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Phyllotactic Model Linking Nano and Macro World
Horáček, Miroslav; Meluzín, Petr; Krátký, Stanislav; Urbánek, Michal; Bok, Jan; Kolařík, Vladimír
2017 - anglický
Recently, the arrangement of diffraction primitives according to a phyllotactic model was presented. This arrangement was used to benchmarking purposes of the e-beam writer nano patterning. The phyllotactic arrangement has several interesting properties. One of them is related with the coherence between the nanoor microscopic domain of individual optical primitives and the properties of visually perceived images crated by these structures in the macro domain. This paper presents theoretical analysis of the phyllotactic arrangement in the referred context. Different approaches enabling the creation of diffractive optically variable images are proposed. The practical part of the presented work deals with the nano patterning of such structures using two different types of the e-beam pattern generators. One of them is a system with a variable shaped beam of electrons, while the other one is a system with a Gaussian-shaped beam. E-beam writing strategies and the use of inherent spiral patterns for exposure ordering and partitioning are also discussed.
Klíčová slova:
nano patterning; spiral grating structure; phyllotactic pattern; e-beam writer
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Phyllotactic Model Linking Nano and Macro World
Recently, the arrangement of diffraction primitives according to a phyllotactic model was presented. This arrangement was used to benchmarking purposes of the e-beam writer nano patterning. The ...
Study of laser wobbling welding process through the radiation of plasma plume
Mrňa, Libor; Horník, Petr; Jedlička, Petr; Pavelka, Jan
2017 - anglický
During laser welding with wobbling to the vector of the welding speed adds trivial movement of the beam in the shape of a circle or other shapes. Therefore, the laser beam moves with much higher current speeds than during normal welding. The melting of material on the leading edge of the keyhole occurs periodically. This fact is reflected in the character of the radiation of plasma plume over the keyhole. Experiments were conducted in which it was obtained spectrum of plasma plume radiation by using autocorrelation function for different parameters of circular wobbling (circle diameter, frequency) and for different materials. In the spectra are found the higher harmonic frequency of wobbling. The results were also compared with the radiation of the plasma plume during pulsed laser welding where the laser beam also periodically melts the leading edge.
Klíčová slova:
laser welding; wobbling; process monitoring
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Study of laser wobbling welding process through the radiation of plasma plume
During laser welding with wobbling to the vector of the welding speed adds trivial movement of the beam in the shape of a circle or other shapes. Therefore, the laser beam moves with much higher ...
Babinet principle for plasmonic antennas: complementarity and differences
Horák, M.; Křápek, V.; Hrtoň, M.; Metelka, O.; Šamořil, T.; Stöger-Pollach, M.; Paták, Aleš; Šikola, T.
2017 - anglický
Plasmonics deals mainly with surface plasmon polaritons (SPP), which are collective oscillations of free electrons at metal-dielectric interfaces connected with the local electromagnetic field. When SPP are spatially restricted to a metallic nanoparticle, we talk about localized surface plasmons (LSP). LSP resonances can be characterized with an excellent spectral and spatial resolution by electron energy loss spectroscopy (EELS) and cathodoluminescence. Both techniques utilize an electron beam that interacts with the metallic nanoparticle and excites the LSP resonances. EELS measures the energy transferred from electrons to the LSP and cathodoluminescence deals with the light which the LSP emit during their decay. Babinet principle, originating in the wave theory of light and analysis of diffraction, relates the optical response of apertures in thin films and their complementary particle analogues. According to the Babinet principle, LSP in complementary particles and apertures have identical resonance energies and their near fields are closely linked: the electric field distribution of a specific in-plane polarization for an aperture corresponds to the magnetic field distribution of a perpendicular polarization for a particle.
Klíčová slova:
Babinet principle; complementarity; plasmonic antennas; cathodoluminescence; EELS
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Babinet principle for plasmonic antennas: complementarity and differences
Plasmonics deals mainly with surface plasmon polaritons (SPP), which are collective oscillations of free electrons at metal-dielectric interfaces connected with the local electromagnetic field. When ...
Phase and group refractive indices of air calculation by fitting\nof phase difference measured using a combination of laser and\nlow-coherence interferometry
Pikálek, Tomáš; Šarbort, Martin; Číp, Ondřej; Pham, Minh Tuan; Lešundák, Adam; Pravdová, Lenka; Buchta, Zdeněk
2017 - anglický
The air refractive index is an important parameter in interferometric length measurements, since it substantially\naffects the measurement accuracy. We present a refractive index of air measurement method based on monitoring\nthe phase difference between the ambient air and vacuum inside a permanently evacuated double-spaced cell. The cell is placed in one arm of the Michelson interferometer equipped with two light sources—red LED and HeNe laser, while the low-coherence and laser interference signals are measured separately. Both phase and group refractive indices of air can be calculated from the measured signals. The method was experimentally verified by\ncomparing the obtained refractive index values with two different techniques.
