Search Results (2,194)

The technology of 3D printing has become one of the most effective methods of creating various parts, such as those used for fast prototyping. The most important aspect of 3D printing is the selection and application of the appropriate material, also known as filament. The current review concerns mainly the description of the mechanical and physical properties of the different filaments and the possibilities of improving those properties. The review begins with a short description of the development of 3D printing technology. Next, the basic characteristics of thermoplastics used in the fused filament fabrication (FFF) are discussed, namely polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), and polyethylene terephthalate glycol (PETG). According to modern con-cepts, the printed parts can be reinforced with the use of different kinds of fibers, namely synthetic fibers (carbon, glass, aramid) or natural fibers (wood, flax, hemp, jute). Thus, the impact of such a reinforcement on the performance of FFF composites is also presented. The current review, unlike other works, primarily addresses the problem of the aging of parts made from the thermoplastics above. Environmental conditions, including UV radiation, can drastically reduce the physical and mechanical properties of printed elements. Moreover, the current review contains a detailed discussion about the influence of the different fibers on the final mechanical properties of the printed elements. Generally, the synthetic fibers improve the mechanical performance, with documented increases in tensile modulus reaching, for instance, 700% for carbon-fiber-reinforced ABS or over 15-fold for continuous aramid composites, enabling their use in functional, load-bearing components. In contrast, the natural ones could even decrease the stiffness and strength (e.g., wood–plastic composites), or, as in the case of flax, significantly increase stiffness (by 88–121%) while offering a sustainable, lightweight alternative for non-structural applications. Full article

This paper constructs a numerical simulation model for the fire and fire-fighting system of an all-electric vehicle ro-ro passenger ship to study the influence of fire characteristics and fire-fighting system layout parameters on the fire-extinguishing system. The simulation results show that the fire can spread to the upper deck within 52 s, and the smoke will fill the main deck within 57 s. The study found that the battery capacity has a super-linear relationship with the fire hazard, and the fire thermal spread radius of a 240 Ah battery can reach 3.5 m. The high-expansion foam system has a low applicability in quickly suppressing battery fires due to its response delay and limited cooling capacity for deep-seated fires; the fire-extinguishing efficiency of fine water mist has spatial dependence: 800 µm droplets achieve effective cooling in the core area of the fire source with stronger penetrating power, while 200 µm droplets show better environmental cooling ability in the surrounding area; at the same time, the large-angle nozzles with an angle of 80–120° have a wider coverage range and perform better in overall temperature control and smoke containment than small-angle nozzles. The study also verified the effectiveness of fire curtains in forming fire compartments through physical isolation, which can reduce the heat radiation range by approximately 3 m. This research provides an innovative solution for improving the fire safety level of transporting all-electric vehicles on ro-ro passenger ships. Full article

Background: Gross tumor volume (GTV) segmentation of Nasopharyngeal Carcinoma (NPC) crucially determines the precision of image-guided radiation therapy (IGRT) for NPC. Compared to other cancers, the clinical delineation of NPC is especially challenging due to its capricious infiltration of the adjacent rich tissues and bones, and it routinely requires multimodal information from CT and MRI series to identify its ambiguous tumor boundary. However, the conventional deep learning-based multimodal segmentation method suffers from limited prediction accuracy and frequently performs as well as or worse than single-modality segmentation models. The limited multimodal prediction performance indicates defective information extraction and integration from the input channels. This study aims to develop a 3D Gaussian-prompted Diffusion Model (3DG-PDM) for more clinically targeted information extraction and effective multimodal information integration, thereby facilitating more accurate and clinically interpretable GTV segmentation for NPC. Methods: We propose a 3D-Gaussian-Prompted Diffusion Model (3DGS-PDM) that operates NPC tumor contouring in multimodal clinical priors through a guided stepwise process. The proposed model contains two modules: a Gaussian Initialization Module that utilizes a 3D-Gaussian-Splatting technique to distill 3D-Gaussian representations based on clinical priors from CT, MRI-t2 and MRI-t1-contract-enhanced-fat-suppression (MRI-t1-cefs), respectively, and a Diffusion Segmentation Module that generates tumor segmentation step-by-step from the fused 3D-Gaussians prompts. We retrospectively collected data on 600 NPC patients from four hospitals through paired CT, MRI series and clinical GTV annotations, and divided that dataset into 480 training volumes and 120 testing volumes. Results: Our proposed method can achieve a mean dice similarity cofficient (DSC) of 84.29 ± 7.33, a mean average symmetric surface distance (ASSD) of 1.31 ± 0.63, and a 95th percentile of Hausdorff (HD₉₅) of 4.76 ± 1.98 on primary NPC tumor (GTVp) segmentation, and a DSC of 79.25 ± 10.01, an ASSD of 1.19 ± 0.72 and an HD₉₅ of 4.76 ± 1.71 on metastasis NPC tumor (GTVnd) segmentation. Comparative experiments further demonstrate that our method can significantly improve the multimodal segmentation performance on NPC tumors, with superior advantages over five other state-of-the-art comparative methods. Visual evaluation on the segmentation prediction process and a three-step ablation study on input channels further demonstrate the interpretability of our proposed method. Conclusions: This study proposes a performant and interpretable multimodal segmentation method for GTV of NPC, contributing greatly to precision improvement for NPC therapy treatment. Full article

