Measurement of Inertia properties of bodies for the purpose of mathematical modeling of vehicle dynamics

Tato práce se zabývá návrhem metody, kterou lze měřit u součástí podvozků automobilů důležité mechanické veličiny -- souřadnice polohy těžiště a tenzor momentů setrvačnosti, a to v případě, kdy inženýr nemá k dispozici počítačový model dané součásti. Práce problém rozděluje do několika dílčích podproblémů, přičemž u každého je navržen postup, jak jej lze s dostatečnou přesností a zároveň s přijatelnou náročností vyřešit. Byly zhotoveny potřebné pomůcky a bylo provedeno měření součástí. V závěru jsou porovnány změřené hodnoty s teoretickými a je odhadnuta přesnost, které lze touto metodou měření docílit.The aim of the diploma thesis is to create a concept of methods that can be used for measurement of important mechanical inertia properties of bodies -- the coordinates of center of gravity and the the moment of inertia tensor, in case we don't have 3D model of these bodies. The thesis divides this problem into several sub-problems and suggests the solutions for each of them. Required equipment was created and measurement was carried out. At the end the measured values are compared with the teoretical ones and accuracy of this method is determined.

High autonomy and low accountability: Case study of five Czech schools

The paper aims to describe the effects of a unique combination of high autonomy and low outcome accountability of the Czech schools. First, the paper outlines test-based accountability as a key concept of contemporary educational policy. Next, the research design is briefly described and the qualitative data on the effects of school choice and curriculum autonomy / decentralisation are presented. The discussion stresses the problem of time frame in evaluating system wide interventions and also sketches a vision of new emerging school reform discourse. Processes of change in five Czech “combined” primary and lower secondary schools were studied by qualitative longitudinal multiple case study for over 5 years. Surprisingly, the results suggest that many negative effects ascribed to the highstakes tests (e. g. curriculum narrowing, fabrication of image) could be seen in the studied schools despite the different model of governance in the Czech Republic. The contemporary discussion of risks of (high stake) testing should be complemented by a similar analysis of both costs and negative effects of the absence of outcome accountability

Potatoes (Solanum tuberosum L.)

In the area of potato production, targeted research solving concrete and actual problems of potato producers runs on Czech University of Life Sciences in Prague. In the last few years, we were focused on the production of new potatoes designated for early harvest, and we were focused on capitalization of yielding and qualitative characteristics of colored potato variety. These findings were further utilized and transferred to the system of organic farming. Firstly, we watched the influence of organic farming on yield and quality of tubers. Ecological ways of cultivation had strong negative influences on yield (decrease of 36%). From qualitative characteristics, organic farming increased the content of polyphenols by 10.2%, decreased the content of nitrates by 11.0%, and decreased the content of reducing sugars by 22.0%. We also evaluated the possibilities and impacts of mulch on potato cultivation. The mulch on top of ridges affected the temperature of soil (it increased the temperature by 0.2–0.6 °C under black mulching nonwoven fabric, and it decreased by 0.5–0.8 °C under herbal mulch). The mulch also affected soil humidity (herbal mulch decreased the soil humidity) and adjust weed infestation (20 to 92% lower), soil erosion (95% lower), the occurrence of Colorado beetle (the number of larvae was 22.8% lower with herbal mulch and 88.7% higher with mulching textile), and late blight in potato vegetation

Simplified Analytical Calculation of PM Machines Magnetic Flux Leakage Factor

The permanent magnets used for generation of magnetic field in permanent magnet machines are placed in more or less magnetically conducting environment – electrical steel and air. This causes leakage of the magnetic flux from its desired path through the air gap. This paper describes simplified analytical calculation of magnetic properties of five most commonly used placements of permanent magnets and compares obtained leakage factors. A verification of the results via finite element method is also included

Effect of Different High-energy Grinding Technologies on Granulometric and Crystallographic Properties of Portland Cement

