Low-temperature magnetism of alabandite : Crucial role of surface oxidation

Manganese(II) monosulphide crystallizes into three different polymorphs (alpha-, beta-, and gamma-MnS). Out of these, alpha-MnS, also known as mineral alabandite, is considered the most stable and is widespread in terrestrial materials as well as in extraterrestrial objects such as meteorites. In this study, a low-temperature antiferromagnetic state of alpha-MnS was investigated using macroscopic magnetic measurements as induced and remanent field-cooled (FC) and zero-field-cooled (ZFC) magnetizations and magnetic hysteresis. Both natural alabandite and synthetic samples show (i) Néel temperatures in a narrow temperature range around 153 K and (ii) a rapid increase of the magnetization around 40 K. An anomalous magnetic behavior taking place at about 40 K was previously ascribed to the magnetic transition from a high-temperature antiferromagnetic to a low-temperature ferromagnetic state documented for non-stoichiometric alpha-MnS slightly enriched in manganese. However, our detailed microscopic observations and, in particular, oxidation experiments indicate that the anomalous magnetic behavior around 40 K is caused by a presence of oxide layer of ferrimagnetic hausmannite (Mn3O4) on the surface of alpha-MnS rather than being an intrinsic property of nearly stoichiometric alpha-MnS.Peer reviewe

Analysis and modelling of single domain core-shell (αFeNi/chromite) nanoparticles emitted during selective laser melting, and their magnetic remanence

Despite recent intense implementation of increasingly eco-friendly additive manufacturing, the properties of nanoparticulate pollutants emitted during Laser Powder Bed Fusion are still not fully understood, and have generally been overlooked. This study aims to fill this gap in current research by providing new insights into distinct metal/oxide core-shell nanoparticles (3–36 nm) that are produced during 3D printing using stainless steel. It also suggests possible ways for the removal of these potentially harmful by-products. Further, this research also provides a newly developed kinetic model that predicts a metal core growth time of below 200 μs and confirms the predicted theory for the formation of these by-products. In the current study it was found that the cores produced during this process are purely metallic and consist of meteoroid phase kamacite (αFeNi). Within this study there was found to be a complete dominance of single-domain cores of kamacite with prevailing particles below the superparamagnetic threshold showing strong magnetic response and remanence. This new knowledge can be used to minimize potential health risks and reduce contamination of raw materials by this nanoparticulate pollutant, which can adversely affect the quality of printed metal parts, the environment, and the health of the operator. These findings also provide a new possibility of targeted efficient production of superparamagnetic core-shell nanoparticles with a metallic kamacite core during laser powder bed fusion of austenitic steel 316L powder, which can be used in the production of sensors.Web of Science400art. no. 13668

Verification of the commercial potential of the project - Agro-Photovoltaic facilities

This thesis aims to verify the commercial potential of the project on Agro-Photovoltaic devices. In the first parts of the thesis, the author will focus on the literature review for the different points of the thesis, such as setting up the commercial process and its verification. Subsequently, it will focus on defining the business models, which are necessary for this project and will be used in the implementation. Subsequently, a survey of the business environment will be conducted. In the case of the implementation of a certain commercial project, it is necessary to know the environment of the company in order to subsequently choose the right business model. In the practical part, a database of potential customers will be created based on the data obtained from the market analysis, which will provide sufficient information about the customers. Based on the responses when addressing this database, the author will conduct semi-structured in-depth interviews to verify whether the respondents have shown interest in the project and confirmed the functionality of the business model. The conclusion of this thesis will be to evaluate the feasibility of this project and to verify whether this project has commercial potential.Tato práce má za cíl ověřit komerční potenciál projektu Agro-fotovoltaických zařízení. V první části práce se autor zaměří na literární rešerši pro jednotlivé body práce, jakožto nastavení obchodního procesu a jeho ověření. Následně se bude věnovat definování business modelů, který z nich je pro tento projekt nezbytný a bude využit při realizaci. Následně bude proveden průzkum podnikatelského prostředí. V případě realizování určitého komerčního projektu je nutné znát okolí podniku k tomu, aby mohl být následně zvolen správný business model. V praktické části bude na základě údajů vytvořena databáze potenciálních zákazníků Získaných z analýzy trhu, která poskytne dostatečné množství informací o zákaznících. Podle odpovědí při oslovování této databáze, autor vypracuje polostrukturované hloubkové rozhovory, které ověří, zda se respondenti projevili zájem o tento projekt a potvrdili funkčnosti business modelu. Závěrem této práce bude zhodnocení realizovatelnosti tohoto projektu a ověření, zda má tento projekt komerční potenciál

Verification and estimation of uncertainties of Tobias Mayer's 18th century astronomical observations

