Subsequent Operations Research Articles

Outcomes of Surgical Treatment for Multiligament Knee Injuries in a Cohort Including Competitive Athletes With Long-Term Follow-Up.

There is a paucity of outcomes data on surgical reconstruction for multiligament knee injury (MLKI) in the orthopaedic literature. To examine functional and return-to-sports (RTS) outcomes and revision rates after single-stage reconstruction for MLKIs in a cohort containing a large proportion of competitive athletes over a 20-year period. Case series; Level of evidence, 4. We identified all patients at our institution who underwent surgical reconstruction for an anterior cruciate ligament (ACL) or bicruciate (ACL-posterior cruciate ligament) MLKI between 2001 and 2020 and had ≥2 years of postoperative outcome data. Patient-reported outcomes were evaluated using the International Knee Documentation Committee (IKDC) form, a surgical satisfaction survey, and questions about subsequent knee surgery and RTS administered via telephone. Summary statistics for all outcomes data were calculated, and predictors of IKDC scores at follow-up were examined using univariable linear regression. Out of 151 patients eligible for this study, outcomes data were collected in 119 patients (79%). The mean follow-up time was 8.3 ± 4.4 years, and the mean IKDC score at follow-up was 79 ± 17. A total of 83 competitive athletes were included; 62 of these athletes attempted to return to preinjury sport. Among the 62 who attempted RTS, 50 (81%) were successful, and 12 were unable to return due to limitations from their surgery. At follow-up, 112 of the overall cohort of 119 patients (94%) were either satisfied or very satisfied with their surgical outcome, and 91% stated the surgery met or exceeded their expectations. In addition, 24% had subsequent ipsilateral knee operations after their index multiligament knee reconstruction. Older age at surgery and female sex were associated with worse IKDC scores at follow-up. Despite the severity of the injuries in our cohort, we found high levels of patient-reported function and a high rate of successful RTS in the competitive athletes. Older age and female sex were associated with worse patient-reported knee function at follow-up.

Sensor Fault Detection and Classification Using Multi-Step-Ahead Prediction with an Long Short-Term Memoery (LSTM) Autoencoder

The Internet of Things (IoT) is witnessing a surge in sensor-equipped devices. The data generated by these IoT devices serve as a critical foundation for informed decision-making, real-time insights, and innovative solutions across various applications in everyday life. However, data reliability is often compromised due to the vulnerability of sensors to faults arising from harsh operational conditions that can adversely affect the subsequent operations that depend on the collected data. Hence, the identification of anomalies within sensor-derived data holds significant importance in the IoT context. This article proposes a sensor fault detection method using a Long Short-Term Memory autoencoder (LSTM-AE). The AE, trained on normal sensor data, predicts a 20-step window, generating three statistical features via SHapley Additive exPlanations from the estimated steps. These features aid in determining potential faults in the predicted steps using a machine learning classifier. A secondary classifier identifies the type of fault in the sensor signal. Experimentation on two sensor datasets showcases the method’s functionality, achieving fault detection accuracies of approximately 93% and 97%. It is possible to attain a perfect fault classification performance by slightly modifying the feature calculation approach. In a univariate prediction scenario, our proposed approach demonstrates good fault detection and classification performance.

Image encryption algorithm based on multiple chaotic systems and improved Joseph block scrambling

Abstract With the rapid development of digital information technology, images are increasingly used in various fields. To ensure the security of image data, prevent unauthorized tampering and leakage, maintain personal privacy, and protect intellectual property rights, this study proposes an innovative color image encryption algorithm. Initially, the Mersenne Twister algorithm is utilized to generate high-quality pseudo-random numbers, establishing a robust basis for subsequent operations. Subsequently, two distinct chaotic systems, the autonomous non-Hamiltonian chaotic system and the tent-logistic-cosine chaotic mapping, are employed to produce chaotic random sequences. These chaotic sequences are used to control the encoding and decoding process of the DNA, effectively scrambling the image pixels. Furthermore, the complexity of the encryption process is enhanced through improved Joseph block scrambling. Thorough experimental verification, research, and analysis, the average value of the information entropy test data reaches as high as 7.999. Additionally, the average value of the number of pixels change rate (NPCR) test data is 99.6101%, which closely approaches the ideal value of 99.6094%. This algorithm not only guarantees image quality but also substantially raises the difficulty of decryption.

