Contact Zone Research Articles

Theoretical modeling of the interfacial shear and contact stresses of 2D braided composite cylinders

AbstractThis research aims to develop an analytical model to predict the interfacial shear stress distribution and contact stress of 2D braided composite cylinders. For this purpose, a tubular structure including a helix braid on a cylindrical mandrel is considered. The interfacial shear stress and axial tensile stress in the composite structure was estimated by applying shear lag assumptions. The contact normal stress and adhesion energy were estimated by applying the assumptions of Johnson‐Kendall‐Robert (JKR) and the Hertzian contact stress theory. The results show that the geometry of the braid and different braid yarn paths have a significant influence on the interfacial shear stress, normal stress in the contact zone, and adhesion energy of composite cylinders. As a novel approach, the proposed model considers the effect of surface roughness in the composite. The results of a parametric study indicated that the composite cylinders with larger braiding angles have lower debonding initiation force. The results also showed that the yarn diameter affected the pullout force in composite cylinders by a large extent.Highlights Normal contact stress and adhesion energy of composite cylinders are affected by the braid yarn path. The 30° composite presented the largest adhesion energy and normal contact stress. Normal tensile stress and interfacial shear stress are influenced by the reinforcement path in the composite. Normal tensile stress and interfacial shear stress in composite cylinders decreased with increased braid angle.

The Formation of In-Betweennees: Iraqi Immigrants' Identity in Heather Raffo's Noura

: Heather Raffo, an Iraqi American playwright, focuses on Iraqi immigrants’ issues and offers a glimpse into their lives by narrating their stories in her plays. Raffo’s drama falls under the category of immigrant literature in which immigrants or their descendants are usually presented. In Noura (2019), Raffo depicts the story of a Christian Iraqi family who fled to the United States to avoid ISIS, a dangerous radical Islamic group. Raffo’s Noura describes the notion of in-betweenness through its characters’ dimensions. Depending on postcolonial theories, this paper analyzes and elucidates the situation of the Iraqi immigrants who fluctuate between the two different cultures of their homeland and their adoptive country. Moreover, this paper highlights how Iraqi immigrants occupy the place of in-betweeness and their in inability to forget their cultural belonging. Depending on Homi Bhabha’s mention of the term ‘in-between’ space to refer to the ‘third Space,’ the Iraqi immigrant characters in Noura designate a transcultural contact zone, hybrid or ‘in-between' space in which they initiate new signs of identity formation. The paper portrays how the cultural encounter causes a sense of confusion among the immigrants and how it affects the construction of their in-between or multicultural identity. Hereby, Noura’s characters develop a new mixed form in which the boundaries between their Iraqi identity and their American identity are blurred and fluid.

Characterizing ground ice content and origin to better understand the seasonal surface dynamics of the Gruben rock glacier and the adjacent Gruben debris-covered glacier (southern Swiss Alps)

Abstract. Over the recent years, there have been focused international efforts to coordinate the development and compilation of rock glacier inventories. Nevertheless, in some contexts, identifying and characterizing rock glaciers can be challenging as complex conditions and interactions, such as glacier–rock-glacier interactions, can yield landforms or landform assemblages that are beyond a straightforward interpretation and classification through ordinary visual means alone. To gain a better understanding of the spatial and temporal complexity of the ongoing processes where glacier–permafrost interactions have occurred, the characterization of the subsurface of the Gruben rock glacier and its adjacent complex contact zone with the then more extended Little Ice Age Gruben glacier is quantitatively assessed using a petrophysical joint inversion (PJI) scheme, based on electrical resistivity (ERT) and refraction seismic (RST) data. Surface dynamics are assessed using both in situ and close-range remote sensing techniques to monitor daily and seasonal displacements and to monitor landform-wide surface changes at high spatial resolution, respectively. Both the geophysical and geodetic surveys allowed two zones to be identified: the rock glacier zone and the complex contact zone where both permafrost and embedded surface ice are present. In the complex contact zone extremely high ice contents (estimated up to 85 %) were found. Widespread supersaturated permafrost conditions were found in the rock glacier zone. Surface displacement rates in this zone are typical of permafrost creep behaviour, with a gradual acceleration in late spring and a gradual deceleration in winter. Moreover, the coherent nature of the rock glacier zone surface deformation contrasts with the back-creeping and slightly chaotic surface deformation of the complex contact zone. Favouring a multi-method approach allowed a detailed representation of the spatial distribution of ground ice content and origin, which enabled us to discriminate glacial from periglacial processes as their spatio-temporal patterns of surface change and geophysical signatures are (mostly) different.

