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Based on the detected vibration signal, a measurement system was designed to solve the current problem of closed centrifuge speed measurement. The system collected and adjusted the signal collected by the vibration sensor, and then send it to the control unit STM32 for spectrum analysis to get the speed frequency. The sampling data was analysed and processed in PC through serial communication. Programs were written to achieve data sampling, filtering and storage, and the important parameters such as acceleration waveforms, vibration frequency and actual speed were displayed on the screen. The experimental results show that the system can accurately calculate the real-time speed of the closed centrifuge according to the measured vibration signals, which has the advantages of high stability, detection accuracy and real-time performance.

This work is devoted to the study of centrifugation processes, which are one of the most complex processes of technology. The use of the action of the centrifugal force field for the separation of heterogeneous liquid systems in a rotor system (centrifuge) is very effective. Separability of centrifuged materials, multiphase dispersion, the relationship between phases cause ambiguous processes of centrifugation, and therefore it is not always possible to accurately predict and evaluate the main characteristics of the separation of heterogeneous systems in the centrifugal force field. For a qualitative assessment of the main separation characteristics, such as the angular velocity of rotation, the dependence of the angles of inclination of the glasses on the angular velocity, the settling time of particles, etc., is created a mathematical model of the vertical rotor system. The rotor represents a round disk on which cups (vial) with a multiphase liquid are symmetrically suspended. A particular case of a fixed rotor is considered. Nonlinear differential equations of motion of the suspension particle, which have no exact solution, are obtained. The research is conducted by analytical and numerical methods. The dependence of the slope angles of the tubes from the angular rotational speed of the rotor, sedimentation curves are obtained , which allow estimating the time of particle deposition and the effect of the particle size distribution on the separation process. The results of this research work allow us to determine with sufficient accuracy all the necessary characteristics of the sedimentation working process, and also, in certain cases, it is possible to exclude the conduct of experimental work. The results of the work confirm the physical meaning of the process, which can serve as a justification for the use and introduction of this mathematical model in industrial production.

The disc stack centrifuge (DSC) in the virgin olive oil (VOO) industry is widely used for oil purification at a final stage of extraction process. The obtained oil should be commercialized directly as turbid or sent to settling and/or filtration. Despite technology is strongly consolidated, few literature is available on the effect of DSC on efficiency and quality of VOO, specially compared with alternative methods. Alternative technologies to DSC like settling or direct filtration are suitable only for very small production scale. Application of advanced technology already available for DSC like hermetic design is applicable also to VOO but more research is necessary to establish effect on quality and cost/benefit ratio. Improvement of installation module and a more appropriate use of DSC on VOO industry are recommended to reduce water consumption and consequent loss of VOO quality.

Copyright of Petroleum Refinery Engineering is the property of Petroleum Refinery Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Key points: The aim of this study was to determine the effect of rotational axis position (RAP and thus g‐gradient) during short‐arm human centrifugation (SAHC) upon cardiovascular responses, cerebral perfusion and g‐tolerance.In 10 male and 10 female participants, 10 min passive SAHC runs were performed with the RAP above the head (P1), at the apex of the head (P2), or at heart level (P3), with foot‐level Gz at 1.0 g, 1.7 g and 2.4 g.We hypothesized that movement of the RAP from above the head (the conventional position) towards the heart might reduce central hypovolaemia, limit cardiovascular responses, aid cerebral perfusion, and thus promote g‐tolerance.Moving the RAP footward towards the heart decreased the cerebral tissue saturation index, calf circumference and heart rate responses to SAHC, thereby promoting g‐tolerance.Our results also suggest that RAP, and thus g‐gradient, warrants further investigation as it may support use as a holistic spaceflight countermeasure. Artificial gravity (AG) through short‐arm human centrifugation (SAHC) has been proposed as a holistic spaceflight countermeasure. Movement of the rotational axis position (RAP) from above the head towards the heart may reduce central hypovolaemia, aid cerebral perfusion, and thus promote g‐tolerance. This study determined the effect of RAP upon cardiovascular responses, peripheral blood displacement (i.e. central hypovolaemia), cerebral perfusion and g‐tolerance, and their inter‐relationships. Twenty (10 male) healthy participants (26.2 ± 4.0 years) underwent nine (following a familiarization run) randomized 10 min passive SAHC runs with RAP set above the head (P1), at the apex of the head (P2), or at heart level (P3) with foot‐level Gz at 1.0 g, 1.7 g and 2.4 g. Cerebral tissue saturation index (cTSI, cerebral perfusion surrogate), calf circumference (CC, central hypovolaemia), heart rate (HR) and digital heart‐level mean arterial blood pressure (MAP) were continuously recorded, in addition to incidence of pre‐syncopal symptoms (PSS). ΔCC and ΔHR increases were attenuated from P1 to P3 (ΔCC: 5.46 ± 0.54 mm to 2.23 ± 0.42 mm; ΔHR: 50 ± 4 bpm to 8 ± 2 bpm, P < 0.05). In addition, ΔcTSI decrements were also attenuated (ΔcTSI: −2.85 ± 0.48% to −0.95 ± 0.34%, P < 0.05) and PSS incidence lower in P3 than P1 (P < 0.05). A positive linear relationship was observed between ΔCC and ΔHR with increasing +Gz, and a negative relationship between ΔCC and ΔcTSI, both independent of RAP. Our data suggest that movement of RAP towards the heart (reduced g‐gradient), independent of foot‐level Gz, leads to improved g‐tolerance. Further investigations are required to assess the effect of differential baroreceptor feedback (i.e. aortic–carotid g‐gradient). Key points: The aim of this study was to determine the effect of rotational axis position (RAP and thus g‐gradient) during short‐arm human centrifugation (SAHC) upon cardiovascular responses, cerebral perfusion and g‐tolerance.In 10 male and 10 female participants, 10 min passive SAHC runs were performed with the RAP above the head (P1), at the apex of the head (P2), or at heart level (P3), with foot‐level Gz at 1.0 g, 1.7 g and 2.4 g.We hypothesized that movement of the RAP from above the head (the conventional position) towards the heart might reduce central hypovolaemia, limit cardiovascular responses, aid cerebral perfusion, and thus promote g‐tolerance.Moving the RAP footward towards the heart decreased the cerebral tissue saturation index, calf circumference and heart rate responses to SAHC, thereby promoting g‐tolerance.Our results also suggest that RAP, and thus g‐gradient, warrants further investigation as it may support use as a holistic spaceflight countermeasure. [ABSTRACT FROM AUTHOR]

The need to tunnel closely beneath piles is increasing due to the development of urban areas. This poses a risk to the stability and serviceability of overlying structures (e.g., buildings, piers, and piled embankments). The impact of tunneling on piles is usually assessed using a displacement threshold, yet this provides no information about the posttunneling pile safety factor. Knowledge of a pile's safety factor under serviceability or extreme loading conditions is important, especially if future repurposing of the associated superstructure is a possibility. Tunneling can reduce the safety factor of a pile up to the point of geotechnical failure (i.e., when the pile capacity reduces to that of the applied load), yet little guidance is available to enable a straightforward means of assessing the posttunneling safety factor of a pile. This paper aims to address this shortcoming by providing design charts based on an analytical tunnel-single pile interaction approach that provides a means of determining a posttunneling pile safety factor. The methodology and design charts are applicable to drained soil conditions and include for the effects of the initial pile safety factor, the pile installation method [displacement (driven and jacked), nondisplacement (bored) with only the shaft capacity, and nondisplacement with base and shaft capacity] and varying water table depths. In the paper, as a validation exercise, analytical predictions are compared against data from geotechnical centrifuge tests designed to model both displacement and nondisplacement piles in sands, including a variety of tunnel–pile relative locations and initial pile safety factors. For a specified design value of a posttunneling pile safety factor, the design charts enable a quick assessment of the safe location of a pile or a tolerable tunnel volume loss considering ground parameters, water table position, pile installation method, and initial safety factor. [ABSTRACT FROM AUTHOR]

