Head Start and urban children's school readiness: A birth cohort study in 18 cities.

We used longitudinal data from a birth cohort study, the Fragile Families and Child Wellbeing Study, to investigate the links between Head Start and school readiness in a large and diverse sample of urban children at age 5 (N = 2,803; 18 cities). We found that Head Start attendance was associated with enhanced cognitive ability and social competence and reduced attention problems but not reduced internalizing or externalizing behavior problems. These findings were robust to model specifications (including models with city-fixed effects and propensity-scoring matching). Furthermore, the effects of Head Start varied by the reference group. Head Start was associated with improved cognitive development when compared with parental care or other nonparental care, as well as improved social competence (compared with parental care) and reduced attention problems (compared with other nonparental care). In contrast, compared with attendance at pre-kindergarten or other center-based care, Head Start attendance was not associated with cognitive gains but with improved social competence and reduced attention and externalizing behavior problems (compared with attendance at other center-based care). These associations were not moderated by child gender or race/ethnicity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Random laser based on waveguided plasmonic gain channels

A waveguide-plasmonic scheme is constructed by coating the matrix of randomly distributed gold nanoisland structures with a layer of dye-doped polymer, which provides strong feedback or gain channels for the emission from the dye molecules and enables successful running of a random laser. Excellent overlap of the plasmonic resonance of the gold nanoislands with the photoluminescence spectrum of the dye molecules and the strong confinement mechanism provided by the active waveguide layer are the key essentials for the narrow-band and low-threshold operation of this random laser. This kind of feedback configuration potentially enables directional output from such random lasers. The flexible solution-processable fabrication of the plasmonic gold nanostructures not only enables easy realization of such a random laser but also provides mechanisms for the tuning and multicolor operation of the laser emission.     

Study on NIR optical rewritable film based on dithienylethene and upconversion nanocrystals

Tm3+ and Yb3+ codoped NaYF4 upconversion (UC) nanoparticles (NPs) with intense ultraviolet (UV) fluorescence were synthesized using a solvothermal approach. NIR optical rewritable film incorporated with the UCNPs and dithienylethene (DTE) were performed for optical storage based on the photochromic reaction of DTE induced by the intense UV from themultiphoton UC fluorescence of NaYF4NPs. The photochromic DTE did not exhibit obvious fatigue after repetitious write/erase cycles using NIR/green irradiation.     

量子级联红外探测器

半导体基中远红外探测器在成像、传感、国家安全以及国防领域具有广泛的应用背景.目前,在这个领域最主流的技术之一是量子阱红外探测器( QWIPs).传统的量子阱红外探测器往往存在较大的暗电流和较低的工作温度等限制.量子级联探测器( QCDs)是一种新型的光伏型量子阱红外探测器.其工作原理基于电子吸收光子后在量子阱的子带间跃...     

基于STM32的传感器接口模块的设计

基于STM32实现了电流型、电压型以及数字IO型传感器接口模块;进行了接口模块的软件设计,说明了详细的固件代码设计.除传统串口外,提供以太网接口,嵌入UDP协议,提供后期开发的便利接口.     

6061-T6铝合金高速高功率CO_2激光填丝焊接性的研究

为实现6061-T6铝合金薄板的高速高功率CO2激光填丝焊接,选用了ER4043,ER5356两种焊丝进行了焊接性试验。利用鱼骨状试样对两种焊丝的激光焊接铝合金6061-T6的热裂纹敏感性进行了分析;利用金相显微镜、扫描电镜、显微硬度计以及万能材料试验机分析了焊接接头的组织与性能。研究结果表明,与填充ER5356焊丝相比,填充ER4043焊丝的焊接接头热裂纹敏感性较低,焊接速度可达6 m/min。焊缝主要是柱状晶、等轴晶及少量树枝晶,显微硬度在60~80 HV,拉伸强度可达240~262 MPa,弯曲性能良好。     

西北处置场低、中放固体废物处置实践

介绍了我国西北处置场的基本情况,西北处置场低、中放固体废物接收、处置的组织机构及管理体系,工艺技术,辐射防护及环境监测,以期为我国放射性废物处置工程提供借鉴和支持。     

提高球墨铸铁管综合合格率的措施

对球墨铸铁管综合合格率低的原因进行了分析并采取了改进措施。现场分析结果表明：＂重皮、气孔与针孔＂和＂夹渣夹杂＂是导致球墨铸铁管综合合格率低的主要原因。通过规范管模使用、调整流槽高度、合理控制铁水温度和规范控制主机走速、翻包量、管模转速等措施,减少了铸铁管＂重皮、气孔与针孔＂和＂夹渣夹杂＂的质量缺陷,提高了铸铁管综合合格率,实现了企业的降本增效。     

易切削钢中硫化物形态的研究

以易切削钢20CrMnTiSH为研究对象,通过喂硫线增加钢中硫化物数量,再喂入SiCa线使长条形的硫化物变性为球形或纺锤形,在改善钢材切削性能的同时不降低钢材的机械性能。对LF、VD和轧材取样进行检验。检验结果表明:钙处理后夹杂物数量增多,94%以上的夹杂物粒径集中在0～4μm之间;夹杂物纺锤率平均值达到50.73%,在钢中呈细小弥散的分布;氧、Mn/S、Ca/S是影响硫化物形态的重要因素。     

10000m~3/h空分设备冷箱内管道焊缝开裂分析

由于安装人员将粗氩塔进液阀V3的固定支架和活动支架的位置装反,导致投运制氩系统时V3阀进口管线焊缝开裂,制氩系统不能成功投入运行。文章介绍了故障经过、原因分析过程和冷箱内损坏情况,最后阐述了冷箱内管道的优化措施和避免同类故障再次发生的防范措施。