Podded propulsors are widely used in warships and cruise ships, which have a higher requirement of vibrational and acoustic design. Therefore, studying vibration characteristics and the transmission mechanism of podded propulsor shafting is significant for reducing vibration and ensuring the safe operation of ships. This paper establishes a model of podded propulsor shafting by analytical method. The shafting is simplified to a heterogeneous variable cross-section beam, while bearings are seen as springs. The podded propulsor shafting has one radial-thrust hybrid bearing and one radial bearing. The excitations from the propeller and cabin are considered. The influences of bearing stiffness, bearing location, and excitation on vibration characteristics of shafting are analyzed. The main conclusions are as follows: Based on the analysis of the area that resonance frequency is sensitive to the change of bearing stiffness, the resonance frequencies of the shafting can be adjusted to the proper range. The large span between hybrid bearing and radial bearing leads to low stiffness of shafting and low resonances frequencies. Under radial excitations, the low vibration always occurs at the hybrid bearing, motor shafting, or propeller end of shafting. This research provides theoretical support for the design and optimization of vibration reduction of podded propulsor shafting.
With the advent of the era of globalization and the rise of the wave of the information revolution, international public opinion and national image have become necessary considerations for a country to realize its national interests in the international community. The outbreak of the global epidemic in the past two years has pushed China to the center of public opinion again, threatening China's national image. This once again reminds us that we should use public diplomacy to carry out the long-term strategic task of building an excellent national image. My country has used national image propaganda films to shape the image of a peaceful, open, and friendly big country. Some of these experiences are worth learning from, and some problems are worth reflecting on and discussing. Taking the Chinese national image propaganda films "Character" and "Angle" as examples, combined with Lasswell's 5W theory, this paper discusses the advantages and difficulties of using national image propaganda films to shape national image in China's public diplomacy. We provide some constructive solutions to the difficulties and problems encountered by our predecessors, look to the future, and look forward to the development direction of shaping China's national image.
A newly excavated ritual site, Xuechi, exposed abundant sacrificial livestock, allowing to understand the supplies and managements of livestock during the early Chinese Qin-Han Empires. Here we reported animal enamel 87Sr/86Sr values from the Xuechi site that are obviously higher than those of local snails and surface water, as well as calcites of the Chinese Loess Plateau (CLP) where the site was located, strongly suggesting that these sacrificial animals were not raised in the vicinity of the site. The regional bioavailable 87Sr/86Sr isoscape further indicates that some livestock were probably derived more than one hundred kilometers away, suggesting a complex social network for recruiting and managing the sacrificial activities. In the context of other Neolithic-Bronze Age records on the CLP, an increasing trend in variation of faunal 87Sr/86Sr values shows a robust correlation to Chinese states’ trajectory, in concordance with the territorial expansion model for state formation.
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