Evaluation of the mechanical anisotropy of lacustrine smectite clays by triaxial test analysis

This paper describes the role of fabric anisotropy during clayey soil deformation. A set of triaxial tests was performed on vertical and horizontal specimens of undisturbed smectite lake sediments from Jurica, Queretaro in Mexico. The results allowed to analyze the influence of bedding and discontinuities on the mechanical behavior of Jurica clays after failure. Tests with applied low strain rates allowed pore pressure equalization within specimens with different gravimetric water content and degree of saturation. Shear failure results of undrained tests showed that deformation distributes differently in both horizontal and vertical directions and that stress may be dissipated by pore collapses, fractures and particle deformation. The experimental evidence suggests that microfabric is a relevant variable in the overall mechanical response of clayey sediments that depends on the natural fabric (bedding and discontinuities), mineralogy, and water content. A detailed analysis of Young´s Moduli (E) showed the high variability of this parameter from 108 to 409 kg/cm2 (calculated at 30% of σdmax) and its dependence on the orientation of the specimen and the water content. In addition, p’-q’ graphs illustrate the relevance of considering mechanical anisotropy in clays and provide further insights to understand the role of smectites in progressive shear deformation.

The Benefit of Horizontal Photovoltaic Panels in Reducing Wind Loads on a Membrane Roofing System on a Flat Roof

The present paper proposes a measure for improving the wind-resistant performance of photovoltaic systems and mechanically attached single-ply membrane roofing systems installed on flat roofs by combining them together. Mechanically attached single-ply membrane roofing systems are often used in Japan. These roofing systems are often damaged by strong winds, because they are very sensitive to wind action. Recently, photovoltaic (PV) systems placed on flat roofs have become popular. They are also often damaged by strong winds directed onto the underside, which cause large wind forces onto the PV panels. For improving the wind resistance of these systems, we proposed to install PV panels horizontally with gaps between them. Such an installation may decrease the wind forces on the PV panels due to the pressure equalization effect as well as on the waterproofing membrane due to the shielding effect of the PV panels. This paper discusses the validity of such an idea. The pressure on the bottom surface of a PV panel, called the “layer pressure” here, was evaluated by a numerical simulation based on the unsteady Bernoulli equation. In the simulation, the time history of the external pressure coefficients, measured at many points on the roof in a wind tunnel, was employed. It was found that the wind forces, both on the PV panels and on the roofing system, were significantly reduced. The reduction was large near the roof’s corner, where large suction pressures were induced in oblique winds. Thus, the proposed method improved the wind resistance of both systems significantly.

Numerical Study of a Horizontal Wind Turbine under Yaw Conditions

Over recent years, considerable attention has been devoted to the optimization of energy production in wind farms, where yaw angles can play a significant role. In order to quantify and maximize such potential power, the simulation of wakes is vital. In the present study, an actuator line model code was implemented in the OpenFOAM flow solver. A tip treatment was applied to involve the tip effect induced by the pressure equalization from the suction and pressure sides. The Leishman–Beddoes dynamic stall (LB-DS) model modified by Sheng et al. was employed to consider the dynamic stall phenomenon. The developed ALM-CFD solver was validated for the NREL Phase VI wind turbine reference case. The solver was then used in simulating the yawed wind turbine, and power variation was compared with UBEM and CFD. Overall, according to the obtained data, the coupled solver compared well with CFD. There was an improvement in terms of prediction of the phase delay that is due to the dynamic stall. However, there was still negligible overestimation in deep stall conditions. Based on the obtained results, it is suggested that the reduction of power output follows a cosine to the power of X function of the yaw angle. In terms of visualizing wake, the results demonstrated that the current ALM code was satisfying enough to simulate skewed wake and vortices trajectory. The effect of advancing and retreating blade was captured. It was found that yaw led to the concentration of the induced velocity downstream, resulting in a lower velocity deficit on a broader area, which is essential for wind farm optimization.

