A Novel Low Air Pressure-Assisted Approach for the Construction of Cells-Decellularized Tendon Scaffold Complex

Objective The goal of this study was to develop a decellularized tendon scaffold(DTS)and repopulate it with adipose-derived stem cells(ADSCs)assisted by low air pressure(LP).Methods The porcine superficial flexor tendons were processed into the DTSs using a combination of physical,chemical,and enzymatic treatments.The effectiveness of decellularization was verified by histological analysis and DNA quantification.The properties of the DTSs were evaluated by quantitative analysis of biochemical characterization,porosimetry,in vitro biocompatibility assessment,and biomechanical testing.Subsequently,the ADSCs-DTS complexes were constructed via cell injection assisted by LP or under atmospheric pressure.The differences in cell distribution,biomechanical properties,and the total DNA content were compared by histological analysis,biomechanical testing,and DNA quantification,respectively.Results Histological analysis confirmed that no cells or condensed nuclear materials were retained within the DTSs with widened interfibrillar space.The decellularization treatment resulted in a significant decrease in the content of DNA and glycosaminoglycans,and a significant increase in the porosity.The DTSs were cytocompatible in vitro and did not show reduced collagen content and inferior biomechanical properties compared with the fresh-frozen tendons.The assistance of LP promoted the broader distribution of cells into the adjacent interfibrillar space and cell proliferation in DTSs.The biomechanical properties of the scaffolds were not significantly affected by the recellularization treatments.Conclusion A novel LP-assisted approach for the construction of cells-DTS complex was established,which could be a methodological foundation for further bioreactor and in vitro studies.

The Influence of Atmospheric Pressure on Air Content and Pore Structure of Air-entrained Concrete

To study the effect of atmospheric pressure on the properties of fresh and hardened airentrained concrete, three kinds of air entraining agents were used for preparing air-entrained concrete in the plateaus(Lhasa, 61 kPa) and the plains(Beijing, 101 kPa). Air content, slump, compressive strength and pore structure of the three air-entrained concretes were tested in these two places. It is found that the air content of concrete under low atmospheric pressure(LAP) is 4%-36% lower than that of concrete under normal atmospheric pressure(NAP), which explaines the decrease of slump for air-entrained concrete under LAP. Pore number of hardened concrete under LAP is reduced by 48%-69%. While, the proportion of big pores(pore diameter >1 200 μm) and air void spacing factor are increased by 1.5%-7.3% and 51%-92%, respectively. The deterioration of pore structure results in a 3%-9% reduction in the compressive strength of concrete. From the results we have obtained, it can be concluded that the increase of critical nucleation energy of air bubbles and the decrease of volumetric compressibility coefficient of air in the concrete are responsible for the variation of air content and pore structure of concrete under LAP.

Analysis of a Large Scale Cold Air Weather Process in China during January 2021

This study uses data provided by the National Meteorological Information Center of China, Japan Meteorological Agency (JMA) and National Oceanic Atmospheric Administration (NOAA) Physical Sciences Laboratory of the USA to analyze a cold air weather process at the beginning of January 2021. Synoptic analysis is mainly used to summarize synoptic laws or patterns based on observational data, and describe and infer weather processes. The main conclusions are as follows: The cold air travels south along the northwest path, affecting most of China. During the cold wave process, the first cold air is weak, which has a certain cooling effect on northern China. The second cold air was guided by the low vortex, the accumulation in the transverse groove of Mongolia was strengthened, and the cooling effect was significant. The southwest jet showed an increasing trend, and the water vapor transport conditions were good. However, due to the relatively gentle southern branch system, the warm and humid air flow was weak and the precipitation level was small. The purpose of this study is to better understand a large-scale cold air weather process in January 2021 in China.

