Finite element analysis of stress distribution and burst failure of SiC_f/Ti-6Al-4V composite ring

A three-dimensional cyclic symmetry finite element model of titanium-matrix composites（TMCs） ring was developed to investigate the stress distribution and burst failure. The effects of fiber volume fractions, reinforced areas, thermal residual stresses and two different temperatures on stress distribution were studied. The burst speed was obtained through analyzing the hoop tensile stresses under a series of rotating speeds. The results indicate that at the two different temperatures, the influences of fiber volume fractions and reinforced areas on stress level and distribution are different. Some proposals are provided for the structure design of the TMCs ring. With regard to thermal residual stresses, a larger reinforced area is an advisable choice for design of the ring at higher temperature.

Fluorescence Microscopic Image Analysis of Nucleic Acids Based on The Capillary Flow Directed Assembly Ring of Neutral Red-nucleic Acid Supramolecular Complexes

It is critical to establish a direct and precise method with a high sensitivity and selectivity in analytical chemistry. In this research, making use of a well known phenomenon of capillary flow, we have proposed an image analysis method of nucleic acids at the price of a small amount of sample. When a droplet of the supramolecular complex solution, formed by neutral red and nucleic acids(NA) under an approximate neutral condition, was placed on the hydrophobic surface of dimethyl dichlorosilane pretreated glass slides, and it was evaporated, the supramolecular complex exhibited the periphery of the droplet due to the capillary effect, and accumulated there to form a red capillary flow directed assembly ring(CFDAR). A typical CFDAR has an outer diameter of (2 r ) about 1.18 mm and a ring width(2 δ ) of about 41 μm. Depending on the experimental conditions, a variety of CFDAR can be assembled. The experimental results are in agreement with our former theoretical discussion. It was found that when a droplet volume is 0.1 μL, the fluorescence intensity of the CFDAR formed by the NR NA is in proportion to the content of calf thymus DNA in the range of 0-0.28 ng, fish sperm DNA of 0-0.24 ng and yeast RNA of 0-0.16 ng with the limit of detection(3 σ ) of 1 7, 1.4 and 0.9 pg, respectively for the three nucleic acids.

Failure analysis of wear of main clutch separating ring of heavy vehicles

The severe wear of separating ring is considered to be a main reason which leads to the improper declutch of the main clutch of heavy vehicles. The wear mechanism of the separating ring is not well understood. Scanning electron microscopy and transmission electron microscopy were employed to analyze the surface features and dislocation characteristics of the separating ring. The typical features of furrows and rolled tongue-like metal were found on the surface of separating ring by scanning electron microscopy observation, which can be considered as a major indication of the grain-abrasion. A zone of high density dislocation was noted on the subsurface of the separating ring by transmission electron microscopy observation, which implies the contribution of the severe impact on the surface of the separating ring in the wear process. The influences of the structure of the separating ring, the service condition and the in-service stress distribution on the wear behavior, were also analyzed. The results show that the failure of separating ring results from the impact wear and grain-abrasion together with the plastic deformation.

Genome-wide identification and expression analysis of Gossypium RING-H2 finger E3 ligase genes revealed their roles in fiber development,and phytohormone and abiotic stress responses