The present article deals with the effect of different high-energy grinding technologies through available laboratory mills on Portland cement's granulometric and crystallographic properties. Two types of commonly available laboratory mills were selected, namely the planetary mill and the vibratory mill. The type of laboratory mill used, the grinding environment, and the grinding time were monitored. The planetary laboratory mill with 10 mm in diameter grinding steel balls proved to be more efficient in the scope of material reduction, which effectively reduces the material, especially during wet grinding of the material. The agglomeration effect is significantly reduced, which is a big advantage of method of wet grinding

High autonomy and low accountability: Case study of five Czech schools

Článek upozorňuje na efekty vysoké úrovně autonomie při současné nízké odpovědnosti za výsledky v případě českých základních škol. Jsou načrtnuty základní principy akontability jako klíčového pojmu současné vzdělávací politiky a stručně je popsán použitý výzkumný plán. Pak jsou představena data ilustrující efekty volby školy, autonomie školy v oblasti alokace zdrojů a kurikulární decentralizace. V diskusi je mj. zmíněn problém časové škály pro hodnocení efektů reformy a otevřena otázka potřeby nového přístupu k autonomii a akontabilitě škol. Po dobu více než pěti let sledujeme za použití převážně kvalitativních longitudinálních postupů vývoj pěti českých plně organizovaných základních škol. Výsledky naznačují, že některé efekty, považované za negativní a připisované plošnému testování a na něj navázaným politikám, lze překvapivě pozorovat ve zkoumaných školách, ačkoli v český vzdělávací systém řadu prvků akontability nezavedl. Současná bohatá literatura o rizicích spojených s plošným testováním by si zasloužila doplnění o studie rizik a negativních efektů projevujících se tam, kde výsledky žáků nejsou systematicky sledovány a využívány.The paper aims to describe the effects of a unique combination of high autonomy and low outcome accountability of the Czech schools. First, the paper outlines test-based accountability as a key concept of contemporary educational policy. Next, the research design is briefly described and the qualitative data on the effects of school choice and curriculum autonomy / decentralisation are presented. The discussion stresses the problem of time frame in evaluating system wide interventions and also sketches a vision of new emerging school reform discourse. Processes of change in five Czech “combined” primary and lower secondary schools were studied by qualitative longitudinal multiple case study for over 5 years. Surprisingly, the results suggest that many negative effects ascribed to the highstakes tests (e. g. curriculum narrowing, fabrication of image) could be seen in the studied schools despite the different model of governance in the Czech Republic. The contemporary discussion of risks of (high stake) testing should be complemented by a similar analysis of both costs and negative effects of the absence of outcome accountability

Study on Mechanical Properties of Heap Deposited Fly Ash Based Geopolymers with Different Alkaline Activator Properties

Geopolymers can improve environmental protection and are therefore considered a 21st-century material that requires special attention. The main objective of this study was to examine the utilization of fly ash deposited on a heap as a potential raw material for the geopolymerization process. In this work, flexural and compressive strengths, as well as water absorption of geopolymers, were evaluated based on alkaline activator properties. Na2O content, SiO2/Na2O molar ratio and fly ash-to-water ratio were key observed factors. Mechanical strengths tests were conducted after 7, 28, 90, 180, and 360 days. The research findings showed that geopolymer cured at appropriate conditions and with a suitable alkaline activator can reach a compressive strength of more than 55 MPa. The presented study highlighted the possibility of the efficient use of fly ash to produce useful materials, i.e., geopolymers, which contribute to environmentally friendly solutions. This approach is fully in line with the principles of sustainable development

Verification and numerical simulation of advanced composite inlet in compliance of airworthiness impact requirements

