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Arun Chaudhari, OjasORCID iD iconorcid.org/0000-0002-4182-5653
Publications (9 of 9) Show all publications
Abrahamsson, C., Rissler, J., Kåredal, M., Hedmer, M., Suchorzewski, J., Prieto Rábade, M., . . . Isaxon, C. (2024). Characterization of airborne dust emissions from three types of crushed multi-walled carbon nanotube-enhanced concretes. NanoImpact, 34, Article ID 100500.
Open this publication in new window or tab >>Characterization of airborne dust emissions from three types of crushed multi-walled carbon nanotube-enhanced concretes
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2024 (English)In: NanoImpact, ISSN 2452-0748, Vol. 34, article id 100500Article in journal (Refereed) Published
Abstract [en]

Dispersing Multi-Walled Carbon Nanotubes (MWCNTs) into concrete at low (<1 wt% in cement) concentrations may improve concrete performance and properties and provide enhanced functionalities. When MWCNT-enhanced concrete is fragmented during remodelling or demolition, the stiff, fibrous and carcinogenic MWCNTs will, however, also be part of the respirable particulate matter released in the process. Consequently, systematic aerosolizing of crushed MWCNT-enhanced concretes in a controlled environment and measuring the properties of this aerosol can give valuable insights into the characteristics of the emissions such as concentrations, size range and morphology. These properties impact to which extent the emissions can be inhaled as well as where they are expected to deposit in the lung, which is critical to assess whether these materials might constitute a future health risk for construction and demolition workers. In this work, the impact from MWCNTs on aerosol characteristics was assessed for samples of three concrete types with various amounts of MWCNT, using a novel methodology based on the continuous drop method. MWCNT-enhanced concretes were crushed, aerosolized and the emitted particles were characterized with online and offline techniques. For light-weight porous concrete, the addition of MWCNT significantly reduced the respirable mass fraction (RESP) and particle number concentrations (PNC) across all size ranges (7 nm – 20 μm), indicating that MWCNTs dampened the fragmentation process by possibly reinforcing the microstructure of brittle concrete. For normal concrete, the opposite could be seen, where MWCNTs resulted in drastic increases in RESP and PNC, suggesting that the MWCNTs may be acting as defects in the concrete matrix, thus enhancing the fragmentation process. For the high strength concrete, the fragmentation decreased at the lowest MWCNT concentration, but increased again for the highest MWCNT concentration. All tested concrete types emitted <100 nm particles, regardless of CNT content. SEM imaging displayed CNTs protruding from concrete fragments, but no free fibres were detected. 

Place, publisher, year, edition, pages
Elsevier B.V., 2024
Keywords
Aerosols; Concrete aggregates; Demolition; Health risks; Light weight concrete; Morphology; Risk assessment; Buildings materials; Cellular lightweight concrete; Cellulars; Concrete types; Construction and demolition waste; Multi-walled-carbon-nanotubes; Nano-enabled building material; Nanosafety; Property; Size ranges; Multiwalled carbon nanotubes (MWCN)
National Category
Civil Engineering
Identifiers
urn:nbn:se:ri:diva-72968 (URN)10.1016/j.impact.2024.100500 (DOI)2-s2.0-85186528171 (Scopus ID)
Funder
EU, Horizon 2020, 814632AFA Insurance, 20010
Note

This study was supported by AFA Insurance ( dnr 20010 ); the European Union's Horizon 2020 research and innovation programme LightCoce (grant agreement No 814632 ); and the Swedish Foundation for Strategic Environmental Research through the research program Mistra Environmental Nanosafety Phase II.

