Different Types Of Connections Research Articles

Experimental analysis of the performance of screwed connections for steel-timber composite beams

The proposed research addresses the structural behavior of screwed connections in composite beams consisting of Cold-Formed Steel (CFS) profiles and timber boards. An experimental program consisting of 30 push-out tests involving six different models was conducted to evaluate the performance of different types of connection. The screw diameter and spacing were different in each model, and in one out of every five specimens of each model, the screws were installed with steel washers. Results indicate that the screws’ diameter influences the connection’s load-carrying capacity. Results also indicate that the spacing of screws influences the connection’s longitudinal shear flow: the larger the spacing between screws, the lower the longitudinal shear flow. Conversely, results from connections involving steel washers did not show any increase in load-carrying capacity or stiffness. The failure mode detected in the tested specimens resulted from the crushing of the Oriented Stranded Board (OSB) related to the rotation of the self-tapping screws. The typical failure mode, called "screw tilting", can be explained by analyzing the axial and transverse projections of the push-out force, where the latter causes crushing of the timber through contact pressure, and the former induces tension in the screw.

Attention-based dynamic multilayer graph neural networks for loan default prediction

Whereas traditional credit scoring tends to employ only individual borrower- or loan-level predictors, it has been acknowledged for some time that connections between borrowers may result in default risk propagating over a network. In this paper, we present a model for credit risk assessment leveraging a dynamic multilayer network built from a Graph Neural Network and a Recurrent Neural Network, each layer reflecting a different source of network connection. We test our methodology in a behavioural credit scoring context using a dataset provided by U.S. mortgage financier Freddie Mac, in which different types of connections arise from the geographical location of the borrower and their choice of mortgage provider. The proposed model considers both types of connections and the evolution of these connections over time. We enhance the model by using a custom attention mechanism that weights the different time snapshots according to their importance. After testing multiple configurations, a model with GAT, LSTM, and the attention mechanism provides the best results. Empirical results demonstrate that, when it comes to predicting probability of default for the borrowers, our proposed model brings both better results and novel insights for the analysis of the importance of connections and timestamps, compared to traditional methods.

Design and experimental validation of a finite-size labyrinthine metamaterial for vibro-acoustics: enabling upscaling towards large-scale structures.

In this article, we present the design and experimental validation of a labyrinthine metamaterial for vibro-acoustic applications. Based on a two-dimensional unit cell, different designs of finite-size metamaterial specimens in a sandwich configuration including two plates are proposed. The design phase includes an optimization based on Bloch-Floquet analysis with the aims of maximizing the band gap and extruding the specimens in the third dimension while keeping the absorption properties almost unaffected. By manufacturing and experimentally testing finite-sized specimens, we assess their capacity to mitigate vibrations in vibro-impact tests. The experiments confirm a band gap in the low- to mid-frequency range. Numerical models are employed to validate the experiments and to examine additional vibro-acoustic load cases. The metamaterial's performances are compared with benchmark solutions, usually employed for noise and vibration mitigation, showing a comparable efficacy in the band gap region. To eventually improve the metamaterial's performance, we optimize its interaction with the air and test different types of connections between the metamaterial and the homogeneous plates. This finally leads to metamaterial samples largely exceeding the benchmark performances in the band gap region and reveals the potential of interfaces for performance optimization of composed structures.This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'.

Examination of Various Abutment Designs Behavior Depending on Load Using Finite Element Analysis.

