Optical coherence tomography with or without enhanced depth imaging for peripapillary retinal nerve fiber layer and choroidal thickness

AIM：To assess peripapillary retinal nerve fiber layer（RNFL）and choroidal thickness obtained with enhanced depth imaging（EDI）mode compared with those obtained without EDI mode using Heidelberg Spectralis optical coherence tomography（OCT）.METHODS：Fifty eyes of 25 normal healthy subjects and32 eyes of 20 patients with different eye diseases were included in the study.All subjects underwent 3.4 mm diameter peripapillary circular OCT scan centered on the optic disc using both the conventional and the EDI OCT protocols.The visualization of RNFL and choroidoscleral junction was assessed using an ordinal scoring scale.The paired t-test,intraclass correlation coefficient（ICC）,95%limits of agreement（LoA）,and Bland and Altman plots were used to test the agreement of measurements.RESULTS：The visibility score of RNFL obtained with and without EDI was of no significant difference（P=0.532）,the visualization of choroidoscleral junction was better using EDI protocol than conventional protocol（P〈0.001）.Peripapillary RNFL thickness obtained with EDI was slightly thicker than that obtained without EDI（103.25±9.42μm vs 101.87±8.78μm,P=0.010）.The ICC of the two protocols was excellent with the value of 0.867 to 0.924,the 95%LoA of global RNFL thickness was between-10.0 to 7.4μm.Peripapillary choroidal thickness obtained with EDI was slightly thinner than that obtained without EDI（147.23±51.04μm vs 150.90±51.84μm,P〈0.001）.The ICC was also excellent with the value of 0.960 to 0.987,the 95%LoA of global choroidal thickness was between-12.5 to 19.8μm.CONCLUSION：Peripapillary circular OCT scan with or without EDI mode shows comparable results in the measurement of peripapillary RNFL and choroidal thickness.

Effects of monsoon onset vortex on heat budget in the mixed layer of the Bay of Bengal

We investigated the effects of monsoon onset vortex(MOV)on the mixed layer heat budget in the Bay of Bengal(BOB)in spring 2003 using the reanalysis datasets.The results suggest that the solar radiation flux penetrating the mixed layer and the existence of barrier layer are both able to modulate the effects of MOV on the evolution of sea surface temperature(SST)in the BOB.Prior to the formation of BOB MOV,the local SST raised quickly due to mass of solar radiation reaching the sea surface under the clear-sky condition.Meanwhile,since the mixed layer was shallow before the onset of the Asian summer monsoon(ASM),some solar radiation flux could penetrate to directly heat the deeper water,which partly offset the warming effect of shortwave radiation.On the other hand,the in-situ SST started to cool due to the upwelling of cold water when the MOV generated over the BOB,along with the rapidly increased surface wind speed and its resultant deeper mixed layer.As the MOV developed and moved northward,the SST tended to decrease remarkably because of the strong upward surface latent heat flux over the BOB ascribed to the wind-evaporation mechanism.However,the MOV-related precipitation brought more fresh water into the upper ocean to produce a thicker barrier layer,whose thermal barrier effect damped the cooling effect of entrainment upwelling on the decrease tendency of the BOB SST.In other words,the thermal barrier effect could slow down the decreasing trend of the BOB SST even after the onset of ASM,which facilitated the further enhancement of the MOV.

Coupling of the Calculated Freezing and Thawing Front Parameterization in the Earth System Model CAS-ESM

The soil freezing and thawing process affects soil physical properties,such as heat conductivity,heat capacity,and hydraulic conductivity in frozen ground regions,and further affects the processes of soil energy,hydrology,and carbon and nitrogen cycles.In this study,the calculation of freezing and thawing front parameterization was implemented into the earth system model of the Chinese Academy of Sciences(CAS-ESM)and its land component,the Common Land Model(CoLM),to investigate the dynamic change of freezing and thawing fronts and their effects.Our results showed that the developed models could reproduce the soil freezing and thawing process and the dynamic change of freezing and thawing fronts.The regionally averaged value of active layer thickness in the permafrost regions was 1.92 m,and the regionally averaged trend value was 0.35 cm yr–1.The regionally averaged value of maximum freezing depth in the seasonally frozen ground regions was 2.15 m,and the regionally averaged trend value was–0.48 cm yr–1.The active layer thickness increased while the maximum freezing depth decreased year by year.These results contribute to a better understanding of the freezing and thawing cycle process.

