Demonstration of reduced neoclassical energy transport in Wendelstein 7-X

Research on magnetic confinement of high-temperature plasmas has the ultimate goal of harnessing nuclear fusion for the production of electricity. Although the tokamak1 is the leading toroidal magnetic-confinement concept, it is not without shortcomings and the fusion community has therefore also pursued alternative concepts such as the stellarator. Unlike axisymmetric tokamaks, stellarators possess a three-dimensional (3D) magnetic field geometry. The availability of this additional dimension opens up an extensive configuration space for computational optimization of both the field geometry itself and the current-carrying coils that produce it. Such an optimization was undertaken in designing Wendelstein 7-X (W7-X)2, a large helical-axis advanced stellarator (HELIAS), which began operation in 2015 at Greifswald, Germany. A major drawback of 3D magnetic field geometry, however, is that it introduces a strong temperature dependence into the stellarator’s non-turbulent ‘neoclassical’ energy transport. Indeed, such energy losses will become prohibitive in high-temperature reactor plasmas unless a strong reduction of the geometrical factor associated with this transport can be achieved; such a reduction was therefore a principal goal of the design of W7-X. In spite of the modest heating power currently available, W7-X has already been able to achieve high-temperature plasma conditions during its 2017 and 2018 experimental campaigns, producing record values of the fusion triple product for such stellarator plasmas3,4. The triple product of plasma density, ion temperature and energy confinement time is used in fusion research as a figure of merit, as it must attain a certain threshold value before net-energy-producing operation of a reactor becomes possible1,5. Here we demonstrate that such record values provide evidence for reduced neoclassical energy transport in W7-X, as the plasma profiles that produced these results could not have been obtained in stellarators lacking a comparably high level of neoclassical optimization.

Development of Empirical Correlation of Two-Phase Pressure Drop in Moisture Separator Based on Separated Flow Model

Pressure drop across the moisture separator installed in the steam generator of a nuclear power plant affects the power generation efficiency, and so accurate pressure drop prediction is important in generator design. In this study, an empirical correlation is proposed for predicting the two-phase pressure drop through a moisture separator. To ensure the applicability of the correlation, a series of two-phase air-water experiments were performed, and the results of the present test and of the benchmark test of high-pressure steam-water were used in developing the correlation. Based on the experimental results, quality, dimensionless superficial velocity, density ratio of the working fluid, and the geometrical factor were considered to be important parameters. The two-phase pressure drop multiplier was expressed in terms of these parameters. The empirical correlation was found to predict the experimental results within a reasonable range.

Target Characterization and Scattering Power Decomposition for Full and Compact Polarimetric SAR Data

This manuscript was accepted for publication on IEEE Transactions on Geoscience and Remote Sensing.<br><br>Abstract: In radar polarimetry, incoherent target decomposition<br>techniques help extract scattering information from polarimetric<br>SAR data. This is achieved either by fitting appropriate scattering models or by optimizing the received wave intensity<br>through the diagonalization of the coherency (or covariance)<br>matrix. As such, the received wave information depends on<br>the received antenna configuration. Additionally, a polarimetric<br>descriptor that is independent of the received antenna configuration might provide additional information which is missed by the individual elements of the coherency matrix. This implies that existing target characterization techniques might neglect this information. In this regard, we suitably utilize the 2D and 3D Barakat degree of polarization which is independent of the received antenna configuration to obtain distinct polarimetric information for target characterization. In this study, we introduce new roll-invariant scattering-type parameters for both full-polarimetric (FP) and compact-polarimetric (CP) SAR data. These new parameters jointly use the information of the 2D and 3D Barakat degree of polarization and the elements of the coherency (or covariance) matrix. We use these new scattering type parameters, which provide equivalent information as the Cloude alpha for FP SAR data and the ellipticity parameter chi for CP SAR data, to characterize various targets adequately. Additionally, we appropriately utilize these new scattering-type parameters to obtain unique non-model based three-component scattering power decomposition techniques. We obtain the even-bounce, and the odd-bounce scattering powers by modulating the total polarized power by a proper geometrical factor derived using the new scattering-type parameters for FP and CP SAR data. The diffused scattering power is obtained as the depolarized fraction of the total power. Moreover, due to the nature of its formulation, the decomposition scattering powers are nonnegative and roll-invariant while the total power is conserved. The proposed method is both qualitatively and quantitatively assessed utilizing the L-band ALOS-2 and C-band Radarsat-2 FP and the associated simulated CP SAR data.

