Carbon Black-Supported Single-Atom Co?N?C as an Efficient Oxygen Reduction Electrocatalyst for H2O2 Production in Acidic Media and Microbial Fuel Cell in Neutral Media

Single metal atom isolated in nitrogen-doped carbon materials (M N C) are effective electrocatalysts for oxygen reduction reaction (ORR), which produces H₂O₂ or H₂O via 2-electron or 4-electron process. However, most of M N C catalysts can only present high selectivity for one product, and the selectivity is usually regulated by complicated structure design. Herein, a carbon black-supported Co N C catalyst (CB@Co N C) is synthesized. Tunable 2-electron/4-electron behavior is realized on CB@Co-N-C by utilizing its H₂O₂ yield dependence on electrolyte pH and catalyst loading. In acidic media with low catalyst loading, CB@Co N C presents excellent mass activity and high selectivity for H₂O₂ production. In flow cell with gas diffusion electrode, a H₂O₂ production rate of 5.04 mol h⁻¹ g⁻¹ is achieved by CB@Co N C on electrolyte circulation mode, and a long-term H₂O₂ production of 200 h is demonstrated on electrolyte non-circulation mode. Meanwhile, CB@Co N C exhibits a dominant 4-electron ORR pathway with high activity and durability in pH neutral media with high catalyst loading. The microbial fuel cell using CB@Co N C as the cathode catalyst shows a peak power density close to that of benchmark Pt/C catalyst.     

融合矩阵分解和代价敏感的微生物数据扩增算法

微生物会对人类健康产生直接影响,对相关数据的分析有助于疾病诊断。然而,采集到的数据存在类不平衡与高稀疏性两个问题。现有的过采样方法在一定程度上可缓解数据的类不平衡,但是难以应对微生物数据的高稀疏性。本文提出了一种融合矩阵分解和代价敏感的数据扩增算法,其包含3个技术。首先,将原始矩阵分解为样本子空间和特征子空间;其次,利用样本子空间的正向量及其近邻向量生成合成向量;最后,根据合成向量与所有负向量的距离对其过滤。实验在8个微生物数据集上进行,同时与5种过采样算法对比,结果表明本文所提算法能够增强正样本的多样性,在识别出更多正样本的同时,分类结果的代价更低。     

龙岩市新罗区小流域水土保持综合效益指标定量评价方法

由于目前的水土保持效益评价方法对于不同区域的适宜性有待提高,研究新罗区小流域水土保持综合效益指标定量评价方法。构建评价指标体系,确定项目区域内的16个评价指标。通过水土保持指标权重的确定,获得判断矩阵。定量化评价指标,并建立模糊数学隶属度函数对指标进行标准化处理。经综合效益得分值计算,完成综合效益的定量评价。经评价结果分析,新罗区小流域内的蓄水效益为248.97×104m2、保土效益共为3.64×104t,经济效益为1676.92万元,生态环境得到了有效地改善。拱桥溪综合效益得分为57.1、硿溪综合效益得分为42,坪坑溪综合效益得分为40.6,本研究的综合效益评价结果与实际情况符合,证明所提方法具有有效性。     

中央空调传感器双重降噪模糊故障检测方法

针对现有降噪方法存在噪声残留以及异常检测指标受噪声影响较大的问题,提出中央空调传感器双重降噪和模糊指标 的故障检测方法。 自适应噪声的完整经验模态分解(complete EEMD with adaptive noise,CEEMDAN)所具有的噪声残余等问题, 用局部均值估计提取 k 阶模态替换模态估计完成初次降噪;而早期出现的虚假模式,先通过相关系数准则筛选含噪分量尽可能 保留有效信息,然后计算奇异值差分谱确定降噪阶次进行奇异值分解(singular value decomposition,SVD)完成二次降噪。 最后, 结合能量和峭度系数提出模糊指标作为异常信号控制限进行故障检测。 采用中央空调实验系统运行数据对所提方法进行验 证,结果表明,该方法具有良好的降噪及敏感特征筛选能力,信噪比提升 20. 203 7 dB,均方误差平均减小 48. 75%,故障检测准 确率平均提升 8. 67%,响应速度提升 33. 3%,抗噪性及检测效果提升明显。     

考虑频率与区间联络线功率安全约束的两区互联电力系统机组组合

随着电源结构与电网形态的转变,互联电力系统频率时空分布特征日益显著,区域频率差异与区间联络线功率振荡增大,基于统一频率假设的频率安全约束机组组合方法不再适用。针对考虑频率时空分布特征的两区互联电力系统安全约束机组组合,推导区域频率与区间联络线功率闭式解,并基于闭式解的两项划分,推得区域频率最低点、最大变化率、准稳态值以及区间联络线功率振荡峰值、准稳态值等一系列解析安全量化指标。基于所得指标,构建考虑区域频率与区间联络线功率安全约束的机组组合模型。并根据调度模式与指标特点,提出兼顾区域能力保障与区间能力协调的两级两阶段迭代求解算法。结果表明,所得指标可准确描述两区互联电力系统的安全特征,所提模型和算法可有效保障两区互联电力系统机组组合方案的运行安全。     