低温等离子体空气消毒机在骨科病室的应用效果

目的 针对医院骨科病室环境的常态化消毒需求,研制基于低温等离子体技术的空气消毒机,探究其在骨科病室患者住院、家属陪同、医护治疗的动态环境中的空气消毒效果。方法 以西安交通大学第二附属医院骨科病室环境为研究对象,采用自制的低温等离子体空气消毒机进行病室空气消毒,利用安德森六级筛孔空气碰撞式微生物采样器对室内空气中微生物浓度进行采样,分析低温等离子体消杀对病室空气中不同种类微生物的影响,揭示该技术对空气中悬浮微生物的消杀机制。结果 利用低温等离子体协同催化剂对病室环境进行间歇式消毒,能够保持室内臭氧浓度低至5 ppbv以内,消毒3 h后病室空气中自然菌的菌落总数减少至约150 CFU/m^(3),消亡率达92.35%;消杀2 h后马赛血杆菌的消亡率达100%;消杀3 h后人葡萄球菌、蜡样芽孢杆菌、霉菌、藤黄微球菌的消亡率分别为90.48%、80.90%、87.50%和92.82%。结论 利用低温等离子体协同催化剂的空气消毒机对病室动态环境进行间歇式消毒,室内臭氧浓度达到了一级国家标准线,在有效控制臭氧产生造成二次污染的同时,可高效杀灭空气中悬浮微生物,病室环境接近《GB 15982-2012医院消毒卫生标准》中Ⅰ类环境标准。等离子体-催化协同消杀具有高效消毒和人机共存的技术优势,可以在保障病室内空气质量安全的同时,减轻护理人员的工作量,是辅助甚至替代现有物理化学手段的有效方法。

Preparation and performance of a cold gas dynamic sprayed high-aluminum bronze coating

By mixing preheated high-aluminum bronze powders with different amounts of Al_2O_3 powder, a low-pressure cold-sprayed coating was prepared and sprayed onto a Cr12MoV steel substrate. The hardness of the coating and the bonding strength between the coating and the substrate were tested with a HV-1000 microhardness tester and a mechanical universal testing machine. The surface microstructure, cross-section and tensile fracture surface of the coating were observed with a scanning electron microscope(SEM). Correspondingly, the influences of the preheat treatment temperature of the bronze powder and the Al_2O_3 content on the coating performance were investigated. The results indicate that the hardness of bronze powders decreased and the coating deposition rate increased after the preheating treatment of the bronze powder. The Al_2O_3 content in the mixed powders contributed to the deformation of bronze powders during the spraying process. This trend resulted in varied performance of the coating.

Analysis on Extreme Gale of Capital Airport

Observation data of extreme gale in Capital Airport during 1976-2013 were analyzed,and climate characteristics of extreme gale in Capital Airport were summarized. Moreover,three extreme gale weather processes with larger influences on December 10,2010,November 22,2011 and March 9,2013 were contrasted and analyzed,and results showed that extreme gale in Capital Airport mainly appeared during March-April or December-January. Occurrence frequency of extreme gale was the most from late afternoon to evening,and the minimum was from night to morning,while peak appeared during 14:00-15:00. Extreme gale of Capital Airport was dominated by northwest gale at the rear of cold front,and the peak occurred at the wind direction of 330°. The common effect of strong cold high pressure going south at the rear of ground cold front and highaltitude transverse trough turning vertical was main cause of extreme gale in Capital Airport,and momentum transmission below 500 hP a also had an important effect in the generation of extreme gale.

The effect of living environment on developmental disorders in cold regions

Developmental disorders(DDs)are a kind of chronic maladies,which can cause serious irreversible detriment to children’s physical and mental health.It is predominantly regulated by the interaction of environment and heredity.Cold regions are mainly located in the high latitudes of China.Their living environment is characterized by frequent cold wave,huge temperature difference,severe air pollution,high calorie diet,less exercise,smoking,drinking,etc.In recent years,substantial advances have been made in studies of the correlation between the living environment features in cold regions and the DDs.Accordingly,this article reviews the impact of the peculiar living environment of cold regions on DDs,with a view to provide fresh prevention strategies for reducing the morbidity of DDs in China cold regions by ameliorating living environment.

