Two-point Algorithm Research Articles

High temperature dielectric properties measurement system at 915 MHz based on deep learning

A ridged waveguide and heating system based on deep learning for dynamic measurement of dielectric properties at high temperatures has been developed. Firstly, specially designed ridged waveguide at the frequency of 915 MHz was utilized. The finite difference time domain simulation was then combined with the deep learning algorithm to construct the dielectric properties. In addition, the calibration method based on a two-point algorithm was involved in the network. The precision of the measured dielectric constant and loss tangent was improved by 4.4% and 1.9%, respectively. Simulated results indicated that the deep learning algorithm had higher accuracy than back propagation neural networks and support vector machine algorithms. The reliability of the system was verified by Si3N4 and alcohols at room temperature. The dielectric properties of quartz particles were also tested over a temperature range up to 900°C. The experiment results agreed well with the reference values. This system can measure a wider range of dielectric properties and achieve higher accuracy using the advanced deep learning algorithm. It is more convenient to measure large size materials in industrial applications at high temperatures.

Mitigation of Striping Noise in ATMS Calibration Counts by Symmetric Filters

AbstractGlobal observations from the Advanced Technology Microwave Sounder (ATMS) onboard the Suomi National Polar-Orbiting Partnership satellite are affected by striping-patterned noise. An optimal symmetric filter method to mitigate the striping noise in warm counts, cold counts, warm load temperatures, and scene counts instead of antenna temperatures is developed and tested in this study. The optimal filters are developed based on the results free of striping noise obtained with a striping noise detecting method by combining the principal component analysis and the ensemble empirical mode decomposition. The two-point algorithm is then used to calculate antenna temperatures with warm counts, cold counts, warm load temperatures, and scene counts before and after applying the optimal filters. The necessity of applying the striping noise mitigation to the scene counts besides the calibration counts (warm and cold counts) is also shown. This explains why the traditional method to smooth only calibration counts has failed to remove the ATMS striping noise. The optimal filters proposed in this study, which remove the high-frequency striping noise without altering low-frequency weather signals, outperform the conventional boxcar filters adopted in the current operational ATMS calibration system.

P4QCN: Congestion Control Using P4-Capable Device in Data Center Networks

Modern data centers aim to offer very high throughput and ultra-low latency to meet the demands of applications such as online intensive services. Traditional TCP/IP stacks cannot meet these requirements due to their high CPU overhead and high-latency. Remote Direct Memory Access (RDMA) is an approach that can be designed to meet this demand. The mainstream transport protocol of RDMA over Ethernet is RoCE (RDMA over Converged Ethernet), which relies on Priority Flow Control (PFC) within the network to enable a lossless network. However, PFC is a coarse-grained protocol which can lead to problems such as congestion spreading, head-of-the-line blocking. A congestion control protocol that can alleviate these problems of PFC is needed. We propose a protocol, called P4QCN for this purpose. P4QCN is a congestion control scheme for RoCE and it is an improved Quantized Congestion Notification (QCN) design based on P4, which is a flow-level, rate-based congestion control mechanism. P4QCN extends the QCN protocol to make it compatible with IP-routed networks based on a framework of P4 and adopts a two-point algorithm architecture which is more effective than the three-point architecture used in QCN and Data Center QCN(DCQCN). Experiments show that our proposed P4QCN algorithm achieves the expected performance in terms of latency and throughput.

Research on Power Generation Energy Sources Structure Adjustment Algorithm Based on HyperGraph

Nowadays, the energy structure is gradually changing to clean power generation. Clean energy mainly includes renewable energy and part of non-renewable energy. Non-renewable energy is depleting day by day, showing a shrinking trend. Renewable energy is not affected by energy shortage, and is the focus of future development. How to ensure the sustainable and healthy development of clean energy, it is necessary to adjust the existing power generation energy structure scientifically and rationally. In this paper, the theory of hypergraph is introduced to cluster the optimal combination information of clean energy, and a hypergraph model of power generation energy structure adjustment is established. The problem of replacing fossil energy in power generation energy consumption with clean energy is solved as the original objective. By mapping the generation energy structure adjustment with hypergraph, the problem of generation energy structure adjustment is transformed into the problem of solving hypergraph path. By using the two-point hyperpath algorithm, an optimal path for the development of clean power generation, reducing the proportion of fossil energy power generation, and gradually converting to clean energy is obtained. The application of hypergraph algorithm in the structural adjustment of power generation is of great significance to promote the diversification of power generation energy, especially in the clean development, low-carbon development and green development of the power industry.

