隧道内偏置火源顶棚近壁面温度边界层效应研究

基于隧道火灾不同横向火源位置的非对称卷吸影响,通过模拟计算分析了中心火源和偏置火源产生的烟气沿纵向最大温升变化规律,研究了顶棚下方近壁面区域内的不同温度分布,提出偏置火源纵向空间最大顶棚温升公式。结果表明:在壁面黏性作用下,沿纵向蔓延的烟气最高温度在顶棚下方呈现“温度边界层”分布;随着火源位置的偏移,下游出现偏置距离起主导作用影响温度衰减的区域,衰减速度相较于中心火源逐渐降低;火源下游近壁面最高温度位置逐渐远离顶棚后趋于稳定。研究结果对于排烟方式的设计以及空间通风效果的提升有着重要意义。

非对称Lens-walled CPC设计与光学性能模拟研究

提出一种新型的可与建筑南墙固定结合的非对称Lens-walled CPC,充分利用全反射、折射及镜面反射特性,在保证一定聚光比条件下,获得较大的接收角及较高光学效率。通过软件模拟,对其光学性能进行分析,并与非对称镜面CPC进行光学对比。研究结果表明,非对称Lens-walled CPC与建筑相结合优势明显,是聚光太阳能利用与建筑相结合的有效途径之一。

基于Logit模型的城乡结合部不同车型安全性分析

与城市地区相比,城乡结合地区交通具有事故频发、严重程度高等特点,虽经多方努力但效果有限,已成为影响我国交通安全的重点瓶颈地区。采集某城市城乡结合地区近3年来的事故数据,引入车辆保护性和攻击性指标作为车型安全性指标,基于多分类有序Logit模型设计了城乡结合地区不同车型安全性分析方法,确定了各车型安全性,深入分析了各因素对车型安全性影响,并提出相关改善建议。

单细胞RNA测序解析普通小鼠和糖尿病小鼠全层皮肤缺损创面中CD34^(+)细胞的类型与功能

目的单细胞RNA测序解析普通小鼠和糖尿病小鼠全层皮肤缺损创面中CD34^(+)细胞的类型与功能。方法该研究为实验研究。构建CD34^(+)细胞谱系追踪小鼠,实现CD34^(+)细胞在荧光条件下可视化。取6只7~8周龄雄性CD34^(+)细胞谱系追踪小鼠(设为糖尿病组),腹腔注射链脲佐菌素构建糖尿病模型,于小鼠13周龄时在其背部制备全层皮肤缺损创面;另取6只13周龄雄性CD34^(+)细胞谱系追踪小鼠(设为对照组),在其背部制备全层皮肤缺损创面。伤后4 d,分别收集对照组3只小鼠和糖尿病组2只小鼠创面组织,消化制备单细胞悬液,采用荧光活化细胞分选法筛选出CD34^(+)细胞后进行单细胞RNA测序,采用R语言的Seurat 4.0.2程序通过降维可视化和细胞聚类分析CD34^(+)细胞类型并筛选注释各CD34^(+)细胞亚群的标记基因,对2组小鼠创面组织间CD34^(+)成纤维细胞(Fb)、平滑肌细胞、角质形成细胞(KC)、类软骨细胞的差异表达基因(DEG)进行京都基因与基因组百科全书(KEGG)和基因本体论(GO)富集分析,探索细胞功能。结果伤后4 d,2组小鼠创面组织中CD34^(+)细胞均包含7种细胞类型,具体为内皮细胞、Fb、KC、巨噬细胞、T细胞、平滑肌细胞和类软骨细胞,其中Fb细分为5个亚群。与对照组比较,糖尿病组小鼠创面组织中的CD34^(+)内皮细胞、Fb亚群1、Fb亚群4、KC、类软骨细胞占比升高,CD34^(+)Fb亚群2、Fb亚群3和平滑肌细胞占比下降。注释CD34^(+)类软骨细胞、内皮细胞、Fb亚群1、Fb亚群2、Fb亚群3、Fb亚群4、Fb亚群5、KC、巨噬细胞、平滑肌细胞、T细胞的标记基因分别为转移相关肺腺癌转录本1、脂肪酸结合蛋白4、Gremlin 1、补体成分4B、H19印记母源表达转录本、Dickkopf Wnt信号通路抑制剂2、纤维调节蛋白、角蛋白5、CD74分子、G蛋白信号调节蛋白5、可诱导T细胞共刺激分子。KEGG和GO富集分析显示,与对照组比较,糖尿病组小鼠伤后4 d创面组织中CD34^(+)Fb差异表达显著的DEG显著富集于炎症反应、细胞外基质(ECM)组装、细胞增殖调控、衰老相关条目(P值均<0.05),CD34^(+)平滑肌细胞差异表达显著的DEG显著富集于细胞迁移、凋亡过程、转录的正调控、吞噬体等条目(P值均<0.05),CD34^(+)KC差异表达显著的DEG显著富集于线粒体功能、转录、神经退行性疾病相关条目(P值均<0.05),CD34^(+)类软骨细胞差异表达显著的DEG显著富集于节律调控、ECM、病毒感染等相关条目(P值均<0.05)。结论CD34^(+)细胞在普通小鼠和糖尿病小鼠全层皮肤缺损创面愈合过程中均存在高异质性,2种小鼠创面间CD34^(+)细胞亚群差异表达显著的DEG显著富集的相关功能与创面愈合过程紧密相关。

