为儿童而设计——以首都儿科研究所附属儿童医院通州院区方案设计为例

针对首都儿科研究所附属儿童医院通州院区的建设,设计者从方案设计开始就对标国际知名儿童医院,在吸取优质经验的同时又寻求创新,力争实现"打造以儿童健康为中心的当代儿童医院建设典范"的建设目标.方案在城市空间、儿童特色塑造、卓越医疗中心、平疫结合、康愈花园、技术应用等方面做了大量探索,为未来我国儿童医院的建设提供有益指导.     

城镇燃气典型输配系统甲烷排放源识别及分类

借鉴国内外相关甲烷排放核算研究成果和实践经验,结合中国城镇燃气典型输配系统的工艺特点,进行甲烷排放源识别及分类研究。研究表明,城镇燃气典型输配系统从门站进站管道到用户燃气表之间的所有设施、设备、组件及连接处都存在甲烷排放的可能,按照排放类型分为逃逸排放和放散排放;按照设施类型分为埋地燃气管道排放、燃气厂站排放和终端用户排放。根据国内外文献调研,不同设施类型中的材料材质、设备类型是影响甲烷排放量的重要因素,因此将排放源细分为6个一级排放源,21个二级排放源,72个三级排放源,为城镇燃气典型输配系统排放清单编制奠定基础。     

城镇燃气典型输配系统甲烷排放源识别及分类

借鉴国内外相关甲烷排放核算研究成果和实践经验,结合中国城镇燃气典型输配系统的工艺特点,进行甲烷排放源识别及分类研究。研究表明,城镇燃气典型输配系统从门站进站管道到用户燃气表之间的所有设施、设备、组件及连接处都存在甲烷排放的可能,按照排放类型分为逃逸排放和放散排放;按照设施类型分为埋地燃气管道排放、燃气厂站排放和终端用户排放。根据国内外文献调研,不同设施类型中的材料材质、设备类型是影响甲烷排放量的重要因素,因此将排放源细分为6个一级排放源,21个二级排放源,72个三级排放源,为城镇燃气典型输配系统排放清单编制奠定基础。     

金属薄膜屈服强度的鼓包法表征

本文采用鼓包法研究金属薄膜的屈服强度,对具有圆形自由窗口的镍薄膜一侧施加压力,薄膜受压变形的全场形貌用数字散斑相关法(DSCM)进行测量,并应用板壳理论分析小挠度变形下膜内应力分布情况。结果表明:圆形薄膜受压时首先从边缘开始屈服,从压力-挠度曲线偏离线性关系的临界点得到金属镍膜的屈服强度为467MPa,这和单轴拉伸法测量所得到的屈服强度值吻合较好。     

Simulation Guided Coaxial Electrospinning of Polyvinylidene Fluoride Hollow Fibers with Tailored Piezoelectric Performance

Electrospun polyvinylidene fluoride (PVDF) piezoelectric fibers have high potential applicability in mechanical energy harvesting and self-powered sensing owing to their high electromechanical coupling capabilities. Strategies for tailoring fiber morphology have been the primary focus for realizing enhanced piezoelectric output. However, the relationship between piezoelectric performance and fiber structure remains unclear. This study fabricates PVDF hollow fibers through coaxial electrospinning, whose wall thickness can be tuned by changing the internal solution concentration. Simulation analysis demonstrates an increased effective deformation of the hollow fiber as enlarging inner diameter, resulting in enhanced piezoelectric output, which is in excellent agreement with the experimental results. This study is the first to unravel the influence mechanism of morphology regulation of a PVDF hollow fiber on its piezoelectric performance from both simulation and experimental aspects. The optimal PVDF hollow fiber piezoelectric energy harvester (PEH) delivers a piezoelectric output voltage of 32.6 V, ≈3 times that of the solid PVDF fiber PEH. Furthermore, the electrical output of hollow fiber PEH can be stably stored in secondary energy storage systems to power microelectronics. This study highlights an efficient approach for reconciling the simulation and tailoring the fiber PEH morphology for enhanced performances for future self-powered systems.     

Ultrafast and Stable Li-(De)intercalation in a Large Single Crystal H-Nb2O5 Anode via Optimizing the Homogeneity of Electron and Ion Transport

Exploring anode materials with fast, safe, and stable Li-(de)intercalation is of great significance for developing next-generation lithium-ion batteries. Monoclinic H-type niobium pentoxide possesses outstanding intrinsic fast Li-(de)intercalation kinetics, high specific capacity, and safety; however, its practical rate capability and cycling stability are still limited, ascribed to the asynchronism of phase change throughout the crystals. Herein this problem is addressed by homogenizing the electron and Li-ion conductivity surrounding the crystals. An amorphous N-doped carbon layer is introduced on the micrometer single-crystal H-Nb₂O₅ particle to optimize the homogeneity of electron and Li-ion transport. As a result, the as-prepared H-Nb₂O₅ exhibits high reversible capacity (>250 mAh g⁻¹ at 50 mA g⁻¹), unprecedented high-rate performance (≈120 mAh g⁻¹ at 16.0 A g⁻¹) and excellent cycling stability (≈170 mAh g⁻¹ at 2.0 A g⁻¹ after 1000 cycles), which is by far the highest performance among the H-Nb₂O₅ materials. The inherent principle is further confirmed via operando transmission electron microscopy and X-ray diffraction. A novel insight into the further development of electrode materials forlithium-ion batteries is thus provided.     