Study on nonuniform tip clearance in mixed flow compressor

In compressed air energy storage system, the inevitable axial vibration during the frequent start-stop of compressor leads to circumferential nonuniform tip clearance formation, which significantly impacts compressor performance. This paper utilizes numerical simulation to study the overall performance and internal unsteady flow field of a mixed flow compressor with 4 different eccentricities and compares them with the original model. The results indicate that the eccentricity of blade tip clearance has little effect on pressure ratio and isentropic efficiency of the mixed flow compressor, but has an important impact on its stall margin. Specifically, when the eccentricity is 70 % of the blade tip clearance, the compressor stall margin is reduced by 5.96 %. The circumferential distribution of tip relative leakage aligns with the circumferential variation of tip clearance height. The average tip relative leakage increases gradually with the increase of eccentricity, and its growth rate also increases gradually with the increase of eccentricity. There are two peaks and valleys in the radial force distribution of a single blade, while the axial force of a single blade is consistent with the change in circumferential tip clearance height. These findings can provide valuable guidance for subsequent compressor design and operation.

Evolution of pre-damaged ITER grade plasma facing components under WEST plasma exposure: smoothing and tungsten sources

The evaluation of the impact of plasma-facing units (PFUs) damage on subsequent plasma operation is an important issue for ITER. This is one of the topic addressed by the operation of dedicated PFUs in WEST. From the start of WEST in 2017, few ITER grade divertor PFUs were tested in the lower divertor for short plasma exposure (experimental campaigns C1–C5). A PFU is an assembly of tungsten blocks on CuCrZr tube via pure copper interlayer. Since 2022, WEST operates with a lower divertor fully equipped with ITER grade PFUs (experimental campaign C6–C7) with long duration plasma exposure capabilities. To test the ageing of the ITER-grade PFUs on an accelerated basis, well controlled damage was implemented on purpose with electron beam loading on the plasma facing surface of two different PFUs (pre-damage#1 and #2 featuring different level of damage). Damage tackled in this study is induced by the loading with numerous transient heat loading events to mimic the ELM impact on the ITER grade PFU. This paper presents the damage before and after WEST plasma exposure and shows the tungsten sources and temperature of the block measured during the operation. On damaged area, surface roughening is heterogeneous. With WEST campaigns (C3, C4 and C7) respectively ended in (2018, 2019 and 2023) a global smoothing of the pre-damaged surfaces, in particular those located in the high loaded erosion area, is observed. No evolution of the crack is observed in the electron beam loaded area, while new cracking are observed on non pre-damaged area on the tungsten top surfaces in highly loaded areas (outer strike point) after significant plasma duration and cumulated energy (first observation in C4 and tends to be confirmed with preliminary observations after the C7 campaign). Smoothing is less pronounced after the 2018 campaign, which may be due to the related short plasma duration. The surface smoothing of blocks also depends on their poloidal position. For PFU which has no shaping, toroidal positioning within a block has no influence on the surface smoothing. After 2019 and 2023 campaigns, equivalent relative smoothing is obtained (between 19 and 32%). For the explored plasma conditions, damage has no influence on the maximum brightness of W.

Research on metal surface specular removal algorithm based on unsupervised learning

The highlights on the surface of metal materials can seriously destroy the continuity of the image, produce certain false edges, and cause the texture details in the highlights area to weaken or even disappear, which interferes with the subsequent operations such as surface region segmentation and defect detection. Aiming at the low efficiency, high loss, easy distortion and difficult calibration of metal highlight data, an unsupervised perceptual enhancement network model based on the convolutional neural network (CNN) is proposed. Firstly, the method of generating antagonism is used to generate a large number of metal images with high-light feature information, which is used to increase the number of high-light metal image data sets in the training set. Secondly, a detail enhance model(DEM) and a color enhance model(CEM) are introduced into the context aggregation network to improve the feature detail retention rate in the low resolution weight graphs. Finally, the multi-scale structural similarity function is used to replace the original structural similarity function to solve the insensitive detail when the image size is too large. Experiments show that comparing with other multi-exposure image fusion models, the present model can improve the evaluation index of mutual information and average gradient of fused images by about 10%, and can retain more texture feature information.