A mathematical model is proposed to calculate the total separation effectiveness in terms of GT for a disk stack centrifuge taking account of the variation of the centrifugal force with a position in the disk. In practice, the centrifuge ability/force is often referred as Relative Centrifugal Force (RCF) or G number, which is a multiple of the centrifugal acceleration over the gravitational acceleration. As the radial velocity varies it is important to integrate the relative centrifuge force, here in terms of the G number along the path taking account of the change in velocity. The separation effectiveness, GT is defined as an integrated product of local G number, G(x) and local residential time (dt), where dt is the time taken for the bulk fluid to traverse a distance from r to r+ dr. The GT value calculated for a disk type centrifuge can be compared with the GT value of others and compared with a bench top fixed rotor centrifuge. An industrial centrifuge would be expected to be able to deliver similar separation performance to a pilot or a lab scale one, if operated at the same/similar value of GT. This would allow the performance of a full-scale clarifier to be predicted. This model is, in essence, a simple alternative to the Sigma concept. [ABSTRACT FROM AUTHOR]

Microgravity during long-term space flights induces degeneration of articular cartilage. Artificial gravity through centrifugation combined with exercise has been suggested as a potential countermeasure for musculoskeletal degeneration. The purpose of this study was to investigate the effect of different types of impact loading under normal and artificial gravity conditions on serum concentrations of cartilage oligomeric matrix protein (COMP), a biomarker of cartilage metabolism. Fifteen healthy male adults (26 ± 4 years, 181 ± 4 cm, 77 ± 6 kg) performed four different 30-min impact loading protocols on four experimental days: jumping with artificial gravity elicited by centrifugation in a short-arm centrifuge (AGJ), jumping with artificial gravity generated by low-pressure cylinders in a sledge jump system (SJS), vertical jumping under Earth gravity (EGJ), and running under Earth gravity (RUN). Five blood samples per protocol were taken: 30 min before, immediately before, immediately after, 30 min after, and 60 min after impact loading. Serum COMP concentrations were analyzed in these samples. During the impact exercises, ground reaction forces were recorded. Peak ground reaction forces were significantly different between the three jumping protocols (p < 0.001), increasing from AGJ (14 N/kg) to SJS (22 N/kg) to EGJ (29 N/kg) but were similar in RUN (22 N/kg) compared to SJS. The serum COMP concentration was increased (p < 0.001) immediately after all loading protocols, and then decreased (p < 0.001) at 30 min post-exercise compared to immediately after the exercise. Jumping and running under Earth gravity (EGJ and RUN) resulted in a significantly higher (p < 0.05) increase of serum COMP levels 30 min after impact loading compared to the impact loading under artificial gravity (RUN +30%, EGJ +20%, AGJ +17%, and SJS +13% compared to baseline). In conclusion, both the amplitude and the number of the impacts contribute to inducing higher COMP responses and are therefore likely important factors affecting cartilage metabolism. RUN had the largest effect on serum COMP concentration, presumably due to the high number of impacts, which was 10 times higher than for the jump modalities. Future studies should aim at establishing a dose-response relationship for different types of exercise using comparable amounts of impacts. [ABSTRACT FROM AUTHOR]

Based on the Onsager Equation, a linearized sixth-order partial differential equation describing the flow in the volume of the rotor of a gas centrifuge is solved using a finite element algorithm employed by the CurvSOL code. The results are compared to those from Pancake, an existing code that uses eigenfunction expansion to solve the Onsager equation. Excellent agreement is demonstrated between the solutions of the wall temperature gradient and scoop drive mechanisms for both the Rome and Iguaçu centrifuge designs. Results suggest rotor speed and radius play key roles in the influence of wall curvature on the flow solution. [ABSTRACT FROM AUTHOR]

