固相应力在肿瘤中的研究进展

近几十年来,肿瘤微环境(TME)作为肿瘤发生、发展、免疫逃避和治疗反应的关键而成为肿瘤研究的热点。而作为肿瘤微环境中的物理特性,“固相应力”可由周围正常组织从肿瘤外部施加产生,也可由肿瘤本身生长而引起。随着肿瘤的生长,固相应力会通过生化-物理机制破坏周围组织的结构和功能,并促进肿瘤的发生和肿瘤治疗的抗性。该文针对固相应力在肿瘤中的发生机制及相关进展进行综述,探讨恶性肿瘤生物学和物理学之间的联系,为新型药物研发和肿瘤治疗策略制定提供参考。

基于人工神经网络的非均匀固相应力模型

最小多尺度理论EMMS已经被引入多相质点网格法MP-PIC中,建立了非均匀EMMS固相应力模型.但现有的非均匀固相应力模型计算中,中间步骤繁琐且花费时间长.采用人工拟合的方式能获得非均匀固相应力表达式,但需要人为确定拟合变量和拟合函数,且针对于非均匀固相应力这种高度非线性函数所得到的拟合精度不高、用于MP-PIC模拟的结果相比原EMMS固相应力模型结果存在偏差.针对上述问题,本文提出通过机器学习的方法,规避对固相体积分数的局部分布情况的表征,并提出和建立能考虑颗粒浓度详细分布的人工神经网络ANN固相应力模型.首先,基于局部颗粒浓度和颗粒非均匀分布指数建立了双变量的ANN固相应力模型;进一步将当前网格及其周边网格颗粒浓度组成的序列来详细表征颗粒浓度分布,并建立相应的ANN固相应力模型.然后,将两种模型与EMMS固相应力模型进行了对比并测试了网格分辨率和粗化率对模型的影响.研究表明:基于ANN固相应力模型的模拟结果对EMMS固相应力模型结果有较高的还原度,同时具有一定的网格分辨率无关性和粗化率无关性.

相应力对双相钢Bauschinger效应的影响

本文根据各向同性和各向异性硬化模型,利用有限单元法计算了双相钢的反向(压缩)流动曲线.计算结果清楚地揭示了由塑性变形不均匀产生的相应力对Bauschinger 效应的影响规律:使反向曲线在较低的载荷下进入屈服,初始流动阶段具有较高的硬化率,不产生永久软化.

CFD-DEM-IBM方法探究流化床倾斜挡板内构件受力特性

在密相床层内安装内构件可显著改善工业流化床的流化质量、强化气固传质和提高化学反应效率。由于长时间受气体和颗粒的挤压和冲击,流化床内构件可能会发生变形或断裂。为实现流化床内构件设计的科学性,确保其长周期可靠性,需要明确其受力机理与不同操作条件下受力特性。利用粗粒化CFD-DEM-IBM方法,实现了利用笛卡儿网格模拟流化床中倾斜挡板内构件受力特性的定量模拟,该方法拓展原有挡板应力统计方法,获得了不同倾斜角度对挡板所受应力的定量影响规律。模拟所得挡板受力随时间的演化曲线与实验报道较为一致,在流化床启动阶段会出现较大的峰值,同时成功复现在启动阶段的峰值受力总体与挡板在水平面上的投影面积成正比。模拟结果显示,在启动阶段,挡板受力中颗粒挤压作用力占主导,但在流化阶段,除颗粒作用力达到极大值外的大部分时间中挡板受到的气相压差力要大于颗粒作用力。当挡板倾斜角度较小时,挡板受力较大但抑制床内返混效果较好,因此在工业流化床内构件设计中应兼顾强化传递及长周期可靠性的需求,当挡板倾斜角度较小时应选择强度大的挡板材料。

耐磨胶粘涂层的微观热应力分析

按球对称模型分别分析了胶层基体及填充粒子中的微观热应力，同时对经历了不同温差循环的胶层进行了显微观察。取粒子中心为坐标原点时，研究表明，两相材料中各相热应力均在界面达到最大值，降温温差△t1在45℃左右就会引起界面附近胶层开裂。升温会使界面附近胶层屈服，计算出屈服升温温差△t2＝88℃。

综放工作面粉尘浓度空间分布规律的数值模拟及其应用

针对粉尘采样器测尘法不能全面反映工作面作业空间粉尘浓度的缺点,用数值模拟的方法对综放工作面粉尘浓度的三维分布规律进行研究。为此,根据综放工作面气体-粉尘流动的特性,运用颗粒相的动力学理论,推导了颗粒相应力的表达式,实现了求解粉尘浓度空间分布规律的k-ε-Θ-kp双流体封闭方程组的数学建模。采用基于同位网格的SIMPLE算法,利用Fluent软件对综放工作面粉尘浓度空间分布规律进行了数值模拟。根据模拟结果指导综放液压支架喷雾降尘装置的优化设计,取得了很好的降尘效果。

饱和多孔介质材料的应变局部化萌生条件

在单相介质和非渗流饱和多孔介质应变局部化萌生条件的基础上,应用饱和多孔介质控制方程和Liapunov稳定理论,导出了渗流条件下的固相应力-应变描述和有效应力-应变描述的多孔介质固相部分的应变局部化的萌生条件。不同应力描述下的萌生条件的形式有一定变化。应用简单算例,讨论了Terzaghi有效应力描述的应变局部化萌生条件中两种固、液相对运动特例下的饱和多孔介质应变局部化破坏的形式。

饱和多孔介质中骨架的应变局部化萌生条件

应用饱和多孔介质控制方程和Liapunov稳定理论,导出了固相应力和有效应力描述的多孔介质骨架应变局部化的萌生条件.不同应力形式表达的多孔介质基体的控制方程,相应的应变局部化萌生条件的表达形式也不尽相同,其原因源于骨架本构中固液两相之间相互作用的不同描述.应用得出的Terzaghi有效应力描述的应变局部化萌生条件,可以理论解释多孔介质中固、液两相不同相对运动出现的破坏方式,如管涌、滑坡和泥石流.应用简单算例说明了应变局部化条件的具体实施方法.

Effect of stress on microstructures of creep-aged 2524 alloy

Microstructures of creep-aged 2524 （A1-4.3Cu-1.5Mg） aged at 170 ℃ with various stresses （0, 173 and 250 MPa） were studied on a creep machine. Ageing hardness curves under various stresses were plotted and the corresponding microstructures were characterized by transmission electron microscopy （TEM）. The results show that the value of peak hardness is increased, while the time to reach the peak hardness is reduced under an external stress. Meanwhile, the length of S（Al2CuMg） phase is shorter and the number density of S phases is larger in the creep-aged alloy. The predominant contribution to the peak hardness can be ascribed to the GPB zones with an elastic stress.

Microstructure and property of stress aged Al-Cu single crystal under various applied stresses

The stress aging behavior of Al-Cu alloy under various applied stresses, i.e., elastic stress, yield stress and plasticdeformation stress, was investigated using single crystals. The resulting microstructures and the yield strength were examined bytransmission electron microscopy （TEM） and compression tests, respectively. The results indicate that an elastic stress of 15 MPa ishigh enough to influence the precipitation distribution of θ′ during aging at 180℃. The applied stress loading along [116]Aldirection results in increased number density of θ′ on （001）Al habit planes. This result becomes more significant with increasingapplied stress and leads to lower yield strength of Al-Cu single crystals during aging. Moreover, the generation of the preferentialorientation of θ′ was discussed by the effect of the dislocation induced by applied stress as well as the role of the misfit between theθ′-precipitate and Al matrix. The results are in agreement with the effect of the latter one.

