Maximum Total Efficiency Research Articles

Multi-objective optimization for microbial electrolysis cell-assisted anaerobic digestion of swine manure

As a new technology, microbial electrolysis cell-assisted anaerobic digestion (MEC-AD) has been applied to the utilization of swine manure. Methane production and total energy efficiency are both important indicators in MEC-AD; thus, it is necessary to simultaneously optimize methane production and total energy efficiency. In this study, the Box–Behnken design (BBD) was used as the experimental design, the response surface methodology (RSM) and back propagation neural network (BP-NN) methods were used to construct multi-objective models, and the non-dominated sorting genetic algorithm II (NSGA II) was used for multi-objective optimization. The BP-NN model was superior to the RSM model in terms of goodness of fit. Additionally, the relative error between the predicted and experimental values of the Pareto front was determined to be <3%. The maximum methane production and total energy efficiency were 333.97 mL/g total solid and 61.38%, respectively. Therefore, multi-objective optimization of MEC-AD systems may be accomplished using BBD-(BP-NN)-NSGA II.

Electrical and thermal performance analysis of hybrid photovoltaic/thermal water collector using meta-heuristic optimization

The photovoltaic/thermal (PV/T) flat-panel technology has numerous advantages over PV modules and separately mounted solar thermal collectors regarding overall effectiveness and space-saving. Hybrid PV/T solar collectors’ thermal and electrical performance is influenced by design parameters like mass flow rate, tube diameter, tube spacing, packing factor, and absorber conductivity. This paper focused on using several meta-heuristic optimization techniques, incorporating the following: multiverse algorithm, dragonfly algorithm, sine–cosine algorithm, moth-flame algorithm, whale algorithm, particle swarm algorithm, ant-lion algorithm, grey wolf algorithm, and particle swarm optimization algorithm in PV/T collector optimal design according to maximum total efficiency obtained. The outcomes of the various algorithms revealed that the maximum electrical efficiency of the PV/T collector ranged from 13.85 to 14.28%, while the maximum thermal efficiencies ranged from 41.41 to 52.08% under standard test conditions (1000 W/m2 and 25 °C). The optimized values for the design parameters of the PV/T collector were as follows: the absorber conductivity was determined to be 356.6 W/m K, the packing factor was optimized to 0.7, the mass flow rate was set at 0.019 kg/s, the tube width was determined to be 0.035 m, and the tube spacing was optimized to 0.0524 m. The results indicated that the grey wolf optimizer (GWO) algorithm proved to be highly effective in optimizing the design parameters of PV/T collectors. Furthermore, the study examined the relationship between the temperature of PV modules and PV/T collectors by considering variations in mass flow rate, packing factor, and tube width at different solar radiation levels. The results confirmed that the PV/T collector temperature exhibited improvements compared to the PV module temperature. As a result, this led to higher electrical efficiency and an overall increase in the total efficiency of the PV/T collector.

GENERALIZED THERMAL OPTIMIZATION METHOD FOR THE PLATE-FIN HEAT SINKS OF HIGH LUMEN LIGHT EMITTING DIODE ARRAYS

The performance of high-lumen light-emitting diode (LED) arrays is strongly affected by high temperatures. For better performance, the design of better thermal management techniques is required. In this work, an analytical thermal optimization algorithm for the passive heat sinks of high-lumen LED arrays is presented. With the aid of this algorithm, a broader range of heat sink geometry alternatives can be explored for the identification of the optimal heat sink design. This task is challenging using experimental or numerical techniques. The results demonstrate that the algorithm yields design with a reduction of more than 30% in base temperatures compared to previous heat sink design studies when minimum mass and maximum total efficiency constraints are applied. For devices with high powers, small chip spacing, and space limitations in the horizontal axis where base temperatures cannot be further reduced using these constraints, minimum temperature optimization can result in up to a 17% reduction in base temperatures. This reduction in base temperatures significantly improves the junction temperatures and the overall lighting quality of the LEDs.

