Experimental study on long friction-type bolted joint combined with interference fit bolt

In recent years, high-strength bolts with friction-type joints have been lengthened to withstand increased traffic load. However, with increase in the joint length, the force able to be resisted by bolted joints has decreased owing to uneven distribution of the bolts within the joint. In addition, the proximity of secondary members to the joint has restricted the allowable size of the splice plates. It is therefore necessary to reduce the joint length while maintaining its design strength. In this study, interference fit bolts were assembled at both ends of a friction-type bolted joint to form a hybrid joint, and tensile tests were conducted to elucidate the load transmission mechanism, analyse the slip resistance, and verify whether the addition of the interference fit bolts improves the strength of the friction-type joint. It was concluded that despite a minor slip in the hybrid joint, the slip resistance was approximately 10% higher than that of the friction-type joint, and the overall load–deformation relationship maintained a quasi-linear behaviour up to 1.1 times the slip resistance of the friction-type joint. In addition, the hybrid joint had smaller data scattering than the friction-type joint, suggesting that the uneven load distribution and deformation in the joint was slightly improved by installing the interference fit bolts. The performance of hybrid joints is superior to that of the existing friction-type joints under the current slip limit specification.</p

A Single-Granule-Level Approach Reveals Ecological Heterogeneity in an Upflow Anaerobic Sludge Blanket Reactor

<div><p>Upflow anaerobic sludge blanket (UASB) reactor has served as an effective process to treat industrial wastewater such as purified terephthalic acid (PTA) wastewater. For optimal UASB performance, balanced ecological interactions between syntrophs, methanogens, and fermenters are critical. However, much of the interactions remain unclear because UASB have been studied at a “macro”-level perspective of the reactor ecosystem. In reality, such reactors are composed of a suite of granules, each forming individual micro-ecosystems treating wastewater. Thus, typical approaches may be oversimplifying the complexity of the microbial ecology and granular development. To identify critical microbial interactions at both macro- and micro- level ecosystem ecology, we perform community and network analyses on 300 PTA–degrading granules from a lab-scale UASB reactor and two full-scale reactors. Based on MiSeq-based 16S rRNA gene sequencing of individual granules, different granule-types co-exist in both full-scale reactors regardless of granule size and reactor sampling depth, suggesting that distinct microbial interactions occur in different granules throughout the reactor. In addition, we identify novel networks of syntrophic metabolic interactions in different granules, perhaps caused by distinct thermodynamic conditions. Moreover, unseen methanogenic relationships (e.g. “<i>Candidatus</i> Aminicenantes” and <i>Methanosaeta</i>) are observed in UASB reactors. In total, we discover unexpected microbial interactions in granular micro-ecosystems supporting UASB ecology and treatment through a unique single-granule level approach.</p></div

Boxplots of observed OTUs (lower box plots) and Chao1 (upper box plots).

<p>The dash lines indicate the statistical differences based on unpaired Welch’s t-test. The gray and black lines are p-value <0.05 in Chao1 and observed OTUs and p-value <0.05 in observed OTUs.</p

Venn diagram of the shared microorganisms in PTA-watewater treatment UASB granules.

<p>Syntrophs and methanogens are highlighted by green and blue, respectively.</p

Abundance of predominant OTUs in reactors E, F and U1 using bubble plots.

<p><i>Circle sizes</i> correspond to abundance rate, as shown at the bottom of the figure. <i>Circle lines</i> indicate the statistical differences of OTU abundance between different granule types based on Welch’s t-test (p<0.05).</p

Network of predominant microorganisms in reactor E based on Spearman’s correlation analysis(Spearman’s <i>rs</i> > 0.4 and p-value < 0.001).

<p>Highlighted blue and green lines indicate the positive correlations between methanogens and syntrophs and strong positive correlations between “<i>Candidatus</i> Aminicenantes” and <i>Methanosaeta</i> (<i>rs</i> > 0.7), respectively. Light blue and light orange lines indicate the positive and negative correlations, respectively. <i>Circle sizes</i> correspond to average abundance rate, as shown at the left bottom of the figure. Orange circle color shows the methanogens nodes including <i>Methanosaeta</i> (MS), <i>Methanomethylovorans</i> (MV), <i>Methanobacterium</i> (MB), <i>Methanolinea</i> (ML), and <i>Methanomassiliicoccus</i> (MM). Light green circle color shows the syntrophs nodes including <i>Syntrophaceae</i> (SPH) and <i>Syntrophorhabdacea</i> (SHB). <i>Bacteroidales</i> (BCT), <i>Rikenelaceae</i> (RIK), and <i>Treponema</i> (TPN) were indicated with light brown, dark gray, and brown circle colors, respectively.</p

Ratio of consumed methane and reduced electron acceptors in continuous cultures in operation days of 794 to 832.

<p>Ratio of consumed methane and reduced electron acceptors in continuous cultures in operation days of 794 to 832.</p

Fluorescence in situ hybridization of biomass from nitrite fed continuous culture (A), nitrate fed continuous culture (B), nitrite batch culture (C), and nitrate batch culture (D).

<p>Epifluorescence micrographs taken after hybridization with the general bacterial probes of Alex488-labeled EUB338, EUB338 II, and EUB338 III (green), Cy3-labeled NC10-1162, DBACT-193, and DBACT-447 for NC10 bacteria (Red). Bacteria related to <i>M. oxyfera</i> appear yellow due to co- hybridization with both probes.</p

Methane oxidation, denitrification, and nitrite (A) or nitrate (B) reduction of batch cultures.

<p>Methane oxidation, denitrification, and nitrite (A) or nitrate (B) reduction of batch cultures.</p

Phylogenetic tree constructed with the neighbor- joining method of the <i>pmoA</i> genes identified from paddy field soil and enrichment cultures.

<p>The sequence of the <i>amoA</i> gene from Nitrosomonas europaea (L08050) was used as an outgroup. Clones obtained in this study are in bold: clones in the series “NO2K-”, “NO3K-” were obtained from the batch cultures A and B, respectively; clones “NO2R-”, “NO3R-” were obtained from the continuous culture reactors A and B, respectively. The scale bar represents the number of nucleotide changes per sequence position. The numbers at each branch point are bootstrap values obtained by 1,000 resampling analysis.</p