Search

This paper investigates the reliability of Ball Grid Array (BGA) package with different sizes and numbers of Sn3.0Ag0.5Cu solder balls from both experimental and simulation perspectives. The fatigue life of three different sizes of BGA packaged samples was obtained by conducting temperature cycling tests and simultaneously recording the resistance changes of the specimens. The characteristic life of the three types of samples was determined using the number of thermal cycles corresponding to 63.2% probability of failure in the two-parameter Weibull distribution. In order to achieve an optimal balance between the accuracy and efficiency of the simulation based on the finite element method (FEM), the submodel method is used to model the three types of samples and calculate the key variables of the life prediction model. The effect of mesh density on equivalent creep strain (CEEQ) and creep dissipated energy results was investigated. Based on the mesh-independence results, creep dissipated energy was used as a prediction parameter to obtain the Akay fatigue life prediction model under optimal mesh density. The model’s prediction accuracy is reasonably good, as validated by simulation and experimental data. [ABSTRACT FROM AUTHOR]

In the present research, the effects of normal mean stress acting on fatigue evolution are considered well in critical plane multiaxial models, whereas shear mean stress effects have rarely attracted attention. These models may result in nonconservative predictions under asymmetric loadings with substantial shear mean stress. Therefore, an improved critical energy model is introduced to solve multiaxial fatigue issues on the basis of the Fatemi-Socie model and the Walker model, which consider normal mean effect, shear mean stress effect, and additional hardening effect. Moreover, experimental data from GH4169, wrought Ti-6Al-4V, and TC4 are employed to validate the proposed model. Results show that the proposed model can reasonably predict fatigue life under various loadings, particularly for asymmetric loadings. [ABSTRACT FROM AUTHOR]

Public concerns are increasing regarding the prevalence and transmission of antibiotic resistance genes (ARGs) in wastewater treatment plants (WWTPs), especially ARG persistence and dissemination in activated sludge (AS). However, the temporal dynamics of ARGs in the AS of WWTPs over a long period of time and their transfer potential after the treatment process upgrade (e.g., total nitrogen reduction from 20 to 15 mg/L in effluent) remain poorly explored. Here, metagenomic sequencing was performed to quantify the ARGs in AS samples from two WWTPs with different treatment processes over a 2-year period. A total of 368 and 426 ARG subtypes affiliated with 20 ARG types were identified separately in the two WWTPs and the similar core ARGs were shared by all 54 samples. There were significant differences in ARG composition in different treatment processes, yet the abundance and diversity of ARGs in the AS samples demonstrated no distinct seasonal patterns. Notably, after the treatment process upgrade, the relative abundance of sulfonamide, beta-lactam, and aminoglycoside resistance genes was reduced by more than 10%, and the transfer potential of ARGs in bacterial pathogens decreased greatly, which suggested that an upgrade could limit the prevalence and transmission of ARGs. Variation partitioning analysis showed that metal resistance genes rather than bacterial community represented the significantly influential factor in shaping ARGs, and some key genera correlated with ARGs were identified through network analysis. These results will deepen our understanding of the dynamic changes in ARG profiles in AS systems and guide wastewater treatment plant upgrades. Key points: • The potential transfer of ARGs decreased after the treatment process upgrade • Metal resistance genes were the most influential factor in shaping ARG composition • Co-occurrence networks displayed potential hosts of beta-lactam resistance genes [ABSTRACT FROM AUTHOR]

Quantitative trait locus (QTL) mapping often yields associations with dissimilar loci/genes as a consequence of diverse factors. One trait for which very limited agreement between mapping studies has been observed is resistance to white mold in soybean. To explore whether different approaches applied to a single data set could lead to more consistent results, haplotype-trait association and epistasis interaction effects were explored as a complement to a more conventional marker-trait analysis. At least 10 genomic regions were significantly associated with Sclerotinia sclerotiorum resistance in soybean, which have not been previously reported. At a significance level of α = 0.05, haplotype-trait association showed that the most prominent signal originated from a haplotype with 4-SNP (single nucleotide polymorphism) on chromosome 17, and single SNP-trait analysis located a nucleotide polymorphism at position rs34387780 on chromosome 3. All of the peak-SNPs (p-value < 0.05) of each chromosome also appeared in their respective haplotypes. Samples with extreme phenotypes were singled-out for association studies, 25–30% from each end of the phenotypic spectrum appeared in the present investigation to be the most appropriate sample size. Some key genes were identified by epistasis interaction analysis. By combining information on the nearest positional genes indicated that most loci have not been previously reported. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses suggest potential candidate genes underlying callose deposition in the cell wall and mitogen-activated protein kinase (MAPK) signaling pathway-plant, as well as plant-pathogen interaction pathway, were activated. Integration of multi-method genome-wide association study (GWAS) revealed novel genomic regions and promising candidate genes in novel regions, which include Glyma.01g048500, Glyma.03g129100, Glyma.17g072200, and the Dishevelled (Dvl) family of proteins on chromosomes 1, 3, 17, and 20, respectively. [ABSTRACT FROM AUTHOR]

