K. Labropoulos - Academia.edu (original) (raw)

Papers by K. Labropoulos

Buildings, Mar 16, 2024

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Within the framework of the collaboration between Princeton University, the National Technical Un... more Within the framework of the collaboration between Princeton University, the National Technical University of Athens, and Bogazici University, the present work deals with material analyses of small samples taken from Hagia Sophia, a sixth century masonry edifice, in Istanbul, Turkey, coordinated with structural studies to provide insight to the structure's ability to withstand seismic loads. The present work is based on the methods of X-ray diffraction analysis and thermogravimetric analysis performed both on the samples themselves and on their fractions after a physical separation. The results account for a possible technology of a pozzolanic mortar, where one part per volume lime was mixed with 3 parts of aggregate (crushed brick fragments, sea sand, and fine pozzolanic sand). However, up to now, analytical techniques cannot provide directly technology information, let alone on the physicochemical interactions among the constituents of historic walls, as in the case under study...

Measuring, Monitoring and Modeling Concrete Properties

... The spectra reveal the presence of either hydraulic lime or poz-zolana admixed with aerial li... more ... The spectra reveal the presence of either hydraulic lime or poz-zolana admixed with aerial lime, rich in CSH. ... of mortars from traditional build-ings in seismic areas, PACT Revue du groupe europeen d'etudes pour les techniques phy-siques, chimiques, biologiques et ...

The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2013

Sustainable maintenance and preservation of cultural heritage assets depends highly on its resili... more Sustainable maintenance and preservation of cultural heritage assets depends highly on its resilience to external or internal alterations and to various hazards. Risk assessment of a heritage asset's can be defined as the identification of all potential hazards affecting it and the evaluation of the asset's vulnerability (building materials and building structure conservation state).Potential hazards for cultural heritage are complex and varying. The risk of decay and damage associated with monuments is not limited to certain long term natural processes, sudden events and human impact (macroscale of the heritage asset) but is also a function of the degradation processes within materials and structural elements due to physical and chemical procedures. Obviously, these factors cover different scales of the problem. The deteriorating processes in materials may be triggered by external influences or caused because of internal chemical and/or physical variations of materials properties and characteristics. Therefore risk evaluation should be dealt in the direction of revealing the specific active decay and damage mechanism both in mesoscale [type of decay and damage] and microscale [decay phenomenon mechanism] level. A prerequisite for risk indicators identification and development is the existence of an organised source of comparable and interoperable data about heritage assets under observation. This unified source of information offers a knowledge based background of the asset's vulnerability through the diagnosis of building materials' and building structure's conservation state, through the identification of all potential hazards affecting these and through mapping of its possible alterations during its entire lifetime. In this framework the identification and analysis of risks regarding degradation processes for the development of qualitative and quantitative indicators can be supported by documentation protocols. The data investigated by such protocols help identify the parameters needed for the assessment of the preservation state of a monument and its monitoring through its entire lifetime. The main tool for detecting these indicators is a diagnostic methodology based on appropriate standards that reveals the actual degradation processes responsible of the asset's vulnerability. It is very important that the integration between the material's diagnosis and the overall documentation is taken into consideration in order to identify the required levels of protection and preventive conservation for heritage assets depending on the most frequent local risks. The ranging of risks is therefore necessary according to their importance in each area. Documentation protocols provide with a specific diagnostic tool for materials characterization, decay diagnosis, evaluation process of former conservation materials and interventions, standard procedures for monitoring and control as well as data documentation based on specific guidelines and standards. Implementation and analysis of a "standardised" diagnostic study will reveal the main risks due to degradation processes affecting the heritage asset to be subsequently recorded in order to result into risk indicators. The development of risk indicators regarding degradation processes is the basic step towards uptaking efficient management, preventive conservation and strategic planning for heritage assets against various threats. These risk indicators could be further elaborated according to the activities of inspection, diagnosis and intervention works, offering scientific support to the decision making process for cultural heritage preventive conservation and overall protection.

