The Oriental neotenic net-winged beetles attracted attention of biologists due to conspicuous large-bodied females; nevertheless phylogenetic relationships remain contentious and only a few species are known in both the fully metamorphosed males and neotenic females. The phylogenetic analyses and morphology of larvae and adults provide data for investigation of relationships and species delineation. Platrilus Kazantsev, 2009, Platerodriloplesius Wittmer, 1944, and Falsocalochromus Pic, 1942 are synonymized to Platerodrilus Pic, 1921. Platrilus hirtus (Wittmer, 1938) and Pl. crassicornis (Pic, 1923) are transferred to Platerodrilus Pic, 1921. Platerodrilus hoiseni Wong, 1996 is proposed as a junior subjective synonym of Falsocalochromus ruficollis Pic, 1942. Platerodrilus is divided in three species-groups: P. paradoxus, P. major, and P. sinuatus groups defined based on the shape of genitalia and molecular phylogeny. The following species are described: Platerodrilus foliaceus sp. n., P. wongi sp. n. (P. paradoxus group); P. ngi sp. n., P. wittmeri (P. major group), P. ijenensis sp. n., P. luteus sp. n., P. maninjauensis sp. n., P. montanus sp. n., P. palawanensis sp. n., P. ranauensis sp. n., P. sibayakensis sp. n., P. sinabungensis sp. n., P. talamauensis sp. n., and P. tujuhensis sp. n. (P. sinuatus group). P. korinchiana robinsoni Blair, 1928 is elevated to the species rank as P. robinsoni Blair, 1928, stat. n. The conspecific semaphoronts are identified using molecular phylogeny for P. foliaceus sp. n., P. tujuhensis sp. n., P. montanus sp. n., P. maninjauensis sp. n.; additional female larvae are assigned to the species-groups. Diagnostic characters are illustrated and keys are provided for P. paradoxus and P. major groups.

• Klíčová slova
• Oriental Region, molecular phylogeny, morphology, net-winged beetles, taxonomy,
• Publikační typ
• časopisecké články MeSH

This article deals with drilling, the most common and simultaneously most important traditional machining operation, and which is significantly influenced by the properties of the machined material itself. To fully understand this process, both from a theoretical and practical perspective, it is essential to examine the influence of technological and tool-related factors on its various parameters. Based on the evaluation of experimentally obtained data using advanced statistical methods and machine learning decision trees, we present a detailed analysis of the effects of technological factors (fn, vc) and tool-related factors (D, εr, α0, ωr) on variations in torque (Mc) during drilling of two types of engineering steels: carbon steel (C45) and case-hardening steel (16MnCr5). The experimental verification was conducted using CTS20D cemented carbide tools coated with a Triple Cr SHM layer. The analysis revealed a significant influence of the material on torque variation, accounting for a share of 1.430%. The experimental verification confirmed the theoretical assumption that the nominal tool diameter (D) has a key effect (53.552%) on torque variation. The revolution feed (fn) contributes 36.263%, while the tool's point angle (εr) and helix angle (ωr) influence torque by 1.189% and 0.310%, respectively. No significant effect of cutting speed (vc) on torque variation was observed. However, subsequent machine learning analysis revealed the complexity of interdependencies between the input factors and the resulting torque.

• Klíčová slova
• C45 steel (AISI 1045), case-hardened steel 16MnCr5, decision trees, drilling, machine learning, torque,
• Publikační typ
• časopisecké články MeSH

Incremental sheet forming technology is finding increasing application in the production of components in many industries. This article presents the analysis of the formability of 0.68-mm-thick Zn-Cu-Ti alloy sheets during the single-point incremental forming (SPIF) of pyramid-shaped drawpieces. Basic mechanical properties of sheets were determined in a uniaxial tensile test. Formability tests were carried out using the Erichsen and Fukui methods. SPIF tests were carried out under the conditions of variable process parameters: tool diameter (12 and 20 mm), feed rate (500-3000 mm/min), tool rotational speed (250-3000 rpm), and step size (0.1-1.2 mm). The effect of SPIF process parameters on the value of basic mechanical parameters, maximum deviation of the measured wall profile from the ideal profile, limit-forming angle, and surface roughness of pyramid-shaped drawpieces was determined. It was found that increasing the step size resulted in a decrease in the value of the limit-forming angle. Both the step size and the tool rotational speed contribute to the increase of the maximum wall deviation. However, the use of higher feed rates and a larger tool diameter caused its reduction. Higher values of arithmetic mean surface roughness Ra were found for the outer surface of drawpieces. The use of a smaller step size with a larger tool diameter caused a reduction in the Ra value of the drawpiece wall. Based on the obtained results, it can be concluded that the Zn-Cu-Ti alloy demonstrates good suitability for SPIF when proper process parameters and sheet orientation are selected. An appropriate combination of tool diameter, feed rate, step size, and sample orientation can ensure the desired balance between dimensional accuracy, mechanical strength, and surface quality of the formed components.

