Search Results (1,507)

This research aims to determine the state of Industry 4.0 readiness and to identify the best practices, challenges, and barriers to implementing Industry 4.0 technology in a medical device manufacturer, thus aiding in improving sustainability. Semi-structured interviews were completed with 12 senior executives representing a wide array of functions in a single large medical device manufacturer. Convenience sampling was used to analyse the interview transcripts to draw out themes that were then discussed and analysed with findings from the literature review. This research determined the state of Industry 4.0 readiness in the case study of medical device manufacturers. This research identified several best practices, challenges, and barriers to implementing Industry 4.0 technology. Currently, there are few case studies in the literature that have a medical device manufacturer as the case study for Industry 4.0 readiness. There are even fewer articles that tackle Industry 4.0 implementation across the entire medical device industry. There is currently no published literature that analyses the best practices for implementing Industry 4.0 in a medical device manufacturer. The best practices for Industry 4.0 implementation identified in this study can be beneficial to stakeholders in the medical device industry and within the healthcare sector, help them plan current and future Industry 4.0 programmes, improve sustainability in their companies, as well as optimise patient treatment and approaches. Full article

In this study, it is shown that an efficient organic optocoupler (OPC) can be fabricated using commercially available and solution-processable organic semiconductors. The transmitter is a single-active-layer organic light-emitting diode (OLED) made from a well-known polyparavinylene derivative, Super Yellow. The receiver is an organic light-emitting diode (OLSD) with a single active layer consisting of a mixture of the polymer donor PTB7-Th and the low-molecular-weight acceptor ITIC; the receiver operates without an applied reverse voltage. OLED and OLSD have the same geometry and simple structure without any interlayers: glass/ITO/PEDOT:PSS/(active layer)/Ca/Al; the OPC is formed by OLED and OLSD which adhere tightly to each other. Despite its simple structure, the OPC showed a current transfer ratio of 0.13%, good linearity, and good dynamic performance: a three-decibel cutoff frequency of 170 kHz and response times to a step change in current at the OPC input of 2 μs. Compared to most organic OPC devices with similar performance parameters, where the transmitter and receiver have complex structures with additional interlayers between the active layers and electrodes and the need to apply a reverse voltage to the receiver, the simple design of our OPC reduces the number of fabrication steps and greatly simplifies the device fabrication process. Full article

Understanding the influence of heat transfer on the pyrolysis process is crucial for optimizing industrial biofuel production processes. While numerous scientific studies focus on experimental investigations of pyrolysis using laboratory-scale devices, many neglect the essential role of thermal energy in initiating and controlling thermal decomposition processes. This study presents a transient two-dimensional numerical model of biomass single-particle pyrolysis, which includes the energy balance, mass conservation equations and pyrolysis gas pressure and velocity equations. The model employs explicit numerical methods to manage the high computational demands of 2D transient simulations, but is successfully validated with the use of experimental data found in the literature. The model reflects the heterogeneous structure of wood by using different thermal conductivity coefficients depending on the wooden fibers’ orientation. The results demonstrate the impact of fiber orientation on the heat transfer and thermal decomposition processes. The anisotropic properties of wood led to varied temperature fields and pyrolysis decomposition stages, aligning well with experimental data, thus validating the model’s accuracy. The proposed approach can provide a better understanding and lead to improvement in biofuel production processes, enabling more efficient and controlled conversion of biomass into fuel. By optimizing the pyrolysis process, it contributes to the development of sustainable energy preservation and regeneration methods, supporting a shift towards more sustainable fuel production patterns using renewable biomass resources like wood. Full article

This study describes experimental data on 3D-printed compact heat exchangers. The heat exchanger is a prototype designed and manufactured additively using 3D printing in metal—AISI 316L steel. The device’s design is based on the triply periodic minimal surface (TPMS) geometry called gyroid, which can only be obtained by incremental manufacturing. This innovative heat exchange surface structure enables these devices to provide higher thermal performance while reducing their weight by up to 50%. Few publications describe thermal or flow tests in this type of device. They mainly concern computer simulations that have yet to be experimentally verified. The authors of this study conducted innovative flow tests to determine pressure drops during the flow of working fluids under conditions of variable temperature, mass flow rate and thermal load. Water was used as a heat transfer fluid during the tests. The range of parameters for the entire experiment was ṁ = 1–24 kg/h; Δp/Δl = 0.05–2 kPa; t_cold = 20 °C; t_hot = 50 °C. Flow characteristics during the single-phase heat exchange process were determined, including Δp/Δl = f(ṁ), Δp/Δl = f(Re), Δp/Δl = f(f). The experimental data will be used to determine the relationships describing flow resistance in structures based on a triply periodic minimal surface, and it also enables one to specify the energy consumption of these devices and compare the profitability of their use to conventional designs, i.e., shell-and-tube or plate heat exchangers. Full article

