Airborne bacterial assemblage in a zero carbon building: A case study

Currently, there is little information pertaining to the airborne bacterial communities of green buildings. In this case study, the air bacterial community of a zero carbon building (ZCB) in Hong Kong was characterized by targeting the bacterial 16S rRNA gene. Bacteria associated with the outdoor environment dominated the indoor airborne bacterial assemblage, with a modest contribution from bacteria associated with human skin. Differences in overall community diversity, membership, and composition associated with short (day‐to‐day) and long‐term temporal properties were detected, which may have been driven by specific environmental genera and taxa. Furthermore, time‐decay relationships in community membership (based on unweighted UniFrac distances) and composition (based on weighted UniFrac distances) differed depending on the season and sampling location. A Bayesian source‐tracking approach further supported the importance of adjacent outdoor air bacterial assemblage in sourcing the ZCB indoor bioaerosol. Despite the unique building attributes, the ZCB microbial assemblage detected and its temporal characteristics were not dissimilar to that of conventional built environments investigated previously. Future controlled experiments and microbial assemblage investigations of other ZCBs will undoubtedly uncover additional knowledge related to how airborne bacteria in green buildings may be influenced by their distinctive architectural attributes.     

基于自适应阈值活动语音检测和最小均方误差对数谱幅度估计的低信噪比降噪算法

针对低信噪比(SNR)环境下传统方法对声信号降噪的局限性，提出了一种联合自适应阈值活动语音检测（VAD）算法和最小均方误差对数谱幅度估计（MMSE-LSA）的实时降噪算法。首先，在VAD算法中通过基于能量概率最大值的概率统计来对背景噪声进行估计，对得到的背景噪声进行实时更新并保存；然后，将实时更新的背景噪声作为MMSE-LSA的参考噪声，并对噪声幅度谱进行自适应更新，最后进行降噪处理。通过在真实场景中对四类声信号进行实验，结果表明，该算法在保证对低SNR声信号的实时处理的情况下，相较于传统MMSE-LSA算法，降噪信号的SNR能够提高10~15 dB，且不存在信号过减的情况，可应用于实际工程。     

CO2对油田地下水环境中Q235钢和X70钢腐蚀行为的影响

为了探明辽河油田地下水环境中CO₂对Q235钢和X70管线钢的腐蚀规律,采用动电位极化技术及交流阻抗技术研究了不同CO₂浓度对该环境下两种钢腐蚀行为的影响,并利用光学显微镜对试样腐蚀界面进行表征。结果表明:随着CO₂浓度的增加,Q235和X70钢的交流阻抗图谱的半径均减小,腐蚀电流密度增大,腐蚀坑数量、深度和面积都增加,腐蚀敏感性增大。在低浓度CO₂环境下(CO₂含量为10%时),Q235钢的腐蚀敏感性比X70钢更高;而在高浓度CO₂环境下(CO₂含量为20%、40%、60%时),Q235钢的腐蚀速率反而较小,耐腐蚀性更好。     

磁性纳米材料处理含铀废水的研究进展

磁性纳米材料具有较强的化学稳定性、可再生回收、良好的吸附性能和易于分离等优点，在去除水溶液中的铀酰离子方面有广泛的应用前景。然而，磁性纳米材料也存在易团聚、易氧化等不足，通过表面修饰或改性等方法可改善其不足，提高其对废水中铀酰离子的去除能力，改善其吸附效果。本文通过总结近年来的相关研究资料，概括了磁性纳米材料的种类，归纳总结并比较了不同种类磁性纳米材料对含铀废水的去除能力及优势与不足，探讨了磁性纳米材料在含铀废水处理中的应用并对其机理进行了分析，阐述了磁性纳米材料去除溶液中铀酰离子的影响因素，简述了目前磁性纳米材料在处理含铀废水中有待解决的问题，并对其在分离放射性元素方面的应用前景进行了展望。     

基于介形类生态特征评价湖南某铀矿山地表水放射性环境

湖南某铀矿为我国一重要铀资源生产基地，长年的矿冶活动使该铀矿冶地域生态环境不可避免地遭到了一定程度破坏。本文以该铀矿冶地域介形类为研究对象，分析其分布与生态特征，并利用该生物评价本矿冶地域地表水放射性污染状况。结果表明，Cypridopsis vidua在溪流与河流中均有分布，Helerocypris incongruens仅发现于河流，两者丰度均不高。利用该两种介形类丰度及总丰度变化可指示水体铀浓度的变化，丰度越小，铀含量越大，反之亦然。Shannon-Wiener物种多样性指数与水体铀浓度呈明显负相关，表明也可利用介形类生物指数指示水体铀浓度。该生物指数明显偏低，说明该铀矿冶地域地表水环境质量需要改善，放射性污染应引起足够重视。     