• Klíčová slova
• SPIF, Zn-Cu-Ti alloy, formability, forming limit angle, incremental sheet forming, surface roughness,
• Publikační typ
• časopisecké články MeSH

Geopolymer composite materials are a viable alternative to conventional construction materials. The research problem of geopolymer composites revolves around the imperative to comprehensively address their synthesis, structural performance, and environmental impact. The derived mathematical model facilitates precisely determining the optimal proportions of two crucial constituents in the geopolymer matrix: silica sand and secondary aluminum by-product. A mathematical model for optimizing the composition of geopolymer composites has been developed based on the integrated use of Markov chains, criterion methods, and an orthogonally compositional plan. The optimal composition of the geopolymer matrix is determined and predicted using a mathematical model. Specifically, the recommended content mixing ratio is as follows: metakaolin at 1000 g, activator at 900 g, silica fume at 1052.826 g, carbon fibre at 10 g, and secondary aluminum by-product at 62.493 g. This study analyzes the influence of different secondary aluminum industry by-products on the geopolymerization process and assesses the mechanical, thermal, and environmental properties of the resulting composites to establish a comprehensive understanding of their structural viability.

• Klíčová slova
• composition, geopolymers, optimization, properties, renewable raw materials, structure, technology,
• Publikační typ
• časopisecké články MeSH

The reactive soldering of silicon-carbide (SiC) ceramics to a Ni-SiC composite was investigated using an Sn-5Sb-3Ti active solder and electron-beam heating at 750 °C, 850 °C and 950 °C. Wettability: The average contact angle decreased from 94 ± 4° (750 °C) to 60 ± 3° (850 °C) and further to 24 ± 2° (950 °C), demonstrating progressively improved spreading of the filler with increasing temperature. Interfacial reactions: Continuous layers of Ni3(Sn,Sb)4 and Ti6(Sn,Sb)5 formed along the Ni-SiC/filler interface, the latter confirming Ti diffusion that activates the wetting of the composite surface. Mechanical performance: Shear-lap tests on three joints per condition yielded 39 ± 6 MPa (750 °C), 27 ± 2 MPa (850 °C) and 36 ± 15 MPa (950 °C). The highest and lowest individual values at 950 °C were 51 MPa and 21 MPa, respectively. These results show that a higher soldering temperature lowers the contact angle and promotes interfacial reaction, but only a moderate improvement in average joint strength is obtained. These findings demonstrate a flux-free route to bond SiC ceramics with Ni-SiC composites, which is highly relevant for next-generation power-electronics modules and other high-temperature applications.

• Klíčová slova
• Ni-SiC composite, SiC ceramics, Sn-Sb-Ti solder, diffusion, electron beam heating, reaction layer, shear strength, soldered joints, wettability,
• Publikační typ
• časopisecké články MeSH

This paper is focused on the modification of commercial resin by using biobased fillers during stereolithography (SLA) 3D printing. This research aims to create a composite material with a matrix made of commercially available photosensitive resin modified with a filler based on secondary raw materials and materials formed as by-products in the processing of biological materials. The research determines the effect of different fillers on the tensile properties and hardness of samples printed using SLA 3D printing, and it also investigates their integrity using SEM analysis. This study aims to evaluate the feasibility of using these fillers for producing 3D-printed parts with SLA technology. The results of this study open up new possibilities for designing modified composite materials based on additive SLA 3D-printing technology using biological fillers. Within the framework of research activities, a positive effect on tensile properties and an improved interfacial interface between the matrix and the filler was demonstrated for several tested fillers. Significant increases in tensile strength of up to 22% occurred in composite systems filled with cotton flakes (CF), miscanthus (MS), walnut (WN), spruce tree (SB), wheat (WT) and eggshells (ES). Significant potential for further research activities and added value was shown by most of the tested bio-fillers. A significant contribution of the current research is the demonstration of the improved mechanical performance of photosensitive resin modified with natural fillers.