Klíčová slova:
air refractive index; laser interferometry; low-coherence interferometry
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Phase and group refractive indices of air calculation by fitting\nof phase difference measured using a combination of laser and\nlow-coherence interferometry
The air refractive index is an important parameter in interferometric length measurements, since it substantially\naffects the measurement accuracy. We present a refractive index of air measurement ...
Efficient implementation of Stockwell Transform for real-time embedded processing of physiologic signals
Holmes, D.; Pinto, S.C.; Felton, Ch.; Smítal, L.; Leinveber, P.; Jurák, Pavel; Gilbert, B.; Haider, C.
2017 - anglický
Physiologic monitoring enables scientists and physicians to study both normal and pathologic signals of the body. While wearable technologies are available today, many of these technologies are limited to data collection only. Embedded processors have minimal computational capabilities. We propose an efficient implementation of the Stockwell Transform which can enable real-time time-frequency analysis of biological signals in a microcontroller. The method is built upon the fact that the Stockwell Transform can be implemented as a compact filter bank with pre-computed filter taps. Additionally, due to the long tails of the gaussian windowing function, low amplitude filter taps can be removed. The method was implemented on a TI MSP430 processor. Simulated ECG data was fed into the processor to demonstrate performance and evaluate computational efficiency.
Klíčová slova:
time-frequency analysis; biomedical monitoring; electrocardiography; real-time systems
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Efficient implementation of Stockwell Transform for real-time embedded processing of physiologic signals
Physiologic monitoring enables scientists and physicians to study both normal and pathologic signals of the body. While wearable technologies are available today, many of these technologies are ...
Lift-off technology for thick metallic microstructures
Krátký, Stanislav; Horáček, Miroslav; Meluzín, Petr; Kolařík, Vladimír; Matějka, Milan; Oulehla, Jindřich; Pesic, Z.
2017 - anglický
This paper deals with a method enabling the preparation of thick metallic microstructures on metal substrates. Such metallic microstructures can be used as a resolution samples to characterize various microanalysis techniques, such as X-ray fluorescence (XRF) or X-ray photoelectron spectroscopy (XPS). Moreover, the\npatterned samples could be used as anodes to characterize focusing properties of X-ray tubes for micro CT systems. Considering that the standard lift-off technique is designated for structures with the thickness of several hundred nanometers at most, we had to modify lift-off technique to be possible to use it for preparation of very thick metal layers (several microns) with spatial resolution of a few microns. The mask with the desired pattern for UV exposure was prepared by e-beam lithography. SU-8 photoresist was used for a lift-off because of its aspect ratio ability, process purity and high resistance to heating. We used a thin layer of PMMA under the SU-8 masking layer to guarantee the photoresist would lift-off correctly. Thick aluminum layer was deposited by thermal evaporation. The dependence of metal layer thickness as a function of required exposed\nline width was determined. The final lift-off process was carried out in acetone ultrasonic bath. Generally, this technology can be used for the evaporate deposition of various materials with several microns thick layer in\nmicron resolution.
Klíčová slova:
lift-off technique; SU-8 photoresist; e-beam lithography; thick layer evaporation
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Lift-off technology for thick metallic microstructures
This paper deals with a method enabling the preparation of thick metallic microstructures on metal substrates. Such metallic microstructures can be used as a resolution samples to characterize various ...
Possibilites of using the Erichsen test for determination of forming limit diagram and its utilization for hydroforming
Řiháček, J.; Mrňa, Libor; Peterková, E.; Dvořák, M.
2017 - anglický
Forming limit diagrams (FLD) are used to determine process limitations in sheet metal forming, i.e. as a level of formability assisting in the estimation of stamping characteristics. This paper deals with the experimental determination of a forming limit curve (FLC) using the Erichsen test. In this case, FLC of an austenitic stainless\nsteel X5CrNi18-10 is obtained by performing the Erichsen test with different shapes of specimens. Furthermore, utilization of FLD for evaluation of a hydroforming process is shown in the second part of the paper.
Klíčová slova:
Erichsen test; formability; hydroforming; FLD
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Possibilites of using the Erichsen test for determination of forming limit diagram and its utilization for hydroforming
Forming limit diagrams (FLD) are used to determine process limitations in sheet metal forming, i.e. as a level of formability assisting in the estimation of stamping characteristics. This paper deals ...
