APPLICATION OF TWO-BIT DITHERED DISCRETE FOURIER BASIS FUNCTIONS IN ELECTRICITY MEASUREMENT

Paper defines an algorithm for generating two - bit dithered discrete Fourier basis functions (2BDDFBF) used in a Stochastic Digital Discret Fourier Transformation (SDDFT) processor. Based on the theoretical criterion of marginal precision, and norm and orthogonality, the orthonormality of DFT with 32 harmonics was confirmed by simulation and experimentally. The experiment was detailed and comprehensive, both for standardization and for both types of orthogonality. It was performed in 236800000 points in each of the three variants of orthonormalization. The matching of theoretical and experimental precision is very acceptable and it can be said with great reliability that the proposed algorithm for generating DDFBF is correct. 2BDDFBF play key role in electricity measurement what is emphasized in the paper. .

Experimental validation of universal plasma blob formation mechanism

Abstract Anomalous plasma transport in the boundary region of a tokamak plasma is commonly associated with the formation and evolution of coherent density structures known as blobs. Recently, a theory for a universal mechanism of plasma blob formation has been put forward. It is based on a breaking process of a radially elongated streamer due to poloidal and radial velocity shears. The theory is well supported by two-dimensional and three-dimensional numerical simulation results but lacks experimental validation. In this work, we report the first ever experimental validation of this universal criterion by testing it against NSTX data on blobs obtained using the gas-puff imaging (GPI) diagnostic. It is found that the criterion is widely satisfied in most L-mode discharges and may explain the significantly larger number of blob events. We also validate the theoretical criterion against ADITYA Langmuir probe data taken in the scrape-off layer region.

Vibration response of defect-ball-defect of rolling bearing with compound defects on both inner and outer races

Aiming at the problem that the existing compound defects model of rolling bearings under radial load is difficult to reflect the actual contact between rolling elements and defects. A new model is proposed to accurately reflect the simultaneous or sequential contact between inner and outer race defects and rolling elements. Considering the coupled excitation between shaft and bearing and pedestal, time-varying displacement excitation, and radial clearance, a four degree-of-freedom vibration model of rolling bearing with compound faults on both inner and outer races is built. The vibration equations are calculated by the method of numerical way, and the model is verified by experiment. The vibration response characteristics of the Defect-Ball-Defect model are studied, which renders a theoretical criterion for bearing fault diagnosis.

Chemical Potential-Based Modeling of Shale Gas Transport

Shale gas plays an increasingly important role in the current energy industry. Modeling of gas flow in shale media has become a crucial and useful tool to estimate shale gas production accurately. The second law of thermodynamics provides a theoretical criterion to justify any promising model, but it has been never fully considered in the existing models of shale gas. In this paper, a new mathematical model of gas flow in shale formations is proposed, which uses gas density instead of pressure as the primary variable. A distinctive feature of the model is to employ chemical potential gradient rather than pressure gradient as the primary driving force. This allows to prove that the proposed model obeys an energy dissipation law, and thus, the second law of thermodynamics is satisfied. Moreover, on the basis of energy factorization approach for the Helmholtz free energy density, an efficient, linear, energy stable semi-implicit numerical scheme is proposed for the proposed model. Numerical experiments are also performed to validate the model and numerical method.

Numerical simulation of shock wave/tip leakage vortex interaction for a transonic axial fan rotor

This paper presents the steady numerical investigation on SW/TLV interaction with SST turbulence model at two characteristic operating conditions for a transonic fan rotor, NASA Rotor 67. The main purpose of the present work is to reveal the main flow structures and properties during the SW/TLV interaction, and a theoretical criterion for vortex stability is engineeringly utilized to determine such shock wave-induced vortex stability. The validations for all numerical schemes have been conducted by comparing the RANS solutions with detailed experimental data before the analyses of flow phenomenon and mechanism. The simulation results indicate that numerical methods used in NUAA-Turbo 2.0 solver, independently developed by our team, enable to accurately capture the complex flow structures including shock wave and vortex systems within the blade passages, especially in the tip region. Similar to wing-tip vortex created by vortex generator, the TLV has the same wake-type characteristics. The flow pattern generated by such interaction is characterized by the bulged-forward shock front followed by a subsonic flow region and a slight expansion of vortex core. No apparent vortex breakdown was examined by both intuitive visualization of three-dimensional vortex structure and a theoretical criterion.

Influence of Piping on On-Line Continuous Weighing of Materials inside Process Equipment: Theoretical Analysis and Experimental Verification

Due to the continuity and complexity of chemical systems, piping and operating conditions will have a significant effect on the on-line continuous weighing of materials inside process equipment. In this paper, a mathematical model of the weighing system considering piping and operating conditions was established based on the gas–liquid continuous heat transfer weighing process. A theoretical criterion which can be extended to any continuous weighing system of the materials inside equipment with connected piping is obtained through the mechanical derivation between the material mass, the cantilever beam deflection, the strain gage deformation, and the bridge output voltage. This criterion can effectively predict the influence of piping on weighing results with specific accuracy, and provide a basis for engineering optimization design. On this basis, a set of gas–liquid continuous contact weighing devices was built. The static/dynamic experimental results showed that the accuracy of the system meets the set requirements.

Controls of boundary conditions on accelerating turbidity currents in a reservoir: Case study of Xiaolangdi Reservoir on the Yellow River, China

<p>Turbidity currents are a major way to transport sediment along reservoir, lake and sea beds. They are not fully understood yet due to the difficulty of accessibility. Theoretical criteria have been established for the conditions that generate accelerating turbidity currents, which can produce strong erosion of channel beds, transmit over long distances and thus have important significance for reservoir and sea bed morphology. However, the current theoretical criterion only utilizes local factors of hydraulic, morphology and grain size, which do not necessarily depend on the up- and down- stream boundary conditions. Here, we conducted field surveys on turbidity currents and bed morphology of the Xiaolangdi reservoir on the Yellow River, China. The survey results show clear evidence of accelerating turbidity currents. We identify two types of accelerating turbidity currents: one locates closely to the upstream plunging point where fluvial sediment-laden flow collapses to a stratified turbidity current, concentrating momentum and producing acceleration locally, and the other is located downstream and shows dependence on the enhancement of local slope and potentially on downstream boundary (flushing condition at flow outlets of the dam). So both ends of the boundaries may work together to produce long run-out turbidity currents that transmit through the entire reservoir.  Although preliminary, our dataset indicates that the conditions for accelerating turbidity currents are not only controlled by local morphology and grain size, but also by both upstream and downstream conditions. A comprehensive understanding of the boundary conditions so as to determine conditions for the generation of accelerating turbidity currents will help enhance the sustainability of the dam and reservoir system.</p>