Changes in the depths of seasonal freezing and thawing and their effects on vegetation in the Three-River Headwater Region of the Tibetan Plateau

Frozen ground degradation plays an important role in vegetation growth and activity in high-altitude cold regions.This study estimated the spatiotemporal variations in the active layer thickness(ALT)of the permafrost region and the soil freeze depth(SFD)in the seasonally frozen ground region across the Three Rivers Source Region(TRSR)from 1980 to 2014 using the Stefan equation,and differentiated the effects of these variations on alpine vegetation in these two regions.The results showed that the average ALT from 1980 to 2014 increased by23.01 cm/10 a,while the average SFD decreased by 3.41 cm/10 a,and both changed intensively in the transitional zone between the seasonally frozen ground and permafrost.From 1982-2014,the increase in the normalized difference vegetation index(NDVI)and the advancement of the start of the vegetation growing season(SOS)in the seasonally frozen ground region(0.0078/10 a,1.83 d/10 a)were greater than those in the permafrost region(0.0057/10 a,0.39 d/10 a).The results of the correlation analysis indicated that increases in the ALT and decreases in the SFD in the TRSR could lead to increases in the NDVI and advancement of the SOS.Surface soil moisture played a critical role in vegetation growth in association with the increasing ALT and decreasing SFD.The NDVI for all vegetation types in the TRSR except for alpine vegetation showed an increasing trend that was significantly related to the SFD and ALT.During the study period,the general frozen ground conditions were favorable to vegetation growth,while the average contributions of ALT and SFD to the interannual variation in the NDVI were greater than that of precipitation but less than that of temperature.

Impact toughness of a gradient hardened layer of Cr5Mo1V steel treated by laser shock peening

Laser shock peening（LSP） is a widely used surface treatment technique that can effectively improve the fatigue life and impact toughness of metal parts.Cr5Mo1 V steel exhibits a gradient hardened layer after a LSP process.A new method is proposed to estimate the impact toughness that considers the changing mechanical properties in the gradient hardened layer.Assuming a linearly gradient distribution of impact toughness,the parameters controlling the impact toughness of the gradient hardened layer were given.The influence of laser power densities and the number of laser shots on the impact toughness were investigated.The impact toughness of the laser peened layer improves compared with an untreated specimen,and the impact toughness increases with the laser power densities and decreases with the number of laser shots.Through the fracture morphology analysis by a scanning electron microscope,we established that the Cr5Mo1 V steel was fractured by the cleavage fracture mechanism combined with a few dimples.The increase in the impact toughness of the material after LSP is observed because of the decreased dimension and increased fraction of the cleavage fracture in the gradient hardened layer.

人工缺陷下感应淬火重载铁路车轴损伤容限评价

目的研究不同感应淬火工艺对重载铁路车轴钢试样梯度结构的影响,阐明不同人工缺陷下感应淬火试样的疲劳断裂行为,并评价损伤容限,为重载铁路车轴感应淬火工艺设计和损伤容限评价提供理论基础和评价方法。方法在AAR-CM车轴钢试样表面采用不同感应淬火工艺参数制备不同深度淬硬层,采用X射线测量淬硬层残余应力分布,通过电火花和空气炮在正火态和感应淬火试样表面制备不同尺寸的电火花或冲击损伤,采用疲劳试验机研究损伤试样的弯曲疲劳性能,借助光学显微镜和扫描电镜分析试样的损伤机理和疲劳断裂行为,并对其疲劳性能进行评价。结果在3种工艺下感应淬火试样有效淬硬层深度分别为800、1200、1400μm。在电火花缺口尺寸较小时,感应淬火试样的疲劳强度比正火态试样高出50%。在冲击损伤尺寸较小时,感应淬火试样的疲劳强度比正火态试样高出40%。较小的尺寸冲击损伤对正火态和感应淬火处理试样的疲劳强度无影响。结论感应淬火可提高重载铁路车轴钢试样表面强度,进而提高其耐冲击性能,残余压应力减弱了电火花缺口试样和低速冲击损伤对试样疲劳强度的影响,高速冲击破坏了试样表面完整性,并削弱了残余压应力的作用,试样的疲劳强度急剧降低。文中设计的淬硬层深度对感应淬火试样损伤容限的影响较小。