Energy and economic analysis of building integrated photovoltaic thermal system: Seasonal dynamic modeling assisted with machine learning-aided method and multi-objective genetic optimization

Building integrated photovoltaic thermal (BIPV/T) systems offer a highly effective means of generating clean energy for both electricity and heating purposes in residential buildings. Hence, this article introduces a new BIPV/T system to optimally minimize the energy consumption of a household residential building. The meticulous design of the proposed BIPV/T system is accomplished through MATLAB/Simulink® dynamic modeling. Performance analysis for the BIPV/T system is performed under different seasonal conditions with in-depth techno-economic analyses to estimate the expected enhancement in the thermal, electrical, and economic performance of the system. Moreover, a sensitivity analysis is conducted to explore the impact of various factors on the energetic and economic performances of the proposed BIPV/T system. More so, the two-layer feed-forward back-propagation artificial neural network modeling is developed to accurately predict the hourly solar radiation and ambient temperature for the BIPV/T. Additionally, a multi-objective optimization using the NSGA-II method is also conducted for the minimization of the total BIPV/T plant area and maximization of the total efficiency and net thermal power of the system as well as to estimate the optimized operating conditions for input variables across different seasons within the provided ranges. The sensitivity analysis revealed that higher solar flux levels lead to increased electric output power of the BIPV/T plant, but total efficiency decreases due to higher thermal losses. Moreover, the proposed NSGA-II shows a feasible method to attain a maximum net thermal power and optimal total efficiency of 5320 W and 63% with a minimal total plant area of 32.89 m2 that attained a very low deviation index from the ideal solution. The levelised cost of electricity is obtained as 0.10 $/kWh under the optimal conditions. Thus, these findings offer valuable insights into the potential of BIPV/T systems as a sustainable and efficient energy solution for residential applications.

The investigation of V-shaped arrays with non-uniform diameter cylinders for high performance hydrokinetic energy conversion

Harnessing hydrokinetic energy through vortex-induced vibration (VIV) is of great significance. The energy capture efficiency of VIV cylindrical arrays still has great potentials for making further progress. This paper investigates the energy conversion performance of cylinder cluster arrays with non-uniform diameter positioned at the upstream, midstream, and downstream locations, utilizing the downstream VIV enhancement effect. The cylinder arrays consist of five cylinders with non-uniform diameters of 2, 3, and 4 cm, resulting in a total of eight different V-shaped configuration scenarios. Through numerical simulation, it is found that the optimal flow velocity for maximizing the cylinder vibration amplitude is 0.8 m/s. In the condition of 0.8 m/s flow velocity, this study investigates the impact of cylinder diameter and the array arrangement on lift force, amplitude response, vortex shedding frequency, converted power, and efficiency. If the diameter of a cylinder is smaller than that of its upstream cylinder, cylinder experiences an enhanced amplitude, and the magnitude of this enhancement increases with the difference in diameters between the two cylinders. The blocking effect in the cylinder array occurs at a distance of two times the diameter. It has been observed that the small diameter cylinder demonstrates exceptional performance, achieving the highest converted power of 6.58 W (88% higher than the single cylinder) and the highest conversion efficiency of 68 % (75% higher than the single cylinder) in the convergent V-shaped array. The divergent V-shaped array achieves a maximum total converted power of 17.12 W (14% higher than the average conversion efficiency of single 2 cm, 3 cm, 4 cm cylinders), while the convergent V-shaped array achieves a maximum total conversion efficiency of 44% (24% higher than the average conversion efficiency of single 2 cm, 3 cm, 4 cm cylinders). This study presents an innovative perspective on the VIV enhancement effect in energy conversion, specifically focusing on multi-cylinder arrays with non-uniform diameters.

SRS conversion efficiency assessment of a single cell Raman gas mixture for DIAL ozone lidar.

