城市居住区室外光环境现状调查研究

本文通过对天津、长沙、郑州三座城市30个居住区的夜间室外照明情况的调查,使用实地物理测试、居民走访与主观感受的方式,重点研究我国城市居住区光环境的现状和问题,分析近年居住区室外照明发展现状,同时深入探讨城市居住区光环境的特点.     

三峡水库蓄水后水温变化对四大家鱼自然繁殖的影响

三峡水库蓄水后,坝下水温变化对四大家鱼关键生活史阶段造成一定影响。本文使用水温变化指标定量评价蓄水后水温的改变程度,分析水温改变对四大家鱼自然繁殖的影响。基于宜昌水文站1983-2013年长系列逐日水温资料,建立了25个具有生态意义的水温参数,利用变动范围法计算了三峡水库蓄水后25个水温参数变化度,对高度改变的水温参数采用线性回归方法评估其变化倾向,基于F检验法检验回归效果。分析四大家鱼自然繁殖时间与水温参数变化的关系,研究四大家鱼自然繁殖对水温过程变化的响应。结果表明：整体水温改变度达44.2%,高度改变的水温参数有7个,分别是1、4、10、11、12月平均水温、最低水温出现日期、水温达到18℃日期,水温改变度达87.9%、75.8%、74%、100%、100%、74%、89.9%,说明三峡水库蓄水后坝下水温发生显著变化;下泄水温在消落期4、5份偏低趋势明显,较蓄水前平均降低2.3、1.7℃,由于4、5月水温偏低导致水温达到18℃的日期发生显著变化,由蓄水前4月19日推迟至蓄水后5月4日,平均推迟15 d。四大家鱼自然繁殖时间与水温达到18℃的日期密切相关,下泄水温偏低造成其自然繁殖时间推迟,首次产卵推迟至5月中旬,整个繁殖季节由4-7月份压缩至5-6月份,研究成果为三峡水库开展生态调度提供科学支撑。     

高炉铁口孔道侵蚀过程的模拟

从流体动力学的角度出发,建立高炉出铁口处流动的数学模型.基于对孔口出流出口处流线公式的推导并作适当修正,计算出铁时铁口孔道的侵蚀形状,并描述了侵蚀过程.通过水模型实验和模拟计算的方法分别模拟出侵蚀过程.实验与模型假设较为符合,可以为铁口区的维护以及推荐适宜的打泥量提供参考.     

非线性控制系统综合的频域逆系统方法研究

提出一种不需已知系统微分方程模型的非线性系统综合方法。首先得到对象非线性传递函数的估计,然后利用非线性补偿算法构造前馈补偿器,使复合系统具有近似线性系统的特性,最后采用常规线性系统反馈控制的方法进行控制。仿真结果表明,所提出的频域逆系统综合方法比一般非线性系统自适应控制方法有效。     

页岩水平井环保型多硅基水基钻井液技术

针对页岩水平井钻井过程中使用水基钻井液时面临的井壁易失稳、钻具摩阻扭矩大,井眼清洁困难等技术难题,通过引入硅酸钾钠、有机硅改性腐植酸钾盐、聚倍半硅氧烷等硅基处理剂,构建了环保型多硅基水基钻井液体系.该体系所用处理剂EC50>3×104 mg/L,为无毒级别,抗温180℃,流变性能稳定,具有良好的抑制性、封堵性和润滑性,...     

中航时平台惯导系统导航精度的全误差评估方法

平台惯导系统(PINS)初始对准误差和标定参数重复性是评估PINS精度的主要参数.应用给定精度评定指标无法准确评估PINS导航精度,PINS全误差导航模型能够准确描述PINS误差传播过程,但对多批次中航时PINS精度评估需消耗大量时间,缺乏实用性.结合实际应用中需要对每一台PINS中航时导航精度进行快速准确评估的需求,通过对PINS全误差导航模型传播规律进行分析,得到PINS误差参数对导航精度的单项评估公式和简化综合评估公式.数值仿真验证表明:该方法能够对中航时PINS导航精度进行快速准确估算,在PINS选择中具有很好的实用性.同时该方法可以指导惯导系统生产调试,找到影响惯导系统的主要误差因素,对改进设计、提高精度和精度评定具有参考价值.     

Biomimetic Engineering of a Scavenger‐Free Nitric Oxide‐Generating/Delivering System to Enhance Radiation Therapy

Nitric oxide (NO) is a potent tumor‐cell radiosensitizer but it can be readily scavenged by hemoglobin (Hb) in vivo. A biomimetic incubator that can generate and deliver NO in a scavenger (Hb)‐free environment to enhance its radiosensitizing effect to maximize its efficacy in radiotherapy is proposed. This NO incubator comprises a poly(lactic‐co‐glycolic acid) (PLGA) hollow microsphere (HM) that contains an NO donor (NONOate) and a surfactant molecule (sodium caprate, SC) in its aqueous core. In acidic tumorous environments, the PLGA shell of the HM allows the penetration of protons from the outside, activating the hydrolytic cleavage of NONOate, spontaneously generating NO bubbles, which are immediately trapped/stabilized by SC. The SC‐stabilized NO bubbles in the HM are then squeezed through the spaces of its PLGA matrices by the elevated internal pressure. Upon leaving the HM, the entrapped NO molecules may passively diffuse through their SC‐stabilized/protected layer gradually to the tumor site, having a long‐lasting radiosensitizing effect and inhibiting tumor growth. The entire process of NO generation and delivery is conducted in a scavenger (Hb)‐free environment, mimicking the development of young ovoviviparous fish inside their mothers' bodies in the absence of predators before birth.     

Density-controllable growth of SnO2 nanowire junction-bridging across electrode for low-temperature NO2 gas detection

The junction-bridging structure of metal oxide nanowires (NWs) improves gas-sensing properties. In this study, an on-chip growth method was used to fabricate gas sensors, it easily and effectively controls NW junctions. SnO₂ NWs were synthesized by thermal evaporation at 800 °C with tin powder as the source. The density of the NW junctions was controlled by changing the mass of the source material. A source material with large mass yielded high-density NW junctions. With electrode spacing of 20 μm, NW junctions were formed from the source material of larger than 2 mg. Gas sensing results revealed that the junction sensors exhibited a good response to NO₂ gas at a concentration of 1–10 ppm. The sensors exhibited a good response to NO₂ gas at low temperature of up to 100 °C and short response–recovery time (~20 s). The sensors also had good selectivity to NO₂ gas. The response (R _gas /R _air) to 1 ppm NO₂ was as high as 22 at 100 °C, whereas the cross gas responses (R _air /R _gas) to 10 ppm CO, 10 ppm H₂S, 100 ppm C₂H₅OH, and 100 ppm NH₃ were negligible (1.1–1.3).     

催化裂化火炬系统的一些改进措施

针对原长庆第一助剂厂小型催化裂化装置火炬系统阻火器易堵塞、点火器频繁失效、火炬易熄灭等问题,重新设计了阻火器阀组,采用"低位点火、阶梯引燃"的方法降低点火头的安装高度,用开有断续长条孔的不锈钢管对所有点火弯管火嘴和长明灯火嘴进行圈闭以起到挡风稳焰的作用.这些简单有效的改进,提高了火炬系统安全保障的可靠性.