In the nuclear reprocessing plant, after the dissolution of spent fuel, high-speed tubular bowl sedimentation centrifuge is being used to remove the solid particles from the solvent. The performance of the system and extent of clarification of the solvent is ascertained in the chemical laboratory by drawing the sample. A noninvasive methodology, the laser obscuration, is studied for its adaptability as an online measurement tool for determination of clarification status. This would help to manipulate the operation of the centrifuge to achieve desired separation efficiency with minimum time and without interruption. In this context, the performance evaluation of a uniquely designed high-speed tubular centrifuge for reprocessing of fast reactor fuel has been carried out by using laser obscuration method. The light scattering technique has been widely used for the determination of concentration of clarification liquid. In addition, the size distribution is also ascertained in our study, which is useful to determine the grade efficiency of centrifuge system. Two different particulate liquid suspensions namely ferric oxide (Fe2O3) and zirconium molybdate suspended in de-ionized water are used. The tubular bowl centrifuge is tested at the high-speed rotation of the inner bowl (14000–20000 rpm), various throughput of clarifier liquid (30–470 lph) and in half-loaded bowl condition. The laser obscuration method is found to be useful for ascertaining the performance of the centrifuge system and it is recommended as an online tool for monitoring and maintaining separation efficiency by adjusting rotational speed, throughput and to monitor the bowl-loading condition. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Medical Equipment Journal is the property of Chinese Medical Equipment Journal Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Numerical simulation of the centrifuge experiment with dynamic loading on a small scale circular tunnel model surrounded by dry Buzzard sand is being presented. Considering soil dynamic behaviour properly, analyses were performed using an advanced hypoplastic constitutive model for sands considering the intergranular strain. The results include: settlement, lining forces time histories and peak acceleration in normalized model depth, were in good agreement with experimental data. Additional numerical modelling have been performed using hardening soil model with small-strain stiffness (HSS) and Mohr–Coulomb criteria (MC), then the results compared in detail with the hypoplastic (HP) model. The finite element predictions of settlement time histories and the internal forces mobilized in the tunnel lining were compared and the results declared that although settlements were underestimated by all models, HP has shown better responses in following the experimental trend. Also, internal forces obtained by the HP model showed smaller reversible variations. [ABSTRACT FROM AUTHOR]

Three centrifuge model tests were conducted on geosynthetic-reinforced pile-supported (GRPS) embankments with side slopes to investigate the influence of pile end-bearing conditions and pile modulus on their performance. This study found that when end-bearing piles were used, differential settlement occurred at the base of the embankment and the majority of the embankment load was transferred to the piles. Floating piles, however, behaved as rigid inclusions and formed a composite foundation with their surrounding soil, which shared the total load under an approximately equal-strain condition. The use of end-bearing piles with low modulus increased the total settlement of the piles and the foundation soil at the base of the embankment and promoted lateral movement of the side slopes. Two theoretical methods were adopted with some modifications to calculate pile head settlement compared with the measured data. When the end-bearing piles were used to support the geosynthetic-reinforced embankment, the modified Vesic method considering negative skin friction along pile shafts was used to calculate the pile head settlement close to the measured one. When floating piles were used to support the geosynthetic-reinforced embankment, the modified equivalent footing method was used to calculate the settlement, matching reasonably well with the measured one. [ABSTRACT FROM AUTHOR]

This paper highlights the beneficial usage of Combined Pile-Raft Foundation (CPRF) over conventional pile group foundation subjected to seismic loading in liquefiable soil. Firstly, asingle pileresting on a liquefiable soil is numerically modelled and subsequently validated with available dynamic centrifuge test result by using finite difference based computer programme, FLAC3D.Thereafter, the model is extended for simulatingCPRF and pile group. Further parametric studies areperformed to understand the effect of pile spacing (s), pile length (l) and different seismic motions on the behaviour of CPRF and pile group. Results are presented in terms of normalised bending moment (M/Mmax), shear forces and pore water pressure (PWP) ratio. Increase in shear resistances in the range of (35 - 60)% and (40 - 70)% are observed for the piles in CPRF over the conventional pile group foundation, having a pile spacing of 2 to 5 times of its diameter (d) and the (l/d) of 14 to 20, respectively. These outcomes portray the advantages of employing CPRF over pile group founded in liquefiable area under seismic loading. [ABSTRACT FROM AUTHOR]

