Comparison of two reader modes of computer-aided diagnosis in lung nodules on low-dose chest CT scan

Low-dose computerized tomography(LDCT)scanning is of great significance for monitoring and management of pulmonary nodules on chest computerized tomography(CT).Nevertheless,the malignant potential of these nodules is often difficult to detect,especially for some smaller pulmonary nodules on LDCT images.Recent advances using the state-of-art computer-aided detection(CAD)system have attempted to address this problem by identifying small nodules that can be easily missed during clinical practice.CAD is used in two reading modes:Concurrent-reader(CR)mode or second-reader(SR)mode.In this study,we prospectively evaluated the efficiency of a CAD system's SR and CR modes in detecting pulmonary nodules on LDCT.We found that the SR mode improves pulmonary nodule detection regardless of the dose and ex-perience level,especially for interns in the low-dose setting.The CR mode maintains the sensi-tivity of SR mode while significantly decreasing reading times.

基于最小二乘法的组合梁斜拉桥施工控制研究

大跨度桥梁施工控制质量好与坏决定最终的成桥目标,因此在施工过程中及时修正与纠偏是十分重要的工作。本文以主跨340m组合梁斜拉桥为背景,基于最小二乘法理论对主梁线形、主梁应力分别进行二次多项式拟合,借助Matlab软件建立了实测与理论拟合函数,对比发现两者变化规律是一致的,实测拟合函数可用于指导现场施工,且具有较高的预测精度,总体预测误差在6%以内。实践证明,最小二乘法适用性强,精度高,在大跨度斜拉桥施工控制中可以取得很好效果。

Elevated Temperature Strength of TiC_(p)/W Composites

The elevated temperature mechanical properties of TiCp,/W composites produced using powder metallurgical technique were investigated. Results show that with increasing temperature, the strength of TiCp/W composites increases gradually and reaches its maximum value at 1000℃, which is much higher than that at room temperature. The strengthening mechanisms at high temperature are attributed to dislocation strengthening and load transfer between matrix and particles.

Phase transition of multi-component(TiZrVNb)C ceramics—Part II:From single phase to multiple phases via adjusting V content

To address the relatively mediocre mechanical properties of single-phase multi-component carbide ceramics,a phase transition from a single phase to multiple phases was proposed to achieve superior mechanical properties.A series of(TiZrV_(x)Nb)C_(0.8) ceramics with different V contents were fabricated by spark plasma sintering(SPS).The influence of the V content on the phase composition,microstructural evolution,and mechanical properties was investigated in detail.The transition behavior from a single phase to multiple phases is discovered and discussed.The formation of the Zr-rich phase and Zr-poor phase can be attributed to the increase in lattice distortion and mixed enthalpy caused by the addition of V.A nanometer lamellar structure with a semi-coherent interface obtained via in situ decomposition is reported for the first time in multi-component carbide ceramics.The semi-coherent interfaces with high dislocation density and strain concentration effectively improve the mechanical properties,grain refinement,and multi-phase formation.The optimal comprehensive mechanical properties of the Vickers hardness(26.3 GPa),flexural strength(369 MPa),and fracture toughness(3.1 MPa·m^(1/2))were achieved for the sample with 20 mol%V.

Phase transition of multi-component(TiZrVNb)C ceramics—Part I:Phase decomposition induced by carbon content

Phase decomposition can effectively enhance the mechanical properties of carbide ceramics and can overcome the difficulty of enhancing the mechanical properties of single-phase multicomponent carbide ceramics.In this work,a series of nonstoichiometric(TiZrVNb)Cx ceramics were prepared by spark plasma sintering(SPS)at different temperatures.The effects of the carbon content on the phase composition,microstructure evolution,and mechanical properties were investigated in detail.Phase decomposition occurred with decreasing carbon content.Two different solid solutions of(Ti,V)-rich and Zr-rich phases formed from the decomposition of equimolar single-phase solid solutions,namely,the Zr-poor phase and Zr-rich phase,respectively.The distribution of Nb element is relatively uniform.The semicoherent interfaces between the Zr-poor phase and the Zr-rich phase can harden and strengthen effectively under the synergistic effect of grain refinement.Ceramics with phase decomposition structures have apparent advantages compared to single-phase high-entropy carbides.This work provides an important train of thought for the microstructure tailoring and properties optimization of multi-component carbide ceramics.

