Evaluation of Oxidation of Ti-Al and Ti-Al-Cr Coatings Arc-ion Plated on Ti-60 High-temperature Titanium Alloy

High-temperature titanium alloy for aeroengine compressor applications suffers from high-temperature oxidation and environmental corrosion, which prohibits long-term service of this kind alloy at temperatures above 600℃. In an attempt to tackle this problem, Ti-48Al （at. pct） and Ti-48Al-12Cr （at. pct） protective coatings were plated on the substrate of alloy Ti-60 by arc ion plating （ALP） method. Isothermal and cyclic oxidation tests were performed in static air at elevated temperatures. Phase composition, morphology of the coatings and distribution of elements were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and energy dispersive X-ray analysis （EDX）. The results showed that the Ti-48Al coating exhibited good isothermal oxidation resistance during exposure at 800℃, but poorer resistance against oxidation at 900℃. By contrast Ti-48Al-12Cr coating demonstrated excellent isothermal oxidation resistance at both temperatures. Cyclic oxidation tests performed at 800℃ indicated that resistance and no spallation of coatings was observed. But both coatings demonstrated good cyclic oxidation at 900℃ only Ti-48Al-12Cr coating demonstrated excellent cyclic oxidation resistance.

Utility and Weight of Factors of Bus Transit's Service Quality Analysis in Nanjing

Service quality is a major factor that affects how public transport users evaluate bus service. In order to evaluate how bus users make trade-offs across travel cost,time,reliability,etc.,and to investigate the extent to which the components of service quality vary according to relevant trip characteristics,this paper analyzes service quality of bus transit with the conjoint analysis. Through data analysis,the levels 'utility values of reliability,waiting time,walking time,etc.,on the commuter trip and the non-commuter trip are gotten,so it is the utility function of the transit system. Then the factors' weights are obtained through the utility values. The results show that on the commuter trip,passengers value reliability the most,which is followed by waiting time and walking time,while in-bus environment,price and station environment's weights are small. While on the non-commuter trip,the weights in a higher order to lower order are the first for reliability,the second for in-bus environment,the third for walking time,the fourth for station environment and the last for ticket price.

Analysis of 24-hour Monitoring of Intraocular Pressure in 1055 Eyes

Purpose:.To investigate the clinical significance of 24-hour monitoring of intraocular pressure(IOP).Methods: A total of 571 cases(1055 eyes) undergoing 24-hour monitoring of IOP in the Second People's Hospital of Zhengzhou between June 2012 and March 2013 were retrospectively analyzed.Results: Among all 1055 eyes,.298 had suspected glaucoma(28.2%); 390(37.0%) were diagnosed with glaucoma but received no treatment(312 with primary open angle glaucoma(POAG).and 78 with primary angle closure glaucoma(PACG));215(20.4%) were diagnosed with glaucoma and received medical treatment;. 132( 12. 5 %). underwent glaucoma filtration surgery;.and there were 20 others..Through 24-hour IOP monitoring,.104 among 298 cases with suspected glaucoma were diagnosed with normal tension glaucoma(NTG),.110 with POAG,.and 28 with the secondary glaucoma..Condition assessment and treatment plans were presented for 390 glaucoma cases receiving no treatment..Adjustment was made in the medical treatment of 138 eyes..Following glaucoma filtration surgery,.52 eyes received clinical advice on subsequent treatment.Conclusion: The simplified 24-hour IOP monitoring method is readily accepted by patients,.which is of great significance for providing guidance on the diagnosis of glaucoma and the assessment of the efficacy of glaucoma surgery..However,one-time 24-hour IOP monitoring is not sufficiently efficacious to make a definite diagnosis of NTG..Therefore,.long-term follow-up and repeated 24-hour IOP monitoring are required to diagnose NTG,.along with a variety of related examinations.