• Klíčová slova
• 3D printing, additive manufacturing technologies, biological fillers, composite, mechanical properties, stereolithography (SLA),
• Publikační typ
• časopisecké články MeSH

Severe systemic toxicity and poor targeting efficiency remain major limitations of traditional chemotherapy, emphasising the need for smarter drug delivery systems. Magnetic 2D transition-metal-based nanomaterials offer a promising approach, as they can be designed to combine high drug loading, precise targeting, and controlled release. The key material classes-transition metal dichalcogenides, transition metal carbides/nitrides, transition metal oxides, and metal-organic frameworks-share important physicochemical properties. These include high surface-to-volume ratios, tuneable functionalities, and efficient intracellular uptake. Incorporating magnetic nanoparticles into these 2D structures broadens their potential beyond drug delivery, through enabling multimodal therapeutic strategies such as hyperthermia induction, real-time imaging, and photothermal or photodynamic therapy. This review outlines the potential of magnetic 2D transition-metal-based nanomaterials for biomedical applications by evaluating their therapeutic performance and biological response. In parallel, it offers a critical analysis of how differences in physicochemical properties influence their potential for specific cancer treatment applications, highlighting the most promising uses of each in bionanomedicine.

• Klíčová slova
• hyperthermia, magnetic nanoparticles, magnetic resonance imaging, metal–organic frameworks, photodynamic therapy, photothermal therapy, targeted drug delivery, transition metal carbides/nitrides, transition metal dichalcogenides, transition metal oxides,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Bone diseases lead to an increasing demand for implants to treat long bone defects and for load-bearing applications. Osteoporosis care and accidental injuries are major contributors to this rising need. Our research aims to demonstrate innovative material systems and methods for preparing implants that can be used in regenerative medicine. We hypothesize that by combining titanium alloys (Ti6Al4V) with hydroxyapatite (Hap), we can enhance biocompatibility and tribo-mechanical performance, which are critical for the longevity of Ti-based surgical implants. Additionally, we investigate the application of laser surface treatments to expose the underlying porosity, thereby enhancing cell transport and promoting cell growth. In this study, we investigate the effects of two fabrication techniques-Spark Plasma Sintering (SPS) and powder metallurgy (PM)-on the properties of laser-textured Ti64/Hap biocomposites. Our findings demonstrate that the selected processing route significantly influences the microstructure, tribological performance, and surface properties of these materials. An X-ray diffraction (XRD) analysis corroborates our results from incubation studies in simulated body fluids, highlighting the impact of phase transformations during sintering on the chemical properties of Ti-Hap composites. Additionally, while laser surface texturing was found to slightly increase the friction coefficient, it markedly enhanced the wear resistance, particularly for the PM and SPS Ti + 5%Hap composites.

• Klíčová slova
• SPS, biocomposite, biomaterial, friction, hydroxyapatite, laser surface texturing, titanium alloy,
• Publikační typ
• časopisecké články MeSH

This paper discusses the possibility of determining k-values for active admixtures concerning durability factors such as the depth of penetration of water under pressure and the depth of carbonation of cement mortars with fly ash. The k-value considers the use of active admixtures in concrete when calculating the water/cement ratio and the equivalent amount of binder. Currently, only the effect of the active admixture on the compressive strength of concrete and cement mortars is considered when determining the k-value, but not the effect of the active admixture on durability. To account for the influence of durability factors on the determination of the k-value, the mathematical functions of the property, dependent on the water/cement ratio and the age of the cement mortar, were constructed using regression analysis. From the determined functions, it was then possible to use an optimisation problem to determine the k-value so the difference between the actual measurement and calculated depth of pressure water seepage or carbonation was as small as possible. A high coefficient of determination of 0.9855 was achieved for the pressure water seepage depth function, but the coefficient of determination for the carbonation depth was lower.

• Klíčová slova
• activity index, durability, fly ash, k-value, supplementary cementitious materials,
• Publikační typ
• časopisecké články MeSH

Despite the surge in plasma nitriding research, few reviews thoroughly examine how surface decarburization-occurring both before and during the treatment-affects AISI 4140 and similar steel grades. This review addresses that shortfall by providing an investigation into the decarburization process and its consequences. It compiles essential findings from prior studies, demonstrating instances of decarburization in both plasma-free and plasma-containing environments. Furthermore, this analysis explores strategies to prevent decarburization and assesses its significant impact on the steel's microstructure, hardness, corrosion resistance, and wear properties in surface and near-surface regions. Moreover, this study proposes directions for future research, emphasizing the necessity for a more detailed understanding of the decarburization mechanisms and their influence on the properties of plasma-nitrided steels.

• Klíčová slova
• corrosion, decarburization, friction, low-alloy steel, plasma nitriding, wear,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH