Evolution of microstructure and texture of AZ80 magnesium alloy under hot torsion with constant decreasing temperature rate

Hot torsion tests for AZ80 magnesium alloy were carried out in the temperature range of 380℃-260℃,with a constant decreasing temperature rate of 10℃/s in order to weaken the basal texture and refine the grains.The results indicated that the average grain sizes were refined forming gradient structure with increasing specimen radial position from center(12.2-5.4μm),and that the initial basal texture intensity of the extruded magnesium alloy was weakened from 46.2 to 8.3.Furthermore,the extension twins(ETs)could be disintegrated from the twins forming separated twins with smaller sizes.Interestingly,ETs with the same twin variant intersecting with each other could be coalesced forming grains with similar orientation,while ETs with different twin variants were separated by twins boundaries contributing to grain refinement.Moreover,in addition to the conventional continuous dynamic recrystallized(CDRX)grains with 30˚orientation rotated around C-axis of the parent grains,CDRXed grains with 30˚rotation around a-axis and random rotation axis were also discerned.Besides,the CDRX evolution induced twins were also elaborated,exhibiting the complex competition between CDRX and twining.Hot torsion deformation with constant decreasing temperatures rate is an effective way of grain refinement and texture modification.

Numerical simulation of 80 ℃ temperature field distribution of thick plate multi-pass welding with SYSWELD

The PPG PITT-CHAR XP flame retardant system has been used by COOEC to preventing the thermal softening of steel in the high temperature,whose degradation temperature is 80 ℃.To prevent damage to PPG PITT-CHAR XP fire retardant paint from excessive heat during welding,it is necessary to get accurately reserved area near the welding joints prior to welding. For the foregoing reasons,the 80 ℃ temperature field distribution of thick plate multi-pass welding was analyzed with SYSWELD.The influence of welding groove form and time interval on welding temperature field was also analyzed. Results showed that the range of 80 ℃ welding temperature field increased with the increasing of weld layers at first and then it inclined to stable value. Interpass time setting was crucial to control the range of 80 ℃ welding temperature field. It was also found that double V groove had better thermal diffusivity than double-bevel groove.And double-bevel groove was better than single V groove.

80-3Cr油管钢在CO_(2)驱环境下的性能研究与应用

针对CO_(2)驱高CO_(2)分压、高H_(2)S分压、低温井筒环境造成N80、P110管柱失效的问题,开展了80-3Cr、N80、P110三种管材的耐CO_(2)腐蚀、抗H_(2)S应力腐蚀开裂、耐低温冷脆对比评价试验。结果表明,不同CO_(2)工况条件下,N80、P110、80-3Cr油管在添加缓蚀剂情况下的腐蚀速率分别为0.0549 mm/a、0.0645 mm/a、0.0333 mm/a;80-3Cr油管的腐蚀速率明显低于N80、P110油管;80-3Cr油管在不同H_(2)S环境下均未出现应力腐蚀开裂,具有较好的抗H_(2)S应力腐蚀性能;在-20℃的低温环境下,N80和P110油管冲击功分别只有80-3Cr油管的62.6%和23.2%;80-3Cr油管在CO_(2)驱油现场应用后,管柱失效率从2019年的20%下降到0,取得显著效果。

Future Changes in Extreme High Temperature over China at 1.5℃-5℃ Global Warming Based on CMIP6 Simulations

Extreme high temperature(EHT)events are among the most impact-related consequences related to climate change,especially for China,a nation with a large population that is vulnerable to the climate warming.Based on the latest Coupled Model Intercomparison Project Phase 6(CMIP6),this study assesses future EHT changes across China at five specific global warming thresholds(1.5℃-5℃).The results indicate that global mean temperature will increase by 1.5℃/2℃ before 2030/2050 relative to pre-industrial levels(1861-1900)under three future scenarios(SSP1-2.6,SSP2-4.5,and SSP5-8.5),and warming will occur faster under SSP5-8.5 compared to SSP1-2.6 and SSP2-4.5.Under SSP5-8.5,global warming will eventually exceed 5℃ by 2100,while under SSP1-2.6,it will stabilize around 2℃ after 2050.In China,most of the areas where warming exceeds global average levels will be located in Tibet and northern China(Northwest China,North China and Northeast China),covering 50%-70%of the country.Furthermore,about 0.19-0.44 billion people(accounting for 16%-41%of the national population)will experience warming above the global average.Compared to present-day(1995-2014),the warmest day(TXx)will increase most notably in northern China,while the number of warm days(TX90p)and warm spell duration indicator(WSDI)will increase most profoundly in southern China.For example,relative to the present-day,TXx will increase by 1℃-5℃ in northern China,and TX90p(WSDI)will increase by 25-150(10-80)days in southern China at 1.5℃-5℃ global warming.Compared to 2℃-5℃,limiting global warming to 1.5℃ will help avoid about 36%-87%of the EHT increases in China.

Impact of Thickness of Polymer Electrolyte Membrane and Gas Diffusion Layer on Temperature Distributions in Polymer Electrolyte Fuel Cell Operated at Temperature around 90℃

Polymer Electrolyte Fuel Cell(PEFC)is desired to be operated at temperature around 90℃ for stationary applications during the period from 2020 to 2025 in Japan.It can be expected thinner polymer electrolyte membrane(PEM)and gas diffusion layer(GDL)would promote the power generation performance of PEFC at this temperature.The aim of this study is to understand the impact of thickness of PEM and GDL on the temperature profile of interface between PEM and catalyst layer at the cathode(i.e.,the reaction surface)in a single PEFC with an initial operation temperature(Tini).An 1D multi-plate heat transfer model based on temperature data of separator measured using thermograph in power generation process was developed to evaluate temperature of the reaction surface(Treact).This study investigated the effect of Tini,flow rate and relative humidity of supply gas on Treact distribution.The study finds that when using thin GDL,the even distribution of Treact – Tini is obtained irrespective of thickness of PEM,Tini and relative humidity conditions.Treact – Tini using Nafion 115 is higher than the other thin PEMs irrespective of Tini and relative humidity conditions.It can be concluded that the even temperature distribution could be achieved by using thin PEM and GDL.

Novel Cascade Refrigeration Cycle for Cold Supply Chain of COVID-19 Vaccines at Ultra-Low Temperature -80°C Using Ethane (R170) Based Hydrocarbon Pair

Several media report highlight on that the pharmaceutical companies require ultra-low temperatures -80°C to transport and store its COVID-19 vaccines. This research presents the thermodynamic analysis on cascade refrigeration system (CRS) with several refrigerant pairs which are R32/R170, R123/R170, R134a/R170, R404A/R170, R407c/R170, R410/R170, and the hydrocarbon (HC) refrigerant pair Propane/Ethane, namely R290/R170. Besides, the results of R22/R170 pair, which is not recommended to be used due to phase out of R22 as per Montréal Protocol, are included as base case to compare the novel hydrocarbon pairs in CRS and the old trend of refrigerant pairs. Thermodynamic properties of all these pairs were investigated and compared under different intermediate temperature used in CRS heat exchanger, which thermally connected both the Low and High temperature cycles (LTC) and (HTC). By applying the first law of thermodynamics, the coefficients of performance (COPs) and the specific power consumptions (SPC) in kW/TR are presented and compared. In addition, by applying the second law of thermodynamics the exergetic efficiencies were estimated. The results reveal the promising opportunity of using the HC pair (R290/R170). The minimum SPC in kW/TR is recorded for the pair R123/R170. One the other hand, the highest exegetic efficiency values are observed to be 40%, 38%, and 35% for the pairs R123/R170, R290/R170, and R134/R170, respectively. This research concludes that the HC pair (R290/R170) is highly recommended for CRS applications either to transport the COVID-19 or store it in cold storage rooms in hospitals and clinics. All precautionary measures should be carefully applied in design and operation of HC pair (R290/R170) due to its flammability hazard.

