Building nonparametric nn-body force fields using Gaussian process regression

Constructing a classical potential suited to simulate a given atomic system is a remarkably difficult task. This chapter presents a framework under which this problem can be tackled, based on the Bayesian construction of nonparametric force fields of a given order using Gaussian process (GP) priors. The formalism of GP regression is first reviewed, particularly in relation to its application in learning local atomic energies and forces. For accurate regression it is fundamental to incorporate prior knowledge into the GP kernel function. To this end, this chapter details how properties of smoothness, invariance and interaction order of a force field can be encoded into corresponding kernel properties. A range of kernels is then proposed, possessing all the required properties and an adjustable parameter $n$ governing the interaction order modelled. The order $n$ best suited to describe a given system can be found automatically within the Bayesian framework by maximisation of the marginal likelihood. The procedure is first tested on a toy model of known interaction and later applied to two real materials described at the DFT level of accuracy. The models automatically selected for the two materials were found to be in agreement with physical intuition. More in general, it was found that lower order (simpler) models should be chosen when the data are not sufficient to resolve more complex interactions. Low $n$ GPs can be further sped up by orders of magnitude by constructing the corresponding tabulated force field, here named "MFF".Comment: 31 pages, 11 figures, book chapte

A laboratory stand for automatic reading of the value measured by an analog meter

W artykule przedstawiono stanowisko do automatycznego odczytu wartości mierzonej miernikiem analogowym (woltomierz magnetoelektryczny). Do rejestracji obrazu zastosowano standardową kamerę internetową oraz oprogramowanie LabVIEW. Wykorzystano narzędzia z modułu NI Vision Development. Do detekcji wskazówki zastosowano transformatę Hougha. Przedstawiono wyniki badań wpływu parametrów rejestracji i przetwarzania obrazu oraz natężenia oświetlenia na detekcję wskazówki miernika analogowego.The paper presents an application for automatic reading of the measured value from an analogue meter. The software of the proposed application was developed in the LabVIEW environment using the NI Vision Development. For image acquisition the standard webcam was used (Fig.2). The analogue magneto-electric voltmeter with measuring ranges: 1,5 V; 3 V and 7,5 V was used as a testing instrument. The Hough transform (1) was applied to detection of the analogue meter indicator. Determination of the range of measurements was carried out using patternmatching methods. Fig. 5 presents the algorithm for determining the measuring range and the final value. The influence of illumination on the detection of the analog meter indicator was also examined. The obtained results are shown in Fig. 6. The analysis of the effect of the light intensity was made under artificial lighting. A digital luxmeter LUXMETER L-50 SONOPAN was used in the test procedure. The elaborated application (for the tested range 400-3000 lx) is fully useful for detection of image elements. The results of investigations of the influence of acquisition parameters and parameters of image processing on the detection of the analog meter indicator are included

Measuring methods of welding process parameters

The paper focuses on the problems of monitoring the resistance spot welding process of thin metal sheets used in aircraft structures. The welding process is conducted using welders with software control which allows the welding cycle to be established. Essential parameters in the welding process include: electrode profiles, establishing electrode force as well as the shape and the intensity of the current heating the weld. The paper proposes using a measurement system which registers the above-mentioned welding process parameters and utilises the modules of data acquisition, series NI 9215 operating in a set with NI cDAQ-9178. Software which uses the LabVIEW environment was implemented into the measurement system. The measurement of the welding current intensity was made using a Rogowski coil, while other measurement signals were obtained from the diagnostic interface of the programmable controller of the welder. The paper presents preliminary results of the research. The objective of the initial research is the preparation of a calibration method of welder measurement systems

Comparative analysis of the profitability of construction and use mikrobiogas plants for the agricultural farm of the holder 100 LU