Target Characterization and Scattering Power Decomposition for Full and Compact Polarimetric SAR Data

This manuscript was accepted for publication on IEEE Transactions on Geoscience and Remote Sensing.<br><br>Abstract: In radar polarimetry, incoherent target decomposition<br>techniques help extract scattering information from polarimetric<br>SAR data. This is achieved either by fitting appropriate scattering models or by optimizing the received wave intensity<br>through the diagonalization of the coherency (or covariance)<br>matrix. As such, the received wave information depends on<br>the received antenna configuration. Additionally, a polarimetric<br>descriptor that is independent of the received antenna configuration might provide additional information which is missed by the individual elements of the coherency matrix. This implies that existing target characterization techniques might neglect this information. In this regard, we suitably utilize the 2D and 3D Barakat degree of polarization which is independent of the received antenna configuration to obtain distinct polarimetric information for target characterization. In this study, we introduce new roll-invariant scattering-type parameters for both full-polarimetric (FP) and compact-polarimetric (CP) SAR data. These new parameters jointly use the information of the 2D and 3D Barakat degree of polarization and the elements of the coherency (or covariance) matrix. We use these new scattering type parameters, which provide equivalent information as the Cloude alpha for FP SAR data and the ellipticity parameter chi for CP SAR data, to characterize various targets adequately. Additionally, we appropriately utilize these new scattering-type parameters to obtain unique non-model based three-component scattering power decomposition techniques. We obtain the even-bounce, and the odd-bounce scattering powers by modulating the total polarized power by a proper geometrical factor derived using the new scattering-type parameters for FP and CP SAR data. The diffused scattering power is obtained as the depolarized fraction of the total power. Moreover, due to the nature of its formulation, the decomposition scattering powers are nonnegative and roll-invariant while the total power is conserved. The proposed method is both qualitatively and quantitatively assessed utilizing the L-band ALOS-2 and C-band Radarsat-2 FP and the associated simulated CP SAR data.

Tools for Visualizing and Analyzing Fourier Space Sampling in Cryo-EM

A complete understanding of how an orientation distribution contributes to a cryo-EM reconstruction remains lacking. It is necessary to begin critically assessing the set of views to gain an understanding of its effect on experimental reconstructions. Toward that end, we recently suggested that the type of orientation distribution may alter resolution measures in a systematic manner. We introduced the sampling compensation factor (SCF), which incorporates how the collection geometry might change the spectral signal-to-noise ratio (SSNR), irrespective of the other experimental aspects. We show here that knowledge of the sampling restricted to spherical surfaces of sufficiently large radii in Fourier space is equivalent to knowledge of the set of projection views. Moreover, the SCF geometrical factor may be calculated from one such surface. To aid cryo-EM researchers, we developed a graphical user interface (GUI) tool that evaluates experimental orientation distributions. The GUI returns plots of projection directions, sampling constrained to the surface of a sphere, the SCF value, the fraction of the empty region of Fourier space, and a histogram of the sampling values over the points on a sphere. Finally, a fixed tilt angle may be incorporated to determine how tilting the grid during collection may improve the distribution of views and Fourier space sampling. We advocate this simple conception of sampling and the use of such tools as a complement to the distribution of views to capture the different aspects of the effect of projection directions on cryo-EM reconstructions.

Universal Relation for Life-span Energy Consumption in Living Organisms: Insights for the origin of aging

Metabolic energy consumption has long been thought to play a major role in the aging process (1). Across species, a gram of tissue on average expends about the same amount of energy during life-span (2). Energy restriction has also been shown that increases maximum life-span (3) and retards age-associated changes (4). However, there are significant exceptions to a universal energy consumption during life-span, mainly coming from the inter-class comparison (5, 6). Here we present a unique relation for life-span energy consumption, valid for ∼300 species representing all classes of living organisms, from unicellular ones to the largest mammals. The relation has an average scatter of only 0.3 dex, with 95% of the organisms having departures less than a factor of π from the relation, despite the ∼20 orders of magnitude difference in body mass, reducing any possible inter-class variation in the relation to only a geometrical factor. This result can be interpreted as supporting evidence for the existence of an approximately constant total number Nr ∼ 108 of respiration cycles per lifetime for all organisms, effectively predetermining the extension of life by the basic energetics of respiration.

