Effects of Ship Propulsion Shafting Alignment on Whirling Vibration and Bearing Temperature Response

Ship’s propulsion shafting is one of the main sources of ship vibration and noise. The shafting, whirling vibrations, and alignment are important factors that affect the comfort, stability, and reliability during a ship’s navigation. However, the mechanism of the interacting of the both factors is not fully revealed. In this paper, the effect of shafting alignment on whirling vibration and the bearing temperature response is studied by experiment. The test scheme is designed reasonably according to the theoretical analysis. The results show that the horizontal component of the shafting whirling vibration can be effectively reduced by adjusting the shafting alignment state while the vertical component is not. The shafting axis balancing position (SABP) slightly moves upward in high speed, which should be considered in the dynamic alignment design of the shafting, especially for the high-speed shafting. Little ABSB (the angle between the shafting centre line and the No. 1 bearing centre line) is beneficial to the stable operation of shafting, while appropriately increasing the ABSB and bearing load is beneficial to reducing the shafting whirling vibration. By balancing the relationship between bearing load and ABSB, the performance of whirling vibration and bearing temperature response can be optimized.

Acoustic focusing of beads and cells in hydrogel droplets

The generation of hydrogel droplets using droplet microfluidics has emerged as a powerful tool with many applications in biology and medicine. Here, a microfluidic system to control the position of particles (beads or astrocyte cells) in hydrogel droplets using bulk acoustic standing waves is presented. The chip consisted of a droplet generator and a 380 µm wide acoustic focusing channel. Droplets comprising hydrogel precursor solution (polyethylene glycol tetraacrylate or a combination of polyethylene glycol tetraacrylate and gelatine methacrylate), photoinitiator and particles were generated. The droplets passed along the acoustic focusing channel where a half wavelength acoustic standing wave field was generated, and the particles were focused to the centre line of the droplets (i.e. the pressure nodal line) by the acoustic force. The droplets were cross-linked by exposure to UV-light, freezing the particles in their positions. With the acoustics applied, 89 ± 19% of the particles (polystyrene beads, 10 µm diameter) were positioned in an area ± 10% from the centre line. As proof-of-principle for biological particles, astrocytes were focused in hydrogel droplets using the same principle. The viability of the astrocytes after 7 days in culture was 72 ± 22% when exposed to the acoustic focusing compared with 70 ± 19% for samples not exposed to the acoustic focusing. This technology provides a platform to control the spatial position of bioparticles in hydrogel droplets, and opens up for the generation of more complex biological hydrogel structures.

Spatio-temporal flow variations driving heat exchange processes at a mountain glacier

Multi-scale interactions between the glacier surface, the overlying atmosphere, and the surrounding alpine terrain are highly complex and force temporally and spatially variable local glacier energy fluxes and melt rates. A comprehensive measurement campaign (Hintereisferner Experiment, HEFEX) was conducted during August 2018 with the aim to investigate spatial and temporal dynamics of the near-surface boundary layer and associated heat exchange processes close to the glacier surface during the melting season. The experimental set-up of five meteorological stations was designed to capture the spatial and temporal characteristics of the local wind system on the glacier and to quantify the contribution of horizontal heat advection from surrounding ice-free areas to the local energy flux variability at the glacier. Turbulence data suggest that temporal changes in the local wind system strongly affect the micrometeorology at the glacier surface. Persistent low-level katabatic flows during both night and daytime cause consistently low near-surface air temperatures with only small spatial variability. However, strong changes in the local thermodynamic characteristics occur when westerly flows disturbed this prevailing katabatic flow, forming across-glacier flows and facilitating warm-air advection from the surrounding ice-free areas. Such heat advection significantly increased near-surface air temperatures at the glacier, resulting in strong horizontal temperature gradients from the peripheral zones towards the centre line of the glacier. Despite generally lower near-surface wind speeds during across-glacier flow, peak horizontal heat advection from the peripheral zones towards the centre line and strong transport of turbulence from higher atmospheric layers downward resulted in enhanced turbulent heat exchange towards the glacier surface at the glacier centre line. Thus, at the centre line of the glacier, exposure to strong larger-scale westerly winds promoted heat exchange processes, potentially contributing to ice melt, while at the peripheral zones of the glacier, stronger sheltering from larger-scale flows allowed the preservation of a katabatic jet, which suppressed the efficiency of the across-glacier flow to drive heat exchange towards the glacier surface by decoupling low-level atmospheric layers from the flow aloft. A fuller explanation of the origin and structure of the across-glacier flow would require large-eddy simulations.