全球海洋混合层深度和障碍层厚度计算及其时空变化特征分析

基于2002—2019年的Argo温盐数据计算得到海洋混合层深度(MLD)和障碍层厚度(BLT),利用阈值法在计算过程中设置不同的温度阈值ΔT_(1)=0.2℃和ΔT_(2)=0.5℃,并分别利用温度、密度以及由温度和密度计算得到全球海洋的MLD和BLT值,基于此描述不同温度阈值下得到的全球海洋混合层和障碍层分布特征。结果表明:不论阈值是ΔT_(1)还是ΔT_(2),基于温度和密度的计算结果较基于温度参数或密度参数的结果更为可靠。利用温度参数或密度参数计算得到的MLD值,不论是MLDT还是MLDD都能够在一定程度上体现全球海洋MLD的分布特征,两者在赤道附近和低纬度海域结果的一致性较好,在高纬度海域差异较大。基于阈值ΔT_(2)=0.5℃的结果比基于阈值ΔT_(1)=0.2℃的结果与现有MLD数据的相关性更高,但是均方根误差也更大,可能是由于不同海域适合的阈值选择不同,需进一步计算分析。全球海洋BLT较南北半球高纬度海域BLT值更大,BLT值随着纬度的降低而减小,空间分布特征在不同海域均存在明显差异,总体来说BLT随着纬度的降低而减小。

45钢表面硬化层深度的高鲁棒性微磁定量预测方法

考虑多功能微磁检测系统对微磁参量的重复测试性能,研究利用系统对45钢表面硬化层深度进行高鲁棒性定量预测的方法。首先,利用测试数据的变异系数β统计方法,定量评价了系统对41项微磁参量的重复测试能力,结合指标β和微磁参量对硬化层深度的敏感性指标S,对微磁参量进行了筛选;其次,融合多项微磁参量建立了硬化层深度的前馈神经网络定量预测模型,提出了改善模型鲁棒性的建模策略及鲁棒性评价方法;最后,讨论了输入节点逐项剔除和有条件保留规则对模型鲁棒性的影响规律。与传统建模方法相比,利用规则剔除微磁参量项数为8时,模型的MAE均值和MAE值小于5%的模型数量P分别下降约68.8%和增加约150%,表明提出的建模策略可以有效改善仪器在45钢表面硬化层深度定量预测过程中的鲁棒性。

宽厚板轧机用Cr3钢支承辊淬硬层深度的理论预测与实验验证

差温热处理是决定支承辊工作层组织、应力分布和使用性能的关键工序。为精准控制宽厚板轧机用Cr3钢支承辊辊身淬硬层深度以进一步提高其寿命周期内的服役性能,利用ABAQUS有限元模拟软件计算了支承辊在差温热处理过程中的温度场分布,分析了距离辊身不同深度处的温度与显微组织演变,预测了差温处理过程中辊身淬硬层的深度。结果表明:当加热温度达到840℃及以上时,Cr3钢可获得耐磨性较佳的非珠光体组织;Cr3钢支承辊实验件的淬硬层深度达110 mm,表面硬度达到55 HSD以上,且距离表面110 mm深处的硬度降低不大于4 HSD;淬硬层深度的理论预测结果与实测结果吻合较好,可以实现支承辊淬硬层深度的精确控制,指导Cr3钢支承辊差温热处理工艺制定。

上硬下软层状土中锚板抗拔承载特性研究

锚板基础是一类在海工系泊系统中广泛应用的锚固基础,其特点是具有较高的承载力和稳定性。锚板的承载能力是基础设计的重要参考因素,而承载能力与土体的性质密切相关。现有关于锚板承载力的研究多集中在单一均质土层中,而对层状土尤其是上硬下软这类层状土体中的承载特性认识不足。基于数值分析,综合考虑层状土的分层性质,对锚板基础在硬黏-软黏层状土体及砂土-软黏土复合土体中的承载特性展开研究,分析锚板埋深、土层抗剪强度比、层厚比及土体性质等关键因素对锚板周围土体破坏模式和承载力的影响。结果表明:在硬黏-软黏土体中,随着抗剪强度比、层厚比的增加,极限承载力均显著增加;在砂土-软黏土体中,极限承载力同样随着层厚比的增加而增加,当下层软黏土中的锚板破坏进入局部破坏后,层厚比对承载力的影响逐渐减弱。研究可以为上硬下软层状土中锚板基础的承载力确定提供计算方法和理论参考。