Assessing the Influence of Low Doses of Sucrose on Memory Deficits in Fish Exposed to Common Insecticide Based on Fipronil and Pyriproxyfen

Although pesticides have been a constant concern for decades, in the last ten years, public discussions and scientific research have emphasized their impact on human health and the environment, drawing increased attention to the problems associated with their use. The association of environmental stressors such as pesticides with a sugar-rich diet can contribute to the growing global metabolic disease epidemic through overlapping mechanisms of insulin resistance, inflammation, and metabolic dysregulation. The main aim of this study was to evaluate the behavioral effects of the exposure of Silver crucian carp (Carassius auratus gibelio) to a commercial insecticide formulation containing fipronil, pyriproxyfen, and other additives, as well as sucrose and their mixtures. The behavioral responses in the T-test showed significant abnormalities in the exploratory activity evocative of memory deficits and an increased degree of anxiety in the groups of fish treated with the insecticide formulation and the mixture of the insecticide with sucrose. Aggression, quantified in the mirror-biting test, as biting and the frequency of approaches to the mirror contact zone, was significantly decreased only in the insecticide and sucrose group. All three groups showed behavioral changes reflective of toxicity, but only the combination of the two stress factors, environmental (insecticide) and metabolic (sucrose intake), resulted in pronounced memory alterations.

Brokering war: Afghan interpreters, western soldiers and unequal encounters in crisis

ABSTRACT Crisis scholarship has so far remained inattentive to the uneven entanglements and encounters that operate in what are designated as times or spaces of crisis, such as conflict and war. Indeed, scholarship on crisis suffers from a division between scholars who study the effect of crisis on privileged groups and locations and those who research marginalized communities. This has led the first to approach crisis as an exceptional moment, and the latter to argue that crisis is a semi-permanent condition. The lack of exchange between these two bodies of crisis scholarship has resulted in insufficient consideration of the divergent experiences of the nature and temporalities of crisis by unequally situated actors. This article looks at the contact zone forged by the 2001–2021 Afghanistan war to demonstrate that temporalities of crisis manifest themselves in varied and uneven ways, depending on the positionality of actors. Empirically, this article draws on interviews conducted with western Afghanistan veterans and with Afghan interpreters who worked as linguistic and cultural brokers. By contrasting the experiences of Afghan interpreters with that of the international soldiers who were dependent on their brokerage, I show how differential structures of power and privilege shape what constitutes a crisis, who is touched by it and how and when crisis makes itself felt. Close analysis of the narratives of Afghan interpreters also challenges scholarship which presents brokers as crisis opportunists, who subsequently experience an existential crisis and tragic demise (Distiller and Samuelson 2005, Gaskill 2023). Instead, I develop the argument that brokers’ relationship to crisis can be better understood when the relational and spatio-temporal frames to situate their actions are expanded. I suggest that the cliché of the tragic broker is unsettled when tracing the strategies of Afghan interpreters over time and with attention to the interactions with those for whom they broker.

A snapshot in time: composition of native primary fauna of gall wasps in Spanish contact zones with chestnut trees infested by Dryocosmus kuriphilus.

One of the most prominent problems related to biological invasions is the variation of local species composition, which often leads to ex novo interspecific interactions. Here, we explored and analysed the native species composition of gall inducers and their associated parasitoids and inquilines in Spanish areas invaded by Dryocosmus kuriphilus Yasumatsu 1951 (Hymenoptera: Cynipidae), an invasive pest of chestnut trees. After a quantitative description of these species' assemblages, we analysed through bipartite networks the level of the trophic specialisation of parasitoids and inquilines when considering either the host taxonomic identity, the host plant species or the host gall morphological type. We sampled galls of D. kuriphilus and native species of Cynipidae in different Spanish areas, including those where the exotic parasitoid Torymus sinensis Kamijo 1982 (Hymenoptera: Torymidae) had been released for D. kuriphilus biological control. The results indicate that the native parasitoids recruited by D. kuriphilus come almost exclusively from native communities on Quercus galls, except for one species from Rosa. Galls of D. kuriphilus had the second most diverse species composition; despite this species assemblage arose ex novo in less than a decade. The bipartite networks resulted more specialised when considering host plant taxa than when gall types and the host taxa were accounted. In such trophic webs, there were few parasitoid/inquiline specialist and many generalist species, which agrees with the rapid recruitment by D. kuriphilus. Higher parasitoid species richness in D. kuriphilus galls is likely due to their being a largely unexploited available resource for the native natural enemies of cynipid wasps.

