Discontinuous Mode Research Articles

Application of the market-ready NAVETTA electrodeposition chamber for controlled in vitro exposure with nano-scaled aerosols.

Exposure of lung epithelia to aerosols is omnipresent. Chronic exposure to polluted air is a significant factor in the development of pulmonary diseases, which are among the top global causes of death, including COVID-19, chronic obstructive pulmonary disease, lung cancer, and tuberculosis. As efforts to prevent and treat lung diseases increase, the development of pulmonary drug delivery systems has become a major area of interest. In line with the '3 R' principles (Reduce, Refine, and Replace animal testing), we developed an in vitro aerosol exposure system, termed NAVETTA, which was designed to replicate lung conditions most realistically. This system exposes air-liquid interface-cultured lung epithelial cells to a low, laminar airflow, enabling efficient aerosol deposition within an electric field. The aim of this study was to test instrumental performance on different aerosols, with a focus on precision, reproducibility, and cellular response. Deposition of sodium fluorescein droplets, pristine, and fluorescently labeled silica nanoparticles was homogenous and reproducible across the different instrument positions and over several runs, hence, the coefficient of variance for run-to-run and position-to-position was below 15 % using reference aerosols. To showcase NAVETTA's versatile applicability, pristine silica nanoparticles and surface-functionalized fluorescently labeled silica nanoparticles were used. Various charging scenarios were studied, evidencing that deposition was enabled by and dependent on the applied electric field. Additional aerosol charging enhanced deposition compared to deposition achieved employing only the intrinsic charges of aerosol particles/droplets. In a second feasibility study two dry powder generators were tested for application with the NAVETTA system for testing deposition and cellular effects of nano-scale TiO2 aerosols. Cellular stress response was determined by interleukin-8 secretion, and viability post-exposure to TiO2 was monitored. Cells exhibited a trend to decreased viability and increased interleukin-8 secretion upon TiO2 deposition evidencing feasibility for application, however, more work is needed for optimizing reproducibility when using dry aerosol generators due to their discontinuous operation mode. Physiological conditions of 37°C and 98 % relative humidity within the NAVETTA resulted in 95 % viability over 24 h enabling longer-term exposure experiments. In summary, the market-ready NAVETTA presents a versatile exposure system for future in vitro pulmonary safety and efficacy studies by facilitating reliable and reproducible electrodeposition of various aerosols.

Nonlinear Analysis and Closed-Form Solution for Overhead Line Magnetic Energy Harvester Behavior

Recently, much attention has been given to the development of various energy harvesting technologies to power remote electronic sensors, data loggers, and communicators that can be installed on smart grid systems. Magnetic energy harvesting is, perhaps, the most straightforward way to capture a significant amount of power from a current-carrying overhead line. Since the harvester is expected to have a small size, the high currents of the distribution system easily saturate its magnetic core. As a result, the operation of the magnetic harvester is highly nonlinear and makes precise analytical modeling difficult. The operation of an overhead line magnetic energy harvester (OLMEH) generating significant DC power output into a constant voltage load was investigated in this paper. The analysis method was based on the Froelich equation to analytically model the nonlinearity of the core’s BH characteristic. The main findings of this piecewise nonlinear analysis include a closed-form solution that accounts for both the core and rectifiers’ nonlinearities and provides an accurate prediction of OLMEH transfer window length, output current, and harvested power. Continuous and discontinuous operational modes are identified and the mode transition boundary is obtained quantitatively. The theoretical investigation was concluded by comparison with a computer simulation and also verified by the experimental results of a laboratory prototype harvester. A good agreement was found.

Salinity as an Abiotic Stressor for Eliciting Bioactive Compounds in Marine Microalgae.