Smart Sensor Phenomena, Technology, Networks, and Systems Integration 2012, 2012

ABSTRACT The church of Hagia Sophia in Istanbul is a world heritage monument that epitomizes the ... more ABSTRACT The church of Hagia Sophia in Istanbul is a world heritage monument that epitomizes the byzantine ecclesiastic architecture. The church is decorated with mosaics from various historic periods. The preservation state of the mosaics is of high importance. In this study, non-destructive techniques (ground penetrating radar, infra-red thermography, fibreoptics microscopy) were employed on south upper gallery mosaic areas. The main aim of this on-site investigation was the evaluation of the preservation state of the mosaics and the previous interventions (materials characterization and decay diagnosis) in order to assess the performance of previous conservation/restoration interventions, as well as to verify the presence of mosaics in layers below the external plaster surfaces. Results indicated that is indeed possible to locate the grid of rendered mosaics. Regarding the preservation state of the mosaics, it was indicated that the main environmental decay factors were the high relative humidity levels with co-action of salt damp as well as the air pollutants. Moreover, it was revealed that previous incompatible restoration/conservation interventions have often accelerated the mosaics' degradation processes. Using non-destructive techniques it was possible to identify areas where the mosaic materials (tesserae and mortars) presented decay problems and in addition identify sub-layers that pose risk of detachment or decay intensification. In this way, NDT can contribute to the development of a strategic planning for mosaics conservation, protection and revealing.

MRS Proceedings, 1995

The decay processes in monuments, considered as interaction between building materials and enviro... more The decay processes in monuments, considered as interaction between building materials and environmental factors, presents a specific interest in the case of marine environment (Mediterranean), in mild climatic conditions. An extended monument, like the Medieval Fortress of Rhodes could be a characteristic example. It is constructed by a susceptible to salt decay biocalcareous porous stone which suffers mainly from salt crystallisation and hard carbonate crusts formation.

Lecture Notes in Computer Science, 2012

ABSTRACT Abstract The world’s cultural heritage is frequently subject to misuse and vandalism by ... more ABSTRACT Abstract The world’s cultural heritage is frequently subject to misuse and vandalism by the general public. However, while a lack of knowledge, unawareness of the heritage values and the importance of its preservation are demonstrated in the real “tangible world” of historic monuments and sites, the general public, and especially youth, have proved to be sophisticated visitors to “intangible” virtual reality. The Euromed Heritage 4 Project “ELAICH” (Educational Linkage Approach In Cultural Heritage) provided an e-tool for increasing “awareness of the importance of Cultural Heritage ... and its conservation by ... the general public” - the eLAICH Educational Toolkit, which was developed and made accessible to the general public through the eLAICH e-learning platform, using Learning Management System (LMS), Content Management System (CMS) and Information and Communication Technologies (ICT). This paper provides an overview of the project’s organization, computerized support, and e-results.

Fracture and Failure of Natural Building Stones

ABSTRACT The decay of materials is a function of intrinsic and extrinsic factors. The intrinsic f... more ABSTRACT The decay of materials is a function of intrinsic and extrinsic factors. The intrinsic factors are related to the material itself, and include the type of the material, its properties and its microstructure. The extrinsic factors refer to the effect that the environment has on the material and can be generally divided into factors related to the atmosphere and factors related to the usage of the material respectively. Salt decay is arguably the most significant deteriorating mechanism for monuments and buildings in marine environment. Salts migrate in the form of solution through the complex capillary system of porous stones towards the surface. Crystallization of soluble salts may appear in the form of efflorescences or subefflorescences. The assessment of the susceptibility of stone to salt decay can be accomplished either through the calculation of crystallization pressure or through the determination of the most probable scenario as determined by an energetic evaluation. Non-destructive techniques can also be used in situ to assess the susceptibility of the building materials and to assess the effectiveness of interventions.

