Buckling analysis of the shell of a refuge chamber in a coal mine under uniform axial compression

A stiffened cylindrical shell is normally used in refuge chambers of a coal mine. Based on the method of application and shape characteristics of a refuge chamber, we simplified its shell as an orthotropic cylinder. The basic buckling equation of the stiffened cylindrical shell under uniform axial compression was deduced by using a Donnell function. The factors affecting its buckling capacity were studied by theoretical analysis and numerical calculations. The results reveal that the torsional rigidity of the longitudinal stiffener had little effect on the buckling capacity of the shell and that the critical load of an externally stiffened cylindrical shell is higher than that of an internally stiffened cylindrical shell.

Effect of axial length and anterior chamber depth on the peripheral refraction profile

AIM:To evaluate the effect of axial length(AL)and anterior chamber depth(ACD)on peripheral refractive profile in myopic patients compared to emmetropic participants.METHODS:This cross-sectional study was conducted in right eyes of 58 participants of whom 38 were emmetropic and 20 were myopic.Central and peripheral refraction were measured at 10°,20°,and 30°eccentricities in nasal and temporal fields using an open-field autorefractor.The Lenstar LS900 was used to measure ACD and AL.The participants were divided into three groups of short(<22.5 mm),normal(22.5-24.5 mm),and long eye(>24.5 mm)according to AL and three groups of low ACD(<3.00 mm),normal ACD(3.00-3.60 mm),and high ACD(>3.60 mm)according to ACD.RESULTS:The mean age of the participants was 22.26±3.09 y(range 18-30 y).The peripheral mean spherical refractive error showed a hypermetropic shift in myopic and emmetropic groups although this shift was more pronounced in the myopic group.The results showed significant changes in the spherical equivalent,J0,and J45 astigmatism in all gazes with an increase in eccentricity(P<0.001).The pattern of refractive error changes was more noticeable in long and short eyes versus normal AL eyes.Moreover,the pattern of peripheral refractive changes was much more prominent in the high ACD group versus the normal ACD group and in the normal ACD group versus the low ACD group.CONCLUSION:Peripheral refraction changes are greater in participants with AL values outside the normal range and deeper ACD values compared to participants with normal AL and ACD.

Axial length,vitreoretinal pathology,and anterior chamber depth can predict postoperative refractive outcomes in phacovitrectomy/silicone oil removal

AIM:To evaluate the postoperative refractive prediction error(PE)and determine the factors that af fect the refractive outcomes of combined pars plana vitrectomy(PPV)or silicone oil removal(SOR)with cataract surgery.METHODS:The study is a retrospective,case-series study.Totally 301 eyes of 301 patients undergoing combined PPV/SOR with cataract surgery were enrolled.Eligible individuals were separated into four groups according to their preoperative diagnoses:silicone oil-filled eyes after PPV(group 1),epiretinal membrane(group 2),macular hole(group 3),and primary retinal detachment(RD;group 4).The variables af fecting postoperative refractive outcomes were analyzed,including age,gender,preoperative best-corrected visual acuity(BCVA),axial length(AL),keratometry average,anterior chamber depth(ACD),intraocular tamponade,and vitreoretinal pathology.The outcome measurements include the mean refractive PE and the proportions of eyes with a PE within±0.50 diopter(D)and±1.00 D.RESULTS:For all patients,the mean PE was-0.04±1.17 D,and 50.17%of patients(eyes)had a PE within±0.50 D.There was a significant difference in refractive outcomes among the four groups(P=0.028),with RD(group 4)showing the least favorable refractive outcome.In multivariate regression analysis,only AL,vitreoretinal pathology,and ACD were strongly associated with PE(all P<0.01).Univariate analysis revealed that longer eyes(AL>26 mm)and a deeper ACD were correlated with hyperopic PE,and shorter eyes(AL<26 mm)and a shallower ACD were correlated with myopic PE.CONCLUSION:RD patients have the least favorable refractive outcome.AL,vitreoretinal pathology,and ACD are strongly associated with PE in the combined surgery.These three factors affect refractive outcomes and thus can be used to predict a better postoperative refractive outcome in clinical practice.