Structural Colors of Self-Similar Nano Patterns
Meluzín, Petr; Horáček, Miroslav; Krátký, Stanislav; Kolařík, Vladimír
2017 - anglický
E-beam lithography is a flexible technology for various diffraction gratings origination. The e-beam patterning typically allows for the creation of optical diffraction gratings in the first diffraction order. However, the very high resolution enables also the patterning of structures providing the zero-order diffraction. Recently, we presented a work on the structural colors of metallic layers covering both regular-line structures and CGH (computer generated hologram) structures. This work presents a study dealing with zero-order diffraction structures with self-similar properties. The practical part of the work is focused on two aspects: design parameters and technological issues. Variations in design parameters include the tone of the structure (positive or negative),\nthe density of filling, the filling factor, and the depth of the structures. The achieved gamut of colors may by primarily extended by the proper selection of metal deposition technology and its parameters, and further by the proper selection of the metal and the thickness of its layer, these are the technological issues.
Klíčová slova:
e-beam writer; nano patterning; self similarity; diffraction grating
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Structural Colors of Self-Similar Nano Patterns
E-beam lithography is a flexible technology for various diffraction gratings origination. The e-beam patterning typically allows for the creation of optical diffraction gratings in the first ...
Blaze Gratings with a Ribbed Back Slope
Krátký, Stanislav; Meluzín, Petr; Horáček, Miroslav; Kolařík, Vladimír; Matějka, Milan; Chlumská, Jana; Král, Stanislav
2017 - anglický
Binary relief phase-modulated gratings provide symmetrical diffraction of the incoming light beam. Asymmetrical gratings, e.g. asymmetrical triangular blazed gratings, are characteristic by an asymmetrical diffraction behavior, where one of the first diffraction orders is more important than the other one. Electron beam lithography is a suitable and flexible tool for patterning of such kind of gratings. High quality results can be readily obtained when the period of the grating is relatively large and the relief depth is relatively low, this is the case of gratings with a small blaze angle. As the blaze angle increases, the quality of result suffers from several patterning-related issues. One of the problems is a reflection of the incoming light beam from the back slope (anti-blaze facet) of the blaze grating. We propose a novel configuration, with a ribbed modulation of the back slope. This modulation is perpendicular to the direction of the grating grooves. This paper presents an analysis of the proposed blazed grating configuration. E-beam pattern generators were used to prepare a few\nsamples of blaze gratings with a ribbed back slope. One part of the experiment was performed with a Gaussianshaped beam and another one with the variable-shaped beam. Results of the experiment are presented.\nFinally, we discuss the optical performance of two blaze gratings with similar parameters, one of them is with the flat back slope and another one is with the ribbed back slope.
Klíčová slova:
nano patterning; blazed diffraction grating; Gaussian-type beam; variable-shaped beam; electron beam writer
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Blaze Gratings with a Ribbed Back Slope
Binary relief phase-modulated gratings provide symmetrical diffraction of the incoming light beam. Asymmetrical gratings, e.g. asymmetrical triangular blazed gratings, are characteristic by an ...
Hemodynamic modelling in the calf — A pilot study
Matějková, M.; Jurák, Pavel; Soukup, L.; Halámek, Josef; Viščor, Ivo; Langer, P.; Vondra, Vlastimil
2016 - anglický
With increasing age, the cardiovascular system loses its efficiency. The goal of this work was to investigate the hemodynamic system response to a head-up tilt test in two groups of different aged people. We used a model for describing this response in the right calf based on a non-invasive, non-occlusive, bioimpedance signal measurement technique. A decrease in the bioimpedance value in the calf during the head-up tilt test is associated with the accumulation of blood in the calf, which can be expressed by a model parameter. Subjects were examined in both a head-up tilt test and a supine position. 50 healthy non-smoking volunteers were divided into two groups according to age. The impedance signal during the tilt test for each subject was fitted by a model exponential function: Z0 model EF(t) =A exp(-t/B)+C, where Z0 model EF(t) is the calculated model of electrical impedance in the calf by an exponential function, A is the amplitude of impedance change, B is the time constant of the impedance decrease, C is the value of the steady state after the tilt test and t denotes time. A lower time constant B shows a faster filling of the vascular system in the investigated part. The Mann-Whitney test (p-value<;0.005) revealed that the time constant B for the older group was significantly lower than for the young group (145.24+/- 80.28 vs. 239.23+/-136.59 sec.). A lower time constant value means a faster response to blood filling in the lower limbs and directly reflects decreased vessel elasticity. This time constant was lower in the older group. The results show increased vessel stiffness in old age and could lead to a non-invasive evaluating the cardiovascular system state.
Klíčová slova:
impedance; bioimpedance; blood; biomedical monitoring
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Hemodynamic modelling in the calf — A pilot study
With increasing age, the cardiovascular system loses its efficiency. The goal of this work was to investigate the hemodynamic system response to a head-up tilt test in two groups of different aged ...
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