考虑桩基极限沉降深度的荷载传递模型的研究

荷载传递法广泛运用于基桩承载力和沉降分析。通过理论公式推导,在传统模型上考虑桩径的影响,并引入沉降计算深度概念,建立考虑桩基极限沉降深度的荷载传递模型,以此分析分层厚度(k)和应力比(η)对沉降计算精度的影响。研究发现:当桩端下土层压缩模量变小时,需要采用更小的分层厚度;应力比的设定对极限沉降深度计算有着明显的影响,若在实际工程应用中主要关注点为桩顶沉降,则根据压缩层压缩模量选取合适的应力比参数,若关注点为极限沉降深度,则尽量减小应力比取值。

高速精密轴承表面硬化及尺寸稳定化工艺研究

利用金相显微镜(OM)、显微硬度计和X射线衍射仪(XRD)等仪器对GCr15轴承钢在不同热处理工艺下的组织特征、硬化层梯度和残余奥氏体含量进行分析研究。结果表明,通过碳氮共渗淬火+(-70℃×2 h)冷处理+220℃×4 h回火热处理可实现轴承零件表面硬度>63 HRC、基体残余奥氏体含量<3%、表面残余奥氏体含量约6%的技术要求,保证零件尺寸精度的同时可避免因残余奥氏体含量过低而导致的轴承接触疲劳寿命下降。通过在原材料中添加微量Mo、V等强碳化物合金元素,并进行马氏体淬火和碳氮共渗两次淬火,基体的平均晶粒度由原来的8级细化至10级以上。

某渡槽槽身侧墙裂缝成因调查研究及分析

渡槽因常年通水可能引发混凝土结构内部钢筋锈蚀膨胀导致混凝土结构裂缝,也可能因常年经受冻融循环产生温度应力而引起裂缝。为此,文中主要通过对渡槽槽身外观质量、混凝土抗压强度、碳化深度、槽身裂缝等方面的调查试验来分析研究渡槽槽身产生裂缝的主要原因,为水利运管单位运行维护提供理论支撑。

S-Zorb装置金属密封球阀内件硬化方法及材料选择

主要介绍应用于S-Zorb催化汽油吸附脱硫装置中金属密封耐磨球阀内件硬化所采用的超音速喷涂和渗硼加工等工艺方法,以及各种方法的硬化层硬度、结合强度和热膨胀系数、硬化层厚度或深度等性能参数。

Durability Analysis and Carbonation Life Prediction of Shajiang River Bridge

The shajiang river bridge on the appearance test, concrete rebound detection, concrete cover depth detection, concrete carbonation depth detection, concrete chlorine ion content detection, and the detection results in statistics and analysis. Based on the bridge of the service the atmospheric environment parameters and testing data, the paper calculates and analyzes the main stress components the carbonation bridge reliability index and remaining life of carbide, assessing the bridge for the service life and reinforcement maintenance and offer the scientific basis.

中国西部土壤冻融起止期和冻结深度及其与气温关系的时空分布特征分析

冻土变化对寒区基础建设、水文、生态等都有重要影响,在全球变暖背景下,探究土壤冻融过程具有重要现实意义。本文基于中国自然地理特征和冻土特性,划分出中国西部地区(以下简称西部地区)作为研究区域,并利用1981年1月至2020年6月ERA-5地表温度、土壤体积水含量和逐月气温数据,分析了近40年中国西部地区土壤冻融状况、活动层厚度和最大冻结深度空间分布,探讨了冻融状态与气温、海拔的相关性。研究结果表明:西部地区冻融起始时间空间分布具有由高海拔地区至低海拔地区冻结推迟、融化提前的特征。高海拔的藏北高原冻结最早,融化最晚,冻结持续时间最久昆仑山脉上零星区域冻结最长可持续300天以上。海拔低且土壤含水量低的西部西北塔里木盆地,冻结最晚,融化最早,融化持续时间最长,塔克拉玛干沙漠区域融化可维持在280天以上。多年冻土活动层厚度基本都超过2.0 m,只有喀喇昆仑山脉附近的区域才有较大范围活动层厚度低于2 m的区域,青藏高原的季节性冻土冻结深度最大,厚度可以达到2 m以上,塔里木盆地冻结深度最浅,厚度在0.6 m以内。1981-2020年间,西部地区冻结起始日推迟,融化起始日提前,开始冻结和完全冻结起始时间分别以0.089 d·a^(-1)和0.061 d·a^(-1)的速率上升。开始融化与完全融化起始时间分别以0.102 d·a^(-1)和0.156 d·a^(-1)的速率下降。在冻结趋势上升,融化趋势下降的情形下,完全融化持续时间以0.256 d·a^(-1)的速率增加了12天左右,完全冻结持续时间以0.164 d·a^(-1)的速率缩短约11天,研究期间,完全融化起始时间在1996年发生突变,开始冻结起始时间与完全融化持续时间在1997年发生突变。西部地区冻融起始时间整体变化趋势一致,局部地区略有差异,黄土高原开始冻结与完全冻结持续时间分别以0.166 d·a^(-1)和0.405 d·a^(-1)的速率下降最快。整个研究期间,开始冻结持续时间和完全冻结持续时间分别缩短7天和16天左右。4个区域的完全融化期持续时间趋势都呈上升趋势。但黄土高原完全融化持续时间以0.435 d·a^(-1)的速率快速上升,在1981-2020年间,增加约17天。西部地区冻融起始时间与年平均气温和海拔存在显著相关性,年平均气温与所有冻融时间的相关性均超过0.79,其中完全融化起始时间与年均气温的负相关高达0.963。气温每升高1.0℃,开始冻结起始时间推迟2.03天,完全冻结起始时间推迟2.12天,开始融化起始时间与完全融化起始时间分别提前5.10天和5.17天。海拔每升高1000 m,开始冻结与完全冻结起始日期分别提前6.1天和4.5天,开始融化与完全融化起始日期分别推迟14.4天和19.9天。本文研究结果揭示了中国西部土壤冻融状况及近年来的变化规律,为中国西部地区寒区生态环境和基础建设提供科学参考。