This study investigated the impact of culture medium salinity (5-50 PSU) on the growth and maximum photochemical yield of photosystem II (Fv/Fm) and the composition of carotenoids, fatty acids, and bioactive substances in three marine microalgae (Chrysochromulina rotalis, Amphidinium carterae, and Heterosigma akashiwo). The microalgae were photoautotrophically cultured in discontinuous mode in a single stage (S1) and a two-stage culture with salt shock (S2). A growth model was developed to link biomass productivity with salinity for each species. C. rotalis achieved a maximum biomass productivity (Pmax) of 15.85 ± 0.32 mg·L-1·day-1 in S1 and 16.12 ± 0.13 mg·L-1·day-1 in S2. The salt shock in S2 notably enhanced carotenoid production, particularly in C. rotalis and H. akashiwo, where fucoxanthin was the main carotenoid, while peridinin dominated in A. carterae. H. akashiwo also exhibited increased fatty acid productivity in S2. Salinity changes affected the proportions of saturated, monounsaturated, and polyunsaturated fatty acids in all three species. Additionally, hyposaline conditions boosted the production of haemolytic substances in A. carterae and C. rotalis.

High-Frequency Modified Bridgeless AC-DC PFC Rectifier for Ceiling-Fan

High current percentage total harmonics distortion (%THD), low supply power factor (SPF), and high input-power are main concern in an existing brushless direct current motor ceiling-fan (BLDCMCF). This paper presents AC-DC coupled-inductor-based bridgeless switched-inductor Cuk-converter (CIB-BLSICC) for BLDCMCF to address these concerns. CIB-BLSICC improves supply power quality (SPQ) and reduces input-power. Switched-inductor branch using coupled-inductor provides high-step-down-gain (HSDG), which offers an appropriate operating duty for BLSICC. Front-end CIB-BLSICC is developed in discontinuous mode (DCM) with changeable output voltage and a low component count, which reduces converter's overall size. DCM design offers auto power-factor correction (PFC) at a supply-mains. Variable output-voltage makes voltage source inverter (VSI) control easy (offers inverter switching at fundamental-frequency) with low switching-losses and helps speed-control. In addition to improving CF's (ceiling-fan's) overall efficiency, bridgeless design of PFC-converter lowers losses caused by conduction. Using reference speed of fan, CIB-BLSICC calculates its operational duty in order to create fixed-frequency PWM-pulses (200 kHz) while supply-voltage remains constant. This simple-control brings CF's price down by removing need for a sophisticated sensing-circuit, a DC-link sensor, and a voltage-controller. Test results confirm concept and design, which demonstrate a %THD of 1.483%, a crest-factor of 1.48, SPF of 0.9991, and a power-input of 27.93 W.

Partial PAM Inverter with Power Decoupling Operation in Discontinuous Current Mode

Partial PAM Inverter with Power Decoupling Operation in Discontinuous Current Mode

Interleaved Modified SEPIC Converters with Soft Switching and High Power Factor for LED Lighting Appliance

A novel ac/dc LED driver with power factor correction and soft-switching functions is proposed. The circuit topology mainly consists of two modified single-ended primary inductance converters (SEPIC) with interleaved operation. The first half stage of SEPIC operates like a boost converter and the second half stage operates like a buck–boost converter. Each boost converter is designed to operate in discontinuous current mode (DCM) to function as a power factor corrector (PFC). The two buck–boost converters that share a commonly coupled inductor are designed to operate at near boundary conduction mode (BCM). Without using any active clamping circuit, auxiliary switch or snubber circuit, the active switches can achieve zero-voltage switching on, and all diodes achieve zero-current switching off. First, operation modes in steady state are analyzed, and the mathematical equations for design component parameters are derived. Finally, a prototype circuit of 180 W rated power was built and tested. Experimental results show satisfactory performance of the proposed circuit.

Enriched PQ-based bridgeless isolated one-stage sepic PFC converter for power solutions

ABSTRACT This article deals with an enriched power quality (PQ) based bridgeless isolated one-stage (BIOS) Sepic PFC converter as a cost-effective power solution. The presented revamped bridgeless structure on the front-end avoids unnecessary capacitive coupling and assures less current harmonic distortions, better power factor (PF) at the AC mains to confirm the permissible power quality (PQ) metrics as per IEC 61,000-3–2 standards. This PFC circuit is modelled to be operated on discontinuous inductor current mode (DICM) to reveal the innate zero current switching (ZCS) and power factor correction (PFC) capability. The added merits of DICM and high-frequency isolation involve lesser number of sensors, part count, control complications, size and cost associated with the entire power conversion. Further, the hardware setup of 250W/48 V power solution is assembled to testify the performance of the developed circuit. From the experimental outcomes it is notable that this power solution retains the bettered PQ profile within the perceivable limits even under broad range of source voltage and load discrepancies. Finally, the extensive loss modelling of the power circuit is formulated to evaluate the actual efficiency of the entire power conversion.