Optical properties and cooling performance analyses of single-layer radiative cooling coating with mixture of TiO_(2) particles and SiO_(2) particles

Radiative cooling can achieve cooling effect without consuming any energy by delivering energy into outer space(3K) through"atmospheric window"(8–13 μm). Conventional radiative cooling coating with multi-layer structure was severely restricted during application due to its complex preparation process and high cost. In this study, a single-layer radiative cooling coating with mixture of TiO_(2) particles and SiO_(2) particles was proposed. The algorithm for calculating the radiative properties of the multi-particle system was developed. Monte Carlo ray-tracing method combined with that algorithm was used to solve the radiative transfer equation(RTE) of the single-layer radiative cooling coating with mixture of TiO_(2) particles and SiO_(2) particles.The effects of particle diameter, volume fraction and coating thickness on radiative cooling performance were analyzed to obtain the best radiative cooling performance. The numerical results indicated that the average reflectivity of the single-layer radiative cooling coating with mixture of TiO_(2) particles and SiO_(2) particles in the solar spectrum can reach 95.6%, while and the average emissivity in the "atmospheric window" spectrum can reach 94.9% without additional silver-reflectance layer. The average reflectivity in the solar spectrum and average emissivity in the "atmospheric window" spectrum of the single-layer radiative cooling coating with mixture of TiO_(2) particles and SiO_(2) particles can increase 4.6% and 4.8% compared to the double-layer radiative cooling coating. This numerical research results can provide a theoretical guidance for design and optimization of single-layer radiative cooling coatings containing mixed nanoparticles.

Design and Development of a Lens-walled Compound Parabolic Concentrator-A Review

Compound parabolic concentrator(CPC) is a representative among solar concentrators, one of whose disadvantage is that the concentration ratio limits the half acceptance angle. Based on this, researchers put forward a novel structure, named the lens-walled CPC. This paper reviews the design and development of lens-walled CPC. The structure of the symmetric and asymmetric lens-walled CPC and the improved ones are presented, and their indoor and outdoor performances are also illustrated. The lens-walled CPC has a larger half acceptance angle and a more uniform flux distribution that is suitable for PV application. Furthermore, the life-cycle assessment for building integrated with PV is performed and it shows that the energy payback time of such integrated system has a significant advantage. In addition, future research areas are also indicated that may provide more functions and more stable performance. The design methods and developmental directions given in this study would provide many references in solar optical research and solar concentrator optimization.