Journal of Cultural Heritage, 2013

Documentation on cultural heritage assets is an indispensable part of an overall strategy for cul... more Documentation on cultural heritage assets is an indispensable part of an overall strategy for cultural heritage protection. Sustainable conservation and management is not feasible without a systematic data collection and registration that identifies the history of the monument, its architectural attributes, preservation state and its possible alterations during its entire lifetime. Integrated documentation protocols for data collection and organizing are developed that built upon certain documentation procedures, encompassing all parameters relating to the monument. These were developed based on the current documentation methodologies survey, revealing the prerequisite main attributes of such protocols, and the need to incorporate quality control principles. Their structure follows a three-level classification of data that reflect the overall information to be documented at an increasing complexity. They constitute a solid basis for any knowledge-based decision making process to establish priorities of cultural heritage protection, through the use of specific necessity indices that utilize the information collected and stored.

Construction and Building Materials, 2013

h i g h l i g h t s NDTs are valuable for the protection of built cultural heritage. NDTs can ass... more h i g h l i g h t s NDTs are valuable for the protection of built cultural heritage. NDTs can assess the preservation state of materials and structures. NDTs can evaluate the efficiency of restoration/protection interventions. NDTs are integrated into information systems for effective planning of interventions.

In this work, diagnostic strategies involving the application of in-situ non-destructive testing ... more In this work, diagnostic strategies involving the application of in-situ non-destructive testing and in-lab techniques, GIS modeling and analysis operations were utilized for planning of materials and conservation interventions at the walls of Erimokastro Acropolis Rhodes. Polarized optical microscopy mercury porosimetry, scanning electron microscopy, determination of total soluble salt content, fibre-optic microscopy, ultrasonics and infra-red thermography were used to characterize the building materials and their ...

The decay of materials is a function of intrinsic and extrinsic factors. The intrinsic factors ar... more The decay of materials is a function of intrinsic and extrinsic factors. The intrinsic factors are related to the material itself, and include the type of the material, its properties and its microstructure. The extrinsic factors refer to the effect that the environment has on the material and can be generally divided into factors related to the atmosphere and factors related to the usage of the material respectively. Salt decay is arguably the most significant deteriorating mechanism for monuments and buildings in marine environment. Salts migrate in the form of solution through the complex capillary system of porous stones towards the surface. Crystallization of soluble salts may appear in the form of efflorescences or subefflorescences. The assessment of the susceptibility of stone to salt decay can be accomplished either through the calculation of crystallization pressure or through the determination of the most probable scenario as determined by an energetic evaluation. Non-des...

Journal of materials science & engineering, 2012

Ground penetrating radar was used to assess the decay state of the mosaics at the south upper gal... more Ground penetrating radar was used to assess the decay state of the mosaics at the south upper gallery of Hagia Sophia, Istanbul. These mosaics were plastered during the Ottoman period of the monument, but during recent conservation interventions part of the plaster layer has been removed. It has been revealed that cohesion problems may be encountered with the preserved mosaic at the perpendicular junction of two arches. In another area, GPR was employed to reveal the presence of underlying mosaics being below the plaster layer. There have been observed void spaces below this layer, indicating possible cohesion problems that need to be taken into consideration in case of future removal of the plaster. In addition, the Empress Zoe mosaic was scanned, verifying good overall cohesion and homogeneity of the mosaic and the substrate structure but also that there exist restored areas with new base mortar and tesserae, confirming historic data.

Non-destructive testing is used for many applications in the cultural heritage protection field. ... more Non-destructive testing is used for many applications in the cultural heritage protection field. In this study three such sensing techniques, portable digital microscope, infrared thermography, georadar were used for the in site investigation of the ISIA building at the historic center of Florence. This work was a sub-action of a research program called MEDNETA; “MEDNETA- Mediterranean cultural network to promote creativity in the arts, crafts and design for communities’ regeneration in historical cities”.

Singh/Innovative, 2012

This study proposes a fundamental microstructural/rheological model for agar gels that describes ... more This study proposes a fundamental microstructural/rheological model for agar gels that describes their dynamic rheological behavior during gelation. The concept of a sigmoidal type temperature dependence of the monomeric friction coefficient, ξ o , of the agar molecule is introduced to describe the increase of relaxation times of the agar molecules with decreasing temperature. At high temperatures (close to 373 K), the model behaves like a dilute solution of flexible polymers. At low temperatures (close to 273 K) contributions from an equilibrium modulus term are predominant. Dynamic rheology was employed to study the applicability of this model for agar gels. Gelation curves were obtained experimentally for various agar concentrations and cooling rates were fitted successfully to the theoretical model predictions.

