Study of the truncation strategy in the FPGA of a solar radio digital receiver

Computation resource is the limiting factor in higher operational accuracy of field-programmable gate arrays (FPGAs) in solar radio digital receivers. The data truncation strategy which determines the accuracy of data is then the essential technology in the design of a receiving system. Based on the solar radio spectrometer (dual channel, 14 bit, 1.25 gigasamples per second) at the Chashan Solar Radio Observatory (CSO), this paper presents a data truncation strategy which can realize real-time solar radio observation (35–40 GHz) with high time and frequency resolution as well as a large dynamic range, and at the same time saves the computation resource to a large extent. Simulations of truncations during signal processing are carried out in MATLAB, and the best truncation mechanisms are deduced for windowing and fast Fourier transform (FFT). Using the simulation results, the best truncation strategies have been implemented in the solar radio receiver at CSO with the result that the best truncation bits for the windowing operation are [27 : 14], with an error of 2.5 × 10−4, and the best truncation bits for the FFT output are [20 : 5] with an error of 1.5 × 10−3. Compared with the processing of full-precision data, occupation of the computation resources in the FPGA can be reduced significantly. For instance, the lookup table, lookup table RAM, flip flop, and digital signal processing slices are reduced by 7.36%, 14.65%, 8.38%, and 24.94%, respectively, which guarantees broad-band real-time solar radio observations (35–40 GHz).

A Structural Pounding Formulation Using Systematic Modal Truncation

The evaluation of the response function of the structural pounding problem is generally time-consuming if high-order systems are applied. The well-known modal truncation strategy is outstandingly efficient for a single linear ground-accelerated structure. However, for the analysis of the structural pounding problem, the classical modal truncation technique turns out to be ineffective as additional higher frequency motion due to possible contact impact occurs. This makes the determination of how many modes should be taken into account in order to obtain a required level of accuracy more difficult. Therefore, in this paper, a systematically controlled modal truncation strategy adapted to the seismic pounding formulation under consideration of high nonlinearity and nonsmoothness of contact problems is introduced. A comparative study of the classical and the controlled modal truncation technique is presented and a comparison with the commercial software package ABAQUS© is provided. It is shown that the computational accuracy is significantly improved when applying the new systematically controlled modal truncation strategy.

A metal–organic framework based on a custom-designed diisophthalate ligand exhibiting excellent hydrostability and highly selective adsorption of C2H2 and CO2 over CH4

The ligand truncation strategy was employed to devise a novel bent diisophthalate ligand which was used to construct a copper-based MOF exhibiting highly selective C2H2/CH4 and CO2/CH4 separations.