Together, these tools may increase the reproducibility and openness of psychological science.A consensus on the importance of open data and reproducible code is emerging. How should data and code be shared to maximize the key desiderata of reproducibility, permanence, and accessibility? Research assets should be stored persistently in formats that are not software restrictive, and documented so that others can reproduce and extend the required computations. The sharing method should be easy to adopt by already busy researchers. We suggest the R package standard as a solution for creating, curating, and communicating research assets. The R package standard, with extensions discussed herein, provides a format for assets and metadata that satisfies the above desiderata, facilitates reproducibility, open access, and sharing of materials through online platforms like GitHub and Open Science Framework. We discuss a stack of R resources that help users create reproducible collections of research assets, from experiments to manuscripts, in the RStudio interface. We created an R package,  Research projects produce experiments, data, analyses, manuscripts, posters, slides, stimuli and materials, computational models, and more. However, the potential added value of these products is not fully realized due to limited sharing and curating practices. Although more transparent communication of these research products has recently been encouraged . However, those materials often contain idiosyncratic file organization and minimal or missing documentation for raw data. In specific areas, organization and documentation standards have emerged,  guidelines to maximize the reuse potential of data and support “discovery through good data management” , and RStudio is its associated integrated development environment . Both are free, open source, and work on Windows, Mac, and Linux systems. These tools are already widely used among psychology researchers: In one crowd-sourced analysis, 16 of 29 analysis teams used R .R is a programming language for statistical analyses ; https:A cornerstone of R is user-created packages, which contain functions, (meta)data, and documentation in a standard format that allows seamless sharing across users and operating systems. Data and functions in R packages are immediately available to others through the R console, and documentation can be viewed in R or online. We first outline how data and functions are included in R packages, and then turn to including other assets, such as manuscripts and posters. A complete guide to R packages is outside our scope (see Wickham ).When an R package is created as shown in Fig. Researchers often develop and use custom functions in their analysis. Although it is possible to declare them directly in the analysis scripts, we suggest declaring functions using the R package standard, by placing the function’s source code into a file in the “R” directory. That directory is automatically created see Fig. . FunctioWrapping functions into R packages also provides a reuse benefit: Functions can be difficult to find in old scripts, but easy to find and load if they are called from an existing package. Thus, formally including one’s functions in R packages facilitates reproducibility and sharing.Broadly, there are three steps to including data in an R package: 1. placing raw data in the “data-raw” directory, 2. creating an R script that processes the raw data and creates an R data object into the “data” directory, and 3. documenting the final data object.First, raw data in any format is stored in the “data-raw” directory to ensure that the method of sharing remains software-agnostic. If possible, that raw data should be in a text-based format, rather than proprietary formats such as SPSS files. Second, instructions for converting and cleaning the raw data into analyzable format should also be included in this directory (the raw data files should not themselves be modified). These pre-processing steps should be saved so that the complete path from raw data to results is transparent and reproducible, preferably in an R script in the “data-raw” directory. That script should end with creating an R data object in the “data” directory. Placing the R data object there ensures that it is included in the resulting R package, which makes using the data effortless for any R user, and eschews the need to download additional files. Loading the R package makes the included data immediately available in the R console.https://crumplab.github.io/vertical/), and in Wickham data. However, as we will see, the package structure can be extended to include analyses, manuscripts, posters, and presentations as well. The complete project is then easily shared online, and even showcased as a website, as we will show below. To enable these additional features, many R packages have been developed . To facilitate their use, we have created an R package, vertical extends the R package template with a set of additional files and directories for products such as manuscripts and posters. These assets are organized such that they can be easily shared online on GitHub or OSF, installed to R as a package, and showcased online as a website. Figure vertical research project.vertical, or any packages contained therein, users must first install it in R , and thus enables including one’s text and analyses in a single document. Because of its importance, we describe R Markdown first.R Markdown allows executable code snippets to be embedded alongside regular text, and simple markup for formatting code . R Mark3Data analysis can be made fully transparent and reproducible with R Markdown. Above, we suggested placing any preprocessing steps in a separate file in the “data-raw” directory, and creating a documented R data object in “data”. If the data object is called mydata and the package is installed and loaded, calling mydata in R will call the data object, ready to be used in analyses. Our favored approach is to write any analyses relevant to a product  directly into the product’s R Markdown source file. Typically, we would include data analysis code in the R Markdown source of the APA style manuscript (see below).vertical project is created, the “vignettes” directory is automatically created with an example data analysis R Markdown script.Nevertheless, sometimes supplementary analyses are conducted that are not included in any other document. These are most conveniently placed in R Markdown files into the “vignettes” directory. Then, when the project is compiled into a website (see below), those analyses are viewable as part of the resulting website. When a papaja R package, that provides an R Markdown template file, and additional helper functions for creating tables and figures  embeds model’s statistical results directly into the manuscript, obviating the need to copy them by hand and removing human error in reporting. References can be automatically added from Zotero using the citr plugin .When a new vertical includes a posters folder where poster documents can be deposited and shared. vertical suggests using the posterdown package . For example, arbitrary R Markdown documents can be included in the vignettes directory. When the project is compiled (see below), R Markdown files in that directory are automatically compiled and served on the website (see Wickham and Hesselberth ).vertical suggests using jsPsych . Scripts can be shared in a self-contained manner such that the experiment is reproducible and the methods are transparent and verifiable. Third, because the experiment is an HTML file it can be shared and run as part of the project website, facilitating understanding of the experimental procedures. Sharing experiment source code with a demonstration could benefit the review process and readers’ understanding of the procedures.vertical facilitates sharing the entire project as an R package for easy access to the data and functions, as a version controlled repository for the project’s source code, and as a website, where the components can be viewed in their final format.Above, we discussed using R Markdown, R package standards, and other R resources for creating research products. The next step is sharing and communicating these products. When the products are created as suggested above, vertical projects enable Git for new projects.The core of our proposal is that all project materials are stored in one directory on the user’s local filesystem. When version control, such as Git, is enabled in this directory, the entire project can be seamlessly shared with others through online platforms such as GitHub, GitLab, and OSF. Version control systems provide filesystems with additional functioning for keeping track of file versions, improved options for collaborating, and seamless integration with online collaboration platforms. For example, old versions of manuscripts are retained in the project’s history. However, the details are outside our scope, and we refer readers to Vuorre and Curley . By defaBecause of the integration between Git(Hub) and one’s local filesystem, users should primarily interact with Git(Hub). However, for long-term preservation, users should also link the project’s GitHub repository to OSF. This can be done through the “Settings” page on an OSF project’s page. Then, one can create an OSF registration of that project, which preserves the GitHub repository’s current status on OSF permanently. This way, users gain both GitHub’s convenience and OSF’s long-term preservation.pkgdown , rather than the official CRAN channel. Sharing as an R package is very convenient for other R users, as any packaged