温度对MX-80膨润土物理性能的影响

为研究高温受热对膨润土物理性能的影响,将MX-80膨润土粉末置于4种不同温度(25、100、150、200℃)下受热30 d后,对其进行比重、界限含水率、膨胀指数试验。在此基础上,利用热重分析试验(TGA)和X射线衍射试验(XRD)揭示高温受热后MX-80膨润土的物理性能变化及微观机理。试验结果表明:MX-80膨润土的比重、界限含水率、膨胀指数均随受热温度增加而减小,100℃以下受热时温度对膨润土物性的影响较小,在150℃及以上受热时对物性指标的影响较大;受热30 d后MX-80膨润土中蒙脱石含量减少,150、200℃下受热后出现了新矿物钠云母,表明受热温度达到150℃后土中出现了蒙脱石向钠云母的转化;受热后MX-80膨润土吸附的弱结合水、强结合水含量减少;MX-80膨润土物理性能的变化可归因于不同高温作用后土中蒙脱石向钠云母的转化和结合水的脱附。

-80℃冻存的自体外周血造血干细胞移植重建造血的观察

目的:本研究旨在明确-80℃非程控降温对于保存外周血造血干细胞的效果。方法:观察104例自体移植的病例,外周血造血干细胞采用-80℃非程控降温,采用5%的二甲亚砜(DMSO)、20%人血白蛋白(HSA)以及羟乙基淀粉40(HES)作为冻存保护液,中位冻存时间为30.5 d,观察冻存前后细胞活性、CD34+细胞、单个核细胞(mononuclear cells,MNCs)以及植入情况。结果:本冻存方式可以在短时间内很好的保存外周血造血干细胞。104例患者除2例发生移植相关死亡外,余患者均顺利植入,白细胞中位植入时间为12 d,血小板中位植入时间为14d,复苏后细胞活性为94%,CD34+细胞回收率为86%,单个核细胞回收率为80.3%,性别,化疗周期和放疗对于植入时间均无明显影响,白细胞的植入与CD34+细胞的输注量呈线性关系。结论:本研究的冻存方式安全、有效,完全可以满足临床需求。这种节约资金、人力的干细胞保存方式可以被广泛地应用和推广。

低温-80℃长期保存单采血小板的功能研究

目的 :为明确长期冰冻保存的单采血小板的功能 ,并对冰冻单采血小板的保存时间进行初步探讨。方法 :对冰冻保存前后的单采血小板进行回收率、粘附率、聚集强度和Ⅲ因子活性进行检测。结果 :冰冻保存后的回收率为 83 8%± 8 3 % ,粘附率为 5 9 0 %± 9 2 % ,聚集强度为 66 1%± 13 2 % ,Ⅲ因子活性为 ( 18± 3 )s。结论

-20℃低温环境下大口径X80钢管的焊接

本文对试验用X80钢的焊接性进行了详尽的分析,进行了-20℃低温环境下可行的2种焊接工艺试验,根据相应的常规力学性能试验、金相检验和硬度测试结果,提出了-20℃低温环境下相应的焊接工艺参数和技术措施。

猪皮、尸体皮在-80℃冰箱降温-LN_2冻存中细菌学的动态观察

目的 :探讨猪皮、尸体皮在冷冻保存过程中 ,消毒剂、冷冻及抗冻剂对皮肤细菌的影响。方法 :将新鲜消毒的中厚猪皮、尸体皮和经过 - 80℃降温 ,LN2 冻存的猪皮、尸体皮各取 6块行需氧菌和厌氧菌培养 ,而后做细菌学检测。结果 :猪皮冷冻前后三组各时间点均检出细菌 ,尸体皮仅冷冻前和冷冻后对照组及 10 %D -KR组检出细菌 ,余未检出细菌。所检出的需氧菌为表皮葡萄球菌和棒状杆菌 ,厌氧菌为丙酸杆菌和贪婪丙酸杆菌。猪皮所检细菌量 3- 5CFulog/g ,尸体皮 <4CFulog/ g。结论 :猪皮细菌检出率明显高于尸体皮 ,冷冻对细菌检出率有一定影响 ,温度越低影响越大 ,但与冷冻时间长短无关。抗冻剂对皮肤细菌无影响。常规清洗消毒方法不能完全清除皮肤细菌。