Studies on dental implant abutments' geometric design and material selection offer significant innovations and results. These studies aim to improve the abutments' functionality and aesthetic performance, minimize microcavities' formation, and ensure implant-supported prostheses' longevity. For example, CAD-CAM fabricated custom abutments have been found to produce a better marginal fit and fewer microgaps than standard abutments. In an in vitro study, transepithelial abutments offered lower microgap values than titanium-based abutments and provided a better fit at the implant-abutment interface. It is known that studies to improve mechanical and biological performance with Polyether Ether Ketone (PEEK) material have been addressed. New materials such as PEEK and zirconia have offered significant advantages in biocompatibility and aesthetics. Along with those studies, different abutment designs are also important. Abutment geometry is optimized to improve stress distribution and minimize peri-implant bone loss. In implant and abutment connections with different angles, mechanical life performances may vary depending on static and dynamic load. These studies emphasize the importance of material research on different types of connections to improve dental implants' durability, homogeneous load distribution, and reliability. The abutment parts used in implant treatment are insufficient to distribute the load homogeneously against chewing pressure due to their materials and geometry. Non-uniform load distribution damages the abutment and the prosthetic crown, accelerating the wear process. This study aimed to create different abutment designs to improve dental implants' biomechanical performance and longevity. This study aimed to increase the mechanical durability of the implant-abutment connection by reducing stress concentrations in response to masticatory compression on the abutment in different directions and forces and to guarantee the long-term success of the implant system by providing a more homogeneous stress distribution. It aimed to apply different forces in the axial direction to these models in a simulation environment and to calculate and compare the deformation and stress load distribution. As a method, three-dimensional models of the parts used in implant treatments and forming the implant system were designed. Different abutment designs were created with these models. Taking the current material values used in implant treatments as a reference, finite element analysis (FEA) was performed by applying different axial loads to each implant system model in the ANSYS software (version 24.1). Comparative analysis graphs were prepared and interpreted for the stress values obtained after the applied load. This study evaluated the mechanical performance of different abutment models (A, B, C, D, and E) under a 100 N load using the Kruskal-Wallis test. The Kruskal-Wallis test showed significant differences between the groups (p < 0.001). The greatest difference was observed between models E and A (q' = 6.215), with a significant difference also found between models C and A (q' = 3.219, p < 0.005). Regarding stress values, the highest stress on the abutment was observed in Model B (97.4 MPa), while the lowest stress was observed in Model E (9.6 MPa). The crown exhibited the highest stress in Model B (22.7 MPa) and the lowest in Model E (17.3 MPa). The implant stress was highest in Model C (14.8 MPa) and lowest in Model B (11.3 MPa). The stress values for the cortical bone and cancellous bone were quite similar across the models, showing no significant differences. These findings indicate that the abutment design and material selection significantly impact mechanical performance. Among the implant systems created with five different abutment models, in which the existing abutment geometry was also compared, homogeneous and axial distribution of the load on the abutment was achieved, especially with viscoelastic and surface area increased abutment designs. Clinically, the inadequacy and limited mounting surface or geometry of the abutments used in today's implant treatment applications have led to different design searches. It was concluded that the designs in this study, which are considered alternatives to existing abutment models, contribute positively to the mechanical life of the abutment material, considering the von Mises stresses and directions. This study brings a new perspective to today's practices and offers an alternative to treatment practices.

Flexural behaviour of built-up I-shaped bamboo scrimber beams: experimental tests and design method

ABSTRACT This paper presents the flexural behaviour of built-up I-shaped bamboo scrimber beams under four-point bending. Ten bamboo scrimber beams were tested, employing different types of connections between the web and flanges. The load-deflection relationship, failure mode and load-slip relationship of beams were obtained through experimental tests. Besides, the measured strains of bamboo scrimber in various regions were used to analyse the flexural mechanisms of I-shaped beams. Test results showed that the beam with a glued connection exhibited debonding at the web-flange interface, hindering the development of flexural capacity of the beam. By using self-tapping screws or bolted steel angles to strengthen the connection, the slip between the web and flanges was considerably reduced, resulting in the increased flexural capacity of beams. The rupture of the bottom flange near the concentrated point load led to the final failure of strengthened beams. The design method for mechanical fastened glulam beams in Eurocode 5 was adopted to assess the flexural capacity of bamboo scrimber beams. Comparisons between experimental results and calculated results per Eurocode 5 indicate that the method is capable of predicting the flexural resistances of I-shaped bamboo scrimber beams with reasonably good accuracy.

Recommendation Of RLC Circuit and Its Uses in Electronic Devices

This paper introduces RLC circuit, which is a circuit with resistor, inductor, and capacitor. This paper will introduce the different types of RLC circuit and will show the uses of them in electronic devices. Equations are used to express the relationship of the different elements in the circuit, and theories are introduced to prove some equations. In addition, figures can also show the different types of connections of RLC circuit, including theoretical series and parallel connection and connection that will come in use in electronic devices. This first part of article will enable people to understand what RLC circuit is, the second part will use equations to prove certain theories, and the third part of the article will introduce how RLC circuit is used in radios, and the different ways of connection which cause the circuit to receive waves, and filter waves. The final part will conclude all the parts mentioned in the article.