Effect of Crowding in Metro Carriages on Travelers’ Disutility: An Evidence from Guangzhou Metro

Overcrowding has become a non negligible issue for metros in China.This paper analyzes the impact of crowding in metro carriages on people’s travel behaviors based on the stated preference survey data from college students and full time workers in Guangzhou.The data were analyzed by using the constant value per trip model and the travel time multiplier model with the multinomial logit modeling technique.Results show that there is a significant impact of crowding in metro carriages on passengers’welfare.The relationship between the disutility of crowding and the standee density is not linear.Commuters do not care much about crowding in the metro,whereas non commuters and college students pay special attention to crowding in metro carriages,especially when the carriage is crowded.This paper presents new findings of the impact of demographic characteristics on the evaluation of crowding in metro carriages in developing countries.

Impact of the Real-time Bus Information on Bus Riders, an Evidence from Guangzhou

This paper evaluates impacts of the real-time information from the smartphone APP and the real-time information board at bus stops on bus users with survey data. Through the analysis of data with t-test and linear regression, it is found that the waiting time of bus riders with real-time information from the smartphone APP is much less than that of bus riders without the real-time information. As to the perceived waiting time of bus users, through the linear regression, the study finds that without the real-time information, bus riders’ perceived waiting time is greater than waiting time. At the same time, the perceived waiting time of bus users with real-time information is only slightly larger than their waiting time. Through regressing anxiety on real-time information, perceived waiting time and so on, it is found that real-time information reduces anxiety remarkably.

How do Users Evaluate Service Quality of the Dockless Bicycle Sharing System?

In order to improve the public transit’s accessibility and promote service quality of the public transit,it is necessary to alleviate the“last⁃mile”problem.The combination of the public transit and bicycle⁃sharing system is competitive compared with the private car.In 2016,the dockless bicycle⁃sharing system has been undergoing tremendous development.Because the dockless bicycle⁃sharing system is different from previous bicycle⁃sharing systems,components of service quality of the dockless bicycle⁃sharing system differ.However,there are few articles about the service quality of the dockless bicycle⁃sharing system.This paper examined the evaluation of service quality of the dockless bicycle⁃sharing system along with a measurement of users’satisfaction.A questionnaire about service quality was designed,which includes 15 factors.Through the analysis of travelers’evaluation of factors of the dockless bicycle⁃sharing system with Rasch Model,these original ordinal data(Likert data)was transformed to the interval data:the person parameter(ability)and the item parameter(difficulty).Through the analysis of interviewees’abilities,it was found that only education and monthly consumption have significant influence on interviewees’evaluation of service quality of the dockless bicycle⁃sharing system,while there is no significant influence of gender,weekly use of dockless shared⁃bicycle,private car ownership,or monthly income on the evaluation.Furthermore,it was found that users were dissatisfied with cycling under the adverse weather,disturbance from pedestrians and cars,continuity of the bicycle lane,complaint channel,and staff service the most.

Identification of novel biomarkers for varicocele using iTRAQ LC-MS/MS technology

To the Editor:Varicocele(VC)is a vascular disease and considered as the main cause of male infertility.^([1])The incidence of VC in the common male population was 4.4–22.6%,of which the incidence of primary infertility was 35–40%,while the incidence of secondary infertility was as high as 80%.^([2])The exact pathophysiological mechanism of male infertility caused by VC and regulative molecules are still unclear.Clear and definite molecular markers of VC disease are helpful for early prevention and timely treatment.This study aimed to screen candidate regulative molecules playing a role in male infertility caused by VC.