Assessment of hydrogen-induced material degradation using electromagnetic testing technology

The production, transport and use of green hydrogen are key issues for the efficient use of renewable energies. Hydrogen is able to compensate for both temporal and spatial fluctuations that naturally occur in the production and consumption of renewable energies, regardless of weather conditions, and thus can act as an efficient energy storage medium. The use of existing gas pipelines in a dynamically operated pipeline network offers particular potential for the transport of green hydrogen with regard to sustainability, resource conservation and economic efficiency. In this context, dynamic means that pressure fluctuations are permissible to a certain extent in the operation of gas pipelines. However, a hydrogen-induced degradation of the mechanical material properties can lead to brittle fracture and manifest itself in sudden material failure. Such failure must be excluded in safetyrelevant infrastructures. Hence, it would be beneficial to detect fatigued or degraded areas in the material at an early stage, especially in the context of possible increased crack growth rates associated with hydrogen embrittlement. In addition to fatigue data, which are crucial in the calculation and design of gas pipelines, non-destructive inspections are particularly important in subsequent operation to monitor the current condition of the pipelines. Non-destructive testing focuses primarily on defects such as cracks that have already developed or on visible corrosion attack. The fatigue condition, i.e., the probability of crack initiation and crack propagation is hard to evaluate. However, this can be addressed by an electromagnetic test method capable of evaluating the current state of the material. In the presented paper, an electromagnetic test method is presented, which is able to detect and evaluate hydrogen-induced material degradation. In subsequent stages, such a method can then be used as an electromagnetic monitoring system in fatigue tests, thus providing new potential for condition assessment.

Integrating reliability analysis into MBSE for FPGA-based safety critical I&C system design in nuclear power plants

Abstract With the widespread application of Field Programmable Gate Array (FPGA) technology in the instrumentation and control (I&C) systems of nuclear power plants (NPPs), its design reliability has become the key to ensuring the subsequent safe operation of NPPs. However, the traditional document-based design method is no longer sufficient to meet the current design needs of complex systems, and there is a lack of research related to the reliability and security analysis of FPGA-based systems. Therefore, the overall goal of this study is to integrate reliability analysis into the model-based systems engineering (MBSE)-based design of FPGA-based I&C systems. Based on the typical application characteristics of the FPGA, a digital design framework for FPGA-based systems is proposed to realize a traceable design process from requirements to implementation. Subsequently, a model-based forward comprehensive reliability analysis method is proposed, which uses a SysML-based mapping mechanism to integrate Failure Mode and Effects Analysis (FMEA) and Fault Tree Analysis (FTA) methods into the design process, so as to comprehensively identify and analyze failure modes from systems to components and optimize and improve system design. Finally, the proposed method is applied to the analog output design of FPGA-based systems. The proposed method can provide guidance for improving the reliability of FPGA-based DI&C systems and provide theoretical basis for the further engineering application.