地铁盾构隧道双线施工对地表沉降影响的预测及分析

结合广州地铁12号线双线隧道工程,采用ABAQUS数值模拟方法,分析不同注浆层厚度、埋深比和隧道间距等因素对工程地质条件的影响,并提出相应施工控制措施。研究发现:注浆层厚度与地面沉降量成反比,0.3m为最佳注浆层厚度。地面侧向沉降量随埋深比的增大呈先增大后减小趋势,这与土的拱形作用有关。当2条并联巷道间距越大,左右巷道地面沉降越大;间距越小时,其相互作用越强,在共同受扰的范围内,沉降变形越大,沉降沟呈倒V形。当2条隧道间隔足够大时,2条隧道间的相互干涉作用被削弱,地面沉降变形被视为2条独立隧道沉降变形叠加,形成W形沉降沟。

某宽厚钢板等离子切割开裂原因

在某宽厚板的等离子切割工序中,其板厚1/2处产生中心裂纹。采用宏观观察、化学成分分析、金相检验、扫描电镜及能谱分析、硬度测试等方法分析该钢板开裂的原因。结果表明:在钢板1/2厚度处存在明显的偏析带,基体和偏析带的显微组织分别为回火马氏体和淬火马氏体,在偏析带中分布有长条状夹杂物,裂纹从夹杂物处萌生并扩展;等离子切割后的淬硬层硬度较大,具有很大的淬硬倾向,在热应力和组织应力的作用下,钢板最终开裂。

SAE J403钢制驻车齿轮淬火层深度超声非线性表征

汽车电子驻车齿轮主要由SAE J403碳素钢制成,在其生产过程中,需要对SAE J403进行高频感应淬火过程,由于材料本身或淬火工艺上的差距,会造成齿轮表面形成不同厚度的淬硬层,从而影响齿轮的材料性能和力学性能。通过超声检测装置完成对不同淬硬层厚度碳素钢的信号采集,对采集的超声信号做频谱分析(快速傅里叶变换),获得超声信号基波幅值和二次谐波幅值计算出评定淬硬层深度的非线性超声系数。结果表明,随着淬硬层深度的增加,碳素钢的非线性系数呈现出不断上升的趋势。由此利用非线性超声系数实现对不同淬硬层厚度的碳素钢深度表征。

双线盾构隧道开挖参数对诱发地表沉降的影响分析

以南昌市轨道交通2号线沈桥站至殷王站盾构区间隧道工程为研究对象,通过ABAQUS有限元软件对注浆层厚度、深径比和2条平行隧道间距离对地表沉降的影响进行了综合探讨。研究发现:注浆层厚度与地表沉降量呈反比关系,最佳注浆层厚度为0.30m;深径比的增加会导致地表横向沉降发生先增加后减少的趋势,与土体的拱效应密切相关;此外,2条平行隧道间距的增大与左右隧道地表沉降量的增加呈正相关,在较小的间距下,隧道相互干扰影响增强,呈现“V”形沉降凹槽,而在较大的间距下,相互干扰影响减弱,呈现“W”形沉降凹槽。