Enrichment characteristic of carbon atoms in solid-liquid zone of high carbon steel under different directional solidification rates

To reveal the formation mechanism and main influencing factors of C-segregation in high carbon steel under different solidification rates(40,80,160,200 and 320μm·s^(-1)),the enrichment characteristics of carbon atoms in the solid-liquid zone of Fe-0.61%C steel were studied using a zone melting liquid metal cooling apparatus and electron probe microanalysis.The relationships among micro-segregation of carbon atoms,solid-liquid interface morphology and solidification rate were fully discussed.The results show that large dendrite spacing and a slow-moving dendritic interface create less resistance and more time for the migration of interdendritic carbon atoms to liquid zone.This results in the continuous enrichment of carbon atoms in liquid zone,further expands the solid-liquid temperature range,prolongs the solidification time of molten steel,and causes the formation of carbon micro-segregation at the solidification end as the solidification rate is 40μm·s^(-1).Conversely,abundant and elongated secondary dendrite arms with small spacing seriously impede the diffusion of interdendritic carbon-rich molten steel to liquid zone.As a result,there is only obvious dendrite segregation,but little difference in the carbon content along the solidification direction as solidification rate exceeds 200μm·s^(-1).

基于探测区域的多预警机协同探测部署方法

单架预警机在执行任务过程中通常会面临探测区域有限、雷达情报掌握不连续、抗干扰能力弱、安全性不强等问题,为了适应复杂多变的未来战场环境以及对抗"四大威胁"的需要,多预警机协同探测是必然趋势。多预警机协同探测的部署是多预警机协同探测首先需要解决的问题,文中由探测任务区域驱动,提出了一种基于并立组合航线模式的多预警机协同探测部署方法。该方法不仅能对任务区域进行空域上的稳定覆盖,发挥现有装备最大效费比;还能减小目标同时进入相邻两架预警机雷达多普勒盲区的概率,提高情报质量。仿真实验证明了该方法的有效性。

Al—5％Cu合金固液共存区的粘性、弹性和塑性变形行为

在自行研制的装置上研究了Al-5％Cu合金固液共存区拉伸过程的粘性、弹性和塑性变形规律。讨论了不同条件下上述变形的变化特点。

Al—Si合金固液共存区流变行为的实验研究

在自行研制的实验装置上研究了Al-Si合金固液共存区的流变行为。测试了Al-Si合金的流变参数值,考察了流变参数与温度的关系,建立了描述合金流变行为的流变模型和本构方程,在不同的温度区间流变模型可进行简化。

Al—Cu合金固液共存区的非线性流变模型

本文建立了 Al—Cu 合金固液共存区的非线性流变模型.并同线性模型进行了对比。结果表明,在断裂应力附近并随蠕变量的增加,非线性流变行为显著。

合金凝固温区的流变模型及其微分型本构方程

通过高温流变实验，揭示了合金凝固温区不同阶段的流变特性；提出准液相及准固相为五元件流变模型，而其过渡温区为六元件流变模型．并获得了相应的微分型本构方程．

废弃石油井对煤层安全开采的影响评价

在煤炭资源与石油资源共储区,先期开采石油遗留的许多废弃石油井会严重影响煤炭的后续安全高效开采。为探究废弃石油井对井周围煤层安全开采的影响程度,根据神华宁煤双马煤矿内废弃石油井及其周围煤岩层的实际情况,运用层次分析法和模糊综合评价法针对废弃石油井对煤层安全开采的影响程度进行了评价。结果表明:废弃石油井对煤层安全开采的危害主要分为油气涌入、水涌入和顶板灾害3类,其中油气灾害对煤层安全开采的威胁最大;依据最大隶属度原则,油气、水和顶板灾害因素对煤层安全开采的影响等级分别为严重、较严重和轻微;废弃石油井对煤层安全开采综合影响的模糊综合评价向量为(0.0943,0.2245,0.3009,0.6490,0.6071),依据最大隶属度原则,其影响等级为严重。该研究可为双马煤矿及全国类似煤矿的安全高效采煤提供理论指导。

Microhabitat Segregation of Parapatric Frogs in the Qinling Mountains

Coexistence mechanisms for species with similar ecological traits and overlapping geographic distributions are basic questions in ecology and evolutionary biology. Specific habitat requirements often limit distribution range as well as facilitate partitioning resource utilization in ecological similar species. Understanding niche segregation and differences in microhabitat utilization can contribute to identifying coexistence mechanisms between parapatric species. Feirana quadranus and F. taihangnica are two closely related frog species with parapatric geographic ranges and an elongated contact zone within the Qinling Mountains, which is an important watershed for East Asia. Here, we analysed the difference in microhabitat utilization between the two frog species and explored the key ecological factors that induced their microhabitat differentiation based on quadrats sampled in the contact zone. Our comparison of twenty environmental variables showed that both species used microhabitats with alkalescent warm water and gentle slope conditions. The principal component analysis indicated that climate-related variables, vegetation conditions, and river width were the important factors for microhabitat utilization of these species. These findings contribute to our understanding on the coexistence mechanisms of these two related and parapatric Asian mountain frog species. This study can also be helpful for identifying target habitats to conduct conservation actions and management strategies effectively in the face of environmental changes.

