Synchronization of two coupled exciters in a vibrating system of spatial motion

The paper proposes an analytical approach to investigate the synchronization of the two coupled exciters in a vibrating system of spatial motion. Introducing the distur- bance parameters for average angular velocity of two excit- ers, we deduce the non-dimensional coupling equations of angular velocities of two exciters, in which the inertia cou- pling matrix is symmetric and the stiffness coupling matrix is antisymmetric in a non-resonant vibrating system. The analysis of the coupling dynamic characteristic shows that the coupled cosine effect of the phase angles will cause the torque acting on two motors to limit the increase of phase difference between two exciters as well as sustain its sym- metry of two exciters during the running process. It physi- cally explains the peculiarity of self-synchronization of two exciters. The cosine effect of phase angles of the vibrations excited by each exciter will decrease its moment of inertia. The residual moment of inertia of each exciter represents its relative moment of inertia. The stability condition of synchro- nization of two exciters is that the relative non-dimensional moments of inertia of two exciters are all greater than zero and four times their product is greater than the square of their coefficient of coupled cosine effect of phase angles, which is equivalent to that the inertia coupling matrix is positive definite and all its elements are positive. The numeric results show that the structure of the vibrating system can ensure the stability condition of synchronous operation.

Recognition and Prediction of Source Rocks of the Madingo Formation in the Lower Congo Basin

We investigated the petrological and seismic properties of Madingo Formation, the highquality source rocks in the Madingo Formation in the Lower Congo Basin are highly heterogeneous. Due to little drilling and oil-based mud pollution, samples that are able to be used to measure the TOC(total organic carbon) content of source rock in the Madingo Formation are few and unevenly distributed;hence, it is difficult to carry out their quantitative evaluation. We investigated the petrological and seismic properties of Madingo Formation between TOC and well logging parameters including density, natural gamma, and acoustic time difference via multiple regression analysis. The TOC data volume is calculated using a neural network model between the predicted TOC content and seismic attributes of the sidetrack. The results of TOC three-dimensional quantitative prediction in the study area show that the source rocks in the Madingo Formation have a strong heterogeneity in the vertical direction, and the plane distribution is low in the northeast and high in the southwest. This study provides suitable tools to predict the complex heterogeneous distribution of source rocks and has great significance for oil exploration in the Lower Congo Basin.

Degradation behavior of 17α-ethinylestradiol by ozonation in the synthetic secondary effluent

Endocrine disrupting chemicals（EDCs） in the secondary effluent discharged from wastewater treatment plants（WWTPs） are of great concern in the process of water reuse.Ozonation has been reported as a powerful oxidation technology to eliminate micropollutants in water treatment.Due to the complexity of the wastewater matrix,orthogonal experiments and single factor experiments were conducted to study the influence of operational parameters on the degradation of 17α-ethinylestradiol（EE2） in the synthetic secondary effluent.The results of the orthogonal experiments indicated that the initial ozone and natural organic matter（NOM） concentration significantly affected EE2 degradation efficiency,which was further validated by the single factor confirmation experiments.EE2 was shown to be effectively degraded by ozonation in the conditions of low pH（6）,NOM（10 mg/L）,carbonate（50 mg/L）,but high suspended solid（20 mg/L） and initial ozone concentration（9 mg/L）.The study firstly revealed that the lower pH resulted in higher degradation of EE2 in the synthetic secondary effluent,which differed from EDCs ozonation behavior in pure water.EE2 degradation by ozone molecule instead of hydroxyl radical was proposed to play a key role in the degradation of EDCs by ozonation in the secondary effluent.The ratio between O3 and TOC was identified as an appropriate index to assess the degradation of EE2 by ozonation in the synthetic secondary effluent.

Experimental study of surface integrity and fatigue life in the face milling of Inconel 718

The Inconel 718 alloy is widely used in the aerospace and power industries. The machining-induced surface integrity and fatigue life of this material are important factors for consideration due to high reliability and safety requirements. In this work, the milling of Inconel 718 was conducted at different cutting speeds and feed rates. Surface integrity and fatigue life were measured directly. The effects of cutting speed and feed rate on surface integrity and their further influences on fatigue life were analyzed. Within the chosen parameter range, the cutting speed barely affected the surface roughness, whereas the feed rate increased the surface roughness through the ideal residual height. The surface hardness increased as the cutting speed and feed rate increased. Tensile residual stress was observed on the machined surface, which showed improvement with the increasing feed rate. The cutting speed was not an influencing factor on fatigue life, but the feed rate affected fatigue life through the surface roughness. The high surface roughness resulting from the high feed rate could result in a high stress concentration factor and lead to a low fatigue life.