合并高钠血症供肝在劈离式肝移植中的应用

目的探讨不同程度高钠血症供肝在劈离式肝移植(SLT)中应用的安全性和疗效。方法回顾性分析2017年9月至2022年1月在中山大学附属第三医院行SLT的连续122例供受者临床资料。供受者或(和)家属均签署知情同意书,符合医学伦理学规定。供者均为公民逝世后器官捐献,其中男97例,女25例;年龄4.6~56.8岁,中位年龄27.3岁。受者中,男85例,女37例;年龄0.2~82.8岁,中位年龄8.0岁。供者和受者经过严格筛选和匹配,选择循环稳定的供者,尽可能缩短冷缺血时间(CIT)≤8 h,供肝尽可能选取质地柔软、无或轻微脂肪变(<10%),并优化供肝灌注流程。根据供者血钠浓度将受者分为高钠血症组(160 mmol/L≤血清钠浓度<170 mmol/L,22例)和对照组(血清钠浓度<160 mmol/L,100例)。两组受者CIT、术中出血量比较采用秩和检验;术后7 d早期移植物功能障碍发生率、术后30 d死亡比较采用χ2检验;术后90 d生存情况分析采用Kaplan-Meier法和Log-rank检验。结果高钠血症组CIT和术中出血量中位数分别为445(360,514)min、700(300,1500)ml,对照组相应为450(360,510)min、500(200,1200)ml,差异无统计学意义(Z=-0.182,0.448;P>0.05)。两组受者术后7 d早期移植物功能障碍发生率分别为36%(8/22)、40%(40/100),术后30 d死亡率分别为5%(1/22)、6%(6/100),差异无统计学意义(χ2=0.100,0.071;P>0.05);两组受者术后90 d累积生存率分别为90.9%、93.0%,两组术后生存率比较差异无统计学意义(χ2=0.014,P>0.05)。结论供者血清钠浓度<160 mmol/L的供肝可用于劈离;当160 mmol/L≤血清钠浓度<170 mmol/L时,通过更加严格的脂肪肝评估、CIT控制和优化供肝灌注流程,亦可谨慎安全地实施SLT。

Rolling texture and its effect on tensile property of a near-α titanium alloy Ti60 plate

Rolling texture and its effect on tensile properties of Ti60 alloy plates were investigated in the present study. The plates were β-rolled at 1070℃ and(α+β)-rolled at 980℃, using uni-directionally rolling(UDR) and cross-directionally rolling(CDR) processes, respectively.β-rolled plates exhibited weak textures, which were attributed to the dispersive orientations of secondary α during the β→α phase transformation. Strong deformation textures formed in(α+β)-rolled plates as a result of slipping mechanisms: the strong T-type texture in UDR plate was related to {10 1 0}[11 2 0] slipping, while the B-type texture in CDR plate was relevant with {0001}[11 2 0] slip. Strong T-type textures led to anisotropic tensile properties. B-type textures would decrease such an anisotropy. The(α+β)-CDR process was found to be a candidate process for reducing anisotropy of Ti60 alloy plates.

Precipitates and alloying elements distribution in nearαtitanium alloy Ti65

Precipitates,including silicides and Ti3 Al(α2)phase,and alloying elements distribution in a near a titanium alloy Ti65(Ti-5.8 Al-4.0 Sn-3.5 Zr-0.5 Mo-0.3 Nb-1.0 Ta-0.4 Si-0.8 W-0.05 C)after solution treatment and aging process were characterized by using transmission electron microscopy(TEM)and atom probe tomography(APT).Quantitative composition analysis and TEM observation indicate that the silicides fit to(Ti,Zr)6(Sl,Sn)3.Zr exhibits aβ-stabilizing effect in near a titanium alloys but is weaker than otherβstabilizing elements.The enriching tendency of the alloying elements in the retainedβphase is in the order of Zr<Nb<Ta<Mo<W.The experimental results are rationalized by the relative stability of alloying elements in the a andβphases and the mobility of these atoms in the matrix.An enrichment of Si in theα2 phase over theαmatrix phase is noticed,which is attributed to the lower formation energy of Si in theα2 phase.