Análise da mobilidade e da acessibilidade por agrupamento de bairros por meio da sintaxe espacial

O artigo apresenta o perfil da cidade de Campina Grande – PB sob a ótica da Sintaxe Espacial com fundamento na Teoria da Lógica social do Espaço. Na metodologia adotada, utilizou-se o modelo que parte da elaboração do mapa Road Centre Line – RCL que serviu de base para a obtenção da Análise Angular de Segmentos, via softwares Depthmap® e QGIS 2.14, geradores das medidas sintáticas apresentadas nos resultados. Os objetivos propostos no presente estudos foram alcançados, pois os resultados obtidos demonstram que na cidade coexistem espaços com características orgânicas e planejadas, o que reflete aspectos socioculturais de ocupação e povoamento da cidade ao longo de sua formação predominantemente heterogenia. Quanto à forma urbana percebe-se uma configuração composta por um núcleo integrador, situado no centro urbano. No que refere-se às medidas encontradas, têm-se os valores médios obtidos do NAIN (1,007), do NACH (0,911) e do INCH (12.213) para a cidade como um todo. Na análise por bairros identificou-se que 56% do conjunto urbano apresentam um NAIN médio acima do índice mínimo do intervalo inferior (1,00 - 1,67); 94% estão acima do NACH mínimo do intervalor inferior (0,8 – 1,4); e 46% acima INCH médio encontrado para toda a cidade. Sendo assim, concluiu-se que as regiões centrais parecem apresentar, de acordo com os dados obtidos, uma configuração mais favorável à mobilidade e à acessibilidade, tendo nos bairros periféricos aspectos segregacionistas que podem explicar a restrição de movimento dos indivíduos quanto ao acesso de bens e serviços na urbe. Diante desse mapeamento é possível para os planejadores urbanos direcionar novos estudos nessas regiões que demandam maior necessidade de intervenção para melhoria e integração urbanística na malha urbana local.

Can statistics of turbulent tracer dispersion be inferred from camera observations of SO₂ in the ultraviolet? A modelling study

Atmospheric turbulence and in particular its effect on tracer dispersion may be measured by cameras sensitive to the absorption of ultraviolet (UV) sunlight by sulfur dioxide (SO2), a gas that can be considered a passive tracer over short transport distances. We present a method to simulate UV camera measurements of SO2 with a 3D Monte Carlo radiative transfer model which takes input from a large eddy simulation (LES) of a SO2 plume released from a point source. From the simulated images the apparent absorbance and various plume density statistics (centre-line position, meandering, absolute and relative dispersion, and skewness) were calculated. These were compared with corresponding quantities obtained directly from the LES. Mean differences of centre-line position, absolute and relative dispersions, and skewness between the simulated images and the LES were generally found to be smaller than or about the voxel resolution of the LES. Furthermore, sensitivity studies were made to quantify how changes in solar azimuth and zenith angles, aerosol loading (background and in plume), and surface albedo impact the UV camera image plume statistics. Changing the values of these parameters within realistic limits has negligible effects on the centre-line position, meandering, absolute and relative dispersions, and skewness of the SO2 plume. Thus, we demonstrate that UV camera images of SO2 plumes may be used to derive plume statistics of relevance for the study of atmospheric turbulent dispersion.

Continuous Measurement of Three-Dimensional Root Canal Curvature Using Cone-Beam Computed and Micro-Computed Tomography: A Comparative Study

The knowledge of root canal curvature is crucial regarding the prevention of ledge formation, root perforation and the possibility of endodontic instruments’ fracture during endodontic treatments. Therefore, a quantification method of the root canal curvature as well as the applicability of diagnostically relevant tomographic three-dimensional (3D) imaging data is necessary. Hereby, cone-beam computed tomography (CBCT) images and micro-computed tomography (µCT) data of distal root canals were analysed concerning the continuous three-dimensional curvature of human mandibular molars ( n = 50). The curvature of the canal’s three-dimensional centre line was determined by evaluating the tomographic images. The centroids of each root canal slice were identified and approximated by spline curves to obtain the centre line and therefore, its curvature. Comparing the results evaluated from CBCT and µCT images, minimum radii of curvature of 2.6 mm and 2.1 mm were determined, respectively. The observation of the centre line demonstrated the requirement of the three-dimensional imaging data from CBCT and µCT for a reliable curvature analysis. Conclusively, the evaluation of CBCT and µCT images results in comparable radii of curvature. Thus, the application of the introduced method in combination with CBCT applied to patient cases could offer an important preliminary diagnostical step to prevent endodontic treatment complications.

Cost Comparison of a Building Project by Manual and BIM

This article focuses on comparison between Manual/Traditional and Building Information Modelling (BIM) software based approaches for cost comparison. Centre line method for manual and Revit software for BIM based approaches are used in this research. The principal objectives of this research are to calculate quantities by Manual Centre line method, then to make the cost estimation fast, accurate, efficient, and errorless by using BIM software Rivet, and finally the comparison study of manual based and BIM / Software based estimation. For manual approach, quantities are calculated by multiplying the measurements of length, breadth, and height. Then to get the total quantities the deduction is subtracted from the quantities and final BOQ is prepared for which estimated cost of building is calculated. For BIM based approach, 3D model from 2D floor plan of building is prepared in Revit software, then to estimate the cost of building structure elements, sheets of quantities are generated in the schedule option of the view tab in the software. The Percentage difference between Manual and BIM / Revit Software estimation in brick work, RCC Slab, Plaster Work, PCC for Flooring, Floor Tile Work, Skirting, Paint Work, False Ceiling, Doors and Aluminum Work is 4.57, 2.61, 7.58, 3.27, 1.87, 6.73, 8.03, 1.87, and 0.00% respectively. The total cost difference between manual and BIM based estimation approach comes out to be 4.8%. It is thus concluded that the BIM-assisted estimates have better performance over traditional/manual estimating methods.