data and functions are immediately available for use, natively in R, after package installation. We expand on the extended benefits of using R packages for transparency and reproducibility in the general discussion.If the project contains R functions, data, and documentation following the R package standard, then others can install the package on their computers for fast access to the data and functions from R. Again, integrating the project with GitHub is beneficial, because then others can install the package from GitHub using the https://mybinder.org/), CodeOcean (https://codeocean.com/), or RStudio Cloud (https://rstudio.cloud/)).It is not uncommon to discover breaking changes in previously working code as a result of updates to a computational environment . As a result, an important component of computational reproducibility is specifying the (software) environment in which the computations were done, or should be done. In general, there is a continuum of static to dynamic approaches to this problem. A static approach could be a list of the requirements for the computational environment; whereas, a more dynamic approach could be a website or other container that actively runs the required environment . Nevertheless, this static approach is not incompatible with dynamic approaches, and advanced users could conceivably adapt vertical websites to link to cloud computing environments that preserve and execute project scripts.vertical, a stack of R tools for a single-platform solution for creating, curating, and communicating psychological research projects in a reproducible manner. It might seem that the benefits of this approach apply only to R users. We believe this is not the case; the workflow creates a single repository that includes all the research products related to a project, which can then be viewed as a public  website and source code repository. Of course, to get the most out of the proposal, some R use is required. However, any standardized computational procedure assumes some computational environment, and our choice of R is natural due to its already widespread adoption in the psychological researcher community. Furthermore, by requiring raw data inclusion, our proposal does not strictly require using R. Also, the software we have discussed, RStudio, works well with other languages, including JavaScript, Python, and C++.We presented https://github.com/psych-ds/psych-DS). Our suggestion is directly compatible with that effort, insofar as the R package standard doesn’t require any special format from the raw data. In fact, future work might bring these two approaches together to inform both how the raw data should be formatted (Psych-DS), and how research products based on that raw data could best be curated and shared (present work).We are not the first to recommend some form of standardization of workflows and procedures within psychology. First, Psych-DS is a collaborative project that aims to “promote the adoption of good practices in the management of scientific data” and “create a machine-readable format for these datasets that can support tools for analysis, discovery, and preparation of datasets in psychology” . The workflowr R package itself is quite mature, and provides helpful tools for compiling many R Markdown documents sequentially, but has a slightly different approach to our proposal, in that workflowr does not itself provide much of a standardized organization for the materials . Further, the materials are not organized as an R package, as they would be in the (extended) vertical approach. Additionally, workflowr does not easily incorporate other types of materials  in the resulting website, unlike vertical. However, it may be slightly easier to use otherwise, for the many useful functions that it provides.There are also at least two other R packages designed to help researchers organize their workflows and facilitate reproducibility and data/code sharing. We highlight these packages here, while also discussing their similarities and differences to our approach. rrtools R package , which, unlike workflowr but like our approach, centers on the R package architecture. Additionally, rrtools helps set up a Docker container and continuous integration services for the project, both tools that we hope become more widely adopted in the future. However, it does not help users set up other important research materials as part of the project’s materials, such as slides and experiments, nor does it help users share their projects as websites.Another approach is contained in the rrtools, vertical, and workflowr are pointing to the same important and general idea: Psychological sciences would benefit from standardizing, as much as possible, the ways in which computational work is curated. We think that these tools and principles are in their infancy, and their importance is only now being recognized. Therefore, we expect these tools to evolve and mutate to best suit the practical researchers’ needs, and hope that our suggestion provides some insight to how these tools might work in the future.More generally, however, tools and descriptions, such as Psych-DS, Our suggestion has wider implications for research transparency and reproducibility. Consider the implied truth claims associated with any peer-reviewed manuscript. The act of publishing can be seen as a validity assertion: that the truth claims made by the authors are verifiably true, or more weakly that the research assets are verifiable. Unlike a set of conclusions from premises that may be tested for logical validity, research conclusions and claims are not as easily scrutinized and tested. Reviewers trust that methods and results were as written when assets can not be verified directly. Sharing in the manner discussed here would facilitate scrutinizing and testing research projects, and thus potentially increase the reliability of the resulting scientific products.vertical project and unit testing. Building is a call to compile individual components of the project. If a user adheres to the vertical workflow, then R must be able to perform all of the scripted operations. Successfully building a vertical project is loosely analogous to performing unit tests that confirm and validate the process of asset creation. So, compiling a project is a test of the research project and verification its assets. Other researchers can perform the same verification, if the project’s source is shared. We note that vertical does not conduct proper unit tests on functions included in an R package. However, because these projects are R packages, proper unit tests can be easily included .Software developers routinely use version control platforms, such as GitHub and GitLab to coordinate software development across a team of collaborators . We recvertical suggests using Git . For example, we used GitHub as a collaboration tool to create vertical and to write this manuscript (using papaja). Among other features, Git provides functionality similar to track changes in Microsoft Word that allow contributions to be reviewed, accepted, and modified. It makes this process robust even when many collaborators are involved. We also made extensive use of the GitHub issues tab, which is normally used to report bugs or feature requests to a software developer. Many users may find this feature very useful. In our case, we opened issues for discussion and then closed the issues once they were addressed. A side effect is that the GitHub issues tab, and the Git history, may double as a project development narrative, or a lab journaling system preserving issues and solutions for posterity.Research projects can be hosted on GitHub throughout the lifespan of the project to make use its collaboration tools. With this in mind, vertical may be most beneficial to users who already use R. Although our website tutorial is intended for R beginners, it is not a tutorial on the R language. Nevertheless, vertical could be used for pedagogical purposes, like a museum guide offering an orientation to collections in a large museum. For example, an R programming class for psychologists (or statistics/methods course using R) could be structured around the components of a vertical project, such as how to program functions, import and analyze data, write manuscripts, posters, slide decks, and websites in R. Moreover, vertical provides a convenient and well-organized workflow for students to save their work as they learn each component.vertical is a modular open-source tool that can be extended by anyone. We included modules that we think are common, and can incorporate new modules as they are identified and suggested. Users can fork the vertical source code on GitHub, make suggested changes, and submit pull requests for review and inclusion.Future work should also identify commonalities between our suggestion, and other related work such as rrtools : Projects are accessible through the internet at OSF or GitHubvertical project can be minted through OSF or ZenodoDOIs for a A ccessible data is available to approved researchers  through a standardized communications protocol : Projects on GitHub and OSF can be made accessible to a specific set of users, or completely private, if desiredMost data sharing guides emphasize manually uploading heterogeneous data files to a repository . R packages allow that, but also facilitate programmatic access to the data, and therefore are more accessible than methods relying on manual transfer of filesI nteroperable data is described (via metadata and file organization) in a common, openly available, non-proprietary language: R packages describe a strict organization of source files, resulting in a software product that is directly usable in a programming environmentR packages describe a common language for documenting the data, its use, and dependenciesR package (meta)data is human- and machine-readable and in a non-proprietary formatData wrapped in an R package is accessible in other programming environments due to standardized formattingR eusable data are richly described and licensed to facilitate reuse: R packages are described in a standard formatR packages facilitate use of appropriate licensesvertical workflow, adopting R standards during asset creation demands some amount of attention on how research products are curated, stored, documented, and shared. Drawing attention to these details may also serve to increase the reproducibility of our work.Borrowing standards and best practices from software development, such as the R package standard discussed here, may serve to dramatically improve reproducibility. By organizing research assets in a standard format, their reuse will be less time consuming and error-prone. Standard formats also facilitate large-scale meta-scientific investigations (Gorgolewski et al.,