Bird or hail stone strikes are an important phenomenon which must be considered during aircraft design. Most of major bird or hail strike incidents result from engine ingestion. As engines are the sole thrust providing mechanisms of an aircraft, it is critical to investigate and mitigate the effects of bird or hail strikes on engine inlets and systems to the greatest extent possible. The article presents application of test verified numerical simulation for design and full-scale test verification of advanced composite air inlet for new generation of jet trainer aircraft from point of view of high speed impact resistance. The physical bird and hail impact tests were performed at the Czech Aerospace Research Centre (VZLÚ) according to airworthiness requirements. The measurement during impact test were performed by high-speed camera, Fiber Bragg Grating (FGB) sensors and strain gauges in cooperation with Czech Technical University (CTU) in Prague. The results from full-scale bird and hail strike tests were compared with numerical simulation

IMRT using simultaneous integrated boost (66 Gy in 6 weeks) with and without concurrent chemotherapy in head and neck cancer – toxicity evaluation

AimTo evaluate the toxicity of intensity-modulated radiotherapy with simultaneous integrated boost (SIB-IMRT) in head and neck cancer patients treated using a protocol comprising 66 Gy to the PTV1 (planning target volume; region of macroscopic tumour) and 60 Gy and 54 Gy to the regions with high risk (PTV2) and low risk (PTV3) of subclinical disease in 30 fractions in six weeks.Material and MethodsBetween December 2003 and February 2006, 48 patients (median age 55; range 25–83, performance status 0–1) with evaluable non-metastatic head and neck cancer of various localizations and stages (stages: I–1; II–8; III–12; IV–27 patients, resp.) were irradiated according to the protocol and followed (median follow-up 20 months; range 4–42). Ten patients underwent concurrent chemotherapy (CT) and in 15 patients the regimen was indicated postoperatively because of close or positive margins. In all cases the regimen was used as an alternative to conventional radiotherapy (70 Gy in 7 weeks). The acute and late toxicities were evaluated according to RTOG and RTOG/EORTC toxicity scales, respectively.ResultsAll patients finished the treatment without the need for interruption due to acute toxicity. No patient experienced grade 4 toxicity. More severe acute toxicity was observed in patients with CT, but the most severe toxicity was grade 3. Grade 3 toxicity was observed in the skin, mucous membrane, salivary glands, pharynx/oesophagus and larynx in 8.4%, 35.4%, 39.6% and 2.1%, in the CT subgroup in 10%, 100%, 90%, 10%, respectively. The trend of impairment of acute toxicity by concurrent chemotherapy was statistically confirmed by Fisher's exact test (for mucous membranes p=0.000002 and pharyngeal/oesophageal toxicity p=0.0004). The most severe late toxicity was grade 2 subcutaneous tissue (34.2%), mucous membrane (36.8%) and larynx (11.1%), grade 3 in salivary gland (2.6%) and grade 1 in skin (84.2%) and spinal cord (5.4%). The late toxicity was not increased by chemotherapy.ConclusionIn light of the toxicity profile we consider the presented regimen to be an alternative to conventional radiotherapy 70 Gy in 7 weeks. The addition of CT requires more intensive supportive care

The role of different high energy ball milling conditions of molybdenum powder on the resulting particles size and morphology

High energy ball milling is a powder processing method in which the powder particle size can be decreased to micrometer size in a relatively short period of time. This method is based on the friction and the high energy kinetic collisions between the balls and the trapped powder particles. The milling process is influenced by many process variables such as mainly the rotational speed, ball to powder weight ratio and processing time. In the present study, high energy ball milling process was performed for molybdenum powder using a high energy ball mill under different milling conditions varying the: (i) rotational speed from 600 to 800 rpm, (ii) ball to powder weight ratio of 100:3 and 100:6, (iii) milling time in the range of 10 to 60 minutes, (iv) process control agent using polyethylene glycol, and (v) milling atmosphere under air or nitrogen. The used initial molybdenum powder was of globular morphology and 100 µm in particle size. The powders after milling were characterized by a scanning electron microscope (SEM) and a laser diffraction size analysis. The particle size of milled powders was decreased down to 1.1 µm. As the most effective ball to powder weight ratio was found 100:6 with the milling speed of 800 rpm. The milling time played a crucial role for the refinement of particles up to 45 min, where the further milling had negligible effect on the overall trend of particle size evolution