Computers in Railways X, 2006

The preventive maintenance of rails is necessary for safe, successful and economical railway perf... more The preventive maintenance of rails is necessary for safe, successful and economical railway performance and operations. Rolling contact fatigue (RCF) is one of the main issues that concern the head of the railway. Progressively, RCF defects can propagate inside the material with the risk of damaging the rail, and thus they need to be monitored, categorized, evaluated, and treated through a comprehensive maintenance system. In a previous work with the Athens Metro, an innovative monitoring system was developed based on the capability of non-destructive techniques, such as IR thermography, to inspect and identify defects at early stages and reveal the activated paths of fracture (Moropoulou A., Avdelidis N., et al. Thermosense XXVII, 5782, 371-378, 2005). In the present work with the Athens Piraeus Electric Railways S.A. this system is further integrated into a complete system consisting of three components. The surveillance component identifies the rail defects and includes non-destructive techniques, such as visual inspection, infra-red thermography, ultrasonics, fiber optics microscopy, and ACFM. The data management component receives information from the various defect identification techniques, categorizes them and stores them for further use. The defect warning component uses risk indices such as defect level indices, defect extent indices, and risk threshold values, in order to evaluate the significance of the observed defects. All three components are part of a decision making system that monitors the development of defects, warns for significant threats and schedules rail maintenance.

Journal of Cultural Heritage, 2013

Carbohydrate Polymers, 2002

A theoretical rheological model for agar gels is proposed, based on the bead and spring model for... more A theoretical rheological model for agar gels is proposed, based on the bead and spring model for linear flexible random coils and the model for crosslinked polymers. The model introduces the concept of a temperature dependence of the monomeric friction coefficient, ζ0, of the agar molecule. The model has a random coil-like behavior at high temperatures (close to 373K), and contributions from a three-dimensional network at low temperatures (close to 273K). A proposed temperature dependence of the net association rate allows the calculation of the fraction of associated molecules as a function of time and temperature. The proposed model predicts the gelation behavior of agar gels utilizing time–temperature data (cooling curves).

Cement and Concrete Research, 2004

Traditional pozzolanic mortars such as those from Rhodes, Greece, or Hagia Sophia, Turkey, reveal... more Traditional pozzolanic mortars such as those from Rhodes, Greece, or Hagia Sophia, Turkey, revealed the presence of a calcium-silicate-hydrate (C-S-H) binding phase. This phase, which is similar to that found in ordinary Portland cement (OPC), is produced under the pozzolanic reaction of slaked lime with fine reactive siliceous sources at temperatures

Geoinformatics FCE CTU, 2011

Information on current state of immovable cultural heritage is important for specifying measures ... more Information on current state of immovable cultural heritage is important for specifying measures necessary to preserve the heritage in an appropriate condition and ensure that the maintenance required to keep it at this level is well defined. In this framework, EU-CHIC project aims to set-up a system introducing a concept of the “Cultural Heritage Identity Card”, which will develop into a systematic collection and storage of data on immovable heritage objects across European and neighboring countries. This work supports sustainable maintenance, preservation and revitalization of historic sites and monuments. This is achieved through the development of a guideline for the assessment of efficient documentation systems that identify the parameters needed for the characterisation of the preservation state of a monument and its possible alterations during its entire lifetime. In order to develop and test the recommendations for efficient compilation of the data pertinent to each monument...

Buildings, Mar 16, 2024

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Within the framework of the collaboration between Princeton University, the National Technical Un... more Within the framework of the collaboration between Princeton University, the National Technical University of Athens, and Bogazici University, the present work deals with material analyses of small samples taken from Hagia Sophia, a sixth century masonry edifice, in Istanbul, Turkey, coordinated with structural studies to provide insight to the structure's ability to withstand seismic loads. The present work is based on the methods of X-ray diffraction analysis and thermogravimetric analysis performed both on the samples themselves and on their fractions after a physical separation. The results account for a possible technology of a pozzolanic mortar, where one part per volume lime was mixed with 3 parts of aggregate (crushed brick fragments, sea sand, and fine pozzolanic sand). However, up to now, analytical techniques cannot provide directly technology information, let alone on the physicochemical interactions among the constituents of historic walls, as in the case under study...

