基于非线性涡流的结构材料塑性损伤评价

基于非线性涡流(nonlinear eddy current,简称NEC)检测技术搭建了实验系统,对Q195碳素钢和304奥氏体不锈钢两种常用核电结构材料的塑性损伤程度进行无损定量评价研究。发现材料的塑性损伤程度与非线性涡流检测信号频谱图中基频幅值、三次谐波幅值存在一定线性关系。不同材料的线性关系存在差异,Q195碳素钢的检测信号随损伤程度增大而下降,304奥氏体不锈钢的检测信号随损伤程度增大而上升。通过开发实验系统、进行塑性变形导入和非线性涡流检测实验,分析检测信号与塑性变形程度的相关性,发现检测信号中基波幅值及三次谐波幅值与检测试件的塑性变形程度具有良好相关性,验证了本研究方法对两种典型核电结构材料塑性变形无损定量评价的有效性与可行性。     

改建工程竖向构件力系转换施工

结合上海华润时代广场改造项目,对改造工程中竖向构件力系转换的施工技术进行了介绍。通过在转换过程中对各受力构件的受力状态变化进行实时监测,确保了施工全过程的安全完成,所总结的经验为类似工程提供了参考。     

镍基多孔材料压缩性能的研究

镍基合金的弹性模量、弹性范围大小及在弹性范围内弹性模量的变化情况等是评价其在某些工程应用中使用价值的重要参数。使用镍基合金和造孔剂的混合粉末制备多孔性镍基合金试件,利用激光共聚焦显微镜、拉伸-压缩试验机、数据采集仪器等对试样的微观形貌、弹性模量、压缩-回弹性能等进行表征,与镍基合金实体金属相比较,结果表明:多孔性镍基合金具有更低的弹性模量,在达到相同的应变的情况下,其所受到的应力更小,并且,多孔性镍基合金材料所能达到的最大可恢复应变更大,即其弹性范围更大。     

结构用平压毛竹集成材单轴本构关系研究

为研究平压毛竹集成材单轴拉压状态下的应力-应变本构关系,以5年生毛竹的根部、中部和稍部为原料按照1∶1∶1的比例制备的毛竹集成材试件为研究对象。探讨了毛竹集成材受拉和受压状态下的破坏模式及应力-应变全过程曲线。研究结果表明:毛竹集成材的受拉破坏表现出典型的脆性拉断破坏;毛竹集成材的受压破坏属于延性破坏,具体表现3种典型破坏模式:纤维纵向撕裂、竹片层间开裂和褶皱破坏,经历了3个破坏阶段,即线弹性阶段、弹塑性阶段和加速破坏段。对于毛竹集成材单轴受拉应力-应变关系,提出了线弹性模型;对于毛竹集成材单轴受压应力-应变关系,提出了三折线模型和多项式模型,理论模型结果和试验结果吻合较好,为毛竹集成材结构有限元分析提供研究基础。     

基于工程认证标准要求的课程权重系数计算方法分析

建筑环境与能源应用工程是以培养学生能够从事工业与民用建筑环境控制和能源供应为主的工程应用性专业,根据工程认证标准要求,建环专业的毕业要求控制指标点各因素应根据培养目标和课程体系进行权重系数计算。目前,由于工程认证在我国开展时间不长,专业教师还缺少对相关权重系数计算方法的认识、理解和掌握。这不利于教学开展,也不符合工程认证条件下专业的发展要求。在工程认证标准基础上,对建环专业的毕业要求指标点与支撑课程之间的关系进行了分析,利用层次分析法通过构建指标点和支撑课程的层次结构模型,建立其判断矩阵,并对各指标点因素的权重系数进行了计算分析,获得了毕业要求不同指标点的权重系数,并对其计算结果进行了分析讨论;同时,将层次分析法与学分法得到的权重系数进行了比较分析,指出了每种计算方法存在的优缺点,以期对建环专业的工程认证起到促进作用。     

高温碳化张力对碳纤维性能影响

在碳纤维生产过程中张力贯穿于整个工艺过程,张力控制的划分可分为两个部分,一是预氧化张力控制;二是碳化张力控制。借助在线张力仪详细研究了特定工艺条件下的高温碳化张力对6K碳纤维拉伸强度、弹性模量和密度的影响。     

