Search results for "Chopper"
showing 7 items of 7 documents
Robust current observer design for DC-DC converters
2014
In recent years several fast response controllers have been proposed for DC-DC converters. The majority of them rely on a cascade control structure involving the inductor's current in the control function as its faster dynamics, respect to output voltage, allows a significant increase in the regulation performance; the drawback is the need of a proper and expensive current sensor. In this paper a simple and robust formulation for the design of a current observer, based on the output voltage measurement is presented. The formulation is common for the three standard DC-DC converters and the resulting observer is robust to load variation. The observers have been tested in a cascade PI control …
Justification of Construction Parameters of the Screen in the Small-Sized Household Biomass Chopper
2019
The mechanism of influence of screen design parameters on the technological process and the particle size distribution of the chopped biomass were determined in this research. The presented engineering solutions make it possible to design the screen for chopping the given biomass material. The modernized construction expands the scope of application of small-sized chopper, especially when used in private farm households. Size control of the chopped material allows to use material as fuel, material for mulching of berry plantations and gardens, material for production of constructional and insulating wood concrete.
Non-Waste Technology for Utilization of Tree Branches
2022
The trees (e.g., fruit or decorative) growing on the homestead plots of private households provide opportunities for sustainable biomass obtained from pruned branches every year. Profitable production of fuel material requires high-performance equipment and methods by which wood chips can be produced at low cost. The practice of chopping tree branches shows that not all chopping machines are suitable for use on homestead plots. This research gives the five-year test results of a developed and patented tree branch chopping machine under special operating conditions. The machine was tested under the conditions of the homestead plot of a private household in the Poltava region, and the enginee…
Effects of Frequency Dependence of the External Quantum Efficiency of Perovskite Solar Cells
2018
Perovskite solar cells are known to show very long response time scales, on the order of milliseconds to seconds. This generates considerable doubt over the validity of the measured external quantum efficiency (EQE) and consequently the estimation of the short-circuit current density. We observe a variation as high as 10% in the values of the EQE of perovskite solar cells for different optical chopper frequencies between 10 and 500 Hz, indicating a need to establish well-defined protocols of EQE measurement. We also corroborate these values and obtain new insights regarding the working mechanisms of perovskite solar cells from intensity-modulated photocurrent spectroscopy measurements, iden…
Eresus kollari (Araneae: Eresidae) calls for heathland management
2011
Northwest Europe’s largest heather-dominated sandy habitats are located in the nature reserve Lu¨neburgerHeide, Germany. Yet, even these appear to be losing their ability to support some of their stenotopic species such as theladybird spider, Eresus kollari Rossi 1846, and are thus becoming increasingly important for the preservation of thesespecies. The habitat requirements of this endangered spider species were investigated in order to obtain data that will helpstabilize the last remnants of the species’ population in northwest Germany. Several heathland habitats were surveyed bypitfall trapping during the mate-search period of the males. Two statistical methods were applied: logistic reg…
An optical device for ultra-cold neutrons - Investigation of systematic effects and applications
2010
We developed an optical device for ultra-cold neutrons and investigated the influence of a tilt of its guiding components. A measurement of the time-of-flight of the neutrons through the device by means of a dedicated chopper system was performed and a light-optical method for the alignment of the guiding components is demonstrated. A comparative analysis of former experiments with our results shows the potential of such a device to test the electrical neutrality of the free neutron on the $10^{-22} q_{\rm e}$ level and to investigate the interaction of neutrons with gravity.
Scientific and methodical foundations of heat saving of rural territories on the basis of use of local biomass
2018
W ostatnich latach gaz ziemny na Ukrainie, a w szczególności w regionie połtawskim,wykorzystywany jest najczęściej do ogrzewania prywatnych domów. Niestety co roku państwo podnosi cenę gazu. Koszty ogrzewania stają się dla mieszkańców wsi dużym obciążeniem. Wcześniej na wsi tradycyjnie budowano domy o dużej powierzchni. Dlatego obecnie wspólnoty terytorialne szukają alternatywnych sposobów ogrzewania. W celu oszczędzania ciepła ważnymi dla nich stają się zagadnienia związane z izolacją budynków mieszkalnych, zakładów produkcyjnych. Głównym celem artykułu jest analiza możliwości wykorzystania biomasy jako materiału termoizolacyjnego oraz źródła energii alternatywnej. Przedstawiono doświadcze…