Machining Performance of Ti6Al4V Nano Composites Processed at Al2O3 Nano Particles Mixed Minimum Quantity Lubrication Condition

Introduction: In this research work, an attempt was made to machine Ti6Al4V nano composites utilizing Al2O3 mixed nano fluid at minimum quantity lubrication condition, in which experiments were designed using the L16 orthogonal array, whereas Material Removal Rate, Surface Roughness, machining force and power were recorded as responses. Methods: The nano composites were fabricated using the stir casting technique and the nano particles were synthesized using the sol-gel technique. the microstructure revealed that the homogeneous dispersion of particles with dendric arms. Increased cutting speed and feed lead to more tool wear, which in turn causes a decrease in surface quality and an increase in surface roughness. Results: Larger areas of cut are often the consequence of higher feed rates, which increases the amount of friction between the work piece and the cutting edge. The machining force increases when the feed rate is increased. A higher feed rate produces a large volume of the cut material in a given length of time in addition to having a dynamic impact on the cutting forces. Conclusion: It also results in a corresponding increase in the typical contact stress at the tool chip interface and in the tool chip contact zone.

Contribution of Induced Polarization to the Identification of Mineralization in the Agnibilékrou Department (Eastern Côte d’Ivoire)

The chargeability maps of the Siakakro, N’Guessankro, and Mossikro sites (Agnibilékrou Department, in the east of Côte d’Ivoire) are established from induced polarization (IP) measurements. These maps reveal both polarizable and weakly polarizable structures, with anomalies primarily oriented NE-SW. These orientations, influenced by geological faults, facilitate the migration of hydrothermal fluids and the potential formation of mineral deposits. The zones with high chargeability are mainly located in the center and east of the sites, suggesting the presence of sulfides and representing promising targets for mining exploration. The weakly polarizable areas are associated with sandy-clay formations and non-conductive materials, limiting their mining potential. However, their proximity to faults, especially at N’Guessankro, justifies further investigations to identify potential hidden mineralization. In summary, the zones with high chargeability, particularly at Siakakro, should be prioritized for exploratory drilling. Further exploration, particularly around geological contact zones, is necessary to assess the economic potential of these anomalies.

Research on Propagation Characteristics of Fracture Grouting in Clay Formation

Splitting grouting is a highly effective technique for reinforcing tunnels and underground structures, ensuring their operational stability and facilitating long-term maintenance. It has been widely adopted in the prevention and remediation of geological hazards. However, the theoretical research on the diffusion mechanisms of split grouting lags behind its practical applications. This study addresses several key scientific challenges in understanding the diffusion behavior of split grouting. By integrating experimental design, numerical simulations, and theoretical analysis, we conduct a systematic investigation into the diffusion process and vein morphology of split grouting in both homogeneous and heterogeneous formations. We first employed a self-developed two-dimensional grouting test system to perform diffusion experiments on cohesive strata, focusing on the influence of various factors such as grout density, water/cement ratio, soil consistency, and fracture characteristics. The results provide insights into the diffusion patterns, morphology, soil pressure distribution, and surface uplift behavior of the grout veins. Subsequently, a numerical simulation program, developed in-house, based on the finite element method (FEM) and the volume of fluid (VOF) approach, was employed to model the entire process of fracturing grouting within clay strata. The experimental and numerical results indicate that grout vein diffusion in layered soil follows a Y-shaped pattern with an inclined deflection. In uniform strata, the surface uplift curve displays both symmetrical and asymmetrical “convex” elevations, while in heterogeneous soft and hard strata, the uplift is characterized by distinct “convex” deformations. Finally, based on these findings and the principles of contact mechanics, we analyze the underlying mechanisms. The results suggest that weak contact zones undergo tensile cracking and horizontal deflection prior to the formation of grout veins. Additionally, local stress rotations in the soil can induce tilting and deflection. The theoretical insights derived from this study provide valuable guidance for practical engineering applications.

