Specific Relationship between the Surface Air Temperature and the Area of the Terra Nova Bay Polynya,Antarctica

Antarctic polynyas play an important role in regional atmosphere?ice?ocean interactions and are considered to help generate the global deep ocean conveyer belt.Polynyas therefore have a potential impact on the Earth’s climate in terms of the production of sea ice and high-salinity shelf water.In this study,we investigated the relationship between the area of the Terra Nova Bay polynya and the air temperature as well as the eastward and northward wind based on the ERA5 and ERAInterim reanalysis datasets and observations from automatic weather stations during the polar night.We examined the correlation between each factor and the polynya area under different temperature conditions.Previous studies have focused more on the effect of winds on the polynya,but the relationship between air temperature and the polynya area has not been fully investigated.Our study shows,eliminating the influence of winds,lower air temperature has a stronger positive correlation with the polynya area.The results show that the relationship between the polynya area and air temperature is more likely to be interactively influenced.As temperature drops,the relationship of the polynya area with air temperature becomes closer with increasing correlation coefficients.In the low temperature conditions,the correlation coefficients of the polynya area with air temperature are above 0.5,larger than that with the wind speed.

The corrosion behaviors of Mg-7Gd-5Y-1Nd-0.5Zr alloy under(NH4)_(2)SO_(4),NaCl and Ca(NO_(3))_(2)salts spray condition

The corrosion behaviors of Mg–7Gd–5Y–1Nd–0.5Zr alloys after T5 treatment under(NH4)_(2)SO_(4),NaCl and Ca(NO_(3))_(2)salt spray condition were investigated by weight loss rates,residual mechanical properties,scanning electron microscope(SEM),X-ray Diffraction(XRD)and potentiodynamic polarization tests.The corrosion degree of Mg–7Gd–5Y–1Nd–0.5Zr alloys in Ca(NO_(3))_(2)salt spray was very shallow by corrosion morphology and the corrosion route was extended along the surface in texture-like shape,while the alloy in NaCl and(NH4)_(2)SO_(4)salt spray were major local corrosion and there were serious corrosion pits on the surface.The weight loss rates in(NH4)_(2)SO_(4),NaCl and Ca(NO_(3))_(2)salt spray was respectively 0.4147,0.1618 and 0.0725 mg/(cm2 d−1).The results of residual mechanical properties indicated that the corrosion order in salts spray of Mg–7Gd–5Y–1Nd–0.5Zr alloys is NH4SO4>NaCl>Ca(NO_(3))_(2),which was consistent with the results of potentiodynamic polarization tests.The type of the salts will play a vital role in the initiation of the corrosion of EW75 alloy when they are used in the atmosphere environments.Inorganic salts with the smaller PH value after dissolution will have a stronger impact on the corrosion of EW75 magnesium alloys.

Textbook outcome in gallbladder carcinoma after curative-intent resection:a 10-year retrospective single-center study

Background:Textbook outcome(TO)can guide decision-making among patients and clinicians during preoperative patient selection and postoperative quality improvement.We explored the factors associated with achieving a TO for gallbladder carcinoma(GBC)after curative-intent resection and analyzed the effect of adjuvant chemotherapy(ACT)on TO and non-TO patients.Methods:A total of 540 patients who underwent curative-intent resection for GBC at the Department of Hepatobiliary Surgery of the First Affiliated Hospital of Xi’an Jiaotong University from January 2011 to December 2020 were retrospectively analyzed.Multivariable logistic regression was used to investigate the factors associated with TO.Results:Among 540 patients with GBC who underwent curative-intent resection,223 patients(41.3%)achieved a TO.The incidence of TO ranged from 19.0%to 51.0%across the study period,with a slightly increasing trend over the study period.The multivariate analysis showed that non-TO was an independent risk factor for prognosis among GBC patients after resection(P=0.003).Age≤60 years(P=0.016),total bilirubin(TBIL)level≤34.1 mmol/L(P<0.001),well-differentiated tumor(P=0.008),no liver involvement(P<0.001),and T1-2 stage disease(P=0.006)were independently associated with achieving a TO for GBC after resection.Before and after propensity score matching(PSM),the overall survival outcomes of non-TO GBC patients who received ACT and those who did not were statistically significant;ACT improved the prognosis of patients in the non-TO group(P<0.05).Conclusion:Achieving a TO is associated with a better long-term prognosis among GBC patients after curative-intent resection,and ACT can improve the prognosis of those with non-TO.