Microstructure and mechanical properties of(TiZrNbTaMo)C high-entropy ceramic

A high-entropy(Ti Zr Nb Ta Mo)C ceramic has been successfully fabricated by hot pressing the newlysynthesized quinary carbide powder to investigate its microstructure and mechanical properties.The carbothermal reduction process of equimolar quinary metallic oxides at 1500℃for 1 h generates a carbide powder mixture,which consists mainly of Ta C-and Zr C-based solid solutions.The as-synthesized powder was then sintered to form a single-phase high-entropy ceramic by a two-step hot pressing at 1850℃for1 h and 2100℃for 0.5 h,respectively.The high-entropy ceramic exhibits a fine grain size of about 8.8μm,a high compositional uniformity and a high relative density of 98.6%by adding Mo as the strategic main component.The measured nanohardness values of(TiZrNbTaMo)C ceramic are 25.3 GPa at 9.8 N and 31.3 GPa at 100 m N,respectively,which are clearly higher than those of other available high-entropy carbide ceramics.

Review and Development of Electric Motor Systems and Electric Powertrains for New Energy Vehicles

This paper presents a review on the recent research and technical progress of electric motor systems and electric powertrains for new energy vehicles.Through the analysis and comparison of direct current motor,induction motor,and synchronous motor,it is found that permanent magnet synchronous motor has better overall performance;by comparison with converters with Si-based IGBTs,it is found converters with SiC MOSFETs show significantly higher efficiency and increase driving mileage per charge.In addition,the pros and cons of different control strategies and algorithms are demonstrated.Next,by comparing series,parallel,and power split hybrid powertrains,the series-parallel compound hybrid powertrains are found to provide better fuel economy.Different electric powertrains,hybrid powertrains,and range-extended electric systems are also detailed,and their advantages and disadvantages are described.Finally,the technology roadmap over the next 15 years is proposed regarding traction motor,power electronic converter and electric powertrain as well as the key materials and components at each time frame.

Densification,microstructure and mechanical properties of multicomponent(TiZrHfNbTaMo)C ceramic prepared by pressureless sintering

A multicomponent(TiZrHfNbTaMo)C ceramic has been fabricated by pressureless sintering at temperatures from 2100℃to 2500℃,using an equimolar multicomponent carbide powder synthesized by carbothermal reduction as the starting material.Influence of sintering temperature on densification,microstructure and mechanical properties of the ceramics was investigated.The relative density increases with increasing sintering temperature,and a nearly fully dense sample is achieved by pressureless sintering at 2500℃.Average grain size increases from 3.7 to 15.2μm with increasing sintering temperature from 2300 to 2500℃.The(TiZrHfNbTaMo)C ceramic sintered at 2400℃exhibits a single phase fcc structure with homogeneous chemical composition,an average grain size of 7.0μm and a relative density of96.5%,while its measured hardness is 33.2 GPa at 100 mN and 23.2 GPa at 9.8 N.

Low thermal conductivity of dense(TiZrHfVNbTa)C_(x) high-entropy carbides by tailoring carbon stoichiometry

Transition metal carbides are promising candidates for thermal protection materials due to their high melting points and excellent mechanical properties.However,the relatively high thermal conductivity is still a major obstacle to its application in an ultra-high-temperature insulation system.In this work,the low thermal conductivity of dense(TiZrHfVNbTa)Cx(x=0.6-1)high-entropy carbides has been realized by adjusting the carbon stoichiometry.The thermal conductivity gradually decreases from 10.6 W·m^(−1)·K^(−1) at room temperature to 6.4 W·m^(−1)·K^(−1) with carbon vacancies increasing.Due to enhanced scattering of phonons and electrons by the carbon vacancies,nearly full-dense(97.9%)(TiZrHfVNbTa)C_(0.6) possesses low thermal conductivity of 6.4 W·m^(−1)·K^(−1),thermal diffusivity of 2.3 mm^(2)·s^(−1),as well as electrical resistivity of 165.5μΩ·cm.The thermal conductivity of(TiZrHfVNbTa)C_(0.6) is lower than that of other quaternary and quinary high-entropy carbide ceramics,even if taking the difference of porosity into account in some cases,which is mainly attributed to compositional complexity and carbon vacancies.This provides a promising route to reduce the thermal conductivity of high-entropy carbides by increasing the number of metallic elements and carbon vacancies.

Microstructural evolution of h-BN matrix composite ceramics with La-Al-Si-O glass phase during hot-pressed sintering

BN/La-Al-Si-O composite ceramics were fabricated by hot-pressed sintering using hexagonal boron nitride(h-BN),lanthanum oxide(La_(2)O_(3)),aluminia(Al_(2)O_(3)),and amorphous silica(SiO_(2))as the raw materials.The effects of sintering temperature on microstructural evolution,bulk density,apparent porosity,and mechanical properties of the h-BN composite ceramics were investigated.The results indicated that La-Al-Si-O liquid phase was formed during sintering process,which provided an environment for the growth of h-BN grains.With increasing sintering temperature,the cristobalite phase precipitation and h-BN grain growth occurred at the same time,which had a significant influence on the densification and mechanical properties of h-BN composite ceramics.The best mechanical properties of BN/La-Al-Si-O composite ceramics were obtained under the sintering temperature of 1700℃.The elastic modulus,flexural strength,and fracture toughness were 80.5 GPa,266.4 MPa,and 3.25 MPa·m^(1/2),respectively.

