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1

NGS-Concrete - New Generation Shielding Concrete against Ionizing Radiation - the Potential Evaluation and Preliminary Investigation

100%

Piotrowski T., Tefelski D., Sokołowska J., Jaworska B.

Acta Physica Polonica A

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2015

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vol. 128

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issue 2B

B-9-B-13

EN

Concrete is a common material used as a shielding against ionizing radiation due to the relatively low cost and the ability to meet the structural function. State of the art in concrete shielding is that while in case of gamma radiation an increase in density by a change of aggregate is usually efficient enough, protection against neutrons is more complex. It is due to the differences in interactions of neutrons with the matter, depending on their kinetic energy and reaction cross-sections with the component atoms of the cement paste and the aggregate. Last progress in concrete evolution due to use of polymer additives (e.g. superplasticizers) together with reactive additions (e.g. silica fume) allows for a new look at the concrete design for radiation shielding purposes. One of the main advantages of concrete is its composite-type and there is a potential for the optimization of its constituents as well as mixture proportions. The paper presents the preliminary results of the project NGS-Concrete - new-generation shielding concrete against ionizing radiation. The aim of the project is to design the composition of concrete against ionizing radiation, achieved by the use of experiment based multi-criteria optimization of materials supported by the Monte Carlo simulations. The purpose of presented studies was to evaluate neutron shielding properties of ordinary and heavy-weight magnetite concrete modified with epoxy resin and gadolinium oxide. At first the shielding efficiency against neutrons from LWR neutron flux source and Pu-Be was simulated in MCNP code. At the end the comparison of MCNP simulated results and real experiment was presented. It was proved that both methods of modification can improve neutron shielding properties concrete but gadolinium oxide is an efficient additive only for low energy neutron attenuation.

2

Experiments on Neutron Transport through Concrete Member and the Potential for the Use in Material Investigation

100%

Piotrowski T., Tefelski D., Skubalski J., Żak A.

Acta Physica Polonica A

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2015

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vol. 128

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issue 2B

B-14-B-18

EN

Concrete has been used as a shield against high-energy photons and neutrons since the beginning of use of nuclear reaction in energy, medicine and research. From that time the progress in concrete technology is huge - very good concrete used in 60's was about 30 MPa compressive strength, and now the recommendation of ETC-C is to use in EPR nuclear power plant the concrete at least class C45/55 for airplane resistant shell or class C40/50 for other structures. The Monte Carlo computer simulations indicate that an increase in density of the shielding member has a minor effect on the weakening of neutron transport and, therefore, the optimal composition of a shielding concrete against gamma radiation is different than the optimal composition of shielding concrete against neutron radiation. Neutron stopping is a two-step effect: slowing down of fast neutrons and absorption of thermal ones. Both result from the atomic composition of the barrier. The paper presents an analysis of neutrons transport through concrete cement mortar and polymer cement composites mortar based on specially designed experiments which allows for measuring fast neutron attenuation and thermal neutron capture separately. The aim of experiments was to find an influence of the cement type, polymer addition and moisture content on both aspects of neutron shielding properties of a composite. The experimental results were confirmed in MCNP simulations. There was found an influence of cement type on fast neutron attenuation due to differences in chemical composition. Next an important improvement of both fast neutron attenuation and thermal neutron capture due to polymer modification of concrete. The last was fond of clear linear relationship between fast neutron attenuation to the hydrogen content which shows the possibility of using this phenomenon in building material investigation like measurement of moisture content or polymer content in the polymer cement composites.

3

Porous Silicon Formation by Metal-Assisted Chemical Etching

100%

Lipinski M., Cichoszewski J., Socha R., Piotrowski T.

Acta Physica Polonica A

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2009

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vol. 116

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issue S

S-117-S-119

EN

The method of metal-assisted chemical etching produces a porous silicon layer. Palladium particles are deposited on both: multi-crystalline and Czochralski grown mono-crystalline Si wafers by immersing them in PdCl_{2} solution for 1 to 3 min. X-ray photoelectron spectroscopy analysis of Pd clusters shows a decrease in Pd metal fraction by prolonged immersion time t from F_{Pd} = 71.2% for t = 1 min to F_{Pd} = 61.4% for t = 3 min due to Pd oxidation process. Porous silicon forms by metal-assisted chemical etching in a HF:H_{2}O_{2} solution for 1 to 3 min. Photoluminescence of metal-assisted chemical etched samples exhibits the peak with a maximum of t at λ=650 nm independent of the etching time. Simultaneously, the intensity of the photoluminescence spectra strongly decreases for extended etching time t = 3 min. This behavior is attributed to increasing layer macroporosity, which strongly reduces amount of light emitting nanocrystallites.