Copyright of Computer Measurement & Control is the property of Magazine Agency of Computer Measurement & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The development of a continuous process for the separation of solvent‐diluted bitumen from mineral particles is an important step for the development of solvent‐based extraction technology of bitumen from mined oil sands. In this work, a custom‐made conical filtering centrifuge is used to separate toluene‐diluted bitumen from oil sand mineral particles. Compositions of wet granular samples are analyzed before and after centrifugation for three different oil sand ores. Results suggest that conical filtering centrifuges could be used for continuous separation of solvent‐diluted bitumen from oil sand ores with relatively coarse particles. [ABSTRACT FROM AUTHOR]

This paper presents a software for a centrifuge-based flight simulator designed for training pilots in manually controlled aerospace flights with a broad range of overloads. Dynamic simulation algorithms of an aerospace flight were developed. A special technique of maximin testing of the stabilization accuracy is proposed for manned flights performed under extreme conditions. [ABSTRACT FROM AUTHOR]

During the Great East Japan Earthquake and Tsunami of 2011, enormous coastal levees collapsed as a result of tsunami overflows. Concrete-covered levees, where concrete blocks are used to protect levees made of soil, showed a specific failure mode in which back slope blocks and internal soils were dislodged. Although several hydraulic experiments have been conducted in an attempt to understand the failure mechanism, the complexity of the failure requires that both hydro-dynamical and geotechnical points of view be taken into account for a deeper understanding. This study uses a centrifuge to identify the failure behavior of levees from those points of view. The centrifuge can reproduce the stress, water pressure, and overflow velocity of the prototype-scale ground. Overflowing at sufficient time periods was produced in the centrifuge by generating differences in water height for seaside and landside areas. The test results showed that the levees collapsed due to a combination of the effect of water flow on the back slope and seepage inside the levees. In addition, the effectiveness of several proposed countermeasures for preventing collapse was confirmed. [ABSTRACT FROM AUTHOR]

Several techniques have been developed in order to mitigate damage to buildings during and after liquefaction events. Benefits of using vertical drains have been verified by analysing their performance in the soil and evaluating their effectiveness in dissipation of excess pore pressures generated by the earthquake. However, the effect of drains in the soil below structures requires further investigation. In this paper, a dynamic centrifuge test series was carried out to evaluate the performance of a vertical drains arrangement below shallow foundations. High permeable rubble brick was used as coarse material inside the drains to provide positive results not only from a geotechnical point of view but also from an environmental and sustainable perspective. The behaviour of drains was analysed when they are located under shallow foundations of a building, in terms of the excess pore pressures generated during the earthquake and subsequent post-seismic dissipation, the foundation settlement and its dynamic response. [ABSTRACT FROM AUTHOR]

In addition to inducing uncertainty in the predicted response, natural spatial variability of soil properties affects the mechanical response of geotechnical structures. When a failure surface is involved in the response, this surface can deviate from its theoretical location to pass through weaker zones of material. For the case of seismically induced soil liquefaction, it has been found that a larger amount of excess pore water pressure is generated in a soil exhibiting small-scale variability of its properties than in the corresponding uniform soil having geomechanical properties equal to the average properties of the heterogeneous soil. An explanation for this important phenomenon is provided in this paper based on the results of centrifuge experiments and numerical simulations of heterogeneous and homogeneous saturated soil deposits subjected to seismic loads. It is demonstrated, based on a detailed analysis of the results, that partial drainage during the earthquake, consisting of pore water inflow from loose soil zones that liquefy first toward surrounding dense areas, may trigger softening of dilative soils. The water inflow effects in terms of volumetric strains leading to reduced cyclic resistance of dense sands are compared with results of specially designed cyclic triaxial tests reported by other researchers. • Spatially variable soils have lower liquefaction resistance than uniform soils. • Centrifuge experiments and finite element analyses are used in this study. • The results confirm the conclusions of specially designed cyclic laboratory tests. • Partial drainage during "undrained" cyclic loading may lead to soil softening. [ABSTRACT FROM AUTHOR]

