Is floating photovoltaic better than conventional photovoltaic? Assessing environmental impacts

Photovoltaic (PV) solar energy installations are growing all over the world as a promising renewable alternative to generate electricity. However, many studies have highlighted some drawbacks associated with the installation and operation of conventional solar energy power plants. Thus, floating photovoltaic (FPV) systems have been emerging as a new concept in solar energy to lessen negative environmental impacts caused by allocation of conventional PV facilities. This paper is an overview of the potential negative and positive environmental impacts caused by photovoltaic systems with particular interest on large-scale conventional and floating photovoltaic. This study addresses and compares the impacts at all phases of project implementation, which covers planning, construction, and operation and decommissioning, focusing on ambient located in the tropics. The overall impacts associated with project allocation such as deforestation (for the project implementation and site accessing), bird mortality, erosion, runoff, and change in microclimate are expected to have higher magnitudes for the implementation of conventional PV facilities. The results highlight advantages of FPV over conventional PV during the operational and decommissioning phases as well. Though, further studies are required to assess both qualitative and quantitative aspects of installations in similar areas.     

Electrochemical Behavior of Single CuO Nanoparticles: Implications for the Assessment of their Environmental Fate

The electrochemical behavior of copper oxide nanoparticles is investigated at both the single particle and at the ensemble level in neutral aqueous solutions through the electrode‐particle collision method and cyclic voltammetry, respectively. The influence of Cl^? and NO₃^? anions on the electrochemical processes occurring at the nanoparticles is further evaluated. The electroactivity of CuO nanoparticles is found to differ between the two types of experiments. At the single‐particle scale, the reduction of the CuO nanoparticles proceeds to a higher extent in the presence of chloride ion than of nitrate ion containing solutions. However, at the multiparticle scale the CuO reduction proceeds to the same extent regardless of the type of anions present in solution. The implications for assessing realistically the environmental fate and therefore the toxicity of metal‐based nanoparticles in general, and copper‐based nanoparticles in particular, are discussed.     

Mechanical and thermal properties of RE4Hf3O12 (RE=Ho,Er, Tm) ceramics with defect fluorite structure

The thermal and environmental barrier coatings (T/EBC) are technologically important for advanced propulsion engine system. In this study, RE₄Hf₃O₁₂ (RE=Ho, Er, Tm) with defect fluorite structure was investigated for potential use as top TBC layer. Dense pellets were fabricated via a hot pressing method and the mechanical and thermal properties were characterized. RE₄Hf₃O₁₂ (RE=Ho, Er, Tm) possessed a high Vickers hardness of 11 GPa. The material retained high elastic modulus at elevated temperatures up to 1773 K, which made it attractive for high temperature application. The coefficient of thermal expansion (CTE) of RE₄Hf₃O₁₂ (RE = Ho, Er, Tm) laid in the range between 7 × 10⁻⁶ K⁻¹ to 10 × 10⁻⁶ K⁻¹ from 473 K to 1673 K. In addition, the rare earth hafnates exhibited lower thermal conductivity which rendered it a good candidate material for thermal barrier applications.     

Wrapping effect of secondary phases on the grains: increased corrosion resistance of Mg–Al alloys

The discrete secondary phases usually cause severe galvanic corrosion, thereby resulting in rapid degradation for Mg–Al alloys in orthopaedics application. In this study, CaO was introduced into Mg–Al–Zn (AZ61) alloy via selective laser melting (SLM) to ameliorate the characterisations of the secondary phases, with an aim to improve its corrosion behaviour. Results revealed that CaO reacted with Mg and Al in Mg–Al alloys during SLM, suppressing the formation of coarse Mg₁₇Al₁₂ phase and promoting the formation of (Mg, Al)₂Ca phase. Meanwhile, the rapid solidification during SLM promoted the homogeneous precipitation of the second phase. As a result, inert (Mg, Al)₂Ca phase homogeneously wrapped the Mg grains, which effectively protected them from the invasion of corrosion solution. Thus, the degradation rate was remarkably reduced from 0.073 to 0.031?mg?cm^–2?h^–1. Furthermore, AZ61-9CaO exhibited good cytocompatibility. This work suggested that AZ61-9CaO was promising candidates for orthopaedics implants.     