Grain growth kinetics and densification mechanism of(TiZrHfVNbTa)C high-entropy ceramic under pressureless sintering

The grain growth kinetics and densification mechanism of(TiZrHfVNbTa)C high-entropy carbide ceramic are investigated in this work.A single phase carbide with a rock-salt structure is formed until 2300°C,below which an apparent aggregation of V,Zr and Hf exists.It is associated with the slow diffusion rate of V element as well as the relatively poor solubility of VC in HfC(as well as ZrC).The grain growth mechanism gradually changes from surface diffusion to volume diffusion and then grain boundary diffusion with increasing sintering temperature.This is attributed to the variation of activation energy of grain growth.The densification mechanism is principally dominated by the mass transport through lattice diffusion with the activation energy of 839±53 k J/mol.Through the design of two-step sintering,it is verified that the solid solution formation can effectively promote the densification process.

Reactive sintering of dual-phase high-entropy ceramics with superior mechanical properties

1. Introduction The requirements for the performance of materials have become increasingly stringent in recent years, with the rapid development of aerospace, machinery, metallurgy, nuclear energy,chemical industry, and military industry [1,2], and traditional single-phase materials are gradually revealing disadvantages due to the contradiction between demanding service environments and simple material design.

Insights into grain boundary segregation and solubility limit of Cr in(TiZrNbTaCr)C

Dense(TiZrNbTaCr)C with Cr segregation along grain boundaries(GBs)has been first proposed and fabri-cated by pressureless sintering at 1800-2000℃,utilizing the self-synthesized carbide powders obtained by carbothermal reduction.Cr segregation along GBs is successfully realized as expected via optimizing the initial Cr content.When Cr content is more than 11.12 at.%,Cr addition is excessive and results in Cr-rich second phase formation at triple junctions.To analyze the Cr solubility dependence on tempera-ture and initial Cr content,the Cr content in(TiZrNbTaCr)C grains is investigated by EDS.The solubility limit of Cr in(TiZrNbTaCr)C is about 3.8 at.%at 1900℃.Finally,Vickers hardness of all the samples is measured to assess the mechanical property of(TiZrNbTaCr)C ceramics.The basic understanding of the Cr solubility limit and GB segregation feature in(TiZrNbTaCr)C have been preliminarily clarified,which may pave a potential way to design and tailor microstructure and GB feature of(TiZrNbTaCr)C for the purpose of enhancing its properties in the future.

The highest melting point material:Searched by Bayesian global optimization with deep potential molecular dynamics

The interest in refractory materials is increasing rapidly in recent decades due to the development of hypersonic vehicles.However,the substance that has the highest melting point(Tm)keeps a secret,since precise measurements in extreme conditions are overwhelmingly difficult.In the present work,an accurate deep potential(DP)model of a Hf-Ta-C-N system was first trained,and then applied to search for the highest melting point material by molecular dynamics(MD)simulation and Bayesian global optimization(BGO).The predicted melting points agree well with the experiments and confirm that carbon site vacancies can enhance the melting point of rock-saltstructure carbides.The solid solution with N is verified as another new and more effective melting point enhancing approach for HfC,while a conventional routing of the solid solution with Ta(e.g.,HfTa_(4)C_(5))is not suggested to result in a maximum melting point.The highest melting point(~4236 K)is achieved with the composition of HfCo.638No.271,which is~80 K higher than the highest value in a Hf-C binary system.Dominating mechanism of the N addition is believed to be unstable C-N and N-N bonds in liquid phase,which reduces liquid phase entropy and renders the liquid phase less stable.The improved melting point and less gas generation during oxidation by the addition of N provide a new routing to modify thermal protection materials for the hypersonic vehicles.