How teachers make connections among ideas in mathematics instruction.

Conceptual understanding involves understanding connections among ideas within a domain. In this chapter, we consider how teachers support students in learning about connections among ideas in mathematics. We review research focusing on teachers' connection making in mathematics classrooms, and we consider several dimensions of variability in that connection making. Across three corpora of lessons that varied in students' grade levels (first grade to college), cultural settings (United States and China), and mathematics content, we found that all teachers produced linking episodes, but the frequency with which they did so varied substantially, raising new questions about the sources and consequences of that variability. Teachers of first-grade students in China routinely engaged their students in co-constructing links; teachers of middle schoolers and college students in the United States typically explained links to students. Linking episodes targeted many different types of connections, including connections between representations, connections between principles and exemplars, connections between procedures and concepts, and connections between concepts and real-world instantiations. Across all three corpora, teachers expressed linked ideas multimodally in a majority of linking episodes. Based on the findings, we present several hypotheses about how teacher behaviors may support students' understanding of connections among ideas, and we suggest directions for future work.

A Novel Projection-based Embedded Discrete Fracture Model (pEDFM) for Anisotropic Two-phase Flow Simulation Using Hybrid of Two-point Flux Approximation and Mimetic Finite Difference (TPFA-MFD) Methods

This paper presents a novel projection-based embedded discrete fracture model (pEDFM) applicable to general two-phase flow simulation in anisotropic reservoirs for the first time. The novel pEDFM is developed based on hybrid two-point flux approximation and mimetic finite difference (TPFA-MFD) methods, which retains the basic features of two-point flux approximation (TPFA) based generic pEDFM workflow and incorporates new features of mimetic finite difference (MFD) to handle full-tensor permeabilities. This is achieved by introducing the concept of effective connection, formulating additional pressure degrees of freedom for effective connections, assigning effective matrix-matrix (m-m) and matrix-fracture (m-f) connections to the corresponding sides of matrix-cell interfaces, presenting methods corresponding to different types of connections to handle low-conductivity fractures, and further deriving formulas of numerical fluxes for effective connections. The resulting global equation system is solved by a Newton-Raphson nonlinear solver with the temporary discretization of the implicit backward Euler scheme. The 2D and 2.5D numerical examples show the novel pEDFM could achieve the same level of computation accuracy and convergence as the reference discrete fracture model (DFM), while avoiding the gridding difficulty of complex fracture networks. It also significantly outperforms classical EDFM based on MFD and generic pEDFM workflow in the computational accuracy for cases with anisotropic full tensor permeabilities. The novel pEDFM, to our best knowledge, is for the first time proposed and developed for general anisotropic two-phase flow simulation and maybe the numerical simulation framework for multi-phase flow in fractured reservoirs with the best comprehensive performance so far.

Effects of module-to-module connection rotational stiffness on the structural performance of high-rise steel modular buildings

With advantages including high productivity and sustainability, modular construction has attracted increasing interest in building project developments. As modular buildings are stepping higher, the modular systems should be better designed to ensure structural safety. In such systems, different types of connections, such as module-to-module (M2M) connections, play an important role in the loading transfer. However, the investigation into the rotational stiffness of the M2M connection was still insufficient in the literature. This paper aims to examine the effects of M2M connection rotational stiffness on the structural performance of high-rise steel modular buildings. A theoretical analysis was conducted on a hypothetic three-storey three-span steel frame to simplistically demonstrate the significant effect of connection rotational stiffness on the internal force distribution of modular buildings. To assess the applicability of preliminary findings in real-life high-rise steel modular buildings, validated numerical models were employed to determine the rotational stiffness of a newly proposed innovative and practical M2M connection. Subsequently, structural models of a 40-storey steel modular building with different M2M connection rotational stiffness values were established to conduct comprehensive investigations. The analysis results indicated that the rotational stiffness of M2M connections plays a critical role in determining the behaviours of critical structural members. The findings provide important references for the design of M2M connection stiffness and structural performance analysis of high-rise steel modular buildings.

