Research on sound radiation characteristics of the high-speed train wheel

Taking the standard wheel model as an example, the radiation noise of a single wheel under excitation force which is computed by multi-body dynamics model is computed by acoustic boundary element method (BEM). Then, the damped wheel is proposed, and the sound radiation characteristics of both wheels are analyzed and compared. The results show that sound field of a single wheel presents an obvious directivity with petaloid change and continuous decrease, and the wheel tread and web contribute the most rolling noise. Compared with the standard wheel, the acoustic radiation power of the damped wheel decreased significantly, especially at the peak frequency. After that, the radiation noise generated by the wheel in the train is researched. The results show that the radiation noise generated by the wheel in the train is a complex sound field after the superposition and interference of multiple wheel noises, which are mainly in the bogies at both ends and its vicinity region. Meanwhile, the basic directivity characteristics of the petaloid change and continuous reduction are remained. The radiation noise which is generated by the wheel in the train has obvious peak characteristic, whose corresponding peak noises are below 110 dB. The radiation noise of the damped wheel is significantly smaller than that of the standard wheel at most frequency bands, and the total SPL at the observation point has decreased by 14.5 dB with obvious noise reduction effect. In order to further research the radiation noise of the damping wheel, influence factors on the noise reduction are analyzed. Finally, these parameters such as thickness and material should be considered comprehensively during designing the damping wheel, in order to find the optimal combination of all parameters

Distribution domains of the Pan-African event in East Antarctica and adjacent areas

The Pan-African event is widely distributed in East Antarctica (EA) craton, including both the coastal regions and interior of the EA. From aspects of the shear zones, granites, pegmatites, time of high-grade metamorphism and detrital zircon age peaks of the downflowing sediments from the inland, the Pan-African event in the EA and adjacent areas in the Gondwana reconstruction, like SE Africa, southern India and SW Australia, was described in the paper. The water or fluid available along the shear zones was responsible for retrogression of the earlier, e.g., Grenville age, high-grade outcrops to later Pan-African amphibolite to granulite facies metamorphism. In geochemistry, the granites are generally anorogenic, ocassionally with some gabbros or dolerite dykes, showing sign of bimodal feature. Meanwhile, the event has influenced most isotopic systems, including the U-Pb, Sm-Nd, Rb-Sr and Ar-Ar systems, giving Pan-African apparent ages. Spatially, the Pan-African event is demonstrated from possibly local granitic magmatism, to wider medium-high grade metamorphism, and mostly widespread in resetting for some isotope systems, suggesting the prevailing thermal effect of the event. Before Gondwana formation, local depressions in the EA may have been filled with sediments, implying the initial breakup period of the Rodinia. The later Pan-Gondwana counterrotating cogs shaped the interstitial fold belts between the continent blocks and formed a set of shear zones. The mafic underplating in the Gondwana may be responsible for the typical features of the Pan-African event. The event may be an overwhelmingly extensional and transcurrent tectonics in mechanism and is a possible response of the plate movement surrounding the continent swarms in the non-stable interior of the yet consolidated Gondwana

The evolution of floral deception in Epipactis veratrifolia (Orchidaceae): from indirect defense to pollination

BACKGROUND: It is estimated that floral deception has evolved in at least 7500 species of angiosperms, of which two thirds are orchids. Epipactis veratrifolia (Orchidaceae) is a model system of aphid mimicry as aphidophagous hoverflies lay eggs on false brood sites on their flowers. To understand the evolutionary ecology of floral deception, we investigated the pollination biology of E. veratrifolia across 10 populations in the Eastern Himalayas. We reconstructed the phylogeny of Epipactis and mapped the known pollination systems of previously studied species onto the tree. RESULTS: Some inflorescences of E. veratrifolia were so infested with aphids while they were still in bud that the some larvae of hoverflies developed to the third instar while flower buds opened. This indicated that adult female hoverflies were partly rewarded for oviposition. Although flowers failed to secrete nectar, they mimicked both alarm pheromones and aphid coloring of to attract female hoverflies as their exclusive pollinators. Phylogenetic mapping indicate that pollination by aphidophagous hoverflies is likely an ancestral condition in the genus Epipactis. We suggest that the biological interaction of aphid (prey), orchid (primary producer) and hoverfly (predator) may represent an intermediate stage between mutualism and deception in the evolution of pollination-by-deceit in E. veratrifolia. CONCLUSIONS: Our analyses indicate that this intermediate stage may be used as a model system to interpret the origin of oviposition (brood site) mimicry in Epipactis. We propose the hypothesis that some deceptive pollination systems evolved directly from earlier (partly) mutualistic systems that maintained the fidelity of the original pollinator(s) even though rewards (nectar/ brood site) were lost