高海拔潮气量双环PID控制系统研究

为解决高海拔地区气压降低导致急救呼吸机潮气量控制精度下降的问题,提出了双环PID潮气量控制系统。该系统采用气压补偿型PID控制器调整风机转速,并辅以积分分离式PID控制器,以实现对气流速度的精确控制。在实际海拔4370 m、大气压59 kPa的环境中,系统性能测试表明,相较于单环PID控制,双环控制系统在高海拔条件下表现出快速响应和无超调的卓越性能。平均气流速度输出误差为3.19%,最大误差为4.1%,优于现有临床设备的准确性。这一技术突破不仅提供了高海拔急救呼吸机潮气量控制的有效解决方案,也为特殊环境下的通气控制技术发展贡献了重要参考。

低压磨料空气射流切槽辅助TBM滚刀破岩规律

全断面隧道掘进机(TBM)在矿井开采中应用逐渐推广,坚硬围岩巷道与隧道施工过程中存在掘进困难、刀具损耗严重的问题,如何实现高强度高磨蚀性地层安全掘进对于指导地下工程建设和能源开发等具有重要意义。为此,提出低压磨料空射流切槽辅助滚刀破硬岩技术思路。基于低压磨料空气射流辅助滚刀破岩综合实验平台,研究不同切槽深度对滚刀破岩刀具受力和岩石破碎的影响。采用PFC数值分析不同切槽深度下刀具垂直载荷、裂纹扩展、比能耗和岩石应力场等变化规律,进一步解释切槽辅助滚刀破岩过程中刀具受力减小原因。形成以下主要结论:切槽底端是滚刀破岩过程应力集中区域,主裂纹从滚刀与岩石作用位置到切槽底端扩展贯通,当切槽深度大于8 mm后形成滚刀压痕处高、切槽底端低的“岩脊”状岩石破坏特征,随着切槽深度增加,岩脊高度逐渐变大。切槽后主裂纹与切槽边缘和岩石断面贯通,呈现三角状岩石破碎体,切槽深度越大,岩石块状破碎体的体积越大,同时滚刀最大垂直载荷越小,数值模拟结果与相关实验结果具有一致性。低压磨料空气射流切槽为20 mm时,滚刀最大垂直载荷为不切槽时的68%。切槽过后滚刀破岩过程中刀具两侧岩石应力减小,进一步使滚刀破岩过程刀具传递力的大小降低并朝着切槽底端传递,切槽起到移除侧向约束的作用,降低了刀具贯入的垂直载荷,形成大块状的岩石破碎体,从而减小破岩比能耗。

低气压直流转换开关开断能力研究

直流转换开关被广泛应用于特高压直流输电工程,用于系统运行方式的切换。其多采用无源自激振荡的技术路线,具有结构简单、性能可靠等优点。该文以直流转换开关为研究对象,通过SF6气体低气压特性分析,结合直流转换开关开断过程灭弧室的气流场仿真分析结果,优化气流通道,设计出适用于低气压环境的大容量开断装置。采用了低频振荡电流法等效直流电源进行直流转换开关的电流转换能力验证,分别在不同电流、不同气体压力时进行电流转换试验。由试验结果可知,随着开断装置充气压力的降低,电流转换的能力下降率达到10%~25%,且燃弧时间较长。通过仿真和试验研究,为低气压条件下直流转换开关的设计和电流转换能力评估奠定了基础。