Analizowano zasadność budowy i użytkowania dwóch wariantów mikrobiogazowni rolniczych w odniesieniu do gospodarstwa rolniczego specjalizującego się w chowie krów mlecznych o obsadzie 100 DJP. W wariancie I w mikrobiogazowni stosowano gnojowicę z gospodarstwa, a w wariancie II dodatkowo kiszonkę z kukurydzy, zakładając że sucha masa gnojowicy w komorze fermentacyjnej stanowi 40%, a sucha masa kiszonki z kukurydzy 60%. W wariancie I mikrobiogazowni można uzyskać 51 981,840 m3 biogazu i wyprodukować 82 890 kWh energii elektrycznej przeznaczonej do sprzedaży, podczas gdy w wariancie II produkcja biogazu może być czterokrotnie większa - 211 757,407 m3 , produkcja i sprzedaż energii elektrycznej może wynosić 337 667 kWh. Analiza finansowa w warunkach założonych wskaźników ekonomicznych funkcjonowania mikrobiogazowni (koszty substratów, cena giełdowa sprzedaży świadectw pochodzenia itd.) wykazała, że wzrost produkcji biogazu nie przekłada się na osiągnięcie przez biogazownię zysku operacyjnego. Biogazownia w wariancie I osiąga roczny zysk operacyjny po opodatkowaniu w kwocie 47 925,14 zł, natomiast w wariancie II biogazowni obliczono stratę w wysokości 93 201,18 zł. Prosty okres zwrotu wariantu I bazującego na fermentacji gnojowicy wynosi 6 lat i 290 dni, co jest wynikiem akceptowalnym. Dodatek kiszonki z kukurydzy do substratu, poza zwiększeniem uzysku biogazu, powoduje także negatywne skutki w postaci dodatkowych kosztów wynoszących 64 491 zł rocznie, co stanowi 20% całości rocznych kosztów funkcjonowania biogazowni.Was analyzed the legitimacy of the construction and operation of two variants of biogas plant for a farm specializing in the breeding of dairy cows with a cast of 100 LU. In the variant I used only the slurry holding, in the variant II using additional silage maize, assuming that the dry weight of the slurry in the digester is 40% of the dry weight of corn silage 60%. The biogas plant (variant I) allows you to get 51 981.840 m3 of biogas and produce 82 890 kWh of electricity to be sold, while in the variant II achieved a fourfold increase in the production of biogas to 211 757.407 m3 , production and sale of electricity in the amount of 337 667 kWh. Financial analysis for the assumed economic indicators functioning the biogas plant (cost substrates, the trading price of sale of certificates of origin etc.) showed that the increase in biogas production does not translate to reach the biogas operating profit. The biogas plant in the variant and has an annual operating profit after tax in the amount of 47 925.14 PLN, while the variant II biogas recorded a loss of 93 201.18 PLN. Simple payback option and based on the fermentation of manure is 6 years and 290 days which is the result acceptable. The addition of maize silage substrate in addition to increasing the yield of biogas also causes negative effects in the form of additional costs amounting to 64 491 PLN per year, which represents 20% of the total annual operating costs of the plant

Possible Causes of Asymmetry in the Mössbauer Spectra of~Brain Tissue

Iron present in the human brain plays important role in neurodegenerative diseases like Parkinson and Alzheimer diseases. Brain iron is mainly stored within globular protein called ferritin. Mössbauer spectra of brain tissue are asymmetric doublets at 300 K and 90 K. This asymmetry is slightly bigger in the case of samples taken from diseased subjects. Reason for this is still unknown. Few possible causes of aforesaid difference had been discussed. Nanometer-size of ferritin iron cores, pathological protein influence were taken into account. It was also discussed if experimentally available statistics is sufficient to obtain reliable asymmetry coefficient from Mössbauer spectra. Physical experiment were reproduced by means of computer simulations. Nevertheless, the reason for the asymmetry has not been completely elucidated yet

Mossbauer studies of Sołtmany meteorite - preliminary results

In Mossbauer spectra of the Sołtmany meteorite we identified four iron-bearing minerals: olivine, pyroxene, kamacite and troilite. The distribution of iron among these minerals is different in the Sołtmany meteorite from this distribution in the Baszkowka meteorite. As Sołtmany and Baszkowka meteorites are ordinary chondrites type L (both falls), differences in the distribution of iron over the four main iron-bearing mineral phases could be the basis for a new classification of L-type ordinary chondrites. Small amounts of taenite were also observed in the Sołtmany meteorite. The ratio of iron in kamacite and taenite in the Sołtmany meteorite was found to be about 3. No Fe3+ could be detected