This paper explores the potential of phase change materials (PCM) for dynamically tuning the frequency response of a dumbbell u-slot defected ground structure (DGS)-based band stop filter. The DGSs are designed using co-planar waveguide (CPW) line structure on top of a barium strontium titanate (Ba_0.6Sr_0.4TiO₃) (BST) thin film. BST film is used as the high-dielectric material for the planar DGS. Lower insertion loss of less than −2 dB below the lower cutoff frequency, and enhanced band-rejection with notch depth of −39.64 dB at 27.75 GHz is achieved by cascading two-unit cells, compared to −12.26 dB rejection with a single-unit cell using BST thin film only. Further tunability is achieved by using a germanium telluride (GeTe) PCM layer. The electrical properties of PCM can be reversibly altered by transitioning between amorphous and crystalline phases. We demonstrate that incorporating a PCM layer into a DGS device allows for significant tuning of the resonance frequency: a shift in resonance frequency from 30.75 GHz to 33 GHz with a frequency shift of 2.25 GHz is achieved, i.e., 7.32% tuning is shown with a single DGS cell. Furthermore, by cascading two DGS cells with PCM, an even wider tuning range is achievable: a shift in resonance frequency from 27 GHz to 30.25 GHz with a frequency shift of 3.25 GHz is achieved, i.e., 12.04% tuning is shown by cascading two DGS cells. The results are validated through simulations and measurements, showcasing excellent agreement. Full article

This study introduces a novel single-degree-of-freedom polycentric knee mechanism specifically designed for transfemoral prostheses to address dual challenges of stability during the stance phase and biomimetic motion during the swing phase. Leveraging analytical kinematic synthesis, the proposed mechanism integrates separate kinematic designs for each of the gait phases into a combined structure that prevents singularity issues during full knee flexion, which is a significant limitation in conventional active designs. The stance phase mechanism emphasizes stability through precise control of the instantaneous center of rotation (ICR) and weight-bearing support, while the swing phase mechanism adopts a biomimetic motion trajectory. In order to validate the proposed methodology, kinematic synthesis, numerical simulations, and visual analyses were conducted. Incorporating insights from polycentric prostheses and orthotic applications, the proposed mechanism achieves a seamless transition between two different configurations by keeping its overall mobility. Additionally, its possible compatibility with motorized actuation offers a foundation for active prosthesis systems, paving the way for adapting the advantages of polycentric prosthesis to active devices. This innovative approach offers a scientifically grounded pathway for improving transfemoral prosthetic systems, advancing both their biomechanical utility and user comfort. Full article

Remote sensing imagery contains rich information about geographical targets, and performing super-resolution (SR) reconstruction on such images requires greater feature representation capabilities. Convolutional neural network (CNN)-based methods excel at extracting intricate local features but fall short in terms of capturing global representations. While transformer methods are capable of learning long-distance dependencies, they often overlook local feature details, which can diminish the discriminability between the background and the foreground. Moreover, the distinctive architectures of transformers, their extensive parameter counts, and their reliance on large-scale training datasets impose constraints on transformer applications in remote sensing image feature extraction tasks. To address these challenges, this study introduces a novel hybrid CNN-Transformer network model named RepCHAT for remote sensing single image reconstruction, which incorporates a structural re-parameterization technique and a hybrid attention mechanism. This method leverages the strengths of transformers in terms of learning long-distance dependencies (global features) and CNNs with respect to extracting local features. The proposed approach achieves SR reconstruction for remote sensing images with fewer parameters and less computational overhead than those of traditional transformers and high-performance CNN models. We develop a multiscale feature extraction module that integrates both spatial- and frequency-domain features and employs structural re-parameterization theory to increase the inference efficiency of the model. Furthermore, we incorporate depthwise-separable convolution into the transformer block to bolster the local feature learning capabilities of the transformer. The method we propose achieves the optimal performance for remote sensing single-image super-resolution reconstruction and outperforms the competing methods by 0.28–1.05 dB (×4 scale) in terms of signal-to-noise ratio (PSNR). Experimental results indicate that the RepCHAT model proposed in this study maintains a high performance with significantly reduced complexity, making it suitable for deployment on edge devices. Full article

