火源功率对竖井负压控烟效果影响的实验研究

基于竖井的烟囱效应原理,利用小尺寸实验台开展了一系列实验,通过改变油盘的尺寸,对竖井内的烟气温度、压力、速度以及通风口处的压力、气流速度进行测量,研究了火源功率对房间利用竖井进行负压控烟效果的影响。实验结果表明:一方面随着火源功率的增大,室内温度升高,热烟气形成的热压增大,使烟气向外膨胀;另一方面,竖井底部的烟气温度升高,竖井底部的负压值增大,烟囱效应增强,排烟速度增大,新鲜空气补入的速度增大,逐渐抑制住烟气从通风口向外溢出,达到了负压控烟的效果。     

多层采空区流场局部动态平衡数学建模分析

针对大同矿区浅埋深、多煤层群、近距离、两硬条件下开采形成的多层采空区极易发生自燃的问题,进行风流流场调压分析,以达到控制采空区遗煤自燃及防止有害气体流人工作面的目标.建立了多层采空区流场调压数学模型,得出工作面风压调节的最优参数,结合工程实际分析,确定了多层采空区流场调压需要达到的预期效果.提出多层采空区流场局部动态平衡的调压方法,结合达西线性渗流定律,确定了多层采空区流场达到局部动态平衡的调压允许范围,并提出调压自动控制方法.     

基于离线采集模式的高低温低气压试验箱校准技术的研究

针对高低温低气压箱校准技术展开研究,分析了传统校准方案的不足之处,提出了一种基于离线采集模式的高低温低气压试验箱温度、压力校准方案,并结合虚拟仪器、数据库与MATLAB,完成了该方案的设计与实现。最后通过实验验证了该方案的可靠性与可行性,并应用到环境与可靠性工作中。     

常压下煤对N2/CO2/CH4单组分气体吸附特性研究

为了研究常压不同条件下煤样对N2/CO2/CH4单组分气体的吸附特性,以Langumir单分子层吸附模型为依据,对其吸附阶段进行划分,选择长焰煤、气肥煤和无烟煤分别进行了单组分气体吸附试验,探讨不同试验条件对煤吸附量的影响。结果表明:在常压阶段,煤对单组分气体的吸附规律服从Langumir单分子层吸附模型的第一阶段,吸附量与压力正相关;煤的变质程度、吸附温度及压力和吸附气体的种类是影响吸附量的主要因素,并在不同情况下对煤吸附量的影响程度不同;高低变质煤样对吸附量的影响大,而中等变质程度的影响小;温度是低压阶段影响吸附量的主要因素;吸附气体种类对吸附量的影响是由于其自身物化性质差异,相同试验条件下煤对3种单组分气体的吸附量从大到小为CO2、CH4、N2。     

Unveiling soil degradation and desertification risk in the Mediterranean basin: a data mining analysis of the relationships between biophysical and socioeconomic factors in agro-forest landscapes

Soil degradation and desertification processes in the Mediterranean basin reflect the interplay between environmental and socioeconomic drivers. An approach to evaluate comparatively the multiple relationships between biophysical variables and socioeconomic factors is illustrated in the present study using the data collected from 586 field sites located in five Mediterranean areas (Spain, Greece, Turkey, Tunisia and Morocco). A total of 47 variables were chosen to illustrate land-use, farm characteristics, population pressure, tourism development, rainfall regime, water availability, soil properties and vegetation cover, among others. A data mining approach incorporating non-parametric inference, principal component analysis and hierarchical clustering was developed to identify candidate syndromes of soil degradation and desertification risk. While field sites in the same study area showed a substantial similarity, the multivariate relationship among variables diverged among study areas. Data mining techniques proved to be a practical tool to identify spatial determinants of soil degradation and desertification risk. Our findings identify the contrasting spatial patterns for biophysical and socioeconomic variables, in turn associated with different responses to land degradation.     