A single Raman cell configuration useful for DIAL ozone lidar is designed and optimized. The conversion efficiency and flexibility of using a single Raman cell filled with a mixture of high pressure Raman active gases hydrogen (H 2) and methane (C H 4) have been examined and reported. The stimulated Raman scattering (SRS) conversion efficiency of Raman active gases with different total cell pressures and the volume mixing ratio excited with a focused, frequency quadrupled Nd:YAG laser with a maximum pulse energy of 25mJ and a pulse duration of 10ns at 100Hz repetition rate are examined in detail. The gas combination of H 2:C H 4 emits a coaxial beam of two wavelengths, 288.4nm (C H 4) and 299.1nm (H 2), with a maximum total conversion efficiency of about 45%. The optimum volume mixing ratio for generating the required wavelength pair with almost equal energies is found to be 2:1 (H 2:C H 4) at a total cell pressure of 18bar. The contribution of cascade Raman scattering (CRS) and four-wave mixing (FWM) to the higher order Stokes lines is examined. The laser attenuation due to soot formation under various mixing ratios in the cell is also presented.

Thermodynamic evaluation of a novel renewable energy system that simultaneously provides electricity, freshwater, and syngas using a multiobjective optimization approach

AbstractThis research entails the simulation and thermodynamic evaluation of a combined solar‐powered system that is intended to achieve the energy necessary to construct factories in areas where other sources of energy are not available. The system comprises five major circuits: (1) a parabolic trough that collects solar energy and passes it to downstream circuits via an evaporator, (2) an organic Rankine cycle that generates electricity for devices and factories, (3) a proton exchange membrane electrolysis unit that produces hydrogen from pure water, (4) a methanation unit that produces gas by combining hydrogen and carbon dioxide, and (5) a reverse osmosis (RO) unit that purges seawater to produce freshwater. This investigation studies the efficiency of energy and exergy, the destruction rate of exergy, and the economic value of system components as a whole. The system is represented by the technical equation solver, and the results are obtained as a result. This research employs the genetic algorithm and Technique for Order of Preference by Similarity to Ideal Solution method to locate the most effective point. The achieved outcomes include a maximum total system efficiency of 54.935% and a minimum total cost of 2.578 $/GJ. Dated to the optimal point, the power generated is 305.5 kW, the required power of a single‐cell electrolyzer is 293.8 W, the mass flow rate of methane and hydrogen production is 448.92 and 225.64 kg/h, respectively. The water volume generated by RO is 35.25 m3/h, and the total cost of the investment is 85.57 $/h.

Biosorption and desorption of chromium using hybrid microalgae-activated sludge treatment system

This study utilised a mixed culture of Chlorella vulgaris and bacteria from sludge to treat synthetic tannery wastewater (STWW) in modified stirred-tank photobioreactors (MSTPBRs). The MSTPBRs were fabricated locally and operated at irradiance value of 580 µmol/m2s supplied by red light-emitting diodes at 12:12 light–dark cycles and 100 ± 1 rpm continuous stirring. In each case, 50, 100 and 150 mg/L concentrations of STWW were inoculated with mixed culture of microalgae and bacteria in three MSTPBRs, with the control MSTPBR operating at 50 mg/L of STWW. Chromium concentrations were measured using colorimeter whilst Fourier transform infrared spectroscopy (FTIR) indicated possible Cr biosorption. Maximum Cr (VI) and total Cr removal efficiencies of 93 and 94% were achieved, with more than 78% total Cr recovery. Results from FTIR suggested involvement of Chlorella vulgaris in the Cr biosorption. The hybrid microalgae-bacteria system efficiently treated tannery wastewater with considerable Cr removal efficiencies. The potentials of the system in treating tannery wastewater in larger scale may require further investigation.

