Papers by Leszek Krzemien
Biomechanics and Modeling in Mechanobiology
We present a model useful for interpretation of indentation experiments on animal cells. We use f... more We present a model useful for interpretation of indentation experiments on animal cells. We use finite element modeling for a thorough representation of the complex structure of an animal cell. In our model, the crucial constituent is the cell cortex—a rigid layer of cytoplasmic proteins present on the inner side of the cell membrane. It plays a vital role in the mechanical interactions between cells. The cell cortex is modeled by a three-dimensional solid to reflect its bending stiffness. This approach allows us to interpret the results of the indentation measurements and extract the mechanical properties of the individual elements of the cell structure. During the simulations, we scan a broad range of parameters such as cortex thickness and Young’s modulus, cytoplasm Young’s modulus, and indenter radius, which define cell properties and experimental conditions. Finally, we propose a simple closed-form formula that approximates the simulated results with satisfactory accuracy. Our ...
This paper discusses a costless method of improving daylighting in a building. It shows that the ... more This paper discusses a costless method of improving daylighting in a building. It shows that the diagonal cuts in insulation around windows substantially increase the amount of light coming into the building without compromising the heat resistance of the barrier. The effect of various depth and angles of cuts on the daylighting as well as the thermal performance of the envelope is simulated. An optimal geometry is found as a function of insulation thickness. The results were obtained using the finite element method. A novel approach was used that allows the daylighting and thermal simulation to be performed in the same simulation environment using the same geometry. Additionally, a traditional daylighting analysis was performed. They show that for the thick insulation, bevels make difference between having and not having satisfactory levels of light in the room.
The 3rd International Conference on Energy Efficiency in Historic Buildings (EEHB2018), Visby, Sweden, September 26th to 27th, 2018., 2018
Bulletin of the American Physical Society, Jun 8, 2012
Studies in Conservation, 2016
The drying shrinkage accumulation from exposure of freshly prepared gesso layers to relative humi... more The drying shrinkage accumulation from exposure of freshly prepared gesso layers to relative humidity (RH) cycles was determined to elucidate the mechanism of craquelure pattern formation on panel paintings. The progresive drying shrinkage of the gesso is observed only under the cycles going to high RH levels which bring about transitions from brittle to ductile state of the material. The first incidence of fracture on the gesso layers occurred after a limited number of cycles ranging between a few and 100 for a range of layer thickness between 0.5 and 1 mm. The craquelure patterns stabilised also after a limited number of cycles (30 for the 1-mm thick layer). Upon increase in the gesso layer thickness, the strength of the layer is reduced and the spacing of shrinkage fractures increases. The study demonstrated that craquelure patterns, mimicking historical ones, can be realistically produced in laboratory conditions. Such studies would provide useful information for preparing specimens simulating historic panel paintings and would inform the current efforts on automatic, computer-aided classifications of crack formations on paintings.
Heritage Science, 2020
Moisture adsorption and related dimensional change were examined in several samples of historic a... more Moisture adsorption and related dimensional change were examined in several samples of historic and contemporary parchment. The tensile behaviour was determined for contemporary parchment and two selected historic materials. The moisture-related data for most parchments are close to the contemporary material while aging and past treatments may lower adsorption of moisture and, in consequence, the dimensional change induced by changes in the moisture content. Contemporary parchment exhibited larger water vapour adsorption and moisture-related response compared to most historic materials and, therefore, can be regarded as the worst-case material in terms of the climate-induced risks to parchment. Tensile parameters of parchment varied significantly with increasing relative humidity (RH). Elasticity modulus declined from on average 1200 to 400 MPa and strain at failure doubled when RH increased from 30 to 85%. Parchment’s critical strain at which permanent deformation occurred decrease...