不完全观测数据下混合效应模型的正交投影估计

基于矩阵的QR分解技术,对一类含有不完全观测数据的线性混合效应模型提出了一种基于正交投影的估计方法。在一些正则条件下,证明了固定效应参数的估计渐近服从标准正态分布,得到了固定效应参数的置信区间。另外,所提出的固定效应参数的估计过程不受随机效应的任何影响,具有较好的有效性和稳健性。最后,通过一些数值模拟和一个实例分析研究了所提出估计方法的有限样本性质。     

Vibration data-driven machine learning architecture for structural health monitoring of steel frame structures

A vibration data-based machine learning architecture is designed for structural health monitoring (SHM) of a steel plane frame structure. This architecture uses a Bag-of-Features algorithm that extracts the speeded-up robust features (SURF) from the time-frequency scalogram images of the registered vibration data. The discriminative image features are then quantised to a visual vocabulary using K-means clustering. Finally, a support vector machine (SVM) is trained to distinguish the undamaged and multiple damage cases of the frame structure based on the discriminative features. The potential of the machine learning architecture is tested for an unseen dataset that was not used in training as well as with some datasets from entirely new damages close to existing (i.e., trained) damage classes. The results are then compared with those obtained using three other combinations of features and learning algorithms—(i) histogram of oriented gradients (HOG) feature with SVM, (ii) SURF feature with k-nearest neighbours (KNN) and (iii) HOG feature with KNN. In order to examine the robustness of the approach, the study is further extended by considering environmental variabilities along with the localisation and quantification of damage. The experimental results show that the machine learning architecture can effectively classify the undamaged and different joint damage classes with high testing accuracy that indicates its SHM potential for such frame structures.     

Studies on microbridges of superconducting YBCO thin film

Critical current densities of the superconducting Y-Ba-Cu-O (YBCO) films have been observed to decrease with the increase of power of microwave radiation. Presence of Josephson type of junctions in the microbridges has been established from the microwave irradiation and magnetic field studies. BCS energy gap parameter (2/kT _c ) has been calculated from thedI/dV characteristics and found to be 3.7 at 13 K.     

矿井作业区域环境安全评价系统的设计与实现

分析了现有煤矿安全监控系统的状况,在安全监测的基础上建立了作业区域危险程度分级判定的评价模型,设计了一个矿井作业区域环境安全评价系统,详细介绍了该系统的设计思想、系统结构原理及主要功能。该系统可对煤矿井下主要作业区域生产安全的环境参数的变化进行动态分析和综合评价,并以不同的颜色给出该作业区域的危险等级,为保证井下作业人员的环境安全提供参考依据。该评价系统可独立运行,也可作为安全监控系统的功能组件运行。     

Modified criterion for global asymptotic stability of fixed-point state-space digital filters using two’s complement arithmetic

A criterion for the global asymptotic stability of fixed-point state-space digital filters using two’s complement arithmetic is presented. The criterion is a modified form of a well-known criterion due to Mills, Mullis, and Roberts. The criterion is in the form of linear matrix inequality and, hence, computationally tractable. An example shows the effectiveness of the modified criterion.     

营造和谐空间——浅析环境景观中公共设施的无障碍设计

环境景观中公共设施无障碍设计的目的是为了充分满足老年人、儿童以及残疾人群体在使用环境景观中公共设施的需求。在环境景观中合理设置无障碍的公共设施,是现代城市兼顾实用功能与审美功能的人性化体现。文章从环境景观中公共设施无障碍设计的现状来分析公共设施无障碍设计的思考方向。