OPUS Collection:

Performance analysis of a Brayton Barocaloric refrigeration cycle using (C9H19NH3)2CuBr4 as refrigerant

Title: Performance analysis of a Brayton Barocaloric refrigeration cycle using (C9H19NH3)2CuBr4 as refrigerant Authors: Balthazar, P; Islam, MS; Bennett, NS Abstract: Abstract Barocaloric materials promise eco-friendly alternatives to vapour compression in refrigeration, with (C 9 H 19 NH 3 ) 2 CuBr 4 being a focus of this study. It is a highly promising barocaloric refrigerant due to the 0.4 K hysteresis temperature and operational pressure as low as 500 Bar. A reversible and irreversible Brayton Barocaloric refrigeration cycle analysis is established. For the irreversible cycle, the irreversibility during the compression and expansion process is considered in the two adiabatic processes. Performance characteristics are investigated across various indoor and outdoor temperature ranges, material operational temperature points, and operating pressures to determine the Coefficient of Performance (COP) and Dimensionless Refrigeration Capacity (DRC). The guidance for optimising the irreversible Brayton Barocaloric refrigeration cycle analysis is provided by disclosing the impact of the irreversibility of work process efficiency, timing ratio, and heat reservoir temperatures. Moreover, several specific cases are examined in detail. The results demonstrate that maximising the phase transition region of (C 9 H 19 NH 3 ) 2 CuBr 4 results in a COP of 10.8 achieved at a temperature span of 3.5 K while maintaining a 0.9-time ratio and conservative irreversibility efficiency of 0.8. This material is capable of cooling by 5.0 K with a reasonable COP of 2.5 at the 0.75-time ratio for a heat source temperature of 309 K and heat sink temperature of 314 K. Finally, this study demonstrates the potential for constructing a simple Barocaloric refrigeration system to validate the concept, with opportunities for further improvement through modifications.

FPGA implementation of a GHKSS filter for real-time noise reduction in nonlinear time series data

2025-04-01T00:00:00Z

Title: FPGA implementation of a GHKSS filter for real-time noise reduction in nonlinear time series data Authors: Konczyk, M; Oberst, S Abstract: The GHKSS nonlinear projective filtering method as a representative of nonlinear time series analysis, has been used as a “posterior filtering” noise reduction technique in a range of applications. Compared to Fourier and model-based techniques it has the advantage of reducing the noise with broadband spectra, without knowledge of the system model. The contamination of time series data with measurement noise may result in an apparent loss of intrinsic dynamical information of the nonlinear systems. A real-time implementation and working principle of the GHKSS algorithm is widely ignored due to its complexity and high computational cost. Here, we present a real-time implementation of this algorithm using a Field Programmable Gate Array (FPGA) and High-level synthesis (HLS) tools. The computational burden is reduced by running the false nearest neighbour (FNN) search and delay estimation part of the GHKSS, on a separate DSP slice using HLS tools. The effect of noise reduction on dynamic preservation using GHKSS was illustrated by estimating the correlation dimension and the maximal Lyapunov exponent of the 3-D Chay model in the chaotic regime. This research is important since the real-time implementation of the GHKSS algorithm will widen its application in nonlinear time series analysis.

Antioxidants, Radical Scavengers, and Their Impact on Oxidative Stress

2025-01-21T00:00:00Z

Title: Antioxidants, Radical Scavengers, and Their Impact on Oxidative Stress Authors: Ohiagu, FO; Chikezie, PC; Maduka, TO; Chikezie, CM; Nwaiwu, O; Paudel, KR Abstract: Antioxidants impede free radical chain reactions and thereby retard and prevent oxidative cellular damage. The present review provides an overview of the basic mechanisms by which antioxidants scavenge free radicals and describes the basic methods for measurement of antioxidant activities against free radicals as well as the underlying chemistry and pathologies linked with oxidative stress. This review was sourced online from scientific search engines using appropriate keywords. For appropriate measurement of antioxidant capacity, with respect to reaction mechanisms involved in the free radical reduction process, exclusive application of HAT, SET methods, and/or a combination of both HAT/SET methods should be considered. The human body is equipped with an antioxidant defence system to mitigate or prevent free radical-induced cellular damage through free radical scavenging mechanisms such as inhibition of enzyme activity involved in free radical generation, activation of intracellular enzymatic antioxidant activity, metal ion chelation, as well as inhibition of protein modification, DNA damage, and lipid peroxidation. Impaired antioxidant activity is associated with chronic diseases such as cardiovascular diseases, diabetes mellitus, inflammatory disease, cancer, cataracts, Alzheimer’s disease, autism, and ageing. Overexpression of enzymatic antioxidants, as demonstrated in mutant mice models, could serve as a novel alleviative measure against the development of pathological conditions associated with oxidative stress.

Effect of Filtration and Self-Cleaning Filter In Air Conditioning

2024-01-01T00:00:00Z

Title: Effect of Filtration and Self-Cleaning Filter In Air Conditioning Authors: Miraz, R; Mushfiq, D; Huynh, P