Monotonic, static beam on nonlinear Winkler foundation (BNWF) methods are used to analyze a suite of dynamic centrifuge model tests involving pile group foundations embedded in a mildly sloping soil profile that develops liquefaction-induced lateral spreading during earthquake shaking. A single set of recommended design guidelines was used for a baseline set of analyses. When lateral spreading demands were modeled by imposing free-field soil displacements to the free ends of the soil springs (BNWF_SD), bending moments were predicted within −8% to +69 16th to 84th percentile values and pile cap displacements were predicted within −6 to +38%, with the accuracy being similar for small, medium, and large motions. When lateral spreading demands were modeled by imposing limit pressures directly to the pile nodes (BNWF_LP), bending moments and cap displacements were greatly overpredicted for small and medium motions where the lateral spreading displacements were not large enough to mobilize limit pressures, and pile cap displacements were greatly underpredicted for large motions. The effects of various parameter relations and alternative design guidelines on the accuracy of the BNWF analyses were evaluated. Sources of bias and dispersion in the BNWF predictions and the issues of greatest importance to foundation performance are discussed. The results of these comparisons indicate that certain guidelines and assumptions that are common in engineering design can produce significantly conservative or unconservative BNWF predictions, whereas the guidelines recommended herein can produce reasonably accurate predictions.

Eight dynamic model tests were performed on a 9 m radius centrifuge to study the behavior of single piles and pile groups in liquefiable and laterally spreading ground. Pile diameters ranged from 0.36 to 1.45 m for single piles, and from 0.73 to 1.17 m for pile groups. The soil profile consisted of a gently sloping nonliquefied crust over liquefiable loose sand over dense sand. Each model was tested with a series of realistic earthquake motions with peak base accelerations ranging from 0.13 g to 1.00 g. Representative data that characterize the important aspects of soil-pile interaction in liquefiable ground are presented. Dynamic soil-pile and soil-pile cap forces are backcalculated. Directions of lateral loading from the different soil layers are shown to depend on the mode of pile deflection relative to the soil, which depends on the deformed shape of the soil profile, the pile foundation stiffness, and the magnitude of loads imposed by the nonliquefied crust. Procedures for estimating the total horizontal loads on embedded piles and pile caps (i.e., passive loads plus friction along the base and sides) are evaluated. Due to liquefaction of the sand layer beneath the crust, the relative displacement between the pile cap and free-field crust required to mobilize the peak horizontal loads is much larger than expected based on static pile cap load tests in nonliquefied soils. Journal of Geotechnical and Geoenvironmental Engineering © ASCE.

Danger to rubber trees (Hevea brasiliensis) from South American leaf blight fungus imperils the world’s source of natural latex for essential rubber products. Avoiding latex allergies also requires a non-Hevea latex source. The present methods for removing latex entrapped in the individual cells of guayule plants require environmentally hazardous chemicals. This study proposes a new method for latex extraction from guayule using various ionic liquids (ILs) to dissolve cell walls and release latex, as substantiated by Fourier transform infrared spectroscopy (FTIR) data.

The physical modelling of subsoil behaviour and soil-structure interaction is essential for the proper design of offshore structures and port infrastructure. A brief introduction to such modelling of geoengineering problems is presented and some methods and experimental devices are described. The relationships between modelling scales are given. Some examples of penetration testing results in centrifuge and calibration chamber are presented. Prospects for physical modelling in geotechnics are also described.