Measuring, Monitoring and Modeling Concrete Properties

... The spectra reveal the presence of either hydraulic lime or poz-zolana admixed with aerial li... more ... The spectra reveal the presence of either hydraulic lime or poz-zolana admixed with aerial lime, rich in CSH. ... of mortars from traditional build-ings in seismic areas, PACT Revue du groupe europeen d'etudes pour les techniques phy-siques, chimiques, biologiques et ...

The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2013

Sustainable maintenance and preservation of cultural heritage assets depends highly on its resili... more Sustainable maintenance and preservation of cultural heritage assets depends highly on its resilience to external or internal alterations and to various hazards. Risk assessment of a heritage asset's can be defined as the identification of all potential hazards affecting it and the evaluation of the asset's vulnerability (building materials and building structure conservation state).Potential hazards for cultural heritage are complex and varying. The risk of decay and damage associated with monuments is not limited to certain long term natural processes, sudden events and human impact (macroscale of the heritage asset) but is also a function of the degradation processes within materials and structural elements due to physical and chemical procedures. Obviously, these factors cover different scales of the problem. The deteriorating processes in materials may be triggered by external influences or caused because of internal chemical and/or physical variations of materials properties and characteristics. Therefore risk evaluation should be dealt in the direction of revealing the specific active decay and damage mechanism both in mesoscale [type of decay and damage] and microscale [decay phenomenon mechanism] level. A prerequisite for risk indicators identification and development is the existence of an organised source of comparable and interoperable data about heritage assets under observation. This unified source of information offers a knowledge based background of the asset's vulnerability through the diagnosis of building materials' and building structure's conservation state, through the identification of all potential hazards affecting these and through mapping of its possible alterations during its entire lifetime. In this framework the identification and analysis of risks regarding degradation processes for the development of qualitative and quantitative indicators can be supported by documentation protocols. The data investigated by such protocols help identify the parameters needed for the assessment of the preservation state of a monument and its monitoring through its entire lifetime. The main tool for detecting these indicators is a diagnostic methodology based on appropriate standards that reveals the actual degradation processes responsible of the asset's vulnerability. It is very important that the integration between the material's diagnosis and the overall documentation is taken into consideration in order to identify the required levels of protection and preventive conservation for heritage assets depending on the most frequent local risks. The ranging of risks is therefore necessary according to their importance in each area. Documentation protocols provide with a specific diagnostic tool for materials characterization, decay diagnosis, evaluation process of former conservation materials and interventions, standard procedures for monitoring and control as well as data documentation based on specific guidelines and standards. Implementation and analysis of a "standardised" diagnostic study will reveal the main risks due to degradation processes affecting the heritage asset to be subsequently recorded in order to result into risk indicators. The development of risk indicators regarding degradation processes is the basic step towards uptaking efficient management, preventive conservation and strategic planning for heritage assets against various threats. These risk indicators could be further elaborated according to the activities of inspection, diagnosis and intervention works, offering scientific support to the decision making process for cultural heritage preventive conservation and overall protection.