Archeion
Budynek archiwum państwowego to miejsce służące przede wszystkim długoterminowej ochronie materia... more Budynek archiwum państwowego to miejsce służące przede wszystkim długoterminowej ochronie materiałów archiwalnych. Musi także spełniać wymagania stawiane przyjaznej instytucji publicznej, związane z obsługą i zaspokajaniem różnorodnych potrzeb użytkowników w zakresie działalności prowadzonej przez archiwa. Pełnione przez archiwa funkcje determinują, już na etapie opracowywania koncepcji, a następnie dokumentacji projektowej, kwestie konstrukcji, wyposażenia oraz zastosowanych instalacji i technologii. Szczególne znaczenie w przypadku archiwum państwowego mają pomieszczenia magazynowe, służące przechowywaniu materiałów archiwalnych. W wypadku nowej siedziby Archiwum Narodowego w Krakowie, dla ośmiokondygnacyjnego segmentu magazynowego opracowano koncepcję z pasywną regulacją klimatu. Jest on wyodrębnioną strukturą, w której nie ma stałych stanowisk pracy, a pasywną stabilizację mikroklimatu zapewniono w znacznym stopniu przez przemyślane rozwiązania budowlane: dobrą izolację termiczn...
Holzforschung, 2015
Scots pine (Pinus sylvestris L.) was subjected to relative humidity (RH) changes, and the dynamic... more Scots pine (Pinus sylvestris L.) was subjected to relative humidity (RH) changes, and the dynamic strain field on the surface and in the bulk wood was monitored by digital speckle pattern interferometry and X-ray computed microtomography assisted by digital volume correlation. If a freely shrinking specimen was subjected to an RH decrement, earlywood (EW) and latewood (LW) at the surface layer were deformed in the opposite directions at the beginning of drying due to moisture gradient across the specimen. As a result, the surface and core behaved as independent sub-components, with the surface restrained in its response by the dimensionally unchanged core. With time, both LW and EW shrank as moisture content (MC) became uniform across the specimen. When an entire wood specimen was restrained from movement and desiccated in ambient RH, EW was stretched to compensate for the considerable shrinkage of LW. Knowledge about surface deformation at the annual ring level as a function of varying RH may be helpful to assess the risks associated with the damage of paint layers caused by fluctuations of ambient RH.
Experimental Techniques
The paper presents an experimental procedure based on micro-scratching to detect stresses in the ... more The paper presents an experimental procedure based on micro-scratching to detect stresses in the ground layer of panel paintings. The method relies on the fact that cracking of the material during a micro-scratching test is the outcome of a combination of local force applied by an indenter and the stresses present in the material. The critical normal load at which damage appears during the test has a strong correlation with the stress in the material. The method, although not providing absolute values of stress, is sensitive to stress magnitude and direction, only micro-destructive, and attractive for monitoring stress changes caused by relaxation processes also in multi-layer materials. The presented tests were performed on artistic materials for which information on stress relaxation is particularly important when developing strategies for their storage and transportation.
Studies in Conservation
HERIe is a web-based decision-supporting software tool to facilitate the management of collection... more HERIe is a web-based decision-supporting software tool to facilitate the management of collection environments by precise assessment of climate-induced risk of physical damage to vulnerable objects. The software translates the relative humidity and temperature data recorded in the environment of the analysed object into a strain history experienced by it, and estimates the risk of physical damage using selected failure criteria. As all information is pre-calculated for the user, no engagement in complex and time-consuming numerical simulations is required. HERIe is available for testing at herie.mnk.pl. Detailed information on the methodologies used by the software is available at the above website which also contains tutorial climates. The current work aims at refining HERIe by selecting the damage criteria not only from laboratory studies but also from direct monitoring damage accumulation in objects, especially using the acoustic emission method. The software has been expanded to include moisture-induced response of parchment to support managing environments in libraries and archives.
HERIe is a web-based decision-supporting software tool to facilitate the management of collection... more HERIe is a web-based decision-supporting software tool to facilitate the management of collection environments by precise assessment of climate-induced risk of physical damage to vulnerable objects. The software translates the relative humidity and temperature data recorded in the environment of the analysed object into a strain history experienced by it, and estimates the risk of physical damage using selected failure criteria. As all information is pre-calculated for the user, no engagement in complex and time-consuming numerical simulations is required. HERIe is available for testing at herie.mnk.pl. Detailed information on the methodologies used by the software is available at the above website which also contains tutorial climates. The current work aims at refining HERIe by selecting the damage criteria not only from laboratory studies but also from direct monitoring damage accumulation in objects, especially using the acoustic emission method. The software has been expanded to...