Objective Synoptic Weather Classification on Air Pollution during Winter Seasons in Hangzhou

Using the 2015-2018 Hangzhou city PM2.5, PM10, SO2, CO, NO2 and O3 mass concentration data, ERA5 reanalysis data and ground observation data, through the PCT classification method, the objective analysis of the winter air pollution weather situation in Hangzhou was obtained. The results showed that the winter air quality concentration in Hangzhou continued to be high from 2015 to 2018, and the air pollution was the most significant. Through objective classification, it is concluded that the main weather conditions affecting the region in winter are divided into 6 types, namely high pressure control, high pressure bottom control equalizing field, L-shaped high pressure control, high pressure front control equalizing field, low pressure control, low pressure front control Equalizing field. Among them, when high pressure control, high pressure bottom control equalizing field, L high pressure control, low pressure control are affected by local sources, the impact of external sources has a greater impact on the air quality in Hangzhou, and air pollution is prone to occur; before low pressure When the pressure equalization field is controlled by the Ministry and the pressure equalization field is controlled by the high pressure front, the local wind and precipitation in Hangzhou are relatively high, which is not conducive to the accumulation of air pollutants. The probability of occurrence of air pollution is small, and air pollution is not easy to occur.

Prospective study on the Eustachian tube function during Frenzel maneuver in a hypobaric/hyperbaric pressure chamber

Introduction The Frenzel maneuver describes a technique for middle ear equalizing which is frequently used by apnea divers. It offers advantages compared to the most commonly used techniques such as the Valsalva or Toynbee maneuver. Until now, there is insufficient literature about the pressure dynamics and Eustachian tube (ET) function during the Frenzel maneuver. The aim of the present study was to characterize the ET function during the Frenzel maneuver. Materials and methods By means of an established standardized profile of compression and decompression in a hypo/hyperbaric pressure chamber, we examined different parameters such as the ET opening pressure (ETOP), ET opening duration (ETOD), and ET opening frequency (ETOF) in 11 experienced apnea divers and compared them to the parameters during the Valsalva and Toynbee maneuver. Results Standard values for ETOP, ETOD, and ETOF could be established for the Frenzel maneuver under standardized conditions in a hypo/hyperbaric pressure chamber. Compared to the Frenzel maneuver, ETOP was higher and ETOD longer (both p < 0.001) during the Valsalva maneuver whereas ETOP was lower and ETOD shorter (both p < 0.001) during the Toynbee maneuver. No difference regarding ETOF was observed between the Frenzel, Valsalva, and Toynbee maneuver. Discussion The Frenzel maneuver was shown to be at least as effective as the Valsalva maneuver concerning ET opening. We believe that knowledge of the Frenzel technique might facilitate the pressure equalization during diving and recommend implementation of an appropriate equalization training in apnea and scuba diving education.

Analysis of the skin wrinkling in out-of-plane joints of CFRP hat-shaped structure

Out-of-plane joints, between hat (omega) stiffeners and skin panels are asymmetric parts of the composite structure. Studies show that physical-mechanical conditions in these joints significantly affect skin forming quality. In the present article, aimed to investigate the mechanism of the skin wrinkle in the joints of carbon fiber reinforced plastics (CFRP) hat-shaped structure, the pressure testing apparatus based on the Pascal principle is used to surveillance the resin pressure dynamically in out-of-plane joints. In this regard, several influencing factors such as first-order holding time, forming pressure and relative volume of unidirectional fillers are studied. Obtained results show that increasing the first stage holding time can prolong the viscous flow state of the resin, and time to achieve pressure equalization at each detection point, thereby improving the dispersion of the pressure and reducing the possibility of wrinkles. It is found that as the forming pressure increases, the degree of skin wrinkles in the out-of-plane joints ameliorates. Moreover, for fillers with a relative volume within the range of 0–50%, the pressure transfer effect and the skin flatness is relatively dissatisfactory. It is concluded that the filler with a relative volume of 80–120% improves the skin wrinkle in out-of-plane joints.