具有交错扩散和保护区域的Ivlev型捕食模型的共存解

主要研究一个食饵具有保护区域的Ivlev型捕食模型的平衡态问题.应用特征值理论和分歧理论讨论共存态的存在性.结果表明,交错扩散有助于物种的共存.

城市边缘地带人居环境的协调性发展研究——工业区发展演变对人居环境的影响探讨

以烟台市的工业区的发展为研究目标,围绕其在城市化进程中对人们居住质量的影响展开研究。工业区在城市化进程中处于向工业、居住、商务混合区过渡的过程,研究在这个区域和这个过程中人们的居位环境质量的改变和发展,为位于城市边缘地带中工业区的发展探讨更适合于其生态和协调发展的方法,改善在城市化进程中人们的居住环境,使工业区与居民区共存。

Insight into the role of ethylene glycol on thermodynamics and nucleation kinetics of dimethyl terephthalate in mixed solvent system

Dissolution and nucleation are two essential processes for industrial crystallization.This paper in-vestigates the effect of ethylene glycol addition on the crystallization behavior of dimethyl terephthalate(DMT)in solution.The DMT solubility in mixed solvent system(methanol-ethylene glycol)was deter-mined by isothermal satiation approach,and the solubility was associated using seven models.The model fitting results were consistent with the experimental values.Based on the results,the metastable zone width(MSZW)of DMT was detected by the polythermal approach;the modified Sangwal's theory was used to investigate the nucleation behavior,which can provide a new way of thought for better analysis of the crystallization behavior.The results demonstrated that MSZW was associated with various elements,such as cooling rate,saturation temperature and mass fraction of ethylene glycol.The addition of ethylene glycol slowed down the nucleation rate as shown by the broadening of MSZW.We derive the solid-liquid interface energy,the nucleation driving force,the critical nucleation size and the critical Gibbs free energy according to the classical nucleation theory.It is demonstrated that the nucleation driving force and the solid-liquid interface energy are dependent and jointly influence the MSZW.

Melting temperature of iron under the Earth’s inner core condition from deep machine learning

Constraining the melting temperature of iron under Earth’s inner core conditions is crucial for understanding core dynamics and planetary evolution.Here,we develop a deep potential(DP)model for iron that explicitly incorporates electronic entropy contributions governing thermodynamics under Earth’s core conditions.Extensive benchmarking demonstrates the DP’s high fidelity across relevant iron phases and extreme pressure and temperature conditions.Through thermodynamic integration and direct solid–liquid coexistence simulations,the DP predicts melting temperatures for iron at the inner core boundary,consistent with previous ab initio results.This resolves the previous discrepancy of iron’s melting temperature at ICB between the DP model and ab initio calculation and suggests the crucial contribution of electronic entropy.Our work provides insights into machine learning melting behavior of iron under core conditions and provides the basis for future development of binary or ternary DP models for iron and other elements in the core.

添加重熔料及稀土钇对ZL205A合金铸态组织、热裂性能及凝固特性的影响

研究重熔料及稀土钇对ZL205A合金铸态组织、热裂性能及凝固特性的影响。结果表明:单独和复合添加重熔料及稀土钇都能够细化合金组织,使之变得更加均匀、细小。单独添加重熔料对ZL205A合金相的组成没有影响,但是提高了ZL205A合金凝固过程中液相线温度,增大了固液共存区间,进而增加合金的热裂倾向性;单独添加稀土钇和复合添加重熔料及稀土钇均可使合金凝固过程中液相线温度降低,减小固液共存区间从而有效地改善合金的热裂倾向性,使得热裂抗力由原料ZL205A合金的330N左右分别提高至450和670N左右。除此之外,添加稀土钇后,三角晶界处出现了灰色块状富钇相。

双侧不同约束碰振系统的周期运动转迁规律

针对一类含不同约束的单自由度碰撞振动系统,建立了系统的Poincaré映射,进而推导出映射的雅可比矩阵.在多参数协同仿真方法的基础上,结合胞映射法研究了系统在间隙(b1,b2)参数平面内各类周期运动分布及共存的特点,总结了相邻周期运动之间的转迁规律.系统相邻周期运动之间主要通过擦边分岔和鞍结分岔实现转迁,转迁过程不可逆,在相邻周期运动间分布着多态共存区;在转迁过程中当系统出现倍周期分岔或边界激变时,相邻周期运动之间会经过由复杂周期运动组成的过渡区进行转迁.

Al—Cu 合金固液共存区的流变行为

本文研究了 Al-Cu 合金固液共存区的流变行为,提出了开尔芬体温度和开尔芬体有效温度区间的概念,并就开尔芬体在固液共存区的力学行为进行了微观解释。

Mn 对 Al-5wt-%Cu 合金固液共存区流变行为的影响

在自行研制的 Al 合金流变性能测试装置上研究了 Mn 对 Al-5wt-%Cu 合金固液共存区流变行为的影响。实验结果表明,Mn 能不同程度地提高合金在固液共存区的剪切模量、粘度系数和屈服强度,并能使开尔芬体的延迟时间η_2/G_2最小值所对应的温度和开尔芬体温度右移,使开尔芬体有效温度区间扩大。