不同强度冷空气事件特征及对中国冬季温度的影响

利用1979-2019年美国国家环境预报中心-国家大气研究中心再分析资料,采用冷空气爆发指数和二维阻塞高压指数,筛选出3类不同强度的冷空气事件:高-中纬(H-M)、高-低纬(H-L)、中-低纬(M-L)事件和乌拉尔山阻塞高压(UBH)事件,分析冬季3类冷空气事件的演变特征、UBH背景下冷事件的基本特征及其对中国的降温效果.结果表明,H-M和M-L事件的频次在2000年前呈下降趋势,M-L事件的强度总体上呈减小趋势.UBH背景下,66.1%的冷空气事件强度较强(冷空气爆发指数≥2),46.4%的冷空气事件持续时间为1 d,H-L事件的平均持续时间最长(3.4 d).3类事件的冷空气通量在高纬欧亚大陆上空表现为由西伯利亚反气旋和东亚北部气旋组成的偶极型分布;阻塞高压影响下,偏北风加强,冷空气南下入口处的冷气团总量距平在事件开始前后最强达到110 hPa以上,50°N的温度负异常也受影响变得更加深厚,可以延伸到500 hPa以上;强的负热含量距平与强的地面温度异常对应,尤其在冷事件开始当天,50°N的负热含量距平远大于30°N.3类事件发生时,降温主要集中在中国北部和东部地区,H-L事件的降温效果最强,容易形成高纬至华南的穿透性冷空气事件.

混凝土冻融破坏机理及寿命预测方法

冻融破坏是我国严寒或寒冷地区混凝土的主要破坏形式,分析混凝土的冻融破坏过程、明确混凝土的冻融破坏机理、提出混凝土冻融损伤寿命预测方法对混凝土结构耐久性设计至关重要。本文根据混凝土结构的冻融破坏特点,从整体水冻和表面盐冻两方面阐述了混凝土的冻融破坏机理,论述了冻融破坏机理在不同混凝土结构中的适用性,分析了高原低气压地区混凝土冻融破坏更加严重且引起困难的原因;系统总结了基于试验数据和数值模拟的混凝土冻融损伤寿命预测方法,分析了两种寿命预测方法的优势和不足,以期为寒区混凝土的抗冻性设计提供参考。

阵列低环温空气源热泵外流场模拟研究

建立了无墙面阻碍和有墙面阻碍情况下低环境温度空气源热泵六列四行的阵列物理模型,对以261.15 K为名义工况下的空气源热泵外环境流场进行三维数值模拟。对比研究不同水平风速下蒸发器换热面入口空气温度和换热量,分析冷风回流现象对低环温空气源热泵传热性能的影响,指出最恶劣工况机组的位置。环境风存在阻碍风机出口冷空气的扩散,使风机出口偏转角增大,导致冷空气在风机上部堆积,阵列内部以及背风侧的机组冷风回流现象更加明显。结果表明:当机组横向间距为0.6 m时,水平风速分别从0 m/s增至5 m/s,阵列机组最低入口空气温度比环境温度低2.44~3.69 K,平均换热量下降1%~6.2%,平均入口空气温度比环境温度低0.78~1.57 K;当机组距墙间距为0.6 m时,水平风速分别从0 m/s增至5 m/s,阵列机组最低入口空气温度比环境温度低3.51~4.14 K,平均换热量下降5.9%~11.5%,平均入口空气温度比环境温度低1.29~1.98 K。在此基础上对不同横向间距、不同距墙间距下阵列空气源热泵进行模拟,结果表明:增大横向间距或距墙间距均能改善阵列低环温空气源热泵机组的换热。当横向间距增至1.2 m,阵列机组平均换热量可达原来机组换热量的96.5%以上;距墙间距增至1.2 m,阵列机组平均换热量可达原来机组换热量的91.3%以上。横向间距或距墙间距为1.2 m为较好安装间距。

下向低浓钻孔“抽-注”排水排渣抽采一体化技术研究

为了防止永夏矿区陈四楼煤矿煤与瓦斯突出事故的发生,在采用水力排渣钻孔进行抽采瓦斯时,发现在钻孔内存在着大量的水和煤渣,堵塞了煤体内部的孔隙通道,对煤层瓦斯运移和钻孔孔壁的稳定性产生不利影响,从而严重影响了瓦斯抽采的效果。针对煤矿急需解决的俯孔排水排渣问题,提出采用压风吹孔技术,将孔内水和煤渣带出孔外,疏通钻孔堵塞通道。该技术在陈四楼煤矿井下现场应用效果良好,吹孔后钻孔平均在抽浓度由11.86%提升到了18.73%~56.38%,低浓钻孔提升效果明显;代替了以往水力排渣钻进技术,达到高效抽采瓦斯、保证煤矿安全生产的目的,对钻孔抽采瓦斯过程中能够及时排出水和煤渣有一定指导意义。在此基础上,形成的一套下向低浓钻孔“抽—注”排水排渣一体化技术及工艺,为下向低浓钻孔排水排渣工作提供参考借鉴。