Axial length and anterior chamber indices in elderly population: Tehran Geriatric Eye Study

AIM:To determine the normative distribution of axial length(AL),anterior chamber depth(ACD),anterior chamber volume(ACV),anterior chamber angle(ACA),and some of their associated factors in subjects aged 60 and over.METHODS:In this cross-sectional study,160 clusters were sampled using multi-stage cluster sampling in Tehran,Iran.After a preliminary interview,the participants underwent optometric examinations including visual acuity and refraction measurement followed by slit lamp biomicroscopy.Finally,ocular imaging was done using the Pentacam AXL to measure AL,ACD,ACV,and ACA.RESULTS:A total of 4519 eyes of 2436 participants were evaluated,of whom 58.0%(n=1412)were female.The mean age of the subjects was 67.32±6.05y(range:60-95y).The mean AL,ACD,ACV,and ACA was 23.22 mm(23.18-23.27 mm),2.61 mm(2.59-2.62 mm),126.56 mm3(125.08-128.04 mm3),and 30.61°(30.3°-30.92°),respectively.In the multivariable model,after adjusting for the effect of both eyes,the longest and shortest AL was seen in myopic and hyperopic subjects,respectively.AL,ACD,ACV and ACA were significantly larger in men compared to women(P<0.001).Except ACA,other evaluated parameters showed an inverse correlation with age(P<0.001),however,this correlation was insignificant for AL(P=0.623).CONCLUSION:Normative value of AL,and other biometric parameters are specific for each ethnicity,age and sex group.Any alteration in these parameters and their effect on refraction should be considered in this age group,especially in case of cataract surgery.

Distribution of Axial Length, Anterior Chamber Depth and Lens Thickness of Pre-Operative Cataract Patients in Indonesian Population

Purpose: Biometry measurement of pre-operative cataract patients plays a major role in calculating intraocular lens power. This study aimed to review and determine the distribution of biometry components, such as axial length (AL), anterior chamber depth (ACD), and lens thickness (LT) of pre-operative cataract patient in Indonesian population. Methods: A cross-sectional study data were obtained from 2015-2018 cataract surgery at Prima Husada Citra Hospital, Surabaya, East Java, Indonesia. A total of 1295 eyes with cataract was included in the study based on their medical record. We analyzed the data using descriptive analysis and correlated each variable using the Spearman’s Rho analysis. Results: Mean AL, LT and ACD was 23.81 ± 1.46 mm, 4.49 ± 0.55 mm, 3.25 ± 0.70 mm respectively. Male has longer AL and deeper ACD with (p < 0.001), while LT was found thicker in female (p = 0.005). The increase of AL was accompanied by ACD (r = 0.457;p < 0.001) and a thinner LT (r = -0.101;p < 0.001). Conclusions: LT is increased with age while AL and ACD are shortened with age. There was a positive correlation between AL and ACD, but an inverse correlation between AL and LT.

Associations of lens thickness and axial length with outcomes of laser peripheral iridotomy

AIM:To investigate the association of axial length(AL),lens thickness(LT),and lens vault(LV)with postoperative anterior chamber angle metrics after laser peripheral iridotomy(LPI).METHODS:Prospective observational study of 69 patients(97 eyes)were diagnosed as primary angle-closure suspect(PACS),primary angle closure(PAC)or primary angle-closure glaucoma(PACG).AL,LT,anterior central chamber depth(ACD),angle opening distance(AOD),trabecular iris angle(TIA),and angle recess area(ARA)were measured before and 1 wk after LPI.The association between AL,LT,LV with ACD,AOD,TIA,ARA were analyzed by comparing the differences between preoperative and postoperative measurements for anterior segment biometric parameters.RESULTS:ACD,AOD,TIA,and ARA were significantly increased after LPI(all P<0.05).Greater LT was significantly associated with greater postoperative increases in ACD,AOD,TIA,and ARA(all P<0.05).AL was not significantly associated with changes of anterior segment biometric parameters.Greater LV was significantly associated with greater postoperative increases in ACD,AOD,and TIA(all P<0.05),but was not significantly associated with changes of ARA.CONCLUSION:Greater baseline LT and LV measurements are associated with greater increases in anterior segment biometric parameters after laser peripheral iridotomy.AL are not associated with the change of anterior segment biometric parameters.

Ultrasonic Evaluation of the Lens Thickness to Axial Length Factor in Primary Closure Angle Glaucoma

Ultrasonic biometry was done in 232 normal eyes and 138 eyes with primary angle closure glaucoma (ACG), using Ultrascan Digital B System IV (10 MHz). The ratio between the lens thickness and the axial length (lens thickness to axial length factor, LAF) was evaluated as a biometric index for assessing the eye with primary ACG in Chinese. LAF of 2.00 was found to be ideal point of demarcation between ACG and normal eyes (i.e., lens thickness equals to 1/5 of axial length). It appears that LAF is helpful i...