Demonstration of a small‐scale power generator using supercritical CO2

AbstractThe supercritical CO2 (sCO2) power cycle could improve efficiencies for a wide range of thermal power plants. The sCO2 turbine generator plays an important role in the sCO2 power cycle by directly converting thermal energy into mechanical work and electric power. The operation of the generator encounters challenges, including high temperature, high pressure, high rotational speed, and other engineering problems, such as leakage. Experimental studies of sCO2 turbines are insufficient because of the significant difficulties in turbine manufacturing and system construction. Unlike most experimental investigations that primarily focus on 100 kW‐ or MW‐scale power generation systems, we consider, for the first time, a small‐scale power generator using sCO2. A partial admission axial turbine was designed and manufactured with a rated rotational speed of 40,000 rpm, and a CO2 transcritical power cycle test loop was constructed to validate the performance of our manufactured generator. A resistant gas was proposed in the constructed turbine expander to solve the leakage issue. Both dynamic and steady performances were investigated. The results indicated that a peak electric power of 11.55 kW was achieved at 29,369 rpm. The maximum total efficiency of the turbo‐generator was 58.98%, which was affected by both the turbine rotational speed and pressure ratio, according to the proposed performance map.

Selective granulation of trivalent iron into ferric hydroxide from bi-metal containing wastewater using Fluidized-Bed Homogeneous Crystallization technology

The traditional method that is used to treat the bi-metal-contained wastewater involves simultaneous chemical precipitation for the removal of both metals. However, recent trends in wastewater treatment emphasize the importance of recovery, recycling, and reuse. This study uses Fluidized-Bed Homogeneous Crystallization (FBHC) technology to selectively recover Fe(III) as granulated Fe(OH)3 from electroplating wastewater that contains iron and copper. For the treatment of a pure iron solution ([Fe(III)]0 = 650 mg/L), the optimal conditions include a pH value of 3.8, a reflux ratio (R) of 17.5, an up-flow velocity (U) of 35.9 m/h and a hydraulic retention time (HRT) of 17.9 min to give the maximum total removal efficiency (TR) for iron of more than 99.5%, and a crystallization ratio (CR) for iron of 93.6%. To treat real electroplating wastewater that contains iron and copper ([Fe(III)]0 = 1000 mg/L and [Cu(II)]0 = 500 mg/L), Fe(III) is effectively recovered as granules with a TR of 99% and a CR of 90%, and more than 90% of copper ions remain in the solution. SEM analysis observes that the product is an unseeded core-shell spherical particle. Additionally, XRD, FT-IR, and TGA results confirm that the product is an amorphous ferric hydroxide (Fe(OH)3) compound. A FBHC system has a high potential to separate iron and copper in a solution via a selective granulation process.

Performance evaluation of a moonbase energy system using in-situ resources to enhance working time

The solar energy resources of the Moon are far more prosperous than those of the Earth. Therefore, energy systems driven by solar energy are more suitable for application on the Moon. Ensuring the safe operation of the energy system under solar energy (or other variable-temperature heat sources) has become a focal point issue that constrains the construction of the moonbase. In this paper, based on the closed Brayton cycle-organic Rankine cycle (CBC-ORC) system and considering the dryness of the outlet of the evaporator of ORC, a scheme is proposed to raise the temperature of the heat source by using a heat storage heat exchanger (HSHEX). Thus increase the dryness of the organic working fluid side of the evaporator. With the introduction of HSHEX, ORC can work for up to 13.3 days at a mass flow rate of 0.6 kg/s, nearly one time more than the case without HSHEX. The maximum total system thermal efficiency can reach 28.74 %. By stopping the CBC and adjusting the ORC mass flow rate, the average power generation gets 5.69 kW, doubling the working time during the lunar nighttime. This paper aims to solve the problem of improving the working time of the moonbase energy system and provide theoretical guidance for constructing the future lunar base energy system.

Analysis of optimal expansion dynamics in a reciprocating drive for a micro-CAES production system