Available from: 2024-04-25 Created: 2024-04-25 Last updated: 2024-04-25Bibliographically approved
Suchorzewski, J., Flansbjer, M., Arun Chaudhari, O. & Williams Portal, N. (2024). Experimental Development and Field Validation of Rock Anchors for Sustainable Onshore Foundations. Paper presented at WindEurope Annual Event 2024 Conference. Bilbao, Spain. 20 March 2024 through 22 March 2024. Journal of Physics, Conference Series, 2745, Article ID 012011.
Open this publication in new window or tab >>Experimental Development and Field Validation of Rock Anchors for Sustainable Onshore Foundations
2024 (English)In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 2745, article id 012011Article in journal (Refereed) Published
Abstract [en]

The development of an innovative rock anchor prototype manufactured using high strength steel sheets produced locally in Sweden is the core of the PROWIND concept. Steel sheets provide a design freedom to easily manufacture complex geometries, which can be advantageous to enhance the shear force transmission in the bond-length segment of the anchor. The underlying challenge of this concept has been to design a solution which meets the design requirements of today and future technological advancements, all while keeping conventional installation practices in mind. The project followed a 4-step development process: (1) concept analysis and modelling, (2) small-scale prototypes testing and (3) large scale lab-validation and lastly (4) field validation. The performance of the developed rock anchor prototype and grouting material was experimentally quantified on both small and large-scale test specimens and also validated in full scale in the field concerning installation process, proof-loading and maintaining the prestress over time. The PROWIND anchors with the end feature with ribbed design have 4-5 times higher load bearing capacity. The experience from the anchor installation proved that the developed grout and anchors are faster and easier to install. The field test in two different geological conditions has proven that the news design is reducing the required anchorage length to just 1 meter. The restressing of anchors is fully possible with the proposed lock-off solution with a nut. All of those contribute to lower costs of installations and possibly longer service-life.

Place, publisher, year, edition, pages
Institute of Physics, 2024
Keywords
Anchors; Bond length; Grouting; High strength steel; Installation; Steel sheet; Complex geometries; Design freedom; Experimental development; Field validation; Force transmission; High-strength steel sheet; Installation practices; Rock anchors; Shear force; Technological advancement; Mortar
National Category
Civil Engineering
Identifiers
urn:nbn:se:ri:diva-73253 (URN)10.1088/1742-6596/2745/1/012011 (DOI)2-s2.0-85193041344 (Scopus ID)
Conference
WindEurope Annual Event 2024 Conference. Bilbao, Spain. 20 March 2024 through 22 March 2024
Note

The research presented in this paper has been financed by The Swedish Energy Agency (Energimyndigheten) within the project PROWIND \u201CPROWIND rock-adaptors for wind power\u201D (51382-1) in years 2022-2024.

Available from: 2024-05-23 Created: 2024-05-23 Last updated: 2024-05-27Bibliographically approved
Pushp, M., Arun Chaudhari, O., Vikegard, P., Blomqvist, P., Lönnermark, A., Ghafar, A. N. & Hedenqvist, M. (2023). Specific heat and excess heat capacity of grout with phase change materials using heat conduction microcalorimetry. Construction and Building Materials, 401, 132915-132915
Open this publication in new window or tab >>Specific heat and excess heat capacity of grout with phase change materials using heat conduction microcalorimetry
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2023 (English)In: Construction and Building Materials, E-ISSN 1879-0526, Vol. 401, p. 132915-132915Article in journal (Refereed) Published
Abstract [en]

Microencapsulated phase-change-materials (PCMs) incorporated in cementitious grout can be used as a source of energy in an underground thermal energy storage system. Differential scanning calorimetry (DSC) is a widely used technique to measure the latent heat or specific heat of PCM-embedded cementitious materials. However, using milligram sample sizes (as required by DSC) of a cementitious material fails to represent the actual scale of cementitious components. This is the reason why, in the present paper, non-isothermal heat conduction microcalorimetry (MC) was evaluated as a tool for determining the thermal properties of PCM-embedded grout as well as pure PCM (three PCMs were used). An MC experimental protocol (using both single and 5–6 temperature cycles) was developed and used to measure latent heat and melting and crystallization temperatures, which were in good agreement with those reported for pure PCMs by the producers. In addition, the specific heats of the PCM-containing grout also agreed with measurements using the hot disk technique. Overall, the results show that the MC technique can be used as a potential standard method in determining thermal processes in complex systems, such as in PCM-embedded cementitious systems, where a large sample size is needed to represent the material.

National Category
Energy Engineering
Identifiers
urn:nbn:se:ri:diva-66941 (URN)10.1016/j.conbuildmat.2023.132915 (DOI)
Note

This article is part of a project that has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 727583.

