Experimental Investigation of Wind Pressure Characteristics for Cladding of Dome Roofs

Cladding for dome roofs is often made of membrane materials that are light and easy to install. Due to these characteristics, wind damage to dome roof cladding is very common. In particular, open or retractable dome roofs are prone to wind damage because of inadequacies in wind load calculations. In this study, the wind pressure characteristics of a dome with a central opening were investigated. Wind tunnel tests were performed, and the pressure distribution was investigated by analyzing external and internal pressure coefficients. Based on the experimental results, the peak net pressure coefficients for the cladding design of a dome roof with a central opening were proposed. For the external peak pressure coefficients, the values of leeward regions were similar despite height–span ratios and turbulence intensity values. For the internal peak pressure coefficients, negative pressure was dominant, and the coefficients were not significantly affected by changes in height–span ratio. This tendency locally increased the negative peak net pressure, in which the load acts in the upward direction, and relatively significantly increased the positive peak net pressure, in which the load acts in the downward direction.

Sustained pharyngeal inflation on upper airway effects in infants---flexible bronchoscopy measurement

OBJECTIVE: Sustained pharyngeal inflation (SPI) with pharyngeal oxygen and nose-close (PhO2-NC) can create positive peak inflation pressure (PIP) inside the pharyngolaryngeal space (PLS). This study measured and compared effects of four different SPI durations in the PLS. METHOD: In this prospective observational study, 20 consecutive infants aged less than 3 years, scheduled for elective flexible-bronchoscopy were enrolled. SPI was performed twice in four different durations (0, 1, 3 and 5 seconds) sequentially in each infant. PIP was measured for each SPI in the pharynx, and simultaneously took images at two locations of oropharynx and supra-larynx. Infants’ demographic details and PIP levels, lumen expansion scores and images of PLS were measured and analyzed. RESULTS: Twenty infants with 40 measurements were collected. The mean (SD) age and weight were 11.6 (9.1) months and 6.8 (2.4) kg, respectively. The measured mean (SD) pharyngeal PIPs were 4.1 (3.3), 21.9 (7.0), 42.2 (12.3) and 65.5 (18.5) cm H2O at SPI duration of 0, 1, 3 and 5 seconds, respectively; which showed significant positive association (p<0.001). At assigned locations, the corresponding PLS images also show significant increase in lumen expansion scores and number of detected lesions with increase in SPI duration (p<0.001). The mean (SD) study time was 5.7 (1.2) minutes. No study related complication was noted. CONCLUSIONS: SPI with PhO2-NC up to 5 seconds is a simple, safe and feasible clinical ventilation modality. It may provide enough PIP to expand the PLS and facilitate flexible-bronchoscopy performance in infants.

A New Research Method for Corrosion Defect in Metal Pipeline by Using Pulsed Eddy Current

Pulsed eddy current (PEC) is a new technique to distinguish corrosion defeats inside and outside the metal pipeline. In comparison with other eddy current techniques, the PEC technique has the advantage of being simple and high velocity. In this article, a brand-new PEC probe based on differential conductivity is established through the combination of modules like square wave generator, eddy current coil bridge, differential current, voltage sample circuits and so on. The 50% duty cycle square wave is used as the driving signal. To measure differential conductance, a coil bridge configuration with two legs is adopted. One leg is composed of measurement eddy current coil and the in-series resistor, and the other is reference eddy current coil and the in-series resistor. Because the two legs go through defects in pipeline non-synchronously, there is a differential conductance between the two coils. A trans-impedance amplify circuit is used to detect coil eddy current. At the same time, two amplifiers are used to measure the differential voltage between the two coils. A 14 bit ADC is used to sample differential voltage, measurement and reference eddy currents which transferred to differential current by main processor Complex Programmable Logic Device (CPLD). CPLD is used to get differential conductance by differential current divide differential voltage. At last the eddy current signal sampling sequence is developed. A dynamic testing fixture with artificial defects carved on the pipeline is used to validate PEC probe’s accuracy. The differential conductance signals were displayed on the oscilloscope. Results showed that the inside defect had two peaks, positive peak and negative peak, but the outside defect only had one positive peak. We can conclude that the brand-new PEC probe has high accuracy in distinguishing the inside and outside defects.