Mechanical properties of electron beam welded dissimilar joints of TC17 and Ti60 alloys

Microstructure, hardness, tensile and high cycle fatigue （HCF） properties of the welded dissimilar joints of Ti60 and TC17 titanium alloys had been investigated in this study. A significant microstructural change was observed to occur after welding, with rod-like α and β phases in the fusion zone （FZ）, equiaxed et phases, fine α laths and β phases in the heat-affected zone （HAZ） of TCl7 side and acicular martensite α＇ phases＋＂ghost＂ α phases in the HAZ of Ti60 side, The microhardness across the joints exhibited an inhomogeneous distribution with the highest hardness of ~404 HV in FZ and the lowest hardness of ~304 HV in base material （BM） of Ti60. All the joints tested in tension fractured at BM of Ti60 side. Fatigue limits of the joints at 107 cycles were 425 MPa at room temperature and 380 MPa at 400 ℃, respectively. Welding micropores were found to be the main source of fatigue crack initiation.

Dwell and Normal Cyclic Fatigue Behaviours of Ti60 Alloy

An experimental study of dwell and normal cyclic fatigue behaviours was carried out using specimens from a Ti60 forging with a bimodal microstructure. Apparent decrease in the fatigue life was found under dwell fatigue condition as compared to that under normal cyclic condition. Strain produced in each cycle in dwell fatigued specimens was observed larger than that in its normal cyclic-fatigued counterparts. Interior crack initiation was found in most dwell fatigued specimens as compared to the subsurface crack initiation under normal cyclic fatigue condition. Flat and bright facets were found at crack initiation sites in both cases. The facet density is higher in dwell condition, which is consistent with the crystal orientation and Schmid factors analysis of α grains around secondary cracks using electron back-scattered diffraction （EBSD） methods. Dwell loading favours cleavage in α grains with their basal plane normals aligned no more than 15° to the loading axis, which may account for its lower fatigue life according to the present study.

Microstructure and Mechanical Properties of Electron Beam Welded Titanium Alloy Ti-6246

Electron beam welding （EBW） was applied to a 10-mm-thick plate cut from Ti-6246 compressor disk. The microstructural characteristics, microhardness and room temperature tensile properties were investigated. Microstructure observations indicated that there existed plenty of thin needle-like α platelets studding in the matrix of the columnar β grains in the as-welded fusion zone （FZ）. Post-weld heat treat- ment （PWHT） led to the precipitation of small secondary α platelets in the β matrix in heat affected zone and FZ. The thickness and the density of α platelets increased as the temperature of PWHT increased from 545 to 645 C. The microhardness across the Ti-6246 EBWjoint exhibited a nonuniform distribution. The hardness increased with the decrease of distance to the weld center, and reached the maximum of 467 HV in FZ when PWHT was carried out at 595 C. All the weldments tested with tension were fractured at the base material （BM） and exhibited a ductile fracture mode. The major deformation barrier in BM was the platelet α/β interfaces, however, the major deformation barrier in FZ was found to be β grain boundaries and secondary α/β interfaces. The BM with thicker platelet α phases had lower strength than the other two zones in the joint, and the BM deformed first and led to fracture in this zone.

Preparation and characterization of carbonyl iron/strontium hexaferrite magnetorheological fluids

The heat transfer oil-based magnetorheological fluid （MRF） was prepared using oleic acid-modified micron carbonyl iron powder as a magnetic dispersed phase and strontium hexaferrite （SrFe12019） nanoparticles as an additive. The sedimentation stability of MRFs was studied. The results indicated that the stability of MRFs was improved remarkably by adding SrFel2019 nanoparticles and the sedimenta- tion ratio was only 0.88 in 20 days when the content of nanoparticles reached 10wt%. The rheological properties were characterized by a HAAKE rheometer without a magnetic field and a capillary rheometer with and without a magnetic field. The effects of SrFe12019 nanoparticles, the temperature, and magnetic field strength were investigated. In addition, the rheological properties could be predicted well using the improved Herschel-Bulkley model, even under a magnetic field. A theoretical model was also proposed to predict the yield stress based on the microstructure of the MRF under an applied magnetic field.