Available from: 2023-09-21 Created: 2023-09-21 Last updated: 2023-09-21Bibliographically approved
Zirgulis, G., Javadi, H., Arun Chaudhari, O., Ghafar, A. N., Fontana, P., Sanner, B., . . . Shuster, M. (2023). Temperature evolution around four laboratory-scale borehole heat exchangers grouted with phase change materials subjected to heating–cooling cycles: An experimental study. Journal of Energy Storage, 74, Article ID 109302.
Open this publication in new window or tab >>Temperature evolution around four laboratory-scale borehole heat exchangers grouted with phase change materials subjected to heating–cooling cycles: An experimental study
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2023 (English)In: Journal of Energy Storage, ISSN 2352-152X, E-ISSN 2352-1538, Vol. 74, article id 109302Article in journal (Refereed) Published
Abstract [en]

This article presents the experimental results from a unique laboratory test-setup used to comparative study of heat transfer conditions in borehole heat exchangers with different grouts under a controlled environment. The work was part of a larger, EU-funded project on advanced materials for borehole heat exchangers pipes and grout, GEOCOND. Four grout columns with different formulations were cast and tested under cyclic heating and cooling. One grout column was cast using high thermal conductivity grout; two columns were cast from high thermal conductivity grout with microencapsulated phase change material (MC-PCM) and one with shape-stabilised phase-change material (SS-PCM). The objective of the test was to comparatively evaluate performance of the borehole heat exchanger under a cyclic temperature regime and to investigate if the selected phase change materials (PCM) embedded in grout can be activated by cyclic heating and function steadily. Twenty-five heating-cooling cycles were performed, each lasted 24 h. The results showed clear cooling delay in grouts containing PCM associated with the crystallization heat release. The cooling delay was better expressed in grouts with SS-PCM. The PCM related cooling delay was stable throughout all the cycling in SS-PCM containing grouts, however, the effect vanished in grouts with MC-PCM. © 2023 The Authors

Place, publisher, year, edition, pages
Elsevier Ltd, 2023
Keywords
Boreholes; Cooling; Geothermal energy; Grouting; Mortar; Thermal conductivity; Borehole heat exchangers; Cyclic heating; Heating-cooling cycle; High thermal conductivity; High thermal conductivity grout; Laboratory test; Shallow geothermal energies; Shape stabilized phase change material; Temperature evolution; Test setups; Phase change materials
National Category
Energy Engineering
Identifiers
urn:nbn:se:ri:diva-67699 (URN)10.1016/j.est.2023.109302 (DOI)2-s2.0-85174685922 (Scopus ID)
Funder
EU, Horizon 2020, 727583
Note

This work received funding from the European Union's Horizon 2020 research and innovation programme [grant agreement number No 727583 ].

Available from: 2023-11-06 Created: 2023-11-06 Last updated: 2023-11-16Bibliographically approved
Zirgulis, G., Nejad Ghafar, A. & Arun Chaudhari, O. (2022). Development of dynamic grouting under laboratory and field conditions. Geomechanics and Tunneling, 15(5), 535-539
Open this publication in new window or tab >>Development of dynamic grouting under laboratory and field conditions
2022 (English)In: Geomechanics and Tunneling, ISSN 1865-7362, E-ISSN 1865-7389, Vol. 15, no 5, p. 535-539Article in journal (Refereed) Published
Abstract [en]

When it comes to underground structures, water ingress from the surrounding formations leads to several environmental, economic and sustainability issues. To obtain the sealing, the grouting of rock fractures is done. Today, in the grouting operations, which are commonly conducted in almost all the tunnel and subsurface infrastructure projects, the pressure applied is static. This type of applied pressure might be suitable for the large fracture apertures > 100 μm, but it has been acknowledged that it is difficult to obtain sufficient penetration through smaller apertures, where filtration of cement particles starts to occur. Research is already done to overcome this issue by applying dynamic grouting pressure instead of static. It was proved that this approach erodes the formed filter cakes and improves grout penetrability in fractures below 100 μm. This research focuses on low-frequency rectangular pressure impulse as an alternative to other methods. The goal is to improve grout spread in micro-fractures (especially in apertures < 70 μm). During the investigation, a prototype dynamic injection equipment was built and tested under laboratory conditions. The 4 m variable aperture long slot (VALS) was used in the experiments to simulate rock fractures. The test showed better grout penetrability using dynamic pressure approach. At the current time of writing this article, preparation works are done for field test of prototype equipment at SKB Hard Rock Laboratory (HRL) at Äspö, Sweden. 

