基于影响力扩散的会话推荐模型

会话推荐的任务是根据用户近期的点击行为预测下一个点击.该领域之前的模型主要关注到会话推荐中的时序模式(序列特征),但是由于用户兴趣迁移以及商品多属性等因素,物品之间的交互关系可能比呈现出来的时序模式更为复杂.为了解决该问题,受PageRank算法的启发,把会话点击和网页跳转联系起来,提出了一个会话推荐中的影响力扩散模型.具体地说,该模型在会话序列的显式时序结构之上构建了会话图,刻画出更加丰富的转移路径,并通过图扩散模型捕获到物品之间的潜在交互关系.在会话表示阶段,该模型提出了一种新颖的位置编码方式来应对兴趣迁移的状况,并在此基础上设计了一种意图提取框架,能在多兴趣会话中迭代出核心意图.在真实数据集上的实验结果表明,所提模型相较于以往方法有较好的性能,并有效解决了兴趣迁移的问题.     

电感耦合等离子体串联质谱法测定 高纯氧化镁粉中金属杂质元素

基于电感耦合等离子体串联质谱(ICP-MS/MS)法建立了准确可靠分析高纯氧化镁粉中金属杂质元素的新方法。ICP-MS/MS通过启用新的质量过滤装置,在氧化镁基质的金属杂质元素测定过程中,能有效减少多原子干扰。采用He为碰撞气,O₂以及NH₃/He混合气为反应气,对比了在单四极杆(SQ)模式和串联四极杆(MS/MS)模式下消除干扰的效果。采用He碰撞模式无法消除一些特殊的质谱干扰,特别是双电荷离子干扰;然而,将分析物转移为氧化物离子或团簇离子,能实现待测元素的无干扰分析,并能获得极低的检出限,通过加标回收实验评估了方法的准确性。结果显示,方法的检出限为0.46~65.9ng/L。各元素的线性相关系数(R²)均不小于0.9998,真实样品的加标回收率为93%~108%,相对标准偏差为1.6%~4.4%。方法完全能用于高纯氧化镁粉中金属杂质元素的实时监控。     

厚火成岩下采煤地表移动规律研究

在厚火成岩下采煤,因火成岩硬度大,不易冒落而容易诱发冲击性地质灾害。为了研究火成岩下开采沉陷规律,解决火成岩下开采地面破坏及建筑物保护问题,建立了地表移动观测站。根据火成岩厚度分布情况,结合数值模拟计算,确定了煤层开采后火成岩随下伏岩层呈整体下沉。利用岩移预计软件计算无火成岩条件下地表变形,与实际观测结果对比,分析火成岩下采煤地表移动规律。     

Schedule Compression Impact on Construction Project Safety

Many construction projects are met with stringent timelines or the threat of exorbitant liquidated damages. In addition, construction schedulers are frequently forced to incorporate aggressive schedule compression techniques. As already discussed by previous researchers, these schedule compression techniques have direct impacts on project productivity and quality defects.Researchers have also pointed out that schedule compression will affect safety incidents such as Occupational Safety Health Administration recordable injuries and near misses over long project durations. However, most of the existing studies treated safety as a subcategory of project productivity and project quality, and minimal research has been done to directly quantify the effect of schedule compression on safety at the project level.Therefore, in this research, we conducted a survey and statistical analysis to investigate the relationship between schedule compression and safety in construction projects.We interviewed various members of the Houston construction community from both industrial and non-industrial roles. Statistical analysis was used to identify factors that have significant impacts on the occurrence of safety incidents at an industry specific level.     

基于优化多核支持向量回归的制造过程均值偏移幅度估计

为更加准确地估计制造过程均值偏移幅度,提出了一种基于多核函数支持向量回归（SVR）的估计方法。多核函数由线性核、多项式核和径向基核3种基本核函数凸组合而成,并通过粒子群优化算法（PSO）对核参数、组合权重系数以及SVR的惩罚系数C进行联合优化,以五折交叉验证求得训练样本的决定系数均值作为粒子适应度值,使生成的多核SVR获得良好的泛化能力。将该多核SVR与累积和（CUSUM）控制图集成构建了过程均值偏移监测模型,仿真实验结果表明,该方法相对人工神经网络（ANN）方法估计精度明显提高,比采用单一径向基核函数的SVR更为优越;在实际齿轮加工过程中进行应用验证,进一步证实了该方法的有效性和实用性。     

有机朗肯循环的研究进展

有机朗肯循环是一种被认为能有效利用低温热能的技术。科研工作者在不同方面（包括工质、膨胀机、换热器的影响、系统的优化）对有机朗肯循环系统效率的影响进行了大量的研究。本文针对不同热源的工质筛选、膨胀机的特点、系统循环优化以及换热器的影响方面进行了讨论和总结,为有机朗肯循环系统的实际应用提供参考。     

减少频谱泄漏的一种新的等角度间隔采样递推算法

提出并证明了离散傅里叶变换的基相量循环移位性质.就减少频谱泄漏问题,根据基相量循环移位性质提出了一种新的等角度间隔采样算法,并证明了该算法的递推特性.仿真结果表明该算法不仅减少了频谱泄漏,提高了谐波分析精度,而且由于算法具有递推特性,使计算量很小,从而保证了分析实时性.有较强的应用价值.     

Effect of Active Lengthening and Shortening on Small-Angle X-ray Reflections in Skinned Skeletal Muscle Fibres

Our purpose was to use small-angle X-ray diffraction to investigate the structural changes within sarcomeres at steady-state isometric contraction following active lengthening and shortening, compared to purely isometric contractions performed at the same final lengths. We examined force, stiffness, and the 1,0 and 1,1 equatorial and M3 and M6 meridional reflections in skinned rabbit psoas bundles, at steady-state isometric contraction following active lengthening to a sarcomere length of 3.0 µm (15.4% initial bundle length at 7.7% bundle length/s), and active shortening to a sarcomere length of 2.6 µm (15.4% bundle length at 7.7% bundle length/s), and during purely isometric reference contractions at the corresponding sarcomere lengths. Compared to the reference contraction, the isometric contraction after active lengthening was associated with an increase in force (i.e., residual force enhancement) and M3 spacing, no change in stiffness and the intensity ratio I_1,1/I_1,0, and decreased lattice spacing and M3 intensity. Compared to the reference contraction, the isometric contraction after active shortening resulted in decreased force, stiffness, I_1,1/I_1,0, M3 and M6 spacings, and M3 intensity. This suggests that residual force enhancement is achieved without an increase in the proportion of attached cross-bridges, and that force depression is accompanied by a decrease in the proportion of attached cross-bridges. Furthermore, the steady-state isometric contraction following active lengthening and shortening is accompanied by an increase in cross-bridge dispersion and/or a change in the cross-bridge conformation compared to the reference contractions.     

Steam effects over Pd/Ce0.67Zr0.33O2-Al2O3 three-way catalyst

Ceria-zirconia-alumina (CZA) solid solution was prepared by sol-gel method in the present study. 0.5 wt.% Pd supported on CZA was prepared by incipient wetness impregnation. The steam effects for CO and C3H8 oxidation, three-way catalytic activity and stoichiometric window property were studied. The light-off temperature of the CO oxidation reaction shifted to a lower temperature due to the water-gas shift (WGS) reactions. The oxidation of C3H8 was enhanced due to the steam reforming (SR) reactions. The steam promoted the C3H8 oxidation and NO reduction in three-way catalytic reaction. The amplitude of stoichiometric window was amplified by the addition of water to the feed stream.