Research on Aggregations for Algebraic Multigrid Preconditioning Methods

Aggregation based algebraic multigrid is one of the most efficient methods to solve sparse linear systems. In this paper, a new method based on cliques and several classical aggregations are implemented based on sparse data structures, and compared in solving sparse linear systems from model partial differential equations. The results show that with Vanek scheme, the number of levels is often less than that with others, and when Jacobi smoothing is used, the number of preconditioned iterations and the time elapsed for iteration are both the least, while the time for setup is too long. From the view point of strong connections, it is beneficial to aggregate the points in a common clique, but the experiments have not shown this privilege. Instead, the two-point aggregation based on strong connection is effective in most cases, and the four-point and the eight-point aggregations which are based on loop of the two-point algorithm with two or three times respectively are effective too. In respect to total computation time, the best scheme is always one of these three schemes. In addition, the larger the average degree the related adjacent graph has, the less time required for the Vanek scheme to setup is and the more efficient it is, so is the aggregation scheme based on cliques.

Accelerating NLTE radiative transfer by means of the Forth-and-Back Implicit Lambda Iteration: A two-level atom line formation in 2D Cartesian coordinates

State-of-the-art methods in multidimensional NLTE radiative transfer are based on the use of local approximate lambda operator within either Jacobi or Gauss–Seidel iterative schemes. Here we propose another approach to the solution of 2D NLTE RT problems, Forth-and-Back Implicit Lambda Iteration (FBILI), developed earlier for 1D geometry. In order to present the method and examine its convergence properties we use the well-known instance of the two-level atom line formation with complete frequency redistribution. In the formal solution of the RT equation we employ short characteristics with two-point algorithm. Using an implicit representation of the source function in the computation of the specific intensities, we compute and store the coefficients of the linear relations J=a+bS between the mean intensity J and the corresponding source function S. The use of iteration factors in the ‘local’ coefficients of these implicit relations in two ‘inward’ sweeps of 2D grid, along with the update of the source function in other two ‘outward’ sweeps leads to four times faster solution than the Jacobi’s one. Moreover, the update made in all four consecutive sweeps of the grid leads to an acceleration by a factor of 6–7 compared to the Jacobi iterative scheme.

Solution for the nonuniformity correction of infrared focal plane arrays

Based on the S-curve model of the detector response of infrared focal plan arrays (IRFPAs), an improved two-point correction algorithm is presented. The algorithm first transforms the nonlinear image data into linear data and then uses the normal two-point algorithm to correct the linear data. The algorithm can effectively overcome the influence of nonlinearity of the detector's response, and it enlarges the correction precision and the dynamic range of the response. A real-time imaging-signal-processing system for IRFPAs that is based on a digital signal processor and field-programmable gate arrays is also presented. The nonuniformity correction capability of the presented solution is validated by experimental imaging procedures of a 128 x 128 pixel IRFPA camera prototype.

New improved nonuniformity correction for infrared focal plane arrays

The nonuniformity correction for infrared focal plane arrays (IRFPA) is generally implemented in engineering by using the two-point correction algorithm. However, its correction precision is reduced by the response non-linearity of IRFPA detectors. In this paper, using the “S”-curve model to approximate the response of IRFPA detectors, an improved two-point correction algorithm is presented. The algorithm firstly transforms the non-linear image data to linear ones, and then uses the normal two-point algorithm to correct the linear data. It can effectively overcome the influence of the response non-linearity of the detectors. The experiments demonstrate the high correction precision of the new correction algorithm.