Perceiving the uncertainty of the measurement has been changing over the past centuries, reflecting the advancement in the experimental techniques, the urge for reliable and reproducible measurement methodology, and development of mathematical data processing and evaluating algorithms. From the historical perspective, the concepts of considering the measurement uncertainty were firstly introduced with geographic and cartographic measurements. In this context, the works of Tobias Mayer on lunar landscape measurements are widely highlighted which, at that time, presented innovative approaches in data processing with the method of averages and pioneeringly addressed the issue of measurement error. In this study, we analyze in details the Mayer’s set of 27 non-linear equations with 3 unknown parameters and discuss the effect of Mayer’s linearization and subsequent mathematical procedures on the accuracy of the parameter values in contrast with the results from rigorous treatment of non-linear regression model involving the least-square method. In particular, we compare the values of the unknown parameters and their uncertainties in several variants in the linearized and non-linearized model, providing monitoring of a small deviation of the Mayer’s linearization. The results, presented here, show that despite the conceptual and computational simplification of the Mayer’s method, such an approach to data processing can be exploited, with an acceptable level of accuracy, in several practical situations even today

Řešení problému magnetického indukčního ohřevu metodami vícerozměrných Fredholmových integrálních rovnic: Alternativní přístup k optimalizaci a hodnocení výkonnosti procesu

Induction heating is a frequently used technology in both fundamental and applied research. It is heavily exploited in the industry for processing materials by heat treatments. In addition, it is viewed as a promising tool in medicine, particularly as a part of therapeutic strategies for treating cancer diseases. Thus, in order to optimize (i.e., enhance and tune) the performance of the induction heating process, several aspects must be considered, including the design of the magnetic coils, features of the magnetic fields applied, coupling of magnetic and thermal fields, and the material's characteristics. To tackle this complex problem, numerical mathematical models are often used. The results of which can help in understanding the role of the various parameters on the performance of the induction heating. Here, we present an alternative mathematical approach to solve the induction heating problem using Fredholm integral equations of the second kind with a singular kernel. To reduce the computation time, the Nystrom method has been adopted. As the kernel function shows a singularity, a singularity subtraction has been involved in the developed mathematical procedure. Furthermore, the error features of the Nystrom method with the singularity subtraction have been described, and convergence conditions of the proposed computational algorithm have been thoroughly identified. Although special conditions for the kernel function and the integration rule are needed, the method shows lower computing times, competing well with those of traditional finite-element based routines. The applicability of the developed methodology is demonstrated for the simulation of induction heating the body of a metal object.Indukční ohřev je často používanou technologií v základním i aplikovaném výzkumu. V průmyslu je hojně využíván pro zpracování materiálů tepelným zpracováním. Kromě toho je vnímán jako slibný nástroj v medicíně, zejména jako součást terapeutických strategií pro léčbu nádorových onemocnění. Aby bylo možné optimalizovat (tj. zlepšit a vyladit) výkon procesu indukčního ohřevu, je třeba vzít v úvahu několik aspektů, včetně konstrukce magnetických cívek, vlastností použitých magnetických polí, propojení magnetických a tepelných polí a vlastnosti materiálu. K řešení tohoto složitého problému se často používají numerické matematické modely. Jejich výsledky mohou pomoci pochopit roli různých parametrů na výkon indukčního ohřevu. Zde uvádíme alternativní matematický přístup k řešení problému indukčního ohřevu pomocí Fredholmových integrálních rovnic druhého druhu se singulárním jádrem. Pro zkrácení doby výpočtu byla přijata metoda Nystrom. Protože funkce jádra ukazuje singularitu, bylo do vyvinutého matematického postupu zahrnuto odečítání singularity. Dále byly popsány chybové vlastnosti Nystromovy metody s odečítáním singularity a byly důkladně identifikovány podmínky konvergence navrženého výpočetního algoritmu. Ačkoli jsou nutné speciální podmínky pro funkci jádra a integrační pravidlo, metoda vykazuje nižší výpočetní časy, které dobře konkurují těm tradičním rutinám založeným na konečných prvcích. Je demonstrována použitelnost vyvinuté metodiky pro simulaci indukčního ohřevu tělesa kovového předmětu

Is There Still a Place for Brachytherapy in the Modern Treatment of Early-Stage Oral Cancer?

Brachytherapy (BT) involves the direct application of radioactive sources to the tumour. This technique is characterised by a steep dose gradient, the delivery of high-dose radiation to the target volume centre, and the sparing of surrounding healthy tissues. Low-dose-rate (LDR) BT and manual afterloading played an important role in the treatment of early-stage oral cancer, with treatment outcomes that were comparable to surgery. Interest in BT as a primary treatment for oral cancer has declined in recent years due to the emergence of better surgical techniques, the switch from LDR BT to high-dose-rate (HDR) BT (which has a higher risk of complications), and to advances in external beam radiotherapy (EBRT). At present, the main indications for BT are in the postoperative setting due to the superior dose conformity and better quality of life offered by BT versus EBRT. Postoperative BT can be administered as monotherapy in early-stage (T1N0) cancers and in combination with elective neck dissection or EBRT to treat larger or deeper tumours. BT yields excellent results for lip carcinoma in older patients and in tumours with unfavourable localisations. BT is an effective salvage therapy for local recurrences in previously-irradiated areas. Despite its many advantages, brachytherapy is a complex treatment requiring meticulous technique and close cooperation between the radiation oncologist, physicist, and surgeon