Background： RING H2 finger E3 ligase （RH2FE3） genes encode cysteine rich proteins that mediate E3 ubiquitin ligase activity and degrade target substrates. The roles of these genes in plant responses to phytohormones and abiotic stresses are well documented in various species, but their roles in cotton fiber development are poorly understood. To date, genome wide identification and expression analyses of Gossypium hirsutum RH2FE3 genes have not been reported. Methods： We performed computational identification, structural and phylogenetic analyses, chromosomal distribution analysis and estimated KJKs values of G hirsutum RH2FE3 genes. Orthologous and paralogous gene pairs were identified by all versus all BLASTP searches. We predicted cis regulatory elements and analyzed microarray data sets to generate heatmaps at different development stages. Tissue specific expression in cotton fiber, and hormonal and abiotic stress responses were determined by quantitative real time polymerase chain reaction （qRT PCR） analysis. Results： We investigated 140 G hirsutum, 80 G. orboreum, and evolutionary mechanisms and compared them with orthologs 89 G. roimondii putative RH2FB genes and their in Arobidopsis and rice. A domain based analysis of the G hirsutum RH2FE3 genes predicted conserved signature motifs and gene structures. Chromosomal localization showed the genes were distributed across all G hirsutum chromosomes, and 60 duplication events （4 tandem and 56 segmental duplications） and 98 orthologs were detected, cis elements were detected in the promoter regions of G hirsutum RH2FE3 genes. Microarray data and qRT PCR analyses showed that G hirsutum RH2FE3 genes were strongly correlated with cotton fiber development. Additionally, almost all the （brassinolide, gibberellic acid （GA）, indole 3-acetic acid drought, and salt）. dentified genes were up regulated in response to phytohormones （IAA）, and salicylic acid （SA）） and abiotic stresses （cold, heat, Conclusions： The genome wide identification, comprehensive analysis, and characterization of conserved domains and gene structures, as well as phylogenetic analysis, cis element prediction, and expression profile analysis of G hirsutum RH2FE3 genes and their roles in cotton fiber development and responses to plant hormones and abiotic stresses are reported here for the first time. Our findings will contribute to the genome wide analysis of putative RH2FE3 genes in other species and lay a foundation for future physiological and functional research on G hirsutum RH2FE3 genes.

Identification of key genes and pathways in gastric signet ring cell carcinoma based on transcriptome analysis

BACKGROUND Gastric signet ring cell carcinoma(GSRCC)is one of the most malignant tumors.It has the features of high invasiveness,rapid progression,and resistance to chemotherapy.However,systematic analyses of mRNAs have not yet been performed for GSRCC.AIM To identify key mRNAs and signaling pathways in GSRCC.METHODS A transcriptome analysis of two GSRCC and two non-GSRCC samples was performed in this study.Differentially expressed mRNAs and pathways were identified based on the KEGG and PANTHER pathway annotations.The interactive relationships among the differential genes were mapped with the STRING database.Quantitative real-time polymerase chain reaction was used to validate the key gene expression in GSRCC.RESULTS About 1162 differential genes(using a 2-fold cutoff,P<0.05)were identified in GSRCC compared with non-GSRCC.The enriched KEGG and PANTHER pathways for the differential genes included immune response pathways,metabolic pathways,and metastasis-associated pathways.Ten genes(MAGEA2,MAGEA2B,MAGEA3,MAGEA4,MAGEA6,MUC13,GUCA2A,FFAR4,REG1A,and REG1B)were identified as hub genes in the protein-protein interaction network.The expression levels of five genes(MAGEA2,MAGEA3,MAGEA4,MAGEA6,and REG1B)showed potential clinical value.CONCLUSION We have identified the potential key genes and pathways in GSRCC,and these hub genes and pathways could be diagnostic markers and therapeutic targets for GSRCC.

Failure analysis of ring die of a feed pellet machine

The severely worn position and failure mechanisms of the ring die of a feed pellet machine were investigated.The macroscopic and microscopic morphologies of the failed surface,the chemical composition and mechanical properties of the collected samples were analyzed using scanning electron microscopy,energy disperse spectroscopy,optical emission spectrometry,and a universal testing machine.Results show that the dip angle at the entrance of the ring die hole between the roller and ring die was severely worn.The feed powder could not be fully extruded through the dip angle at the entrance of the ring die holes,thus the density of the feed particles produced could not meet the requirements.Therefore,abrasive wear under high stress is the main reason of failure at the entrance of the ring die holes under the action of feeding powder;and cutting and fatigue spalling lead to substantial material loss.In addition,a high damp-heat environment aggravates abrasive wear on the die hole internal surface.