Simulation of the process of cryogenic freezing of coriander seeds

In the technology for extracting the required components from plant raw materials, in most cases, the grinding process is used as a preparatory operation before the main process, followed by the separation of the extracted material into target components.In most cases, as a result of such a process, we can talk about the effective extraction of only a single target component, while others inevitably lose their qualitative and quantitative indicators, which is due to the morphology of the plant raw material.One of the promising directions in the processes of destruction of plant material for further operations is selective disintegration. For this purpose optimal process conditions have been selected, such as heating, freezing and others. Raw materials obtained as a result of selective destruction can be effectively fractionated according to morphological and physicochemical characteristics, and only after that can be sent to subsequent operations with the greatest efficiency.Under modern conditions, the loss of essential oil in coriander associated with splitting the fruit reaches 23.4% of the oil weight in whole fruits. At the same time, the essential oil from split fruits is enriched with valuable components – linalool, geraniol, geranyl acetate and, in addition, contains less hydrocarbons and camphor. As shown in [1], oil from split fruits can be used to adjust the composition of batches of coriander essential oil in order to increase the content of linalool while simultaneously reducing the content of undesirable components – hydrocarbons and camphor, and can also be used primarily to isolate valuable components – linalool, geraniol. To reduce losses associated with splitting coriander fruits, it has been proposed to carry out mathematical modeling of the process of cryogenic freezing with subsequent grinding of the frozen mass, which will significantly reduce losses of essential oil. Considering that essential oils extracted from coriander show high antibacterial, antioxidant and antifungal activity [2], increasing the yield of high-quality coriander essential oil will allow its wider use in flavoring and food preservation, as well as for medicinal purposes, which is important and actual task.

Open Globe Injury Repairs Among Medicare Beneficiaries from 2011 to 2020

ABSTRACT Purpose To explore patient and surgeon characteristics for open globe injury repairs (OGRs) and rates of subsequent operations. Methods Using a retrospective cohort design, eyes of patients ≥18 years who underwent OGR among 100% Medicare Fee-For-Service dataset from 2011 to 2020 were included. Current Procedural Terminology (CPT®) codes were used to identify OGR. Patient characteristics were reported, and surgeon characteristics were stratified by sex and compared using Chi-square and Student’s t-test. Overall rate of subsequent operations was reported, and trends of subsequent operations over time were assessed using Cochrane-Armitage trend test. Results A total of 16,576 patients with a mean age of 73.89 years (±12.89) underwent OGR. Most patients were White (79.68%, n = 13,207) and 49.44% (n = 8196) were female. More patients resided in a rural area (18.71%; n = 3102) relative to surgeon location (4.51%, n = 748; p < 0.001). A total of 5,898 surgeons performed these OGRs with 77.33% (n = 4,561) male and 22.67% (n = 1,337) female surgeons. Male surgeons performed most of the OGRs (76.35%, n = 12,655; p < 0.001). On average, a surgeon performed a single OGR annually (Mean: 1.08 ± 1.04; Range: 0.11–40). Among all OGRs, 51% (8,452/16,576) had ≥1 subsequent operations in median 29 days (IQR: 10–86), which increased during the last decade from 47% to 51% (p = 0.008). Conclusion Geographic and workforce disparities in ocular trauma warrant future investigation. Further studies can also assess the reasons for increase in the incidence of subsequent procedures after OGR over time.

Prescribed-time command filtered control for a class uncertain nonlinear systems

This article delves into the intricate challenge of implementing prescribed-time command filtered control in the context of uncertain nonlinear systems. Firstly, a prescribed-time function is defined to lay the groundwork for subsequent controller design. Subsequently, a novel prescribed-time command Filtered controller is proposed for high-order nonlinear systems featuring unknown parameters. This controller guarantees swift error convergence within a predefined time range, with the added capability of periodic error convergence to zero during subsequent controller operations. A pivotal innovation in this study lies in the controller’s design, which remains unaffected by the system’s initial conditions. This unique feature enables the prescribed time to be flexibly set within physical constraints, diverging markedly from conventional finite-time control theory. Theoretical analysis has conclusively shown that the controller achieves full-state tracking error convergence within the specified time frame. The efficacy of the research findings is substantiated through two simulation cases, underscoring a substantial contribution to the refinement and adaptability of nonlinear system control theory.