The purpose of the present paper is to analyze, both experimentally and theoretically, the behavior of the polymeric biocomposite generically known as “liquid wood”, trademarked as Arbofill. The experimental part refers to the mechanical performance in tension and compression, having as finality the possibility of using “liquid wood” as a material suitable for the rehabilitation of degraded wooden elements in civil structures . The theoretical part refers to computer simulations regarding the mechanical behavior of “liquid wood” as well as to a theoretical model in the paradigm of motion, which describes the same behavior. This model is based on the hypothesis that “liquid wood” can be assimilated, both structurally and functionally, to a multifractal object, situation in which its entities are described through continuous, non-differentiable curves. Then, descriptions of the behavior of “liquid wood”, both in the Schrödinger-type and in hydrodynamic-type representations at various scale resolutions, become operational. Since in the hydrodynamic-type representation, the constitutive law of “liquid wood” can be highlighted, several operational procedures  will allow correlations between the present proposed model and the experimental data. The obtained results, both practical  and theoretical  indicate that “liquid wood” could be used in the construction industry, as a potential rehabilitation material, but with more development clearly needed. The construction industry is regarded as a major contributor to environmental pollution. It is mainly fossil-fuel driven  and construction sites represent a source of noise and particulate pollution. In particular, the released contaminants  can travel long distances and are harmful both for humans and the environment .Thus, one way to mitigate pollution is to use new, environmentally compliant construction materials which show promise in tackling the pollution issue. Ideally, these materials should be naturally sourced and biodegradable, at least to a certain extent .One way to achieve this is to study and use biocomposite materials. A biocomposite can be defined as a composite material made out of a matrix  reinforced with natural fibers.Biocomposites, although known for several decades, are regarded as being “young”  comparedUnfortunately, when referring to biocomposites in the context of the construction industry, their adoption and use is lagging behind, in contrast to other economic branches. In particular, structural applications, which are essential for the successful employment of biocomposites in the construction industry, are sorely lacking ,9. It caAs a remark, it should be noted that biocomposites represent an entire class of products, with uses in several fields. Tannins, for example, are natural phenolic compounds which have many uses in medical and pharmacological industries, but they are also present in the beverage and clothing industry . AnotherMany other applications are currently studied and much work has been devoted to the application of tannins. Especially when it comes to adhesives, a pressing issue is represented by the need to eliminate toxic formaldehydes from wood adhesive products. Not just tannin, but also urea adhesives, protein adhesives, carbohydrate adhesives, and furanic resins, as well as unsaturated oil adhesives represent promising alternatives. Natural high tech laminates and impregnated paper laminates—also employing tannins—have the potential to deliver alternative products to the industry, with good performance. Bio-based resins, foams and preservatives are also of interest for various applications . MoreoveAll in all, these natural and naturally derived products have the potential to replace “classic”, industrially made, and oftentimes polluting products and associated processes. They are not without issues , but they hold the promise of reducing the environmental impact of the industries in which they may be used.Because the range of biocomposites is relatively large, this article will only refer to a specific polymeric biocomposite material which has shown promise for use in the construction industry—“liquid wood”.As such, the aim of this paper is to explore, both theoretically and practically, the possible use of “liquid wood” as a structural rehabilitation material in the construction industry, in order to facilitate the development and eventual deployment of such materials.Thus, in the present paper, both experimentally and theoretically, the behavior of the polymeric biocomposite generically known as “liquid wood”, trademarked as Arbofill, is analyzed.A biocomposite is a type of material that exhibits a structure similar to the ones found in other types of composites, such as fiber-reinforced polymers, fiberglass etc., but offers biocompatibility. Just like in the case of “classic” composite materials, they can have the role of taking over various efforts that the material is subjected to. They tend to have relatively low density  and a lightweight structure, which offer traction resistance and insulation against heat and noise. Their method of weaving  can be of influence to the overall characteristics of the biocomposite .As a classification, biocomposites are classified according to the type of fibers: wooden and non-wooden fibers.Because wooden fibers are, in one way or another, part of the  wooden mass, they are less popular in the industry  .According to previous statements, “liquid wood” can thus be described as a polymeric biocomposite material, having a matrix made of lignin and other constituents (but mostly organic fibers). From a material constituency point of view, “liquid wood” can be thus viewed as representative for biocomposite products. Obviously, product data sheets exist for all three forms of presentation, which give information about method of processing, method of delivery, and some basic material data . Each of these presentation forms contains varying proportions of lignin, but all of them are biodegradable (up to 100%) and are environmentally friendly ,34,35.“Liquid wood” can be processed much like existing thermoplastics, using well-known manufacturing techniques , hence its “polymeric” trait. While this very trait makes “liquid wood” somewhat different than other composites and biocomposites, it may be viewed as an advantage in lieu of the fact that, for certain types of applications, various objects can be obtained by making use of existing injection machines.As an additional advantage, “liquid wood” can be reused several times over and thus processed and reprocessed, without any loss in its properties .A multitude of tests and observations have been carried out so far on “liquid wood”. These tests approached the topics of: biodegradability , the inf(a) Marine environment degradation—Because “liquid wood” is a up to 100% biodegradable natural material, it is necessary to study its biodegradability and the conditions in which this will occur. Thus, a study was performed on all three presentation forms when they are subjected to the effects of seawater and the microorganisms found in it. It was discovered that “liquid wood” is selective with respect to the absorbed substances and the biofilm developed on the surfaces of samples depends on the surface characteristics. As such, structural degradation is likely to occur and, if “liquid wood” is to be employed in such environments, protection  is recommended .(b)Acidic/Base/UV testing—A rather comprehensive testing of all three presentation forms of “liquid wood”, immersed in water at different temperatures and in the presence of acidic, base and UV environments was carried out. This again had the purpose of determining the behavior of “liquid wood” when subjected to degradation factors. Again, the samples from all three presentation forms showed degradation, so again care must be taken with the conditions in which “liquid wood” is employed .(c)Thermal properties—Because a study of thermal properties was made only on the “liquid wood” trademarked as Arbofill, the other trademarked products—Arboblend and Arboform—were analyzed as well, concerning calorimetric aspects as well as XRD and FTIR procedures. These tests help to further optimize the material injection process .(d)Electrical properties—The scenario mentioned above was repeated for the study of electrical properties. As such, it resulted that both Arboform and Arboblend trademarked commercial products can be considered as electric insulator materials .