Otolith Shape Analysis as a Tool to Identify Two Pacific Saury(Cololabis saira) Groups from a Mixed Stock in the High-Seas Fishing Ground

The Pacific saury Cololabis saira is a commercially important pelagic species with wide distribution in the North Pacific Ocean. Previous studies identified two geographical groups by comparing the radius of otolith annual rings(ROA) of the fish collected during the pre-fishing season. Moreover, understanding the group composition in the mixed catch from the fishing ground is essential for sustainable exploitation of this species. Using samples collected during the fishing season(July–November) from 2016 to 2018, the potential of applying otolith shape analysis as a tool to identify these two mixed groups was tested in this research. Two otolith morphotypes that belong to the eastern group and western group were identified by K-means cluster analysis using Fourier coefficients and ROA. The high classification success of random forest further confirmed the effectiveness of otolith shape analysis. The western group accounted for the majority of catch in July and August at 160?E. With the passing of sampling time and fishing fleets moving westward, the proportion of eastern group gradually increased and finally reached more than 60% of the whole catch in November at 150°E. This result suggests that the eastern and western groups are well mixed during spawning migration. In addition, the temporal and spatial dynamics of their catch composition provide information for their migration route. This study is helpful for improving fisheries management and understanding the short-term stock fluctuation of Pacific saury.

A vector sum analysis method for stability evolution of expansive soil slope considering shear zone damage softening

Slope stability analysis is a classical mechanical problem in geotechnical engineering and engineering geology.It is of great significance to study the stability evolution of expansive soil slopes for engineering construction in expansive soil areas.Most of the existing studies evaluate the slope stability by analyzing the limit equilibrium state of the slope,and the analysis method for the stability evolution considering the damage softening of the shear zone is lacking.In this study,the large deformation shear mechanical behavior of expansive soil was investigated by ring shear test.The damage softening characteristic of expansive soil in the shear zone was analyzed,and a shear damage model reflecting the damage softening behavior of expansive soil was derived based on the damage theory.Finally,by skillfully combining the vector sum method and the shear damage model,an analysis method for the stability evolution of the expansive soil slope considering the shear zone damage softening was proposed.The results show that the shear zone subjected to large displacement shear deformation exhibits an obvious damage softening phenomenon.The damage variable equation based on the logistic function can be well used to describe the shear damage characteristics of expansive soil,and the proposed shear damage model is in good agreement with the ring shear test results.The vector sum method considering the damage softening behavior of the shear zone can be well applied to analyze the stability evolution characteristics of the expansive soil slope.The stability factor of the expansive soil slope decreases with the increase of shear displacement,showing an obvious progressive failure behavior.

滚子与内圈打滑行为诱导的振动特性

针对滚子打滑试验研究困难的问题,通过分析滚子-内圈运动副的相对运动关系得出运动副振动特征频率的计算公式,在此基础上开展打滑试验,提取滚子纯滚动、打滑状态下的振动信号并采用短时傅里叶变换进行时频域分析,结果表明:滚子打滑会诱发一定的振动响应,其频率与滚子、内圈的转动频率相关,理论计算结果与试验结果较为吻合,可用于测算滚子打滑程度;滚子由纯滚动状态转变为打滑状态或由打滑状态转变为纯滚动状态时,纵向、切向振动的幅值均会发生突变,切向振动信号占主要成分且幅值更大。

油罐车自主加注臂密封圈响应面优化及分析

为了提高油罐车自主加注臂前端快接装置的密封性能,设计了一种内胀式橡胶密封圈,并结合响应面法和有限元法对密封圈进行了优化和分析。首先,基于有限元软件ANSYS Workbench对密封圈进行建模和仿真,研究了密封圈的倒圆半径、厚度和压缩量对密封圈性能的影响;然后,将密封圈与管壁的接触面积、接触压力和所受等效应力作为优化目标,利用Design⁃Expert软件建立了密封结构的优化模型,并通过多目标优化获得最优设计方案;最后,进行了密封圈优化前后的性能对比和分析。数值测试表明,在最大3 MPa介质压力下,优化后密封圈的接触压力提升了1.3 MPa,有效接触面积更大,且接触带更加集中,有利于实现快接装置和油罐车加注口的有效密封,同时等效应力降低了4.3%,有助于延长密封圈的使用寿命。

超高压高低温条件下节流阀Y形圈的影响因素分析

为研究天然气设备中节流阀的Y形密封圈在超高压、高低温工况下的影响因素,选择PTFE及其4种改性材料作为密封材料,研究唇口过盈量、唇前角、唇后角对Y形密封圈静密封性能的影响。结果表明:Y形密封圈最大von Mises应力随唇口过盈量增加而减小,随唇前角和唇后角的增大先增加后减小;内唇最大接触应力随唇口过盈量、唇后角的增加而增大,随唇前角的增加先增大后减小。选取密封圈宽度、基体高度、唇尖高度、唇前角、唇后角5个参数,采用ISIGHT软件对各参数进行灵敏度分析。结果表明:密封圈宽度及基体高度对Y形密封圈最大Mises应力及内唇接触应力影响最大。通过多岛遗传算法获得密封圈的优化尺寸,通过试验验证理论设计结果。

