Brno University of Technology

About: Brno University of Technology is a education organization based out in Brno, Czechia. It is known for research contribution in the topics: Fracture mechanics & Filter (video). The organization has 6339 authors who have published 15226 publications receiving 194088 citations. The organization is also known as: Vysoké učení technické v Brně & BUT.

Comparison of low stress creep properties of ferritic and austenitic creep resistant steels

Abstract: Creep tests at stresses below 30 MPa and temperatures from 923 to 1073 K were conducted on an austenitic AISI-316H creep resistant steel The helicoid spring specimen technique was used with the average test duration of ∼2000 h The results were compared to the results obtained on modified 9% Cr ferritic P-91 type creep resistant steel by the same experimental technique under comparable conditions The shapes of creep curves for both steels are rather similar, with a deep decrease in creep rate during primary stage followed by a secondary stage with constant strain rate Viscous creep (ie creep having the stress exponent close to one) was demonstrated in both steels under the loading conditions described above The secondary creep rate for AISI-316H is about two times lower than that of P-91 under the same testing conditions The difference can be easily explained by the difference in mean grain size of both materials, supposing that the diffusional creep is the prevailing deformation mechanism Unfortunately, it is not possible to identify creep mechanism clearly due to no possibility to obtain specimens with different grain size and the same microstructure Further, the creep mechanism identification is complicated by the fact, that the measured apparent activation energy is almost the same for both materials This result is in contradiction to the diffusion data published in the literature, where a considerably lower value of activation enthalpy in γ -phase than in α -phase have been reported for both volume and grain boundary diffusion

Allpass filter employing one grounded capacitor and one active element

Abstract: A simple first-order current-mode allpass filter employing a Z-copy current inverter transconductance amplifier (ZC-CITA) and one grounded capacitor is presented. The natural frequency of the filter can be simply controlled by the transconductance of the CITA. On-chip experiments confirm the design assumptions.

Employment of Electrochemical Techniques for Metallothionein Determination in Tumor Cell Lines and Patients with a Tumor Disease

Abstract: In the present paper we employed adsorptive transfer stripping technique coupled with chronopotentiometric stripping analysis for determination of metallothionein (MT) in tumor cell lines and differential pulse voltammetry Brdicka reaction for determination of MT in blood serum of patients with head and neck cancer or retinoblastoma, and of rats treated with cisplatin with respect to discuss the role of MT in formation of resistance on treatment with heavy metal based cytostatics. The cisplatin or carboplatin sensitive and resistant neuroblastoma cell lines were derived from the maternal cell line isolated from the bone metastasis of patients with neuroblastoma. Based on the results obtained it can be concluded that level of MT increases with higher dose of platinum based cytostatics at cells. Further we focused on determination of MT in blood serum of rats treated with cisplatin (two doses 1.05 mg and/or 2.1 mg of cisplatin per kg). The highest level of MT at rats treated with 1.05 mg cisplatin was determined after four hours as 4.9 mol/L. In the case of the second experimental group the maximum was reached even after two hours of the treatment as 4.8 mol/L. In addition we were interested in the effect of cisplatin or carboplatin treatment of patients with a tumor disease. At patients with tumor in head and neck area treated with cisplatin we observed that the level of MT was going higher due to administration of the drug. This phenomenon was observed at all patients. However at patients with retinoblastoma treated with carboplatin we observed various phenomena including decreasing, increasing or no changes in MT level. Progression of MT levels was therefore individual and probably depended on tumor resistance to carboplatin.

Enhanced-Gain Dielectric Resonator Antenna Based on the Combination of Higher-Order Modes

Abstract: The combination of two higher-order hybrid electromagnetic modes ( ${{\rm HEM}_{133}}$ and ${{\rm HEM}_{123}}$ ) in a simple cylindrical dielectric resonator is exploited in the presented letter to enhance antenna gain. Both modes were excited by the same feeding aperture in the ground plane of a microstrip line. A linearly polarized, broadside radiation pattern with maximum realized gain of about 11.6 dBi was successfully obtained. The antenna was designed for the ISM band with central frequency 5.8 GHz and relative bandwidth of at least 2.6%. For fabrication, we used a layered Arlon AR600 substrate of relative permittivity 6.15. Experimental results showed reasonable agreement with simulations and validated the new concept of the high-gain dielectric resonator antenna.