(e)Biostructure dynamics—It is possible to look at polymeric biocomposite materials as biostructures . Then, it is possible to view such biostructures in terms of fractals and multifractals. Finally, both time and critical velocity particular to any biostructure can be defined . Translated to an engineering point of view, this type of analysis can describe the growth of plant material and thus be used as an estimate of material production  per year .(f)Thermal insulation properties—For a material which has the potential to be used in the construction industry, if appropriate, its thermal insulation properties are usually studied. If they are satisfactory, then said material may be technically considered as a thermal insulator. On a trademarked Arbofill specimen of dimensions 155 × 35 × 35 mm, a reading was made using an Isomet 2114 measuring device  see Fig, with an(g)Fire behavior—Any material that is slated to be used in a building should be tested to the action of fire. A trademarked Arbofill product plate of dimensions 70 × 120 × 10 mm was tested in the scenario of being used as wall cladding, with a violent fire (800–1200 °C) starting next to it see . The “li(h)Rheological properties—Rheology is concerned with the study of flow of solids, but also of non-Newtonian fluids. All “liquid wood” presentation forms were subjected to such testing. The concluding results allow for the determination of optimal viscosity of these materials, in the context of thermal injection .Because the previously mentioned tests were carried out on one, several, or all of the “liquid wood” presentation forms, some of the authors of the present paper carried out further research where it was deemed necessary to obtain data for all three material presentation forms. It should be noted that said research had, as a purpose, the study and uncovering of material properties which are relevant for the possible use of “liquid wood” in civil engineering. These properties represent a departure from the common material properties which are usually encountered in scientific literature . They are listed and briefly discussed below:These tests collectively seem to point out that this material could be used in a structural role in various applications pertaining to the construction industry. Out of all three presentation forms, Arbofill trademark product seems to be the one that has the most suitable properties for use in the construction material. Nevertheless, so far there has been little attempt to employ “liquid wood” in a structurally appropriate manner, much of the research still being relegated to a laboratory environment.In order to assess the suitability of the “liquid wood” Arbofill trademark product for use in building rehabilitation, a scenario was proposed, on which the experiment should rely, in order to replicate an on-site rehabilitation procedure. The idea was that, since “liquid wood” can be thermo-injected, it could be used as a filler material for degraded wooden elements , by cutting out the damaged part of said wooden element. Then, by filling the resulting groove with “liquid wood”, the bearing capacity of the respective beam or column, for example, could be restored. This scenario was replicated in the research team’s laboratory. As a point of note, regarding the  use of “liquid wood” in the construction industry, the material should be accompanied by certificates of approved testing institutes. The experiment presented below only addresses a very specific scenario related to constructions.It is very important to underline the fact that the aim of the experiment is not to study the characteristics of “liquid wood”, but rather the behavior of the timber elements retrofitted with “liquid wood”, in order to determine its viability for use as a repair material.As such, a collection of 12 wooden beams of wood grade class C16 were prepared, in accordance to EN 14081-1. They have the dimensions of 20 × 50 × 800 mm, as recommended by EN 408-2004, and were made ready for testing, by creating a 2 × 2 cm or 2 × 4 cm groove in the mid-section, with the help of a power saw. Nine beams were processed as such, with the remaining three being kept as witness (unmodified) samples. It is acknowledged that this is the absolute minimum of samples that can be tested in order to get appropriate results, according to EN 408-2004. It was decided to use this number of samples as, in previous research, the authors found out that the obtained results are consistent and therefore it would not make a lot of sense to prepare and process a large amount of test beams .Out of the resulting nine beams, six of them, made with the 2 × 2 cm groove in the mid-section, were tested in both tension and compression by bending, in batches of three. The remaining three beams, made with the 2 × 4 cm groove in the mid-section, were tested in tension by bending.Furthermore, in an attempt to improve the adhesion properties of “liquid wood” to regular timber, it was decided to fit the three beams that had a 2 × 4 cm groove with wood screws see a, in var3 of granules.After all preparations were done, the beams were thermo-injected with the product in the grooves. The injection procedure was carried out with the help of a portable thermo-injection machine, which is currently the subject of a pending patent request, No. A/00572/2020, registered with the Romanian State Office for Inventions and Trademarks. The used material volume is estimated at approximately 100 cmThe beams were clamped together in two separate stacks—one containing the beams with 2 × 2 cm groove and one containing the beams with 2 × 4 cm groove, in order to facilitate the injection, which is a continuous working process. The grooves were separated with common baking paper, which has the role of a non-stick medium for “liquid wood”. The baking paper was level cut with the beams, in order to not interfere with the continuity of the injection process see b.An attempt was made to remove the excess “liquid wood”, however this proved unsuccessful, as the material rapidly cools after injection and becomes quite hard. Manual-based attempts to remove the excess material were unsuccessful, but it can be theorized that mechanical grinding may achieve the desired results.After being left to cool and settle for approximately two days, the two beam stacks were unclamped and arranged for structural testing. In order to achieve this, a 600 kN testing machine, model WDW 50 with proprietary acquisition software, was used. The three-point bending test, as previously mentioned, was carried out, with a distance between the supports of 750 mm see a.The testing procedure is fairly straightforward. The beam is settled on supports located at each end of the wooden element. It is then carefully aligned with the loading cell, which applies the force in the middle of the beam, in increments of 10 N/s, until failure. The sensors and the software of the press record the results. Specifically, two parameters are recorded: applied force and resulting displacement.First, the plain wooden beams were tested, in order to extract the control/witness values, which were very close to the standard stipulated ones. They represent the benchmark against which the performance of the rehabilitated wooden elements is evaluated see a.Second, the wooden beams with the 2 × 2 groove were tested in tension and compression by three-point bending see b,c. The Third, the wooden beams with the 2 × 4 groove were tested in tension and compression by three-point bending see d. The saThe overall results are summarized, as an average of values, in the following graphs see .All the tests went according to the initial expectations, with no brittle or unanticipated failures occurring.Almost any material may be studied in a virtual environment. If the material characteristics are known, then they can represent input data in specific simulation software. As such, the studied material can be subjected to various loads, loads that would occur in a projected use, in a specific field. The results obtained following computer simulations can provide important data, for example related to the reliability and performance of a product.In the case of “liquid wood”, it was decided to use Autodesk Inventor virtual simulation environment, in line with the expected employment of “liquid wood” as a thermo—injectable material into existing elements. The simulation software is capable of rendering and analyzing “solids” (3D objects), even when distinct materials are involved (which is in line with the idea of using “liquid wood” as a solution for the repairing of wooden elements).Simulations were made of wooden beams which were rehabilitated with “liquid wood”, in a very similar scenario/setup to the one presented in the practical application.The product was tested in three-point bending at a force of 10 kN. The lateral supports/restrains and the acting force were defined.Then, by “running” the simulation, the resulting output of data were displayed. Furthermore, a colored effort map and an associated value scale were also present see a–c.The obtained values are similar to the experimental ones. This aspect is of particular importance, as it confirms the correspondence of the virtual simulation to the “real” results obtained in the laboratory . Such types of modeling and numerical simulations are recommended, as they are cheaper and faster than carrying out laboratory experiments. They have the potential to provide useful data, as long as the input values reflect expected loads to be encountered in actual product use.(i)A class of models developed on spaces with integer dimension—i.e., differentiable models  ,58.