Optimal Transport Map With Prescribed Direction Indicator for Seismic Full‐Waveform Inversion

AbstractThe quadratic Wasserstein (W2) metric has been proposed as a promising misfit function to mitigate cycle‐skipping phenomena in full‐waveform inversion. Mathematically, we demonstrate that the smoothness of the W2‐based adjoint source is two orders of magnitude higher than that based on L2‐norm, which guarantees a larger convergence radius of related inverse problems. However, the oscillatory characteristics of seismic signals and subsequent operations of transforming them into probability densities would decrease the accuracy of the optimal transport map T(t) and exacerbate the nonconvexity of the misfit function. To tackle these challenges, we propose the concept of prescribed direction indicator, which indicates the properly matching direction from predictions to observations, in order to correct inaccurate T(t). 1D synthetic examples suggest that reasonable bijection can be constructed through the proposed method. Numerical experiments demonstrate that it works well during optimization procedures, including enlarging the convergence radius of the inverse problem, improving the computational efficiency and enhancing the reliability of inversion results.

Stress-strain state of building structures taking into account possible local failure of the element

The issue of choosing a structural design and material for supporting structures is an important technical and economic task at the stage of developing a design solution. It depends on a number of factors: consequence class of the structure, reliability of the design solution, savings in basic building materials. The publication provides a classification of design schemes and types of load-bearing structures used in the corresponding solutions. The disadvantages and advantages of using prefabricated and monolithic structures for the installation and subsequent operation of the structural scheme of buildings and structures are considered. Modern design requirements include ensuring the ability of a damaged structure to adapt to new conditions while continuing to function while ensuring the integrity of human life, property and equipment. New conditions mean the consequences of the occurrence of a certain emergency situation, accompanied by weakening or overloading of the load-bearing structures of a structure or soil foundation: a change in the structural design, a combination of new existing loads and a redistribution of internal forces. The publication reflects the results of assessing the redistribution of the stress-strain state of the elements of the “base - foundations - load-bearing structures” system as a result of the implementation of a hypothetical emergency situation with the exclusion of the load-bearing structure from operation. The case of the collapse of one of the vertical load-bearing elements (local failure of the pylon) of an underground floor, which can be used as a dual-use structure, is considered. Calculations for the stability of the structure against progressive collapse were carried out by numerical modeling in the LIRA SAPR-2019 software using a quasi-static calculation and the method of direct integration of dynamics over time. It has been demonstrated that the method of numerical modeling the joint work of a building with a soil base affects the results of a calculation of the progressive collapse of the building frame. The influence of local collapse of a vertical load-bearing element on the redistribution of stresses and strains in the foundation structures of a building section is assessed. The load on the piles under the pylons around the element removed under the local failure scenario is expected to increase by 15...25%.

Streamlined jet tagging network assisted by jet prong structure

Attention-based transformer models have become increasingly prevalent in collider analysis, offering enhanced performance for tasks such as jet tagging. However, they are computationally intensive and require substantial data for training. In this paper, we introduce a new jet classification network using an MLP mixer, where two subsequent MLP operations serve to transform particle and feature tokens over the jet constituents. The transformed particles are combined with subjet information using multi-head cross-attention so that the network is invariant under the permutation of the jet constituents. We utilize two clustering algorithms to identify subjets: the standard sequential recombination algorithms with fixed radius parameters and a new IRC-safe, density-based algorithm of dynamic radii based on HDBSCAN. The proposed network demonstrates comparable classification performance to state-of-the-art models while boosting computational efficiency drastically. Finally, we evaluate the network performance using various interpretable methods, including centred kernel alignment and attention maps, to highlight network efficacy in collider analysis tasks.

The Microbiology of Knee Prosthetic Joint Infection and its Influence on Persistent Infection.