N′-(2-Bromo-5-hy­droxy-4-meth­oxy­benzyl­idene)-3,5-dihy­droxy­benzo­hydrazide methanol monosolvate

In the crystal structure of the title compound, C15H13BrN2O5·CH3OH, the methanol solvent mol­ecule links symmetry-related mol­ecules through O—H⋯O and N—H⋯O hydrogen bonds. Further inter­molecular O—H⋯O hydrogen bonds link symmetry-related mol­ecules, leading to the formation of a three-dimensional network. Two of the H atoms involved in hydrogen bonding are disordered. The dihedral angle between the rings is 5.64 (14)°

Synergistic Influence of Local Climate Zones and Wind Speeds on the Urban Heat Island and Heat Waves in the Megacity of Beijing, China

Large-scale modifications to urban underlying surfaces owing to rapid urbanization have led to stronger urban heat island (UHI) effects and more frequent urban heat wave (HW) events. Based on observations of automatic weather stations in Beijing during the summers of 2014–2020, we studied the interaction between HW events and the UHI effect. Results showed that the UHI intensity (UHII) was significantly aggravated (by 0.55°C) during HW periods compared to non-heat wave (NHW) periods. Considering the strong impact of unfavorable weather conditions and altered land use on the urban thermal environment, we evaluated the modulation of HW events and the UHI effect by wind speed and local climatic zones (LCZs). Wind speeds in urban areas were weakened due to the obstruction of dense high-rise buildings, which favored the occurrence of HW events. In detail, 35 HW events occurred over the LCZ1 of a dense high-rise building area under low wind speed conditions, which was much higher than that in other LCZ types and under high wind speed conditions (< 30 HW events). The latent heat flux in rural areas has increased more due to the presence of sufficient water availability and more vegetation, while the increase in heat flux in urban areas is mainly in the form of sensible heat flux, resulting in stronger UHI effect during HW periods. Compared to NHW periods, lower boundary layer and wind speed in the HW events weakened the convective mixing of air, further expanding the temperature gap between urban and rural areas. Note that LCZP type with its high-density vegetation and water bodies in the urban park area generally exhibited, was found to have a mitigating effect on the UHI, whilst at the same time increasing the frequency and duration of HW events during HW periods. Synergies between HWs and the UHI amplify both the spatial and temporal coverage of high-temperature events, which in turn exposes urban residents to additional heat stress and seriously threatens their health. The findings have important implications for HWs and UHII forecasts, as well as for scientific guidance on decision-making to improve the thermal environment and to adjust the energy structure

6,6′-Dihydr­oxy-2,2′-[(pentane-1,5-diyl­dioxy)bis­(nitrilo­methyl­idyne)]diphenol

The mol­ecule of the title compound, C19H22N2O6, assumes a W-shaped configuration with the dihedral angle between the two halves of the mol­ecule being 82.48 (5)°. There is one half-mol­ecule in the asymmetric unit with a crystallographic twofold rotation axis passing through the central C atom of the five methylene groups in the [—CH=N—O—(CH2)5—O—N=CH—] bridge. The dihedral angle formed by the two benzene rings in each mol­ecule of the title compound is 84.18 (4)°. There are strong intra­molecular O—H⋯N and O—H⋯O hydrogen bonds and weak inter­molecular π–π stacking inter­actions between neighbouring benzene rings, and the inter­molecular plane-to-plane distances are 3.488 (2) and 3.841 (3) Å along the b and c axes, respectively. In the crystal structure, inter­molecular O—H⋯O hydrogen bonds link each mol­ecule to two others, forming an infinite three-dimensional supra­molecular structure

Research on sound radiation characteristics of the high-speed train wheel

Taking the standard wheel model as an example, the radiation noise of a single wheel under excitation force which is computed by multi-body dynamics model is computed by acoustic boundary element method (BEM). Then, the damped wheel is proposed, and the sound radiation characteristics of both wheels are analyzed and compared. The results show that sound field of a single wheel presents an obvious directivity with petaloid change and continuous decrease, and the wheel tread and web contribute the most rolling noise. Compared with the standard wheel, the acoustic radiation power of the damped wheel decreased significantly, especially at the peak frequency. After that, the radiation noise generated by the wheel in the train is researched. The results show that the radiation noise generated by the wheel in the train is a complex sound field after the superposition and interference of multiple wheel noises, which are mainly in the bogies at both ends and its vicinity region. Meanwhile, the basic directivity characteristics of the petaloid change and continuous reduction are remained. The radiation noise which is generated by the wheel in the train has obvious peak characteristic, whose corresponding peak noises are below 110 dB. The radiation noise of the damped wheel is significantly smaller than that of the standard wheel at most frequency bands, and the total SPL at the observation point has decreased by 14.5 dB with obvious noise reduction effect. In order to further research the radiation noise of the damping wheel, influence factors on the noise reduction are analyzed. Finally, these parameters such as thickness and material should be considered comprehensively during designing the damping wheel, in order to find the optimal combination of all parameters

