Governance choices and policy outcomes in the Latin American and caribbean electricity sector

The paper first provides, for Latin America and the Caribbean, country-specific synthetic quantitative measures of the degree of adoption of governance reforms in the electricity sector, focusing on four key dimensions (market structure, private sector participation (PSP), regulatory autonomy and operational organization). These measures are then correlated with standard policy performance outcomes measures. The findings suggest that, the reforms, considered jointly, were statistically significantly associated with higher technical and process quality but not with social or service improvements. Considered individually, increased regulatory autonomy enjoyed the highest positive correlation with desirable outcomes, but PSP has no significant correlation with any of the outcomes. In sum, as of 2018, governance reforms, considered jointly, had still not delivered on some promised payoffs, notably in addressing energy poverty, although the sensitivity analysis suggests that, for some indicators, the relationships are stronger for larger than for smaller countries.     

Study of the surfactant role in latex–aerogel systems by scanning transmission electron microscopy on aqueous suspensions

For insulation applications, boards thinner than 2 cm are under design with specific thermal conductivities lower than 15 mW m^?1 K^?1. This requires binding slightly hydrophobic aerogels which are highly nanoporous granular materials. To reach this step and ensure insulation board durability at the building scale, it is compulsory to design, characterise and analyse the microstructure at the nanoscale. It is indeed necessary to understand how the solid material is formed from a liquid suspension. This issue is addressed in this paper through wet‐STEM experiments carried out in an Environmental Scanning Electron Microscope (ESEM). Latex–surfactant binary blends and latex–surfactant–aerogel ternary systems are studied, with two different surfactants of very different chemical structures. Image analysis is used to distinguish the different components and get quantitative morphological parameters which describe the sample architecture. The evolution of such morphological parameters during water evaporation permits a good understanding of the role of the surfactant.     

Research on heat dissipation performance and flow characteristics of air‐cooled battery pack

With the depletion of fossil fuels and the aggravation of environmental pollution, the research and development speed of electric vehicles has been accelerating, and the thermal management of battery pack has become increasingly important. This paper selects the electric vehicle battery pack with natural air cooling as the study subject, conducts simulation analysis of the heat dissipation performance of battery packs with and without vents. Then this paper researches on the influence of internal flow field and external flow field. Field synergy principle is used to analyze the effect of velocity field and temperature field amplitude. The results show the following: it is found that the maximum temperature rise and the internal maximum temperature difference of the battery pack with vents are reduced by about 23.1% and 19.9%, raising speed value can improve the heat dissipation performance, and raising temperature value can decrease the heat dissipation performance. Reasonable design of the vents can make the inner and outer flow field work synergistically to achieve the best cooling effect. Then the reference basis for the air cooling heat dissipation performance analysis of electric vehicle, battery pack structure arrangement, and air‐inlet and air‐outlet pattern choosing are offered.     

Probabilistic seismic damage assessment of reinforced concrete buildings considering directionality effects

Most of buildings and structures are usually projected according to two main axes. However, the geographical position of these buildings varies randomly. Such random distributions of the azimuthal positions of structures, in most of the cities, generally, are not accounted for when assessing their seismic risk; certainly, the direction of the seismic loads is another highly random variable. Moreover, an additional important source of uncertainty is related to the structural response, mainly due to the random character of the mechanical properties. There is a consensus that uncertainties must be considered for adequately assessing the seismic risk of structures, but these directionality effects have not been deeply explored so far. In this article, the influence of the high uncertainty involved in these input variables on the expected seismic damage is analysed. Thus, an actual earthquake, which affected the southern part of Spain, is studied. Notably, damages on a group of affected buildings, located close to the epicentre, are analysed and discussed in detail. The results show that the influence of the random azimuthal position of structures is an important source of uncertainty and that it should be taken into account when estimating the expected seismic risk in urban areas.     

Sensitivity analysis of Johnson-Cook material parameters on adiabatic shear in different directions

ABSTRACT

This study investigates the effects of strain, strain rates, and forming directions (RD-rolling direction, TD-transverse direction, and ND-normal direction) on adiabatic shear, via dynamic impact compression tests using the Split Hopkinson Pressure Bar (SHPB) apparatus. A modified Johnson-Cook (J-C) constitutive model is proposed, which used to analyse the influence of the constitutive parameters on the sensitivity of adiabatic shear, employing a finite element software. The different sensitivities of adiabatic shear under different directions are explained by combining microscopic analysis and results from mechanical responses. The results show that the sensitivity of adiabatic shear can be related to the time of stress collapse in the following trend: ND?>?TD?>?RD; the sensitivities of these constitutive parameters on adiabatic shear are calculated and compared.     

