Przeglądanie według Autor "Cholewa, Marian"

Aktualnie wyświetlane 1 - 5 z 5

Characteristics of TiO2, Cu2O, and TiO2/Cu2O thin films for application in PV devices
(AIP Advance, 2019) Sawicka-Chudy, Paulina; Sibiński, Maciej; Pawełek, Ryszard; Wisz, Grzegorz; Cieniek, Bogumił; Potera, Piotr; Szczepan, Patryk; Adamiak, Stanisław; Cholewa, Marian; Głowa, Łukasz
Several Cu2O and TiO2 thin films and four additional TiO2/Cu2O structures were fabricated by direct current (DC) magnetron sputtering. The process parameters were selected on the basis of earlier studies and numerical simulations. We examined the morphology of a cross-section of the PV structures, roughness and topography, and the transmission spectra of the thin films. Additionally, the properties of the samples were determined by X-ray diffraction. Next, the morphology cross-sectional and layer compositions of the solar cells was evaluated by scanning electron microscopy. Only one of the TiO2/Cu2O structures appeared smooth and homogeneous with columnar-type growth. For the as-grown films, diffraction peaks were observed and identified as brookite, rutile, CuO, and Cu2O and the average roughness of the samples was 0.5, 1.2, 5.4, and 4.0 nm, respectively. Finally, the transmission spectra of the thin films were recorded. Transmission and reflection spectra of ultraviolet-visible spectroscopy were analyzed, and the optical band gap and absorption coefficient of the oxidized layers were calculated. In the region of 400 to 1000 nm, transmittance varied from 5% to 70% in the TiO2 samples, and from 15% to 40% in the Cu2O samples, and reflectance of the TiO2 and Cu2O samples ranged from 20% to 90%. In the region of 1.5 eV to 3.5 eV, the mean absorption coefficient varied from ∼105 1/cm to ∼3 · 105 1/cm for TiO2 thin film, and from ∼2 · 105 to ∼6 · 105 1/cm for Cu2O thin film. The optical band gap values of the samples shifted slightly toward bulk anatase-3.5 eV, bulk rutile-3.1 eV, and copper(I) oxide. Finally, silver contacts were used for the electrodes. One of the fabricated TiO2/Cu2O PV structures was found to be sensitive to electromagnetic radiance during the experiment.
Comparison of Solar Tracking System Solar Tracking System and Fixed Photovoltaic Modules in Lodz
(Journal of Solar Energy Engineering, 2018-01) Sawicka-Chudy, Paulina; Sibiński, Maciej; Cholewa, Marian; Pawełek, Ryszard
The world energy consumption has exhibited high growth over the last several decades. Alternative energy sources like photovoltaic (PV) systems generate electricity, reduce pollution air, and have little environmental impact. The commonly used fixed-tilt solar panels, however, have low efficiency and high production cost. Thus, it takes a long time to obtain a return on the investment. Solar trackers increase the efficiency of PV systems and are therefore more attractive from a financial point of view. In order to design tracking systems that will be efficient, it is necessary to analyze the results during various periods during the year and over their lifespan. Thus, we performed a comparative study between fixed-tilt panels and the tracking system installed in Lodz, Poland. Fixed-tilt panels are at normal to the Earth's surface (90 deg from horizontal plane) and are attached to a building façade, azimuth 180 deg (S direction) with 15 cm ventilation gap so slight efficiency drop may be presumed. We performed short- and long-term analyses of the solar tracking and fixed-tilt systems, which allowed us to conclude that the panels tracking the sun had an additional gain of energy during the year as compared to the fixed-tilt panels. During some months, however, the solar tracking system did not produce as much energy as the fixed-tilt, vertically positioned panels. These results might be useful in designing and constructing solar tracking PV systems.