A non-isolated synchronous buck DC-DC converter, ZVS topology under CCM and DCM conditions

Today, the main challenge of miniaturization and integration of power converters is reducing the volume of parts, eliminating capacitors and inductors.This paper proposes a non-isolated synchronous buck converter (NSBC) under soft switching practice. This converter uses the zero voltage switching (ZVS) topology, which not only provides soft-switching conditions for the converter switches but also prevents the voltage kicking off the two ends of the main switches from being off-state due to self-resonance. To achieve the highest voltage gain in different working cycles, complementary switching approach and use of non-isolated Dc-Dc converter for simultaneous switching of two switches will be used.The non-isolated synchronous buck DC-DC converter with ZVS is to use in some parts of the converter for providing a purpose range of output voltage. In addition, the implementation of the proposed converter control circuit is conducted very simply and needs lower costs. To confirm relations in converter theory, the results of a laboratory sample in the discontinuous and continuous modes are examined. It should be noted that the proposed converter can operate under different levels of voltage, which requires a protection heat policy. The proposed converter implements under the nominal 30-V input and 40 KHz switching frequency, which touches on issues on both sides of discontinuous conduction mode (DCM) and the continuous conduction mode (CCM) conditions and experiment as an example two rates of power 30W and 20W respectively, and also has an acceptable interest rate, which will be evaluated and compared with three different types of similar modes.

Switched capacitor and coupled inductor based high power factor charger for E-2/E-3 wheelers

This paper introduces a modified Zeta converter topology designed specifically for charging low voltage electric vehicles (LVEVs), enhancing performance for electric two (E-2) and electric three (E-3) wheelers. Unlike traditional Zeta converter, which offers buck-boost gain, an AC-DC converter in this study, utilizes a switched capacitor configuration to efficiently step-down voltage in a single phase, bridging the gap between the AC grid and low potential battery assemblies. This design incorporates a coupled inductor structure and operates in discontinuous inductor current mode (DICM), reducing the size of magnetic components and overall dimensions of converter and power factor correction (PFC) rectifier. DICM operation provides intrinsic PFC and minimizes switching losses, ensuring exceptional grid-side performance with unity power factor and minimal input current harmonic distortions, while maintaining an optimal battery charging profile. The meticulously developed hardware prototype, rated at 450 W, features precise component selection and carefully designed modes of operation. Performance analysis reveals a converter peak efficiency of 94.7 %, total harmonics distortion (THD) in input current at 2.7 % under rated conditions, and near unity power factor with zero phase displacement between input voltage and current.

Application of hollow fiber membranes for producing an ultrafiltration permeate from colostrum whey enriched in bioactive compounds

Bovine colostrum whey, despite being a source of bioactive peptides and prebiotic oligosaccharides with dietary and nutraceutical applications, presents significant processing challenges due to its high viscosity, making hollow fiber membranes, with their superior ability to control membrane fouling, well-suited for handling such fluids. The objective of this work was to determine optimal ultrafiltration conditions of a 10 kDa hollow fiber membrane to increase efficiency (i.e., permeate flux), selectively retain whey proteins, and facilitate the permeation of peptides (< 10,000 Da) and oligosaccharides (∼600 Da) from bovine colostrum whey. The impact of feed flow rate (3, 6, 9 L min-1) and transmembrane pressure (1, 2, 3 bar) were evaluated on permeate flux, protein retention, and non-protein nitrogen permeation. Higher permeate fluxes were observed at higher feed flows and moderate transmembrane pressure, demonstrating the ability of turbulence to disrupt the concentration polarization layer at the membrane surface and decrease fouling, as exhibited in the resistance analyses. Higher feed flow significantly increased the cumulative permeate flux during colostrum whey concentration (64.6 ± 0.1 L h-1m-2 at 9 L min-1 vs. 12.5 ± 5.9 L h-1m-2 at 3 L min-1, at continuous diafiltration mode and 2 bar), with continuous diafiltration experiments yielding similar permeate fluxes to the ones achieved in discontinuous mode. Processing scale at 12.7 L (2 bar, 9 L min-1, and continuous diafiltration) enabled 97% protein retention and 95% peptide and oligosaccharide permeation, producing a permeate with 1.3 g L-1 peptide and 0.42 g L-1 oligosaccharide. The results of this study highlight the impact of key ultrafiltration conditions of bovine colostrum whey using a hollow fiber membrane for the effective recovery of peptides and oligosaccharides for subsequent evaluation of their biological properties and commercial applications.