Enhancing strength and ductility in back extruded WE71 magnesium alloy cylindrical parts by introduction of multi-direction forging process

Magnesium cylindrical parts have relatively poor mechanical properties and distinct anisotropy of microstructure,which hinder their application as structural components.To improve the performance of WE71 cylindrical parts,multi-direction forging(MDF)was introduced before back extrusion,and the microstructure and mechanical properties were investigated.Results of microstructure show that the grain size in the outer of the cylindrical bottom is refined from 30.1 to 27.7μm,the micro structure is more uniform and the dislocation density is higher.The bimodal grain structure is formed in the outer of the cylindrical wall,which is ascribed to the formation of MgsRE phases along grain boundaries.These phases result in the Zener pinning effect on grain boundaries and the reduction of DRX volume fraction.The texture type of the cylindrical bottom is<0001>‖ED and the cylindrical wall is<1010>‖ED,and the maximum pole intensity is 1.986 and 1.664,respectively.Results of the tensile test at room temperature show that combined improved strength and ductility of the cylindrical part is attained after introducing the MDF process.The ultimate tensile strength(UTS),yield strength(YS)and elongation are279 MPa,185 MPa and 12%at the bottom and 299 MPa,212 MPa and 20%at the wall.

Numerical simulation of mesoscopic cracking of cement-treated base material based on random polygon aggregate model

Cracking failure of cement-treated base(CTB)has always been the concern of highway constructors.Mesoscale cracking analysis is an important means to study the damage degradation mechanism,which is difficult to be characterized by experimental techniques alone.The objective of this paper is to develop a random aggregate modelling method to simulate the mesoscopic cracking of CTB material.A minimum rectangle area method was proposed to calculate the polygon aggregate size,which is closer to the sieving analysis than the average radius method.A buffer zone method was proposed to determine the distance between randomly generated polygon aggregates.Based on the proposed random algorithm,finite element method(FEM)was adopted to build the mesoscopic model of CTB including aggregate,mortar,interfacial transition zone(ITZ)and air voids.Laboratory tests were conducted to validate the numerical model.Then the sensitivity analyses were conducted to study the influencing factors on cracking behavior.The simulation results indicate that the higher aggregate content and the finer gradation lead to the increase of ITZ,thus reducing the cracking resistance of the CTB material.Low porosity content is able to significantly reduce the stress concentration and thus improves the cracking resistance.The research results of this paper could be used to guide the crack resistant design of CTB material.

1.5-m flat imaging system aligned and phased in real time

Flat optics has been considered promising for constructions of spaceborne imaging systems with apertures in excess of 10 m.Despite recent advances,there are long-existing challenges to perform in-phase stitching of multiple flat optical elements.Phasing the segmented planar instrument has remained at the proof of concept.Here,we achieve autonomous system-level cophasing of a 1.5-m stitching flat device,bridging the gap between the concept and engineering implementation.To do so,we propose a flat element stitching scheme,by manipulating the point spread function,which enables our demonstration of automatically bringing seven flat segments'tip/tilt and piston errors within the tolerance.With phasing done,the 1.5-m system has become the largest phased planar instrument ever built in the world,to our knowledge.The first demonstration of phasing the large practical flat imaging system marks a significant step towards fielding a 10-m class one in space,also paving the way for ultrathin flat imaging in various remote applications.

Noninvasive fluid bubble detection based on capacitive micromachined ultrasonic transducers

Ultrasonic fluid bubble detection is important in industrial controls,aerospace systems and clinical medicine because it can prevent fatal mechanical failures and threats to life.However,current ultrasonic technologies for bubble detection are based on conventional bulk PZT-based transducers,which suffer from large size,high power consumption and poor integration with ICs and thus are unable to implement real-time and long-term monitoring in tight physical spaces,such as in extracorporeal membrane oxygenation(ECMO)systems and dialysis machines or hydraulic systems in aircraft.This work highlights the prospect of capacitive micromachined ultrasonic transducers(CMUTs)in the aforementioned application situations based on the mechanism of received voltage variation caused by bubble-induced acoustic energy attenuation.The corresponding theories are established and well validated using finite element simulations.The fluid bubbles inside a pipe with a diameter as small as 8 mm are successfully measured using our fabricated CMUT chips with a resonant frequency of 1.1 MHz.The received voltage variation increases significantly with increasing bubble radii in the range of 0.5–2.5 mm.Further studies show that other factors,such as bubble positions,flow velocities,fluid medium types,pipe thicknesses and diameters,have negligible effects on fluid bubble measurement,demonstrating the feasibility and robustness of the CMUT-based ultrasonic bubble detection technique.