燃气轮机轴向贫燃分级燃烧技术进展

在碳减排背景下,燃气轮机燃烧室需要在出口温度不断提高的同时控制NO_(x)排放、提高功率调节范围和燃料适应性。为了应对以上挑战,燃气轮机厂商正在发展轴向分级燃烧技术。本文介绍了轴向分级燃烧原理,分析了轴向分级参数、交叉射流火焰形态、喷嘴结构和燃料种类对污染物排放和燃烧不稳定性的影响。现有研究表明,降低一级燃烧室当量比、增强二级燃烧室的掺混均匀性能够降低污染物排放;轴向分级燃烧室的热声振荡特性复杂,合理选取分级参数能够抑制振荡。轴向分级燃烧室的减排效益和工况调节能力已经在商业运行中得到验证。基于目前研究现状,展望了轴向分级燃烧技术的关键问题和未来研究方向。

基于中间气压罐和罐前逆止阀的浮船泵站水锤防护

以云南省元谋县金沙江光伏提水工程的第一级浮船泵站供水系统为例,开展了浮船泵站水锤防护的研究。在参考相关设计规范的基础上,确定了停泵水锤防护标准;通过比较不同水源水位和停泵台数对过渡过程的影响,确定水锤防护的控制工况为水源水位最低、运行机组全部停泵的工况;根据管道沿线地形和浮船泵站的特点,在分析泵出口阀关闭程序、中间气压罐防护效果、罐前逆止阀作用的基础上,提出了“泵出口轴流式逆止阀+中间气压罐+罐前逆止阀”的水锤防护方案。该方案通过泵出口轴流式逆止阀完全防止机组倒转,通过中间气压罐控制管线中的正负水锤压力,通过罐前逆止阀防止倒泄水流对浮船和摇臂联络管的冲击。该防护措施对类似工程有较好的参考意义。

Insight into small eyes: a practical description from phenotypes presentations to the management

This narrative review aimed to have an algorithmic approach to microphthalmos by a systematic search.The definition can be related to a number of special phenotypes.In the more challenging cases of complex microphthalmos,relative anterior microphthalmos,and nanophthalmos,the surgeon can approach these cases more safely if they have a deep understanding of the anatomical variations and ideal formulae for intraocular lens computation and knows how to avoid intra-and post-operative complications.In this article,we review the criteria by which we recognize and describe pre-,intra-,and post-operative considerations,as well as discuss the ideal intraocular lenses for microphthalmos,given the intricate varieties of small eye phenotypes.

白内障手术候选者的眼部生物特征参数分析

目的:分析白内障手术候选人的眼部生物特征参数。方法:横断面研究。纳入2017-01/2021-09就诊于伊朗德黑兰Farabi眼科医院的4607例白内障患者(4607眼)。使用IOLMaster 700评估眼轴(AL)、角膜曲率(Kf、Ks、Km)、前房深度(ACD)。根据AL分为22 mm<AL、22 mm≤AL≤25 mm和AL>25 mm组,根据ACD分为3.00 mm<ACD、3.00 mm≤ACD≤3.60 mm、ACD>3.60 mm组。结果:患者平均年龄60.3±14.1(8-95)岁,女2243例(48.69%),男2364例(51.31%)。AL、ACD和平均角膜曲率范围分别为23.1-23.4 mm、3.1-3.2 mm和44.50-45.00 D。AL>25 mm组ACD平均值显著高于22 mm≤AL≤25 mm组和22 mm<AL组(P<0.001)。ACD>3.60 mm组的平均AL显著高于3.00 mm<ACD组和3.00 mm≤ACD≤3.60 mm组(P<0.001)。3.00 mm<ACD组和AL>25 mm组的Kf、Ks、Km均值显著高于ACD>3.60 mm组和22 mm<AL组(P<0.001)。结论:AL长的白内障患者ACD更深,角膜更平坦;AL短的患者ACD较浅,角膜较陡。此外,深ACD患者的AL较长,角膜较平坦,浅ACD患者的AL较低,角膜较陡。

某型F级轴向分级燃烧室的全温全压试验研究

在全温全压条件下对自主研发的F级燃气轮机轴向分级燃烧室进行了燃烧试验研究,以探究设计点工况下燃烧室的压力损失、出口温度分布、火焰筒壁面温度、污染物排放、燃烧效率和热声稳定性等燃烧性能。结果表明:在设计点工况下,燃烧室总压损失系数为5.4%;燃烧室出口温度分布系数为0.06,燃烧室出口径向温度分布系数为0.03;燃烧室火焰筒壁面温度低于850℃;NO_(x)摩尔分数维持在1.9×10^(-5),CO和未燃碳氢(UHC)排放基本为0,燃烧效率维持在99.99%以上;压力脉动各特征频率对应幅值均低于3 kPa,表明燃烧室热声状态稳定。

