The Influence of Thermal Dilution on the Microstructure Evolution of Some Combustion-Synthesized Refractory Ceramic Composites

Modeling the self-sustained high-temperature synthesis (SHS) reaction via thermal dilution and transformation of the reaction heterogeneous media into a moderate exothermic one has unlimited potential for designing inorganic powders of a certain morphology beneficial for advanced consolidation. Thermal/inert dilution of the high-exothermic mixtures leads to the fluent decrease of both the combustion temperature and velocity, thus allowing to tailor the thermal regime of the combustion process, therewith contributing to high yield of reaction and governing the microstructural features of the combustion products. In the current review, we shed on light on the possibilities of this effective strategy to control the thermal behavior of the SHS process for the preparation of applicable powder precursors for the subsequent successful sintering. Since the SHS process of some refractory ceramics (MoSi2, TiB2, TiC, etc.) involves a relatively violent reaction rate and high combustion temperature, achieving a high level of microstructure control in these systems is often challenging. The challenge was tackled with a thermal dilution approach, attaining considerable enhancement in the homogeneity among phases with an increase of diluent content along with microstructure refinement.

Impact of EGR on the surface functional groups of diesel engine particles based on NEXAFS

The thermal, dilution and chemical effects of EGR result in relatively significant changes in the formation environment, in the physical and chemical reactions of particles and in the functional groups of the matter that constitutes the particles.

Estimation of Errors in Determining Intrathoracic Blood Volume Using the Single Transpulmonary Thermal Dilution Technique in Hypovolemic Shock

Background The transpulmonary thermal dilution technique has been widely adopted for monitoring cardiac preload and extravascular lung water in critically ill patients. This method assumes intrathoracic blood volume (ITBV) to be a fixed proportion of global end-diastolic volume (GEDV). This study determines the relation between GEDV and ITBV under normovolemic and hypovolemic conditions and quantifies the errors in estimating ITBV. Methods Nineteen pigs allocated to control (n = 9) and shock (n = 10) groups were studied. Shock was maintained for 60 min followed by volume resuscitation. The dual dye-thermal dilution technique was used to measure GEDV and ITBV (ITBVm) at baseline (time 0), shock phase (30 and 90 min), and after resuscitation (150 min). The regression equations estimated from paired GEDV and ITBVm measurements under normovolemic and hypovolemic conditions were used to estimate ITBV from the corresponding GEDV, and the estimation errors were quantified. A more simplified equation, used in a commercially available clinical monitor (ITBV = 1.25 x GEDV), was then used to estimate ITBV. Results The regression equation in the control group was ITBVm = 1.21 x GEDV + 99 (r = 0.89, P < 0.0001) and in the shock group at 30 and 90 min was ITBVm = 1.45 x GEDV + 0.6 (r = 0.95, P < 0.0001). The 95% confidence interval for the y-intercept was relatively wide, ranging from 31 to 168 and -47 to 49, respectively, for the two equations. The equation estimated in the control group led to overestimation of ITBV and a significant (P < 0.05) increase in errors in the shock group at 30 and 90 min. Errors in estimating ITBV using the simplified commercial algorithm were less than 15% under normovolemic and hypovolemic conditions. Conclusions The linear relation between GEDV and ITBV is maintained in hypovolemic shock. Even though the relation between GEDV and ITBV is influenced by circulatory volume and cardiac output, the mean errors in predicting ITBV were small and within clinically tolerable limits.