Performance Evaluation and Optimization of a Novel System Combining a Photovoltaic/Thermal Subsystem&an Organic Rankine Cycle Driven by Solar Parabolic Trough Collector

A novel coupling system that combines a photovoltaic/thermal(PV/T)subsystem and an Organic Rankine Cycle(ORC)driven by solar parabolic trough collector(PTC)is presented in this paper.The mathematical model is initially built.On the basis,the influence of area ratio of two collectors(PV/T and PTC)on the performance of system is discussed.The results show that the optimal area ratio of PV/T to PTC is 8:2,which can achieve the maximum energy output.Moreover,the performance of the coupling system and two independent systems(PV/T and ORC system)are compared and analyzed.The results show that the coupling system is more reliable and its total output energy(heat and electricity)is the highest,compared with the other two independent systems.The solar energy utilization efficiency of the coupling system is 40%higher than that of the other two independent systems in the steady-state simulation.Moreover,the annual output energy per unit area collector of the coupling system is 13%higher than that of the other two independent systems in the dynamic simulation.Furthermore,in the dynamic simulation of a typical day,the PV panels’temperature of the coupling system is 5℃–7℃ lower than that of the independent PV/T system.It means that the power generation efficiency of PV panels can be increased by 1.5%–3.5%.This study aims to explore the operation characteristics of the novel solar energy utilization coupling system and promote the development of renewable energy utilization models,which provides a reference for the design and optimization of related energy systems.

Experimental and Comparison Study on Two Solar Dish Systems with a High Concentration Ratio

Two high concentrating solar systems have been established with dish concentrator and plane-mirrors array concentrator.In the paper,the thermal performance has been experimentally studied with jet water cooling device and flat microchannel water-cooled device.The experimental results show that the maximum surface temperature difference of the dish concentrating system is greater than 20°C,while the plane-mirrors array system is lower than 4°C.It indicates that the plane-mirrors array concentrator has better uniformity.As the concentration ratio increases,the electrical efficiency of the concentrating photovoltaic system gradually decreases.When the concentration ratio is 200,the electrical efficiency of the photovoltaic system is 25%.The concentration ratio of 500 times or less is considered to be a suitable value,and then the electrical efficiency can still exceed 20%.It is found that the plane-mirrors array solar system is more suitable for the photovoltaic system than dish type system,which is only suitable for thermal power generation system.

Experimental Analysis of a Solar Energy Storage Heat Pump System

This paper introduces a novel solar-assisted heat pump system with phase change energy storage and describes the methodology used to analyze the performance of the proposed system.A mathematical model was established for the key parts of the system including solar evaporator,condenser,phase change energy storage tank,and compressor.In parallel to the modelling work,an experimental set-up of the proposed solar energy storage heat pump system was developed.The experimental data showed that the designed system is capable of meeting cold day heating demands in rural areas of Yanbian city located in Jilin province of China.In day-time operation,the solar heat pump system stores excess energy in the energy storage tank for heating purposes.A desired indoor temperature was achieved;the average coefficient of performance of solar heat pump was identified as 4.5,and the system showed a stable performance throughout the day.In night-time operation,the energy stored in the storage tank was released through a liquid-solid change of phase in the employed phase-change material.In this way,the provision of continuous heat for ten hours was ensured within the building,and the desired indoor air conditions were achieved.

儿童口咽部严重烫伤气管切开术后拔管困难一例

2016年11月4日,广州市红十字会医院收治1例伤后1 h入院的面颈部烫伤合并口咽部严重烫伤的1岁3个月男性患儿。伤后2 h患儿即出现上呼吸道梗阻表现,立即予以气管切开置管建立人工气道,并予以抗感染、补液、换药等对症治疗。伤后第10天,患儿拔管前试堵管过程中出现呼吸困难,难以拔管,继续予以呼吸机辅助通气、加强抗感染等对症治疗。伤后第17天予以调整拔管方案,拔管前30 min肌内注射苯巴比妥镇静、应用阿托品减少气道分泌物,之后拔管成功。经过21 d治疗,患儿痊愈出院。本病例强调了拔管困难的原因中儿童精神因素的重要影响,为临床处理儿童气管切开术后拔除气管套管提供了参考。

Special Issue for Building Energy Conservation and Renewable Energy Integration

With the development of society and the improvement of people’s living standards, the thermal comfort requirement of indoor environment is increasing, which leads to more and more energy consumption. It is essential to scientifically develop, strategically promote and practically implement building energy saving techniques.