Designing Champion Nanostructures of Tungsten Dichalcogenides for Electrocatalytic Hydrogen Evolution

Fine-tuning strain and vacancies in 2H-phase transition-metal dichalcogenides, although extremely challenging, is crucial for activating the inert basal plane for boosting the hydrogen evolution reaction (HER). Here, atomically curved 2H-WS₂ nanosheets with precisely tunable strain and sulfur vacancies (S-vacancies) along with rich edge sites are synthesized via a one-step approach by harnessing geometric constraints. The approach is based on the confined epitaxy growth of WS₂ in ordered mesoporous graphene derived from nanocrystal superlattices. The spherical curvature imposed by the graphitic mesopores enables the generation of uniform strain and S-vacancies in the as-grown WS₂ nanosheets, and simultaneous manipulation of these two key parameters can be realized by simply adjusting the pore size. In addition, the formation of unique mesoporous WS₂@graphene van der Waals heterostructures ensures the ready access of active sites. Fine-tuning the WS₂ layer number, strain, and S-vacancies enables arguably the best-performing HER 2H-WS₂ electrocatalysts ever reported. Density functional theory calculations indicate that compared with strain, S-vacancies play a more critical role in enhancing the HER activity.     

Niobium-Carbide MXene Modified Hybrid Hole Transport Layer Enabling High-Performance Organic Solar Cells Over 19%

Niobium-carbide (Nb₂C) MXene as a new 2D material has shown great potential for application in photovoltaics due to its excellent electrical conductivity, large surface area, and superior transmittance. In this work, a novel solution-processable poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS)-Nb₂C hybrid hole transport layer (HTL) is developed to enhance the device performance of organic solar cells (OSCs). By optimizing the doping ratio of Nb₂C MXene in PEDOT:PSS, the best power convention efficiency (PCE) of 19.33% can be achieved for OSCs based on the ternary active layer of PM6:BTP-eC9:L8-BO, which is so far the highest value among those of single junction OSCs using 2D materials. It is found that the addition of Nb₂C MXene can facilitate the phase separation of the PEDOT and PSS segments, thus improving the conductivity and work function of PEDOT:PSS. The significantly enhanced device performance can be attributed to the higher hole mobility and charge extraction capability, as well as lower interface recombination probabilities generated by the hybrid HTL. Additionally, the versatility of the hybrid HTL to improve the performance of OSCs based on different nonfullerene acceptors is demonstrated. These results indicate the promising potential of Nb₂C MXene in the development of high-performance OSCs.     

Mn掺杂花状ZnO的合成及其光催化特性研究

采用液相沉积法,在室温条件下制备了不同Mn掺杂浓度(0,0.25%,0.5%和1.0%(摩尔分数))的花状ZnO微结构。利用X射线衍射(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)对制备的花状ZnO微结构的物相及形貌进行表征。以甲基橙溶液作为光催化反应模型污染物,对不同浓度的Mn掺杂花状ZnO微结构的光催化性能进行了研究。实验结果表明,Mn在ZnO材料中以两种形态存在,即进入晶格以Mn2+形式替代Zn2+和以Mn3O4形式附着在ZnO材料表面。且Mn掺杂提高了花状ZnO微球结构的光催化活性,当掺杂浓度为0.25%(摩尔分数)时光催化性能最优,紫外光照2.0h后,对甲基橙的光催化降解率可达88.7%。     

保护层开采爆破技术数值模拟研究与应用

为保证保护层开采的爆破效果,提高施工效率并降低爆破成本,采用垂直炮孔底部填充波阻抗差异较大的垫层材料的技术进行保护层开采爆破。在分析爆炸应力波的特点、作用范围、反射与透射原理后,选取泡沫混凝土加松砂作为复合垫层材料。使用LS DYNA对不同保护层开采爆破高度和不同泡沫混凝土高度的保护层开采爆破进行模拟分析,探索保护层开采爆破的合理高度。分析认为,采用25 cm泡沫混凝土加10 cm松砂复合垫层时,保护层开采爆破高度宜为4 m。研究结果在广东太平岭核电站建设中得到运用,建基面岩体得到良好的保护。