Jaroslav Valach | Academy of Sciences of the Czech Republic (original) (raw)

Papers by Jaroslav Valach

Staletá Praha, Dec 14, 2021

The flexibility of Semantic Web ontologies in knowledge mapping and sharing has induced in the la... more The flexibility of Semantic Web ontologies in knowledge mapping and sharing has induced in the last few years professionals and researchers to study their application to various fields of knowledge, including among others flight control and hospital management systems. This paper reviews the applicatibility of ontologies to the domain of cultural heritage protection, outling the main findings of the MONDIS research project. More specifically it outlines the knowledge-based tools, grounded on an ontological representation of the field of heritage conservation, including: the MONDIS mobile application, the ontomind profiles, the MONDIS record explorer, the knowledge matrix and the terminology editor. These tools can be divided into two groups: inputting tools, including the mobile application and ontomind profiles, and visualization tools, such as the record explorer, the knowledge matrix and the terminology editor. Such a comprehensive range of applications opens to the standardization and management of a heterogeneous set of data facilitating the integration of exisitng information systems into the presented one. Finally the paper discusses the main advantage of the ontological approach as applied to historic building inspection and damage identification, highlighting how an ontological data mapping can ensure the information compatibility for automatic data reasoning and processing required for advanced searching and data matching purposes. The advancement of the MONDIS research in the context of cultural heritage protection and the possibility for future developments of the system are also discussed in the paper.

Advanced Engineering Materials, May 8, 2017

In this paper, impact testing of auxetic structures filled with strain rate sensitive material is... more In this paper, impact testing of auxetic structures filled with strain rate sensitive material is presented. Two dimensional missing rib, 2D re-entrant honeycomb, and 3D re-entrant honeycomb lattices are investigated. Structures are divided into three groups according to type of filling: no filling, low expansion polyurethane foam, and ordnance gelatine. Samples from each group are tested under quasistatic loading and dynamic compression using Split Hopkinson Pressure Bar. Digital image correlation is used for assessment of in-plane displacement and strain fields. Ratios between quasistatic and dynamic results for plateau stresses and specific energy absorption in the plateau are calculated. It is found out that not only the manufactured structures, but also the wrought material exhibit strain rate dependent properties. Evaluation of influence of filling on mechanical properties shows that polyurethane increases specific absorbed energy by a factor of 1.05-1.4, whereas the effect of gelatine leads to increase of only 5-10%. Analysis of the Poisson's function reveals influence of filling on achievable (negative) values of Poisson's ratio, when compared to unfilled specimens. The results for the Poisson's function yielded apparently different values as the assessed minima of quasi-static Poisson's ratio in small deformations are constrained by a factor of 15.

WIT transactions on engineering sciences, Oct 14, 2005

The optical measurement of flat specimen deformation is a frequent task. In some applications it ... more The optical measurement of flat specimen deformation is a frequent task. In some applications it is necessary to measure both the in-plane and out-of-plane displacement or strain fields respectively. To achieve this goal a variety of methods have been developed in the past. This paper describes a novel technique based on the use of only one camera which employs a combination of two different optical methods to achieve 3D displacement measurements. The optical grid method for the measurement of the in-plane strain field and the proposed Coded Photometric Stereo method for the measurement of the out-of-plane displacement can be applied simultaneously. This approach reduces hardware part costs. The combined method is full field (all data acquired at once), non-contact and non-destructive.

Journal of Cultural Heritage, 2015

Understanding damages to cultural heritage represents a very complex task based on a multidiscipl... more Understanding damages to cultural heritage represents a very complex task based on a multidisciplinary interpretation of gathered information. Integrating the knowledge of different branches of science related to cultural heritage protection into a comprehensive knowledge-based system allows endorsing professional decision-making processes with the particular scope to mitigate the challenge posed by damage diagnosis to both expert and non-expert users. This paper proposes a model attempting to convey the benefits of modern ontological know-how to the management and processing of information concerning the diagnostic phase. The methodology consists in translating the professional approach to diagnosis of damages into a computer readable form able to replicate the assessment procedure, step by step, towards a feasible intervention. An overview of possible applications to conservation practice, such as the development of a mobile application dedicated to damage surveying and assessment, is also presented.