基于有限元分析的液压缸密封圈磨损分析

液压缸密封圈磨损原因较多,难以通过肉眼直观观察,很难找到直接原因,提出基于有限元的液压缸密封圈磨损量分析方法。基于液压缸密封圈几何模型、材料模型和物理模型,分析了橡胶密封圈在应力和应变上的非线性,通过定义应变密度函数,构建了液压缸密封圈的有限元模型。根据液压缸活塞的密封结构,分析了液压缸活塞的运动特点,利用Archard模型描述密封圈的外观特征变化,通过计算密封圈接触面上任意一点的磨损深度,分析液压缸密封圈的磨损量。试验结果表明,所研究方法可以对液压缸密封圈的裂纹深度与裂纹扩展角度进行有效分析,两项指标的试验分析与实测结果基本一致,裂纹深度的试验分析误差最大值仅为0.002 mm。方法有助于提高液压缸设计的密封可靠性。

自然驾驶状态下城市地下环道驾驶人心理负荷研究

为探究城市地下环道驾驶人心理负荷特性,组织驾驶人自然驾驶试验,使用生理仪获取自然驾驶状态下驾驶人心电信号数据。以驾驶人心率、心率增长率和心率变异性指标为关键变量,基于因子分析法构建心理负荷量化模型,揭示地下环道平曲线半径、曲线类型、出入口以及熟练程度对驾驶人心理负荷的影响。研究表明:心率指标和心率变异性指标分别与地下环道平曲线半径呈负相关和正相关关系;驾驶人心理负荷与平曲线半径呈负相关,在相同半径条件下,连续曲线场景下的心理负荷显著高于单个曲线场景,且连续曲线间负荷累积作用超过单一曲线半径对驾驶人心理负荷的影响;入口段驾驶人心理负荷比出口段高21.39%;非熟练驾驶人心理负荷比熟练驾驶人高30.75%;建议在城市地下环道出入口和曲率变化区段增设视线诱导设施,设计车速为20~40 km·h^(-1)时,平曲线半径不宜小于30 m。

装配式水泥路面夹环连接式传力杆接缝设计及验证

面向可拆卸装配式水泥路面,提出了一种夹环连接式传力杆接缝,在阐述其特征和基本参数的基础上,选取挠度传荷系数和弯沉差作为指标,使用有限元方法分析了下开口槽、传力杆、夹环构件等参数对夹环连接式传力杆接缝传荷能力的影响,同时分析了夹环连接式传力杆接缝的构件及界面应力的变化规律,得到了合理的接缝参数;此外,通过室内足尺试验评价了夹环连接式传力杆接缝的传荷性能。结果表明,提出的夹环连接式传力杆接缝的传荷能力满足要求,具有一定的工程应用价值。

双作用液环压缩机壳体型线响应面分析及多目标优化

为探究双作用液环压缩机壳体型线对其内流场及性能的影响机理,采用DFFD参数化方法对多级双作用液环压缩机椭圆形壳体型线进行响应面优化分析,并结合NSGA-II多目标优化方法对吸排气区壳体型线进行协同优化。采用VOF多相流模型对该液环压缩机全流域进行非定常计算,双作用液环泵内相态场、压力场基本呈径向对称分布,吸排气区域及叶轮壳体内流场与单作用液环泵分布规律基本一致,随着级数增大液环内的气相区域逐渐减小。响应面结果表明吸气量的大小主要取决于吸气口始端和末端的壳体型线,当R_(A)值趋于0水平,R_(B)处于低水平时,吸气量趋于最大值。轴功率主要受吸、排气口始端位置壳体型线影响,R_(A),R_(C)值越小,轴功率越小。效率的大小主要取决于吸气口始端和末端的壳体型线,且R_(A)值越大,R_(B)值越小,效率越高。在额定出口压比条件下,以吸气量和效率作为优化目标对液环压缩机进行NSGA-II多目标优化,获得其Pareto前沿的最优效率设计J和和最优流量设计K,J方案流量和效率分别高于原方案1.40%和2.53%,K方案流量和效率分别高于原方案16.4%和0.61%。

