配分工艺对中碳Ti-Mo高强Q&P钢组织和性能的影响

摘要：采用盐浴实验、扫描电镜、透射电镜、拉伸实验和磨损实验等手段，研究了配分工艺对中碳Ti Mo钢组织和性能的影响，分析了不同配分工艺处理下的组织演变和性能变化。结果表明，显微组织主要由回火马氏体、渗碳体、(Ti，Mo)C粒子组成。随着配分时间的延长和配分温度的升高，板条马氏体数量减少，马氏体板条厚度增加，边界钝化。此外，随着配分温度从310℃提高至400℃，抗拉强度、硬度和低温冲击韧性同时下降，分别降低约250MPa、56HV和15J。最后，Ms以下温度配分（310℃）试样的耐磨损性能明显优于Ms以上温度配分（400℃）试样。Ms以下温度配分试样磨损表面形貌以塑性变形为主，Ms以上温度配分试样磨损表面以犁沟为主。     

智能数据分区与布局研究

大数据时代,数据规模庞大,由数据进行驱动的应用分析场景日益增多.如何快速、高效地从这些海量数据中提取出用以分析决策的信息,给数据库系统带来重大挑战.同时,现代商业分析决策对分析数据的实时性要求数据库系统能够同时快速处理ACID事务和复杂的分析查询.然而,传统的数据分区粒度太粗,且不能适应动态变化的复杂分析负载;传统的数据布局单一,不能应对现代大量增加的混合事务分析应用场景.为了解决以上问题,“智能数据分区与布局”成为当前的研究热点之一,它通过数据挖掘、机器学习等技术抽取工作负载的有效特征,设计最佳的分区策略来避免扫描大量不相关的数据,指导布局结构设计以适应不同类型的工作负载.首先介绍了智能数据分区与布局的相关背景知识,然后对智能数据分区与布局技术的研究动机、发展趋势、关键技术进行详细的阐述.最后,对智能数据分区与布局技术的研究前景做出总结与展望.     

两相区配分时间对IQ&P钢组织与性能的影响

以含Cu低碳钢为研究对象,利用SEM、EPMA和拉伸试验研究了两相区配分时间对其组织演变、元素配分以及经IQ&P处理后力学性能的影响,并利用Dictra软件对元素配分行为进行了动力学计算。结果表明,IQ处理后试验钢中的块状马氏体形成于原铁素体区域;随两相区配分时间延长,粒状马氏体数量减少,板条状马氏体之间的间距减小。检测和计算结果的对比显示,C、Mn、Cu 3种元素的相对配分速率与计算结果一致,但实际配分速率低于各自的计算结果。随两相区配分时间延长,经IQ&P处理后试验钢的抗拉强度先增加后减小,而伸长率持续减小;在600 s时达到较好的强塑性匹配,强塑积为16 963.24 MPa·%。     

Sources and dynamics of semivolatile organic compounds in a single‐family residence in northern California

Semivolatile organic compounds (SVOCs) emitted from building materials, consumer products, and occupant activities alter the composition of air in residences where people spend most of their time. Exposures to specific SVOCs potentially pose risks to human health. However, little is known about the chemical complexity, total burden, and dynamic behavior of SVOCs in residential environments. Furthermore, little is known about the influence of human occupancy on the emissions and fates of SVOCs in residential air. Here, we present the first‐ever hourly measurements of airborne SVOCs in a residence during normal occupancy. We employ state‐of‐the‐art semivolatile thermal‐desorption aerosol gas chromatography (SV‐TAG). Indoor air is shown consistently to contain much higher levels of SVOCs than outdoors, in terms of both abundance and chemical complexity. Time‐series data are characterized by temperature‐dependent elevated background levels for a broad suite of chemicals, underlining the importance of continuous emissions from static indoor sources. Substantial increases in SVOC concentrations were associated with episodic occupant activities, especially cooking and cleaning. The number of occupants within the residence showed little influence on the total airborne SVOC concentration. Enhanced ventilation was effective in reducing SVOCs in indoor air, but only temporarily; SVOCs recovered to previous levels within hours.     

