Search Results (783)

The surface morphology of high molecular weight poly(styrene-b-isoprene) block copolymer was analyzed after chemical modification. Poly(styrene-b-isoprene) was converted into poly(styrene-b-(ethylene-alt-propylene)) by hydrogenation and into poly(styrene-b-sulfonated isoprene) by mild sulfonation of the PI block. Obtained morphologies were examined by atomic force microscopy, analyzing the effect of sample preparation parameters such as solvent (tetrahydrofuran, toluene, and cyclohexane), casting technique (spin casting and drop casting), and annealing temperature [room temperature, 80, 100, and 120 °C]. Significant morphological and topographical changes were found depending on the different parameters. Each modification step introduces new variables that can affect the final structure and properties of the copolymer. Finding the balance between solvent choice, casting technique, and annealing conditions was a difficult task and required extensive experimentation and understanding of the principles of block copolymer self-assembly. Full article

Low-light image enhancement (LLIE) remains a challenging task due to the scarcity of paired training data and the complex signal-dependent noise inherent in low-light scenes. To address these issues, this paper proposes a fully unsupervised framework named Wavelet-Guided Zero-Reference Diffusion (WZD) for natural low-light image restoration. WZD leverages an ImageNet-pre-trained diffusion prior and a multi-scale representation of the Discrete Wavelet Transform (DWT) to restore natural illumination from a single dark image. Specifically, the input low-light image is first processed by a Practical Exposure Corrector (PEC) to provide an initial robust luminance baseline. It is then converted from the RGB to the YCbCr color space. The Y channels of the input image and the current diffusion estimate are decomposed into four orthogonal sub-bands—LL, LH, HL, and HH—and fused via learnable, step-wise weights while preserving structural integrity. An exposure control loss and a detail consistency loss are jointly employed to suppress over/under-exposure and preserve high-frequency details. Unlike recent approaches that rely on complex supervised training or lack physical guidance, our method integrates wavelet guidance with a zero-reference learning framework, incorporates the PEC module as a physical prior, and achieves significant improvements in detail preservation and noise suppression without requiring paired training data. Comprehensive experiments on the LOL-v1, LOL-v2, and LSRW datasets demonstrate that WZD achieves a superior or competitive performance, surpassing all referenced unsupervised methods. Ablation studies confirm the critical roles of the PEC prior, YCbCr conversion, wavelet-guided fusion, and the joint loss function. WZD also enhances the performance of downstream tasks, verifying its practical value. Full article

Rice is a staple food for global nutrition, and its processing generates large volumes of waste with a consequent environmental impact. The industry needs to improve its capacity to manage and treat this waste with more sustainable options than traditional management methods, thereby mitigating the environmental impact of the rice industry. Among the waste streams generated, rice bran represents a significant fraction that is largely underutilized. This study proposes a comprehensive approach to rice bran recovery, aiming to transform 100% of the waste into bio-based products through a three-stage biorefinery approach that combines chemical and biological operations. The process began with the ethanolic extraction of rice bran, which yielded 20.58% (w·w⁻¹) rice bran oil. This oil, evaluated through both in vitro and in vivo trials, has demonstrated effectiveness when combined with commercial edible coatings, reducing post-harvest damage in grapes and lemons by 15–20%. Following extraction, the remaining defatted rice bran, accounting for 79.42% (w·w⁻¹) of the initial material, was used as a carbon-rich substrate for microbial fermentation by Haloferax mediterranei. This step converts 28.75% (w·w⁻¹) of rice bran into microbial biomass and 12.75% (w·w⁻¹) into polyhydroxybutyrate-valerate. The undigested residual biomass, comprising 37.95% (w·w⁻¹) of the starting material, was further valorized through the purification of high-value products such as cellulose (13.08% (w·w⁻¹)), hemicellulose (14.58% (w·w⁻¹)), and lignin (10.29% (w·w⁻¹)). Overall, the biorefinery model recovers 100% of the initial waste and demonstrates, under laboratory conditions, the model’s ability to transform rice bran into six products of industrial interest, offering an option with the potential to effectively manage rice bran waste and help circularize the production model of an industry that traditionally operates under a linear production model. Full article