(ii)Another class of models developed on spaces with non–integer dimensions, which is explicitly written through fractional derivatives ,62—i.e.,(iii)Expanding the previous class of models, new developments have been made, based on Scale Relativity Theory, either in the monofractal dynamics as in the case of Nottale , or in tCommon models used to describe the dynamics of biocomposites, are based either on a combination of basic theories, derived especially from physics or on computer simulations ,60,61,62The fractal approach to studying the behavior of “liquid wood” when used in conjecture with regular timber is favorable, as the material exhibits a complex structure. Both in the context of Scale Relativity Theory in the sense of Nottale , as wellSuch a hypothesis may be clarified by considering the following scenario: between two successive interactions of the structural units belonging to any polymeric biocomposite, the trajectory of the structural unit belonging to the polymeric biocomposite is a straight line that becomes non-differentiable in the impact point. Considering that all interaction points form an uncountable set of points, it results that the trajectories of the structural units belonging to the composite become continuous and non-differentiable . Evidently, the reality is much more complicated, taking into account both the diversity of the structural units which compose any polymeric biocomposite and the various interactions between them in the form of double interactions etc. Extrapolating the previous reasoning for any type of polymeric biocomposite, including the “liquid wood” in its various presentation forms, it results that it can be assimilated to a multifractal.All these considerations imply that, in the description of the “liquid wood” dynamics in its various presentation forms, instead of “working” with a single variable  described by a strict non-differentiable function, it is possible to “work” only with approximations of this mathematical function, obtained by averaging them on different scale resolutions. As a consequence, any variable purposed to describe “liquid wood” dynamics in its various presentation forms will perform as the limit of a family of mathematical functions, this being non-differentiable for null scale resolutions and differentiable otherwise . OtherwiSince for a large temporal scale resolution with respect to the inverse of the highest Lyapunov exponent ,66, the Taking into account all of the above, the multifractality expressed through stochasticity, in the description of “liquid wood” dynamics in its various presentation forms, becomes operational in the multifractal paradigm through the Multifractal Theory of Motion. Various applications of this model are given in ,71,72,73The present analysis was directed to the modeling of the behavior of “liquid wood”, more precisely, the tension and compression phenomena. A mathematical model was created considering “liquid wood” as a multifractal object, and analyzing its dynamics in the framework of Scale Relativity Theory, in the form of hydrodynamic descriptions, using various operational procedures (Riccati-type gauges and invariance groups). Finally, the theoretical model was validated by means of the experimental data.Considering “liquid wood” as a multifractal object, in what follows, it is admitted that the motions of the entities of any polymeric biocomposite are described by continuous and non-differentiable curves .Then, the motion equation of the entities of any polymeric biocomposite becomes (for details see ):(1)d^V^In (2), the meaning of the variables and parameters are as follows:f(α) allows the identification of the universality classes in the dynamics of any polymeric biocomposite even when the strange attractors associated to these dynamics have different aspects. For details on the singularity spectrum and its implication on the dynamics of complex systems see [By using the singularity spectrum, the following patterns in the polymeric biocomposite dynamics can be distinguished: monofractal patterns which imply dynamics in homogenous polymeric biocomposites characterized though a single fractal dimension and having the same scaling properties in any time interval; multifractal patterns that include dynamics in inhomogeneous and anisotropic polymeric biocomposites characterize simultaneously by a wide variety of fractal dimensions. Thus tems see ,75,76.For a large temporal-scale resolution with respect to the inverse of the highest Lyapunov exponent ,75, the Many modes of multifractalization through stochasticization processes can be defined. Among the most utilized processes, the Markovian and non-Markovian stochastic processes are found ,76. In wdure see ):(4)d^V^The relations (4) show that, in any point of the motion curves, the local multifractal complex acceleration, In what follows, let it be admitted that the motions of the entities belonging to any polymeric biocomposite are irrotational. Then, the multifractal complex velocity fields from (2) become:f Ψ, see ,75). In f Ψ, see ,75 the mTherefore, for the complex velocity fields (5), the dynamics of any polymeric biocomposite entities are described through Schrödinger type “regimes” at various scale resolutions .Moreover, if it is chosen In (10), By (9), (10), and (11) and using the mathematical procedure from , the motThe Equation (12) corresponds to the multifractal specific momentum conservation law, while Equation (13) corresponds to the multifractal states density conservation law. The multifractal specific potential (14) implies the multifractal specific force:Therefore, for the multifractal complex velocity fields (9), the dynamics of any polymeric biocomposite are described through Madelung-type “regimes” at various scale resolution .Q should consider the “self” nature of the specific momentum transfer of multifractal type. Then, the conservation of the multifractal energy and the multifractal momentum that ensure the reversibility and the existence of the multifractal eigenstates.In this new context, any polymeric biocomposite entities are in a permanent interaction with a multifractal medium through the multifractal specific force (15); all polymeric biocomposites can be identified with a multifractal fluid, the dynamics of which are described by the multifractal Madelung’s equation (see (12)–(14)). The velocity field If the multifractal tensor is considered:Since In the following, this tensor will be “made responsible” for the polymeric biocomposite behavior, when the material is subjected to tension and compression.It is usually accepted the fact that stresses and strains at any point of any type of polymeric biocomposite, are represented, in a tensor form (In relations (20) and (21), Ideally speaking, the best course of action is to find the most general relationship of multifractal type which, when referring to the case of tensors of multifractal type, should be invariant when considering orthogonal groups of multifractal type. In such a context, said relationship should establish a correlation between As such, this general relationship of multifractal type can be written in the shape of a homographical transformation of multifractal type :(22)εk=αThus, if the relation described by Equation (22) is taken to represent a constitutive law of multifractal type, then the parameters As such, a unique state of stress of multifractal type related to a certain state of strain of multifractal type, even as the structure of the polymeric biocomposite is changing, can be described. This is in line with the usual definition for the stresses and strains, which do not depend on any polymeric biocomposite. Consequently, only the constitutive laws of multifractal type depend on the material.Since every type of polymeric biocomposite changes its structure when the deformation process takes place, said change can be reflected in the fact that the matter coefficients In such a context, the “liquid wood” analysis in usual space, is reduced to obtain a relation between the matrix ensemble are used ,52:(25)ωIt is easy to verify the fact that the metric:The three differentiable 1-forms from (25) completely define the coframe in every point of the absolute space. This coframe allows the translation of all geometric properties of the absolute space in the algebraic properties linked to (24) .The simplest property refers to dynamics on the metric geodesics which can be correlated directly into statistical properties and from here the multi-fractalization through stochasticization. In this case, the 1-forms Along this geodesic, (24) becomes a Riccati type equation of multifractal type:The Equation (30) admits a direct integration, with three possible results:Here, For the first case (31) In As it can be observed, there is a significant difference in fractalization between the control system and the “liquid wood” one. For tension a bigger mismatch can be noticed in the fractalization degree, which leads to a lower material performance. This is well in line with the understanding for the role of “liquid wood”, as it does not interact with timber, therefore, a set of fractal interactions that would be present at the contact surface is missing. This non-interaction scenario is the reasoning for the difference in the fractalization and performance mismatch as most of the behavior is an intrinsic one (only for the “liquid wood”). For compression, in the fractal paradigm presented here, most of the interactions are contained within the core of “liquid wood” with reduced interactions at the contact layer see , while fTaking a closer look