SnO_2/MWCNTs复合改性阳极对海底沉积物微生物燃料电池电化学性能的影响

采用电沉积法和浸渍法制备了氧化锡/多壁碳纳米管(SnO_2/MWCNTs)复合材料,并首次将其应用在海底沉积物微生物燃料电池(MSMFCs)的阳极改性,测试分析SnO_2/MWCNTs改性阳极的电化学性能和由其组成的电池性能。结果表明,SnO_2/MWCNTs复合阳极的氧化还原电化学活性和电子转移动力学活性分别是空白组的28.26倍和983.7倍;电容性能是空白组的43.14倍;阳极电荷转移电阻约是空白组的1/4。复合改性阳极组MSMFCs的最大功率密度(1 085.1 m W/m2)是空白组的2.17倍。机理分析表明,MWCNTs提高了阳极的导电性,SnO_2使氧化还原反应更容易进行,阳极的电容性能增加;在特殊的海洋弱碱条件下,SnO_2和MWCNTs的增强协同作用使复合改性阳极表现出更加优异的性能。     

冷等离子体处理对生鲜鸡胸肉杀菌效果及品质影响

目的 研究沿面介质阻挡放电(Surface Dielectric Barrier Discharge,SDBD)等离子体对生鲜鸡胸肉的杀菌作用及品质影响。方法 采用放电功率为260 W的SDBD等离子体分别处理生鲜鸡胸肉2 min和4 min,并于4 ℃贮藏12 d。每隔3 d取样,测定菌落总数、色泽、pH、汁液流失率、硫代巴比妥酸反应物(Thiobarbituric Acid Reactive Substances,TBARS)含量、挥发性盐基氮(Total Volatile Basic Nitrogen,TVB-N)含量及质构特性。结果 经SDBD等离子体处理2 min或4 min,并于4 ℃贮藏12 d后,生鲜鸡胸肉的菌落总数分别为7.16 lg(CFU/g)和6.70 lg(CFU/g),均低于对照组样品的菌落总数(7.55 lg(CFU/g))。此外,SDBD等离子体处理能够显著(P<0.05)改善冷藏期间鸡胸肉的品质参数,如pH、色泽(L^*、a^*和b^*)、汁液流失率、TVB–N含量和质构特性(硬度、弹性、咀嚼性等),但对脂质氧化具有促进作用。结论 SDBD等离子体对生鲜鸡胸肉具有良好的杀菌效果,并有效保持了其品质,在鸡胸肉保鲜上具有巨大的应用前景。     

Chemiotropic behavior of female olive fly (Bactrocera oleae GMEL.) onOlea europaea L

An interpretation is given of a number of observations on the chemiotropic behavior ofBactrocera oleae in connection with olive maceration water and the fly's return to the olive groves after the first summer rains. To this end, the headspace of both maceration water and leaf leaching water, simulating rainfall, were examined. In both cases, the presence of ammonia, which is generally known to attract fruit flies (Diptera, Tephritidae), was detected and, for the first time, in addition to other compounds that are inert for the fly, the presence of styrene was also detected. This aromatic hydrocarbon was found to be a strong attractant. It is shown that both ammonia and styrene are products of the metabolism of microbial flora present on the olive and leaf surface.     

Ecological assessment of Phragmites australis wetlands using multi-season SPOT-5 scenes

Ecologists and conservationists need accurate and replicable tools for monitoring wetland conditions in order to develop and implement adaptive management strategies efficiently. The Rhone Delta (Camargue) in southern France encloses 9200 ha of fragmented reed marshes actively managed for reed harvesting, waterfowl hunting or cattle grazing, and holding significant numbers of vulnerable European birds. We used multi-season SPOT-5 data in conjunction with ground survey to assess the predictive power of satellite imagery in modelling indicators of reed structure (height, diameter, density and cover of green/dry stems) relevant to ecosystem management and bird ecology. All indicators could be predicted accurately with a combination of bands (SWIR, NIR) and indices (SAVI, OSAVI, NDWI, DVI, DVW, MSI) issued from scenes of March, June, July, September or December and subtraction between these. All models were robust when validated with an independent set of satellite and field data. The high spatial resolution of SPOT-5 scenes (pixel of 10 × 10 m) permits the monitoring of detailed attributes characterizing the reed ecosystem across a large spatial extent, providing a scientifically-based, replicable tool for managers, stakeholders and decision-makers to follow wetland conditions in the short and long-term. Combined with models on the ecological requirements of vulnerable bird species, these tools can provide maps of potential species ranges at spatial extents that are relevant to ecosystem functioning and bird populations.     

短波地空通信站址布局评估方法

针对短波地空通信站址布局的评估问题,给出2个评估站址布局方案的指标——覆盖度和覆盖效率,分别运用网格扫描法和蒙特卡罗方法对这2个指标进行确定。通过仿真,对正方形和正六边形2种特殊站址布局结构进行评估和比较,得出正六边形结构更合理的结论,并验证了这2个评估指标和确定方法的可行性和有效性。