This paper presents the unique design and processing conditions of a micro-CAES device that generates, stores and delivers electrical energy with highly efficient total energy conversion. The micro-CAES installation is divided into six parts, where air, the energy carrier, is compressed, stored, heated and expanded in appropriate sections. We focus mainly on the post-preparation section, where the air mass flow is pulse heated and controlled by Pulse Width Modulation (PWM), and the expansion section, where multiple piston drives are used to achieve maximum energy conversion efficiency or the required amount of electricity to be fed into the grid. We discover that the controllability of expansion process performance is improved by exploiting the inertia of the following elements in multiple reciprocating engines: piston, piston rod, connecting rod, crank, and crankshaft, connected with air injection dynamics and pulse heating by Thermal Energy Storage (TES). Furthermore, we investigate the efficiency using our own zero-dimensional mathematical model illustrating the complex dynamics of air processing. The mathematical model was compared with experimental data for the single-drive air expander, showing qualitatively and quantitatively satisfying model reliability. Moreover, we performed a sensitivity analysis to determine the best number of reciprocating drives involved in the expansion section and the best operating conditions. The use of the PWM function of mass flow of air supplied the expander with an index of 0.5 together with pulsating air heating in the expander installation, including three- reciprocating drives, allows a maximum total energy conversion efficiency of 81%. The presented piston drive expander seems to be a promising solution for micro-CAES in residential and industrial applications, especially where additional low-temperature waste heat is available, and an intermittent control strategy is implemented.

Indoor experimental analysis of Serpentine-Based cooling scheme for high concentration photovoltaic thermal systems

High concentration photovoltaic thermal hybrids are expected to play an important role in meeting growing energy demands. When approaching concentrations over 1000 suns, a cooling system is needed to maximise both the thermal and electrical performance of the multi-junction solar cell without producing excessive parasitic losses.This study develops a novel simulation model to provide an in-depth understanding of the functionality of a concentrated photovoltaic thermal hybrid system with serpentine-based cooling systems. An ultra-high concentrator photovoltaic optic irradiance profile (peak effective concentration ratio: ∼1500 suns) is considered within the simulation model, which has been validated through indoor experimentation. The effectiveness of cooling is also evaluated through maximum thermal stresses generated in the multi-junction solar cell. The double serpentine design was deemed the highest performing, primarily because of the single serpentine’s excessive pressure drop. Copper as the heat sink material yielded superior performance because of its higher thermal conductivity. The maximum total exergetic efficiency achieved by the receiver was ∼ 10.9% with this configuration. Compared to some examples in the literature this value may seem low, however, it is more accurate due to the inclusion of a specific irradiance profile. All serpentine-based cooling systems could maintain the recommended operating temperature.

Performance analysis and structure optimization for concentrated photovoltaic-phase change material-thermoelectric system in space conditions

High-efficient thermal management is urgently needed for concentrated photovoltaic-thermoelectric hybrid system due to the high heat flux. In present paper, a three-dimensional model for the hybrid system in outer space conditions was established by coupling phase change temperature control and radiation heat sink technologies to find the propriate thermal management scheme. Firstly, the three shortcomings in the typical hybrid system were proposed and their adverse effects on efficiency were elucidated. Then, a heat transfer pillar for temperature control unit and a newly designed circular fins for heat sink were designed. The effects of structure parameters on power generation performance were investigated, and the interaction between temperature control unit and heat sink were discussed. The results show that the hybrid systems with the newly designed heat transfer pillar and circular fins have higher efficiency. After that, a united structure optimization by artificial neural network-multi-objective genetic algorithm was performed to solve the interaction and to balance the electrical efficiency and power density of hybrid system. The comprehensive power generation performance of hybrid system can be further improved after the optimization. The system with PCM thickness dPCM = 6.33 mm, heat transfer pillar width a = 18.19 mm, fin length L = 49.99 mm and fin radius R = 50 mm, has the maximum average total efficiency (31.83%, 2.98% higher than the typical system); the system with dPCM = 3.02 mm, a = 10.05 mm, L = 47.03 mm and R = 25.86 mm, has the maximum average power density (36.97 W/kg, 15.78% higher than the typical system).