Smart Sensor Phenomena, Technology, Networks, and Systems Integration 2012, 2012

ABSTRACT The church of Hagia Sophia in Istanbul is a world heritage monument that epitomizes the ... more ABSTRACT The church of Hagia Sophia in Istanbul is a world heritage monument that epitomizes the byzantine ecclesiastic architecture. The church is decorated with mosaics from various historic periods. The preservation state of the mosaics is of high importance. In this study, non-destructive techniques (ground penetrating radar, infra-red thermography, fibreoptics microscopy) were employed on south upper gallery mosaic areas. The main aim of this on-site investigation was the evaluation of the preservation state of the mosaics and the previous interventions (materials characterization and decay diagnosis) in order to assess the performance of previous conservation/restoration interventions, as well as to verify the presence of mosaics in layers below the external plaster surfaces. Results indicated that is indeed possible to locate the grid of rendered mosaics. Regarding the preservation state of the mosaics, it was indicated that the main environmental decay factors were the high relative humidity levels with co-action of salt damp as well as the air pollutants. Moreover, it was revealed that previous incompatible restoration/conservation interventions have often accelerated the mosaics' degradation processes. Using non-destructive techniques it was possible to identify areas where the mosaic materials (tesserae and mortars) presented decay problems and in addition identify sub-layers that pose risk of detachment or decay intensification. In this way, NDT can contribute to the development of a strategic planning for mosaics conservation, protection and revealing.

MRS Proceedings, 1995

The decay processes in monuments, considered as interaction between building materials and enviro... more The decay processes in monuments, considered as interaction between building materials and environmental factors, presents a specific interest in the case of marine environment (Mediterranean), in mild climatic conditions. An extended monument, like the Medieval Fortress of Rhodes could be a characteristic example. It is constructed by a susceptible to salt decay biocalcareous porous stone which suffers mainly from salt crystallisation and hard carbonate crusts formation.

Lecture Notes in Computer Science, 2012

ABSTRACT Abstract The world’s cultural heritage is frequently subject to misuse and vandalism by ... more ABSTRACT Abstract The world’s cultural heritage is frequently subject to misuse and vandalism by the general public. However, while a lack of knowledge, unawareness of the heritage values and the importance of its preservation are demonstrated in the real “tangible world” of historic monuments and sites, the general public, and especially youth, have proved to be sophisticated visitors to “intangible” virtual reality. The Euromed Heritage 4 Project “ELAICH” (Educational Linkage Approach In Cultural Heritage) provided an e-tool for increasing “awareness of the importance of Cultural Heritage ... and its conservation by ... the general public” - the eLAICH Educational Toolkit, which was developed and made accessible to the general public through the eLAICH e-learning platform, using Learning Management System (LMS), Content Management System (CMS) and Information and Communication Technologies (ICT). This paper provides an overview of the project’s organization, computerized support, and e-results.

Fracture and Failure of Natural Building Stones

ABSTRACT The decay of materials is a function of intrinsic and extrinsic factors. The intrinsic f... more ABSTRACT The decay of materials is a function of intrinsic and extrinsic factors. The intrinsic factors are related to the material itself, and include the type of the material, its properties and its microstructure. The extrinsic factors refer to the effect that the environment has on the material and can be generally divided into factors related to the atmosphere and factors related to the usage of the material respectively. Salt decay is arguably the most significant deteriorating mechanism for monuments and buildings in marine environment. Salts migrate in the form of solution through the complex capillary system of porous stones towards the surface. Crystallization of soluble salts may appear in the form of efflorescences or subefflorescences. The assessment of the susceptibility of stone to salt decay can be accomplished either through the calculation of crystallization pressure or through the determination of the most probable scenario as determined by an energetic evaluation. Non-destructive techniques can also be used in situ to assess the susceptibility of the building materials and to assess the effectiveness of interventions.

Journal of Cultural Heritage, 2013

Documentation on cultural heritage assets is an indispensable part of an overall strategy for cul... more Documentation on cultural heritage assets is an indispensable part of an overall strategy for cultural heritage protection. Sustainable conservation and management is not feasible without a systematic data collection and registration that identifies the history of the monument, its architectural attributes, preservation state and its possible alterations during its entire lifetime. Integrated documentation protocols for data collection and organizing are developed that built upon certain documentation procedures, encompassing all parameters relating to the monument. These were developed based on the current documentation methodologies survey, revealing the prerequisite main attributes of such protocols, and the need to incorporate quality control principles. Their structure follows a three-level classification of data that reflect the overall information to be documented at an increasing complexity. They constitute a solid basis for any knowledge-based decision making process to establish priorities of cultural heritage protection, through the use of specific necessity indices that utilize the information collected and stored.

