Correlation analysis of PCB and comparison of test-analysis model reduction methods

AbstractThe validity of correlation analysis between finite element model (FEM) and modal test data is strongly affected by three factors, i.e., quality of excitation and measurement points in modal test, FEM reduction methods, and correlation check techniques. A new criterion based on modified mode participation (MMP) for choosing the best excitation point is presented. Comparison between this new criterion and mode participation (MP) criterion is made by using Case 1 with a simple printed circuit board (PCB). The result indicates that this new criterion produces better results. In Case 2, 35 measurement points are selected to perform modal test and correlation analysis while 9 selected in Case 3. System equivalent reduction expansion process (SEREP), modal assurance criteria (MAC), coordinate modal assurance criteria (CoMAC), pseudo orthogonality check (POC) and coordinate orthogonality check (CORTHOG) are used to show the error introduced by modal test in Cases 2 and 3. Case 2 shows that additional errors which cannot be identified by using CoMAC can be found by using CORTHOG. In both Cases 2 and 3, Guyan reduction, improved reduced system (IRS) method, SEREP and Hybrid reduction are compared for accuracy and robustness. The results suggest that the quality of the reduction process is problem dependent. However, the IRS method is an improvement over the Guyan reduction, and the Hybrid reduction is an improvement over the SEREP reduction

Synthesis of running RMS-induced non-Gaussian random vibration based on Weibull distribution

Gaussian signal is produced by ordinary random vibration controllers to test the products in the laboratory, while the field data usually is non-Gaussian. To synthesize non-Gaussian random vibration, both the probability density function (PDF) and the damage effects must be considered. A new method is presented in this paper to synthesize non-Gaussian random vibration that is characterized by running RMS (root mean square). The essential idea is to model the non-Gaussian signal by a Gaussian signal multiplied by an amplitude modulation function (AMF). A two-parameter Weibull distribution is used to model the PDF of the running RMS and to create the AMF. The shock response spectrum (SRS) is used to detect significant shocks within the non-Gaussian signal. A case study is presented to show that the synthesized non-Gaussian signal has the same power spectral density (PSD), kurtosis, PDF and fatigue damage spectrum (FDS) as the field data

Introgression of bacterial blight (BB) resistance genes Xa7 and Xa21 into popular restorer line and their hybrids by molecular marker-assisted backcross (MABC) selection scheme

Yihui1577 is an elite restorer line widely used in hybrid rice production in China, however, both the restorer and their derived hybrids are susceptible to bacterial blight (BB) caused by Xathomonas oryzae pv. oryzae (Xoo). In order to overcome this problem, we had introgressed two resistant genes Xa7 and Xa21 into Yihui1577 by marker-assisted backcross (MABC) with foreground selection scheme to speed up the process. Six breeding lines with different BB resistance genes: HH1202 (Xa7), HH1203 (Xa7), HH1204 (Xa21), HH1205 (Xa21), HH1206 (Xa7+Xa21) and HH1207 (Xa7+Xa21) were selected and crossed with four CMS and one TGMS lines. Seven most virulent and prevalent Xoo strains (PXO61, PXO99, ZHE173, GD1358, FuJ, YN24 and HeN11) from the Philippines and different provinces of China were inoculated for evaluating the BB-resistance of the selected lines and their derived hybrids. The results reveal that the two lines and their derived hybrids with single resistance gene Xa7 were resistant against six of the seven Xoo strains, except for PXO99. The lines with single resistance gene Xa21 were only susceptible to the Xoo strain FuJ, but some of their derived hybrids were susceptible to the Xoo strains FuJ and GD1358. Interestingly, the pyramiding lines carrying the two resistance genes Xa7 and Xa21 and also their derived hybrids were resistant against all the seven Xoo strains. The data of agronomic and grain quality characteristics demonstrated that the selected lines were similar to that of the recurrent parent Yihui1577. Corrective measures taken by way of introgression of BB-resistance genes: Xa7 and Xa21 into the popular restorer line, Yihui1577 through MABC approach for enhancing the BB-resistance level was effective and timely.Keywords: Bacterial blight, resistance gene, Xa7 and Xa21, MABC, inoculation and reaction, agronomic traits, grain qualit

On the Shaker Simulation of Wind-Induced Non-Gaussian Random Vibration

Gaussian signal is produced by ordinary random vibration controllers to test the products in the laboratory, while the field data is usually non-Gaussian. Two methodologies are presented in this paper for shaker simulation of wind-induced non-Gaussian vibration. The first methodology synthesizes the non-Gaussian signal offline and replicates it on the shaker in the Time Waveform Replication (TWR) mode. A new synthesis method is used to model the non-Gaussian signal as a Gaussian signal multiplied by an amplitude modulation function (AMF). A case study is presented to show that the synthesized non-Gaussian signal has the same power spectral density (PSD), probability density function (PDF), and loading cycle distribution (LCD) as the field data. The second methodology derives a damage equivalent Gaussian signal from the non-Gaussian signal based on the fatigue damage spectrum (FDS) and the extreme response spectrum (ERS) and reproduces it on the shaker in the closed-loop frequency domain control mode. The PSD level and the duration time of the derived Gaussian signal can be manipulated for accelerated testing purpose. A case study is presented to show that the derived PSD matches the damage potential of the non-Gaussian environment for both fatigue and peak response

A Criterion for Topological Close-Packed Phase Formation in High Entropy Alloys

The stability of topological close-packed (TCP) phases were found to be well related to the average value of the d-orbital energy level $\overline{Md}$ for most reported high entropy alloys (HEAs). Excluding some HEAs that contain high levels of the elements aluminum and vanadium, the results of this study indicated that the TCP phases form at $\overline{Md}$ > 1.09. This criterion, as a semi-empirical method, can play a key role in designing and preparing HEAs with high amounts of transitional elements

A new strategy to design eutectic high-entropy alloys using mixing enthalpy

Although eutectic high entropy alloys (EHEAs) display homogeneously fine microstructure, excellent castability and promising industrial application potential, how to design eutectic compositions in high entropy alloys (HEAs) remains to be challenging. Here, a novel strategy, specifically, through calculation of mixing enthalpy, was used to locate eutectic compositions in HEAs. As a proof of this concept, a series of EHEAs were located and prepared following the mixing enthalpy method. Using this new strategy, eutectic compositions can be designed conveniently, once one can classify elements into two different groups. This new alloy design strategy can be readily adapted to locate new EHEAs