Wireless Power Transfer Efficiency Optimization Tracking Method Based on Full Current Mode Impedance Matching.

Wireless power transfer (WPT) technology is a contactless wireless energy transfer method with wide-ranging applications in fields such as smart homes, the Internet of Things (IoT), and electric vehicles. Achieving optimal efficiency in wireless power transfer systems has been a key research focus. In this paper, we propose a tracking method based on full current mode impedance matching for optimizing wireless power transfer efficiency. This method enables efficiency tracking in WPT systems and seamless switching between continuous conduction mode and discontinuous mode, expanding the detection capabilities of the wireless power transfer system. MATLAB was used to simulate the proposed method and validate its feasibility and effectiveness. Based on the simulation results, the proposed method ensures optimal efficiency tracking in wireless power transfer systems while extending detection capabilities, offering practical value and potential for widespread applications.

Thermally compensated discontinuous modulation strategy influence on DC-link capacitor current of CHB converters

Thermally compensated discontinuous modulation strategy influence on DC-link capacitor current of CHB converters

Minimum Voltage Operation of Cascaded H-Bridge StatComs Using Discontinuous Modulation

Minimum Voltage Operation of Cascaded H-Bridge StatComs Using Discontinuous Modulation

Analysis of small-scale soil CO2 fluxes in an orange orchard under irrigation and soil conservative practices

The quantification of soil carbon dioxide (CO2) flux represents an indicator of the agro-ecosystems sustainability. However, the monitoring of these fluxes is quite challenging due to their high spatially-temporally variability and dependence on environmental variables and soil management practices.In this study, soil CO2 fluxes were measured using a low-cost accumulation chamber, that was realized ad hoc for the surveys, in an orange orchard managed under different soil management (SM, bare versus mulched soils) and water regime (WR, full irrigation versus regulated deficit irrigation) strategies. In particular, the soil CO2 flux measurements were acquired in discontinuous and continuous modes, together with ancillary agrometeorological and soil-related information, and then compared to the agrosystem scale CO2 fluxes measured by the eddy covariance (EC) technique.Overall significant differences were obtained for the soil CO2 discontinuous fluxes as function of the WR (0.16 ± 0.01 and 0.14 ± 0.01 mg m−2 s−1 under full irrigation and regulated deficit irrigation, respectively). For the continuous soil CO2 measurements, the response observed for the SM factor varied from year to year, indicating for the overall reference period 2022-23 higher soil CO2 flux under the mulched soils (0.24 ± 0.01 mg m−2 s−1) than under bare soil conditions (0.15 ± 0.00 mg m−2 s−1). Inter-annual variations were also observed as function of the day-of-year (DOY), the SM and their interactions, resulting in higher soil CO2 flux under the mulched soils (0.24 ± 0.02 mg m−2 s−1) than under bare soil (0.15 ± 0.01 mg m−2 s−1) in certain periods of the years, according to the environmental conditions. Resultssuggest the importance of integrating soil CO2 flux measurements with ancillary variables that explain the variability of the agrosystem and the need to conduct the measurements using different operational modalities, also providing for night-time monitoring of CO2. In addition, the study underlines that the small-scale chamber measurements can be used to estimate soil CO2 fluxes at orchard scale if fluxes are properly scaled.