Seismic Response of Reinforced-Concrete One-Storey Precast Industrial Buildings with Horizontal Cladding Panels

An extensive parametric study of the seismic response of one-storey precast buildings with horizontal cladding panels frequently used in Central Europe was conducted to analyse the panels’ influence on the overall response of buildings and to find out if the panels can be considered non-structural elements when they are attached to the main building with the connections typically used in practice in Central Europe. The studied structural system consisted of reinforced concrete columns and beams connected by dowels. Horizontal cladding panels were attached to columns using one of the most frequently used isostatic fastening systems. The top connections provided out-of-plane stability, and the bottom connections supported the panel in the vertical direction. The parametric study was preceded by extensive experimental research, including cyclic tests on connections and full-scale shaking table tests of whole buildings. The results of experiments were used to reveal the basic response mechanisms of panels and connections and to develop, validate and calibrate numerical models employed in the parametric study presented herein. Fifteen generalised structures with different masses and heights were subjected to 30 accelerograms with two peak ground acceleration (PGA) intensities of 0.3 g and 0.5 g, corresponding to significant damage and near-collapse limit states. The effects of the construction imperfections in connections, the silicon sealant panel-to-panel connections and different types of connections of the bottom panel to the foundation were analysed. The crucial parameter influencing the response was the displacement capacity of the connections, which was considerably affected by the construction imperfections and, consequently, difficult to estimate. It has been observed that in some buildings, particularly in shorter structures with smaller mass, cladding panels can have a somewhat more notable influence on the overall response. However, in general, when the considered types of connections are used, the panels can be considered as non-structural elements, which do not importantly influence the response of the main building. Owing to structural imperfections and relatively short available gaps, the failure of the considered top connections and falling of the panels is very likely in the high seismicity regions. In the most adverse cases, it can occur even in the moderate seismicity regions.

Urbanity: automated modelling and analysis of multidimensional networks in cities

Urban networks play a vital role in connecting multiple urban components and developing our understanding of cities and urban systems. Despite the significant progress we have made in understanding how city networks are connected and spread out, we still have a lot to learn about the meaning and context of these networks. The increasing availability of open data offers opportunities to supplement urban networks with specific location information and create more expressive urban machine-learning models. In this work, we introduce Urbanity, a network-based Python package to automate the construction of feature-rich urban networks anywhere and at any geographical scale. We discuss data sources, the features of our software, and a set of data representing the networks of five major cities around the world. We also test the usefulness of added context in our networks by classifying different types of connections within a single network. Our findings extend accumulated knowledge about how spaces and flows within city networks work, and affirm the importance of contextual features for analyzing city networks.

Paradoxical Connections in Sarah Ruhl’s Dead Man’s Cell Phone

The paper examines different types of paradoxical connections in Sarah Ruhl’s Dead Man’s Cell Phone with respect to contemporary characteristics of American theatre. It is so clear that the play has a smooth transformation or connection between paradoxical states or situations. The transformation happens due to spatial, and temporal conditions, and different humankind values. The play is full of different types of connections due to social ties, contradictive life situations, death and life, the whole and the parts, the spatial and the temporal transformation, truth and lies, happiness and misfortune, fancy and facts, and humanity with technology. The study is qualitative depending on the study of the cases within the play that are contradicting each other, yet they serve in deepening the meaning and the understanding of the cases. The paradoxical issues to be studied in a comparative way, these comparative situations serve higher thematic issues in a philosophical dimension in very carefully woven relations between the characters and situational environment as well. The common sense that the play made is to accept the philosophy of black and white as positive paradoxical relation, that the black helps to see the pure white and vice versa. Common unanswered questions are to be presented in a rhetorical and philosophical manner; targeting these questions is the way of being closer to a bunch of truths about the complicated fabric relationships which link the characters all together.