Influence of white etching layer on rolling contact behavior at wheel-rail interface

The existence of narrow and brittle white etching layers(WELs)on the rail surface is often linked with the formation of rail defects such as squats and studs,which play the key roles in rail surface degradation and tribological performance.In the present study,a systematic investigation on stress/strain distribution and fatigue life of the WEL during wheel-rail rolling contact was conducted based on a numerical model considering the realistic wheel geometry.This is the first study considering the influence of rail materials,loading pressure,frictional condition,WEL geometry(a/b),and slip ratio(Sr)in the practical service conditions at the same time.The results revealed much higher residual stress in WEL than in rail matrix.Stress changes along the rail depth matched with the previously reported microstructure evolutions.The current work revealed that the maximum difference in contact stress between the wheel passages of rail matrix and the WEL region(noted as stress variation)rises with the increase of loading pressure,the value of a/b,and Sr;but drops with the friction coefficient(μ).In addition,a critical length–depth ratio of 5 for a/b has been found.The fatigue parameter,FP,of the WEL decreased quickly with the length–depth ratio when it was less than 5 and then increased slightly when it was larger than 5.This study also revealed that the fatigue life of the WEL was reduced for high strength head hardened(HH)rail compared with standard carbon(SC)rail.

Mechanism of the Rpn13-induced activation of Uch37

Uch37 is a de-ubiquitinating enzyme that is activated by Rpn13 and involved in the proteasomal degradation of proteins. The full-length Uch37 was shown to exhibit low iso-peptidase activity and is thought to be auto-inhibited. Structural comparisons revealed that within a homo- dimer of Uch37, each of the catalytic domains was blocking the other＇s ubiquitin （Ub）-binding site. This blockage likely prevented Ub from entering the active site of Uch37 and might form the basis of auto-inhibition. To understand the mode of auto-inhibition clearly and shed light on the activation mechanism of Uch37 by Rpn13, we investigated the Uch37-Rpn13 complex using a combi- nation of mutagenesis, biochemical, NMR, and small- angle X-ray scattering （SAXS） techniques. Our results also proved that Uch37 oligomerized in solution and had very low activity against the fluorogenic substrate ubi- quitin-7-amino-4-methylcoumarin （Ub-AMC） of de-ubiq- uitinating enzymes. Uch37AHb＇Hc＇KEKE, a truncation removal of the C-terminal extension region （residues 256- 329） converted oligomeric Uch37 into a monomeric form that exhibited iso-peptidase activity comparable to that of a truncation-containing the Uch37 catalytic domain only. We also demonstrated that Rpn13C （Rpn13 residues 270- 407） could disrupt the oligomerization of Uch37 by sequestering Uch37 and forming a Uch37-Rpn13 com- plex. Uch37 was activated in such a complex, exhibiting 12-fold-higher activity than Uch37 alone. Time-resolved SAXS （TR-SAXS） and FRET experiments supported the proposed mode of auto-inhibition and the activation mechanism of Uch37 by Rpn13. Rpn13 activated Uch37 by forming a 1：1 stoichiometric complex in which the active site of Uch37 was accessible to Ub.

Effect of high pressure torsion process on the microhardness,microstructure and tribological property of Ti6Al4V alloy

In the present study,a fully lamellar Ti6Al4V alloy was severely deformed by high pressure torsion(HPT)process under a pressure of 7.5 GPa up to 10 revolutions.Experimental results revealed that the microhardness of Ti6Al4V was increased remarkably by about~41%and saturated at about 432 Hv after the HPT process.A relatively uniform bulk nanostructured Ti6Al4V alloy with an average grain size of about52.7 nm was obtained eventually,and no obvious formation of metastableωphase was detected by XRD analysis.For the first time,the tribological properties of the HPT processed Ti6Al4V alloy were investigated by a ball-on-disc test at room temperature under a dry condition.It was found that HPT process had a great influence on the friction and wear behaviors of Ti6Al4V alloy.With increasing the number of HPT revolutions,both friction coefficient and specific wear rate were obviously decreased due to the reduction of abrasion and adhesion wears.After being deformed by 10 HPT revolutions,the friction coefficient was reduced from about 0.49 to 0.37,and the specific wear rate was reduced by about 48%.The observations in this study indicated that HPT processed Ti6Al4V alloys had good potential in structural applications owing to their greatly improved mechanical and tribological properties.