Acta Polytechnica, Dec 31, 2022

Key Engineering Materials, Sep 1, 2013

In the case of material parameters required for evaluation of built heritage preservation state, ... more In the case of material parameters required for evaluation of built heritage preservation state, knowledge of the least possible volume of removed sample is essential in order to minimize damage accumulation to the buildings. These requirements lead to determination of representative volume element (RVE) that was in this paper calculated using combination of image and signal processing techniques. Then, a detailed map of material properties was created using nanoindentation to evaluate local characteristics of the material. Furthermore, atomic composition of samples was quantified by energy dispersive spectrometry (EDX) detector for scanning electron microscopy (SEM) device. Presented method based on combination of SEM, EDX and nanoindentation techniques demonstrates possibility of effective testing in the field of historical buildings preservation.

Advanced Engineering Materials, Oct 1, 2020

The development of reliable method to measure deformations belongs to the most important tasks in... more The development of reliable method to measure deformations belongs to the most important tasks in study of constructions and materials nowadays. The availability of these methods is a prerequisite for effective application of materials in all technical areas because they the reliable knowledge of true state of constructions allows us to use them safely and extend their life span. The one of way how to reach these goals is an analysis of behavior of metals during large plastic deformations. If we will know the processes which are responsible for cumulations and growth of defects in materials we can identify the undesirable symptoms prior catastrophic failure. The aim of the presented research is to find out more about the plastic strain processes by using thermo-camera and FEM.

Key Engineering Materials, Mar 1, 2014

This study is focused on inspection of damage extent induced into C/PPS composite material by fat... more This study is focused on inspection of damage extent induced into C/PPS composite material by fatigue and impact loading. Initial damage to specimens was induced by drop-weight out-of-plane impact damage. Several levels of damage states (intact specimen, fatigued and impacted specimen, ruptured specimen) were inspected using modulus mapping (MM) technique. Quantification of the damage level was based on comparison of results from MM obtained in distinct locations on the specimens. Regions of interest were selected in order to determine magnitude of damage after impact and to assess remaining loading capabilities of the material. For this purpose, material maps provided information about location where matrix had been inflicted by the damage. Results show that impact loading has no measurable influence on mechanical properties of the matrix. However, gradient in mechanical properties was detected in the vicinity of crack. Results were validated using quasi-static nanoindentation and constant strain rate continuous measurement that showed depth profile of mechanical properties.

International Journal of Heritage in the Digital Era, 2012

This paper presents an abbreviated review of the potential capacities of the project on Non-destr... more This paper presents an abbreviated review of the potential capacities of the project on Non-destructive and Considerately (Medium) Destructive Methods for Testing Historic Stone, developed within the 7 th EC FP STONECORE project. These methods include ultrasonic tests, peeling tests, drilling resistance and water uptake by various approaches. The material characteristics acquired by means of these methods are compared with the characteristics measured by destructive standard tests, and the observed correlations are discussed.

Lecture Notes in Computer Science, 2018

Digitization of exhibits and the creation of virtual exhibitions is undergoing a period of stormy... more Digitization of exhibits and the creation of virtual exhibitions is undergoing a period of stormy development and is a dynamic area of care for museum collections. The availability of digital models has a major share in the growing trend of on-line access to collections. At the same time, digitization can improve the protection of items and increase their availability for the public as well as for professionals. It can be performed using procedures based on different physical principles and their technical implementation, with different requirements for the captured objects and different quality levels of the achieved outputs. This paper introduces a technique of 3D digitization based on the principle of photometric stereo. First, it describes typical objects, followed by the physical fundamentals of the method and the selected technical solution. A section on the examples of results introduces the application of this method for creating digital models of various objects and, finally, the conclusion contains contemplations on further development of this method in the future.

