Measurement of airflow and pressure characteristics of a fan built in a car ventilation system

The aim of this study was to identify a set of operating points of a fan built in ventilation system of our test car. These operating points are given by the fan pressure characteristics and are defined by a pressure drop of the HVAC system (air ducts and vents) and volumetric flow rate of ventilation air. To cover a wide range of pressure drops situations, four cases of vent flaps setup were examined: (1) all vents opened, (2) only central vents closed (3) only central vents opened and (4) all vents closed. To cover a different volumetric flows, the each case was measured at least for four different speeds of fan defined by the fan voltage. It was observed that the pressure difference of the fan is proportional to the fan voltage and strongly depends on the throttling of the air distribution system by the settings of the vents flaps. In case of our test car we identified correlations between volumetric flow rate of ventilation air, fan pressure difference and fan voltage. These correlations will facilitate and reduce time costs of the following experiments with this test car

Vladislav Vančura v literárním kontextu 20. století

Title in English: Vladislav Vančura in the Literary Context of the 20th Century On June 23, 2021, it was the 130th anniversary of Vladislav Vančura’s birth, and June 1, 2022, was the 80th anniversary of his death. These anniversaries became the impetus for a collective volume entitled Vladislav Vančura in the Literary Context of the 20th Century. The editor Jiří Poláček approached researchers from various disciplines from literary studies to linguistics and to theatre studies with an appeal to think and rethink the literary and general cultural legacy of this important figure. The book volume by the team of researchers from six Czech universities is an attempt to reflect on the oeuvre by Vančura from the perspective of the current state of knowledge in literary studies and the broader context of the 20th century. The image of Vladislav Vančura within the context of the previous century arises from 15 texts by 15 authors, organized into four thematic blocks

Praktické zkušenosti s blokovou metodou analytické aerotriangulace

485

Technologie kancelářského zpracování číselné technicko-hospodářské mapy

32833

Organizace polních měřičských prací při THM, systém kontrol a příprava dat při vyhodnocení automatickým koordinátografem

24925

Intraclutch eggshell colour variation in birds: are females able to identify their eggs individually?

Background One possibility suggested regarding female post-mating strategies is differential allocation into offspring investment. Female birds produce not only the largest, but also most colourful eggs of all oviparous taxa. Larger eggs provide space for bigger embryos, or more nutrition for their development, but the question why eggs are more colourful and why there is variation in eggshell colouration remains. In this context, the focus of interest has been to explain inter-clutch variation but in many bird species, eggshell colouration also varies within a clutch. Surprisingly, less attention has been paid to this phenomenon. Therefore, we propose the “female egg recognition” hypothesis, suggesting that mothers use colour characteristics to interpret egg attributes and allocate further investment into each egg accordingly. To evaluate the feasibility of the hypothesis, we tested several underlying predictions and examined their suitability using a dataset from our tree sparrow (Passer montanus) study. We predict (i) substantial within-clutch variation in eggshell colouration which, (ii) should be related to laying sequence, (iii) reflect egg quality and, (iv) should stimulate a female response. Methods Eggshell coloration data were obtained via digital photography under standardized conditions, taken after clutch completion. Lightness (L*), representing the achromatic properties of an egg has been chosen as the most important predictor in dark cavities and was related to egg quality and position in the nest. Results In our tree sparrows, first and mainly last eggs were less pigmented, providing information about laying order. Egg volume, which predicts chick quality, positively correlates with eggshell coloration. Finally, we could show that female tree sparrows placed darker, but not bigger, eggs into more central incubation positions. Discussion All basic prerequisites for the “female egg recognition” hypothesis are fulfilled. In this context practicability and feasibility of the hypothesis and alternative explanations are discussed. However future work is necessary to determine a direct effect on offspring condition

Dynamické síly působící v nestabilním řezu při soustružení

Při soustružení i frézování se často technologové setkávají s chvěním existujícím pouze v době obrábění. Jde o samobuzené kmitání nástroje vůči obrobku. Výsledkem je velmi zvlněný povrch obrobku nepřijatelný jak při hrubování tak při dokončování. Tento druh kmitání se objevuje při všech obráběcích operacích. Při soustružení a frézování je nejčastější. Kmity ohrožují lomem řezné břity a působí nepříjemně na obsluhu silným hlukem. Existuje řada metod potlačení samobuzeného kmitání. Známé jsou frézovací nástroje s nepravidelnou roztečí zubů nebo s proměnlivým stoupáním šroubovice. Používají se i tlumené nástroje. Jmenované prostředky potlačuji samobuzené kmitání přímo při obrábění. Při programování pomocí CAM systémů je možné použít předpovědi stabilních, či naopak nestabilních řezných podmínek a zajistit tak bezproblémové obrábění. K tomuto účelu se používá diagram stability, zobrazující mezní šířku třísky (soustružení) nebo axiální hloubku řezu (frézování) v závislosti na otáčkách obrobku nebo nástroje. Diagram se vypočítává na základě měření frekvenčního přenosu mezi nástrojem a obrobkem. Přesnost výpočtu záleží na tvaru matematického modelu dynamické složky řezné síly. Tento příspěvek referuje o experimentech s novým tvarem modelu řezné síly. Na základě analýzy předchozích i současných naměřených dat se ukazuje, že v řezu působí několik vzájemně fázově posunutých sil, které ovlivňuji přesnost predikce stabilních řezných podmínek

Measurement of airflow and pressure characteristics of a fan built in a car ventilation system

The aim of this study was to identify a set of operating points of a fan built in ventilation system of our test car. These operating points are given by the fan pressure characteristics and are defined by a pressure drop of the HVAC system (air ducts and vents) and volumetric flow rate of ventilation air. To cover a wide range of pressure drops situations, four cases of vent flaps setup were examined: (1) all vents opened, (2) only central vents closed (3) only central vents opened and (4) all vents closed. To cover a different volumetric flows, the each case was measured at least for four different speeds of fan defined by the fan voltage. It was observed that the pressure difference of the fan is proportional to the fan voltage and strongly depends on the throttling of the air distribution system by the settings of the vents flaps. In case of our test car we identified correlations between volumetric flow rate of ventilation air, fan pressure difference and fan voltage. These correlations will facilitate and reduce time costs of the following experiments with this test car