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[en] Ultrasound techniques are capable of monitoring changes in the time-of-flight as a material is exposed to different thermal environments. The focus of the present study is to identify the phase of a material via ultrasound compression wave measurements in a through transmission experimental setup as the material is heated from a solid to a liquid and then allowed to re-solidify. The present work seeks to expand upon the authors’ previous research, which proved this through transmission phase monitoring technique was possible, by considering different experimental geometries. The relationship between geometry, the measured speed of sound, and the temperature profile is presented. The use of different volumes helps in establishing a baseline understanding of which aspects of the experiment are geometry dependent and which are independent. The present study also investigates the relationship between the heating rate observed in the experiment and the measured speed of sound. Lastly, the trends identified between the experimental geometry, heat rate and ultrasound wave speed measurement assist in providing a baseline understanding of the applicability of this technique to various industries, including the polymer industry and the oil industry.
[en] NSSS of TR-1 000 PB is a 1000 MW (e) plant with gas-cooled (C02) heavy water reactor the main equipment of which is contained within the vessel of restressed reinforced concrete. In project of TR-1000 PB NSSS the principle of inherent and passive safety is used as much as possible and the version is given how to localize the molten fuel in the special catcher within the prestressed reinforced concrete vessel with long-term passive heat removal
[en] The methods of optically stimulated luminescence (OSL) measurements used until recently, used optical stimulation with a constant energy and a constant or linearly increased flux of stimulation photons. During such a stimulation the ratio of probabilities of the optical release of electrons from different traps is constant and it is hard to separate the signals of different origins. It was shown recently that advantageous changes of the probability ratio during the OSL experiments, and more information about traps can be obtained by optical stimulation with the increasing stimulation energy. This method, however, needs a strong tuneable light source that supplies a stable flux of photons and because of that it cannot find a wide application. Inducing the appropriate changes of the probabilities of the optical release of electrons from traps by increasing the sample temperature during the optical stimulation with a constant stimulation band do not face such obstacles. Such a stimulation can be realised by means of the standard OSL readers after a slight modification and offers the possibility for direct estimation of optical trap depth. The simulations of the OSL process during linear heating show that the experimental parameters such as the heating rate, the stimulation light intensity and the stimulation energy strongly affect the shape of the OSL curve and can be the very useful tools for the OSL process regulation. By this kind of stimulation one can reach very deep traps that are not detectable by thermoluminescence measurements below 500 °C. The resolution of the OSL signal originating from different traps is remarkable.
[en] In an attempt to ensure more consistent casting results and remove some schedule variance associated with casting, an improved casting furnace concept has been developed. The improved furnace uses the existing arc melter hardware and glovebox utilities. The furnace concept was designed around physical and operational requirements such as; a charge sized of less than 30 grams, high heating rates and minimal additional footprint. The conceptual model is shown in the report as well as a summary of how the requirements were met.
[en] We report a spurious thermoluminescence (TL) present in three types of calcite powders which also show regenerated TL (RTL). The amount of RTL was found on storage time and on the heating rate used during TL readout. Different heating rates during TL readout caused profound changes in the measured TL spectra in the range 400-650 nm. These changes can be explained by manganese ions moving into and out of clusters during the heating process. (author)
[en] For the first time, the growth of ZnO nanobelts was monitored in situ using x-ray diffraction. The growth was carried out by heating metallic zinc powder in air at temperatures ranging from 368 to 568 deg. C. The morphology depends on both the growth temperature and the rate of heating to that temperature. A morphology diagram for the synthesized products was generated after systematic study of the experimental parameters. Higher temperatures and faster heating rates favor one-dimensional growth. Faster growth was observed for samples with higher growth temperatures, lower heating rates, and one-dimensional growth. These results give insight into the mechanism for the growth of ZnO nanobelts by metal oxidation.
[en] The kinetic parameters of the two high-temperature glow peaks (peaks III and IV) in a fluorite obtained in a region of Nigeria has been determined in detail by using Chen's peak shape and initial rise methods. The values of these parameters calculated with these two methods are comparable. The orders of kinetics of the two peaks are found to be different from either the first or the second. The b values obtained ranged from 1.023 to 1.134 for peak III and from 1.156 to 1.223 for peak IV. The E values ranged from 0.777 to 1.068 eV for peak III and from 1.328 to 1.428 eV for peak IV. The present values of kinetic parameters are compared with those from past studies on fluorite and the observed variations discussed. The electron lifetime in each of these traps, a parameter to dosimetry, was also determined. The value of lifetime obtained for peak III suggests that the peak may be a complex one, when it is viewed in relation to the thermoluminescence enhancement of this peak with storage time that has been reported. The two peaks were tested for quasi-equilibrium (QE) approximation because the general order model used assumed QE condition; it was found that for all the heating rates used peak IV was emitted under QE condition, while peak III was emitted under QE condition only at the smallest heating rates of 7 and 10 degree sign C/s used in this work
[en] We propose a new scheme to estimate the heating rate of trapped ions in thermal states. By applying a controlled-U gate between the internal and the motional states of one of the trapped ions, we could obtain the mean phonon number from the population of the internal state of the ion. The imperfection due to fluctuations of the relevant parameters in real experiments is considered and we analyze the experimental feasibility of our scheme with sophisticated ion trap techniques. (general)
[en] Metal injection moulding (MIM) is a metalworking technology for producing a small and complex product as well as high efficiency. In this process, the sintering parameter is an important process that must be controlled especially the sintering atmosphere to optimise the product. In the previous study, the sintering process was conducted by using a vacuum atmosphere that resulted in the formation of porosity as a major problem. This study was aimed to understand the influence of argon atmosphere in the sintering process with different temperature in order to improve the relative density of 17-4 PH Stainless Steel. The 17-4 PH Stainless Steel feedstock injected to the mould using injection moulding machine. After injection, the solvent debinding process was carried out at 50 oC with hexane solution for 1.5 h. Thermal debinding was performed at 510 oC using a vacuum furnace with heating rate and holding time were 1 °C min−1 and 60 min, respectively. Afterwards, the resulting sample was heated at the various sintering temperature of 1320 °C, 1340 °C, 1360 °C, and 1380 °C with 5 °C min−1 heating rate and 90 min holding time in an argon atmosphere with flowing rate of 1 litre min−1. These study revealed an argon atmosphere sintering process influenced the content reduction of porosity due to increasing relative density. According to these results, the optimum sintering temperature by using an argon atmosphere was achieved at 1360 oC. (paper)
[en] Studies regarding CHF enhancement using nanofluid have been conducted by many researchers. Few of them have been conducted under flow boiling condition. In our previous work, we could not find the concentration effect of nanofluid on the flow boiling CHF. We concluded that the effect of nanofluid on the CHF may already be saturated at low concentration because of long boiling time (more than 15 minutes), and there may be a minimum deposition layer of nanoparticles to enhance the flow boiling CHF. In the present study, we conducted flow boiling CHF experiments using nanofluid under different heating rate to examine the minimum deposition layer. After the flow boiling CHF experiments, the inner surfaces of the test section tube were explored by FESEM