Morphology and Properties of the Laser-Irradiated Composition “Chrome Coating — Copper Substrate”

Introduction. During pulsed laser processing and modification of the surface of non-ferrous alloys and coatings based on them, several still unresolved issues arise. In particular, the extreme thermal deformation conditions of laser processing are not linked to the peculiarities of structure formation and formation of properties in irradiated “coating — copper substrate” compositions. A metal physical analysis of the possibility and reasons for increasing the adhesion strength of coatings to a metal (copper) substrate during high-speed laser processing is insufficiently substantiated and evidence-based. To make a reasonable choice of technological parameters for the surface hardening mode of non-ferrous alloy products, as well as for obtaining high-quality workable composite layers on their surface, it is necessary to solve the above issues and tasks. The aim of this article is to determine the possibility and conditions for increasing the adhesion strength of a chrome coating to a copper substrate under laser irradiation of the composition.Materials and Methods. Metal physical studies in the work were carried out on samples of non-ferrous alloys of the Cu–Zn system with a chrome electrochemical coating with a thickness of 20 μm. The “copper substrate — chrome coating” composition was irradiated at a Kvant-16 installation with a radiation power density of 70–250 MW/m2. Metallographic structural analysis, scanning probe microscopy, and durometric studies were used in the work.Results. It has been calculated that the dynamic and thermal stresses arising in the laser-irradiated compositions “chrome coating — copper substrate” were about 320 MPa. Metal physical studies revealed that, in extreme thermal deformation conditions of laser treatment, the effect of contact melting was manifested at the boundary of the coating with the copper base. Dynamic recrystallization occurred in the surface layers of the irradiated L62 copper alloy, resulting in the formation of grains with a size of 4.5–5.0 μm on the surface of the alloy with an initial grain size of 25 μm.Discussion and Conclusion. It has been found that the adhesion strength of a chrome coating to a copper alloy substrate increased laser irradiation at a radiation power density of 150 MW/m2. This was due to the formation of a transition region 2–4 μm deep in the contact zone with a structure consisting of sections of mutually insoluble solid solutions based on chromium and copper. Based on the analysis of the copper —chromium state diagram and the model of the temperature field under laser irradiation of the chromium coating, it was suggested that contact melting occurred in the transition zone from the coating to the copper substrate. It was shown that thermostrictive stresses, the calculated quantitative values of which were about 320 MPa, had an initiating effect on the observed processes of structure formation in the laser irradiation zones. It was found that such a level of stresses arising in copper alloys under laser irradiation was sufficient for plastic deformation and dynamic recrystallization of the metal and contributed to the formation of a fine-grained structure (4.5–5.0 μm) with an initial grain size of 25 μm. An analysis of the results of studies of irradiated compositions "coating — copper substrate" allowed us to conclude that they expanded the technological capabilities of the laser method of hardening materials and ensure guaranteed high performance of irradiated products with coatings

Clinal variation in autosomal satellite DNA clusters across a contact zone in Barker Frogs.

Contact zones between genetically divergent lineages offer a unique opportunity to explore gene flow and speciation dynamics. Because satellite DNAs (satDNAs) have high evolutionary rates, they may be useful for comparing related taxa and assessing contact zones. Here, we analyzed the distribution of chromosomal clusters of PcP190 satDNA across a contact zone between two distinct genetic lineages of a Neotropical species complex of frogs. The parental lineages, Physalaemus ephippifer and lineage 1B (L1B), exhibited pronounced divergence in the number of PcP190 clusters. We further expanded the geographic scope of this species complex by including two additional Brazilian localities in previously available cytogenetic and mitochondrial DNA datasets. The contact zone exhibited remarkable variation in the chromosomal distribution of PcP190 clusters among the autosomes; the only fixed autosomal site was found on chromosome 3. The highest numbers of PcP190 clusters were observed in specimens collected at sites near (approximately 320 km from) the distribution of L1B, whereas specimens from Dom Eliseu, which is near (approximately 330 km from) the distribution of P. ephippifer, had the lowest numbers of such clusters. Mitochondrial haplotypes also exhibited geographical variation across sites. Our findings expand the known contact zone of these Physalaemus lineages from 1,500 km2 to over 6,200 km2, demonstrating its extensive area, and emphasize the usefulness of satDNAs in studying contact zones.

