No (33507)
Number of found documents:
33507
Published from
to
Přeměny energie ve fyzice pohledem termokamery
2024 -
Příspěvek představuje jednoduché experimenty využitelné
ve výuce fyziky v souvislosti s vizualizací energetických pře měn – typicky jde o přeměny mechanické či elektrické ener gie na energii vnitřní. Kvalitativní pojetí experimentů umož ňuje jejich začlenění do výuky na základní i střední škole, a to
jak ve formě demonstrační, tak coby náměty na skupinovou
žákovskou práci.
Keywords:
experiment; výuka; fyzika
Available in the ZČU Library.
Přeměny energie ve fyzice pohledem termokamery
Příspěvek představuje jednoduché experimenty využitelné ve výuce fyziky v souvislosti s vizualizací energetických pře měn – typicky jde o přeměny mechanické či elektrické ener gie na energii vnitřní. ...
Porovnání tepelné vodivosti modelu jednoduchého a dvojitého okna
2024 -
Pokus je zaměřen na demonstraci rozdílu v přenosu tepla
mezi jednosklem a dvojsklem. V textu je seznam jednoduchých pomůcek a postup provádění experimentu, který je
doplněn fotografiemi a termogramy. Termogramy slouží
k vizualizaci rozdílu v chování mezi modelem jednoskla
a dvojskla. Vysvětlení je postaveno na rozdílu v tepelné vodivosti mezi polykarbonátem a vzduchem, spolu s porovnáním
měrné tepelné kapacity těchto dvou látek. Výsledky potvrzují,
že model dvojskla má nižší tepelné úniky v čase než model
jednoskla.
Keywords:
přenos teplo; jednosklo; dvojsklo
Available in the ZČU Library.
Porovnání tepelné vodivosti modelu jednoduchého a dvojitého okna
Pokus je zaměřen na demonstraci rozdílu v přenosu tepla mezi jednosklem a dvojsklem. V textu je seznam jednoduchých pomůcek a postup provádění experimentu, který je doplněn fotografiemi a ...
Computational and experimental assessment of natural frequencies in a bladed disk system
Mekhalfia, Mohammed Lamine; Procházka, Pavel; Maturkanič, Dušan; Voronova, Evgeniya; Hodboď, Robert
2024 - English
This paper examines the modal characteristics of a bladed disk in rotating machinery systems using a combination of analytical and experimental modal analysis methods. The analysis involves measuring natural frequencies and mode shapes under different operational conditions. A comparative analysis is conducted to assess modal properties obtained from both analytical and experimental approaches, while also considering the influence of rotation speed. Additionally, Finite Element Method (FEM) outputs are used to accurately position the strain gauge. Integrating these techniques provides a comprehensive understanding of the bladed disk's behaviour under varying rotational speeds, enhancing result accuracy and facilitating thorough investigation within rotating machinery systems.
Keywords:
natural frequencies; FEM; LDV; strain gauge
Available at various institutes of the ASCR
Computational and experimental assessment of natural frequencies in a bladed disk system
This paper examines the modal characteristics of a bladed disk in rotating machinery systems using a combination of analytical and experimental modal analysis methods. The analysis involves measuring ...
Flow simulations approach for flocculation tanks
Idžakovičová, Kristýna; Bílek, V.; Haidl, J.; Isoz, Martin; Pivokonský, M.
2024 - English
Flocculation in water treatment facilities plays a key role in the separation of colloidal inorganic and organic substances. Its optimization leads to a significant increase in its efficiency and savings of operational costs. However, it is currently based on trial-and-error experimental approaches. In this contribution, we focus on flow modeling in stirred flocculation tanks that would, after coupling with a calibrated model of particle aggregation, enable simulationbased flocculation optimization. Despite the abundance of literature on stirred tank modeling, there is no universal agreement on the methodology used to describe turbulence nor on the approach to the computational mesh creation. Consequently, there is no unified methodology for simulations and their validation. To address this, we present a best-practice methodology for economical, yet reliable flow simulations in the said device. This methodology includes the choice of the turbulence model, the approach to the design of a high quality mesh suitable for arbitrary geometries, and results evaluation. It is developed based on an extensive literature review, a multitude of flow simulations using several meshes of progressively higher quality and resolution, and various strategies to converge to steady-state flow conditions. The simulation quality indicators used here involve comparison with the experimental data on fluid velocity, stirrer power output, and flow rate through the impeller zone. Additionally, the resulting flow simulation models are compared using tracer transport simulations, hinting at their potential for coupling with particle aggregation models.
Keywords:
flocculation tank; stirring; MRF; CFD; OpenFOAM
Available at various institutes of the ASCR
Flow simulations approach for flocculation tanks
Flocculation in water treatment facilities plays a key role in the separation of colloidal inorganic and organic substances. Its optimization leads to a significant increase in its efficiency and ...
Development of a moodle online course for the subject of KMT/GKOB
2024 -
Keywords:
online kurz; Moodle; technická dokumentace; technické kreslení; grafická komunikace; online výuka; KMT/GKOB; Pedagogická fakulta; Západočeská univerzita v Plzni
Available in the ZČU Library.
Development of a moodle online course for the subject of KMT/GKOB
Firearms in Czech society, defence education at primary school
2024 -
Keywords:
střelné zbraně ve společnosti; branná výchova na základní škole; možnosti branné výchovy
Available in the ZČU Library.