High-quality rice reference genomes have accelerated the comprehensive identification of genome-wide variations and research on functional genomics and breeding. Tian-you-hua-zhan has been a leading hybrid in China over the past decade. Here, de novo genome assembly strategy optimization for the rice indica lines Huazhan (HZ) and Tianfeng (TF), including sequencing platforms, assembly pipelines and sequence depth, was carried out. The PacBio and Nanopore platforms for long-read sequencing were utilized, with the Canu, wtdbg2, SMARTdenovo, Flye, Canu-wtdbg2, Canu-SMARTdenovo and Canu-Flye assemblers. The combination of PacBio and Canu was optimal, considering the contig N50 length, contig number, assembled genome size and polishing process. The assembled contigs were scaffolded with Hi-C data, resulting in two "golden quality" rice reference genomes, and evaluated using the scaffold N50, BUSCO, and LTR assembly index. Furthermore, 42,625 and 41,815 non-transposable element genes were annotated for HZ and TF, respectively. Based on our assembly of HZ and TF, as well as Zhenshan97, Minghui63, Shuhui498 and 9311, comprehensive variations were identified using Nipponbare as a reference. The de novo assembly strategy for rice we optimized and the "golden quality" rice genomes we produced for HZ and TF will benefit rice genomics and breeding research, especially with respect to uncovering the genomic basis of the elite traits of HZ and TF. [ABSTRACT FROM AUTHOR]

The viscoplastic behavior of solder material is investigated from different scales. Due to the thermal stress in Sn–3.0Ag–0.5Cu alloy at elevated temperatures, the continuous accumulation of unrecoverable deformation becomes the key of interconnections failure in microelectronic packaging. In the current study, the rate and temperature dependence of inelastic deformation and cyclic hardening properties of Sn–3.0Ag–0.5Cu alloy under different loading conditions are studied. A novel phenomenological constitutive model is developed to describe the deformation of lead-free solder interconnections in the microelectronic packaging. The developed model is verified by comparing with the experimental data of bulk solder materials. The results show that the proposed model can accurately describe the viscoplastic properties of bulk solder materials and shows excellent numerical stability. For understanding better the overall deformation behaviors of solder joins, especially the strain–stress relationship, uniaxial compression experiments of spherical joint-scale granules were conducted under different loading rates. The developed model is applied to simulate the compression testing of granules. It shows that the developed model can characterize the viscoplastic compression deformation of Sn–3.0Ag–0.5Cu solder on joint-scale with reasonable accuracy. [ABSTRACT FROM AUTHOR]

An energy approach is proposed to describe electromigration induced void nucleation based on phase transformation theory. The chemical potential for an individual migrated atom is predicted by diffusion induced back stress equivalent principle. After determining the chemical potential for the diffusing atoms, the Gibbs free energy controlling the void nucleation can be determined and the mass diffusion process is considered. The critical void radius and nucleation time are determined analytically when the Gibbs free energy approaches the extreme value. The theoretical predictions are compared with the experimental results from literatures and show good accuracy. The proposed model can also be applied to other diffusion induced damage processes such as thermomigration and stress migration. [ABSTRACT FROM AUTHOR]

Bacterial communities in the activated sludge (AS) determine the wastewater treatment performance in the municipal wastewater treatment plants (WWTPs). Aiming at identifying the affecting factors and the variation patterns of the bacterial assemblages in AS, a 2-year time-series AS samples were collected from two separated WWTPs and metagenomic sequencing was conducted. Obvious seasonal shift and succession of the bacterial community were observed in both WWTPs on the genus and species levels, especially for the persistent taxa, implying that temperature was a decisive factor for maintaining bacterial assemblage patterns in long-term period. Taxa abundance distribution (TAD) concerning occurrence frequency and average abundance were found fitting for exponential formulations, and the approximately equal total abundance of persistent taxa suggested that stable and high abundance (~ 90%) of core functional bacterial groups would help to maintain wastewater treatment performance. Drastic changes of environmental factors were found causing temporally significant bacterial structure variation, while the innate correlations between bacterial species could recover the community gradually and maintain relative stability of the AS system. Delayed correlations between environmental factors and abundant (persistent or intermittent) bacterial species were observed widely, while synchronous biotic interactions were identified more frequently. Besides, bacterial species with similar functions were prone to cluster together and shared the same seasonal variation pattern, implicating that the cooperation of functional correlated taxa played the most dominant role in shaping the bacterial assemblages. Furthermore, rare bacterial groups were to be explored for removing emerging pollutants with lower concentrations. The results of this study would assist dealing with operational defect and optimize the treatment system in WWTPs. [ABSTRACT FROM AUTHOR]