Breeding success of the interspecies hybrids: Reduced fertility in the hybridogeneous magpie population (<i>Pica pica</i> × <i>Pica serica</i>, Aves)

Data on the breeding success of hybrids, collected during direct field observations, are principally important for understanding nature of the species isolating factors and future fate of the hybridogeneous populations. In the zone of secondary contact between Eurasian magpie Pica pica and Oriental magpie Pica serica, emerging right now, limited hybridization occurs, what has been shown in our reported data on nuclear single nucleotide polymorphisms (SNP). In the present work, we have analyzed composition of 119 nesting pairs and content of 89 nests in the hybridogeneous population of P. pica leucoptera × P. serica jankowskii in Eastern Mongolia, then in the recent contact zone in Eastern Transbaikalia (South Siberia) and the relatively pure populations of P. p. leucoptera in Central Transbaikalia and P. s. jankowskii in Northeast China. In the hybridogeneous population of Mongolia, significantly increased portion of nonviable clutches with all dead eggs was recorded, as well as a portion of partly dead clutches, compared with the data on the pure population of Central Transbaikalia. The egg mortality was found to be much less dramatic in the population of the Eastern Transbaikalia, where hybridization is less pronounced than in Mongolia. Several possible mechanisms of genetic incompatibilities breaking the reproductive barriers are discussed. The future fate of this magpie contact zone is considered, taking in account selection against hybridization which was revealed in this study. Among possible scenarios, reinforcement of prezygotic isolation may occur, i. e., in the species-specific calls. It is possible that a kind of mosaic hybrid zone with some features of tension zone will appear. Monitoring of the unique situation with the emerging zone of contact and hybridization of two young magpie species is needed, as a necessary addition to genomic studies.

Identification of Deformation Effects While Shaping the Material Surface Relief Due to Burnishing Treatment.

This study analyses a set of phenomena occurring in the burnished surface layer at the initial moment of deformation formation. The aim of the present research was to explain the phenomena occurring in the top layer of the material during burnishing. The presented analyses include selected laboratory and experimental studies of the process involved in forming burnished surface layers. As shown, conducting an analysis of these processes is purposeful and important because the processes affecting final deformations determine the definitive properties of the burnished surface layers. The final results should help to increase the durability and smoothness of the surface of the products obtained. The feasibility of applying computer technology to determine the three-dimensional shape of the deformation zone formation based on measurements of the stereometry of the contact zone of the burnishing tool with the workpiece material is presented. The process of forming a deformation zone was analysed, revealing that irregularities left over from prior treatment are permanently deformed, and a new structure of irregularities is formed on the machined surface, conditioned by the mechanical, geometric, and kinematic factors of the process. Crucial to this are qualities such as the burnishing load (pressure), the type, shape, and dimensions of the tool, the properties of the workpiece material, and the roughness of the surface before burnishing. The analyses presented here include the first stage of processing, in which initial contact is made with the workpiece, and the period of actual processing, during which plastic deformation of the material occurs in three perpendicular directions, leading to the formation of a material wave on the machined surface just in front of the burnishing tool.

Historical and ongoing hybridisation in Southern South American grassland species

Natural hybridisation in plants can impact genetic and morphological diversity, including the emergence of better-adapted new populations and the potential extinction of some lineages involved in this intricate process. Under progressive global warming, species often need to migrate to newly suitable areas, which may be an additional challenge for species with low dispersal ability. Throughout the search for new environments, previously allopatric lineages can come into secondary contact and eventually hybridise if reproductive isolation is incomplete. Here, we focused on two taxa representing the natural herbaceous component of southern South American lowland grasslands. We aimed to evaluate the impact of contact zones and potential hybridisation on the evolutionary relationships and population dynamics. We used single nucleotide polymorphisms and morphological data of multiple individuals from allopatric and contact zones between taxa to shed light on hybridisation patterns and demographic scenarios. Our results indicated that the contact zones impact taxa’s genetic and morphological diversity, and each contact zone had different patterns of genetic diversity and morphology, constituting stable populations that potentially reflect hybridisation events occurring at distinct evolutionary times.

Secondary contact erodes Pleistocene diversification in a wide-ranging freshwater mussel (Quadrula).