N ASSESSING THE EFFECTIVENESS OF HYBRID SOLAR COLLECTORS SCHEME INIRAQ'S ENVIRONMENT

An evaluation of the performance of the Iraqi environments in terms of electrical, thermal and exergy efficiency is introduced in this study. The research is carried out in May 2022, in the Baghdad metropolis. The extraction process of heat from the photovoltaic units which arises from the coolant liquid mass flow rate deem as an essential point. The experimental studies were implemented by absorbing heat energy behind from the photovoltaic cell's surface in insulated conditions and using a cooled water unit. The results indicated that at a mass inflow rate of 0.2 kg/sec, the maximum average total efficiency of the system was recorded 22%. As a result, it is advised that to reduce the payback interval, it is possible to design efficient solar photovoltaic–thermal systems to promote the whole system's efficiency and lower the payback interval.

Influence of engine heat source conditions on a small-scale CO2 power generation system

Employing a CO2 power generation system to recover waste heat from engines can reduce fuel consumption and CO2 emissions by producing additional electric power. Nevertheless, the fluctuation in engine operating conditions would cause variations in waste heat sources and affect system performances largely. Hence, an experimental performance test at various engine conditions was implemented by the construction of a small-scale (10 kW) CO2 power generation system. Key components, including the turbine expander and printed circuit heat exchanger, were specifically designed and constructed. The steady-state and transient performances of critical components and the integrated system were carried out. Experimental results of the turbine expander at varying engine conditions revealed the potential for long-term and stable operation under dynamic mass flow rate, inlet temperature, and pressure ratio. The maximum total generation power and efficiency reached 11.55 kW and 58.92%. The printed circuit heat exchanger used to exploit engine exhaust gas showed satisfactory performances in balancing the trade-off between heat transfer and pressure drop. The total pressure drop of engine exhaust gas was lower than 4 kPa determined by both exhaust mass flow and temperature, considering all the variable engine conditions. Despite that a performance penalty was observed at the off-design operation of the integrated system because of the decrease in the waste heat input, the maximum net power and thermal efficiency reached 10.57 kW and 6.59%, respectively, at the engine condition of 1100 rpm, 1200 N m, with a relative improvement of 6.3% in engine brake thermal efficiency.

Efficient nitrogen removal of a novel Pseudomonas chengduensis strain BF6 mainly through assimilation in the recirculating aquaculture systems

Biological nitrogen removal has received increasing attention in wastewater treatment. A bacterium with excellent nitrogen removal performance was isolated from biofilters of recirculating aquaculture systems (RAS) and identified as Pseudomonas chengduensis BF6. It was indicated that inorganic nitrogen is transformed into gaseous and biological nitrogen by the metabolic pathways of denitrification, anammox, and assimilation, which is the main nitrogen removal pathway of strain BF6. The strain BF6 could effectively remove nitrogen within 24 h under the conditions of ammonia, nitrate, nitrite, and mixed nitrogen sources with maximum total nitrogen removal efficiencies reaching 97.00 %, 61.40 %, 79.10 %, and 84.98 %, respectively. The strain BF6 exhibited total nitrogen removal efficiency of 91.14 %, altered the microbial diversity and enhanced the relative abundance of Pseudomonas in the RAS biofilter. These findings demonstrate that Pseudomonas sp. BF6 is a highly efficient nitrogen-removing bacterium with great potential for application in aquaculture wastewater remediation.

Electrostatic precipitator with Surface Dielectric Barrier Discharge ionizer

The performance of a two-stage electrostatic precipitator (ESP) with an ionizer with Surface Dielectric Barrier Discharge (SDBD), where the ionizer both generates the free charges and forces the airflow via the electrohydrodynamic (EHD) effect, was experimentally studied. The Particle Image Velocimetry Method (PIV) measurements revealed the airflow patterns and showed that the total flow rate generated by the ionizer (with both flat edge and saw-like high-voltage electrodes) increases with the applied discharge voltage up to a maximum of 73 l/min for 24 kV. These measurements, supported by Computational Fluid Dynamics (CFD) simulations, suggested that changing the airflow pattern with a flow guide would improve the filtration efficiency. This has been experimentally confirmed using an optical particle analyzer, and we recorded a maximum total mass filtration efficiency of 98% for the ionizer with a flat electrode and a flow guide with 3 mm inlet gap. We found that the filtration efficiency increases with the applied voltage up to about 14 kV, then decreases with the voltage due to a reduction in the particle charging rate caused by the high flow velocity of the particles through the discharge region. We also determined that, taking into account both flow rate and filtration efficiency, the ESP works optimally with an applied voltage of 18 kV–20 kV, achieving a filtration efficiency of 77% and simultaneously a flow rate of 63 l/min for the ionizer with the saw-like electrode and respectively 89% and 28 l/min for the ionizer with the flat electrode.