Firearms in Czech society, defence education at primary school
Make it yourself: catalog of instructions for making didactic aids for the first grade of elementary school
2024 -
Keywords:
didaktika pracovních činností; první stupeň základní školy; materiály používané v pracovních činnostech; didaktická pomůcka; inkluzivní vzdělávání; specifické poruchy učení; tvořivost; motivace a pozornost žáků; jemná motorika; katalog
Available in the ZČU Library.
Make it yourself: catalog of instructions for making didactic aids for the first grade of elementary school
A New Hollow Fiber-Based Liquid-Phase Microextraction Method for the Determination of Antihypertensive Drug Lercanidipine in Biological Samples
Labzova, O.; Hrdlička, Vojtěch; Navrátil, Tomáš; Šelešovská, R.
2024 - English
A new hollow fiber-based liquid-phase microextraction (HF-LPME) method for the determination of antihypertensive drug lercandipine (LCN) in biological samples was developed. HF-LPME was\ncombined with optimized square wave voltammetry (SWV) on a cathodically pre-treated screenprinted boron-doped diamond electrode (SP-BDDE). Optimum HF-LPME conditions were:\nsupported liquid membrane (SLM) dodecane, 0.02 mol L-1 Britton-Robinson buffer (BRB, pH = 3) acceptor phase, BRB (pH = 7) donor phase, and time of extraction 30 min. Limits of quantification (LOQ) and detection (LOD) were 3.3 and 1.1 nmol L-1, respectively. The applicability of the developed method was verified on human urine, blood serum, and blood plasma with 20 and 100 nmol L-1 LCN addition.
Keywords:
Lercanidipine hydrochloride; Hollow fiber liquid-phase microextraction; Screenprinted boron-doped diamond electrode
Available on request at various institutes of the ASCR
A New Hollow Fiber-Based Liquid-Phase Microextraction Method for the Determination of Antihypertensive Drug Lercanidipine in Biological Samples
A new hollow fiber-based liquid-phase microextraction (HF-LPME) method for the determination of antihypertensive drug lercandipine (LCN) in biological samples was developed. HF-LPME was\ncombined with ...
Microstructure modifications of Al-Si-coated press-hardened steel 22MnB5 by laser welding
Šebestová, Hana; Horník, Petr; Mika, Filip; Mikmeková, Šárka; Ambrož, Ondřej; Mrňa, Libor
2024 - English
Weld microstructure depends on the characteristics of welded materials and parameters of welding technology, especially on the heat input that determines the peak temperature and the cooling rate. When the coated sheets are welded, the effect of the chemical composition of the coating must be also considered even though its thickness is only a few tens of microns. During 22MnB5+AlSi laser welding experiments, the ferrite-stabilizing elements of coating modified the weld metal microstructure. Ferrite appeared in a quenched weld metal. The rapid cooling rate accompanying welding with a focused beam limited the homogenization of the weld metal which resulted in the formation of ferritic bands in the regions rich in Si and especially in Al. On the other hand, a high level of homogenization was reached when welding with the defocused beam. The ferritic islands uniformly distributed in the weld metal were formed at 0.4 wt% and 1.6 wt% of Si and Al, respectively. The doubled heat input reduced the Al content to 0.7 wt% insufficient for the ferrite formation at still relatively high cooling rates. Predicting the distribution of ferrite in the weld metal is challenging due to its dependence on various factors, such as cooling rate and the volume of dissolved coating, which may vary with any modifications made to the welding parameters.
Keywords:
laser welding; high-strength steel; microstructure; heat input; ferrite stabilization
Available at various institutes of the ASCR
Microstructure modifications of Al-Si-coated press-hardened steel 22MnB5 by laser welding
Weld microstructure depends on the characteristics of welded materials and parameters of welding technology, especially on the heat input that determines the peak temperature and the cooling rate. ...
Influence of ball material on the resulting fatigue life of thermal sprayed HVOF coatings in dynamic impact testing
Duliškovič, J.; Daniel, Josef; Houdková, Š.
2024 - English
Dynamic impact wear, i.e. contact between two components in the presence of high cyclic local loads, is a challenging failure mode that occurs in many mechanical applications. Many previous studies have confirmed that dynamic impact testing is suitable for evaluating the contact fatigue of thermal sprayed coatings. However, the effect of the test parameters on the resulting lifetime is unclear. The aim of this study describes the effect of the ball material used in the dynamic impact test on the resulting fatigue life of the HVOF thermal sprayed coating. Three test balls made of WC/Co alloy, Si3N4 silicon nitride and 440 C steel were chosen for this study. Dynamic impaction testing was carried out on the Cr3C2-NiCr coating, which was sprayed by HVOF on a 1.2376 high-speed steel substrate. The impact lifetime was described by the number of critical impacts, i.e. the number of impacts before coating fatigue occurs. Furthermore, the depth and volume of impact craters were measured. Using scanning electron microscopy (SEM), the surface of the impacts as well as the microstructure of the coating on the cross-section in the region of the impacts were observed. Furthermore, the mechanism of crack propagation in the coating and the microstructure of the indentor were investigated.
Keywords:
dynamic impact test; HVOF; Cr3C2-NiCr; fatigue
Available at various institutes of the ASCR
Influence of ball material on the resulting fatigue life of thermal sprayed HVOF coatings in dynamic impact testing
Dynamic impact wear, i.e. contact between two components in the presence of high cyclic local loads, is a challenging failure mode that occurs in many mechanical applications. Many previous studies ...
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