中心性浆液性脉络膜视网膜病变眼部特征的研究进展

中心性浆液性脉络膜视网膜病变(CSC)是一种以特发性浆液性视网膜脱离(SRD)为特征的脉络膜视网膜疾病,伴有一处或多处视网膜色素上皮脱离(PED)或病变,具有特征性的眼球结构改变。CSC被归类为厚脉络膜相关疾病(PSD),近年来进一步发现主要为Haller层增厚。最近的研究重点关注了CSC患者的厚巩膜特征,阐述了其与脉络膜循环的密切关系,并提出CSC可能与葡萄膜渗漏综合征(UES)具有相似的发病机制。此外,CSC还具有短眼轴、远视性屈光不正、浅前房等特征,表明CSC不仅是眼球后极部的病变,而且累及全眼球。本文对CSC眼部特征的最新进展进行了综述,为进一步探究CSC发病机制提供新思路。

Shuttle配流方案对轴向柱塞泵关键性能的研究

针对轴向柱塞泵配流过程中产生的节流损失、压力冲击等问题,创新设计基于Shuttle配流方案的柱塞泵模型,建立基于Shuttle配流方案的斜盘式轴向柱塞泵AMESim仿真模型。通过与原配流方案对比,验证了Shuttle配流方案中的无节流槽配流盘和可变容积缸体,可以使得柱塞腔在配流中实现更柔和的压缩和膨胀,压力超调更小,同时不存在配流节流损失。仿真结果与2022年INNAS公司公布了Shuttle技术的试验效果一致。

浮动式配流盘柱塞泵马达系统动力学建模及特性研究

浮动式配流盘设计从根本上解决了轴向柱塞泵/马达高转速下缸体倾覆的难题,契合了其高速化的发展趋势,在近年来得到重视。然而,针对浮动式配流盘柱塞泵马达系统所特有的结构,仍然缺乏系统级的动力学建模及动态特性研究,限制了浮动式配流盘柱塞泵马达产品的设计。本文针对浮动式配流盘柱塞泵马达系统,建立了考虑其详细结构特征的完全参数化描述的系统动力学模型,着重研究了其高压油路以及辅助液压腔油液压力的动态变化规律,并通过台架试验验证了模型的正确性。研究结果表明,高压油路表现出“瞬降缓升”的“锯齿形”压力脉动特征,且脉动剧烈。在泵转速1 000 r/min,高压油路平均压力20、40 MPa两个压力等级下,脉动幅值分别高达±1.5和±3 MPa。辅助液压腔油液压力呈现“快速跟随、缓慢下降”的动态变化规律,即辅助液压腔一旦与高速旋转的柱塞腔接通,其油液压力几乎立即无衰减、无滞后地跟随柱塞腔压力变化。而当与柱塞腔脱离之后,其还能很好地维持住腔内压力。

口环间隙对屏蔽泵性能影响的数值研究

口环结构对屏蔽泵水动力特性的影响显著。为了降低屏蔽泵转子轴向力进而延长其使用寿命,采用SST k-ω模型模拟了不同口环形式(矩形、锯齿形、梯形、倒梯形和圆形口环)的屏蔽泵内部流场,分析其对口环压力、后泵腔压力、轴向力和泄漏量的影响,研究不同的口环形式对屏蔽泵运行特性的影响规律。结果表明:后口环间隙宽度增加时,泵水力性能下降,同时会使轴向力由负向正递增,因此存在最佳间隙宽度;后口环结构形式对屏蔽泵水力性能影响不明显,而前口环结构改变可有效提高泵效率,最大提高了1.3%,而对轴向力影响不明显;采用锯齿形后口环时,泄漏量较原模型约降低了30%,可有效地减少泄漏。

藏族年龄相关性白内障患者眼球生物学参数特征分析

目的:比较藏族与汉族年龄相关性白内障患者眼球生物学参数的差异,分析藏族患者眼球生物学参数的分布特征。方法:回顾性队列研究。收集2019-01/2020-12就诊于我院的年龄相关性白内障患者661例1 030眼,其中藏族患者483例739眼,汉族患者178例291眼。术前所有患者均采用IOL Master 500测量眼轴长度、前房深度、角膜曲率、散光及散光轴向。结果:藏族年龄相关性白内障患者眼轴长度为23.33(22.81,23.86)mm,前房深度为3.04(2.79,3.30)mm,散光度为0.73(0.47,1.07)D,平均角膜曲率为43.89±1.35 D,较汉族患者眼轴短,角膜曲率小(均P<0.05)。藏族患者的年龄与眼轴长度和前房深度均呈负相关,而与平均角膜曲率呈正相关(均P<0.05)。藏族患者中男性患者较女性患者眼轴更长、前房更深、角膜更平坦(均P<0.05)。结论:藏族与汉族年龄相关性白内障患者的眼球生物学参数存在差异,不同年龄和性别藏族患者眼球生物学参数的分布有所变化。