Laplacian regularized robust principal component analysis for process monitoring

Principal component analysis (PCA) is one of the most widely used techniques for process monitoring. However, it is highly sensitive to sparse errors because of the assumption that data only contains an underlying low-rank structure. To improve classical PCA in this regard, a novel Laplacian regularized robust principal component analysis (LRPCA) framework is proposed, where the “robust” comes from the introduction of a sparse term. By taking advantage of the hypergraph Laplacian, LRPCA not only can represent the global low-dimensional structures, but also capture the intrinsic non-linear geometric information. An efficient alternating direction method of multipliers is designed with convergence guarantee. The resulting subproblems either have closed-form solutions or can be solved by fast solvers. Numerical experiments, including a simulation example and the Tennessee Eastman process, are conducted to illustrate the improved process monitoring performance of the proposed LRPCA.     

风洞模型加速度负反馈振动主动控制方法研究

针对尾撑式风洞模型强方向性振动问题,基于异位配置加速度负反馈控制器对风洞模型振动主动控制方法进行研究。首先,通过模态分析得到系统低阶模态振动的强方向性并基于系统特性设计了具有结构耦合性的内嵌压电陶瓷作动器的风洞模型振动主动控制系统。然后,基于异位配置NAF控制器分别设计了针对第二阶模态和前两阶模态的单模态NAF控制算法和双模态NAF控制算法。最后,进行了实验验证,结果表明:双模态NAF控制算法控制效果较好,前两阶模态阻尼比分别提高近13倍和近40倍,镇定时间分别缩短近11s和近26s。     

Data envelopment analysis based on team reasoning

Existing approaches to data envelopment analysis focus mainly on the derivation of the efficiency of the individual decision‐making unit (DMU) or on the calculation of the weights of multiple inputs or outputs, but pay little attention to the team interest of all the DMUs. Motivated by the idea of team reasoning, in which the benefit of the team is of higher importance than that of each individual, this paper considers all the DMUs as a team and introduces the team indexes including the overall efficiencies, variance, boundaries of all the DMUs, and relationships between DMUs. Several models are first developed to estimate values of the team indexes based on which decision makers can provide their preferences regarding them. Then, models are established to obtain the interval efficiencies of individual DMUs under the condition that the team indexes are satisfied. Several examples are given to illustrate the proposed approaches and verify their applicability.     

双盘式磁力耦合器振动噪声分析与实验研究

为了在双盘式磁力耦合器设计阶段分析振动噪声特性,优化双盘式磁力耦合器设计,提出了一种利用模态叠加原理来分析其振动噪声的方法。双盘式磁力耦合器具有高转矩密度与高效率等优势,因此逐渐发展成为煤矿机械柔性传动装置。由于双盘式磁力耦合内部的转子磁场非正弦分布以及涡电流谐波等因素影响,双盘式磁力耦合器输出转矩中不可避免的存在波动。若根据计算得出的双盘式磁力耦合器的电磁振动噪声特点,在设计时选取振动噪声小的参数进行优化组合,可在实际中降低其电磁振动及噪声,有利于减少制造成本。本文结合双盘式磁力耦合器的结构特征,提出了一种模态叠加响应法计算电磁振动噪声,建立了其电磁径向力的解析模型,并在多物理场耦合作用下分析主要电磁径向力波在工作频率内的谐波响应,最后在额定功率为55 kW双盘式磁力耦合器实验台上进行试验验证。基于麦克斯韦张量法,建立了双盘式磁力耦合器的径向电磁力解析模型,并得出0阶与10阶电磁径向力波是产生振动噪声的最主要原因;利用多物理场耦合分析法进行谐波响应NVH特性分析,结果显示0阶力波的振动加速度与形变量均大于10阶力波的振动加速度与形变量,因此双盘式磁力耦合器的电磁振动主要来源于0阶力波;在额定功率为55 kW,最高转速为1 500 r/min的双盘式磁力耦合器实验台进行振动测试,试验结果显示在1 500 r/min时,试验得出的最大振动峰值及频率约为35 m/s^2和4 950 Hz,与有限元仿真结果的误差对应为6.3%和1.1%;而当变频电机的输入转速依次增大时,振动加速度的理论值、仿真值与试验值的曲线形态较为接近,误差较小;噪声估计值与实测值的最大误差仅为8.9%,基本验证了本文所提出模态叠加法的正确性。     

袋装水泥装车机及拨板机构的设计与研究

针对袋装水泥装车半自动化问题，设计一款全自动装车机。首先，根据袋装水泥车间生产状况，确定水泥装车方案，即采用抽屉式逐层装车原理，利用ＳｏｌｉｄＷｏｒｋｓ创建装车机三维模型；其次，为使水泥包快速准确地到达指定位置，针对拨板机构中的分拨板及导柱进行受力分析，建立其力学模型，推导出应力公式；最后，通过 ＡＮＳＹＳ有限元软件进行分拨板的力学仿真，为后续的优化设计提供依据。