Middle Ear Barotraumas in Commercial Aircrew

BACKGROUND: Middle ear (ME) barotraumas are the most common condition in aviation medicine, sometimes seriously compromising flight safety. Considering this and the ever-increasing amount of commercial aviation, a detailed overview is warranted.METHODS: In this survey study, an anonymous, electronic questionnaire was distributed to commercial aircrew of the three major commercial airlines operating in Finland (N 3799), covering 93% of the target population (i.e., all commercial aircrew operating in Finland, N 4083). Primary outcomes were self-reported prevalence, clinical characteristics, and health and occupational effects of ME barotraumas in flight. Secondary outcomes were adjusted odds ratios (OR) for frequency of ME barotraumas with respect to possible risk factors.RESULTS: Response rate was 47% (N 1789/3799), with 85% (N 1516) having experienced ME barotraumas in flight. Of those affected, 60% had used medications, 5% had undergone surgical procedures, and 48% had been on sick leave due to ME barotraumas (40% during the last year). Factors associated with ME barotraumas included a high number of upper respiratory tract infections [3 URTIs/yr vs. 0 URTIs/yr: OR, 9.02; 95% confidence interval (CI) 3.9920.39] and poor subjective performance in Valsalva (occasionally vs. always successful: OR, 7.84; 95% CI 3.9715.51) and Toynbee (occasionally vs. always successful: OR, 9.06; 95% CI 2.6730.78) maneuvers.CONCLUSION: ME barotraumas were reported by 85% of commercial aircrew. They lead to an increased need for medications, otorhinolaryngology-related surgical procedures, and sickness absence from flight duty. Possible risk factors include a high number of URTIs and poor performance in pressure equalization maneuvers.Lindfors OH, Ketola KS, Klockars TK, Leino TK, Sinkkonen ST. Middle ear barotraumas in commercial aircrew. Aerosp Med Hum Perform. 2021; 92(3):182189.

Functional Impacts of Aminoglycoside Treatment on Speech Perception and Extended High-Frequency Hearing Loss in a Pediatric Cystic Fibrosis Cohort

Purpose The purpose of this study is to better understand the prevalence of ototoxicity-related hearing loss and its functional impact on communication in a pediatric and young adult cohort with cystic fibrosis (CF) and individuals without CF (controls). Method We did an observational, cross-sectional investigation of hearing function in children, teens, and young adults with CF ( n = 57, M = 15.0 years) who received intravenous aminoglycoside antibiotics and age- and gender-matched controls ( n = 61, M = 14.6 years). Participants completed standard and extended high-frequency audiometry, middle ear measures, speech perception tests, and a hearing and balance questionnaire. Results Individuals with CF were 3–4 times more likely to report issues with hearing, balance, and tinnitus and performed significantly poorer on speech perception tasks compared to controls. A higher prevalence of hearing loss was observed in individuals with CF (57%) compared to controls (37%). CF and control groups had similar proportions of slight and mild hearing losses; however, individuals with CF were 7.6 times more likely to have moderate and greater degrees of hearing loss. Older participants displayed higher average extended high-frequency thresholds, with no effect of age on average standard frequency thresholds. Although middle ear dysfunction has not previously been reported to be more prevalent in CF, this study showed that 16% had conductive or mixed hearing loss and higher rates of previous otitis media and pressure equalization tube surgeries compared to controls. Conclusions Individuals with CF have a higher prevalence of conductive, mixed, and sensorineural hearing loss; poorer speech-in-noise performance; and higher rates of multiple symptoms associated with otologic disorders (tinnitus, hearing difficulty, dizziness, imbalance, and otitis media) compared to controls. Accordingly, children with CF should be asked about these symptoms and receive baseline hearing assessment(s) prior to treatment with potentially ototoxic medications and at regular intervals thereafter in order to provide otologic and audiologic treatment for hearing- and ear-related problems to improve communication functioning.