Reaction mechanisms of low-grade molybdenum concentrate during calcification roasting process

The effects of Ca-based additives on roasting properties of low-grade molybdenum concentrate were studied. The resultsshow that calcium-based additives can react with molybdenum concentrate to form CaSO4 and CaMoO4. The initial oxidationtemperature of MoS2 is 450℃, while the formation of CaMoO4 and CaSO4 occurs above 500℃. The whole calcification reactionsare nearly completed between 600 and 650℃. However, raising the temperature further helps for the formation of CaMoO4 but isdisadvantageous to sulfur fixing rate and molybdenum retention rate. Calcification efficiency of Ca-based additives follows theorder： Ca（OH）2〉CaO〉CaCO3. With increasing the dosage of Ca（OH）2, the molybdenum retention rate and sulfur-fixing rate rise, butexcessive dosages would consume more acid during leaching process. The appropriate mass ratio of Ca（OH）2 to molybdenumconcentrate is 1：1. When roasted at 650 ℃ for 90 min, the molybdenum retention rate and the sulfur-fixing rate of low-grademolybdenum concentrate reach 100% and 92.92%, respectively, and the dissolution rate of molybdenum achieves 99.12% withcalcines being leached by sulphuric acid.

EFFECTS OF MICRO STRESS FIELD ON MARTENSITE TRANSFORMATION CHARACTERISTICS IN Ni-Ti-Nb BASED SHAPE MEMORY ALLOYS

The transformation behavior of Ni Ti Nb based alloys was analysed.The absence of R phase transformation in these alloys is related to the stress field in the NiTi matrix.The thermal mismatch stress was calculated by the Eshelby method in Ni Ti Nb alloys.The results show that the mean matrix elastic stress field is isostatic tensile,there is no preferred stress in [111] B 2 direction.The mean matrix stress from the thermal misfit between NiTi matrix and β Nb particle is too small to induce dislocations.All the factors tend to inhibit R phase transformation.

纳米颗粒聚团流化特性的数值模拟

基于气固两相流体动力学和流态化理论,建立气体纳米颗粒气固两相双流体模型.模型中采用了Jung&Gidaspow[1]测量的固相应力模量,并应用了王垚,金涌,魏飞[2]提出的聚团曳力系数计算模型.对纳米颗粒聚团的流化过程进行了数值模拟,得到纳米颗粒的流化特性.模拟得出的床层膨胀比与文献中实验的结果较为接近.

Time-temperature-property curves for quench sensitivity of 6063 aluminum alloy

The quench sensitivity of 6063 alloy was investigated via constructing time-temperature-property（TTP） curves by interrupted quenching technique and transmission electron microscopy（TEM） analysis.The results show that the quench sensitivity of 6063 alloy is lower than that of 6061 or 6082 alloy,and the critical temperature ranges from 300 to 410℃ with the nose temperature of about 360℃.From TEM analysis,heterogeneous precipitate β-Mg2Si is prior to nucleate on the（AlxFeySiz） dispersoids in the critical temperature range,and grows up most rapidly at the nose temperature of 360℃.The heterogeneous precipitation leads to a low concentration of solute,which consequently reduces the amount of the strengthening phase β＇＇ after aging.In the large-scale industrial production of 6063 alloy,the cooling rate during quenching should be enhanced as high as possible in the quenching sensitive temperature range（410-300℃） to suppress the heterogeneous precipitation to get optimal mechanical properties,and it should be slowed down properly from the solution temperature to 410℃ and below 300℃ to reduce the residual stress.

Thermodynamic modelling and applications of Ce-La-O phase diagram

The Ce-La-O system was investigated via experiments and thermodynamic modeling. A series of CeO2-LaO1.5 mixtures were prepared by co-precipitation technique and examined by X-ray diffraction. Mutual solubilities between LaO1.5 and CeO2 at 1273 K were determined. Using the new experimental data together with literature information, a set of self-consistent thermodynamic parameters for the CeO2-LaO1.5 system were optimized. Combined with thermodynamic descriptions of Ce-O and La-O systems from literature, several property diagrams of Ce-La-O system were calculated and used to explain oxidation process of the Ce-La alloys. The fluorite phase is the unique oxidation products for most of the Ce-La alloys.

