Monitoring of Solder Spreading Velocity on Metal Surface

Práce se zabývá sledováním rychlosti roztékání pájky po povrchových úpravách NiAu, OSP, Sn nanesených na Cu plátovaném základním materiálu FR4 pomocí digitálních kamer. Po procesu přetavení je měřena délka roztečení pájky a velikost smáčecího úhlu. Vyhodnocuje a porovnává časové závislosti rychlosti roztečení pájky, délky roztečení pájky a smáčecí úhel pro povrchové úpravy NiAu, OSP, Sn při různých teplotách přetavení a ošetření povrchu.This work deals with flushing monitoring of spreading velocity on solder finishes Niau, OSP, Sn deposited on copper plated base material FR4 using digital cameras. After the reflow process is measured by length of spreading solder and size of wetting angle. It evaluates and compares the time dependence of velocity of spreading solder, length of solder spreading and wetting angle for NiAu, OSP, Sn finishes at different temperatures reflow and surface treatment.

FR4 base material - evaluation of flame retardant properties

Práce se zabývá zkoumáním hořlavosti materiálů FR4 (EN 61248–2–8) od různých výrobců, porovnávaná jejich samozhášivé vlastnosti s normami a údaji od výrobce. Vyhodnocuje vliv šířky a délky vodiče na maximální možné proudové zatížení spojené se vznikem hoření a dále porovnává vliv nepájivé masky na zkoumaných materiálech FR4.This work examines the flammability material FR4 (EN 61248-2-8) from different manufacturers, comparing their self-extinguishing properties to the standards and information from the manufacturer. Assesses the impact of latitude and longitude leads to the maximum possible current load associated with the occurrence of burning and compares the influence of the examined solder mask materials FR4.

Mormonism in the context of christian theology

Katedra občanské výchovy a filosofiePedagogická fakultaFaculty of Educatio

Extension of Centrifugal Compressor Operational Stability

Odstředivé kompresory s vysokým stlačením jsou používány v malých leteckých turbínových motorech a turbodmychadlech. Při vysokých otáčkách ale mají úzký rozsah stabilní práce a běžně používané kompresory s dozadu zahnutými lopatkami nejsou schopny požadovaný rozsah stabilní práce zajistit. Za účelem jeho rozšíření jsou používána některá antipumpážní opatření jako vnitřní obtokový kanál (OK, IRC), umístěný ve vstupu do kompresoru. Disertační práce je zaměřena na výzkum vlivu OK na provozní parametry odstředivého kompresoru. Nejprve byly různé geometrie OK zkoumány s využitím CFD výpočetních metod na zjednodušených modelech. Geometrie, jež dávala nejlepší výsledky z pohledu průtoku a ztrát v obtokovém kanále byla použita pro zkoušky na modelovém zařízení. Následně ta samá geometrie byla zkoušena na reálném kompresoru v experimentálním turbínovém motoru za účelem ověření vlivu na charakteristiku kompresoru - stlačení a účinnost. Současně byly prováděny 3D CFD analýzy OK s modelem oběžného kola kompresoru a výsledky porovnány s výsledky experimentu na modelu a kompresoru. Navíc bylo, s využitím tříotvorové tlakové sondy, provedeno měření proudového pole za výstupní štěrbinou z OK a porovnáno s průběhy rychlostí získanými z numerických simulací.Centrifugal compressors with high pressure ratio are widely used in small aircraft turbine engines and turbocharges. At high rotational speeds they have narrow stable operating region and commonly used impellers with back swept blades are not able to ensure requested stability. In order to achieve wider stable operating region, some other anti-surge measures can be used, such as an Internal Recirculation Channel (IRC) located in compressor impeller inlet. This thesis deals with an investigation of IRC influence on centrifugal compressor operational parameters. As a first, the various recirculation channel geometry was studied by using of CFD analysis on simplified computational models. Those geometry, which indicated best results in terms of mass flow and looses in channel were used for testing on a model test device. Subsequently the same geometry was tested on real centrifugal compressor in experimental turbine engine to verify influence of IRC on compressor performance map – pressure ratio and efficiency. Simultaneously the CFD analyses of IRC with a 3D model of compressor impeller were performed and results compared with those, gained from measurement on model and compressor. In addition the measurement of flow field downstream the recirculation channel outlet slot with using of 3-hole pressure probe was performed and compared with flow velocity profiles evaluated from numerical simulations.

The prediction of parking space availability

Intelligent Parking Systems (IPS) allow customers to select a car park according to their preferences, rapidly park their vehicle without searching for the available parking space (place) or even book their place in advance avoiding queues. IPS provides the possibility to reduce the wastage of fuel (energy) while finding a parking place and consequently reduce harmful emissions. Some systems interact with in-vehicle navigation systems and provide users with information in real-time such as free places available at a given parking lot (car park), the location and parking fees. Few of these systems, however, provide information on the forecasted utilisation at specific time. This paper describes results of a traffic survey carried out at the parking lot of supermarket and the proposal of the model predicting real-time parking space availability based on these surveyed data. The proposed model is formulated as the non-homogenous Markov chains that are used as a tool for the forecasting of parking space availability. The transition matrices are calculated for different time periods, which allow for and include different drivers’ behaviour and expectations. The proposed forecasting model is adequate for potential use by IPS with the support of different communication means such as the internet, navigation systems (GPS, Galileo etc.) and personal communication services (mobile-phones)

Novel Cytokinin Derivatives Do Not Show Negative Effects on Root Growth and Proliferation in Submicromolar Range

BACKGROUND: When applied to a nutrition solution or agar media, the non-substituted aromatic cytokinins caused thickening and shortening of the primary root, had an inhibitory effect on lateral root branching, and even showed some negative effects on development of the aerial part at as low as a 10 nanomolar concentration. Novel analogues of aromatic cytokinins ranking among topolins substituted on N9-atom of adenine by tetrahydropyranyl or 4-chlorobutyl group have been prepared and tested in standardized cytokinin bioassays [1]. Those showing comparable activities with N(6)-benzylaminopurine were further tested in planta. METHODOLOGY/PRINCIPAL FINDINGS: The main aim of the study was to explain molecular mechanism of function of novel cytokinin derivatives on plant development. Precise quantification of cytokinin content and profiling of genes involved in cytokinin metabolism and perception in treated plants revealed several aspects of different action of m-methoxytopolin base and its substituted derivative on plant development. In contrast to standard cytokinins, N9- tetrahydropyranyl derivative of m-topolin and its methoxy-counterpart showed the negative effects on root development only at three orders of magnitude higher concentrations. Moreover, the methoxy-derivative demonstrates a positive effect on lateral root branching and leaf emerging in a nanomolar range of concentrations, in comparison with untreated plants. CONCLUSIONS/SIGNIFICANCE: Tetrahydropyranyl substitution at N9-position of cytokinin purine ring significantly enhances acropetal transport of a given cytokinins. Together with the methoxy-substitution, impedes accumulation of non-active cytokinin glucoside forms in roots, allows gradual release of the active base, and has a significant effect on the distribution and amount of endogenous isoprenoid cytokinins in different plant tissues. The utilization of novel aromatic cytokinin derivatives can distinctively improve expected hormonal effects in plant propagation techniques in the future

Měření zemních proudových polí

Import 10/10/2012Prezenční410 - Katedra elektroenergetikyNeuveden