酒钢265 m^(2)烧结机风量控制优化应用

在传统的钢铁行业中自动化、数字化、智能化的应用是降本增效的有效手段,也是传统产业继续发展的必然趋势。本研究通过烧结机风量分布的自动控制及烧结机密封板的拓展应用,降低了烧结机有害漏风,优化了烧结机风量分布,有效提升了烧结矿产、质量。

新风空调一体机在夏热冬冷地区超低能耗建筑中的应用

被动式超低能耗建筑具有高能效、高舒适性的特点,已成为助力实现“双碳”目标的重要举措。夏热冬冷地区夏季高温炎热,冬季阴冷潮湿,新风空调一体机能满足该地区供暖、供冷、通风与除湿等多种需求。以湖南省株洲市某被动式超低能耗建筑项目为例,详细阐述了新风空调一体机在该类项目中的设计与应用,并对其室内热环境和能源消耗进行了监测与分析。研究结果可为相关被动式超低能耗建筑项目的发展提供参考。

基于单晶硅的压阻效应压力传感器低气压输出异常分析

某型号压阻式压力传感器在实际工程中出现低气压段输出偏高现象,结合该传感器的结构组成,建立导致该现象的故障树,依据故障树逐一进行排除,采用外观检查、绝缘电阻测试、替换可能的故障部件等方式,确定故障出现在压力芯体中;进一步对芯体进行分析,通过显微镜、手捻法等方式方法,确定硅油中存在气泡导致传感器低气压段输出偏高,并对气泡中压力与输入压力之间的3类关系进行分析,得到输入压力小于气泡内部压力时,低气压段输出偏高故障现象的失效机理,并通过在空气环境下封装压力芯体,复现了故障现象,并建议增加对压力芯体进行低温低气压筛选试验。

冷气模拟火箭级间分离试验憋压过程仿真研究

级间热分离是固体火箭飞行过程中的核心技术之一,传统的“三合一”试验通常包含了上面级发动机、伺服机构和分离系统三个主要分系统,对实际工程研制来说成本高、周期长,只可用于系统级性能验证试验,不适用于摸索性质的研制性试验。以冷气模拟火箭级间分离试验这一新型地面试验方法为研究背景,结合理论模型、数值仿真以及地面试验验证,对级间分离初始憋压阶段的内流场进行仿真,揭示级间段内气体压强变化规律,阐明冷气模拟火箭级间分离的试验机理,并通过数值模拟分析研究不同蓄压罐初始压力、不同蓄压罐容积、不同管道面积以及不同的级间段容积对气体压力变化的影响,为冷气模拟级间分离试验的设计提供解决方法。

寒冷地区农村低温空气源热泵运行特性试验研究

为获得低温型空气源热泵在北方寒冷地区的实际运行特性,对河北省保定市一典型农村住宅安装的空气源热泵机组进行了为期3 d的供暖工况实测。分析测试数据发现:实测室外工况与机组额定工况差距显著,机组平均制热量与平均COP值高于额定值的主要原因是室外温度高于机组额定工况下的室外干球温度。在冬季阴雨雪天气工况下机组的平均制热量、不包含除霜情况下的平均COP值较晴天工况分别下降60.7%、53.4%,反映了机组在阴雨雪天气工况下的制热效果不及晴天工况。研究结果表明:低温空气源热泵机组制热量可以满足冬季供暖的基本需求,室内温度难以达到供暖设定温度是由机组除霜、压缩机频繁停机及建筑保温性能不佳所致。