at the graphs, it is immediately noticeable that the samples behaved far better in compression than in tension. In particular, the performance in compression is very close to the control samples, with a value at breakage rated at approximately 2.7 kN, compared to approximately 3.3 kN for the control ones. This would equate to approximately 81% bearing capacity of the consolidated element, compared to the control one. As an observation, in all the tests performed in compression, “liquid wood” did not suffer any cracks or visible damage, the regular timber always failing first.The performance in tension was lower than what was expected, with a value at breakage rated at approximately 1.2 kN for the retrofitted samples, compared to approximately 3.3 kN for the control ones. This would equate to approximately 36% bearing capacity of the consolidated element, compared to the control one. The obtained results indicate that “liquid wood” can be successfully used in elements where compression is to be expected. However, the results obtained in tension warrant further study and discussion.One of the factors that determined the mediocre performance in tension can be attributed to the lack of interaction between the regular timber and “liquid wood”. It was noticed during material testing that “liquid wood” will not adhere in any meaningful way to timber, even though the two materials are of a polar nature and are biocompatible.The missing adhesion does not seem to stem from improper processing of “liquid wood”, or of the wooden beams. “Liquid wood” is separately converted from a solid state (granules) into a flowing, “liquid” state, followed by thermo-injection and cooling. Similarly, the natural wood was kept and used in optimum laboratory conditions. Rather, there seems to be an interface issue with the two materials, which might be alleviated, for example, by the mixing of heat-activated adhesive ingredients in the “liquid wood” recipe.Nevertheless, it was attempted to rectify this by using wooden screws, as a way of obtaining mechanical adhesion (and thus ensuring the transfer of loads) through the contact between timber, “liquid wood” and the screw flower head. In order to obtain better results in tension, additional steel pieces will have to be used, in order to facilitate the transfer of stresses between the natural wood and “liquid wood”. Although it was noticed that “liquid wood” will adhere to metal, this solution requires further investigations.The better adherence to metal may be explained by previous experiments , which dFinally, it is difficult to compare the results presented in this paper with the ones presented in other manuscripts. The reason is that, to the knowledge of the authors, there are no other studies performed evaluating the performance of “liquid wood”, as a filler material, used for the repair of damaged wooden elements in civil engineering. There are, however, studies regarding mechanical characteristics of “liquid wood”, as a standalone material, in the form of thermo-injected samples subjected to tension and bending. More information regarding “liquid wood” mechanical testing can be found in ,40,43,44The present paper is organized in two main parts: an experimental part and a theoretical part. As such, the following conclusions will be structured based on the organization of the paper.(i)“Liquid wood” seems to be a good option as an eco-friendly, sustainable building material. Its properties appear to be well-suited to use in construction. At the current stage, the material cannot be applied in all situations, but the obtained results are encouraging.(ii)It was decided to employ “liquid wood” in a rehabilitation scenario. Thus, tests both in tension and compression were made, which aim to identify the performance as well as the issues that the polymeric biocomposite might encounter in such situations. The obtained results were displayed in the graphs present at the end of (iii)“Liquid wood” can be used as a repair material, in civil engineering. For compressed elements, like columns, “liquid wood” can be thermo-injected on spot, after proper groove preparation. It is fast to apply, cost-effective, and more environmentally friendly compared to other repair solutions. However, for elements subjected to tension, “liquid wood” requires additional load transfer steel pieces. Additional studies are required in order to determine the optimal solution for load transfer in tension. Once these issues are overcome, “liquid wood” might very well become a material of choice for the rehabilitation of all kinds of building elements.Regarding the experimental aspects, the conclusions are:(i)It was decided to use Autodesk Inventor virtual simulation environment, in line with the expected employment of “liquid wood” as a thermo-injectable material into existing elements. A detailed simulation of a wooden beam which was rehabilitated with Arbofill trademarked product was performed, in a very similar scenario/setup to the one presented in the practical application. Furthermore, it was shown that such simulations can be performed for the other types of product as well. The simulation results confirm the data obtained from the experimental application;(ii)The non-linear behaviors of “liquid wood” are described by means of a theoretical model in the fractal paradigm of motion. This model is based on the hypothesis that “liquid wood” can be assimilated, both structurally and functionally, to a multifractal object. Then, its entities are described through continuous, non-differentiable curves ;(iii)The application of a covariance principle allows the obtainment of the conservation law of the specific momentum. From such a perspective, the description of the dynamics, both in a Schrödinger-type representation and in a hydrodynamic-type representation, at various scale resolutions, becomes operational;(iv)In the hydrodynamic-type representation, at various scale resolutions, a stress-type tensor and its corresponding constitutive laws of multifractal type are presented. In the author’s opinion, this tensor becomes “responsible” for the behavior of “liquid wood” in tension and compression;(v)Using several operational procedures  will allow correlations between stresses and deformations;(vi)The theoretical model was validated by means of data supplied by the experimental application.Regarding the theoretical aspects, the conclusions are:One possible research direction is that the adhesion of “liquid wood” should definitely be studied in detail and methods for improving said adhesion should be explored. Otherwise, “liquid wood” will remain a material confined to a rather narrow palette of applications and uses.Another possible research direction is that the structural properties of “liquid wood” should be further studied. If “liquid wood” should be used as a loadbearing material, then its properties concerning the behavior in tension, compression, shear etc., as well as in various combinations of efforts should be uncovered.One more research direction is that improvement in injection technology (and its on-site employment) and groove preparation should be explored. It may be possible that with advances in both of these previously mentioned aspects, higher rehabilitation performance may be expected, such as better, more uniform groove coverage, and a better “liquid wood” paste layout.


A bibliometric analysis was employed for analyzing the articles published between 2001 and 2021 to show the status of teacher identity research in the past 20 years, research topics on teacher identity, and future research directions. Using the keyword “teacher identity” and filtering data by selecting articles and early access in teaching and education, 848 articles were retrieved. Through production, content, and citation analysis with the help of a bibliometric tool, this study found that teacher identity remained a popular research theme in the academic field over the past 20 years, and its booming production involved many authors, institutions, and sources, and countries. Furthermore, teachers’ “beliefs,” “emotions,” “professional development,” and “context” impacting the construction and reconstruction of teacher identity were the popular topics in teacher identity research, and fundamental issues, including “identity,” “teacher identity,” “professional identity,” “development,” “teacher development,” “beliefs,” and “intersectionality” of teacher identity keep good topics in future research.This study aims to demonstrate a detailed knowledge map of teacher identity research  The teacher identity has played an essential role in education research and teacher education  because There is no doubt that academic publications on the development of teacher identity have been booming over the past 20 years, and they contribute to the development of various aspects of teacher identity research. However, it also becomes increasingly unfeasible to keep pace with everything being published simultaneously. In terms of teacher identity research, there are increasingly more studies on the topics related to it, and several reviews related to some specific aspects of teacher identity have been done. However, there has been a dearth of research on a general and an overall picture of teacher identity research in the past 20 years. A bibliometric analysis adopted in this study will give insights into current research status, research topics, and future research directions in teacher identity. We believe that this study is a valuable tool for practitioners and scholars in the research field of teacher identity. Early researchers interested in teacher identity