This paper deals with an experimental investigation of the future environmental load on the medie... more This paper deals with an experimental investigation of the future environmental load on the medieval mosaic of the Last Judgement located at the entrance to St. Vitus cathedral in the Prague castle. The mosaic suffers from seasonal changes of the weather pattern including rains and their acidity, the deposition of dust and soot particles from polluted air as well as freeze-thaw cycles. These phenomena influence the conservation state of the mosaic. The tesserae composing the mosaic are mostly made from glass prone to weathering. In order to establish a procedure for an appropriate maintenance, the relation between various weather scenarios and their effect on the mosaic was investigated. At the same time a local method for evaluating a suitable protective coating was developed. Both methods will contribute to better care for the mosaic and also to improve visitors' aesthetical experience.

Springer eBooks, Jan 4, 2008

ABSTRACT Finite elements method is widely used for numerical simulations of solid object behaviou... more ABSTRACT Finite elements method is widely used for numerical simulations of solid object behaviour in many applications questioning in some cases the necessity of physical experiments. Available databases of material behaviour are quite sufficient for simulations of linear systems. However for the simulations of nonlinear systems, it is still necessary to have experimental information’s. Unfortunately, the feedback based on strain measurement in several points only can lead to accurate but imaginary numerical solution. Full field strain measurement is routinely performed today. Let’s reduce the class of the analyzed object onto flat specimens only. Dependency on loading type and studied feature, either the in-plain or out-of plain experimental method is usually chosen. One of the highly non-linear problems is the failure of ductile specimen with stress concentrator especially when failure is accompanied by the developing of damage zone in the vicinity of the stress concentrator. Corresponding damage models have a number of parameters which is necessary to determine. The feedback based on in-plane strain measurement only can lead to a non-unique solution as well as without prior knowledge of material damage type. From this reason both in-plane and out-of plane displacement measurement is required. On the other hand monitoring the out-of plane displacement can detect the onset of intensive damage zone development [1].

World Academy of Science, Engineering and Technology, International Journal of Humanities and Social Sciences, Dec 13, 2015

Key Engineering Materials, Sep 1, 2015

In contrast to imaging in visible spectrum temporally-varying distortion (drift distortion) cause... more In contrast to imaging in visible spectrum temporally-varying distortion (drift distortion) caused by positional errors of electron beam during the scanning process occurs in SEM devices. This effect is always present in the data from SEM and its magnitude depends on acquisition time, magnification and conductivity of the sample (where lower conductivity causes higher drift distortion). In this paper 2D digital image correlation based on Lucas-Kanade algorithm was used to assess drift distortion characteristics of MIRA II LMU SEM device during imaging of materials with different conductivity and microstructural properties. Using the DIC technique deformations in the micrographs were evaluated and tool for correction of positional errors was developed. As shown on a set of selected multiphase mixtures this tool enables qualitative backscattered electron analysis independently on the material type and imaging parameters including acquisition time. This enables reliable evaluation of material parameters that have influence on effective mechanical properties.

Carbon fibre in polyphenylene sulfide composites became popular material in aircraft industry but... more Carbon fibre in polyphenylene sulfide composites became popular material in aircraft industry but its fragility and low resistance against impact loading limits the application of these composites in aircraft primary structures. The article deals with experimental investigation of the mechanical response of damaged composite. Material degradation of intact and damaged specimens during fatigue tests was investigated. The changes in natural frequencies, ultrasound wave propagation and bending stiffness were chosen as damage parameters. The entire fatigue life of intact and damaged specimens was studied in the article by all the presented methods. The accuracy and reliability of assessment of damage parameters were compared. Comparison of accuracy and reliability of presented method for assessment of damage parameters is also given.

Acta Polytechnica CTU Proceedings, Feb 11, 2016

Physical weathering of marble, widely used as a cladding material on buildings, is one of the mos... more Physical weathering of marble, widely used as a cladding material on buildings, is one of the most common damaging mechanism caused by anisotropic thermal expansion of calcite grains. The extent of marble deterioration depends mainly on stone fabric and texture. Dry cuboids of Carrara marble and marble from Dolni Morava quarry were subjected to microscopic analysis and thermal cycling, to determine the thermal expansion related to stone fabric and predominant lattice orientation of grains (i.e. texture).