Fast centroid estimation algorithm for high-rate detectors based on a two-point Gaussian fit

Recent developments in detector back-end electronics for position sensitive gas proportional detectors have moved the data processing bottleneck out of the front-end electronics and into signal processing. Even with today's fastest DSP's, the centroid estimation of the cathode charge distribution can impose a limitation on the ultimate count rate attainable by the detector. Hen we present a centroid-finding algorithm that does the bulk of the centroid calculations based on a two-point Gaussian fit that assumes a priori knowledge of the distribution's variance. The variance is estimated only in the calibration phase. The two-point algorithm has the advantage that no division is required, greatly reducing the computational burden on the DSP. The performance of the algorithm is evaluated by implementation on existing detectors.

Mathematical theory of stereotactic coordinate transformation: elimination of rotational targeting error by addition of a third reference point. Technical note.

All frame-based stereotactic procedures require localization of an anatomical target within the coordinate system of the stereotactic frame. If the target is defined by its coordinates given in a stereotactic atlas (indirect localization), the neurosurgeon faces the mathematical task of transforming atlas coordinates into frame coordinates. In the method usually used, the frame coordinates of two reference points (the anterior and posterior commissures) are obtained from computerized tomography or magnetic resonance images, and serve as the basis for the coordinate transformation. This two-point algorithm relies on the additional assumption that the frame sits on the patient's head without exhibiting roll, that is, rotation about the anteroposterior axis (y axis). Usually this assumption is nearly, but not exactly, correct. An amount of roll as small as 3 degrees can cause a targeting error on the order of 1 mm when a two-point algorithm is used. This potential source of error can be eliminated by using a new method of coordinate transformation, the derivation of which is mathematically reported in this article. The new method requires a third reference point located in the midsagittal plane, in addition to the two commissural reference points.

Influence Of Nonuniformity On Infrared Focal Plane Array Performance

It is well known that detector response nonuniformity results in pattern noise with staring sensors that is a severe problem in the infrared due to the low intrinsic contrast of IR imagery. The pattern noise can be corrected by electronic processing; however, the ability to correct for pattern noise is limited by the interaction of interscene and intrascene variability with the dynamic range of the processor (number of bits) and, depending upon the algorithm used, by nonlinearities in the detector response. This paper quantifies these limitations and describes the interaction of detector gain nonuniformity and detector nonlinearities. Probabilistic models are developed to determine the maximum sensitivity that can be obtained using a two-point algorithm to correct a nonlinear response curve over a wide temperature range. Curves that permit a prediction of the noise equivalent differential temperature (NEAT) under varying circumstances are presented. A piecewise linear approach to dealing with severe detector response nonlinearities is presented and analyzed for its effectiveness.

A two-point difference scheme for computing steady-state solutions to the conservative one-dimensional Euler equations

An implicit finite-difference method is presented for obtaining steady-state solutions to the time-dependent, conservative Euler equations for flows containing shocks. The method uses a two-point central-difference scheme for the flux derivatives with dissipation added at supersonic points via the retarded density concept. Application of the method to 1-dimensional nozzle flow equations for various combinations of subsonic and supersonic boundary conditions show the method to be very efficient. Residuals are typically reduced to machine zero in approximately 35 time steps for 50 mesh points. For 1-dimensional Euler calculations, it is shown that the scheme offers two advantages over the more widely-used three-point schemes. The first is in regard to application of boundary conditions, and the second relates to the fact that the two-point algorithm is well-conditioned for large time steps.

Finite-difference solutions of Taylor instabilities in viscous plane flow

Abstract An integration algorithm is presented for the numerical solution of a linear, sixth-order eigenvalue problem that is associated with hydrodynamic stability of viscous flow between rotating planes. The solution method approximates the highest derivative of the eigensolutions D 6 phi(y) by passing a third-degree polynomial through three backward points and one forward point. Formulas for the lower derivatives are obtained by integration of the polynomial approximation. Linearity of the differential operator results in an explicit form for the highest derivative at the forward mesh point; a similar, two-point algorithm is used to start the computations. Neutrally stable eigensolutions associated with vortex instability of Taylor's type have been calculated for plane Couette and Poiseuille flow in a rotating system; these solutions agreed well with accepted solutions found by series-expansion methods.