Evaluation of soil nitrogen emissions from riparian zones coupling simple process-oriented models with remote sensing data

Riparian ecosystems have critical impacts on controlling the non-point source pollution and maintaining the health of aquatic ecosystems. In this study, a process oriented soil denitrification model was extended with algorithms from a simple nitrogen (N) cycle model and coupled to land surface remote sensing data to enhance its performance in spatial and temporal prediction of gaseous N emissions from soils in the riparian buffer zone surrounding the Guanting reservoir (China). The N emission model is based on chemical and physical relationships that govern the heat budget, soil moisture variations and nitrogen movement in soils. Besides soil water and heat processes, it includes nitrification, denitrification and ammonia (NH₃) volatilization. SPOT-5 and Landsat-5 TM satellite data were used to derive spatial land surface information and the temporal variation in land cover parameters was also used to drive the model. A laboratory-scale anaerobic incubation experiment was used to estimate the soil denitrification model parameters for the different soil types. An in situ field-scale experiment was conducted to calibrate and validate the soil temperature, moisture and nitrogen sub-models. An indirect method was used to verify simulated N emissions, resulting in a coefficient of determination of R² = 0.83 between simulated and observed values. Then the model was applied to the whole riparian buffer zone catchment, using the spatial resolution (10 m) of the SPOT-5 image. Model sensitivity analysis showed that soil moisture was the most sensitive parameter for gaseous N emissions and soil denitrification was the main process affecting N losses to the atmosphere in the riparian area. From the aspect of land use management around the Guanting reservoir, the spatial structure and distribution of land cover and land use types in the riparian area should be adapted, to enhance faster ecological restoration of the wetland ecological system surrounding this strategically important water resource.     

大功率LED照明灯有限元热设计与高效系统开发

随着LED亮度要求的不断提高,LED的温度分布和采用的散热手段对LED的可靠性有很大影响。利用ANSYS软件对LED照明的散热问题进行了详细的模拟计算。基于100 WLED实验和模拟结果的一致性,分析比较了不同结构和加载方式对200 WLED温度分布的影响。采用增加散热片个数及其长度、Al锭厚度、灯头的直径等因素,对LED的散热进行了优化设计,结合基于VC++的二次开发系统,较好实现了LED热模拟分析。研究发现LED照明灯的传热方向主要是轴向,轴向散热设计可提高LED开发效率;点阵排列LED灯的温度分布呈现一定的温度梯度;在基于实验验证的模拟可以较好实现不同功率的LED灯散热设计。模拟分析为LED的散热方案优化设计提供了有效的参考依据和手段。     

人工砂干混普通防水砂浆抗渗性能的试验研究

利用人工砂生产干混普通防水砂浆,研究了人工砂中石粉含量、增稠保水材料和膨胀剂对干混普通防水砂浆抗渗性能的影响,并通过SEM和孔结构技术分析了其作用机理.应综合干混普通防水砂浆各项性能要求,确定比较合适的干混普通防水砂浆配合比.     

Highly Enantioselective Epoxidation of Unfunctionalized Olefins Catalyzed by Chiral Jacobsen’s Catalyst Immobilized on Phenoxy‐Modified Zirconium Poly(syrene‐phenylvinylphos‐ phonate)phosphate

Chiral Jacobsen’s catalyst was axially immobilized onto phenoxy‐modified zirconium poly(styrene‐phenylvinylphosphonate)phosphate (ZPS‐PVPA). The immobilized catalysts show comparable ee values for asymmetric epoxidation of styrene and much higher ee values for α‐methylstyrene (73.7% vs. 54.0%) and indene (99.9% vs. 65.0%) than the homogeneous Jacobsen’s catalyst. Moreover, the as‐synthesized catalysts are relatively stable and can be recycled at least five times without significant loss of activity and enantioselectivity. A point worth emphasizing is that the heterogeneous catalysts afforded remarkable increases of conversion and ee values in the absence of expensive O‐coordinating axial bases for the asymmetric epoxidation of olefins, especially for the epoxidation of α‐methylstyrene (conversion: from 24.3% to 99.9%; ee: from 29.4% to 73.7%), which may overcome the last obstacle for the potential industry application of chiral Jacobsen’s catalyst.