Study on Eutectic Melting Behavior of Control Rod Materials in Core Disruptive Accidents of Sodium-Cooled Fast Reactors: Kinetic Study of Boron Carbide-Stainless Steel Eutectic Melting by Differential Thermal Analysis

In a postulated severe accidental condition of sodium-cooled fast reactor (SFR), eutectic melting between boron carbide (B4C) as control rod element and stainless steel (SS) as control rod cladding or related structure may take place. Thus, kinetic behavior of B4C-SS eutectic melting is one of the important phenomena to be considered when evaluating the core disruptive accidents in SFR. In this study, for the first step to obtain the fundamental information on kinetic feature of B4C-SS eutectic melting and compare the pervious findings, the thermal analysis using the pellet type samples of B4C and Type 316L SS as different experimental technique was performed up to 1773 K at different heating rates of 2.5–10 K/min. The differential thermal analysis (DTA) endothermic peaks for the B4C-SS eutectic melting appeared from 1483K to 1534K and systematically shifted to higher temperatures when increasing heating rate. Based on this kinetic feature, apparent activation energy and pre-exponential factor for the B4C-SS eutectic melting were determined by Kissinger method. It was found that the kinetic parameters obtained by thermal analysis were comparable to the literature values of thinning experiment at high temperatures. In addition, the microstructure and element distribution formed in the interdiffusion layer composed of the B4C / SS system were analyzed by the electron probe microanalyzer (EPMA), which can provide key validation data on elemental interdiffusion behavior in the early stage of the eutectic melting.

Kinetic analyses as a tool to examine physiological exercise responses in a large sample of patients with COPD

Kinetic features such as oxygen uptake (V̇o2) mean response time (MRT), and gains of V̇o2, carbon dioxide output (V̇co2), and minute ventilation (V̇e) can describe physiological exercise responses during a constant work rate test of patients with chronic obstructive pulmonary disease (COPD). This study aimed to establish simple guidelines that can identify COPD patients for whom kinetic analyses are (un)likely to be reliable and examined whether slow V̇o2 responses and gains of V̇o2, V̇co2, and V̇e are associated with ventilatory, cardiovascular, and/or physical impairments. Kinetic features were examined for 265 COPD patients [forced expiratory volume in 1 s (FEV1): 54 ± 19%predicted] who performed a constant work rate test (duration > 180 s) with breath-by-breath measurements of V̇o2, V̇co2, and V̇e. Negative/positive predictive values were used to define cutoff values of relevant clinical variables below/above which kinetic analyses are (un)likely to be reliable. Kinetic feature values were unreliable for 21% (= 56/265) of the patients and for 79% (= 19/24) of the patients with a peak work rate (WRpeak)< 45 W. Kinetic feature values were considered reliable for 94% (= 133/142) of the patients with an FEV1 > 1.3 L. For patients exhibiting reliable kinetic feature values, V̇o2 MRT was associated with ventilatory (e.g., FEV1 %predicted: P < 0.001; r = −0.35) and physical (e.g., V̇o2peak %predicted: P = 0.009; r = −0.18) impairments. Gains were mainly associated with cardiac function and ventilatory constraints, representing both response efficiency and limitation. Kinetic analyses are likely to be unreliable for patients with a WRpeak < 45 W. Whereas gains enrich analyses of physiological exercise responses, V̇o2 MRT shows potential to serve as a motivation-independent, physiological indicator of physical performance. NEW & NOTEWORTHY A constant work rate test that is standardly performed during a prerehabilitation assessment is unable to provide reliable kinetic feature values for chronic obstructive pulmonary disease (COPD) patients with a peak work rate below 45 W. For patients suffering from less severe impairments, kinetic analyses are a powerful tool to examine physiological exercise responses. Especially oxygen uptake mean response time can serve as a motivation-independent, physiological indicator of physical performance in patients with COPD.