As core components of terahertz (THz) radiation sources, photoconductive antennas (PCAs) suffer from performance limitations due to inefficient carrier generation/transport and space-charge shielding effects. This study first introduced cylindrical Au nanoarray structures within the electrode gaps of photoconductive antennas to enhance radiation performance. A combination of the finite element method solver and COMSOL Multiphysics was implemented to refine the model by accounting for the shielding field, which is often neglected in the calculations. Guided by the theoretical and simulation model, the generated current, THz radiation power and the shielding field were comparatively studied in the plasmonic nanoarray PCA and traditional PCA without the plasmonic nanoarray structure. The results demonstrate that emitters with the cylindrical nanoarray structures achieve a radiation power 3.81 times higher than that of the traditional structure, along with a 50% broader bandwidth. Further optimization of photogenerated carrier distribution through engineered metallic nanoarray structures reveals that plasmonic photoconductive THz emitters with triangular nanoarrays reduce the space-charge shielding field by 28.7% compared to the cylindrical structures while enhancing the radiation field intensity by a factor of 1.21. This work presents an effective approach to designing high-performance photoconductive THz emitters, holding significant theoretical and practical significance. Full article

Multiple-Input Multiple-Output (MIMO) antenna systems are key to improving wireless channel capacity and reliability. Yet, their inherent need for compact configurations introduces a significant challenge: electromagnetic coupling between closely placed radiating elements. This undesirable phenomenon diminishes efficiency, increases signal correlation, and compromises electromagnetic isolation. To mitigate these issues, researchers have proposed diverse isolation techniques, such as Defected Ground Structures (DGS), metamaterials, fractal geometries, and neutralization lines. These techniques are crucial for boosting isolation and facilitating antenna miniaturization without compromising overall electromagnetic performance, making them indispensable for modern compact communication systems. This article provides a comprehensive review of these techniques, dissecting their fundamental operating principles and analyzing the electromagnetic isolation results previously documented in the literature. Furthermore, experimental findings derived from the fabrication and characterization of prototypes, aiming to confirm the practical efficacy of these isolation methods, are presented. Full article

This study investigates a Solar Air Heating Façade (SAHF), architecturally enhanced through the integration of granular translucent Silica-Aerogel into multi-wall polycarbonate (PC) panels and the implementation of coated timber lamellas. The novelty of this work lies in the combined evaluation of thermal resistance and solar transmission properties of façade-integrated components, aiming to improve both energy efficiency and architectural integration. Two experimental campaigns were conducted: (i) thermal transmittance tests to determine the U-value of PC panels with and without Silica-Aerogel infill, and (ii) solar transmission measurements under controlled artificial solar radiation to evaluate the optical performance of various lamella configurations and coatings. Results show that the incorporation of Silica-Aerogel reduced the U-value by 41.8%, achieving a minimum of 1.19 W/m² K with the 20 mm thick PC panel, while decreasing the solar transmission of 43–53% depending on the incidence angle. The integration of reflective aluminum-coated timber lamella demonstrated promising results, enabling effective management of solar radiation. These findings highlight the potential of façade systems that combine high-performance insulation with visually integrated shading elements. Full article

Given that building energy consumption accounts for a significant portion of total energy consumption, passive building technologies have demonstrated tremendous potential in addressing energy crises and the greenhouse effect. As a passive building technology, the Trombe wall (TW) can utilize solar energy to enhance building energy efficiency. However, due to their reliance on direct solar radiation patterns and limited thermal inertia characteristics, traditional TW systems exhibit inherent efficiency limitations. By integrating phase change materials (PCMs), TW systems can achieve high thermal storage performance and temperature control flexibility within a narrow temperature gradient range. By integrating functional materials, PCM-TW systems can be made multifunctional (e.g., through thermal catalysts for air purification). This has significant engineering implications. Therefore, this paper systematically reviews the development timeline of TWs, focusing on the evolution of PCM-TW technology and its performance. Based on this, the paper particularly emphasizes the roles of three key operational parameters: structural characteristics, thermophysical material design, and operational management. Importantly, through comparative analysis of existing systems, this paper identifies the shortcomings of current PCM-TW systems and proposes future improvement directions based on the review results. Full article