The three Rs of river ecosystem resilience: Resources,recruitment, and refugia

Resilience in river ecosystems requires that organisms must persist in the face of highly dynamic hydrological and geomorphological variations. Disturbance events such as floods and droughts are postulated to shape life history traits that support resilience, but river management and conservation would benefit from greater understanding of the emergent effects in communities of river organisms. We unify current knowledge of taxonomic‐, phylogenetic‐, and trait‐based aspects of river communities that might aid the identification and quantification of resilience mechanisms. Temporal variations in river productivity, physical connectivity, and environmental heterogeneity resulting from floods and droughts are highlighted as key characteristics that promote resilience in these dynamic ecosystems. Three community‐wide mechanisms that underlie resilience are (a) partitioning (competition/facilitation) of dynamically varying resources, (b) dispersal, recolonization, and recruitment promoted by connectivity, and (c) functional redundancy in communities promoted by resource heterogeneity and refugia. Along with taxonomic and phylogenetic identity, biological traits related to feeding specialization, dispersal ability, and habitat specialization mediate organism responses to disturbance. Measures of these factors might also enable assessment of the relative contributions of different mechanisms to community resilience. Interactions between abiotic drivers and biotic aspects of resource use, dispersal, and persistence have clear implications for river conservation and management. To support these management needs, we propose a set of taxonomic, phylogenetic, and life‐history trait metrics that might be used to measure resilience mechanisms. By identifying such indicators, our proposed framework can enable targeted management strategies to adapt river ecosystems to global change.     

Simplified partitioning model to simulate high pressure under-expanded jet flows impinging vertical obstacles

Various reduced-order models have been developed to quickly model high pressure underexpanded jets. One example is the two-layer partitioning model which was developed to model underexpanded jets, but it has not been evaluated for high pressure jets with obstacles in the jet flow region. This research describes an improved two-layer partitioning model based on the Abel-Noble equation of state that is applied here to model horizontal jet flows impacting a vertical obstacle with validations against high pressure gas experiments, full CFD simulations and a revised notional nozzle model based on the Abel-Noble equation of state. The improved two-layer partitioning model accurately predicts the gas concentrations on the obstacle for a 15 MPa underexpanded jet while consuming much less computational resources and time compared with the full CFD simulation.     

Measurements and modeling of absorptive partitioning of volatile organic compounds to painted surfaces

Partitioning to surfaces is an important sink for volatile organic compounds (VOCs) indoors, but the mechanisms are not well understood or quantified. Here, a mass spectrometer was coupled to a portable surface reactor and a flow tube to measure partitioning of VOCs into paint films coated onto glass or wallboard, and their subsequent diffusion. A model was developed to extract values of the effective absorbing organic mass concentration of the film, C_w, which is a measure of absorption capacity, and VOC diffusion coefficients, D_f, from VOC time profiles measured during film passivation and depassivation. Values of C_w agreed well with the value estimated from the paint film mass and flow tube air volume, and D_f values (also measured using attenuated total reflectance-Fourier transform infrared spectroscopy) correlated well with VOC vapor saturation concentrations, C*, estimated using a group contribution method. The value of these relationships for estimating key parameters that control VOC partitioning into paint and the fate of VOCs indoors was demonstrated using a house model, which indicated that >50% of VOCs with C* ≤10⁸ μg/m³ (C* of octane, hexanone, and propanol) that contacted a paint film of typical thickness fully permeated the film regardless of emission duration.     

淬火配分处理对锻态Fe-0.2C-9Mn-3.5Al钢显微组织及力学行为的影响

分析了淬火配分处理对锻态Fe-0.2C-9Mn-3.5Al钢显微组织及力学行为的影响。结果表明,热处理态试验钢主要由块状δ-铁素体、马氏体和板条状残留奥氏体等多相构成;残留奥氏体的体积分数随等温淬火温度升高而增大,在310 ℃时达到峰值;310 ℃等温淬火后在400 ℃配分3 min时可以获得较优的综合力学性能,抗拉强度和断后伸长率分别为1175 MPa和21.50%,强塑积达到25.26 GPa·%;应力-应变曲线中存在着明显的“锯齿”状起伏,可能与亚稳态的残留奥氏体集中转变为马氏体有关。     

中锰Q&P钢连续退火过程碳元素分配行为

采用扫描电镜、X射线衍射等研究了连续退火工艺中退火、淬火和配分等关键过程参数对中锰Q&P钢碳元素分配行为的影响,并分析了相应工艺条件下残留奥氏体量与碳含量的关系。结果表明:两相区退火温度的提高会导致奥氏体中的碳含量下降,微观组织表现为奥氏体含量增加,渗碳体量减少;退火时间10~60 s时,随着退火时间的延长,奥氏体含量和碳含量急剧增加,60 s后基本保持稳定;试验条件下淬火温度对残留奥氏体及碳含量的影响不显著;配分温度350~500℃时,随着配分温度的提高,奥氏体含量和碳含量呈现先增加后减小的趋势,配分温度450℃时均达到最大值;延长配分时间,残留奥氏体含量呈现先减少后增大再减少的趋势,残留奥氏体中的碳含量先减小后增加。