-45℃低温环境用X80钢级Φ1422 mm×30.8 mm站场直缝焊管的开发及性能研究

针对中俄东线天然气管道工程用站场低温管的技术要求,通过对焊管焊接工艺、焊材匹配及扩径工艺的研究,开发出了-45℃低温环境用X80钢级Ф1422mm×30.8mm站场直缝焊管,并对焊管力学性能进行了检验。检验结果表明,焊管管体屈服强度为606~660 MPa,抗拉强度为681~737 MPa,屈强比为0.85~0.91,-45℃时冲击功平均值为327 J,DWTT剪切面积平均值为57%;焊缝冲击功平均值为144J,热影响区冲击功平均值为225 J。各项性能指标均满足《中俄东线天然气管道工程站场低温环境用管材、管件技术条件第5部分:站内钢管》要求。

-80℃冰箱冷冻保存恶性血液病患者自体外周血造血干细胞的临床应用

自体干细胞移植（autologous peripheral blood stem cell trans-plantation,APBSCT）是治愈某些恶性血液病的有效手段之一。除采集的干细胞CD34＋细胞数是否达到最低阈值[（1～2）×10^6/kg]以上外,干细胞冻存方法直接影响造血干细胞存活率的高低，是APBSCT是否成功的关键技术。我科自2007年1月至2008年5月为7例APBSCT患者进行了12次自体干细胞采集，平均采集次数1．7次／例，每次采集干细胞均用造血干细胞低温保护剂保护并直接在-80℃冰箱冷冻保存，取得了很好的效果，现报告如下。

浅议-80℃低温冰箱的研制

目前超低温冰箱已被广泛应用于生物医疗、科研实验等领域。本文着重对 - 80℃超低温冰箱的研制目的 ,基本结构 ,制冷方法以及实验数据作简要阐述。

-80℃保存自制血浆用于血浆纠正实验对检测PT与APTT延长的价值研究

目的观察-80℃保存自制血浆用于血浆纠正试验对检测凝血酶原时间(PT)与活化部分凝血活酶时间(APTT)延长的临床应用价值.方法选取40份PT或APTT延长的血浆标本,分别与正常混合血浆和-80℃保存的自制血浆按1:1比例进行混合并立即进行PT或APTT测定,37℃环境下孵育1 h后进行再次检测,与正常混合血浆混合作为对照组,与-80℃保存的自制血浆混合作为研究组.计算40份血浆标本可被正常混合血浆纠正的情况,比较两组的纠正率.结果35份标本能立即被正常混合血浆纠正,占比87.50%;4份标本未能被立即纠正,并且孵育前、后所测得的结果没变,占比10.00%;1份标本除了未被纠正,同时孵育后测定时间比孵育前更长,占比2.50%.研究组孵育前、后APTT均长于对照组,差异具有统计学意义(P<0.05);对照组孵育前、后在PT延长纠正试验中的纠正率分别为(37.28±14.46)%、(38.01±15.05)%,在APTT延长试验中的纠正率分别为(32.92±16.18)%、(32.61±15.28)%,与研究组的(40.07±13.85)%、(35.35±15.22)%和(27.55±23.49)%、(27.58±21.13)%比较,差异均无统计学意义(P>0.05).结论-80℃保存自制血浆可替代商品化的正常混合血浆用于血浆纠正试验对PT与APTT延长的检测,成本低,且使用方便,对于预算开支相对紧张的基层单位值得借鉴应用.