Expert consensus on perioperative management of liver transplantation in adults with acute-on-chronic liver failure

Acute-on-chronic liver failure(ACLF)is a syndrome in which acute liver failure with extrahepatic organ failure occurs on chronic liver disease.Recently,liver transplantation is the only effective treatment for ACLF.There is still room for discussion on the optimal surgery timing for ACLF,perioperative infection prevention and control,and maintenance of nutrition and organ function.The Transplantation Immu-nology Committee of Branch of Organ Transplantation Physician of Chinese Medical Doctor Association and Enhanced Recovery of Liver Transplantation Group of Enhanced Recovery after Surgery Committee of Chinese Research Hospital Association invited relevant experts to discuss the perioperative management of ACLF liver transplantation in areas including surgery timing,organ protection,nutritional support,infection prevention and control,rehabilitation exercises,regulation of the internal environment,etc.An expert consensus was developed as reference for clinicians.

Arterial stiffness and stroke:de-stiffening strategy,a therapeutic target for stroke

Stroke is the second leading cause of mortality and morbidity worldwide.Early intervention is of great importance in reducing disease burden.Since the conventional risk factors cannot fully account for the pathogenesis of stroke,it is extremely important to detect useful biomarkers of the vascular disorder for appropriate intervention.Arterial stiffness,a newly recognised reliable feature of arterial structure and function,is demonstrated to be associated with stroke onset and serve as an independent predictor of stroke incidence and poststroke functional outcomes.In this review article,different measurements of arterial stiffness,especially pressure wave velocity,were discussed.We explained the association between arterial stiffness and stroke occurrence by discussing the secondary haemodynamic changes.We reviewed clinical data that support the prediction role of arterial stiffness on stroke.Despite the lack of long-term randomised double-blind controlled therapeutic trials,it is high potential to reduce stroke prevalence through a significant reduction of arterial stiffness(which is called de-stiffening therapy).Pharmacological interventions or lifestyle modification that can influence blood pressure,arterial function or structure in either the short or long term are promising de-stiffening therapies.Here,we summarised different de-stiffening strategies including antihypertension drugs,antihyperlipidaemic agents,chemicals that target arterial remodelling and exercise training.Large and well-designed clinical trials on de-stiffening strategy are needed to testify the prevention effect for stroke.Novel techniques such as modern microscopic imaging and reliable animal models would facilitate the mechanistic analyses in pathophysiology,pharmacology and therapeutics.

Investigation of beta fleck formation in Ti-17 alloy by directional solidification method

Beta flecks are one of the most common defects occur in someα+βandβtitanium alloys.In this study,formation of beta flecks in Ti-17 alloy was investigated by directional solidification experiments.Samples were directionally solidified under a constant temperature gradient of 2×10^4 K/m and a wide range of withdrawal rates(R)from 3 mm/h to 150 mm/h.We find that macrostructure of the directionally solidified Ti-17 samples can be characterized by"four zones and two lines"after the heat treatment.Profile of the solid-liquid interface transits from planar to cellular to dendritic shape with solidification rate increasing from 3 mm/h to 150 mm/h.The critical rates for planar to cellular(Rc1)transition and cellular to dendritic(Rc2)transition can be well predicted based on the traditional solidification theory.Dark and light contrast areas in macrostructure are directly related to elemental segregation.Dark contrast areas are rich of Cr,Zr but lean of Mo,while no apparent segregation is found in light contrast areas and the mean level of Cr,Zr is lower and Mo is higher in this area than that in dark contrast areas.We conclude thatβ-flecks in Ti-17 titanium alloy are induced by segregation of alloying elements with k<1 and their shape and size are determined by solidification conditions.Based on the findings of the present article and other literatures,three types ofβ-flecks are proposed and their formation mechanisms are discussed.