Current photoconductive antennas (PCAs) fail to maximize the use of photogenerated carriers at the electrode edges. To address this limitation, we designed a novel PCA structure featuring a ring electrode and a disc electrode. The positive and negative electrodes are positioned on opposite sides of the substrate, and eight metal tips are incorporated into the ring electrode to enhance performance. The PCA-1 photoconductive antenna with both positive and negative electrodes on the same side of the substrate generates a peak current of about 18 μA, whereas under the same simulation parameters, the peak current generated by the PCA-1 and the conventional interdigitated photoconductive antenna are equal, and the PCA-2 photoconductive antenna with positive and negative electrodes on the top and bottom sides of the substrate generates a current nearly 1.45 times higher than that generated by the PCA-1. The PCA-3 photoconductive antenna with positive and negative electrodes on the top and bottom of the substrate and eight additional metal tips on the circular electrodes is nearly twice the peak current generated by the PCA-1, and the terahertz radiated power of the designed PCA-3 is four times that of the PCA-1, which suggests that the designed THz-PCA can improve the optical-terahertz conversion efficiency, and it has a great prospect of popularizing terahertz technology based on the THz-PCA. Full article

Microwave Radiation Imagers (MWRIs) onboard the FY-3B, FY-3C, and FY-3D satellites are the primary sensors for sea surface temperature (SST) observation. Benefiting from the resolution of several key calibration issues in brightness temperature products, MWRI SST records spanning more than a decade have been reprocessed. In this study, these reprocessed SST products are evaluated using direct comparison and the extended triple collocation (ETC) method, along with additional error analyses. Compared with iQuam SST, the reprocessed MWRI SST products from the three satellites show total root mean square errors (RMSEs) of 0.80–0.82 °C and total biases of −0.12 °C to 0.00 °C. ETC analyses based on MWRI, ERA5, and Argo SSTs indicate random errors of 0.76–0.78 °C. Furthermore, the reprocessed MWRI SST products demonstrate temporal stability and exhibit minimal crosstalk effects from sea surface wind speed, columnar water vapor, and columnar cloud liquid water in SST retrievals. Compared with previous versions, the reprocessed products show significant improvements, with consistent performance across FY-3B, FY-3C, and FY-3D. However, differences in SST observations due to the varying local times of the ascending nodes among the three satellites should be corrected in practical applications. Full article

Hylocereus species are promising for enhancing fruit productivity in arid regions, but high solar radiation often leads to yield loss. This study aimed to evaluate the short-term impact of different shading levels on the physiological performance, productivity, and post-harvest quality of Hylocereus costaricensis under semi-arid conditions. Plants were grown in the field under two shade levels, i.e., 35 and 50% and their performances were compared to plants under control, i.e., 0% of shade or full sunlight. The nighttime CO₂ assimilation and productivity increased significantly by 310.5 and 114.6% and 34.3 and 50.14% for plants under 35 and 50% of shade, respectively, compared to the control. A Principal Component Analysis (PCA) revealed that shade enhanced skin betalain (BETS) and phenolic content (PETP), whereas non-shaded plants expressed traits more closely associated with plant and fruit photoprotective pigment synthesis, i.e., total carotenoids and yellow flavonoids, respectively, along with total sugar accumulation, underscoring the significant impact of shading on both metabolic activity and overall agronomic outcomes. Shading within the 35% to 50% range is effective to cope with high solar radiation by improving photosynthetic capacity, productivity, and post-harvest quality, especially regarding the accumulation of pigments such as betalains, indicating that shade as an agro-technique is a valuable approach for the cultivation of Hylocereus species in dryland regions. Full article

In this paper, we present a water mist dehazing network to improve the accuracy of radiation temperature measurements of the billet surface in the secondary cooling zone of continuous casting. First, we develop a billet radiation attenuation model that accounts for the wavelength-dependent attenuation coefficient of water mist in the secondary cooling zone. Using this model and the corresponding dataset, the water mist transmittance is calculated. Furthermore, the water mist dehazing network—which is distinct from conventional dehazing networks designed for natural environments—comprises three key components: water mist feature extraction based on a combined Unet and Transformer structure; fusion of prior water mist transmittance data using an attention mechanism; and composite transmittance estimation via a multi-path dense network. The experimental results demonstrate that the proposed network effectively reduces water mist’s interference with billet surface temperature measurements in both the spatial and temporal dimensions. Compared with the standalone Unet and Unet + Transformer network architectures, the proposed network achieves a significantly improved dehazing performance, thus verifying its practical value and reliability for billet surface temperature measurement tasks. Full article