掺混腔室对透平性能影响的多工况对比研究

基于某变转速透平小机,采用数值模拟方法,研究了阀门全开和额定工况下,掺混腔室轴向长度对机组性能的影响,结果表明:随着掺混腔室轴向长度增加,级段效率逐渐提高,且额定工况效率增加的速度更快。掺混腔室轴向长度主要影响调节级(包含进汽室和掺混腔室)和第2级的性能。阀门全开工况下,随着掺混腔室轴向长度增加,调节级动叶域损失逐渐增大,但掺混腔室出口汽流均匀性得到改善,因此调节级效率逐渐降低,第2级效率逐渐提高。额定工况下,随着掺混腔室轴向长度增加,调节级动叶域损失逐渐减小,掺混腔室出口汽流均匀性得到改善,因此调节级和第2级效率均逐渐提高。

IOLMaster与接触式A超测量前房深度和眼轴长度的比较研究(英文)

目的:比较IOLMaster与接触式A超测量中央前房深度和眼轴长度的差异,以评价两者在人工晶状体度数计算参数测量中的准确性。方法:2006-10/2007-01在我院眼科施行白内障超声乳化摘除手术联合人工晶状体植入的患者121例(137眼),分别用IOLMaster与接触式A超于术前测量中央前房深度和眼轴长度。结果:IOLMaster与接触式A超测量中央前房深度分别为(2.94±0.49)mm,(2.58±0.51)mm,配对t检验,两者的差值为(0.36±0.30)mm(P<0.001),差异有显著性,相关系数r=0.823(P<0.001)。测量眼轴长度分别为(24.37±3.04)mm,(23.81±2.83)mm,配对t检验,两者差值为(0.56±0.34)mm(P<0.001),差异有显著性,相关系数r=0.996(P<0.001)。结论:IOLMaster与接触式A超均可用于前房深度和眼轴长度的测量,两者的相关性好。但基于光学原理的IOLMaster在准确测量眼轴长度和前房深度的同时,简便、快捷、非接触的特点是A超无法比拟的,并可同时测量出其他相关参数。

IOLMaster、Axis-ⅡA型超声和ODM1000A型眼科超声测量仪测量眼轴长度及前房深度的比较

背景眼轴长度和前房深度是人工晶状体（IOL）度数计算公式中的重要参数。目的对IOLMaster、Axis-ⅡA型超声、ODM1000A型眼科超声测量仪测量的眼轴长度及前房深度进行比较。方法同一操作者分别使用IOLMaster、Axis—UA型超声和ODM1000A型眼科超声测量仪测量48例83眼的眼轴长度及前房深度。结果Axis-ⅡA型超声、ODM1000A型眼科超声测量仪、IOLMaster测得眼轴长度的均值分别为（25．79±0．85）、（25．72±0．82）、（26．00±0．83）Film。Axis-ⅡA型超声比ODM1000A型眼科超声测量仪测得眼轴长度长（0．07±0．35）mm，差异无统计学意义（t=1．711，P=0．091）；IOLMaster比ODM1000A型眼科超声测量仪测得眼轴长度长（0．27±0．29）mm，差异有统计学意义（t=-8．570，P：0．000）；IOLMaster比Axis-ⅡA型超声测得眼轴长度长（0．21±0．32）mm，差异有统计学意义（t=-5．931，P=0．000）。3种检查仪测量眼轴长度结果相互呈正相关（r=0．916、0．938、0．928，P〈0．01）。Axis-ⅡA型超声、ODM1000A型眼科超声测量仪、IOLMaster测得前房深度分别为（3．81±0．21）、（3．84±0．25）、（3．83±0．18）mm。Axis-ⅡA型超声比ODM1000A型眼科超声测量仪测得前房深度值小（0．03±0．17）Film，差异无统计学意义（t=-1．324，P=0．189），IOLMaster比ODM1000A型眼科超声测量仪测得前房深度值小（0．01±0．15）mnl，差异无统计学意义（t=0．815，P=0．417），Axis-ⅡA型超声比IOLMaster测得前房深度值小（0．01±0．12）mm，差异无统计学意义（t=-0．900，P=0．371）。3种检查仪测量的前房深度值相互间均呈高度正相关（r=0．735、0．813、0．823，P〈0．01）。结论ODM1000A型眼科超声测量仪可以准确测量眼轴长度及前房深度，但不能替代10LMaster．