Robust Optimization Scheme for Inverse Method for Crystal Plasticity Model Parametrization

A bottom-up material modeling based on a nonlocal crystal plasticity model requires information of a large set of physical and phenomenological parameters. Because of the many material parameters, it is inherently difficult to determine the nonlocal crystal plasticity parameters. Therefore, a robust method is proposed to parameterize the nonlocal crystal plasticity model of a body-centered cubic (BCC) material by combining a nanoindentation test and inverse analysis. Nanoindentation tests returned the load–displacement curve and surface imprint of the considered sample. The inverse analysis is developed based on trust-region-reflective algorithm, which is the most robust optimization algorithm for the considered non-convex problem. The discrepancy function is defined to minimize both the load–displacement curves and the surface topologies of the considered material under applying varied indentation forces obtained from numerical models and experimental output. The numerical model results based on the identified material properties show good agreement with the experimental output. Finally, a sensitivity analysis performed changing the nonlocal crystal plasticity parameters in a predefined range emphasized that the geometrical factor has the most significant influence on the load–displacement curve and surface imprint parameters.

Joint Use of Scattered and Received Wave Polarization Information for Target Characterization and Scattering Power Decomposition

This manuscript was submitted on 31 December 2019 to IEEE Transactions on Geoscience and Remote Sensing.<br><br>Abstract: Incoherent target decomposition techniques provide unique scattering information from polarimetric SAR data either by fitting appropriate scattering models or by optimizing the ``received" wave intensity through the diagonalization of the coherency (or covariance) matrix. Hence, the information provided by the ``scattered" wave might be neglected. This scattered wave information can be well utilized to gain complete polarimetric information for numerous applications. In this study, a new roll-invariant scattering-type parameter is introduced, which jointly uses the degree of polarization as the ``scattered" wave information and the elements of the covariance matrix as the ``received" wave information from both full-polarimetric (FP) and compact-polarimetric (CP) SAR data. This scattering-type parameter, which is comparable to that of the Cloude $\alpha$ for FP SAR data and the ellipticity parameter $\chi$ for CP SAR data, can be well utilized to characterize various targets. Furthermore, this new scattering-type parameter is adequately utilized to obtain a non-model based three-component scattering power decomposition technique. The double-bounce and the odd-bounce scattering powers are obtained by modulating the total polarized power by a proper geometrical factor easily derived using the new scattering-type parameter for both FP and CP SAR data. Moreover, due to its natural and direct formulation, the decomposition scattering powers are non-negative and roll-invariant while the total power is conserved. The proposed method is qualitatively and quantitatively assessed utilizing the L-band ALOS-2 and C-band Radarsat-2 FP and the associated simulated CP SAR data.

The New Method Using Shannon Entropy to Decide the Power Exponents on JMAK Equation †

The JMAK (Johnson–Mehl–Avrami–Kolmogorov) equation is exponential equation inserted power-law behavior on the parameter, and is widely utilized to describe the relaxation process, the nucleation process, the deformation of materials and so on. Theoretically the power exponent is occasionally associated with the geometrical factor of the nucleus, which gives the integral power exponent. However, non-integral power exponents occasionally appear and they are sometimes considered as phenomenological in the experiment. On the other hand, the power exponent decides the distribution of step time when the equation is considered as the superposition of the step function. This work intends to extend the interpretation of the power exponent by the new method associating Shannon entropy of distribution of step time with the method of Lagrange multiplier in which cumulants or moments obtained from the distribution function are preserved. This method intends to decide the distribution of step time through the power exponent, in which certain statistical values are fixed. The Shannon entropy to which the second cumulant is introduced gives fractional power exponents that reveal the symmetrical distribution function that can be compared with the experimental results. Various power exponents in which another statistical value is fixed are discussed with physical interpretation. This work gives new insight into the JMAK function and the method of Shannon entropy in general.

ENERGY EFFICIENT SOLUTIONS FOR SMALL CAPACITY ELECTRIC ARC FURNACES OF A FOUNDRY CLASS

The low specific power of the transformer in combination with the increased heat losses due to the geometrical factor and the unstable operation with long downtimes are predetermined by low technical and economic indicators of production, in comparison with the EAF of the "big" metallurgy. An urgent task is to search for low-cost methods to increase the energy efficiency of furnaces of this class by simulating the thermal work of the elements of the working space. Numerical simulation of heat transfer in the working space of foundry class AC EAF with a capacity of 3 tons has shown that with a duration of furnace downtime of 18–20 hours or more, replacing 40% of the walls lining and 16-20% of the roof lining by water cooled elements with a volumetric structure accumulating the skull, with using of “deep" bath with a reduced by 14–15% diameter of the radiating surface allows, at a given melting mass, to reach the energy consumption level of the furnace with a fully refractory lining and lower with a significant saving of refractories. Preloading scrap into the furnace in downtime increases energy efficiency, all other things being equal.