Box-Jenkins Transfer Function Modelling for Reliable Determination of VO2 Kinetics in Patients with COPD

Oxygen uptake (VO2) kinetics provide information about the ability to respond to the increased physical load during a constant work rate test (CWRT). Box-Jenkins transfer function (BJ-TF) models can extract kinetic features from the phase II VO2 response during a CWRT, without being affected by unwanted noise contributions (e.g., phase I contribution or measurement noise). CWRT data of 18 COPD patients were used to compare model fits and kinetic feature values between BJ-TF models and three typically applied exponential modelling methods. Autocorrelation tests and normalised root-mean-squared error values (BJ-TF: 2.8 ± 1.3%; exponential methods A, B and C: 10.5 ± 5.8%, 11.3 ± 5.2% and 12.1 ± 7.0%; p < 0.05) showed that BJ-TF models, in contrast to exponential models, could account for the most important noise contributions. This led to more reliable kinetic feature values compared to methods A and B (e.g., mean response time (MRT), BJ-TF: 74 ± 20 s; methods A-B: 100 ± 56 s–88 ± 52 s; p < 0.05). Only exponential modelling method C provided kinetic feature values comparable to BJ-TF features values (e.g., MRT: 75 ± 20 s). Based on theoretical considerations, we recommend using BJ-TF models, rather than exponential models, for reliable determinations of VO2 kinetics.

Bioequivalence metrics for absorption rates: linearity, specificity, sensitivity

Aims:In order to ensure the therapeutic equivalence of generic products, it would be important to contrast measures additional to Cmax in order to assess differences in absorption rates. Our aim was to compare partial AUC (PAUC), Swing, and PTF to Cmax in terms of sensitivity, specificity and linearity under identical kinetic conditions. Methods:Single-dose and multiple-dose concentration curves were generated assuming one-compartment models. Kinetic sensitivity curves were obtained by gradually changing the absorption rate constant and keeping all other parameters fixed. Results:A metric should reflect specifically the investigated kinetic feature (e.g., the rate of absorption), be linearly related to it, and should exhibit high kinetic sensitivity. Cmax is related nonlinearly to the rate of absorption, is nonspecific to it (reflects also the extent of absorption as well as the rates of disposition processes), lacks kinetic sensitivity even following a single administration. Compared to Cmax, PAUC was always more sensitive under every investigated condition. Swing and PTF showed high kinetic sensitivity but, in contrast to PAUC, they could be evaluated only in multiple-dose studies. Conclusion:Under identical conditions, different metrics provide widely differing point estimates. Differences in kinetic sensitivity among bioequivalence metrics should be accounted for when results of different metrics are compared.

Development of axisymmetric lattice Boltzmann flux solver for complex multiphase flows

This paper presents an axisymmetric lattice Boltzmann flux solver (LBFS) for simulating axisymmetric multiphase flows. In the solver, the two-dimensional (2D) multiphase LBFS is applied to reconstruct macroscopic fluxes excluding axisymmetric effects. Source terms accounting for axisymmetric effects are introduced directly into the governing equations. As compared to conventional axisymmetric multiphase lattice Boltzmann (LB) method, the present solver has the kinetic feature for flux evaluation and avoids complex derivations of external forcing terms. In addition, the present solver also saves considerable computational efforts in comparison with three-dimensional (3D) computations. The capability of the proposed solver in simulating complex multiphase flows is demonstrated by studying single bubble rising in a circular tube. The obtained results compare well with the published data.

Distinct kinetics of molecular gelation in a confined space and its relation to the structure and property of thin gel films

Distinct kinetic feature of the molecular gelation in a confined or unconfined regime, and its relationship with the tailored fiber network structure and mechanical properties.

Lumping Kinetics of Asphaltene Hydrocracking over NiMo/γ-Al2O3

Catalytic hydrocracking of asphaltene over Ni-Mo/γ-Al2O3 was conducted in a microbatch reactor at 693 K. A kinetic model with four lumps (asphaltene, liquid, gas and coke) containing five reaction paths was developed. The fitting of experimental data validated the suggested model and determined the rate constant of each individual reactions, to give the insight to the kinetic feature of asphaltene catalytic hydrocracking

An Innovative Calculation Method of Trajectories of Rockfall

Rockfall is a frequent engineering disaster confronted in the capital construction engineering. The key for preventing rock fall is the evaluation of the rockfall trajectory. After extensive analysis, an innovative calculation method of rockfall trajectory, called segmented cycling algorithm, has been proposed in the paper. According to the contact relationship between the rolling stones and the slope surface, the movement divided into three sections which include the jumping phase, the rolling (sliding) phase and collision phase, the formulae to calculate the velocity of different phases of motion are proposed respectively by segmented cycling algorithm. A similar model, based on a rock slope in Chongqing-Wanzhou highway, is established to verify the capability and validity of the presented algorithm. Compared with existing algorithm, the new algorithm is simple and clear, easy to use and so on. The algorithm meets the law of the movement of rockfall and can be used to forecast the kinetic feature of rockfall. It is also used as the basis for rockfall disaster prevention.