Maritime power systems must reduce fuel use and emissions while improving resilience. We study a shipboard PV–battery subsystem interfaced with a DC–DC converter running maximum power point tracking (MPPT) and curve-scanning GMPPT to manage partial shading. Dynamic average-value models capture irradiance steps and show GMPPT sustains operation near the global MPP without local peak trapping. We compare converter options—conventional single-port stages, high-gain bidirectional dual-PWM converters, and three-level three-port topologies—provide sizing rules for passives, and note soft-switching in order to limit loss. A Fourier framework links the switching ripple to power quality metrics: as irradiance falls, the current THD rises while the PCC voltage distortion remains constant on a stiff bus. We make the loss relation explicit via $I_{rms}^{2}R$ scaling with THDi and propose a simple reactive power policy, assigning VAR ranges to active power bins. For AC-coupled cases, a hybrid EMT plus transient stability workflow estimates ride-through margins and critical clearing times, providing a practical path from modeling to monitoring. Full article

Electric vehicles (EVs) are experiencing rapid global adoption driven by environmental concerns and fuel security. This article presents a new dual-source converter based on a hybrid modular multilevel configuration (DCHMMC) designed for optimal cell utilisation in EV battery systems. Contrary to conventional converters that can either charge or discharge the cells using a single source, thereby leaving several cells/modules (Ms) idle during each time step, the proposed converter enables the integration of two sources that can utilise the cells simultaneously. This dual source feature minimises idle cells/Ms, enhances energy efficiency, and supports flexible bidirectional power flow. The proposed converter operates in three distinct modes. The first involves dual-source charging for fast charging and improved vehicle availability. The second involves one source charging while the other discharges for dynamic operation. Finally, the last involves dual-source discharging for maximum power delivery and support vehicle-to-grid (V2G) operation. The simulation results demonstrated smooth multilevel sinusoidal output voltages (Vout_a and Vout_b), each with a peak of 350 V, generated simultaneously using 132 cells (six cells per M, 22 Ms). The total harmonic distortion (THD) values for Vout_a and Vout_b were 0.42% and 2.25%, respectively, confirming the high-quality performance. Furthermore, only 0–36 cells and 0–6 Ms were idle during operation, showing improved cell utilisation. Full article

For the application of a high-performance shortwave infrared (SWIR) detector, a fully integrated analog front-end (AFE) circuit is proposed in this paper, which includes a readout integrated circuit (ROIC) and a 12-bit/100 kHz two-step single-slope analog-to-digital converter (TS-SS ADC). The ROIC adopts a direct injection (DI) structure with a pixel size of only 10 µm × 10 µm. The column processing circuit uses a passive correlated double-sampling (CDS) circuit to reduce noise and improve dynamic range. The comparator of four inputs in the ADC solves the problem of linearity reduction caused by charge redistribution during coarse quantization. In addition, the current steering digital-to-analog converter (DAC) is used to compensate for the non-ideal characteristics of the switch, which effectively optimizes the differential nonlinearity (DNL) and integral nonlinearity (INL). The AFE is implemented using SMIC 180 nm 1P6M technology. The post-simulation results show that at a power supply voltage of 3.3 V, the AFE has a frame rate of 100 Hz and a full well capacity (FWC) of 2.8 Me⁻. The linearity can reach 99.59%, and the equivalent output noise is 243 µV. The dynamic range is 73.8 dB. Meanwhile, the signal-to-noise distortion ratio (SNDR) and effective number of bits (ENOB) are 68.38 dB and 11.06 bits, respectively. Full article