A molecular dynamics study on the tribological behavior of molybdenum disulfide with grain boundary defects during scratching processes

The effect of grain boundary(GB)defects on the tribological properties of MoS_(2) has been investigated by molecular dynamics(MD)simulations.The GB defects‐containing MoS_(2) during scratching process shows a lower critical breaking load than that of indentation process,owing to the combined effect of pushing and interlocking actions between the tip and MoS_(2) atoms.The wear resistance of MoS_(2) with GB defects is relevant to the misorientation angle due to the accumulation of long Mo-S bonds around the GBs.Weakening the adhesion strength between the MoS_(2) and substrate is an efficient way to improve the wear resistance of MoS_(2) with low‐angle GBs.

Potential application of graphene nanoplatelets as a high temperature lubricant for hot rolling

Graphene has been shown to be a promising solid lubricant to reduce friction and wear of the sliding counterparts,and currently is reported to only function below 600℃.In this study,its potential as a lubricant above 600℃ was studied using a ball-on-disc tribo-meter and a rolling mill.Friction results suggest that a reduction up to 50%can be obtained with graphene nanoplatelets(GnP)under lubricated conditions between 600 and 700℃ when compared with dry tests.and this friction reduction can last more than 3 min.At 800 and 900℃,the friction reduction is stable for 70 and 40 s,respectively,which indicates that GnP can potentially provide an effective lubrication for hot metal forming processes.Hot rolling experiments on steel strips indicate that GnP reduces the rolling force by 11%,7.4%,and 6.9%at 795,890,and 960℃,respectively.These friction reductions are attributed to the easily sheared GnP between the rubbing interfaces.A temperature higher than 600℃ will lead to the gasification of the residual graphene on the strip surface,which is believed to reduce the black contamination from traditional graphite lubricant.

Bisphenol A removal from synthetic municipal wastewater by a bioreactor coupled with either a forward osmotic membrane or a microfiltration membrane unit

Forward osmotic membrane bioreactor is an emerging technology that combines the advantages of forward osmosis and conventional membrane bioreactor. In this paper, bisphenol A removal by using a forward osmotic membrane bioreactor and a conventional mem- brane bioreactor that shared one biologic reactor was studied. The total removal rate of bisphenol A by the conventional membrane bioreactor and forward osmotic membrane bioreactor was as high as 93.9% and 98%, respectively. Biodegradation plays a dominant role in the total removal of bisphenol A in both processes. In comparison of membrane rejection, the forward osmosis membrane can remove approximately 70% bisphenol A from the feed, much higher than that of the microfiltration membrane （below 10%）. Forward osmosis membrane bioreactor should be operated with its BPA loading rate under 0.08 mg. g-1. d-1 to guarantee the effluent bisphenol A concentration less thanlO μg·L-1.

Genetic Architecture of Childhood Kidney and Urological Diseases in China

Kidney disease is manifested in a wide variety of phenotypes,many of which have an important hereditary component.To delineate the genotypic and phenotypic spectrum of pediatric nephropathy,a multicenter registration system is being imple-mented based on the Chinese Children Genetic Kidney Disease Database(CCGKDD).In this study,all the patients with kidney and urological diseases were recruited from 2014 to 2020.Genetic analysis was conducted using exome sequencing for families with multiple affected individuals with nephropathy or clinical suspicion of a genetic kidney disease owing to early-onset or extrarenal features.The genetic diagnosis was confirmed in 883 of 2256(39.1%)patients from 23 provinces in China.Phenotypic profiles showed that the primary diagnosis included steroid-resistant nephrotic syndrome(SRNS,23.5%),glomerulonephritis(GN,32.2%),congenital anomalies of the kidney and urinary tract(CAKUT,21.2%),cystic renal disease(3.9%),renal calcinosis/stone(3.6%),tubulopathy(9.7%),and chronic kidney disease of unknown etiology(CKDu,5.8%).The pathogenic variants of 105 monogenetic disorders were identified.Ten distinct genomic disorders were identified as pathogenic copy number variants(CNVs)in 11 patients.The diagnostic yield differed by subgroups,and was highest in those with cystic renal disease(66.3%),followed by tubulopathy(58.4%),GN(57.7%),CKDu(43.5%),SRNS(29.2%),renal calcinosis/stone(29.3%)and CAKUT(8.6%).Reverse phenotyping permitted correct identification in 40 cases with clinical reassessment and unexpected genetic conditions.We present the results of the largest cohort of children with kidney disease in China where diagnostic exome sequencing was performed.Our data demonstrate the utility of family-based exome sequencing,and indicate that the combined analysis of genotype and phenotype based on the national patient registry is pivotal to the genetic diagnosis of kidney disease.