During laboratory assessment of the soil water characteristic curve (SWCC), determining equilibrium at various pressures is challenging. This study establishes a methodological framework to identify appropriate experimental duration at each pressure step for the construction of SWCCs via centrifugation. Three common temporal approaches to equilibrium – 24-, 48- and 72-h – are examined, for a grassland and arable soil. The framework highlights the differences in equilibrium duration between the two soils. For both soils, the 24-h treatment significantly overestimated saturation. For the arable site, no significant difference was observed between the 48- and 72-h treatments. Hence, a 48-h treatment was sufficient to determine ‘effective equilibrium’. For the grassland site, the 48- and 72-h treatments differed significantly. This highlights that a more prolonged duration is necessary for some soils to conclusively determine that effective equilibrium has been reached. This framework can be applied to other soils to determine the optimum centrifuge durations for SWCC construction.

Study of boulder transport by tsunamis is challenging because boulder size, shape, and composition vary greatly; furthermore, flow conditions, topography, and initial conditions are generally unknown. To investigate the mechanism of boulder pickup, experiments of tsunami-like flow past spherical boulders partially buried in a sediment bed are conducted. The experiments are performed in a large centrifuge facility to reduce scale effects and the corresponding dynamic similitude is discussed. The traditional approach to determine boulder pickup is adapted for the case of a half-buried spherical boulder. The adapted model predicts that the boulders are transported, but does not accurately predict the timing of pick up. To investigate the difference in pickup timing, two physical phenomena are discussed: pore-water-pressure dissipation in the soil, and the impact of the free-surface flow on hydrodynamic forces. For a spherical shaped boulder, vertical forces (i.e. buoyant and lift forces) are critical for the initiation of boulder pickup. It was found that spherical boulders that are three-quarter buried in the soil are not transported, even when exposed to flow conditions that would otherwise predict transport. [ABSTRACT FROM AUTHOR]

Liquid degassing takes place in several space processes (cooling and lubrication of hardware, combustion of liquid propellants etc.) during launching and re-orbiting of rockets and workstations. The present work studies the effect of hypergravity acceleration on the two phase flow that is developed during the degassing of a liquid jet. Liquid is initially saturated with dissolved gas at 200 kPa and 400 kPa and is then injected at the bottom of a liquid column having its top open to atmospheric pressure. Due to the sudden decompression inside the column, the liquid jet becomes supersaturated with dissolved gas, thus triggering the formation of degassing bubbles within its volume. The local liquid flow pattern inside the column is tracked by recording the motion of bubbles. Experiments are conducted at 1 g, 2 g and 8 g accelerations, using the Large Diameter Centrifuge (LDC) facility of the Technology Center (ESTEC) of the European Space Agency (ESA). The liquid flow behavior registered at varying hypergavity conditions is quite interesting. For an injection pressure of 200 kPa the liquid velocity magnitude increases with acceleration level possibly because of the inertial shear force. Increasing the injection pressure to 400 kPa, not only the magnitude, but also the direction of liquid velocity varies possibly due to the larger effect of Coriolis force induced by the increased liquid velocities. [ABSTRACT FROM AUTHOR]

Particle resuspension has been recognized as a secondary source of indoor air pollution by many field studies. However, some laboratory studies showed that the air velocities or force fields required to resuspend aerosol particles are very high that rarely occurred in indoor environments. In fact, the surfaces used in these studies were treated to ensure cleanliness, but in reality, dusty surfaces are ubiquitous in our daily life. This work aims to investigate the effect of dust on a surface on resuspension of a coarse particle (polyethylene) by a centrifugal method. Dusty surfaces with different loadings were made by gravitational settling of Arizona test dust on a clean poly(methyl methacrylate) substrate inside a deposition chamber. The resuspension of dust particles was first investigated, and it was found that dust particles were resuspended by two stages with different rates of resuspension. For the resuspension of the particles on the dusty surface, the remaining fraction of the polyethylene particles decreased with increasing force field and dust loading. Dust could greatly reduce the adhesion of the particles from one to two orders of magnitude depending on loadings. This gives an explanation to the discrepancy between the field and the laboratory studies. [ABSTRACT FROM AUTHOR]