Place, publisher, year, edition, pages
Ernst und Sohn, 2022
Keywords
Conventional tunneling, dynamic grouting, filtration erosion, grout penetrability, Grouting, Innovative procedures/test techniques, rock fractures, Concrete construction, Fracture, Mortar, Rocks, Sustainable development, Underground structures, Field conditions, Filtration erosions, Innovative procedure/test technique, Laboratory conditions, Test techniques, Water ingress
National Category
Geotechnical Engineering
Identifiers
urn:nbn:se:ri:diva-61211 (URN)10.1002/geot.202200023 (DOI)2-s2.0-85139241886 (Scopus ID)
Available from: 2022-12-05 Created: 2022-12-05 Last updated: 2023-10-09Bibliographically approved
Javadi, H., Urchueguía, J. F., Badenes, B., Mateo, M. Á., Nejad Ghafar, A., Arun Chaudhari, O., . . . Lemus, L. G. (2022). Laboratory and numerical study on innovative grouting materials applicable to borehole heat exchangers (BHE) and borehole thermal energy storage (BTES) systems. Renewable energy, 194, 788-804
Open this publication in new window or tab >>Laboratory and numerical study on innovative grouting materials applicable to borehole heat exchangers (BHE) and borehole thermal energy storage (BTES) systems
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2022 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 194, p. 788-804Article in journal (Refereed) Published
Abstract [en]

In this study, a laboratory-scale prototype of a borehole field has been designed and built to assess various innovative grouting products in a fully controlled environment. Three novel grout formulations are developed and evaluated: enhanced grout, a mixture of enhanced grout and microencapsulated phase change material, and a mixture of enhanced grout and shape stabilized phase change material. The objective is to evaluate the enhancement in their thermal properties (i.e., thermal conductivity and thermal energy storage capacity) compared to those using a commercial reference grout. Besides, three-dimensional numerical modeling is performed to provide a better understanding of the heat transfer and phase transition inside and outside the grout columns and to study the capability of the developed grouts to be used in a borehole heat exchanger or as borehole thermal energy storage system. To the best of the authors' knowledge, there have been just a few numerical studies on using phase change materials inside borehole heat exchangers to assess thermal energy storage applications. The experimental and numerical results showed much higher efficiency of the grout developed with a high thermal conductivity than the reference grout in terms of heat transfer in both the grout column and the surrounding sand. Furthermore, the results indicated the noticeable influence of the microencapsulated phase change material's presence in the grout formulation in terms of heat absorption/storage during the phase transition (from solid to liquid). However, it is concluded that reengineering shape stabilized phase change material should be conducted to make it more appropriate for thermal energy storage applications.

National Category
Infrastructure Engineering
Identifiers
urn:nbn:se:ri:diva-59880 (URN)10.1016/j.renene.2022.05.152 (DOI)2-s2.0-85131566138 (Scopus ID)
Note

This article is part of a project that has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 727583.

Funding for open access charge: AYUDAS A INVESTIGADORES PREDOCTORALES PARA LA PUBLICACIÓN DE ARTÍCULOS DE INVESTIGACIÓN EN ABIERTO (PAID-12-21) by Universitat Politècnica de València.