can provide them with the knowledge needed to begin their research. For experienced teacher identity researchers, this study also serves to better understand the field’s development and promote networking and collaboration between institutions and authors.Under the background of big data, there is a vast amount of literature in various research fields. However, many studies are scattered and hard to be arranged in an organized and transparent way. Consequently, quickly and accurately finding out the critical literature closely related to the research topic has always been perplexing . The stuA bibliometric analysis characterized by a quantitative analysis of the articles published in a specific field  is one oIt is evident that some review studies on the topic of teacher identity have been done, such as teacher identity in the university context , non-natThe present study aims to identify and provide evidence for the state and impact of teacher identity research in the past 20 years. This study analyzed the research topic, publication pattern, research area, authors, highly cited articles, journals, and institutions that contributed most to teacher identity research in the past 20 years. The following questions were designed to plan the review of teacher identity articles in the Web of Science (WoS) database: (1) What was the research status of teacher identity research in the past 20 years? (2) What were the research topics on teacher identity research in the past 20 years? (3) What are the future research directions in teacher identity research? This study offered productivity, citation, and content analysis to answer these questions, such as the number of documents published and citations, co-occurrence of keywords, most relevant sources, authors and institutions, collaboration network, word cloud, and trend topics.In this study, all data were retrieved from the WoS core collection database [including the citation Index Social Sciences Citations Index (SSCI) and Arts and Humanities Citation Index]. WoS is widely used for academic and bibliometric studies as it gives consistent journal coverage of scholarly published articles . The datThis research selected the WoS that contained the data from 2001 to 2021, filtered the core document set according to the title of the study, and exported the 848 data from the selected database. Data collection was divided into three substages. The first was data retrieval. This research chose the WoS as a source of bibliographic information. We selected the articles and early access stored in the SSCI and arts & humanities citation index (AHCI) to analyze research questions. The second substage was data cleaning. We checked articles to avoid data repetition. In the third substage, files were downloaded and compressed. We downloaded 500 references the first time and 348 references the second time. Then, the two article files were compressed for employing bibliometric tools.Nowadays, different tools are available to perform bibliometric studies, including CiteSpace, HistCite, VOSviewer, and CitNetExplorer . This stThe retrieved data in this study were analyzed for bibliometric indicators using the Rstudio software with bibliometric R-package v.4.0.4. First, the bibliometric analysis was activated in the R environment using the R language “install. packages .” The command code opened a biblioshiny web interface on the google chrome browser. Raw data in WoS were imported into the biblioshiny and analyzed. Then, the author described and interpreted the findings indicated by statistics and pictures, which is a crucial part of this research. This study applied relevant authors, institutions, countries, articles, top highly cited publications, keyword co-occurrence, word cloud, thematic map, trend topics, and conceptual structure to answer three different research questions.For the first question: what was the research status of teacher identity in the past 20 years? In this study, a productivity analysis was performed. Preliminary information about data, most relevant authors, institutions and documents, countries dominating the teacher identity study, and the co-citation of authors and sources were presented to show the status of teacher identity research in the past 20 years.The annual production about teacher identity is shown in Teaching and Teacher Education was the essential research front of teacher identity as it published 106 relevant articles and has 38 h-index, 78 g-index, 2.1 m-index, and 6,175 total citations in the past 20 years. Followed by 34 in Teachers and Teaching and 30 in European Journal of Teacher Education, it is proved that the journal Teaching and Teacher Education was far away ahead in all aspects of teacher identity research and the journal Teachers and Teaching and the journal European Journal of Teacher Education were also the two essential research fronts after Teaching and Teacher Education in teacher identity research in the past 20 years. Teacher identity was undoubtedly a hot topic in this study indicated by the fact that increasing more journals devoted themselves to teacher identity research. From Teaching and Teacher Education increased more quickly than the publication in other journals. It coincides with that this journal served as a leading role in teacher identity research in the past 20 years.Reconsidering research on teachers’ professional identity was most wildly cited by having 251 local citations and 1,062 global citations, and it also had 14.6 normalized local citations and 11.79 normalized global citations, which ranked first among all other articles. In this study, ontext, which shapes and reshapes new teachers’ identities: a multi-perspective study written by However, in this overview, the concept of professional identity was hard to agree with or not defined at all. However, A sociocultural approach to understanding teacher identity, agency, and professional vulnerability in a context of secondary school reform (2005), Lasky adopted a sociocultural approach to understanding the dynamic interplay among teacher identity, agency, and context. According to this study, the early influences on teacher identity and the current reform context are the primary mediational systems that shape teacher agency and professional vulnerability. Data from interviews and surveys revealed that the political and social context and early teacher development play an essential role in forming a teacher’s professional identity, and there was a gap between teachers’ expectations and the reality of reform.Through semi-structured interviews, questionnaires, and teachers’ annual reports, this study found that the three main factors influence the construction, deconstruction, and reconstruction of teachers’ professional identities: (1) prior influences, which means teachers’ previous experiences as pupils; (2) initial teacher training and teaching practice, such as teachers’ motivation and general assessment of their professional learning experiences and its influence on the formation of teachers’ identity; and (3) contexts of teaching, which include the classroom practice, school culture, and leadership. This study concluded that teachers’ personal histories and contextual factors of the workplace have a powerful influence on the construction of teachers’ professional identities and suggested that the influence of pre-service programs might be strengthened by providing more opportunities for teachers’ biographical reflection. Teaching and Teacher Education was the most relevant institution contributing to teacher identity research because most of these top most influential documents were published on Teaching and Teacher Education.Moreover, the research suggested that a longitudinal study of how teachers’ identity and agency are mediated over time is essential to explore. Generally, these top local and global cited documents revealed which document had the most significant influence on the perception of a teacher’s professional identity and the production of other works in teacher identity research. Moreover, this table again proves that the journal Co-citation networks can illustrate and analyze the performance of authors and institutions in teacher identity research in the past 20 years.Teaching and Teacher Education had the most intensive network, which shows this journal was most cited and contributed most to the development and progress of teacher identity research. Around the journal Teaching and Teacher Education, intensive co-citation networks among many journals, including Teachers and Teaching European Journal of Teacher Education, and Cambridge Journal of Education are formed. It shows that they were research fronts of teacher identity research and contributed significantly to the progress of teacher identity research. Other sources in the other two clusters indicate that increasingly more authorities paid attention to issues in teacher identity and co-citation network has been formed among them, such as the co-citation network among Language Teaching, System and TESOL Quarterly in the green cluster, the co-citation network among Teacher Education Quarterly, Teaching Education, and Curriculum Inquiry in the blue collection. It is proved that the development of teacher identity research was owned by joint efforts of authors and institutions who contributed to the productivity of teacher identity research.For the second question: What were the research topics on teacher identity in the past 20 years? This study intended to answer it through content analysis. Word Cloud, word growth, thematic map, conceptual structure map, and co-occurrence of author’s