Insights on nitrogen and phosphorus removal mechanism in a single-stage Membrane Aeration Biofilm Reactor (MABR) dominated by denitrifying phosphorus removal coupled with anaerobic/aerobic denitrification

In the study, the denitrifying phosphorus removal process coupled with anaerobic/aerobic denitrification was started in a single-stage Membrane Aeration Biofilm Reactor (MABR). When the influent NO3−-N was 50.2 mg/L and the total phosphorus (TP) was 30.5 mg/L, the maximum Total Inorganic Nitrogen Removal Efficiency (TINRE) can reach 99.79 % and the Total Phosphorus Removal Efficiency (TPRE) can reach 82.62 % without the addition of any flocculant or precipitant. The phosphorus content in the substrate sludge was 4.10 %–6.15 %, which was higher than that in the initial biofilm or activated sludge (1.27 %–1.83 %). Based on 16S rRNA sequencing technology, it was found that Phosphorus-Accumulating Organisms (PAOs, Acinetobacter, relative abundance 0.02 % to 1.92 %) and Denitrifying Phosphorus-Accumulating Organisms (DPAOs, Flavobacterium (0.26 % to 5.39 %), Bdellovibrio (0.12 % to 1.48 %), and Pseudomonas (2.29 % to 1.28 %)) played pivotal roles in phosphorus removal. The enzyme gene reads of Complex I and Complex V processes were much more than that of Complex II- Complex IV, which indicated that Complex I and Complex V can be the main process for oxidative phosphorylation in the MABR. Moreover, four inorganic nitrogen metabolic processes, Dissimilatory Nitrate Reduction to Ammonium (DNRA), Assimilatory Nitrate Reduction Ammonium (ANRA), nitrification, and denitrification were found. Nitrifiers (Nitrosomonas (0.09 % to 0.19 %), Nitrospira (2.48 % to 0.06 %)), denitrifiers (Dokdonella (6.95 % to 2.11 %), Denitratisoma (0.42 % to1.48 %)), and aerobic denitrifiers (Pseudomonas (2.29 % to 1.28 %) and Thauera (4.75 % to 1.78 %)) contributed to nitrogen removal in the MABR. This study provided insights into the removal mechanism of nitrogen and phosphorus in a single-stage MABR.

Dual and wideband 6-port MIMO antenna for WiFi, LTE and carrier aggregation systems applications

This article describes a novel dual-band 6-port MIMO antenna for WiFi, LTE, and carrier aggregation system applications. The proposed antenna consists of a defected annular ring, slots, an array structure, a neutralization block, and a novel isolation structure (GP-3) for enhancement of bandwidth, coupling, isolation, gain, and efficiency. After systematic investigation of the reference antenna (A-0; 0.65λ0×0.48λ0mm2) at the design frequency of 2.4 GHz, an optimized antenna (A-4) with ground plane GP-3 is selected among the antennas (A-1 to A-4). The proposed antenna resonates in dual-band, with a lower band (1.6–2.45 GHz (simulated), 1.57–2.39 GHz (measured)) due to ports P5 and P6, and a higher band (2.3–2.6 GHz (simulated), 2.3–2.58 GHz (measured)) due to ports P1, P2, P3 and P4. A peak realized gain of 2.2 dB and 3.34 dB at resonance frequencies of 1.7 GHz and 2.45 GHz is obtained, respectively. The proposed antenna exhibits a maximum isolation and total efficiency of 45.6 dB and 88%, respectively. Simulated results by means of HFSS version 18 are validated with experimental results of the proposed work.