The paper presents and compares the results of theoretical and experimental research in the field of cracking of model material (commercial plasticine) and C45 steel in hot forming conditions. The aim of the research was to determine the limit values of the Cockroft-Latham integral for both materials. The presented research methodology includes experimental tests (tensile tests) and numerical simulations carried out in the DEFORM-3D program. For laboratory tests, axially symmetric samples made of C45 steel and model material were used. On the basis of the obtained experimental and numerical results, a comparative analysis of both materials was carried out.
Łukasz Marciniak, Anna Wójcik-Gargula, Agnieszka Kulińska, Jakub Bielecki and Urszula Wiącek
This paper presents a set of diagnostics dedicated to PF-24 - new medium size - plasma focus (PF) device built and operated at the Institute of Nuclear Physics Polish Academy of Sciences (IFJ PAN). The PF-24 can operate at energy level up to 93 kJ and charging voltage up to 40 kV. Each condenser is connected with a specially designed spark gap with a very small jitter, which ensures a high effi ciency and a low current rise time. The working parameters of PF-24 generator make it a suitable tool for testing new detection systems to be used in fusion research. Four types of such detection systems are presented in this article: three diagnostic systems used to measure electric quantities (Rogowski coil, magnetic probe, capacitance probe), neutron counter based on beryllium activation, fast neutron pinhole camera based on small-area BCF-12 plastic scintillation detectors and high-speed four-frame soft X-ray camera with microchannel plate.
Stanisław Łapiński, Marcin W. Lis, Anika Wójcik, Łukasz Migdał and Iwona Guja
The aim of the study was to assess the extent of fur chewing problems on chinchilla farms. The research was based on a 20-question survey addressed to breeders. A total of 47 anonymous questionnaires were answered. Results showed that the problem of fur chewing was found in as many as 85% of the farms but the proportion of affected animals was usually low (mean±SE: 3.5±0.55%). To determine the relationship between herd size and the extent of the problem, the Pearson’s correlation coefficient was calculated to be r = -0.315 (P≤0.05), possibly indicating the problem to be more severe on smaller farms. No correlation was found between fur chewing and the type of fodder (pellets from different producers), temperature, humidity, type of cage equipment or frequency of dust baths. Moreover, the level of fur-biting animals kept on a deep-litter floor was estimated at 1.7% while the level of those kept on a wire floor and in a mixed system was 2.8-times higher (P≤0.05). The fact that 37.5% of the respondents perceived the predisposition to fur chewing to be hereditary was an important observation suggesting a direction for further research. A considerable proportion of those surveyed (37.5%) also pointed to a greater excitability among fur chewers. To sum up, results of the present study revealed that keeping animals on litter reduces the incidence of fur chewing. Breeders’ observations also suggest that fur biting may be determined genetically and/or connected with impulsive-compulsive disorders; however, more detailed studies are necessary to confirm these hypotheses.
Krzysztof Olszewski, Grzegorz Borsuk, Piotr Dziechciarz, Łukasz Wójcik and Jerzy Paleolog
Temperatures of worker- and drone-brood rearing in various hive locations were compared in both colonies kept on small-cell combs (4.90 mm) (SMC) and standard-cell combs (5.50 mm) (STC) in two seasons. Temperatures close to the worker-brood comb placed near the rightmost storage-comb were lower than those near the worker brood in the nest centre but equal to those near the outskirt drone-brood comb (34.37-35.24°C) regardless of the month and the comb-cell size. Temperatures of the brood rearing in the SMC did not differ from those in the STC, independently on the location (center-periphery) and the brood type (drone-worker). Occasionally, they were even higher in the STC near the peripheral drone-brood comb and in the nest centre. We concluded that the drones which are involved in colony reproduction could affect its thermoregulation. The peripheral drone brood can be heated just as well as the worker brood, if the colony is strong enough and has the proper drone-worker ratio. Therefore, it is doubtful whether a higher temperature near the worker brood in the SMC limit the development of the V. destructor population. A lower temperature may not be a factor in encouraging V. destructor females to prefer trap-drone-combs for reproduction in the SMC. Strong field colonies may be especially prone to such behaviour. Therefore, temperature cannot be considered a mechanism of effective Varroa control in SMC.