Creep Behavior of Fusion Zone and Base Metal of the Electron Beam Weldments of a Near-alpha Titanium Alloy

The high temperature creep behavior of fusion zone （FZ） and of a near-alpha titanium alloy Ti-60 has been investigated. base metal （BM） of the electron beam weldments While the BM shows a fully transformed, coarse primary β grains with large colonies consisting of aligned α lamellar, the FZ exhibits thin martensitic α′ platelets in the columnar β grains. The creep results show that the steady state creep rates of FZ follow the power-law creep, with the stress exponents obtained in the range from 5.6 （550℃） to 5.9 （600℃）, and corrected activation energies of 309-352 kJ/mol; the stress exponents of BM exhibit different values when the creep testing stress and temperature alternate. The values of 2.4-3.2 are obtained when the stresses are under 220 MPa or the temperature is 550℃, also an exponent of 6.6 is achieved at stresses above 220 MPa at 600℃. The corrected activation energies of BM corresponding to the stress exponents are 123-161 kJ/mol （n=2.4-3.2） and 344 kJ/mol （n=6.6）. The creep mechanisms of FZ and BM have been discussed in light of the creep microstructures, activation energies and the stress exponents. The creep mechanisms of FZ is the diffusion controlled dislocation climb, the creep of BM is controlled by ＇solute drag＇ creep and dislocation climb when the stress and temperature are different. Transmission electron microscopy （TEM） observations of the dislocation structures of crept specimens are presented to give some supports for the creep behavior of FZ and BM. In addition to the creep mechanism of dislocation movement, the interface sliding has been found to play an important role during creep of FZ.

Effect of stress ratio on very high cycle fatigue properties of Ti-10V-2Fe-3Al alloy with duplex microstructure

In fatigue critical applications, Ti-10V-2Fe-3Al alloy components are expected to endure cyclic loading with cycles above 109. To assess their operating safety, S-N relations of Ti-10V-2Fe-3Al alloy in very high cycle fatigue （VHCF） regime are of concern and have been investigated in this work. Fatigue behavior including S-N curves and crack initiation mechanisms is reported. Two transitions of fatigue crack initi- ation mechanism, from internal crack initiation to surface crack initiation and from αp cleavage to αS/β decohesion, occur when the stress ratio （R） and stress level are reduced. Fatigue limits exist at Nr = 6×10^7 cycles for all stress ratios except for 0.5. In the VHCF regime two kinds of internal crack initiation mechanisms exist, i.e., coalescence of cluster of αp facets and αS/β decohesion. Their mutual competition depends on the stress ratio and can be interpreted in terms of different stress character required for promotion on different internal crack initiation mechanism. Small crack propagation is discussed to be life controlling process under the stress ratio range from -0.5 to 0.1 during VHCF regime while under the stress ratio 0.5 VHCF, life almost refers to the life required for crack initiation.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.

Overexpression of netrin-1 improves neurological outcomes in mice following transient middle cerebral artery occlusion

Netrin-1(NT-1)is one of the axon-guiding molecules that are critical for neuronal development.Because of its structural homology to the endothelial mitogens,NT-1 may have similar effects on vascular network formation.NT-1 was shown to be able to stimulate the proliferation and migration of human cerebral endothelial cells in vitro and also promote focal neovascularization in adult brain in vivo.In the present study,we reported the delivery of NT-1 using an adeno-associated virus(AAV)vector(AAV-NT-1)into mouse brain followed by transient middle cerebral artery occlusion(tMCAO).We found that AAV vectors did not elicit a detectable inflammatory response,cell loss or neuronal damage after brain transduction.The level of NT-1 was increased in the AAV-NT-1-transduced tMCAO mice compared with the control mice.Furthermore,the neurobehavioral outcomes were significantly improved in AAV-NT-1-transduced mice compared with the control animals(P<0.05)7 days after tMCAO.Our data suggests that NT-1 plays a neuronal function recovery role in ischemic brain and that NT-1 gene transfer might present a valuable approach to treat brain ischemic disorders.