In this study, the authors demonstrate the development and evaluation of an optimal frequency control controller for an interlinked two-area power system that incorporates Renewable Energy Sources (RESs). In decentralized power grids, the Load Frequency Control (LFC) system allows scheduled tie-line power as well as system frequency to be reimposed to their nominal values. Designing an advanced controller might enhance the functionality of the LFC mechanism. This article illustrates the possible impacts of converter capacitors using the new High-Voltage Direct Current (HVDC) tie-line model as well as the Inertia Emulation Technique (IET). This paper suggests a new adaptive control procedure for the expected LFC mechanism: an ANN-based (PI^λ + PI^λf) controller. The authors evaluate which control parameters are most effective using a modified version of the Quasi-Opposition-learning-based Reptile Search Algorithm (QORSA) method. Software called MATLAB/Simulink-2015 is used to create this arrangement. The use of established techniques for handling step as well as random load disturbances has enabled an evaluation of the suggested LFC architecture’s efficacy. An IET-based HVDC tie-line reduces overshoot by 100% in Areas 1 and 2 (Area 1 frequency deviation, i.e., ∆f₁, as well as Area 2 frequency deviation, i.e., ∆f₂). When considering SLD, the suggested controller outperforms the most widely used alternative settings. The IEEE-39 bus system has been changed by the addition of RESs. The IEEE-39 bus system is composed of three control areas. It is confirmed how the IEEE-39 bus system reacts to changes in frequency in Areas 1, 2, and 3. It is illustrated how to use the suggested controller in the modified IEEE-39 bus system, accompanied by real-time load variations. Recent research indicates that the suggested control method is better and more efficient due to its 100% decrease in overshoot in Areas 1 and 2 and quick response time. Full article

This paper introduces a new four-switch, high-voltage, high-step-up converter employing two transformers. The topology enables Zero-Voltage Switching (ZVS) across all primary switches for operating conditions ranging from no load to full load. A voltage-quadrupler and a voltage-doubler rectifier are used on the secondary sides of the transformers, enabling reduced turn-off current for the voltage-quadrupler diodes and Zero-Current Switching (ZCS) turn-off for the voltage-doubler diodes, thereby ensuring high efficiency across diverse load levels. Notably, the voltage stress experienced by the voltage-multiplier diodes is significantly lower than the output voltage, thereby rendering the converter exceptionally suitable for high-voltage applications such as electron beam welding (EBW). The voltage gain surpasses that of the conventional phase-shift full-bridge (PSFB) converter, permitting a lower transformer turns ratio and thus reducing winding resistivity. The removal of the substantial output inductor leads to a lighter and more compact design, eliminating insulation concerns associated with inductor windings. This paper details the operation of the proposed converter, supported by experimental results from a 500-W prototype with a 150-V input and 2-kV output, which confirm its high performance and operational advantages. Full article

This study presents a novel, circular-economy-driven strategy for valorizing post-consumer denim waste into high-performance hydrogels through a fully integrated and eco-friendly process. Unlike conventional approaches that rely on virgin cellulose or harsh chemical treatments, our method uniquely combines high-energy mechanochemical pretreatment, in situ carboxymethylation to produce carboxymethylcellulose (CMC), and citric acid/urea-based crosslinking, all using recycled denim as the sole cellulose source. High-energy milling effectively reduced particle size and lowered the crystallinity index (CI) from 75.7% to 66.1%, transforming the fibrous structure into a more reactive substrate for etherification. Successful CMC synthesis was confirmed by FTIR (COO⁻ stretch at 1587 cm⁻¹), while citric acid crosslinking generated ester bonds (C=O at ~1724 cm⁻¹), forming a 3D network further tailored by urea, acting as a green porogen. The resulting hydrogels exhibited enhanced thermal stability (TGA) and a tunable porous morphology (SEM), with pore sizes reaching up to 147 µm as the urea content increased. Notably, the hydrogel Hy/CMC/U2/CA achieved an exceptional swelling capacity of 1900%, which is among the highest reported for denim-derived or citric acid-crosslinked systems. The objective of this work is to demonstrate, for the first time, the feasibility of converting waste denim directly into functional hydrogels without intermediate purification steps, offering a scalable and sustainable route for agricultural applications, such as soil water retention, controlled nutrient release, or environmental remediation, within a true circular economy framework. Full article

