Use of Morphological Method to Investigate the Influence of Surface Texture on Dimensional Measurement of Additively Manufactured Parts

The high level of surface roughness of additively manufactured (AM) parts post challenges to the applicability of different dimensional measurement techniques, including tactile, optical and XCT. Tactile measurement is traditionally considered to have the best accuracy and traceability. However, tactile measurement can be significantly affected by the mechanical filtering effect. This work sets out to investigate the influence of the mechanical filtering effect of tactile measurement on AM parts. Both experiential and simulation work are unitised to reveal this effect. Particularly the numerical simulation based on the morphological method allows the single influence factor, i.e., the tip diameter to be investigated. The maximum measurement errors caused by the stylus tip mechanical effect are determined by the convex hull points of the measurement profile, which is equivalent to using an infinitely large stylus tip. The CMM and XCT results of measuring the AM cylinder diameters are compared, along with the application of morphological method to “compensate” the mechanical filtering effect of the stylus tip

Sciences for The 2.5-meter Wide Field Survey Telescope (WFST)

The Wide Field Survey Telescope (WFST) is a dedicated photometric survey facility under construction jointly by the University of Science and Technology of China and Purple Mountain Observatory. It is equipped with a primary mirror of 2.5m in diameter, an active optical system, and a mosaic CCD camera of 0.73 Gpix on the main focus plane to achieve high-quality imaging over a field of view of 6.5 square degrees. The installation of WFST in the Lenghu observing site is planned to happen in the summer of 2023, and the operation is scheduled to commence within three months afterward. WFST will scan the northern sky in four optical bands (u, g, r, and i) at cadences from hourly/daily to semi-weekly in the deep high-cadence survey (DHS) and the wide field survey (WFS) programs, respectively. WFS reaches a depth of 22.27, 23.32, 22.84, and 22.31 in AB magnitudes in a nominal 30-second exposure in the four bands during a photometric night, respectively, enabling us to search tremendous amount of transients in the low-z universe and systematically investigate the variability of Galactic and extragalactic objects. Intranight 90s exposures as deep as 23 and 24 mag in u and g bands via DHS provide a unique opportunity to facilitate explorations of energetic transients in demand for high sensitivity, including the electromagnetic counterparts of gravitational-wave events detected by the second/third-generation GW detectors, supernovae within a few hours of their explosions, tidal disruption events and luminous fast optical transients even beyond a redshift of 1. Meanwhile, the final 6-year co-added images, anticipated to reach g about 25.5 mag in WFS or even deeper by 1.5 mag in DHS, will be of significant value to general Galactic and extragalactic sciences. The highly uniform legacy surveys of WFST will also serve as an indispensable complement to those of LSST which monitors the southern sky.Comment: 46 pages, submitted to SCMP

Preparation of grape pomace powders and analysis of their nutritive compositions

Grape pomace (GP) is produced in large amounts worldwide, leading to waste of resources and environmental pollution. Using grapes grown in eastern China, the main nutrients and polyphenols in grape seeds (GS), skin (GSK), and GP powders were determined by conventional chemical composition analysis and HPLC-MS/MS. The antioxidative activity of a GP polyphenol extract was identified using DPPH and hydroxyl radical scavenging assays and reducing power assay. GSK and GP contained less total dietary fiber than GS. The total polyphenolic content of GS was significantly higher than that of GSK and GP. The hydrogen- and electron-donating activities of the GP polyphenol extract were superior to those of vitamin C

Combined effects of internal and external pressures for a building with wall openings

This paper was reviewed and accepted by the APCWE-IX Programme Committee for Presentation at the 9th Asia-Pacific Conference on Wind Engineering, University of Auckland, Auckland, New Zealand, held from 3-7 December 2017

Investigation of Coupling Effects of Wave, Current, and Wind on a Pile Foundation