The isolated river drainages of eastern North America serve as a natural laboratory to investigate the roles of allopatry and secondary contact in the evolutionary trajectories of recently diverged lineages. Drainage divides facilitate allopatric speciation, but due to their sensitivity to climatic and geomorphological changes, neighboring rivers frequently coalesce, creating recurrent opportunities of isolation and contact throughout the history of aquatic lineages. The freshwater mussel Quadrula quadrula is widely distributed across isolated rivers of eastern North America and possesses high phenotypic and molecular variation across its range. We integrate sequence data from three genomes, including female- and male-inherited mitochondrial markers and thousands of nuclear encoded SNPs with morphology and geography to illuminate the group's divergence history. Across contemporary isolated rivers, we found continuums of molecular and morphological variation, following a pattern of isolation by distance. In contact zones, hybridization was frequent with no apparent fitness consequences, as advanced hybrids were common. Accordingly, we recognize Q. quadrula as a single cohesive species with subspecific variation (Q. quadrula rumphiana). Demographic modeling and divergence dating supported a divergence history characterized by allopatric vicariance followed by secondary contact, likely driven by river rearrangements and Pleistocene glacial cycles. Despite clinal range-wide variation and hybridization in contact zones, the process-based species delimitation tool delimitR, which considers demographic scenarios like secondary contact, supported the delimitation of the maximum number of species tested. As such, when interpreting species delimitation results, we suggest careful consideration of spatial sampling and subsequent geographic patterns of biological variation, particularly for wide-ranging taxa.

Stress transfer, stress shielding, and micro-movement analysis in the implanted femoral bone region with various hip implant stem materials: A finite element approach

This study analyzed stress distribution, stress shielding, and bone-implant micro-movement in different zones of implanted femur bone with hip implant stem composed of Inconel 718, 316 Stainless Steel, Ti6Al7Nb, Ti6Al4V, Ti-12Mo-6Zr-2Fe (TMZF), and Ti-33.6Nb-4Sn (TNS). A 3D model of a well-known hip implant “Summit” was placed in an adult femur bone, and walking, standing, and sitting load instances were simulated as loading conditions using a finite element model (FEM). Increasing hip implant material hardness reduces stress transmission in Gruen zones 1, 2, 5, 6, and 7 of the femur bone but increases it in Gruen zone 3. It also enhances stress holding in the implant body and elevates the Stress Shielding index (SSI) at seven Gruen zones for each load case. TMZF and TNS hip implants in Gruen regions 5 and 7 have negative SSI values under specific load situations. At Gruen zone 3, the SSI value for implanted femur bone increases with hip implant stem material hardness and SSI values variation in implanted femur bone for hip implants of different materials at each loading scenario is within 10 %. However, SSI values do not follow any pattern at Gruen zone 4. Less stiff implants demonstrate increased micro-movement in bone-implant contact zones 1 and 2 due to higher stress transfer. Greater stiffness (Inconel 718) caused increased micro-movement in zone 3. The overall micro-movement (Average and Highest) found an incremental trend for hip implants with higher stiffer to lower materials. The lowest stiff material (TNS) is still in the range of appropriate micro-movement for promoting osteointegration. This study indicates TNS as a superior hip implant stem material due to its enhanced stress distribution, reduced SSI in most Gruen zones on implanted femurs, and acceptable micro-movement over the implant-bone area of contact. Further research is required to minimize SSI, particularly in Gruen zone 3, when using TNS hip implants in implanted femurs.

Epistemic modality and evidentiality in virtual intercultural exchanges between Turkish and Texan users of English

AbstractThis study reports on data from two 6‐week virtual intercultural exchanges (VIEs) between teachers of multilingual learners in K‐12 schools in Türkiye and the United States. Using the data from these asynchronous VIEs, we focus on Turkish world Englishes speakers’ use of epistemic markers and evidentials. We examine how participants from Türkiye use markers of epistemic modality and evidentiality in intercultural encounters and how that use influences their construction of cultural information about Türkiye. Our findings show participants selectively code epistemic modality and evidentiality to indicate (their proximity to) the source of cultural information, avoid potential misunderstanding, and claim responsibility for the factuality of the information shared (or not). Our study contributes to understanding how world Englishes and Intercultural Communication intersect in multilingual contact zones that transcend borders―both real and imagined―between cultures, languages, and nations.