Available from: 2022-08-08 Created: 2022-08-08 Last updated: 2023-06-02Bibliographically approved
Arun Chaudhari, O., Ghafar, A., Zirgulis, G., Mousavi, M., Fontana, P., Pousette, S. & Ellison, T. (2021). A Practical Construction Technique to Enhance the Performance of Rock Bolts in Tunnels. In: Proc of ICTC 2021: . Paper presented at ICTC 2021: 15. International Conference on Tunnel Construction Date and location – December 16-17, 2021 in Barcelona, Spain Conducted online due to pandemic)..
Open this publication in new window or tab >>A Practical Construction Technique to Enhance the Performance of Rock Bolts in Tunnels
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2021 (English)In: Proc of ICTC 2021, 2021Conference paper, Published paper (Refereed)
Abstract [en]

In Swedish tunnel construction, a critical issue that has been repeatedly acknowledged is corrosion and, consequently, failure of the rock bolts in rock support systems. The defective installation of rock bolts results in the formation of cavities in the cement mortar that is regularly used to fill the area under the dome plates. These voids allow for water-ingress to the rock bolt assembly, which results in corrosion of rock bolt components and eventually failure. In addition, the current installation technique consists of several manual steps with intense labor works that are usually done in uncomfortable and exhausting conditions, e.g., under the roof of the tunnels. Such intense tasks also lead to a considerable waste of materials and execution errors. Moreover, adequate quality control of the execution is hardly possible with the current technique. To overcome these issues, a nonshrinking/ expansive cement-based mortar filled in the paper packaging has been developed in this study which properly fills the area under the dome plates without or with the least remaining cavities, ultimately that diminishes the potential of corrosion. This article summarizes the development process and the experimental evaluation of this technique for the installation of rock bolts. In the development process, the cementitious mortar was first developed using specific cement and shrinkage reducing/expansive additives. The mechanical and flow properties of the mortar were then evaluated using compressive strength, density, and slump flow measurement methods. In addition, isothermal calorimetry and shrinkage/expansion measurements were used to elucidate the hydration and durability attributes of the mortar. After obtaining the desired properties in both fresh and hardened conditions, the developed dry mortar was filled in specific permeable paper packaging and then submerged in water bath for specific intervals before the installation. The tests were enhanced progressively by optimizing different parameters such as shape and size of the packaging, characteristics of the paper used, immersion time in water and even some minor characteristics of the mortar. Finally, the developed prototype was tested in a lab-scale rock bolt assembly with various angles to analyze the efficiency of the method in real life scenario. The results showed that the new technique improves the performance of the rock bolts by reducing the material wastage, improving environmental performance, facilitating and accelerating the labor works, and finally enhancing the durability of the whole system. Accordingly, this approach provides an efficient alternative for the traditional way of tunnel bolt installation with considerable advantages for the Swedish tunneling industry.

Keywords
Corrosion, durability, mortar, rock bolt
National Category
Infrastructure Engineering
Identifiers
urn:nbn:se:ri:diva-57528 (URN)
Conference
ICTC 2021: 15. International Conference on Tunnel Construction Date and location – December 16-17, 2021 in Barcelona, Spain Conducted online due to pandemic).
Available from: 2022-01-05 Created: 2022-01-05 Last updated: 2023-06-02Bibliographically approved
Arun Chaudhari, O., Alkhaffaf, L., Khalil, H. & Fontana, P. (2021). Effect of Phase Transition Temperatures of the Phase Change Material on Hydration and Mechanical Properties of Cement Paste. In: Proc of INTERNATIONAL CONFERENCE ON“CEMENT - BASED MATERIALS TAILORED FOR A SUSTAINABLE FUTURE: . Paper presented at INTERNATIONAL CONFERENCE ON “CEMENT - BASED MATERIALS TAILORED FOR A SUSTAINABLE FUTURE" IN HONOUR OF PROF. SURENDRA P. SHAH AND PROF. TURAN ÖZTURAN May 27-29, 2021 • ISTANBUL / TURKEY (pp. 85-93).
Open this publication in new window or tab >>Effect of Phase Transition Temperatures of the Phase Change Material on Hydration and Mechanical Properties of Cement Paste
2021 (English)In: Proc of INTERNATIONAL CONFERENCE ON“CEMENT - BASED MATERIALS TAILORED FOR A SUSTAINABLE FUTURE, 2021, p. 85-93Conference paper, Published paper (Refereed)
Abstract [en]