Experimental Techniques, 2018
The paper presents an experimental procedure based on micro-scratching to detect stresses in the ... more The paper presents an experimental procedure based on micro-scratching to detect stresses in the ground layer of panel paintings. The method relies on the fact that cracking of the material during a micro-scratching test is the outcome of a combination of local force applied by an indenter and the stresses present in the material. The critical normal load at which damage appears during the test has a strong correlation with the stress in the material. The method, although not providing absolute values of stress, is sensitive to stress magnitude and direction, only micro-destructive, and attractive for monitoring stress changes caused by relaxation processes also in multi-layer materials. The presented tests were performed on artistic materials for which information on stress relaxation is particularly important when developing strategies for their storage and transportation.
Archiwum Uj Dokt 2009 143, 2009
We describe diagnostic techniques used for optimization of loading of an optical dipole trap with... more We describe diagnostic techniques used for optimization of loading of an optical dipole trap with CO2 laser and 87Rb atoms. Atoms, precooled in a magneto-optical trap, were loaded into the trap formed by a weakly focused CO2 laser beam with the waist of about 150 μm and power of 50 W. In addition to determining the atom number and temperature, the effect of the loading geometry on the time evolution of trapped atoms is discussed. It is shown that a direct study of this evolution can be used for determining the trap frequencies.
Journal of Cultural Heritage, 2014
ABSTRACT Digital speckle-shearing-pattern interferometry (DSSPI) combined with digital speckle pa... more ABSTRACT Digital speckle-shearing-pattern interferometry (DSSPI) combined with digital speckle pattern interferometry (DSPI) were used to document the state of preservation of 8th to 14th century wall paintings of Christian Nubia. The original plasters of the paintings were multilayer inhomogeneous structures cracked in some parts. They were removed from the cathedral in Faras, Sudan, between 1961 and 1964 as part of efforts to rescue archaeological works threatened by flooding and are now held in the collection of the National Museum in Warsaw. Delaminated areas in surfaces of the paintings were detected by inducing surface vibrations with a sonic wave of varying frequency emitted from a loudspeaker. DSPI allowed the size of the areas and vibration resonant frequencies to be characterized, whereas DSSPI was successful in obtaining the spatial distribution of the vibration amplitude with sub-micrometre accuracy as a function of the sound frequency used. The procedure provided precise, detailed and reproducible information on the character of each damaged area in spite of the considerable size of the paintings and the unstable out-of-lab conditions of a conservation studio in which the measurements were carried out. The obtained results will be used as a reference for future surveys of the paintings in order to trace the possible development of surface detachments, even at an incipient stage, which cannot be easily detected by the naked eye or manual inspection.
2011 International Quantum Electronics Conference (IQEC) and Conference on Lasers and Electro-Optics (CLEO) Pacific Rim incorporating the Australasian Conference on Optics, Lasers and Spectroscopy and the Australian Conference on Optical Fibre Technology, 2011
We report the realization of trapping of 87Rb | F=1, mF = −1〉 atoms at temperature of 1–2 μK in a... more We report the realization of trapping of 87Rb | F=1, mF = −1〉 atoms at temperature of 1–2 μK in a 10 μm-period 1D magnetic lattice constructed from a TbGdFeCo magnetic microstructure on an atom chip.
We demonstrate photoionization spectroscopy in cold rubidium atoms trapped in a working magneto-o... more We demonstrate photoionization spectroscopy in cold rubidium atoms trapped in a working magneto-optical trap. Three-photon ionization with two-photon resonance proceeds along various channels, with the step-by-step 5S-5P-5D transition and with the two-photon excitation of the 5D or 7S state. The processes are monitored by measuring ion signals which allow sensitive spectroscopy of weak transitions in a cold-atom sample.
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Papers by Leszek Krzemien