РОБОТОТЕХНІЧНА СИСТЕМА З ОДНОТИПНИМИ ЧАСТОТНО-ЗАЛЕЖНИМИ КОМПОНЕНТАМИ У ТРАКТІ ОБРОБКИ СИГНАЛІВ ДАТЧИКІВ

Abstract. The issue of building a sensor signal processing path on the same type of components in computer robotic systems, which can comprehensively rebuild their characteristics by software and hardware means depending on the operating conditions to increase the system efficiency, is considered. Different types of connections of analog and digital second-order frequency-dependent components are considered, since a high-order processing path is easier to form from the same type of low-order components. This is due to the low cost of calculating the coefficients of the transfer function and the number of coefficients, ease of adjustment or reconstruction, moderate power consumption and processing time. It is shown that a serial connection is best suited for the sensor signal processing path, since signal distortion occurs in other connections. To increase the order of the processing path, it is suggested to use a serial connection of the same type of frequency-dependent components of the second order. Obtained ratios that allow to calculate the frequency of the main typical component based on the required frequency of several components connected in series. These ratios are very difficult to implement in robotic systems, as they do not have large computing resources. Since the range of frequencies and the number of components are limited, it is recommended to calculate the necessary frequencies in advance and summarize them in the table. When working in real time, it is advisable to use these tables for rebuilding. When connecting analog and digital basic filters of the same type in series, it is advisable to use the main filters of the second order of Butterworth and Chebyshev of the second kind with flat frequency response in the passband, which will ensure a good increase in the steepness of the frequency response decline and make it possible to predict the value of the cutoff frequency for the low-pass filter. And for bandpass filters, only Butterworth filters. Keywords: Industry 4.0-5.0, robotic systems, frequency-dependent components, component connection types, series connection, main typical component, amplitude-frequency characteristic.

Analysis and Experimental Study on Mechanical Properties of Large-Diameter Grouted Sleeve Connections

The mechanical properties of a connection are essential for the structural performance of a prefabricated bridge pier because the connection is located in the weakest part of the pier structure. Among different types of connections, a large-diameter grouted sleeve connection with a connection bar of 40 mm diameter has been widely exploited in recent years. However, past experimental researches and the latest corresponding industrial standards barely pay much attention to the mechanical properties of this large-diameter grouted sleeve connection. Therefore, a series of experiments and numerical simulations were conducted to address the critical issue. First, the static tension tests were carried out on fabricated specimens considering the eccentricity of the bar, and then the internal conditions of the sleeve were detected using industrial computed tomography. Experiment-based tests showed that the bearing capacity of all connections exceeds the standard value of the tensile strength of connection bars and mainly depends on the bearing capacity of connection bars. The eccentricity of the bar could increase the local stress of the sleeve, which must be addressed during the design and construction progress. The inner bonding interface between the bar and the grouting material was destroyed when the bar was fractured or pulled out. Moreover, the results of experiments and numerical simulations revealed that some geometry-related parameters about the sleeve and the bar could be properly optimized for further design. The sleeve design parameters considering the eccentricity of the bar was recommended as 1.27, and a new sleeve structure with variable thickness was proposed.

Removable, Reconfigurable, and Sustainable Steel Structures: A State-of-the-Art Review of Clamp-Based Steel Connections

In this review paper, first of all, an analysis of the circular economy and its application to steel structures is carried out. It highlights the need to apply the philosophy of Design for Deconstruction or Design for Disassembly (DfD) from the conception of the structure so that it can be truly reconfigurable. Then, a brief review of the different types of connections for steel structures is conducted, comparing the level of research and development of each of them and the degree of reconfiguration that is possible to obtain. Subsequently, the article focuses on the type of connection using clamps, a key point of this work and on which, to date, there are no state-of-the-art studies. It describes the types of clamps, their principle of operation, the types of connections developed with them, and the results of the different investigations that allow for calculating these types of connections. A summary is also given of how these connection types work according to the geometrical characteristics of the clamp and the bolt so that this review work can serve as a driver for the widespread use of clamp-based connections by researchers and engineers in the design and manufacturing of demountable and reconfigurable steel structures. Finally, some conclusions are given, indicating the advantages and disadvantages of this connection system and future lines of research.