Periprosthetic joint infection (PJI) following total knee arthroplasty (TKA) is a severe complication causing a significant burden. The study aims were to establish the epidemiology of microorganisms in TKA PJI, the rate of persistent infection requiring further surgery, and the risk factors for this. Microbiological specimens between June 2002 and March 2017 at five regional hospital sites were identified with revision TKA procedures in the National Joint Replacement Registry. The time between procedures, type of revision strategy, and any subsequent further revision operations were collected. At minimum 2-year follow-up, 174 revision TKA were identified, with a mean patient age of 69 ± 11 years. A broad range of pathogens were identified. Fifty cases (29%) had persistent infection requiring at least one further operative procedure, 13 cases required 3 or more. Coagulase-negative Staphylococcus species (CNS) was seen most with failed surgery, polymicrobial infections also posing a significant risk factor. The best chance of a successful PJI surgical strategy was < 12 months from primary TKA, with the greatest risk between 3 and 5 years (p < 0.05). Younger age significantly increased the risk of further surgery (p < 0.05). Management varied; 103 (59%) debridement, antibiotic therapy and implant retention, with further surgery in 29%; 45 (17%) single-stage revision, with further surgery in 13%; and 26 (15%) two-stage revision, with further surgery in 12%. This study presents the most common causative pathogens for PJI in TKA, and the high rate of persistent infection after initial revision surgery. Risk factors for persistent infection and further revision surgery were polymicrobial and CNS infections, patients who presented between 3 and 5 years following primary TKA, and younger age. This study therefore raises important risk factors and areas for future research to reduce the burden of multiple operations after PJI.

LGG-28. THE ROLE OF REOPERATION IN PEDIATRIC CEREBELLAR PILOCYTIC ASTROCYTOMA

Abstract BACKGROUND Cerebellar pilocytic astrocytomas (cPAs) in childhood have long been recognized to have a good prognosis after total resection but the outcome after incomplete resective surgery remains largely unpredictable with the incidence of radiological progressive disease ranging from 18-100%. Traditionally thought that GTR was required for long-term survival, small residuals were classically resected in a subsequent operation. METHODS We analyzed our Pediatric Low-Grade Glioma (PLGG) database, between 1985 and 2020, and filtered for intracranial pilocytic astrocytomas to determine what clinical or radiological factors precipitated revisional resective surgery in our single quaternary center cohort. RESULTS Using our Pediatric Low-Grade Glioma (PLGG) database, 283 patients were identified to have a histopathological diagnosis of intracranial pilocytic astrocytoma between 1985-2020 of which 202 were within the cerebellum (68.2%). The majority of patients with cerebellar PA were between 1-10 years of age (n=147, 73.5%) without gender predominance (M:F=99:101), usually presenting with 1 lesion (n=197, 98.5%). Gross total resection (GTR) was achieved in 74.5% (n=149) of initial surgeries for cerebellar PA. In patients with NTR or STR, the mean largest diameter of the post-operative residual was 1.1cm (0.2-3.7cm). Seven patients with STR did not require a second resective intervention. In 31 patients the neuro-oncology multidisciplinary team (MDT) recommended a second surgical resection at a mean time interval of 22.9 months (0.13-81.6 months) from the initial surgery. Proportionally, the children who underwent multiple resections were also more likely to receive adjuvant chemo/radiotherapy. Functionally, the children in the multiple operation cohort experienced more complications of therapy including ongoing endocrinopathy, treatment-associated hearing deficit, and neurocognitive deficits. CONCLUSION Residual disease in cPA should be maintained under clinocoradiological surveillance post-operatively with adoption of a more conservative approach when residual disease is not significantly changing over time.

In-situ synthesis of yolk-shell Si/C anodes via ZnO transformation for high rate lithium-ion batteries

The conceptual design of yolk-shell structured Si/C composite materials is considered an effective approach to enhancing the structural stability of silicon-based anode materials over long cycles. Here, for the first time, zinc oxide is used as both the internal sacrificial layer and the external coating layer reactant, allowing it to be transformed into voids and the carbon layer precursor during subsequent operations. These internal voids can buffer the volume expansion of silicon, ensuring the electrode's integrity during cycling. The ZIF layer formed through in-situ solvothermal reactions can effectively reduce the occurrence of isolated ZIF in the solvent, resulting in better coating of the nano‑silicon particles. Compared to traditional processes for preparing yolk-shell structures, this gentle synthesis strategy avoids the use of HF, offering a new direction for large-scale production. This optimized yolk-shell Si/C-0.70 M electrode exhibits excellent rate performance (specific capacity of 988 mA h g−1 at a high current density of 2 A g−1) and long-term cycling stability (specific capacity of 722 mA h g−1 after 300 cycles at a current density of 0.5 A g−1; reversible specific capacity of 557 mA h g−1 after 500 cycles). Therefore, this scalable study offers a new approach for safely producing yolk-shell anode materials with high cycle stability on a large scale.

