二乙二醇醚马来酸酯钙/锌热稳定剂的制备及应用研究

以马来酸酐和二乙二醇醚为原料在无催化剂条件下制得二乙二醇醚马来酸酯（MD）,此分子结构中具有酯基、醚键及碳碳双键,将此中间产物分别与乙酸钙、乙酸锌反应,制得二乙二醇醚马来酸酯钙/锌盐（MD?Ca/Zn）。通过傅里叶红外测试分析了热稳定剂产物的结构,分子中含有醚键、酯基、碳碳双键、羧酸盐结构,可作为PVC主效热稳定剂。通过刚果红法、热老化法、热失重法、电导率等检测方法,和市售硬脂酸钙/锌进行对比,验证了热稳定效果及性能,分析了热稳定机理,同时探究了与辅助热稳定剂β?二酮（硬脂酰苯甲酰甲烷）的协同作用。结果表明,当MD?Ca/Zn=2∶1（质量比,下同）时,对PVC的热稳定效果最好;初期白度可以达到40 min,静态热稳定时间为35 min;与热稳定剂总质量10 %的β?二酮复配后PVC的热稳定性能还可进一步提升。     

结肠癌基因表达谱的分类检测问题研究

随着大规模基因表达谱技术的发展,基于基因表达谱的癌症诊断方法正在成为临床医学上一种快速有效的诊断方法,但是由于基因表达数据维数过高、样本量小、噪声大,使得正确提取有关癌症的特征基因成为关键。以结肠癌肿瘤的基因表达谱数据为例,提出了结合Fisher权函数、离散傅里叶变换和主成分分析的混合特征基因提取方法,以多元Logistic回归分析和贝叶斯决策作为分类器进行肿瘤分类检测。实验结果表明,该方法对于结肠癌数据集CV识别准确率高达96.80%。     

表面修饰的酸性丝光沸石催化油酸支链化

利用三苯基膦将合成的酸性丝光沸石进行表面修饰处理,使酸性丝光沸石外表面的部分酸性中心被三苯基膦吸附而失活,经过外表面修饰的酸性丝光沸石用于催化油酸支链化的反应,可明显提高目标产物C18饱和支链脂肪酸的选择性,加氢产物的C18饱和支链脂肪酸产率可提高约5个百分点。经过响应面法优化后,表面修饰的酸性丝光沸石催化油酸支链化反应最优工艺条件为:催化剂用量7.0%(基于油酸质量),加水量4.5%(基于油酸质量),反应温度270℃,反应时间4.5 h。在最优反应条件下,C18饱和支链脂肪酸产率可达到87.25%。反应动力学研究表明,该油酸支链化反应的反应活化能为22.46 k J/mol,指前因子为3.2×103。     

A Spatial‐Context‐Based Approach for Automated Spatial Change Analysis of Piece‐Wise Linear Building Elements

Changes of designs and construction plans often cause propagative design modifications, tedious construction coordination, cascading effects of errors, reworks, and delays in project management. Among various building elements, those having piece‐wise linear geometries (i.e., connected straight line segments), such as connected straight sections of ducts in mechanical, electrical, and plumbing systems, frequently undergo spatial changes in response to the changes of their surroundings. On the other hand, the piece‐wise linear geometries pose challenges to analyzing and controlling changes in construction and facility management. State‐of‐the‐art 3D change detection algorithms often face ambiguities about which points belong to which objects when piece‐wise linear object are spacked in small spaces. This article examines a spatial‐context‐based framework that uses spatial relationships between piece‐wise linear building elements (ducts in this article) to enable fast and reliable association of 3D data with ducts in as‐designed models for supporting reliable change analysis. Three case studies showed that this framework outperformed a conventional change detection method, and could handle large dislocations of piece‐wise linear elements and occlusions.     

某“人工湖”防渗分析及评价

通过对湖区水文地质条件、岩溶发育条件、及渗透性分析,确定了湖区地层的相对透水条件,进而分析了湖区渗漏的方式、及渗漏量.总结得出:湖区东西两侧相对隔水,主要由北向南渗漏;湖区渗漏形式为裂隙一溶隙型渗漏;渗漏较弱,渗漏量为7.21m3/d;可不考虑人工湖渗漏,不作防渗处理.     

超细碳酸钙颗粒的离心分级

用一种工业型的牒式离心机对粒度小于8 μm的超细碳酸钙颗粒进行湿法分级.采用统计方法研究了与该离心机相关的主要工艺参数,如:离心力强度、牒类型、喷嘴尺寸、分流率和给料速率等.结果表明:这种牒式离心机可以有效地分级质量分数达到40%的微米粒级的物料,并可获得较窄颗粒粒度分布的超微细产品.离心分级效果与所用的主要参数呈经验关系.     

基于动力吸振原理的动车组车下设备悬挂参数设计

为降低车体的弹性振动,将车体考虑成弹性欧拉梁,基于动力吸振原理进行多个车下设备的最优悬挂频率设计。建立弹性车体和车下设备的垂向耦合振动数学模型,研究不同设备悬挂频率、联接阻尼、质量和安装位置条件下的车体振动分布规律。建立车辆系统三维刚柔耦合动力学模型,仿真分析在实际线路激扰条件下,车体振动和平稳性随设备悬挂参数变化的分布规律。垂向耦合振动理论分析表明动力吸振原理可用于车下设备悬挂参数设计,验证了用于车体弹性振动减振的可行性和有效性,能够显著降低车体的垂弯模态振动;将大质量设备越靠近车体中部安装时车体的减振效果越好;设备悬挂频率应接近车体的垂弯模态频率,较优的弹性联接阻尼比应满足0.05~0.20。三维刚柔耦合动力学仿真结果验证了理论分析结果,车辆运行速度越高,减振效果越显著。试验台结果表明车下设备采用弹性联接可显著改善高速动车组的乘坐平稳性,与理论和仿真分析结果吻合。     

江垭水电站地下洞群三维变形块体稳定分析

根据江垭地下厂房厂区外围正在开挖施工的洞室主要结构面出露情况，应用三维变形块体与弹塑性摩擦接触理论，初步分析了厂区可能存在不稳定块体的数量、规模、坍滑方式和方向，预测了该类不稳定块体对三大洞室开挖施工的影响，并提出对预防措施的意见，可望对设计、施工有所帮助     

Automatic reconstruction of as-built building information models from laser-scanned point clouds: A review of related techniques

Building information models (BIMs) are maturing as a new paradigm for storing and exchanging knowledge about a facility. BIMs constructed from a CAD model do not generally capture details of a facility as it was actually built. Laser scanners can be used to capture dense 3D measurements of a facility's as-built condition and the resulting point cloud can be manually processed to create an as-built BIM — a time-consuming, subjective, and error-prone process that could benefit significantly from automation. This article surveys techniques developed in civil engineering and computer science that can be utilized to automate the process of creating as-built BIMs. We sub-divide the overall process into three core operations: geometric modeling, object recognition, and object relationship modeling. We survey the state-of-the-art methods for each operation and discuss their potential application to automated as-built BIM creation. We also outline the main methods used by these algorithms for representing knowledge about shape, identity, and relationships. In addition, we formalize the possible variations of the overall as-built BIM creation problem and outline performance evaluation measures for comparing as-built BIM creation algorithms and tracking progress of the field. Finally, we identify and discuss technology gaps that need to be addressed in future research.