Lenition of voiced stops in Kurdish

Abstract Contemporary Kurdish variety groups exhibit considerable variation with respect to the lenition of voiced stops. This paper presents a first systematic overview of lenition across major varieties of Kurdish, drawing on published data and a recent questionnaire developed for studying phonological variation within Kurdish. Following recent studies on lenition, a distinction is made between lenition as a process related to earlier stages of language and lenition as a synchronically active process. Analysing diachronic sound changes in Kurdish as well as the synchronic lenition phenomena in its dialects, we conclude that while at earlier stages, Kurdish varieties favoured the lenition of voiced stops across different phonological environments, synchronically, lenition of voiced stops tends to be phonologically active only in the southernmost dialects of Central Kurdish and neighbouring Southern Kurdish and Gorani dialects, and with a limited extent, in the westernmost outliers of Northern Kurdish. It is argued that the synchronic lenition in the Gorani contact zone arose through innovation in Gorani and spread to Kurdish through substratum interference or originated in diffusion from Southern Kurdish.

CFD-FEM Analysis for Functionality Prediction of Multi-Gear Pumps

A comprehensive model for evaluating the functionality of a multi-gear pump has been developed. The integrated model for assessing the functionality of a multi-gear pump contains a computational fluid dynamics analysis (CFD) model combined with a finite element method (FEM)-based strength model. Two submodels were linked: a CFD submodel to evaluate the internal pressure distribution of the pump and a structural FEM submodel to calculate the stresses and structural displacements of the pump due to fluid pressure. Finite element analysis in SolidWorks 2016 was used to evaluate the strength of the gear joints of the pump gears. As the pressure of the working fluid increases from 6 to 20 MPa, a linear increase in Mises stresses is observed. At the shaft, these stresses increase to 226.2 MPa, and at the tooth mouths, they reach a maximum value of 205.5 MPa. With the increase in torque on the drive shaft from 100 to 500 N·m, there is a significant increase in Mises stresses localized in the contact zones of the shaft with the drive gear. Analysis of the data obtained showed that the displacements caused by the pressure of the working fluid are insignificant compared to the displacements arising under the action of torque. With increasing pressure and torque, there is a tendency to decrease the safety factor, which indicates a decrease in the safety factor of the design of the multi-gear pump. The safety factor is not provided at a torque of 400–500 N·m. The simulation results are confirmed by correlation analysis. The average approximation error is 5–7%.

DISPERSED POLYOXADIAZOLE MODIFIER FOR ANTIFRICTION PHENOLFORMALDEHYDE TEXTOLITES

Antifriction polymer composite materials based on phenol-formaldehyde resole binders, reinforced with textile-combined polyoxadiazole and cellulose fibers, have high tribological and physical-mechanical properties. This opens up prospects for solving a wide range of problems in the design of friction units of machines and mechanisms with an extended service life. However, when processing these materials into finished products, technological difficulties arise that limit their use. The use of a dispersed modifier simplifies the technology for producing polymer composite materials. By grinding polyoxadiazole fibers in a ball vibration mill, a new type of anti-friction dispersed modifier of phenol-formaldehyde binders was obtained. In accordance with the data of diffractometric analysis, when grinding polyoxadiazole fiber, there is a slight decrease in its crystallinity, which has virtually no effect on the physical and mechanical properties of the material. The resulting dispersed modifier is a mixture of short fragments of deformed polyoxadiazole filaments and flaky polyoxadiazole particles of irregular shape, the size of which reaches 200-250 µm. X-ray photoelectron spectroscopy data indicate an increase in the nitrogen content in the resulting powdered product compared to the original polyoxadiazole fiber. The introduction of a powdered polyoxadiazole modifier into a phenol-formaldehyde binder for cotton textolites ensured the production of self-lubricating wear-resistant antifriction polymer composite materials with good tribological properties. A decrease in the coefficient of friction, wear and temperature in the friction contact zone is observed (under conditions of dry friction on a steel counterbody). The samples of the studied materials with a small content of polyoxadiazole modifier (5% wt.) in the phenol-formaldehyde binder have the best tribological characteristics. The properties of the resulting materials are due to polymer composite materials reinforced with a fabric combination of fibers, polyoxadiazole and cellulose. For citation: Panova M.O., Buyaev D.I., Shaposhnikova V.V. Dispersed polyoxadiazole modifier for antifriction phenolformaldehyde textolites. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 11. P. 79-85. DOI: 10.6060/ivkkt.20246711.7051.