Research on Thread Seal Failure Mechanism of Casing Hanger in Shale Gas Wells and Prevention Measures

The strength and sealing failure of the connecting thread of the casing head mandrel hanger causes huge economic losses. One of the major challenges is the thread seal failure mechanism of the casing hanger in the wellhead during pressure testing in shale gas wells. In order to analyze the failure causes of connecting threads and put forward improvement measures, a typical case of a well accompanied by a hanger seal failure is analyzed in this paper, and a series of material tests are carried out. The microstructure and mechanical properties of casing materials and hanger materials could meet the field requirements. It is concluded that both the hanger material and casing material are characterized with significant ductile fracture. A three-dimensional model of the hanger and casing system is established, and the mechanical behavior is calculated for the connecting thread under different working conditions. The results showed that the connection degree of the hanger–casing is insufficient at the torque recommended by the manufacturer because of the difference in wall thickness between the box thread of the hanger and the box thread of the joint according to the connection degree of the coupling casing. It is seen that the high contact pressure ring of zone three on the sealing surface plays an effective sealing role under the manufacturer’s recommended torque (20,465 N·m). Finally, when the torque is increased by 25%, the maximum contact pressure between the pin thread of the casing and the box thread of the hanger can fully meet the internal pressure from the wellbore pressure test and the internal pressure strength required for subsequent operations.

The method of calculating the vector antenna pattern based on the algebra of quaternions

The quaternion algebra contains the algebra of real and complex numbers, as well as three-dimensional vector algebra. The algebra of quaternions finds application in describing the rotations of coordinate systems, which is also of interest in describing problems of electrodynamics, in which it is often necessary to perform a transition from the basis of sources to the basis of observation. It is shown that using the algebra of quaternions, it is possible to express Maxwell's equations and their solutions in a coordinate system invariant form. A method for calculating a vector antenna based on the algebra of quaternions is proposed. It is shown that the algebra of quaternions is applicable not only for the calculation of electromagnetic fields, radiation patterns, but also for the calculation of polarization characteristics. All transformations define products of rotation functions, for which it is enough to find trigonometric functions sinx and cosx once, and all subsequent rotation operations are performed when implementing quaternion algebra procedures. The application of the quaternion algebra also avoids errors in determining the directions of turns. The proposed methodology can be used to design antennas placed on mobile objects when solving problems of analysis and synthesis.

MODELING OF A LIGHTWEIGHT FLAT FLOOR WITH VOIDS MADE OF PLASTIC BALLS

Formulation of the problem. Prefabricated monolithic construction in domestic and global practice in recent years has occupied a small share in the field of construction. A fairly large number of designs of prefabricated monolithic lightweight floors, as well as its individual structural elements, have been proposed. The use of lightweight floors in the construction of residential and public buildings can significantly reduce the consumption of materials and the dead weight of structures and increase the size of live loads and overlapping spans. Despite this, it cannot be said that effective design solutions have been found that can maximally satisfy the requirements of consumers, architects and builders. Based on this, a constructive solution for a lightweight prefabricated monolithic floor with voids made of plastic balls, quite effective from the point of view of construction and subsequent operation, was proposed and investigated. The proposed design solution for a lightweight prefabricated monolithic flat floor with voids made of plastic balls has less mass than solid floors and optimal use of material resources, namely the consumption of concrete and reinforcement. Therefore, research to determine the optimal design parameters of a flat lightweight floor with void formers made of plastic balls is relevant. The purpose of the article is to conduct numerous studies of the stress-strain state of the proposed design of a prefabricated monolithic floor with voids made of plastic balls. Conclusion. As a result of the research, it was established that it is rational to use hollow balls made from recycled materials as a material for making voids from balls in flat floors. Moreover, all studied floor options with spans of 6 m, 7 m, 8 m and void sizes made of balls with diameters of 180 mm, 315 mm and 500 mm meet the requirements of the first and second groups of limit states.