High-Efficient Direct Power Control Scheme Using Predictive Virtual Flux for Three-Phase Active Rectifiers

In recent years, the pulse-width-modulation (PWM) converter has been found to have extensive applications in renewable energy, industrial fields, and others. The high efficiency requirement is crucial to operating a PWM rectifier in various applications, in addition to the fundamental control objectives of sinusoidal grid currents and the correct DC bus voltage. Additionally, in practical application, another issue arises when the grid voltage frequently experiences distortion, leading to a distorted grid current and a significant rise in total harmonic distortion (THD). To resolve these problems, a model predictive virtual flux-based direct power control (MPVFDPC) with improved power loss performance is proposed based on an integrated switching state predetermination strategy. The proposed MPVFDPC for PWM rectifier inherits the merits of both virtual flux control and direct power control, which have fast dynamic performance and the grid current THD is considerably decreased under distorted grid voltage states. The proposed technique aims to minimize switching loss under ideal and distorted grid voltage states by exploiting the discontinuous modulation concept by using a switching state predetermination strategy. The MPVFDPC with switching state predetermination strategy is proven by employing it in experiments as well as simulations in comparison with previous models: predictive direct power control (Conv. MPDPC) and conventional MPVFDPC (Conv. MPVFDPC). The acquired waveforms and quantitative data are employed to prove the effectiveness of the developed algorithm.

Activator effect on sawdust-based adsorbent efficiency: application to organic pollutants decontamination

The aim of this study is to valorize available Sawdust as a ligno-cellulosic and locally abundant solid waste generated by different activities, via combined chemical and physical activations route and its application for the removal of hydroxybenzene as a toxic pollutant from aqueous solution in discontinuous mode. Enhancement of adsorption capacities by impregnating separately the powdered sawdust in acidic (phosphoric acid: 20%), basic (potassium hydroxide: 20%) and salty (Ammonium Persulfate: 0.1M) solutions then pyrolysis at 600°C for 1hour in tubular furnace resulting in SWDA, SWDB and SWDS- based adsorbents. The adsorptive rates of the obtained adsorbents were compared to the commercial activated carbon from Merck taken as a reference. The batch adsorption experiments resulted in a maximum adsorption capacities obtained from Langmuir model of up to 192.31, 123.56 and 109.89 and 133.33 mg/g for SWDA, SWDB, SWDS and Merck respectively. Conventional parameters influencing the removal capacity of the considered pollutant such as contact time, adsorbent dosage, pH, initial concentration and temperature were also studied. Samples characterization was carried out using Fourier-transform infrared spectroscopy (FTIR) analyses for functional groups determination, Iodine number test for porosity and scanning electronic microscopy (SEM) for microstructure examination of the samples. Adsorption kinetics was found to comply with the pseudo second order with a good correlation factor (R2 &gt; 0.99) with intra-particle diffusion as the rate determining steps. Thermodynamics of Hydroxybenzene adsorption process was spontaneous (ΔG o &lt;0) and endothermic (ΔHo &gt;0). This study showed that sawdust as a waste could prove to be a very efficient adsorbent in removing toxic substances from wastewater.

Effect of Pt nanoparticle size on resistance to chloride-induced inhibition for hydrodechlorination of trichloroethylene in water

Catalysts used for hydrodechlorination (HDC) of trichloroethylene (TCE) undergo partial or complete loss of catalytic activity due to inhibition by inevitable reaction product HCl. Changing the size of Pt NPs could be used as a strategy to prevent inhibition of HDC catalysts if the structure sensitivity of the reaction was known. This study aims to obtain structure-sensitivity of aqueous-phase HDC of TCE and investigate the effect of Pt NPs’ size on resistance to chloride inhibition. The research encompassed the synthesis of Pt NPs, characterization studies, and catalytic activity measurements at 30 °C & 1 atm H2 in batch or discontinuous pulse mode. Characterization results showed that targeted Pt NPs were successfully synthesized with average particle sizes of 3.0 nm, 5.8 nm, 8.9 nm, and 60.9 nm. Catalytic activity experiments revealed that initial turnover frequency values exhibited a decrease with increasing particle size of Pt NPs, indicating that aqueous-phase HDC of TCE is a structure sensitive reaction. The fastest kinetics and the highest resistance to HCl inhibition were observed over the smallest Pt NPs employed in this study. This information can serve as a rational synthesis parameter for designing catalysts that could mitigate chloride inhibition caused by the reaction product HCl.