4

Increased prefrontal event-related current density after sleep deprivation

100%

Szelenberger W., Piotrowski T., Dabrowska A. J.

Acta Neurobiologiae Experimentalis

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2005

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vol. 65

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issue 1

19-28

EN

To investigate how partial sleep loss affects temporal and spatial pattern of information flow, we analyzed sources of brain electrical activity during continuous attention test. Sixteen physicians recruited from the university hospitals participated in the study. Each participant served as his own control. All participants underwent two test sessions including the Stanford Sleepiness Scale (SSS), the Beck Depression Inventory (BDI), the Selective Reminding Test (SRT), and the Continuous Attention Test (CAT). The CAT items were used as stimuli in event-related potential (ERP) recordings. EEG was recorded from 21 electrodes, according to the international 10-20 system. The sources of bioelectrical activity were computed with low resolution electromagnetic tomography (LORETA). Estimated sleep time was significantly shorter on nights spent on duty than on nights of normal sleep at home. Sleep loss resulted in significant increase in SSS and BDI scoring, and impairment of immediate recall. Performance on the CAT remained relatively intact. Under the sleep loss condition compared to baseline, significant differences in brain activity occurred only for targets. Within the P1 time frame, sleep loss led to greater activation in the right Brodmann's area 9/10. For the N1 component, significant differences were localized on the lateral surface of the right frontal lobe, in Brodmann's areas 8 and 9. No significant effects of sleep deprivation on the P3 component were found. Our results are consistent with earlier data indicating that increased activation of the prefrontal cortex allows the maintainance of performance during periods of sleep loss.

5

Optical Properties of Al_{x}Ga_{1-x}As_{y}Sb_{1-y} Epitaxial Layers

100%

Świątek K., Piskorski M., Piotrowski T.

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EN

Photoluminescence spectra of Al_{x}Ga_{1-x}As_{y}Sb_{1-y} layers (x = 0.2-0.5, y = 0.02-0.03) grown by liquid-phase epitaxy on GaSb substrates were studied in a wide temperature range (14-295 K). The temperature changes of energy and intensity of the layer and substrate emission were measured. Linear part of the temperature-induced energy shift of the Al_{0.20}Ga_{0.80}As_{0.02}Sb_{0.98} band-to-band emission exhibits a slope of -0.3 meV/K and -0.45 meV/K at temperatures 150 K and 295 K, respectively.

6

Event-related desynchronization and synchronization in evoked K-complexes

88%

Zygierewicz J., Malinowska U., Suffczynski P., Piotrowski T., Durka P. J.

Acta Neurobiologiae Experimentalis

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2009

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vol. 69

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issue 2

254-26

EN

K-complexes ? phenomena occurring in sleep EEG ? pose severe challenges in terms of detection as well as finding their physiological origin. In this study, K-complexes (KCs) were evoked by auditory stimuli delivered during sleep. The use of evoked KCs enables testing the sleeping nervous system under good experimental control. This paradigm allowed us to adopt into the KC studies a method of signal analysis that provides time-frequency maps of statistically significant changes in signal energy density. Our results indicate that KCs and sleep spindles may be organized by a slow oscillation. Accordingly, KCs might be evoked only if the stimulus occurs in a certain phase of the slow oscillation. We also observed middle-latency evoked responses following auditory stimulation in the last sleep cycle. This effect was revealed only by the time-frequency maps and was not visible in standard averages.

7

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vol. 114

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issue 6A

A-223-A-230

EN

In the paper, the results of technological investigations on planar optical waveguides based on high band gap oxide semiconductors were presented. Investigations concerned the technologies of depositing very thin layers of: zinc oxide ZnO, titanium dioxide TiO_2 and tin dioxide SnO_2 on substrates of quartz glass plates. There were investigated both morphological structures of the produced layers and their optical properties. The paper also presents investigations on the technology of input-output light systems in the Bragg grating structures.

Refine search results

NGS-Concrete - New Generation Shielding Concrete against Ionizing Radiation - the Potential Evaluation and Preliminary Investigation

Experiments on Neutron Transport through Concrete Member and the Potential for the Use in Material Investigation

Porous Silicon Formation by Metal-Assisted Chemical Etching

Increased prefrontal event-related current density after sleep deprivation

Optical Properties of Al_{x}Ga_{1-x}As_{y}Sb_{1-y} Epitaxial Layers

Event-related desynchronization and synchronization in evoked K-complexes

Monte-Carlo aided design of neutron shielding concretes

Properties of Neutron Doped Multicrystalline Silicon for Solar Cells

Shallow Ohmic Contact System to n-GaAs

Interaction of Au with GaSb and its Impact on the Formation of Ohmic Contacts

Materials Technology for GaSb-Based optoelectronic Devices

Planar Optical Waveguides for Application in Optoelectronic Gas Sensors