Automated agricultural robots are becoming more common with the decreased cost of sensor devices and increased computational capabilities of single-board computers. Weeding is one of the mundane and repetitive tasks that robots could be used to perform. The detection of weeds in crops is now common, and commercial solutions are entering the market rapidly. However, less work is carried out on combatting weeds in pastures. Weeds decrease the grazing yield of pastures and spread over time. Mowing the remaining weeds after grazing is not guaranteed to remove entrenched weeds. Periodic but selective cutting of weeds can be a solution to this problem. However, many weeds share similar textures and structures with grazing plants, making their detection difficult using the classic RGB (Red, Green, Blue) approach. Pixel depth estimation is considered a viable source of data for weed detection. However, systems utilizing RGBD (RGB plus Depth) are computationally expensive, making them nonviable for small, lightweight robots. Substituting one of the RGB bands with depth data could be a solution to this problem. In this study, we examined the effect of band substitution on the performance of lightweight YOLOv8 models using precision, recall and mAP50 metrics. Overall, the RDB band combination proved to be the best option for YOLOv8 small and medium detection models, with 0.621 and 0.634 mAP50 (for a mean average precision at 50% intersection over union) scores, respectively. In both instances, the classic RGB approach yielded lower accuracies of 0.574 and 0.613. Full article

Optoelectronic devices combining single-layer graphene (SLG) and colloidal semiconducting nanocrystal (NC) heterojunctions have recently gained significant attention as efficient hybrid photodetectors. While most research has concentrated on systems using heavy metal-based semiconductor NCs, there is a need for further exploration of environmentally friendly nanomaterials, such as Cu_2−xS. Chemical ligands play a crucial role in these hybrid photodetectors, as they enable charge transfer between the NCs and SLG. This study investigates the photoresponse of an SLG/Cu_2−xS NCs heterojunction, comparing the effect of two short molecules—tetrabutylammonium iodide (TBAI) and 3,4-dimethylbenzenethiol (DMBT)—as surface ligands on the resulting structures. We have analysed charge transfer at the heterojunctions between SLG and the Cu_2−xS NCs before and after modification with TBAI and DMBT using Raman spectroscopy and transconductance measurements under thermal equilibrium. The photoresponse of two hybrid devices based on three layers of Cu₂₋_xS NCs, deposited in one case on SLG/Cu_2−xS/TBAI (“TBAI-only” device) and in the other on SLG/Cu_2−xS/DMBT (“DMBT + TBAI” device), with a TBAI treatment applied, for both, after each layer deposition, has been evaluated under 450 nm laser diode illumination. The results indicate that the TBAI-only device exhibited a significant increase in photocurrent (4 μA), with high responsivity (40 mA/W) and fast response times (<1 s), while the DMBT + TBAI device had lower photocurrent (0.2 μA) and responsivity (2.4 μA), despite similar response speeds. The difference is attributed to DMBT’s π–π interactions with SLG, which enhances electronic coupling but reduces SLG’s mobility and responsivity. Full article

A stacked nanocomposite zinc-tin oxide/single-walled carbon nanotubes (ZTO/SWNTs) active layer was fabricated for thin-film transistors (TFTs) as an alternative to the conventional single-layer structure of mixed ZTO and SWNTs. The stacked nanocomposite of the solution-processed TFTs was prepared using UV/O₃ treatment and multiple annealing steps for each layer. The electrical properties of the stacked device were superior to those of the single-layer TFT. The ZTO/SWNT TFT, fabricated using a stacked structure with ZTO on the top and SWNT at the bottom layer, showed a significant improvement in the field-effect mobility of 15.37 ${\mathrm{cm}}^2/\mathrm{V}·\mathrm{s}$ (factor of three increase) and an I_on/I_off current ratio of 8.83 × ${10}^8$ with improved hysteresis. This outcome was attributed to the surface treatment and multiple annealing of the selected active layer, resulting in improved contact and a dense structure. This was also attributed to the controlled dispersion of SWNT, as electron migration paths without dispersants. This study suggests the potential expansion of applications, such as flexible electronics and low-cost fabrication of TFTs. Full article