Experimental and Analytical Study on the Compressive Arch Action of Precast Concrete Assemblies with Monolithic Connections to Resist Progressive Collapse

Although the first progressive collapse event occurred in precast concrete (PC) buildings due to gas explosions, the behavior of PC buildings resisting progressive collapse is still unclear because related tests are few, and the types of PC connections vary. To study the progressive collapse resistance of monolithic PC beam-column assemblies under a middle column removal scenario, an experimental program including four PC assemblies and one reinforced concrete (RC) assembly is conducted. These PC assemblies contain different types of beam-column connections, including connections of lap-splice, 90° hook anchorage, U-shaped bar, and combined U-shaped bar and 30° hook anchorage. The test results demonstrate that flexural action, compressive arch action (CAA), and catenary action were mobilized in sequence in the beams of RC and PC assemblies. Thus, in general, the development of load resisting mechanisms of PC assemblies is similar to that of RC assemblies, although different types of connections may affect the magnitude of each mechanism. The PC assemblies with 90° hook anchorage and U-shaped bar connections attained a CAA capacity similar to that of the RC assembly, whereas the PC assembly with the combined connections had a greater CAA capacity because of plastic hinge relocation at the beam ends near the middle column. The PC assembly with lap-splice connections achieved the lowest CAA capacity due to the anchorage failure of the beam bottom rebar. However, this PC assembly attained the greatest catenary action capacity, because the beam bottom rebar did not fracture and could still develop tension. Subsequently, an analytical model is proposed to reveal the nature of CAA and to better understand the influence of critical parameters.

Identification of Russian Clusters Based on the Synthesis of Functional and Spatial Approaches

Introduction. The study continues the approbation of the methodology of cluster identification, developed earlier by the authors and the study of regional industry specialization, within the framework of which the database “Clusters of Russian Regions” was developed. The relevance of the topic is the necessity of the methodology for complex clustering of regions in order to provide further recommendations for the development of industrial sectors. The purpose of the article is to develop and test the methodology for identifying clusters on the territory of Russia based on the synthesis of functional and spatial approaches. Materials and Methods. The analysis of intersectoral relations within the framework of the functional approach consisted in the application of the maximum method, which allows to trace the chain of consumption relative to the main suppliers and main consumers between industries based on the Russian “Input – Output” table of 2016. The spatial approach was implemented by calculating location quotients, determining z-scores, correlation coefficients analysis between clusters’ location quotients to establish regional and interregional links. Results. The results of the article have tested the methods proposed by the authors for the clustering process of regions. The results obtained after applying the methods revealed the localization of the cluster “Chemical Products” in the territories of certain regions of the Russian Federation and its existing significant functional and spatial relationship with the clusters: “Construction”, “Production Equipment” and others. Moreover, it has been determined that the chemical industry has different types of connections: both the functional connection (with the “Metallurgy” cluster) and the presence of spatial communication: interregional (“Construction”), regional (“Production equipment” and others). Therefore, it has been proved that an integrated approach is necessary to identify industrial clusters. Discussion and Conclusion. Considerations of previous studies on regional clustering and our obtained results on the cluster “Chemical products” have confirmed the need to use the complex methodology of regional clustering, which includes the synthesis of functional and spatial approaches, since both approaches separately have their limitations: functional connection does not mean the existence of spatial (analysis of clusters “Chemical products” and “Metallurgy” interconnection) and vice versa. This result will help to comprehensively solve the problem of the chemical industry development in Russia, due to the understanding of the competent placement of enterprises and taking into account the relationship with enterprises of various industries. The materials of the article can be useful both for scientists dealing with the problems of regional economic development, and for governmental bodies whose goals include making managerial decisions in the field of industrial development.

Arena3Dweb: interactive 3D visualization of multilayered networks supporting multiple directional information channels, clustering analysis and application integration.

Arena3Dweb is an interactive web tool that visualizes multi-layered networks in 3D space. In this update, Arena3Dweb supports directed networks as well as up to nine different types of connections between pairs of nodes with the use of Bézier curves. It comes with different color schemes (light/gray/dark mode), custom channel coloring, four node clustering algorithms which one can run on-the-fly, visualization in VR mode and predefined layer layouts (zig-zag, star and cube). This update also includes enhanced navigation controls (mouse orbit controls, layer dragging and layer/node selection), while its newly developed API allows integration with external applications as well as saving and loading of sessions in JSON format. Finally, a dedicated Cytoscape app has been developed, through which users can automatically send their 2D networks from Cytoscape to Arena3Dweb for 3D multi-layer visualization. Arena3Dweb is accessible at http://arena3d.pavlopouloslab.info or http://arena3d.org.