Hybrid approach for 3 phase bridgeless AC to DC Cuk converter for WECS

ABSTRACT This manuscript proposes a novel hybrid method based on a single-stage three-phase bridgeless alternating current (AC) to direct current (DC) Cuk converter for wind energy conversion systems (WECS). The proposed hybrid method is the combination of Mexican Axolotl Optimization (MAO) and Fuzzy Wavelet Neural Network (FWNN), hence it is named as MAO-FWNN method. Moreover, the proposed method enhanced the system performance by distributing the defined reactive-power to harmonic reduction and doubly fed induction generator (DFIG). The proposed converter is modelled under a discontinuous mode of the inductor current. The converter’s output inductor is modelled as a continuous inductor current mode, and it functions to provide enhanced power quality (PQ) and low DC (Direct Current) voltage ripple. At that point, the MATLAB platform is used to execute the performance of the proposed method, and it is compared with existing methods. The performance of the proposed method provides the 0.095 to 0.096 times/sec, which is higher than the existing methods. As a result, the proposed technique is well established compared to the existing techniques.

Modulation Techniques and Coordinated Voltage Vector Distribution: Effects on Efficiency in Dual-Inverter Topology-Based Electric Drives

The increasing popularity of electric drives employing an isolated dual-inverter (DI) topology is motivated by their superior DC-link voltage and power utilization, fault-tolerant operation, and potential for multilevel operation. These attributes are significant in battery-powered transportation, such as electric vehicles and aviation. Given the considerable freedom in modulation and control of the DI topology, this paper researches the impact of reference voltage vector distribution between the two individual inverters. The study also evaluates the influence of two well-established asynchronous modulation strategies—Space Vector PWM (SVPWM) and Depenbrock’s Discontinuous Modulation (DPWM1). Since simulation tools nowadays play a crucial role in power electronics design and concept verification, the results are based on extensive and detailed models in Matlab/Simulink. Employing the basic field-oriented control of a 12 kW induction motor with precisely parameterized SiC switching devices for accurate loss calculation, this research reveals the possibility of significant energy savings at multiple operating points. Notably, optimal efficiency is achieved when one inverter operates up to half of the nominal speed while the other solely establishes a neutral point for the winding. Moreover, the results highlight DPWM1 as a superior strategy for the DI topology, showcasing reduced converter losses. Overall, it is shown that the system’s losses can be significantly reduced just by the design of the voltage vector distribution in the drive’s operating range and the modulation strategy selection.

A Photovoltaic-based Novel Transformerless High Gain Converter for DC Microgrid Applications

Aim: A typical microgrid network sourced by renewable energy encounters a technical setback owing to the voltage imbalance across the source integration and load power dissemination. Transformers employed to stabilize the potential may deteriorate the network efficiency and increases the cost and size of the system as well. Introduction: Photovoltaic based transformerless high gain DC-DC converter (THG-DC) is proposed here to aid the microgrid infrastructure. Microgrid fuelled by renewable energy sources demands the high gain converter interface to boost low voltage generation. The proposed THG-DC is employed with four switched inductors and three active power switches (IGBT) which are brought together under dual leg configurations. Methods: The proposed topology offers dual-duty cycle modes of regulating the active switches to realize the desired output voltage. Moreover, it is reliable to drive the proposed THG-DC with lower values of duty cycles to achieve a higher gain. The voltage stress across the switches is minimized and the magnitude of inductor current ripples is quashed to an extent. The proposed THGDC is simple in architecture and easy to control in all three operating modes. Results: The operating characteristics and performance investigation of the novel converter during the continuous and discontinuous modes are elucidated briefly and the comparative analysis on switching stress, gain, and efficiency are executed to justify the standards of the proposed THGDC. Conclusions: Finally, the miniature prototype model is experimented with in the laboratory (0.3 kW) and the obtained results are in agreement with the theory. It is evident from the investigations that the proposed THG-DC shows its dominance over other converters on the voltage gain, switching stress, number of components, and overall efficiency.