Dynamic response and effect of apertures on explosion parameters of flameproof apparatus

Explosion parameters for closed flameproof apparatus are changed when apertures like gap (e.g. push button) and porous structures (breathing element) are introduced on the cover or wall of the flameproof enclosures. Similarly, an interconnecting tube between two enclosures, results in significant change in explosion parameters. It is observed that the maximum explosion pressure, maximum rate of pressure rise and severity index are higher for enclosures with apertures on cover or body than that of enclosures without apertures. In case of two interconnected identical enclosures, the explosion parameters are increased in the secondary enclosure and higher than that of primary enclosure and also of isolated enclosure.     

Theoretical estimation of the lower flammability limit of fuel-air mixtures at elevated temperatures and pressures

We present an approach for predicting the lower flammability limits of combustible gas in air. The influence of initial pressure and temperature on lower flammability limit has been examined in this study. The lower flammability limits of methane, ethylene and propane in air are estimated numerically at the pressure from one to 100 bar and the temperature from ambient to 1200 K. It was found that the predicted LFLs of methane, ethylene and propane decrease slightly with the elevated pressure at the high temperature. The LFLs variation for methane-air mixture is 0.17, 0.18, 0.18 volume% with the initial pressure from one to 100  bar at the initial temperature of 800 K, 1000 K and 1200 K respectively, which is significantly higher than that at lower temperature. And the LFL of methane-air mixture at 1200 K and 100 bar reaches 1.03 volume% which is much lower than that at 1 bar and ambient temperature. On the other hand, the LFLs variation is 0.11–0.12 volume% for ethylene-air mixture and 0.06–0.07 volume% for propane-air mixture with the initial temperature from 800 K to 1200 K at the same range of pressure. The LFL values at high temperatures and pressures represent higher risk of explosion.     

氨制冷系统的压力管道安全

氨制冷系统压力管道在特定的环境和特定的工作参数下运行,压力管道的安全性能与设计、安装、检验试验和使用密切相关。关注氨制冷系统压力管道在设计、安装、检验试验和使用方面常出现的问题,有针对性的整改,对预防和提高氨制冷系统压力管道的安全性具有重要意义。     

高效降解青霉素菌的筛选鉴定及降解效果研究

从哈尔滨制药总厂的青霉素发酵药渣中富集筛选出6株青霉素耐受菌株,经驯化后,采用高效液相色谱法检验其对青霉素的降解效率,经比较得到一株青霉素高效降解菌株,编号为JZ6。青霉素浓度300 mg/L,30℃,p H6.7,121 r/min条件下恒温震荡培养24 h后,在青霉素做唯一碳源情况下,青霉素几乎不被降解,外加碳氮源后降解率可达到99.98%。对其进行电镜扫描和16SrDNA序列分析,鉴定其属于洋葱伯克霍尔德菌属(Burkholderia cenocepacia),16SrDNA序列长度为1451bp,在Gen Bank登录号为KF826288。     

Interactive response of photosynthetic characteristics in Haloxylon ammodendron and Hedysarum scoparium exposed to soil water and air vapor pressure deficits

C₄ plants possess better drought tolerance than C₃ plants. However, Hedysarum scoparium, a C₃ species, is dominant and widely distributed in the desert areas of northwestern China due to its strong drought tolerance. This study compared it with Haloxylon ammodendron, a C₄ species, regarding the interactive effects of drought stress and different leaf–air vapor pressure deficits. Variables of interest included gas exchange, the activity levels of key C₄ photosynthetic enzymes, and cellular anatomy. In both species, gas exchange parameters were more sensitive to high vapor pressure deficit than to strong water stress, and the net CO₂ assimilation rate (A_n) was enhanced as vapor pressure deficits increased. A close relationship between A_n and stomatal conductance (g_s) suggested that the species shared a similar response mechanism. In H. ammodendron, the activity levels of key C₄ enzymes were higher, including those of phosphoenolpyruvate carboxylase (PEPC) and nicotinamide adenine dinucleotide phosphate-malate enzyme (NADP-ME), whereas in H. scoparium, the activity level of nicotinamide adenine dinucleotide-malate enzyme (NAD-ME) was higher. Meanwhile, H. scoparium utilized adaptive structural features, including a larger relative vessel area and a shorter distance from vein to stomata, which facilitated the movement of water. These findings implied that some C₄ biochemical pathways were present in H. scoparium to respond to environmental challenges.