Following on from a circular economy in water, membrane technologies can play a role in resource recovery and high-quality water production but should also consider membrane industry circularity. Anaerobic membrane bioreactors (AnMBRs) are being used for advanced wastewater treatment, and their applications are growing due to advantages like lower sludge volume, better permeate quality, and the generation of biogas. High-Rejection (HR) AnMBRs retain a higher fraction of dissolved and particulate components to further promote resource recovery and obtain improved effluent quality. With the development of membrane technologies, end-of-life (EOL) membrane recycling is emerging for various applications. The feasibility of transforming EOL Reverse Osmosis (RO) membranes into ultrafiltration (UF)- and nanofiltration (NF)-like membranes and applying these membranes to submerged HR-AnMBR applications was evaluated. A small pilot AnMBR with granular biomass was operated with EOL RO membranes converted to submerged UF- and NF-like membranes and compared to commercial microfiltration (MF) membranes. UF- and NF-like plates were constructed, characterized, and introduced step-by-step into the AnMBR by the substitution of MF plates. A chemical oxygen demand (COD) removal study showed that while 77% removal of COD was possible with MF membranes, improved COD removal (i.e., 81.40% and 88.39%) was achieved using UF-like and NF-like membranes, respectively. Because of the higher retention of salts of the NF-like membrane, the salinity in the membrane bioreactor increased from 1300 to 1680 µS·cm⁻¹ but stabilized quickly and without a negative impact on system performance. Even without cleaning, minimal fouling and flux decline were observed for all tested configurations thanks to the use of granular biomass and low permeation flux. Permeate flux in the case of the NF-like membrane was slightly lower due to the required higher pressure. The present study demonstrated that the EOL-RO membranes may find applications in HR-AnMBRs to achieve superior permeate quality and move toward circular membrane processes. Full article

This paper presents an enhanced non-isolated single-switch quadratic boost DC-DC converter. The proposed topology employs a single active switch, two inductors, two capacitors, and three diodes. The proposed design improves system reliability by replacing one of the active switches in a conventional cascaded boost converter with a diode. Two key features of this converter are its single switch, which simplifies operation, and the use of a lifting capacitor for voltage step-up. The reduced switch count and the use of Schottky diodes minimize switching losses and enhance overall efficiency. Comprehensive theoretical steady-state analysis under continuous conduction mode (CCM) is carried out to characterize the converter’s performance. Notably, at a 50% duty cycle, the converter achieves a voltage gain of four, while at a 70% duty cycle, it can reach a voltage gain of approximately 11. The proposed topology is validated through extensive simulations in MATLAB/Simulink (2023). In addition, a prototype with a 5 V input and 20 V output at a switching frequency of $50\mathrm{kHz}$ was constructed and tested. The experimental unit achieved an efficiency of about 85% at a 5 V input. The results confirm that the converter achieves high voltage gain and improved efficiency, making it well-suited for IoT and energy harvesting applications. Full article

The growing demand for traceable, high-precision attenuation measurements in electromagnetic compatibility (EMC) testing and low-frequency wireless communication systems has driven the development of a primary attenuation standard covering 1 kHz to 10 MHz. The system employs a dual channel null-detection method using an inductive voltage divider (IVD) as a reference, ensuring the highest accuracy and traceability while eliminating sensitivity to detector nonlinearity. Attenuation at 1 kHz, 9 kHz, and 10 kHz is measured directly against the IVD ratio, while higher-frequency measurements (100 kHz–10 MHz) are performed via heterodyne detection, down-converting signals to 1 kHz for comparison. To ensure comparable accuracy at higher attenuation levels, a double-step method is applied at 9 kHz and 10 kHz to mitigate the increased IVD uncertainty above 1 kHz. Linearity is ensured by suppressing common-mode currents with toroidal ferrite chokes and minimizing inter-channel coupling. Type B (non-statistical) measurement uncertainties are evaluated, with major contributions from the IVD reference, system errors, and mismatch. The expanded uncertainties are 2.2 × 10⁻³ dB at 20 dB, 3.0 × 10⁻³ dB at 40 dB, and 4.0 × 10⁻³ dB at 60 dB attenuation. To facilitate wider dissemination and extend the calibration range, a resistive step attenuator with 10 dB pads is evaluated as a practical transfer standard, providing a simple and robust solution for traceable attenuation calibration in this frequency range. Full article