经导管二尖瓣置换术与二次手术二尖瓣置换术疗效对比的荟萃分析

目的比较经导管二尖瓣置换术(TMVR)与二次手术二尖瓣置换术(redo SMVR)对二尖瓣生物瓣衰败或成形环失效患者的疗效。方法计算机检索PubMed、The Cochrane Library、Web of Science、Embase、中国知网(CNKI)、维普(VIP)、万方和中国生物医学文献数据库(CBM),检索时限为建库至2023年8月,检索有关TMVR对比redo SMVR对二尖瓣生物瓣衰败或成形环失效患者临床疗效的随机对照试验和队列研究。按照纳入与排除标准筛选文献、提取资料和评价纳入研究质量,采用RevMan 5.3和Stata 14.0软件进行荟萃分析。结果最终纳入13项队列研究,共计14226例患者,其中TMVR患者3379例,redo SMVR患者10847例。荟萃分析结果显示,TMVR患者的术后院内死亡率(OR=0.76,95%CI:0.63~0.90,P=0.002)、院内脑血管事件(OR=0.48,95%CI:0.36~0.63,P<0.001)、院内出血事件(OR=0.24,95%CI:0.18~0.32,P<0.001)、院内急性肾损伤(OR=0.52,95%CI:0.45~0.60,P<0.001)、永久起搏器植入(OR=0.25,95%CI:0.18~0.35,P<0.001)、院内心原性休克(OR=0.49,95%CI:0.34~0.72,P<0.001)、主动脉内球囊反搏(OR=0.41,95%CI:0.19~0.91,P=0.030)、新发心房颤动(OR=0.22,95%CI:0.07~0.74,P=0.010)、手术时间(WMD=-225.88,95%CI:-283.56~-168.19,P<0.001)、重症监护室时间(WMD=-2.02,95%CI:-2.32~-1.72,P<0.001)、住院时间(WMD=-5.97,95%CI:-7.87~-4.06,P<0.001)均小于redo SMVR患者,而TMVR患者的1年二尖瓣平均跨瓣压(WMD=1.30,95%CI:0.76~1.84,P<0.001)高于redo SMVR患者,且TMVR和redo SMVR患者术后1年死亡率(OR=1.06,95%CI:0.70~1.61,P=0.770)、2年死亡率(OR=1.90,95%CI:0.98~3.66,P=0.060)比较,差异均无统计学意义。结论TMVR与redo SMVR相比,短期安全性更高,早期并发症较少,术后恢复更快,但术后1、2年死亡率无明显差异。