陕北沙漠区浅埋厚煤层开采潜水位及生态响应

煤炭开采造成上覆岩层破裂、移动，破坏了矿区含（隔）水层结构，改变了地表水及地下水循环演化状态，对浅表层生态环境造成严重影响，引发一系列环境地质问题。为深入研究沙漠地区厚煤层开采给潜水位及生态环境造成的影响，以毛乌素沙漠金鸡滩矿为例，对水文地质条件进行了研究，采用数值模拟的方法，模拟了沙漠区厚煤层开采潜水位的变化，并通过采动潜水位监测数据验证了预测结果。调查分析了研究区及周边地表生态环境现状，预测采后潜水位基本满足植物生长需求，对生态环境影响不大。     

A test method for evaluating the thermal environment of underground coal mine refuge alternatives

Since 2009, the Mine Safety and Health Administration(MSHA) has required mines to install refuge alternatives(RAs) in underground coal mines. One of the biggest concerns with occupied RAs is the possible severity of the resulting thermal environment. In 30 CFR 7.504, the maximum allowable apparent temperature(AT) for an occupied RA is specified as 35 °C(95 °F). Manufacturers must conduct heat/humidity tests to demonstrate that their RAs meet the 35 °C(95 °F) AT limit. For these tests, heat input devices are used to input the metabolic heat of actual miners. A wide variety of test methods, sensors, and heat input devices could be used when conducting such tests. Since 2012, the National Institute for Occupational Safety and Health(NIOSH) has conducted over thirty 96-hour heat/humidity tests on four different RAs. This paper discusses the test equipment and procedures used during these investigations. This information is useful for RA manufacturers conducting RA heat/humidity tests, for other researchers investigating RA heat/humidity buildup, and for those who need to assess the thermal environment of any confined space where people may be trapped or are seeking refuge.     

A Hybrid Virtual Cloud Learning Model during the COVID-19 Pandemic

The COVID-19 pandemic has affected the educational systems worldwide, leading to the near-total closures of schools, universities, and colleges. Universities need to adapt to changes to face this crisis without negatively affecting students’ performance. Accordingly, the purpose of this study is to identify and help solve to critical challenges and factors that influence the e-learning system for Computer Maintenance courses during the COVID-19 pandemic. The paper examines the effect of a hybrid modeling approach that uses Cloud Computing Services (CCS) and Virtual Reality (VR) in a Virtual Cloud Learning Environment (VCLE) system. The VCLE system provides students with various utilities and educational services such as presentation slides/text, data sharing, assignments, quizzes/tests, and chatrooms. In addition, learning through VR enables the students to simulate physical presence, and they respond well to VR environments that are closer to reality as they feel that they are an integral part of the environment. Also, the research presents a rubric assessment that the students can use to reflect on the skills they used during the course. The research findings offer useful suggestions for enabling students to become acquainted with the proposed system’s usage, especially during the COVID-19 pandemic, and for improving student achievement more than the traditional methods of learning.     

PS-PVD热障涂层抗沙尘冲刷行为研究

为提高PS-PVD热障涂层的抗沙尘冲刷性能,采用等离子喷涂-物理气相沉积技术(PS-PVD)在粘结层表面制备7YSZ热障涂层,在大气环境下进行了抗沙尘冲刷试验,研究了PS-PVD热障涂层的冲刷行为及失效机制。通过等离子喷涂技术(APS)在PS-PVD热障涂层表面制备了一层致密层状涂层,重点研究了致密层厚度对PSPVD热障涂层抗冲刷失效性能的影响。结果表明PS-PVD热障涂层冲刷过程经历了快速、中速、慢速冲刷三个阶段。随着致密层厚度的增加,对PS-PVD热障涂层抗冲刷性能的提升愈加明显。当致密层厚度为5μm时,对PS-PVD热障涂层抗冲刷性能无明显影响;当致密层厚度为10μm时,PS-PVD热障涂层抗冲刷性能提高了约30%;当致密层厚度为20μm时,PS-PVD热障涂层抗冲刷性能约提高了4倍。     

The corrosion behavior and mechanism of X65 steel induced by iron‐oxidizing bacteria in the seawater environment

The corrosion behavior and mechanism of iron‐oxidizing bacteria (IOB) on X65 steel in seawater are studied. This study uses the methods of weight loss, electrochemical measurements, and surface analysis. The results show that the IOB increases the corrosion damage degree of steel. Pittings are observed in the medium with IOB. The potentiodynamic polarization curves show that the anodic reaction rate is accelerated in the corrosion process of IOB. The synergies in corrosion between the metal surface, abiotic corrosion products, and bacterial cells, and the pitting corrosion mechanism of X65 steel are discussed.