This study presents a sustainable upcycling strategy to convert “Pit,” a carbon-rich coke oven by-product from steel manufacturing, into high-purity graphite for use as an anode material in lithium-ion batteries. Despite its high carbon content, raw Pit contains significant impurities and has irregular particle morphology, which limits its direct application in batteries. We employed a multi-step, additive-free refinement process—including jet milling, spheroidization, and high-temperature graphitization—to enhance carbon purity and structural properties. The processed Pit-derived graphite showed a much-improved particle size distribution (D50 reduced from 25.3 μm to 14.8 μm & Span reduced from 1.72 to 1.23), increased tap density (from 0.54 to 0.80 g/cm³), and reduced BET surface area, making it suitable for high-performance lithium-ion batteries anodes. Structural characterization by XRD and TEM confirmed dramatically enhanced crystallinity after graphitization (graphitization degree increasing from ~13 for raw Pit to 95.7% for graphitized Pit at 3000 °C). The fully processed graphite (denoted S_Pit3000) delivered a reversible discharge capacity of 346.7 mAh/g with an initial Coulombic efficiency of 93.5% in half-cell tests—comparable to commercial artificial graphite. Furthermore, when composited with silicon oxide to form a hybrid anode, the material achieved an even higher capacity of 418.0 mAh/g under high mass loading conditions. These results highlight the feasibility of transforming industrial coke waste into value-added electrode materials through environmentally friendly physical processes. The upcycled graphite anode meets industrial performance standards, demonstrating a promising route toward circular economy solutions in both the steel and battery industries. Full article

The production of green hydrogen by microalgae is a promising strategy to convert energy of sun light into a carbon-free fuel. Many problems must be solved before large-scale industrial applications. One solution is to find a microalgal species that is easy to grow, easy to manipulate, and that can produce hydrogen open-air, thus in the presence of oxygen, for periods of time as long as possible. In this work we investigate by means of predictive computational models, the [FeFe] hydrogenase enzyme of Nannochloropsis salina, a promising microcalga already used to produce high-value products in salt water. Catalysis of water reduction to hydrogen by [FeFe] hydrogenase occurs in a peculiar iron-sulfur cluster (H-cluster) contained into a conserved H-domain, well represented by the known structure of the single-domain enzyme in Chlamydomonas reinhardtii (457 residues). By combining advanced deep-learning and molecular simulation methods we propose for N. salina a two-domain enzyme architecture hosting five iron-sulfur clusters. The enzyme organization is allowed by the protein size of 708 residues and by its sequence rich in cysteine and histidine residues mostly binding Fe atoms. The structure of an extended F-domain, containing four auxiliary iron-sulfur clusters and interacting with both the reductant ferredoxin and the H-domain, is thus predicted for the first time for microalgal [FeFe] hydrogenase. The structural study is the first step towards further studies of the microalga as a microorganism producing pure hydrogen gas. Full article

This work introduces a non-isolated high step-up dc-dc interleaved boost converter combining magnetic coupling and voltage multiplier cells (VMCs). The proposed topology features a transformer with two primary windings of equal turns, interconnected to each other, enabling improved current sharing, and multiple secondary windings that contribute to extending the voltage gain. A three-winding coupled inductor is integrated into the design, while VMCs not only boost the output voltage but also significantly reduce the voltage stresses on the switches, eliminating the need for extreme duty ratios. The converter exhibits inherent modularity, allowing for voltage gain adjustments either through the turns ratio of the coupled inductor or by incorporating additional VMCs. An in-depth analysis of the topology is derived, and an experimental prototype rated at 48 V/400 V, 25 kHz, and 1 kW is implemented to verify and validate the theoretical claims, achieving an efficiency of 95.12% at full-load conditions. Full article