Phase constitutions,growth pattern and mechanical properties of Mg-1.4Gd-1.2Y-xZn-0.15Zr(at%) alloys

The effects of minor Zn(0.2 at%,0.4 at%,0.6 at%) on the microstructures and mechanical properties of Mg-1.4 Gd-1.2 Y-0.15 Zr(at%) alloys were systematically explored.Results reveal that increasing Zn content leads to the increase of the intergranular phases and the change of their composition from Mg24(Gd,Y)5 phase and(Mg,Zn)3(Gd,Y) phase to 18 R-LPSO phase and(Mg,Zn)3(Gd,Y) phase.Mg24(Gd,Y)5 phase is body-centered cubic structure and shares the same lattice constant with Mg24Y5 while(Mg,Zn)3(Gd,Y)phase is face-centered cubic structure with lattice constant of 0.72 nm,slightly lower than Mg3Gd.18RLPSO structure is identified to be monoclinic with c-axis not strictly vertical to the bottom surface but93.5°.The growth patterns of intergranular phases change from the divorced growth to coupled growth as compositions change.Moreover,the mechanical performance improves with Zn rising,ascribed to the decrease of brittle phases at grain boundaries and the increase of LPSO structure phases.

Microstructure evolution,mechanical properties and creep mechanisms of Mg-12Gd-1MM-0.6Zr(wt%)magnesium alloy

In this research,the microstructure evolution,mechanical properties,and creep mechanisms of Mg-12 Gd-1 MM-0.6 Zr(wt%)alloy under different conditions were systematically studied using scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),and tensile creep tests.Regarding the microstructure of the as-cast sample,the average grain size is about 42μm,and the eutectic compounds were determined to be Mg_(5)(Gd_(0.8)MM_(0.2)).During homogenization,these eutectic compounds gradually dissolve,and Mg_(12)MM particles are precipitated.During hot extrusion,complete dynamic recrystallization(DRX)occurs,resulting in equiaxial grains with an average grain size of about 12μm and the formation of streamlines consisting of Mg_(12)MM particles along the extrusion direction(ED).After T5 treatment(225℃for 7 h),a large number ofβ'(Mg_(7)Gd)phases are precipitated on the{11-20}αhabit plane and are interconnected,forming an interlaced network structure.The ultimate tensile strength(R_(m)=405 MPa)and yield strength(R_(P0.2)=288 MPa)of the T5 sample are significantly higher than those of the as-extruded sample(R_(m)=289 MPa,R_(P0.2)=185 MPa),but the elongation(A=4%)was remarkably lower than that of the as-extruded sample(A=18%).When crept at225℃under 100 MPa,the steady-state creep rates of the as-cast,as-extruded,and T5 samples are1.59×10^(-8),1.08×10^(-8),and 1.40×10^(-8)s^(-1),respectively,and their total strains within 100 h are respectively breaking,0.81%,and 0.92%,indicating that the as-extruded alloy exhibits the best creep resistance.TEM analysis reveals that,during the creep process of the T5 sample,theβ'particles coarsen and the precipitate-free zones(PFZs)widen,which increase the steady-state creep rate and the total strain within 100 h as compared with the as-extruded sample.

Hot deformation behavior and finite element simulation of Mg-8.3Gd-4.4Y-1.5Zn-0.8Mn alloy

To study the hot deformation behavior of Mg-8.3 Gd-4.4 Y-1.5 Zn-0.8 Mn(wt%) alloy,hot compression tests were conducted using a Gleeble-3500 thermal simulator at temperatures ranging from 653 to773 K,true strain rates of 0.001-1 s^(-1),and a deformation degree of 60%.Results of hot compression experiments show that the flow stress of the alloy increases with the strain rate.The true stress-true strain curves are corrected by correcting the effect of temperature rise in the deformation process.Activation energy,Q,equal to 287380 J/mol and material constant,n,equal to 4.59 were calculated by fitting the true stress-true strain curves.Then,the constitutive equation was established and verified via finite element simulation.Results of the hot processing map show that the probability of material instability increases with the degree of deformation,which indicates that the material is not suitable for large deformation in a single pass.On the whole,the alloy is appropriate for multipass processing with small deformation and a suitable processing temperature and strain rate are 733 K and 0.01 s-1,respectively.

Analysis of influence of the length of ground heat exchangers on the operation characteristics and economy of ground source heat pumps

A three-dimensional finite element dynamic simulation platform of the ground source heat pump system(GSHPS)is established.According to the outlet temperature of ground heat exchangers(GHEs)required by the code in summer and winter,the calculated minimum buried depth of GHEs meeting the requirements is 60 m,when the number of borehole is 9.By using the established platform,the annual operation performance and cost of the GSHPS under different buried pipe depths are studied.The results show that the deeper the buried depth of GHEs is,the better the heat exchange effect of GHEs is.Compared with the GHEs with 60 m buried depth,when the buried depth of GHEs is 65 m,70 m,75 m and 80 m,the average coefficient of performance(COP)of the unit increases by 4.1%,6.3%,7.7%and 8.2%in cooling period and 1.0%,1.6%,1.8%and 1.9%in heating period,respectively.Considering the performance and initial investment of the GHSPS comprehensively,the optimal buried depth of GHEs is 60 m.However,considering the performance the system and the total cost of the system running for 20 years comprehensively,the optimal buried depth of GHEs is 70 m.