keywords were used to present research topics in teacher identity research in the past 20 years.According to status quo of topic groups in teacher identity research. Different colors represent different clusters, and the keywords in the same collection signify high relatedness. A thematic map is divided into four quadrants according to centrality degree and density. The high centrality and high density in the upper right quadrant indicate well-developed motor themes in the research field. As it can be seen, “professional,” “teacher professional identity,” and “development” were the focus and core of the research and had excellent prospects of development.The high density and low centrality in the second quadrant indicate niche themes whose development situation is good but has little influence on the research field. It can be seen that “high education,” “gender,” and “curriculum,” and “professional development,” “teacher professional identity,” and “science education” have formed independent research groups. However, their development prospects in the future were uncertain. In the lower-left quadrant, subject clusters had a low centrality and low density. It indicates that various kinds of “teaching training” “teaching” were marginalized. It means that they were emerging or declining topics. The high centrality and low density in the fourth quadrant signified that “teachers,” “identity,” “discourse analysis,” and “teacher education” were the fundamental themes in education. It can be inferred that their theoretical systems were more complete and mature, and these basic themes may provide the theoretical foundation, rationale, and method to teacher identity study. However, their development prospect is not promising.The biblioshiny for Bibliometrix allows, using the Conceptual Structure Map, to perform multiple correspondence analysis (MCA) to draw a conceptual structure of the field and identify clusters of documents that express common concepts . MCA makTo understand the research topics of teacher identity in the past 20 years, we have identified that the co-occurrence of keywords analysis is an effective tool to provide an overall knowledge structure. Similarly, there were five clusters indicated by five colors in In sum, many keywords were employed in the study of teacher identity. “Teacher identity,” “professional identity,” “teacher education,” and “identity” were central and had the highest co-occurrence with other words. It proves that they were fundamental and core research topics in teacher identity research. In the periphery of the network, there was also co-occurrence of other keywords, like “pedagogy,” “teacher agency,” and “teacher training.” It shows that a broader range of research topics in teacher identity research was explored. For all the differences, we can conclude that “teacher identity,” “identity,” and “professional identity” were primary and core research themes, the “beliefs,” “knowledge,” and “experiences” which influence the construction of teacher identity were also popular research contents in the field of teacher identity research.For the third question: What are the future research directions in teacher identity? With the help of the bibliometric tool, this article used Thematic Evolution and Thematic Trends to predict future research directions.Thematic Evolution and Trend Topics can show hot research topics and future research directions. In Thematic Evolution, different themes are represented by different colors, and the rectangle area indicates the degree of research. In the Trend Topic, the size of nodes indicates the publication number of topics and the time when the topics were popular. According to the size of blue node in This study employed a bibliometric tool to analyze the 20-year development of teacher identity research in a detailed manner. Using the visualization method’s productivity analysis, content analysis, and citation analysis, we acquired information about research status and research topics of teacher identity research in the past 20 years. Moreover, future research directions were predicted to enlighten scholars and researchers interested in the issues related to teacher identity research.First, through the bibliometric analysis in 20 years of development of teacher identity research, this study concluded that teacher identity is an encompassing concept and remains a popular topic in the academic field. Among the numerous research topics, “teacher identity,” “professional identity,” and “identity” were the fundamental and core themes. “Education,” “knowledge,” “beliefs,” “agency,” and “experiences”, which shape that teacher identity was also active and popular topic in the teacher identity research. Teacher identity was an everlasting research theme that involved diverse research topics in the past 20 years.Reconsidering research on teacher’s professional identity (Context, which shapes and reshapes new teachers’ identities: a multi-perspective study (A sociocultural approach to understanding teacher identity, agency, and professional vulnerability in a context of secondary school reform (Teachers and Teacher Education, Teachers and Teaching, and European Journal of Teachers Education were the institutions that had the most significant impact on the study of teacher identity. The United States, United Kingdom, and China were the top three countries that contributed to the development of teacher identity research, and strong collaborations and networks among them were formed. These aspects in the teacher identity research are closely connected as the most cited person contributes to the formation of the countries, institutions, and articles that have considerable influences on teacher identity research. All types of this information benefit greatly to stakeholders in the education field. It may help novice and experienced researchers find the most relevant knowledge about teacher identity research and look for potential cooperators in this field. Moreover, it can provide policymakers with a standard to evaluate the performance of institutions, universities, and authors in teacher identity research.Second, teacher identity studies involved many authors, institutions, sources, and countries, and the cooperation mainly conducted its survey among different authors and institutions in other countries. Douwe Beijaard, Maria Flores, and Sun Lasky played a crucial role in teacher identity research as their documents contributed a lot to the production of other research articles. An increasing number of researchers devoted themselves to teacher identity research indicates that teacher identity research in education has practical significance for many aspects of human society. In terms of the documents, the documents identity , Contextve study , and A sl reform  were theThird, through an analysis of Thematic Evolution and Trend Topic, we can conclude that fundamental and core topics in teacher identity research, including “identity,” “teacher identity,” and “professional identity,” are possible to be paid more attention to in the future, which coincides with the Thematic Evolution in 2017–2021. Besides, recently, the emerging topics, including “development,” “teacher development,” and “beliefs” remained popular topics. Remarkably, the “intersectionality” of teacher identity, which shows the influence of gender, social justice, race, and other sociocultural factors on the construction and reconstruction of teacher identity, is an emerging and promising topic in the future indicated by its high productivity. It can be concluded that these topics have the potential to thrive in teacher identity research in the future. This trend agrees with the postmodern stance on teacher identity because it holds that the construction and reconstruction of teacher identity result from the interaction between the individual and context. Moreover, teacher identity development is a relational phenomenon, and sociocultural factors offer a more practicable perspective on teacher identity development.Although bibliometric methods effectively reveal a research field’s knowledge structure and research topics and can predict future research directions, it is not a substitute for extensive reading. The broad task remains a premise for an in-depth understanding of the research field. Furthermore, in the future, the quantitative method in the teacher identity should be applied more to challenge the psychological feature of methodology in the research. Moreover, an integrated method uses qualitative and quantitative methods in future teacher identity research.As a quantitative study with a bibliometric tool based on the data collected from a database, the focus is on the presentation of pictures and statistics, but the qualitative method for data collection and data analysis is absent. Furthermore, it is a review study providing an overall view of teacher identity research in the past 20 years based on the bibliometric analysis, but it has not delved into a specific aspect of teacher identity to give a thorough investigation. To provide a more extensive understanding of teacher identity, we insist that future research could expand the study to employ a variety of data collection to explore more specific issues in teacher identity research.The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.YZ and PW have shared the equal contributions. PW found the research topic and modified the manuscript several times. YZ collected, analyzed the data, and completed the manuscript under the supervision of PW. Both authors have contributed to the article and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.