Polarization-Insensitive Silica on Silicon Arrayed Waveguide Grating Design

A new technology for fabrication of silica on silicon arrayed waveguide grating (AWG) based on deep etching and thermal oxidation is presented.Using this method,a silicon layer is remained at the side of waveguide.The stress distribution and effective refractive index of waveguide fabricated by this approach are calculated using finite element and finite difference beam propagation method,respectively.The results of these studies indicate that the stress of silica on silicon optical waveguide can be matched in parallel and vertical direction and AWG polarization dependent wavelength (PDλ) can be reduced effectively due to side-silicon layer.

Cracking mechanism in as-cast GH4151 superalloy ingot with high γ'phase content

The fundamental mechanism of the cracking formation was investigated for the as-cast GH4151 superalloy.By analyzing the characteristics of cracking,the cracking mechanism was determined to be the cold crack formed during the cooling process.And cold cracking is closely related to severe segregation,complex precipitates and uneven γ'phase distribution.During cooling process,cracks were generated around the precipitates due to their different linear shrinkage coefficients.The annealing treatment process controlling the residual stress,the size and morphology of γ'phase was proposed.The annealing treatment plays a role in reducing residual stress through decreasing the thermal gradient and controlling the size distribution of γ'phase to reduce the strain concentration around the precipitate phases.

Influence of processing parameters on deposition characteristics of Inconel 625 superalloy fabricated by laser solid forming

A series of single track clads of Inconel 625 alloy were fabricated by laser solid forming.To achieve the high dimensional accuracy and excellent mechanical properties,the effect of processing parameters on the geometry,the formation of Laves phase and the residual stress was investigated.The results show that laser power and scanning speed had a dramatical influence on the width and height of single-track clads.According to the columnar to equiaxed transition curve of Inconel 625,the grain morphology can be predicted during the LSF process.With the increasing laser power and the decreasing scanning speed,the segregation degree of Si,Nb,Mo,the volume fraction and size of Laves phase increased.Vickers indentation was used to demonstrate that optimizing processing parameter can achieve the minimum residual tensile stress.

Physical simulation of rock burst induced by stress waves

The behavior of stress wave propagation in rock walls and the process of rock bursts were simulated by application tests of material similar to rock. Results show that 1) the attenuation characteristics of stress waves were related to the material proper-ties, stress waves attenuate more quickly in soft material and 2) when the explosion load was applied at the top of the roadway, the number and the length of the cracks increased with a decrease in the distance between the explosive point and roof of the roadway. When the distance was 280 mm, only some chips appeared near the source, when the distance was 210 mm, some small cracks started to appear near the road-rib and when the distance was reduced to 140 mm, larger cracks appeared at the road-rib. It can be concluded that, under a given stress the number of cracks is closely related to the intensity of stress waves. The cracks in the sur-rounding rock can be reduced by controlling the intensity of the stress waves and rock bursts can be avoided to some extent by pre-venting the formation of layered crack structures. A new experimental approach has been provided for studying rock bursts by using physical simulation.

Phase Field Simulation of Intragranular Microvoids Evolution Due to Surface Diffusion in Stress Field

Based on the bulk free energy density and the degenerate mobility constructed by the quartic double-well potential function,a phase field model is established to simulate the evolution of intragranular microvoids due to surface diffusion in a stress field.The corresponding phase field governing equations are derived.The evolution of elliptical microvoids with different stressesΛ,aspect ratiosβand linewidths hˉis calculated using the mesh adaptation finite element method and the reliability of the procedure is verified.The results show that there exist critical values of the stressΛc,the aspect ratioβc and the linewidth hˉc of intragranular microvoids under equivalent biaxial tensile stress.When Λ≥Λ_(c),β≥β_(c) or h≤h_(c),the elliptical microvoids are instable with an extending crack tip.WhenΛ<Λ_(c),β<β_(c) or hˉ>h_(c),the elliptical microvoids gradually cylindricalize and remain a stable shape.The instability time decreases with increasing the stress or the aspect ratio,while increases with increasing the linewidth.In addition,for the interconnects containing two elliptical voids not far apart,the stress will promote the merging of the voids.