骨科机器人辅助与徒手经皮骶髂螺钉固定治疗骨盆后环骨折比较的Meta分析

目的:经皮骶髂螺钉内固定已经成为治疗骨盆后环骨折的主要手术方式,然而徒手闭合操作对术者经验要求较高,且反复透视增加患者和医务人员辐射危害。文章通过Meta分析方法比较机器人辅助与徒手经皮骶髂螺钉置入治疗骨盆后环骨折临床疗效的差异。方法:计算机检索中国知网、万方数据库、维普数据库、中国生物医学文献数据库、PubMed、Embase、Cochrane Library及ClinicalTrials.gov等数据库,检索时限均从各数据库建库到2022年12月。搜集国内外关于对比研究机器人辅助与徒手经皮骶髂螺钉置入治疗骨盆后环骨折临床疗效的文献,由2名研究者分别根据纳入和排除标准独立筛选并提取文献数据。采用Cochrane风险评估标准评价随机对照试验质量,采用纽卡斯尔-渥太华量表对纳入队列研究的质量进行评估。使用RevMan 5.4软件对纳入指标进行Meta分析,结局指标包括手术时间、术中出血量、透视时间、透视频率、钻孔次数、Majeed术后功能评分、Matta骨折复位优良率、Gras螺钉位置优良率、骨折愈合时间及术后并发症。结果:①共纳入13篇文献,2篇为随机对照试验,均提及随机方法;11篇为非随机对照研究,根据纽卡斯尔-渥太华量表进行文献质量评价,1篇8分,9篇7分,1篇6分,文献质量较好;共纳入748例患者,其中机器人组430例,徒手组318例。②Meta分析结果显示,机器人辅助组手术时间(MD=-28.30,95%CI:-40.20至-16.40)、术中出血量(MD=-6.36,95%CI:-10.06至-2.66)、术中透视时间(MD=-12.13,95%CI:-19.54至-4.72)、术中透视频率(MD=-17.39,95%CI:-29.00至-5.78)、术中导针钻孔次数(SMD=-9.50,95%CI:-14.27至-4.73)和Gras螺钉位置优良率(OR=8.65,95%CI:3.26-22.92)均明显优于徒手组(P<0.05);③机器人辅助组可显著降低术后总体并发症发生率(OR=0.10,95%CI:0.02-0.48,P<0.05);④两组骨折愈合时间(MD=-0.08,95%CI:-0.21,0.06)、Matta骨折复位优良率(OR=2.06,95%CI:0.97-4.39)、Majeed功能评分(MD=0.91,95%CI:-0.31-2.13)比较差异无显著性意义(P>0.05)。结论:与徒手骶髂关节置钉相比,机器人辅助可缩短手术时间,降低术中出血量,减少患者和医务人员辐射伤害,提高螺钉位置优良率,降低患者术后总体并发症发生率,但对骨折复位质量、骨折愈合时间及术后功能无显著改善。未来仍需更多大样本、多中心、高质量的随机对照试验加以验证。

一种稳健空间圆拟合方法及其在地铁洞门环检测中的应用

空间圆拟合在点云数据处理、地铁建设、工业检测中应用广泛,但存在计算步骤繁琐、拟合精度易受异常值影响等不足。针对这些问题,提出一种基于结合改进的主成分分析和罗德里格投影的空间圆拟合方法。首先提出改进的主成分分析法在拟合空间圆所在最佳平面的同时也可以剔除测量中的粗差,该剔除粗差步骤简单、高效,也提升了算法稳健性;接着利用罗德里格投影将三维坐标投影到拟合的平面上进行平面圆的拟合,拟合后再投影至三维坐标系,该步骤进一步提高了算法便捷性;最后利用深圳某地铁车站洞门钢环实际测量数据和几种常见的空间圆拟合算法进行对比实验,分析改进算法的普适性和剔除粗差的能力。实验结果表明,提出的空间圆拟合方法拟合结果可靠,能够有效地剔除观测带来的粗差,提升空间圆的拟合精度和工作效率。在有粗差的情况下拟合的平均圆度为4.8 mm,较对比方法拟合平均圆度提高约50%。

基于伺服液压缸X形密封圈的数值模拟

针对伺服液压系统中的执行元件伺服液压缸活塞中的X形密封圈,采用有限元分析软件ANSYS建立其二维轴对称有限元模型,研究X形密封圈在沟槽圆弧半径、流体压力、初始压缩率不同参数的条件下,对Von Mises应力、主接触面最大接触压力大小的影响。结果表明:内行程时沟槽圆弧半径为2.6 mm时密封性能最佳,外行程时沟槽圆弧半径为2.2 mm时密封性能最佳;X形密封圈在流体压力为10~20 MPa的范围内密封性能逐渐变差;初始压缩率为5%~15%时密封性能逐渐变好。

基于ANSYS水环真空泵转子静力学和模态分析

水环真空泵具有构造简单、等温压缩、方便使用维修等特点,特别适合抽吸和压缩易燃易爆气体。转子部件在水环真空泵的稳定运行中发挥关键作用,其设计强度直接影响着产品的质量和寿命。通过ANSYS有限元分析软件对转子部件进行了静力学分析和模态分析。结果表明:水环真空泵泵轴和叶轮最大变形量均未超过材料允许的变形量。通过模态分析可知水环真空泵工作转速远低于转子系统的一阶临界转速,系统不会发生共振。研究验证了水环真空泵的工作可靠性,为转子部件以及产品整体结构优化设计提供了理论依据。