Construction and Building Materials, 2013

h i g h l i g h t s NDTs are valuable for the protection of built cultural heritage. NDTs can ass... more h i g h l i g h t s NDTs are valuable for the protection of built cultural heritage. NDTs can assess the preservation state of materials and structures. NDTs can evaluate the efficiency of restoration/protection interventions. NDTs are integrated into information systems for effective planning of interventions.

In this work, diagnostic strategies involving the application of in-situ non-destructive testing ... more In this work, diagnostic strategies involving the application of in-situ non-destructive testing and in-lab techniques, GIS modeling and analysis operations were utilized for planning of materials and conservation interventions at the walls of Erimokastro Acropolis Rhodes. Polarized optical microscopy mercury porosimetry, scanning electron microscopy, determination of total soluble salt content, fibre-optic microscopy, ultrasonics and infra-red thermography were used to characterize the building materials and their ...

The decay of materials is a function of intrinsic and extrinsic factors. The intrinsic factors ar... more The decay of materials is a function of intrinsic and extrinsic factors. The intrinsic factors are related to the material itself, and include the type of the material, its properties and its microstructure. The extrinsic factors refer to the effect that the environment has on the material and can be generally divided into factors related to the atmosphere and factors related to the usage of the material respectively. Salt decay is arguably the most significant deteriorating mechanism for monuments and buildings in marine environment. Salts migrate in the form of solution through the complex capillary system of porous stones towards the surface. Crystallization of soluble salts may appear in the form of efflorescences or subefflorescences. The assessment of the susceptibility of stone to salt decay can be accomplished either through the calculation of crystallization pressure or through the determination of the most probable scenario as determined by an energetic evaluation. Non-des...

Journal of materials science & engineering, 2012

Ground penetrating radar was used to assess the decay state of the mosaics at the south upper gal... more Ground penetrating radar was used to assess the decay state of the mosaics at the south upper gallery of Hagia Sophia, Istanbul. These mosaics were plastered during the Ottoman period of the monument, but during recent conservation interventions part of the plaster layer has been removed. It has been revealed that cohesion problems may be encountered with the preserved mosaic at the perpendicular junction of two arches. In another area, GPR was employed to reveal the presence of underlying mosaics being below the plaster layer. There have been observed void spaces below this layer, indicating possible cohesion problems that need to be taken into consideration in case of future removal of the plaster. In addition, the Empress Zoe mosaic was scanned, verifying good overall cohesion and homogeneity of the mosaic and the substrate structure but also that there exist restored areas with new base mortar and tesserae, confirming historic data.

Non-destructive testing is used for many applications in the cultural heritage protection field. ... more Non-destructive testing is used for many applications in the cultural heritage protection field. In this study three such sensing techniques, portable digital microscope, infrared thermography, georadar were used for the in site investigation of the ISIA building at the historic center of Florence. This work was a sub-action of a research program called MEDNETA; “MEDNETA- Mediterranean cultural network to promote creativity in the arts, crafts and design for communities’ regeneration in historical cities”.

Singh/Innovative, 2012

This study proposes a fundamental microstructural/rheological model for agar gels that describes ... more This study proposes a fundamental microstructural/rheological model for agar gels that describes their dynamic rheological behavior during gelation. The concept of a sigmoidal type temperature dependence of the monomeric friction coefficient, ξ o , of the agar molecule is introduced to describe the increase of relaxation times of the agar molecules with decreasing temperature. At high temperatures (close to 373 K), the model behaves like a dilute solution of flexible polymers. At low temperatures (close to 273 K) contributions from an equilibrium modulus term are predominant. Dynamic rheology was employed to study the applicability of this model for agar gels. Gelation curves were obtained experimentally for various agar concentrations and cooling rates were fitted successfully to the theoretical model predictions.