How electromagnetic fields can influence adult stem cells: positive and negative impacts
(Stem Cell Research & Therapy, 2016-04-18) Maziarz, Aleksandra; Kocan, Beata; Bester, Mariusz; Budzik, Sylwia; Cholewa, Marian; Ochiya, Takahiro; Banas, Agnieszka
The electromagnetic field (EMF) has a great impact on our body. It has been successfully used in physiotherapy for the treatment of bone disorders and osteoarthritis, as well as for cartilage regeneration or pain reduction. Recently, EMFs have also been applied in in vitro experiments on cell/stem cell cultures. Stem cells reside in almost all tissues within the human body, where they exhibit various potential. These cells are of great importance because they control homeostasis, regeneration, and healing. Nevertheless, stem cells when become cancer stem cells, may influence the pathological condition. In this article we review the current knowledge on the effects of EMFs on human adult stem cell biology, such as proliferation, the cell cycle, or differentiation. We present the characteristics of the EMFs used in miscellaneous assays. Most research has so far been performed during osteogenic and chondrogenic differentiation of mesenchymal stem cells. It has been demonstrated that the effects of EMF stimulation depend on the intensity and frequency of the EMF and the time of exposure to it. However, other factors may affect these processes, such as growth factors, reactive oxygen species, and so forth. Exploration of this research area may enhance the development of EMFbased technologies used in medical applications and thereby improve stem cell-based therapy and tissue engineering.
Magnetic Resonance Elastography – noninvasive method to assess liver disease
(Wydawnictwo Uniwersytetu Rzeszowskiego, 2017) Ożóg, Łukasz; Aebisher, David; Bober, Zuzanna; Bartusik-Aebisher, Dorota; Guz, Wiesław; Cholewa, Marian
Currently, liver disease is widespread and the awareness of these diseases is low. Early symptoms of liver disease do not necessarily indicate problems with this organ and patients are usually informed of their problems when the stage of the disease is already advanced. Invasive biopsies are the clinical diagnostic method most commonly used in the evaluation of liver disease. A biopsy is associated with a high risk of false results and additional complications. Finding new non-invasive imaging methods has led to the discovery of a new method called Magnetic Resonance Elastography (MRE). This technique allows one to evaluate the mechanical properties of tissues and to distinguish between pathological states. Testing using this technique can be performed on a conventional magnetic resonance system by using few additional components and properly prepared software. Studies have shown that there is a strong correlation between MRE-measured liver stiffness and the degree of fibrosis. MRE is also useful in characterizing liver tumors. Studies show that this technique is highly credible in both health volunteers and patients with liver fibrosis. MRE has tremendous diagnostic potential. The described technique is not currently widely used and has the potential to serve as a safe and accurate alternative in clinical diagnostics in the future.
Review of the development of copper oxides with titanium dioxide thin-film solar cells
(2020) Sawicka-Chudy, Paulina; Sibiński, Maciej; Rybak-Wilusz, Elżbieta; Cholewa, Marian; Wisz, Grzegorz; Yavorskyi, Rostyslav
Copper oxide-titanium dioxide (TiO2) p–n junctions are promising materials for photovoltaic devices and may reduce production costs due to their low cost and inexpensive production methods compared with silicon solar cells. The present review compares solar cells made with copper oxides combined with TiO2–TiO2/Cu2O and TiO2/CuO heterojunctions, and “cascade heterojunction systems.” First, we describe the main properties of titanium (iv) dioxide (TiO2), cuprous oxide (Cu2O), and cupric oxide (CuO), and their potential applications. Next, we explain the concept of copper oxide and TiO2 heterojunctions. We summarize and present the photovoltaic characteristics (efficiency, fill factor, circuit current density, and open circuit voltage), thickness, preparation method, and electrode type for solar cells comprising copper oxide and TiO2. The efficiency of the solar cells ranged from 0.0005% to 1.62%. The thickness of the TiO2 and cupric oxide layers ranged from 0.06 to 16 µm, and from 0.18 to 1.5 µm, respectively, depending on the fabrication method. Additionally, we review and discuss the available combinations of copper oxide with other materials (Cu2O with ZnO, CuO with ZnO, and CuO with Si), as well as the effect of the thickness of the copper (i) oxide and copper (ii) oxide on the solar cell performance. Finally, we present aspects to improve the conversion efficiency of heterojunction solar cells with copper oxides combined with TiO2. This review will be useful for the construction and further development of thin-film solar cells.