Radiology-guided forceps biopsy and airway stenting in severe airway stenosis

PURPOSEWe aimed to determine the feasibility, safety, and effectiveness of radiology-guided forceps biopsy and airway stenting in patients with severe airway stenosis.MATERIALS AND METHODSThis study involved 28 patients with severe airway stenosis who underwent forceps biopsy between October 2006 and September 2011. Chest multislice computed tomography was used to determine the location and extent of stenosis. Sixteen patients had tracheal stenosis, two patients had stenosis of the tracheal carina, six patients had stenosis of the left main bronchus, and four patients had stenosis of the right main bronchus. Forceps biopsy and stenting of the stenosed area were performed under fluoroscopic guidance in digital subtraction angiography and the biopsy specimens were analyzed histopathologically. We contacted the patients via phone call and utilized a standardized questionnaire to determine their medical condition during a postoperative three-month follow-up.RESULTSThe technical success rate of radiology-guided forceps biopsy was 100%. Biopsy specimens were obtained in all patients. Dyspnea was relieved immediately after stent placement. No serious complications, such as tracheal hemorrhage or perforation, mediastinal emphysema, or asphyxia, occurred.CONCLUSIONRadiology-guided forceps biopsy and airway stenting can be used for the emergency treatment of severe airway stenosis. This method appears to be safe and effective, and it may be an alternative therapeutic option in patients who cannot tolerate fiberoptic bronchoscopy

Clean and modified substrates for direct detection of living cells by surface-enhanced Raman spectroscopy

Iodide adsorption and electrochemical negative potential desorption were proposed and compared to obtain clean SERS substrates. The two methods can effectively eliminate the interference of surface impurities in the SERS detection. SERS signals of membranes of living cells with a good reproducibility have been obtained.NSFC[20825313, 20827003, 21021120456]; 973 program[2007CB935603, 2009CB930703]; Fundamental Research Funds for the Central Universities[2010121019]; China Postdoctoral Science Foundatio

The topological differences between visitation and pollen transport networks: a comparison in species rich communities of the Himalaya–Hengduan Mountains

Pollination networks are usually constructed and assessed by direct field observations which commonly assume that all flower visitors are true pollinators. However, this assumption is often invalid and the use of data based on mere visitors to flowers may lead to a misunderstanding of intrinsic pollination networks. Here, using a large dataset by both sampling floral visitors and analyzing their pollen loads, we constructed 32 networks pairs (visitation versus pollen transport) across one flowering season at four elevation sites in the Himalaya–Hengduan Mountains region. Pollen analysis was conducted to determine which flower visitors acted as potential pollinators (pollen vectors) or as cheaters (those not carrying pollen of the visited plants). We tested whether there were topological differences between visitation and pollen transport networks and whether different taxonomic groups of insect visitors differed in their ability to carry pollen of the visited plants. Our results indicated that there was a significantly higher degree of specialization at both the network and species levels in the pollen transport networks in contrast to the visitation networks. Modularity was lower but nestedness was higher in the visitation networks compared to the pollen transport networks. All the cheaters were identified as peripheral species and most of them contributed positively to the nested structure. This may explain in part the differences in modularity and nestedness between the two network types. Bees carried the highest proportion of pollen of the visited plants. This was followed by Coleoptera, other Hymenoptera and Diptera. Lepidoptera carried the lowest proportion of pollen of the visited plants. Our study shows that the construction of pollen transport networks could provide a more in-depth understanding of plant–pollinator interactions. Moreover, it suggests that detecting and removing cheater interactions when studying the topology of other mutualistic networks might be also important.This study was supported by Strategic Priority Research Program of the Chinese Academy of Sciences (XDB31020000), National Key Basic Research Program of China (2014CB954100), Joint Fund of the National Natural Science Foundation of China-Yunnan Province (U1502261), Major International Joint Research Project of NSF China (31320103919), Applied Fundamental Research Foundation of Yunnan Province (2014GA003), National Natural Science Foundation of China (31700361), Yunlin Scholarship of Yunnan Province to H. Wang (YLXL20170001) and CAS ‘Light of West China’ Program to Y.H. Zhao. A. Lázaro was supported by a Ramóny Cajal contract financed by the Spanish Ministry of Economy and Competitiveness