A Proposed Human Structural Brain Connectivity Matrix in the Center for Morphometric Analysis Harvard-Oxford Atlas Framework: A Historical Perspective and Future Direction for Enhancing the Precision of Human Structural Connectivity with a Novel Neuroanatomical Typology

A complete structural definition of the human nervous system must include delineation of its wiring diagram (e.g., Swanson LW. Brain architecture: understanding the basic plan, 2012). The complete formulation of the human brain circuit diagram (BCD [Front Neuroanat. 2020;14:18]) has been hampered by an inability to determine connections in their entirety (i.e., not only pathway stems but also origins and terminations). From a structural point of view, a neuroanatomic formulation of the BCD should include the origins and terminations of each fiber tract as well as the topographic course of the fiber tract in three dimensions. Classic neuroanatomical studies have provided trajectory information for pathway stems and their speculative origins and terminations [Dejerine J and Dejerine-Klumpke A. Anatomie des Centres Nerveux, 1901; Dejerine J and Dejerine-Klumpke A. Anatomie des Centres Nerveux: Méthodes générales d’étude-embryologie-histogénèse et histologie. Anatomie du cerveau, 1895; Ludwig E and Klingler J. Atlas cerebri humani, 1956; Makris N. Delineation of human association fiber pathways using histologic and magnetic resonance methodologies; 1999; Neuroimage. 1999 Jan;9(1):18–45]. We have summarized these studies previously [Neuroimage. 1999 Jan;9(1):18–45] and present them here in a macroscale-level human cerebral structural connectivity matrix. A matrix in the present context is an organizational construct that embodies anatomical knowledge about cortical areas and their connections. This is represented in relation to parcellation units according to the Harvard-Oxford Atlas neuroanatomical framework established by the Center for Morphometric Analysis at Massachusetts General Hospital in the early 2000s, which is based on the MRI volumetrics paradigm of Dr. Verne Caviness and colleagues [Brain Dev. 1999 Jul;21(5):289–95]. This is a classic connectional matrix based mainly on data predating the advent of DTI tractography, which we refer to as the “pre-DTI era” human structural connectivity matrix. In addition, we present representative examples that incorporate validated structural connectivity information from nonhuman primates and more recent information on human structural connectivity emerging from DTI tractography studies. We refer to this as the “DTI era” human structural connectivity matrix. This newer matrix represents a work in progress and is necessarily incomplete due to the lack of validated human connectivity findings on origins and terminations as well as pathway stems. Importantly, we use a neuroanatomical typology to characterize different types of connections in the human brain, which is critical for organizing the matrices and the prospective database. Although substantial in detail, the present matrices may be assumed to be only partially complete because the sources of data relating to human fiber system organization are limited largely to inferences from gross dissections of anatomic specimens or extrapolations of pathway tracing information from nonhuman primate experiments [Front Neuroanat. 2020;14:18, Front Neuroanat. 2022;16:1035420, and Brain Imaging Behav. 2021;15(3):1589–1621]. These matrices, which embody a systematic description of cerebral connectivity, can be used in cognitive and clinical studies in neuroscience and, importantly, to guide research efforts for further elucidating, validating, and completing the human BCD [Front Neuroanat. 2020;14:18].

Stability Properties of Self-Similar Solutions in Symmetric Teleparallel f(Q)-Cosmology

Self-similar cosmological solutions correspond to spacetimes that admit a homothetic symmetry. The physical properties of self-similar solutions can describe important eras of the cosmological evolution. Recently, self-similar cosmological solutions were derived for symmetric teleparallel fQ-theory with different types of connections. In this work, we study the stability properties of the self-similar cosmological solutions in order to investigate the effects of the different connections on the stability properties of the cosmic history. For the background geometry, we consider the isotropic Friedmann–Lemaître–Robertson–Walker space and the anisotropic and homogeneous Bianchi I space, for which we investigate the stability properties of Kasner-like universes.