The results of the study of the adhesion properties of recycling greases expressed in terms of the residual amount of grease that is stored on a metal plate after testing in a laboratory centrifuge are presented. It was established that the investigated samples of recycling greases in the range of the thickness of the deposition layer up to 1.0 mm, by their adhesion properties, are fully suitable for using in all types of bearings operated with a rotation speed of up to 2500 rpm. From the number of investigated grease samples, samples with a deposition layer thickness of 0.1 mm o have evidence of fairly high values of the rotational speed when the threshold value of the residual amount of grease is reached. [ABSTRACT FROM AUTHOR]

• The Gongbei tunnel with area of 336.9 m2 and cover depth ratio of 0.25 is introduced. • The large size tunnel is excavated in multi steps under the support of frozen pipe ring. • A series of centrifuge tests are conducted to simulate tunnel excavation. • Tunnelling-induced ground movement and structural responses are investigated. This paper reports on a series of centrifuge model tests to investigate the ground and structural response of tunnel linings, pipe ring roof and pile foundation induced by a shallow and large section tunnel supported by a roof formed of a ring of jacked pipes pre-installed before the excavation. The prototype is the Gongbei tunnel which has a cross sectional area of 336.9 m2 and is 5 m below the busy Gongbei port and 0.5 m away from the pile foundations of a port building. The pipe ring, tunnel lining, temporary struts, a single pile are simulated in the model with similarity laws under an 80g acceleration. The tunnelling process is modelled by the staged in-flight drainage of pre-injected liquid bags inserted in between model pipe ring and lining. The tested soil mass has dimensions of 900 × 700 × 250 mm3 (width × depth × length) and comprises a homogeneous remoulded soft clay extracted from the Gongbei site and consolidated by the in-flight operation. Four test scenarios were conducted to investigate the effects of a nearby pile, drained liquid volume (representing volume loss) and the pre-installed pipe ring on the ground settlement and structural response of the tunnel linings and pile foundation. Test results indicate that the settlement trough is asymmetrically distributed along the tunnel axis due to the asymmetrical excavation sequences. The ground settlement above the tunnel axis varies almost linearly with the distance to centre of the excavation step. The pile near the tunnel tends to reduce ground settlement. The increase of drained liquid volume will produce significant increases of maximum ground settlement and pile settlement. Similar findings were also found for the case of failure of the frozen pipe ring, but the effect of a nearby pile is not as much as those effects of volume loss and pipe ring. [ABSTRACT FROM AUTHOR]

INTRODUCTION: High-gravity (G) training is used to educate trainee pilots about anti-G straining maneuvers (AGSM) in an environment similar to that of a real fighter aircraft, and to enhance their G tolerance. The success or failure of high-G training could be multifactorial, but most previous studies have only focused on the effect of pilots' physical condition. METHODS: A total of 138 male trainee pilots participated in this study. All trainee pilots had received AGSM training from experienced instructors and then underwent centrifuge high-G training. Participants completed questionnaire surveys about body size, lifestyle, self-reported AGSM proficiency, resilience (Connor-Davidson Resilience Scale, CD-RISC), and depression level (Center for Epidemiologic Studies Depression Scale, CES-D). RESULTS: Of the 138 subjects, 100 (72.5%) successfully completed high-G training without experiencing G-induced loss of consciousness (G-LOC) within two trials; these were allocated to the success group. The remaining 38 (27.5%) subjects who completed the training after three or more attempts, or who failed to complete the training at all, were allocated to the failure group. Multivariate analyses revealed that the success of centrifuge training was positively associated with age and self-reported AGSM proficiency, and negatively associated with depression level. DISCUSSION: The success of high-G training was significantly associated with self-reported AGSM proficiency and depression level. Instructors should emphasize the importance of AGSM proficiency and offer practice-based learning to trainee pilots. In addition, they should pay attention to not only trainee pilots'physical condition, but also their psychological status. [ABSTRACT FROM AUTHOR]