Computers in Railways X, 2006

The preventive maintenance of rails is necessary for safe, successful and economical railway perf... more The preventive maintenance of rails is necessary for safe, successful and economical railway performance and operations. Rolling contact fatigue (RCF) is one of the main issues that concern the head of the railway. Progressively, RCF defects can propagate inside the material with the risk of damaging the rail, and thus they need to be monitored, categorized, evaluated, and treated through a comprehensive maintenance system. In a previous work with the Athens Metro, an innovative monitoring system was developed based on the capability of non-destructive techniques, such as IR thermography, to inspect and identify defects at early stages and reveal the activated paths of fracture (Moropoulou A., Avdelidis N., et al. Thermosense XXVII, 5782, 371-378, 2005). In the present work with the Athens Piraeus Electric Railways S.A. this system is further integrated into a complete system consisting of three components. The surveillance component identifies the rail defects and includes non-destructive techniques, such as visual inspection, infra-red thermography, ultrasonics, fiber optics microscopy, and ACFM. The data management component receives information from the various defect identification techniques, categorizes them and stores them for further use. The defect warning component uses risk indices such as defect level indices, defect extent indices, and risk threshold values, in order to evaluate the significance of the observed defects. All three components are part of a decision making system that monitors the development of defects, warns for significant threats and schedules rail maintenance.

Journal of Cultural Heritage, 2013

Carbohydrate Polymers, 2002

A theoretical rheological model for agar gels is proposed, based on the bead and spring model for... more A theoretical rheological model for agar gels is proposed, based on the bead and spring model for linear flexible random coils and the model for crosslinked polymers. The model introduces the concept of a temperature dependence of the monomeric friction coefficient, ζ0, of the agar molecule. The model has a random coil-like behavior at high temperatures (close to 373K), and contributions from a three-dimensional network at low temperatures (close to 273K). A proposed temperature dependence of the net association rate allows the calculation of the fraction of associated molecules as a function of time and temperature. The proposed model predicts the gelation behavior of agar gels utilizing time–temperature data (cooling curves).

Cement and Concrete Research, 2004

Traditional pozzolanic mortars such as those from Rhodes, Greece, or Hagia Sophia, Turkey, reveal... more Traditional pozzolanic mortars such as those from Rhodes, Greece, or Hagia Sophia, Turkey, revealed the presence of a calcium-silicate-hydrate (C-S-H) binding phase. This phase, which is similar to that found in ordinary Portland cement (OPC), is produced under the pozzolanic reaction of slaked lime with fine reactive siliceous sources at temperatures

Geoinformatics FCE CTU, 2011

Information on current state of immovable cultural heritage is important for specifying measures ... more Information on current state of immovable cultural heritage is important for specifying measures necessary to preserve the heritage in an appropriate condition and ensure that the maintenance required to keep it at this level is well defined. In this framework, EU-CHIC project aims to set-up a system introducing a concept of the “Cultural Heritage Identity Card”, which will develop into a systematic collection and storage of data on immovable heritage objects across European and neighboring countries. This work supports sustainable maintenance, preservation and revitalization of historic sites and monuments. This is achieved through the development of a guideline for the assessment of efficient documentation systems that identify the parameters needed for the characterisation of the preservation state of a monument and its possible alterations during its entire lifetime. In order to develop and test the recommendations for efficient compilation of the data pertinent to each monument...

ed. Marinos Ioannides et al.: Progress in Cultural Heritage Preservation; 4th International Conference, EuroMed 2012, Limassol, Cyprus, October /November / 2012, Lecture Notes in Computer Science, LNCS 7616, Springer 2012, 2012

The world’s cultural heritage is frequently subject to misuse and vandalism by the general public... more The world’s cultural heritage is frequently subject to misuse and vandalism by the general public. However, while a lack of knowledge, unawareness of the heritage values and the importance of its preservation are demonstrated in the real “tangible world” of historic monuments and sites, the general public, and especially youth, have proved to be sophisticated visitors to “intangible” virtual reality. The Euromed Heritage 4 Project “ELAICH” (Educational Linkage Approach In Cultural Heritage) provided an e-tool for increasing “awareness of the importance of Cultural Heritage ... and its conservation by ... the general public” [1] - the eLAICH Educational Toolkit, which was developed and made accessible to the general public through the eLAICH e-learning platform, using LMS , CMS and ICT . This paper provides an overview of the project’s organization, computerized support, and e-results.