Texture and anisotropy of hot-pressed h-BN matrix composite ceramics with in situ formed YAG

Textured hexagonal boron nitride(h-BN)matrix composite ceramics were prepared by hotpressing using different contents of 3Y_(2)O_(3)–5Al_(2)O_(3)(molar ratio of 3:5)as the sintering additive.During hot-pressing,the liquid Y_(3)Al_(5)O_(12)(YAG)phase showing good wettability to h-BN grains was in situ formed through the reaction between Y_(2)O_(3) and Al_(2)O_(3),and a coherent relationship between h-BN and YAG was observed with[010]_(h-BN)//[111]_(YAG) and(002)_(h-BN)//(321)_(YAG).In the YAG liquid phase environment formed during hot-pressing,plate-like h-BN grains were rotated under the uniaxial sintering pressure and preferentially oriented with their basal surfaces perpendicular to the sintering pressure direction,forming textured microstructures with the c-axis of h-BN grains oriented parallel to the sintering pressure direction,which give these composite ceramics anisotropy in their mechanical and thermal properties.The highest texture degree was found in the specimen with 30 wt%YAG,which also possesses the highest anisotropy degree in thermal conductivity.The aggregation of YAG phase was observed in the specimen with 40 wt%YAG,which resulted in the buckling of h-BN plates and significantly reduced the texture degree.

Cost-reduction strategies in massive genomics experiments

Many modern biology studies require deep, whole-genome sequencing of hundreds to thousands of samples. Although persamplecosts have dramatically decreased, the total budget for such massive genome sequencing constitutes a significantbarrier for poorly funded labs. The costly lab tools required for genomics experiments further hinder such studies. Here, weshare two strategies for extensively reducing the costs of massive genomics experiments, including miniaturization of theNEBNext Ultra II FS DNA Library Prep Kit for Illumina (reducing the per-sample total costs to ~ 1/6 of that charged byservice providers) and in-lab 3D model-designing of genomics tools. These strategies not only dramatically release fundingpressure for labs, but also provide students with additional training in hands-on genomics and 3D-model-designing skills,demonstrating the high potential for their application in genomics experiments and science education.

Mechanical properties,thermal conductivity and defect formation energies of samarium immobilization in Gd_(2)Zr_(2)O_(7):First-principles study and irradiation experiment

A density functional theory(DFT)study was employed to investigate the mechanical property,thermal conductivity,Debye temperature,electronic structure and defect chemistry of(Gd_(1-x)Sm_(x))_(2)Zr_(2)O_(7).All the(Gd_(1-x)Sm_(x))_(2)Zr_(2)O_(7) compounds exhibit an excellent structural and mechanical stability(Gd_(0.25)Sm_(0.75))_(2)Zr_(2)O_(7) has the lowest Young’s modulus of 213.7 GPa,the largest Possion’s ratio of 0.292,the lowest Debye temperature of 491.8 K and the lowest thermal conductivity.The calculated thermal conductivities of(Gd_(1-x)Sm_(x))_(2)Zr_(2)O_(7) are 1.17-1.21 W/(m·K)by the Clark’s model and 1.32-1.36 W/(m·K)by the Cahall’s model,respectively.The formation energies of O vacancies at 48f site are negative,which increase with the Sm content,however,the formation energies of O vacancies at 8b site are almost invariable.In addition,Sm partly occupying the Gd-site reduces distinctly the formation energies of defects such as A-site vacancies,cation antisite defects,anion Frenkel pairs of oxygen at 8b site and cation interstitials,which suggests that Sm-doped Gd_(2)Zr_(2)O_(7),especially equimolar GdSmZr_(2)O_(7),has a better irradiation tolerance.After the 16 MeVTa-ion irradiation at a fluence of 1×10^(14) or 2×10^(14) ions/cm^(2),the crystal structure of GdSmZr_(2)O_(7) transforms from pyrochlore to a defect fluorite without obvious amorphous phase.

Dislocation Behavior in ZrC Particles during Elevated Temperature Compressive Deformation of a 30 vol.% ZrC_p/W Composite

A 30 vol.% ZrCp/W composite has been deformed in compression in the temperature range of 1200-1600℃.Dislocation nucleation mechanism in ZrC particles is discussed by analyzing the harmonious deformation between tungsten-matrix and ZrC particles.Thermal activation apparently increases the mobility of screw segments,resulting in the formation of many kinetics jogs and thermodynamics jogs above 1300℃.The formation mechanisms of the dislocation configurations are studied.

Ecological significance and risks of mineral licks to mammals in a nature reserve on the Eastern Qinghai-Tibet Plateau

Mineral licks are important components of terrestrial ecosystems that have special value to the maintenance of fluid balance of mammals,by providing them with essential mineral nutrients such as sodium,calcium,and magnesium.In the Anzihe Nature Reserve,southwest China,seven species of ungulates and one species of primates were frequently observed visiting the mineral licks in high densities.As a consequence,mineral licks have attracted illegal hunters and facilitated the spread of parasites and diseases,leading to a depletion of local populations.Therefore,we suggest that regions with abundant mineral licks should be designated as key protected areas in the Anzihe Nature Reserve and relevant zones for animal health surveillance.