柔性直流系统短路故障网络阻抗建模与时频特性诊断方法研究

针对柔性直流系统直流侧短路故障诊断难题,文章从故障网络精确建模和暂态特征信号分析两个方面展开研究,并提出了阻抗网络暂态响应时频特性关联度的故障诊断方法。该方法通过向柔性直流系统线路入口处注入脉冲电压作为激励,实时提取所产生的暂态电流分量,经不同尺度的Mexican Hat变换得到时频能量序列,并构造反映故障网络暂态响应时频能量谱矩阵。同时,建立柔性直流系统精确模型,模拟不同故障点经不同大小电阻的短路故障,构建完整故障样本及其时频特征库,经相似度计算可选出与实测故障特征最相近的样本,确定故障点位置和估计短路电阻大小。最后,对上述原理方法进行算例分析,并与时域方法比较,结果表明文章所述诊断方法及其判据更为准确有效,相关原理正确可行。     

Pricing and inventory carryover strategy considering cost learning effect and strategic consumers

Anticipating the markdown in the future price due to the cost reduction of the firm, more and more consumers tend to delay their purchasing to the later period. Incorporating the strategic behavior of consumers, this paper establishes a two-period production and selling model under dynamic pricing strategy and price commitment strategy respectively, with considering stochastic learning effect in which the firm may or may not have the inventory carryover option. The results show that the firm may hold inventory under dynamic pricing while no inventory is kept under price commitment. Additionally, consumers' patience level enhances the benefit of inventory carryover. Furthermore, for the firm with relatively high farsighted level and low inventory holding cost, the dynamic pricing equipped with inventory carryover outperforms the price commitment strategy. Finally, numerical examples are conducted to analyze the impacts of important parameters on the firm's choice of pricing strategies.     

Danish milk consumers are critical of advanced breeding methods in dairy production,but only 1 in 5 is unwilling to drink milk from dairy cows bred with semen derived from such methods

Assisted reproductive technologies and genetic technologies can accelerate progress in breeding programs in dairy farming, but it is unclear how consumers will react to the use of these technologies. Using representative questionnaire data on Danish citizens (n = 2,036) this cross-sectional study examined consumer attitudes to the application of advanced technologies in dairy cattle breeding. Attitudes were examined in 2 ways. First, we prompted about general attitudes to assisted reproductive technologies and genetic technologies in dairy cow breeding. Here we found that most of the participants were critical of cow impregnation involving hormone therapy and the insertion of cloned fetuses. Second, we used a vignette experiment to study whether acceptance of and willingness to drink milk varies with the type of technique that farmers use for their breeding work, as well as the traits being bred for. We included 5 breeding methods with differing degrees of technological complexity. Participants were randomly assigned to receive tailored information about 1 of the 5 breeding methods. The information specified that dairy farmers' own use of advanced technologies is limited to using semen in artificial insemination on the farm. The potentially concerning technologies are here not applied at farm level but are represented in the semen used in artificial insemination because they were used by breeders on earlier generations of cows and bulls to develop semen with higher genetic merit. There was much less concern about this indirect use of the technologies. Only 1 in 5 participants thought the most advanced method we prompted about (use of semen from breeding methods involving genetic engineering and cloning) was unacceptable. Unwillingness to drink milk from cows produced through such a breeding method was also modest (18%) and not much higher than the unwillingness to drink milk from a cow produced by natural fertilization (10%). A likely reason for the unexpectedly low level of unwillingness to drink milk is that people regard the genetic engineering as distant from the final product. We also found that high-frequency organic milk consumers were more critical of advanced breeding methods. Thus, 28% within this group were unwilling to drink milk from cows impregnated with semen derived from earlier generations of cows and bulls bred using gene editing and cloning. Further, this share rose if the high-frequency organic consumers were very averse to the manipulation of nature. The organic sector may need to cater to this subgroup (e.g., by ensuring the traceability of the semen that organic farmers use to artificially inseminate their cows).     

Occurrence of enteric viruses and faecal indicators in submarine groundwater discharges in the coastal environment of the Mexican Caribbean

The occurrence of faecal microorganisms such as total coliforms (TCs), Escherichia coli (E. coli), coliphages (somatic and F+ specific) and the genomes of faecal viruses: human adenovirus (HAdV), norovirus (NoV) genogroup I (GI) and II (GII), enterovirus (EV), aichi virus (AiV) and Pepper mild mottle virus (PMMoV), was explored in submarine groundwater discharges (SGDs) in the Mexican Caribbean. Ultra-filtrated water samples were subjected to nucleic acid extraction and real-time quantitative polymerase chain reaction (PCR). Results showed the presence of TC bacteria at all sites, whereas the detection of E. coli occurred only during the dry season. Coliphages occurred during the rainy and dry seasons, with concentrations ranging from 10 to 2560 plaque forming units (PFU/100 ml). HAdV and AiV were detected in 50% and 41% of the samples, at concentrations ranging from 10² to 10⁴ genome copies per litre (GC/L) and from 10² to 10⁶ GC/L, respectively. NoV GI and II were detected in 25% and 16% of the samples, at concentrations of 10¹ GC/L and 10²–10³ GC/L, respectively. PMMoV was detected in 50% of the samples at concentrations ranging from 10¹ to 10³ GC/L. The EV genomes were not detected. These findings demonstrate that faecal microorganisms can be transported through SGDs in the Mexican Caribbean, potentially contributing to human health risks for recreation.     

Marginalising household users in smart grids

Unless just and inclusive, transitions to low carbon-energy systems are unlikely to receive sufficient legitimacy and broad public support. While research on inequalities and injustices in energy transitions is growing, these issues remain less explored in the case of the digitalisation of the energy systems through smart grids and smart homes. This paper aims to synthetise our understandings of inequality, exclusion and vulnerability in energy transitions by systemically analysing different dimensions of marginalisation in the transition to a digitalised electricity infrastructure in Sweden. To synthetise understandings of marginalisation and exclusion, conceptualisations of these processes in different social science approaches to energy studies are reviewed. Moreover, an empirical analysis of interviews with a range of Swedish actors such as energy utilities, social housing developers or pensioner organisations is carried out and enriched by previous research on smart grid users. The empirical analysis demonstrates what specific forms that diverse categories of marginalisation, as already identified generally in different social science approaches to energy studies, may take in smart grids. We argue that marginalisation of household users in smart grids may take place along multiple dimensions, relating to matters of literacy, participation, infrastructure, and the economy. The analysis suggests that bundles of marginalisation aspects concerning household users in sustainable energy transitions should be recognised and addressed simultaneously.