In recent years, the use of Phase Change Materials (PCMs) in cementitious materials have become of vital importance due to their ability to absorb and release the heat and promote thermal comfort in building applications, which is a requirement for saving energy and sustainable infrastructure. The presented study aimed at investigating the PCMs of different phase transition temperatures in cementitious system and their influence on hydration and mechanical properties of the system. In this study, three PCMs with different phase transition temperatures (24 °C, 29 °C and 58 °C) were incorporated into cement paste at various dosages. The mechanical and rheological properties of the cement pastes were evaluated using compressive strength, density, and slump flow measurement methods. In addition, isothermal calorimetry and semi-adiabatic calorimetry measurements were used to elucidate hydration attributes of the cement paste. The results reveal that both the phase transition temperature of PCM and its amount have a crucial effect on the properties of the cement-based material. Especially, the high phase transition temperature (58 °C) PCM has enhanced the heat of hydration and stabilized the temperature during the cement hydration, that resulted in higher compressive strength of the cementitious system. Whereas ambient phase transition temperature (24 °C and 29 °C) PCMs have negatively influenced the rate of strength development of the cementitious system. The slow rate of strength development was found to be attributed to reduction in heat of hydration, which was confirmed through the calorimetry studies.

Keywords
phase change material, cement hydration, Portland cement, concrete, energy storage
National Category
Building Technologies
Identifiers
urn:nbn:se:ri:diva-57527 (URN)
Conference
INTERNATIONAL CONFERENCE ON “CEMENT - BASED MATERIALS TAILORED FOR A SUSTAINABLE FUTURE" IN HONOUR OF PROF. SURENDRA P. SHAH AND PROF. TURAN ÖZTURAN May 27-29, 2021 • ISTANBUL / TURKEY
Available from: 2022-01-05 Created: 2022-01-05 Last updated: 2023-06-02Bibliographically approved
Berktas, I., Chaudhari, O., Ghafar, A. N., Menceloglu, Y. & Okan, B. (2021). Silanization of SiO2 decorated carbon nanosheets from rice husk ash and its effect on workability and hydration of cement grouts. Nanomaterials, 11(3), Article ID 655.
Open this publication in new window or tab >>Silanization of SiO2 decorated carbon nanosheets from rice husk ash and its effect on workability and hydration of cement grouts
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2021 (English)In: Nanomaterials, E-ISSN 2079-4991, Vol. 11, no 3, article id 655Article in journal (Refereed) Published
Abstract [en]

Rice husk ash (RHA) having a porous sructure and a high amount of amorphous silica nanoparticles (4 nm) decorated on the surface of carbon nanosheets is a suitable and cheap candidate for the use of a grout additive. In this study, neat RHA and functionalized RHA (f-RHA) with three different loadings were successfully incorporated into the cement-bentonite based grouts by adjusting the water to cement ratio. The workability of the developed grouts having RHA-based additives was analyzed in terms of bleeding, density, flow spread, and Marsh cone time. Additionally, the thermal and prolongation of hydration performances of the cementitious grout were enriched by successful attachment of amino-silane functional groups on the RHA surface. The heat of hydration performances of RHA and functionalized RHA introduced cementitious grout composite were assessed by isothermal calorimetry tests, and especially the kinetics of hydration was increased by the addition of RHA. The presence of amino silane groups in f-RHA intensified the heat adsorption by reacting with cement constituents, and thus resulted in the retardation and reduction in the heat flow. Therefore, using an amino-silane coupling agent increased the induction period and hindered the heat of hydration compared to the reference grout. On the other hand, the incorporation of RHA and f-RHA into the cement matrix did not affect the thermal conductivity of the grouts. © 2021 by the authors. 

Place, publisher, year, edition, pages
MDPI AG, 2021
Keywords
Cementitious grout composite, Hydration performance, Rice husk ash, Thermal properties
National Category
Geotechnical Engineering
Identifiers
urn:nbn:se:ri:diva-52605 (URN)10.3390/nano11030655 (DOI)2-s2.0-85102032025 (Scopus ID)
Note

Funding details: 727583; Funding text 1: This project is supported by Horizon 2020 project of GEOCOND. The grant number is 727583.

Available from: 2021-03-19 Created: 2021-03-19 Last updated: 2023-06-02Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-4182-5653

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