A new multi-residue method based on solid-phase extraction (SPE) with centrifugation was developed for determination and quantitation of 67 pesticides in water samples. Two SPE cartridges were tested: Chromabond C18 a...A new multi-residue method based on solid-phase extraction (SPE) with centrifugation was developed for determination and quantitation of 67 pesticides in water samples. Two SPE cartridges were tested: Chromabond C18 and Oasis HLB. Parameters that influence the extraction efficiency such as the eluent volume, the sample loading volume, the addition of organic solvent to water sample, sorbent drying and elute concentration were optimized. The innovation of this work was the examination of the use of a centrifugation technique in both the drying and elution steps. When combined with centrifugation, the volume of the elution solvent was reduced to 2 mL and the time for sorbent drying decreased also to 10 min under vacuum. Under the optimized conditions, this method showed good recoveries higher than 65% - 68% for the 67 analyzed pesticides using the C18 and HLB cartridges with relative standard deviations lower than 9.7% - 12.3%. Limits of quantification were between 2 and 20 ng.L–1. The simplicity of the described method, use of less of organic solvent, short procedure time, and good recoveries demonstrate the advantages of this environmentally friendly approach for routine analysis of numerous samples.展开更多
Circulating microRNAs are robustly present in plasma or serum and have become a research focus as biomarkers for tumor diagnosis and prognosis.Centrifugation is a necessary procedure for obtaining highquality blood su...Circulating microRNAs are robustly present in plasma or serum and have become a research focus as biomarkers for tumor diagnosis and prognosis.Centrifugation is a necessary procedure for obtaining highquality blood supernatant.Herein,we investigated one-step and two-step centrifugations,two centrifugal methods routinely used in microRNA study,to explore their effects on plasma microRNA quantification.The microRNAs obtained from one-step and two-step centrifugations were quantified by microarray and TaqMan-based real-time quantitative polymerase chain reaction(Q-PCR).Dynamic light scattering was performed to explore the difference underlying the two centrifugal methods.The results from the microarray containing 1,347 microRNAs showed that the signal detection rate was greatly decreased in the plasma sample prepared by two-step centrifugation.More importantly,the microRNAs missing in this plasma sample could be recovered and detected in the precipitate generated from the second centrifugation.Consistent with the results from microarray,a marked decrease of three representative microRNAs in twostep centrifugal plasma was validated by Q-PCR.According to the size distribution of all nanoparticles in plasma,there were fewer nanoparticles with size>1,000 nm in two-step centrifugal plasma.Our experiments directly demonstrated that different centrifugation methods produced distinct quantities of plasma microRNAs.Thus,exosomes or protein complexes containing microRNAs may be involved in large nanoparticle formation and may be precipitated after two-step centrifugation.Our results remind us that sample processing methods should be first considered in conducting research.展开更多
This study used specularite, a high-gradient magnetic separation concentrate, as a raw material in reverse flotation.An iron concentrate with a grade of 65.1 wt% and a recovery rate of 75.31% were obtained.A centrifug...This study used specularite, a high-gradient magnetic separation concentrate, as a raw material in reverse flotation.An iron concentrate with a grade of 65.1 wt% and a recovery rate of 75.31% were obtained.A centrifugal concentrator served as the deep purification equipment for the preparation of iron oxide red pigments, and its optimal rotating drum speed, feed concentration, and other conditions were determined.Under optimal conditions, a high-purity iron oxide concentrate with a grade of 69.38 wt% and a recovery rate of 80.89% were obtained and used as a raw material for preparing iron oxide red pigment.Calcining with sulfuric acid produced iron red pigments with different hues.Simultaneously, middlings with a grade of 60.20 wt% and a recovery rate of 17.51% were obtained and could be used in blast furnace ironmaking.High-value utilization of specularite beneficiation products was thus achieved.展开更多
A total of 18 ejaculates were collected, once per week, from six fertile stallions for three consecutive weeks in October and November, to compare motility over time between extenders using four semen processing treat...A total of 18 ejaculates were collected, once per week, from six fertile stallions for three consecutive weeks in October and November, to compare motility over time between extenders using four semen processing treatments. Four total aliquots of semen were used. Two aliquots of each semen collection were extended in either INRA96 or an experimental proprietary milk-based extender Walworth （WW） extender, and each was designed for multi-day storage of fresh chilled semen. Each aliquot was divided again, and either centrifuged at 600 μg for 10 min without cushion, or not centrifuged and extended to a final concentration of 25 × 10^6 spermatozoa/mL. The treatments evaluated were INRA96 without centrifugation （INRA-NC） or with centrifugation （INRA-C）, and Walworth extender without centrifugation （WW-NC） or with centrifugation （WW-C）. Total and progressive motility were measured using Sperm Vision~ CASA at 0, 24, 48 and 72 h post-collection. Samples were stored at 4 ℃. No differences were found between extenders in progressive （P = 0.13） or total motility （P = 0.14） over the four different time points without centrifugation. However, ejaculates processed in INRA-C group had the greater total and progressive motility （P 〈 0.05） over the four time points than ejaculates in the WW-C group. It was found that centrifugation and re-suspension of stallion semen in INRA96 improved the longevity of fresh chilled semen. However, when not using centrifugation, the Walworth extender proved to be as effective for maintaining spermatozoa motility across all time points as 1NRA96 , and may be an alternative for use in the equine breeding industry.展开更多