Improving microelectronic technologies has created various micro-power electronic devices with different practical applications, including wearable electronic modules and systems. Furthermore, the power sources for wearable electronic devices most often work with electrical energy obtained from the environment without using standard batteries. This paper presents the structure and electrical parameters of a circuit configuration realized as a prototype of a low-power AC-DC conversion circuit intended for use as a power supply device for signal processing systems that test various biomedical parameters of the human body. The proposed prototype has to work as a wearable self-powered system that transfers electrical energy obtained through mechanical vibrations in the piezoelectric generator. The obtained electrical energy is used to charge a single low-voltage supercapacitor, which is used as an energy storage element. The proposed circuit configuration is realized with discrete components consisting of a low-voltage bridge rectifier, a low-pass filter, a DC-DC step-down (buck) synchronous converter, a power-controlling system with an error amplifier, and a window detector that produces a “power-good” signal. The power-controlling system allows tuning the output voltage level to around 1.8 V, and the power dissipation for it is less than 0.03 mW. The coefficient of energy efficiency achieved up to 78% for output power levels up to 3.6 mW. Experimental testing was conducted to verify the proposed AC-DC conversion circuit’s effectiveness, as the results confirmed the preliminary theoretical analyses and the derived analytical expressions for the primary electrical parameters. Full article

This study reveals the significant role of the pre-melting process in growing high-quality (100) β-Ga₂O₃ single crystals from 4N powder (99.995% purity) using the edge-defined film-fed growth (EFG) method. Among various bulk melt growth methods, the EFG method boasts a fast growth rate and the capability of growing multiple crystals simultaneously, thus offering high productivity. The pre-melting process notably enhanced the structural, optical, and electrical properties of the crystals by effectively eliminating impurities such as Si and Fe. Specifically, employing a 100% CO₂ atmosphere during pre-melting proved to be highly effective, reducing impurity concentrations and carrier scattering, which resulted in a decreased carrier concentration and an increased electron mobility in the grown Ga₂O₃ single crystals. These results demonstrate that pre-melting is a crucial technique for substantially improving crystal quality, thereby promising better performance in β-Ga₂O₃-based device applications. Full article

Macroscopic structures consisting of two or more materials are called composites. The decreasing reserves of the world’s oil reserve and the environmental pollution of existing energy and production resources made the use of recycling methods inevitable. There are mechanical, thermal, and chemical recycling methods for the recycling of thermosets among composite materials. The recycling of thermoset composite materials economically saves resources and energy in the production of reinforcement and matrix materials. Due to the superior properties such as hardness, strength, lightness, corrosion resistance, design width, and the flexibility of epoxy/vinylester/polyester fibre formation composite materials combined with thermoset resin at the macro level, environmentally friendly sustainable development is happening with the increasing use of composite materials in many fields such as the maritime sector, space technology, wind energy, the manufacturing of medical devices, robot technology, the chemical industry, electrical electronic technology, the construction and building sector, the automotive sector, the defence industry, the aviation sector, the food and agriculture sector, and sports equipment manufacturing. Bonded joint studies in composite materials have generally been investigated at the level of a single composite material and single joint. The uncertainty of the long-term effects of different composite materials and environmental factors in single-lap bonded joints is an important obstacle in applications. The aim of this study is to investigate the effects of single-lap bonded GFRP (glass fibre-reinforced polymer) and CFRP (carbon fibre-reinforced polymer) specimens on the material at the end of seawater exposure. In this study, 0/90 orientation twill weave seven-ply GFRP and eight-ply CFRP composite materials were used in dry conditions (without seawater soaking) and the hand lay-up method. Seawater was taken from the Aegean Sea, İzmir province (Selçuk/Pamucak), in September at 23.5 °C. This seawater was kept in different containers in seawater for 1 month (30 days), 2 months (60 days), and 3 months (90 days) separately for GFRP and CFRP composite samples. They were cut according to ASTM D5868-01 for single-lap joint connections. Moisture retention percentages and axial impact tests were performed. Three-point bending tests were then performed according to ASTM D790. Damage to the material was examined with a ZEISS GEMINESEM 560 scanning electron microscope (SEM). The SEM was used to observe the interface properties and microstructure of the fracture surfaces of the composite samples by scanning images with a focused electron beam. Damage analysis imaging was performed on CFRP and GFRP specimens after sputtering with a gold compound. Moisture retention rates (%), axial impact tests, and three-point bending test specimens were kept in seawater with a seawater salinity of 3.3–3.7% and a seawater temperature of 23.5 °C for 1, 2, and 3 months. Moisture retention rates (%) are 0.66%, 3.43%, and 4.16% for GFRP single-lap bonded joints in a dry environment and joints kept for 1, 2, and 3 months, respectively. In CFRP single-lap bonded joints, it is 0.57%, 0.86%, and 0.87%, respectively. As a result of axial impact tests, under a 30 J impact energy level, the fracture toughness of GFRP single-lap bonded joints kept in a dry environment and seawater for 1, 2, and 3 months are 4.6%, 9.1%, 14.7%, and 11.23%, respectively. At the 30 J impact energy level, the fracture toughness values of CFRP single-lap bonded joints in a dry environment and in seawater for 1, 2, and 3 months were 4.2%, 5.3%, 6.4%, and 6.1%, respectively. As a result of three-point bending tests, GFRP single-lap joints showed a 5.94%, 8.90%, and 12.98% decrease in Young’s modulus compared to dry joints kept in seawater for 1, 2, and 3 months, respectively. CFRP single-lap joints showed that Young’s modulus decreased by 1.28%, 3.39%, and 3.74% compared to dry joints kept in seawater for 1, 2, and 3 months, respectively. Comparing the GFRP and CFRP specimens formed by a single-lap bonded connection, the moisture retention percentages of GFRP specimens and the amount of energy absorbed in axial impact tests increased with the soaking time in seawater, while Young’s modulus was less in three-point bending tests, indicating that CFRP specimens have better mechanical properties. Full article