一种80℃固化环氧树脂体系的非等温固化动力学

采用非等温DSC研究了80℃固化环氧树脂体系LTCEP的非等温固化行为。采用GaussianLorentzian加和模型对DSC曲线进行分峰处理,采用Flynn-Wall-Ozawa法确定不同阶段反应的活化能随转化率的变化情况。然后采用Málek方法研究不同阶段反应的非等温固化动力学,得到树脂体系总的反应速率方程并预测树脂体系在不同温度下的固化行为。最后采用拉伸测试表征了LTCEP体系的力学性能。非等温DSC结果表明该树脂体系的DSC曲线可用三个独立的放热峰进行叠加来拟合;三个阶段反应活化能随转化率的变化均不明显,其活化能平均值分别为85.98、84.85和87.16 k J/mol;Sesták-Berggren模型可很好地描述该树脂体系在不同阶段的固化行为。预测LTCEP在150℃下3 min、140℃下5.5 min即可达到90%转化率。拉伸测试结果表明LTCEP经80℃固化后拉伸强度和断裂伸长率分别为(51.34±11.78)MPa和(1.23±0.34)%,125℃后处理对拉伸性能影响不大。

MX-80膨润土高温老化时间效应的细微观分析

在200℃高温条件下,对MX-80膨润土粉末进行了不同时长(0、15、30、60、90、120 d)的热老化预处理;通过热重分析(thermogravimetric analysis,简称TGA)、X射线衍射(X-ray diffraction,简称XRD)和电镜扫描(electron microscope scanning,简称SEM)等试验探讨了MX-80膨润土中结合水、矿物成分、微观形貌等随热老化时间t的变化规律;基于蒙脱石矿物晶体结构学理论揭示了MX-80膨润土高温老化时间效应的细微观机制。试验结果表明:(1)膨润土中自由水、弱结合水和强结合水随热老化时间t的递增均发生不同程度的脱附现象,0~15 d变化显著,15 d后趋于稳定,120 d后三者降幅分别为82.6%、68.8%和96.5%;(2)随着热老化时间t的增加,膨润土主要矿物成分蒙脱石部分转化为稳定性较好的钠云母,0~15 d变化显著,15 d后趋向稳定,120 d后二者的变化量分别为–12.57%和+12.47%;(3)高温热老化过程中,蒙脱石矿物的晶层间距减小,引起片层状矿物之间收缩变形,导致膨润土的微观形貌随着热老化时间t的递增发生不同程度的变化;(4)高温热老化状态下,膨润土的矿物成分转化、结合水脱附、微观形貌改变等三者之间相互作用和彼此影响,是引起膨润土宏观物理力学性能发生变化的根本原因。

贴壁培养细胞直接用培养瓶置-80℃冻存

目的:探讨贴壁培养细胞直接用培养瓶置4℃、-20℃,最后置-80℃低温冰箱冻存的可行性。方法:采用培养瓶常规培养贴壁细胞L929,去上清后,加冻存液覆盖细胞。-80℃低温冰箱冻存,然后,每2个月复苏1次,计数活细胞,观察细胞传代效果。结果:L929细胞置-80℃低温冰箱冻存1年,复苏良好,随着冻存时间延长,存活细胞逐渐减少,复苏耗时延长。结论:贴壁培养细胞直接用培养瓶置-80℃低温冰箱冻存1年,复苏良好。

钢丝缠绕增强聚乙烯复合管的80℃静液压研究

CJ/T 189—2007和GB/T 32439—2017是钢丝缠绕增强聚乙烯复合管(简称钢丝管)现行标准,但CJ/T 189—2007标准中的80℃、1.2倍公称压力(PN)、165 h静液压测试存在较大争议。针对钢丝管80℃静液压问题,以耐热级管道料为基体、EN390高温黏接树脂、双密封连接三种优化配置制备了dn160×3.5 MPa钢丝管,研究了不同倍率公称压力的80℃静液压。结果表明:钢丝管的剥离强度、20℃、2 PN、1 h静液压、60℃、1.2 PN、165 h静液压均符合GB/T 32439—2017要求;以夹具和双密封两种连接方式,80℃、1.2 PN、165 h静液压均无法通过,当测试压力折减为0.8 PN,80℃、165 h静液压测试通过。