平板壁面に衝突する燃料噴霧の液膜形成に及ぼす分割噴射の影響

内容の要約広島大学(Hiroshima University)博士(工学)Doctor of Engineeringdoctora

Behaviors of Multi-Droplets Impacting on a Flat Wall

Microscopic characteristics of fuel spray are very important for atomization and mixture formation. The droplet size, number density, velocity distribution as well as minimum distance reveal the quality of spray and atomization, which affects the subsequent combustion and emissions for different engines such as vehicle, marine and aircraft. Moreover, in the internal combustion engine, the spray-wall impingement is difficult to avoid, which is the main source for soot emissions. Nowadays, regulations for emissions become straight by governments. Therefore, it is urgent for us to alleviate the energy and emissions crisis. In this study, the droplets behaviors will be characterized under the related engine working state. Firstly, the experimental setup and measurement were explained in detail. Then, images process method was induced to calculate the droplet size, velocity and distance among them. Finally, results of the impinging spray were presented. One thing should be noted, as the dense region is not available to detect the droplets by the observation. Therefore, a spray “slicer” was designed and applied to cut the spray slim. Finally, multi-droplets were generated, and the results can be concluded as well. All the results could provide insights into the impacting behaviors for better understanding the droplet dynamics

Research on the Bearing Lifespan Prediction Method for Ship Propulsion Shaft Systems Based on an Enhanced Domain Adversarial Neural Network

To address the challenge of accurate lifespan prediction for bearings in different operating conditions within ship propulsion shaft systems, a two-stage prediction model based on an enhanced domain adversarial neural network (DANN) is proposed. Firstly, pre-training features containing comprehensive degradation information are extracted from the entire source domain dataset encompassing all operational conditions. Subsequently, DANN is employed to extract domain-invariant features that are difficult to distinguish. Following this, a feature alignment process is utilized to align high-dimensional features with pre-training features, thereby mitigating the adverse effects caused by missing data in the incomplete target operational condition dataset. Finally, the effectiveness of this approach is validated using operational data from bearings under multiple operating conditions. The experimental results demonstrate that the method presented in this paper achieves an average error reduction of 0.0626 and 0.0845 compared to the MK-MMD transfer learning method and self-attention ConvLSTM algorithms, respectively, and exhibits higher predictive reliability. This method can provide valuable insights for lifespan prediction challenges concerning bearings in ship propulsion shaft systems under various operational conditions, as well as similar cross-domain lifespan prediction problems

Guiclupea superstes, gen. et sp. nov., the youngest ellimmichthyiform (clupeomorph) fish to date from the Oligocene of South China

A new ellimmichthyiform, Guiclupea superstes, gen. et sp. nov., from the Oligocene Ningming Formation of Ningming Basin, Guangxi Zhuang Autonomous Region, South China is described herein. With relatively large body size, parietals meeting at the midline, anterior ceratohyal with a beryciform foramen in the center, a complete predorsal scutes series of very high number and about equally-size scutes with radiating ridges on dorsal surface, first preural centrum unfused with first uroneural but fused with the parhypural, and first ural centrum of roughly the same size as the preural centrum, Guiclupea superstes cannot be assigned to the order Clupeiformes. The phylogenetic analyses using parsimony and Bayesian inference methods with Chanos/Elops as outgroup respectively suggests that the new form is closer to ellimmichthyiform genus Diplomystus than to any other fishes, although there are some discrepancies between the two criteria and different outgroups used. It shares with Diplomystus the high supraoccipital crest, pelvic-fin insertion in advance of dorsal fin origin, and the number of predorsal scutes more than 20. The new form represents the youngest ellimmichthyiform fish record in the world. Its discovery indicates that the members of the Ellimmichthyiformes had a wider distribution range and a longer evolutional history than previously known

A One-Pot Hydrothermal Preparation of High Loading Ni/La₂O₃ Catalyst for Efficient Hydrogenation of Cinnamaldehyde

