Labelling experiments in red deer provide a general model for early bone growth dynamics in ruminants

Growth rates importantly determine developmental time and are, therefore, a key variable of a species' life history. A widely used method to reconstruct growth rates and to estimate age at death in extant and particularly in fossil vertebrates is the analysis of bone tissue apposition rates. Lines of arrested growth (LAGs) are of special interest here, as they indicate a halt in bone growth. However, although of great importance, the time intervals between, and particularly the reason of growth arrests remains unknown. Therefore, experiments are increasingly called for to calibrate growth rates with tissue types and life history events, and to provide reliable measurements of the time involved in the formation of LAGs. Based on in vivo bone labelling, we calibrated periods of bone tissue apposition, growth arrest, drift and resorption over the period from birth to post-weaning in a large mammal, the red deer. We found that bone growth rates tightly matched the daily weight gain curve, i.e. decreased with age, with two discrete periods of growth rate disruption that coincided with the life history events birth and weaning, that were visually recognisable in bone tissue as either partial LAGs or annuli. Our study identified for the first time in a large mammal a general pattern for juvenile bone growth rates, including periods of growth arrest. The tight correlation between daily weight gain and bone tissue apposition suggests that the red deer bone growth model is valid for ruminants in general where the daily weight gain curve is comparable.

Asymmetric quasi impedance source buck-boost converter

An impedance source buck-boost converter (BBC) prototype for renewable energy (RE) application in the transportation industry is proposed. Its functions include stabilizing the variable output voltage of the RE sources such as fuel cells and photovoltaic cells. The converter utilized a topology of DC-DC quasi-impedance source converters (q-ZSCs) to achieve the gain curve of the BBC. With BBC gain curve, the converter earned advantages over the two other classes of non-isolated DC-DC q-ZSCs. These advantages include ecient buck-boost capability at the ecient duty ratio range of 0:35-0:65 and continuous and non-zero gain at the ecient duty ratio range. The converter's q-ZSC topology implies using two capacitors and two inductors. These two capacitors and inductors formed two separate LC filters that provides second order filtering compared to the first order filtering in BBC. Its other advantages over the traditional BBC include elim-ination of dead and overlap-time, simple contol and permitting higher switching frequency operation. The converter is capable of utilizing high switching frequency and asymmetric components to achieve BBC gain by using smaller components to reduce cost, weight and size. Its simulation response and that of a correspond-ing BBC for some given specifications were compared, presented and analyzed. An experimental scaled-down prototype was also developed to confirm its opera-tion. Analysis of the converters responses comfirmed the prototype's second order filtering as against the first order filtering in traditional BBC.

A Comparison of the Transfer Functions and Flow Fields of Flames With Increasing Swirl Number

The frequency response of premixed swirled flames is investigated by comparing their Transfer Function (FTF) between velocity and heat release rate fluctuations. The equivalence ratio and flow velocity are kept constant and four different swirling injectors are tested with increasing swirl numbers. The first injector features a vanishing low swirl number S = 0.20 and produces a flame anchored by the recirculating flow in the wake of a central bluff body. The three other swirling injectors produce highly swirled flows (S > 0.6) leading to a much larger internal recirculation region, which size increases with the swirl level. When operating the burner at S = 0.20, the FTF gain curve smoothly increases to reach a maximum and then smoothly decreases towards zero. For the highly swirled flames (S > 0.6), the FTF gain curve shows a succession of valleys and peaks attributed to interferences between axial and azimuthal velocity fluctuations at the injector outlet. The FTF phase-lag curves from the vanishing low and highly swirled flames are the same at low frequencies despite their large differences in flame length and flame aspect ratio. Deviations between the FTF phase lag curves of the different swirled flames start above the frequency corresponding to the first valley in the FTF gain of the highly swirled flames. Phase averaged images of the axial flow fields and of the flame chemiluminescence are used to interpret these features. At forcing frequencies corresponding to peak FTF gain values, the cold flow response of all flames investigated is dominated by large coherent vortical structures shed from the injector lip. At forcing frequencies corresponding to a valley in the FTF gain curve of the highly swirled flames, the formation of large coherent structures is strongly hindered in the cold flow response. These observations contrast with previous interpretations of the mechanisms associated to the low FTF response of swirled flames. It is finally found that for flames stabilized with a large swirl number, heat release rate fluctuations result both from large flame luminosity oscillations and large flame volume oscillations. For conditions leading to a small FTF gain value, both the flame luminosity and flame volume fluctuations are suppressed confirming the absence of strong perturbations within the flow at these frequencies. The experiments made in this work reveal a purely hydrodynamic mechanism at the origin of the low response of swirling flames at certain specific frequencies.

Energy gain of a thin DT shell target in inertial confinement fusion

Estimation of maximum possible energy gain for a given energy of driver has always become a key point in inertial confinement fusion. It has direct impact on the cost of produced electricity. Here, we employ a hydrodynamics model to assess energy gain in the case of a symmetrical hydrodynamics implosion where a narrow fuel shell consisting of deuterium–tritium (DT), can experience an isentropic compression in a self-similar regime. Introducing a set of six state parameters {H hs , T hs , U imp , αc, ξhs and μhs}, the final fuel state close to ignition is fully described. It enables us to calculate energy gain curves for specific set of these state variables. The envelope of the energy gain family curves provide a limiting gain curve [Formula: see text]. Next, we took into account the inertial of cold surrounding fuel on the ignition process. It changes the limiting gain curve slope to 0.41. Finally, the analytical model results assessed and validated using numerical simulation code.

Research on LLC DC-DC Transformer

Regulated DC-DC converter and unregulated DC-DC transformer is the basic types of DC-DC converter. Now the research is focusing on the regulated form named regulated LLC resonant DC-DC converter. Unregulated form of LLC resonant DC-DC converter named LLC resonant DC-DC transformer is studied in this paper in order to increase the practical topology of soft-switching and high-efficiency DC-DC transformer. Design method is proposed by the gain curve analyze of LLC resonant DC-DC transformer, and load characteristic of gain and efficiency of the DC-DC transformer is analyzed specializing for optimal design. A LLC resonant DC-DC transformer prototype is designed and implemented. Experimental results verify the correctness and validity of the design method and the load characteristic analysis.