In this paper, multi-modal computer image is identified based on deep neural network. First, we propose two rules for reduction. The first reduction rule is used to reduce the number of similarity calculations between adjacent vertices. The second reduction rule reduces calculation time by inaccurately calculating the similarity between adjacent vertices. Secondly, a structured graph based on GraphX in Spark is proposed Class Algorithm GXDSGC. The algorithm does not require a large amount of disk I/O overhead during operation. Finally, experiments on a large number of real data sets and synthetic data sets, confirm the effectiveness of the proposed GXDSGC algorithm. The GXDSGC algorithm is more than 30 times faster than the algorithm based on the MapReduce framework in Hadoop, which can significantly improve the efficiency of computer image recognition in big data analysis. [ABSTRACT FROM AUTHOR]

Anaerobic ammonium oxidation (anammox)-based nitrogen removal saves aeration energy and organic carbon costs, attributed to its anaerobic and autotrophic nature. However, due to the slow growth of anaerobic ammonium oxidation bacteria (AnAOB), drawbacks including long startup time and sensitivity to toxins still hamper the application of anammox-based processes. To cope with the slow growth of AnAOB, various bioreactor configurations have been investigated for the capability of retaining anammox biomass, among which, the expanded granular sludge bed (EGSB) reactor is a promising option. In this study, two laboratory-scale EGSB reactors were used to gain insights of microbial population and their response to amending biofilm-carriers, aiming to enhance the biomass retention of AnAOB. The respective ammonium and nitrite removal efficiencies were up to over 90%, and the overall nitrogen removal efficiency (NRE) was stable at over 70%, in the EGSB reactor amended with carriers (CEGSB). Compared to the control EGSB, CEGSB's observed performance was more stable during the 236-day operational period. The abundance of AnAOB reached 22% in the EGSB and 49% in the CEGSB. It was also observed that Ca. Brocadia (14.25%) and Asahi BRW2 (33.19%) coexisted in the CEGSB. The dynamics of major metabolisms and functional genes involved in nitrogen conversion were further observed by FAPROTAX based on the taxonomic data, providing more insights into the functions of the microbial communities. [ABSTRACT FROM AUTHOR]

In this work, analysis of electromigration-induced void morphological evolution in solder interconnects is performed based on mass diffusion theory. The analysis is conducted for three typical experimentally observed void shapes: circular, ellipse, and cardioid. Void morphological evolution is governed by the competition between the electric field and surface capillary force. In the developed model, both the electric field and capillary force on the void's surface are solved analytically. Based on the mass conversation principle, the normal velocity on the void surface during diffusion is obtained. The void morphological evolution behavior is investigated, and a physical model is developed to predict void collapse to a crack or to split into sub-voids under electric current. It is noted that when the electric current is being applied from the horizontal direction, a circular void may either move stably along the electric current direction or collapse to a finger shape, depending on the relative magnitude of the electric current and surface capillary force. However, the elliptical-shaped void will elongate along the electric current direction and finally collapse to the finger shape. On the other hand, the cardioid-shaped void could bifurcate into two sub-voids when the electric current reaches a critical value. The theoretical predictions agree well with the experimental observations. [ABSTRACT FROM AUTHOR]

Copy number variants (CNVs) are associated with changes in gene expression levels and contribute to various adaptive traits. Here we show that a CNV at the Grain Length on Chromosome 7 (GL7) locus contributes to grain size diversity in rice (Oryza sativa L.). GL7 encodes a protein homologous to Arabidopsis thaliana LONGIFOLIA proteins, which regulate longitudinal cell elongation. Tandem duplication of a 17.1-kb segment at the GL7 locus leads to upregulation of GL7 and downregulation of its nearby negative regulator, resulting in an increase in grain length and improvement of grain appearance quality. Sequence analysis indicates that allelic variants of GL7 and its negative regulator are associated with grain size diversity and that the CNV at the GL7 locus was selected for and used in breeding. Our work suggests that pyramiding beneficial alleles of GL7 and other yield- and quality-related genes may improve the breeding of elite rice varieties. [ABSTRACT FROM AUTHOR]