It is a challenging task for selective hydrogenation of cinnamaldehyde (CAL) to hydrocinnamaldehyde (HCAL) without additional by-product formation. In this work, a La2O3 supported high Ni content nanoparticle catalyst was prepared for CAL selective hydrogenation. Meanwhile, Co-La2O3 catalysts were used as a reference catalyst. XRD, TEM, STEM-HAADF, XPS, and H2-TPR measurements were used to investigate the physicochemical properties of Ni-La2O3 catalysts. The experimental results confirmed that the CAL conversion and HCAL selectivity were effectively promoted with the increase of Ni loading amounts. At a Ni/La molar ratio of four, a high HCAL selectivity of 87.4% was obtained at a CAL conversion of 88.1% under mild reaction conditions. The catalyst was recycled five times without activity loss. Combined with various characterizations, it could be inferred that the good hydrogen adsorption and dissociation capacity of Ni and the presence of a certain amount of oxygen vacancies on the La2O3 support have a positive effect on the improvement of HCAL selectivity. This work provided an effective path to design transition-metal-based supported oxide catalyst for the cinnamaldehyde hydrogenation to hydrocinnamaldehyde

A New Saurichthyiform (Actinopterygii) with a Crushing Feeding Mechanism from the Middle Triassic of Guizhou (China)

<div><p>Background</p><p>Equipped with an effective predatory feeding mechanism enhanced by large and sharp teeth, pointed snout and elongate body, saurichthyiform fishes are considered common fish-eaters in the early Mesozoic aquatic ecosystems. Additionally, because of the similar body plan across species, saurichthyiforms are also regarded evolutionally conservative, with few morphological and ecological changes during their long history. However, their phylogenetic affinity remains unclear as to whether they are chondrostean, neopterygian or stem-actinopteran, and likewise the intrarelationships of the group have rarely been explored.</p><p>Methodology/Principal Findings</p><p>Here we report a new saurichthyiform from the Middle Triassic of Guizhou, China, based on the well-preserved specimens including a 3-D braincase. The new taxon, <i>Yelangichthys macrocephalus</i> gen. et sp. nov., is unique among saurichthyiforms in having a peculiar neurocranium with a broad orbital tectum, paired posterior myodomes, a deep, transverse fossa in the posterodorsal part of the orbit, and a feeding mechanism structured for durophagy. Phylogenetic analysis places <i>Yelangichthys</i> gen. nov. at the most basal position in the Saurichthyiformes as the sister to Saurichthyidae, and a new family Yelangichthyidae is erected to include only <i>Y. macrocephalus</i> gen. et sp. nov. The monophyly of the Chondrostei comprising [Saurichthyiformes + Acipenseriformes] Birgeriiformes is supported, but not the monophyly of <i>Saurichthys</i>, the type genus of Saurichthyidae. With its outstanding osteological details, <i>Yelangichthys</i> gen. nov. greatly increases the neurocranial variations in saurichthyiforms, and its novel feeding structure suggests the consumption of hard-preys instead of fishes.</p><p>Conclusions/Significance</p><p>Our findings highlight the detailed osteology of a saurichthyiform braincase and its feeding design. We suggest that saurichthyiforms are closely allied to the Acipenseriformes. Saurichthyiforms were very diverse in the cranial osteology and they might have undergone a rapid evolutionary radiation via, for the new material here, transforming the feeding mechanism and thus exploiting the food resources unsuitable for other saurichthyiforms.</p></div

Similarity and normalization study of fuel spray and combustion under ultra-high injection pressure and micro-hole diameter conditions–spray characteristics

The compression-ignition engine has been widely applied in various fields due to its high efficiency, fuel economy, and adaptability. With the increasing awareness of environmental issues, emission regulations have become more stringent, leading to a growing demand for high-pressure and small-sized engines. Since developing new engines is often both costly and time-consuming, leveraging the similarity between spray and combustion processes for new engine development can significantly reduce the required resources and time. However, to date, systematic research on the similarity and normalization of sprays and combustion processes, especially under ultra-high injection pressure and micro-hole diameter conditions, remains lacking. In this study, conversion models and normalization models for spray characteristics were developed based on both time scale and multi-dimensional space scale. The spray transformation and normalization were verified for different aperture sizes, injection pressures, ambient temperatures, densities, and pressures. The results show that the models exhibit good interchangeability and normalization effects. This research outcome will provide valuable references for optimizing and designing more efficient and environmentally friendly internal combustion engines