To investigate the coupling effects of wave–wind, wave–current, and wave–current–wind on a pile foundation of a marine structure, harbor basin tests on loads induced by single and combined action of wave, current, and wind were conducted. The time histories, power spectrums, and characteristic values of drag forces in the test conditions were compared. Then, the coupling coefficients were calculated based on the characteristic values to quantitively evaluate the coupling effects. The influence of natural vibration of the pile on the characteristic values and coupling effects were studied by comparing the test loads between rigid and elastic models. The results show that the shapes of power spectrums of drag forces and their peak frequencies in the wave-involved conditions are similar to the spectrum of incident wave, which means that the steady current and uniform wind cannot change the frequency distribution of incident random wave. Although the drag forces of rigid and elastic model under wave–wind, wave–current, and wave–current–wind are not the linear superposition of corresponding single field, the coupling effects among them are quite weak as the coupling coefficients are small. It is speculated that the weak wave–wind coupling effect may be because, firstly, the interaction of wave and wind is limited to the zone near the water surface, which is far less than the height of the model; secondly, the wave-induced load is dominant compared to wind and current. The loads in test conditions of elastic model are similar to the rigid model; for that, the model’s natural frequency is far away from the peak spectral frequency of incident wave, having little influence on the drag force

Investigation of Coupling Effects of Wave, Current, and Wind on a Pile Foundation

To investigate the coupling effects of wave–wind, wave–current, and wave–current–wind on a pile foundation of a marine structure, harbor basin tests on loads induced by single and combined action of wave, current, and wind were conducted. The time histories, power spectrums, and characteristic values of drag forces in the test conditions were compared. Then, the coupling coefficients were calculated based on the characteristic values to quantitively evaluate the coupling effects. The influence of natural vibration of the pile on the characteristic values and coupling effects were studied by comparing the test loads between rigid and elastic models. The results show that the shapes of power spectrums of drag forces and their peak frequencies in the wave-involved conditions are similar to the spectrum of incident wave, which means that the steady current and uniform wind cannot change the frequency distribution of incident random wave. Although the drag forces of rigid and elastic model under wave–wind, wave–current, and wave–current–wind are not the linear superposition of corresponding single field, the coupling effects among them are quite weak as the coupling coefficients are small. It is speculated that the weak wave–wind coupling effect may be because, firstly, the interaction of wave and wind is limited to the zone near the water surface, which is far less than the height of the model; secondly, the wave-induced load is dominant compared to wind and current. The loads in test conditions of elastic model are similar to the rigid model; for that, the model’s natural frequency is far away from the peak spectral frequency of incident wave, having little influence on the drag force

Computational Investigation of Wind Loads on Tilted Roof-Mounted Solar Array

A detailed computational investigation of the wind field around tilted solar modules mounted on a large building roof has been undertaken, utilizing the Reynolds-Averaged Navier-Stokesv (RANS) approach supplied with the SST k − ω turbulence model. The study investigated the flow field for various tilt angle of modules at normal wind directions relative to the wall. Then the shape factors and moment coefficients of modules were explored. The results show that the recirculation vortex generated by the building edge is disintegrated to smaller local vortices. With the increasing of the tilt angle, an increasing number of local vortices emerged at the leading rows, leading to a relatively large wind pressure and shape factor at the corner of the array. In most tilt angles at 0° and 180° wind direction the shape factors are negative. However, for the 40° and 55° tilt angles at 180° wind direction, the shape factors on the lower surfaces are positive, due to the dominating of approaching flow rather than the local vortices. The array is divided into six zones based on the distribution of shape factors. As the shape factors on upper and lower are similar, the shape factors in most zones for tilt angles from 5° to 55° are quite small. However, shape factors in the leading row for 30°, 40° and 55° are relatively large. This indicates that the shading effect of front rows can significantly reduce the shape factors of the rear rows. Compared to the values calculated by Chinese, American and Japanese standards, the shape factors by simulation are quite small. The moment induced by nonuniform wind pressure, which is often ignored in the literature and standards, is quite large at the leading zones, with a maximum of 0.28 for 55° tilt angle. Ignoring the wind induced moment on the leading zones may make the wind resistance design of the solar module support structure unsafe