Rice seed production is a critical step in breeding high-quality varieties. To ensure seed purity, it is essential that no residual grains or broken ears remain in the harvester header after harvesting each variety, thus preventing cross-contamination. This study addresses the issue of seed retention in existing rice harvesters, which lack efficient self-cleaning or other cleaning mechanisms and cannot be cleaned rapidly. A self-cleaning device for the harvester header was designed to enable one-click cleaning after harvesting a single variety. A novel cleaning nozzle was developed as the key component of the device, with its structure optimized through single-factor and orthogonal combination experiments. The number of nozzles was determined based on their spray width and the header width. A header-cleaning airflow simulation model based on Fluent–EDEM coupling was constructed to investigate the effects of nozzle inlet pressure, airflow incident angle, and nozzle outlet height on the self-cleaning rate. Optimal cleaning parameters were identified to maximize the self-cleaning rate, and the simulation results were validated. The study revealed that the nozzle’s expansion section length, throat diameter, and contraction section length significantly affect the spray width. When the expansion section length was 10 mm, the throat diameter was 8 mm, and the contraction section length was 8 mm, the nozzle achieved the largest jet angle, measuring 50.3 cm. Further analysis indicated that inlet air pressure had the greatest influence on the self-cleaning rate, followed by airflow incident angle and nozzle outlet height. The optimal parameter combination was identified as an inlet air pressure of 0.6 Mpa, an airflow incident angle of 118.25°, and a nozzle outlet height of 2.64 mm, achieving a maximum self-cleaning rate of 99.63%. A one-click cleaning system was designed using an STM32 microcontroller and hardware circuits. Field experiments under optimal parameters demonstrated a self-cleaning rate of 97.68% with a cleaning duration of 10 s per cycle. The findings provide theoretical guidance for the design and optimization of self-cleaning headers for rice seed production. Full article

This paper reviews the field of cascaded metasurfaces, which are advanced optical devices formed by stacking or serially arranging multiple metasurface layers. These structures leverage near-field and far-field electromagnetic (EM) coupling mechanisms to enhance functionalities beyond single-layer metasurfaces. This review comprehensively discusses the physical principles, design methodologies, and applications of cascaded metasurfaces, focusing on both static and dynamic configurations. Near-field-coupled structures create new resonant modes through strong EM interactions, allowing for efficient control of light properties like phase, polarization, and wave propagation. Far-field coupling, achieved through greater interlayer spacing, enables traditional optical methods for design, expanding applications to aberration correction, spectrometers, and retroreflectors. Dynamic configurations include tunable devices that adjust their optical characteristics through mechanical motion, making them valuable for applications in beam steering, varifocal lenses, and holography. This paper concludes with insights into the potential of cascaded metasurfaces to create multifunctional, compact optical systems, setting the stage for future innovations in miniaturized and integrated optical devices. Full article