decision-making methods in selecting the appropriate solution for noise control can overcome the uncertainties in making an appropriate decision for selecting the best solution for noise control. In this study, a decision model was introduced for selecting the most appropriate noise control solution based on different criteria and this model can be used in other industries which should select a noise control solution.