Stress modulation of the seismic gap between the 2008 Ms 8.0 Wenchuan earthquake and the 2013 Ms 7.0 Lushan earthquake and implications for seismic hazard

SUMMARY Between 2008 and 2013, the Ms 8.0 Wenchuan earthquake and the Ms 7.0 Lushan earthquake occurred successively in the Longmenshan fault zone. Their aftershocks delineated a prominent seismic gap approximately 50 km long, hereafter referred to as the WLSG. The possibility of an event of Ms 7.0 or above occurring in the WLSG is a matter of great concern. In this study, we estimated the change of Coulomb failure stress (ΔCFS) along the WLSG caused by historical earthquakes in the last 300 yr. Our results revealed that 20 major earthquakes cast a stress shadow on the WLSG before 2008 (−148.7 to −7.0 kPa), hindering the rupture of the Wenchuan earthquake and the Lushan earthquake. The Wenchuan earthquake had an important influence on the stress redistribution of the WLSG, resulting in significant stress increase (14.7 to 337.5 kPa). As of 2018, although the negative ΔCFS caused by historical earthquakes (especially the Dayi earthquake) pushed the southern end of the WLSG away from failure, the positive peak ΔCFS of 323.0 kPa greatly encouraged the rupture of the northern WLSG. The small afterslip and weak microseismicity indicate that the WLSG is a stress barrier with high seismic potential, which can explain the mechanism of rupture termination of the Wenchuan earthquake and the Lushan earthquake.

Carbon-isotope stratigraphy of the Furongian Berry Head Formation (Port au Port Group) and Tremadocian Watts Bight Formation (St. George Group), western Newfoundland, and the correlative significance

Carbon-isotope stratigraphy of the Furongian (stage 10; Upper Cambrian) and Tremadocian (lowermost Ordovician) reveals distinct variations from the carbonates of the Berry Head and Watts Bight formations of the East Isthmus Bay section that accumulated in a shallow-marine setting on the eastern Laurentian platform in a passive margin setting in western Newfoundland, Canada. The East Isthmus Bay δ13C values show insignificant correlation with their Sr (R2 = 0.04), Mn (R2 = 0.001) and Fe (R2 = 0.02) counterparts, implying preservation of at least near-primary C-isotope compositions. The investigated section is largely fossil poor, but the δ13C profile shows a pattern with distinct variations that can be matched with those of the western Laurentian Lawson Cove Auxiliary Boundary Stratigraphic Section and Point (ASSP) section, Utah, USA. Therefore, it was possible to reconstruct a conodont biozonal scheme by matching the δ13C profile with its counterpart from the Lawson Cove ASSP section. At the base of the East Isthmus Bay section, the δ13C profile exhibits a broad excursion (the top of the Herllnmaria – Red Tops Boundary), which can be matched with the base of the Eoconodontus Zone (mid-Furongian), followed by an enrichment trend through the Cordylodus intermedius Zone (top Furongian). A positive excursion (Hirsutodontus simplex spike) is recorded in the Cordylodus intermedius Zone (top Cambrian), and a prominent positive peak characteristic for the Cordylodus lindstromi Zone is recorded from the top of the investigated section. The δ13C values of the Newfoundland carbonates are generally ∼1‰ Vienna Pee Dee Belemnite lower than those of Lawson Cove, which is likely attributable to a relatively higher productivity and (or) organic burial in the Utah region.

Neural dynamics underlying coherent motion perception in children and adults

Motion sensitivity increases during childhood, but little is known about the underlying neural correlates. Most studies investigating children’s evoked responses have not dissociated direction-specific and non-direction-specific responses. To isolate direction-specific responses, we presented coherently moving dot stimuli preceded by a period of incoherent motion, to 6- to 7-year-olds (n = 34), 8- to 10-year-olds (n = 34), 10- to 12-year-olds (n = 34) and adults (n = 20). Participants reported the direction of coherent motion while high-density EEG was recorded. Using a data-driven approach, we identified two stimulus-locked EEG components with distinct topographies: an early component with an occipital topography and a later, sustained positive component over centro-parietal electrodes. The component waveforms showed clear age-related differences, and scaled with motion coherence. In the early, occipital component, all groups showed a negativity peaking at ~300ms, like the previously reported coherent-motion N2. However, the children, unlike adults, showed an additional positive peak at ~200ms. The later positive response in the centro-parietal component rose more steeply for adults than for the youngest children, likely reflecting age-related changes in decision-making. These results suggest that children’s protracted development of coherent motion sensitivity is associated with gradual maturation of both early sensory and later decision-related processes.