Smart Electromagnetic Skins (SESs) provide a cost-effective and efficient alternative to increasing the number of Base Stations (BSs) for improving the performance of next-generation communication networks and contribute to the implementation of Smart Radio Environments (SREs). SESs generalize the concept of ReflectArrays (RAs) because they redirect the incident field in a non-specular direction. However, as the difference between the pointing and specular directions increases, specular and parasitic effects arise, which affect the radiation pattern, energy efficiency, and pointing direction. The techniques generally adopted for SES design, using homogenized-effective-medium model, are unable to overcome this drawback efficiently. Starting with initial SES design based on the Phase-Gradient (PG) approach, the suppression of the higher order modes has been achieved by incorporating volumetric charge-current distributions when defining radiation modes, using theory of electromagnetic-multipoles. This approach reveals formation of anapoles in single-layer SESs/RAs for first time ever. By combining both local and non-local approaches in super-cell design, higher-order symmetry-breaking of unit cells is utilized to exploit anapole formation as a parasitic mode suppression method. Numerical analysis of SESs with increasing size confirms the effectiveness of the proposed approach, which allows for a drastic reduction in parasitic modes while leaving the performance of the desired mode unchanged. Adopting a multipole perspective enhances the understanding of SES radiation mechanisms, unlocks their unexploited performance potential, and opens new opportunities for multifunctional design. Full article

In this study, a 38 GHz millimeter wave Yagi antenna was designed and fabricated on a chip using a 0.18 μm CMOS process. The radiation performance of the antenna is improved by using a Yagi antenna with end-fire. The proposed antenna chip measures the reflection coefficient at less than −10 dB over a bandwidth range from 36.6 to 39.8 GHz, covering the 5G n260 band. The CMOS antenna chip has a size of $1.2\times 1.2{ \mathrm{m}\mathrm{m}}^2$. This study also proposes a solution for the easy measurement of the radiation characteristics to verify the performance in millimeter wave applications. For this purpose, the chip antenna uses bonding wire technology and is verified in a millimeter wave test system. Finally, the simulation and measurement results of the antenna pattern of the bondline technique yield similar radiation patterns. Full article

Thermal cameras are known for their ability to overcome lighting constraints and provide reliable thermal radiation images. This capability facilitates methods for depth and ego-motion estimation, enabling efficient learning of poses and scene structures under all-day conditions. However, the existing studies on depth prediction for thermal images are limited. In practical applications, thermal cameras capture sequential frames. Unfortunately, the potential of this multi-frame aspect is underutilized by the previous methods, resulting in limitations on the depth prediction accuracy of thermal videos. To leverage the multi-frame advantages of thermal videos and to improve the accuracy of monocular depth estimation from thermal images, we propose a framework for self-supervised depth and ego-motion learning from multi-frame thermal images. We construct a multi-view stereo (MVS) cost volume from temporally adjacent thermal frames. The construction process is adjusted based on the estimated pose, which serves as a motion hint. To stabilize the motion hint and improve pose estimation accuracy, we design a motion enhancement module that utilizes self-generated poses for additional supervisory signals. Additionally, we introduce RGB images in the training phase to form a multi-spectral loss, thereby augmenting the performance of the thermal model. The experimental results, conducted on a public dataset, demonstrate the proposed method’s accurate estimation of depth and ego-motion across varying light conditions, surpassing the performance of the self-supervised baseline. Full article

Background: This study characterizes the current representation of sociodemographic groups within Canadian radiation oncology training programs and trainees’ lived experiences. Methods: A 59-item ethics-approved, bilingual survey assessed sociodemographics, training perceptions, mentorship, discrimination/harassment experienced, and open-ended questions. Electronic surveys were distributed to all Canadian radiation oncology residents/fellows. Descriptive statistics summarized survey responses. Categorical groups were compared using chi-squared/Fisher’s exact tests. Thematic analysis was performed on open-ended responses. Results: Between July and December 2023, 98 of 177 (56%) trainees participated: 70% were residents, 52% identified as male, 62% as a racialized minority, and 10% as a sexual minority. Most respondents reported training program satisfaction (83%) and a respectful workplace culture (69%); however, discrimination during training was reported by 38%. Less than half (45%) felt comfortable reporting discrimination/harassment within their workplace. Women were more likely to feel under-represented in-training (46% vs. 13%, p = 0.001) and perceived more discrimination events (64% vs. 19%, p < 0.001). Three themes emerged as follows: importance of offering EDI education, ensuring pathways for reporting learner mistreatment, and creating appropriately diverse selection committees. Conclusions: Although most Canadian radiation oncology trainees reported satisfaction and a respectful culture, key differences between groups were observed. Targeted strategies and stronger institutional policies to improve representation and reduce rates of discrimination/harassment are needed. Full article