We investigated whether an ordinary centrifuge can achieve the standard centrifugal effect required according to specifications for infectious disease screening using the Abbott i2000.Samples were collected and centri...We investigated whether an ordinary centrifuge can achieve the standard centrifugal effect required according to specifications for infectious disease screening using the Abbott i2000.Samples were collected and centrifuged following a standard operating procedure(SOP).They were then divided into three groups according to the results of the initial screening tests:a negative group,weak-positive group,and positive group.Twenty negative samples and all weak-positive and positive samples were re-analyzed.Two tubes for each re-analyzed sample were centrifuged simultaneously,one for 10 min at 10000x g,per recommendations,and one for 10 min at 2750^g.No significant difference was found between the groups using different centrifugal forces.There was a strong correlation in the quantitative values between the two conditions of centrifugation.Consistency analysis showed a Cronbach's alpha>0.8 for detection of Treponema pallidum,human immunodeficiency virus(HIV),hepatitis C virus(HCV),and hepatitis B surface antigen in the three groups(negative group,weak-positive group,and positive group)under different centrifugation conditions.Strong consistency was found under different centrifugal conditions,regardless of the initial testing results.In conclusion,we conducted centrifugation steps in duplicate,according to infectious disease screening protocols.Our study showed that all samples should be centrifuged using a recommended relative centrifugal force after a proper clotting time,as in the standard operating procedure of our laboratory.In this way,we were able to obtain the same results using an ordinary centrifuge as those obtained using a high-speed centrifuge,such as the Abbott i2000.展开更多
In the present paper we have observed the effect of discontinuous gradient two-step Percoll centrifugation on depleting mature T lymphocytes from normal bone marrow. The pre-/post-Percoll percentage of CD34+, and Leu4...In the present paper we have observed the effect of discontinuous gradient two-step Percoll centrifugation on depleting mature T lymphocytes from normal bone marrow. The pre-/post-Percoll percentage of CD34+, and Leu4+ cells in MNC was counted by using APAAP technique. As the two-step Percoll centrifugation is simple,and time saving, and decreases the incidence of contamination of cultured cells as well,This technique may be of value in serum-free culture of hematopoietic cells and immunological studies.展开更多
Background： Density gradient centrifugation was reported as a technique of semen preparation in assisted reproductive techniques in humans and animals. This technique was found to be efficient in improving semen qual...Background： Density gradient centrifugation was reported as a technique of semen preparation in assisted reproductive techniques in humans and animals. This technique was found to be efficient in improving semen quality after harmful techniques such as cryopreservation. Recently a modified technique, single layer centrifugation,was proposed as a technique providing a large amount of high quality spermatozoa, and this treatment was performed before conservation. Single layer centrifugation has been studied prevalently in stallions and in boars,but limited data were available for bulls. Occasionally bulls are known to experience a transient reduction in semen quality, thus techniques that allow improvement in semen quality could be applied in this context. The aim of this study was the evaluation of single layer and double layer centrifugation by the use of iodixanol, compared with conventional centrifugation and non-centrifuged semen, on the sperm characteristics during the cryopreservation process in bulls with normal and poor semen quality.Results： Single layer centrifugation and double layer centrifugation both significantly increased the percentage of normal spermatozoa and decreased the percentage of non-sperm cells in poor quality samples, while both were ineffective in those of normal quality. Sperm characteristics in poor quality samples increased after single layer centrifugation and double layer centrifugation, reaching values similar to those recorded in normal samples, and this trend is maintained after equilibration and after cryopreservation. On the other hand, SLC and DLC resulted in a consistent reduction in the spermatozoa recovered, and this resulted in a reduction of the absolute amount of spermatozoa cryopreserved in the normal samples, without a clear improvement in sperm characteristics in this type of sample.Conclusions： These data suggested that both SLC and DLC could be performed in practice, but their application should be limited to the cases in which the quality of the spermatozoa recovered is more important than the total amount of spermatozoa.展开更多
Background： Direct ZN （Ziehl-Neelsen） sputum smear microscopy for diagnosis of TB （tuberculosis） has low sensitivity, especially in TB/HIV co-infected patients. Sputum concentration by bleach （NaOCI） with sedim...Background： Direct ZN （Ziehl-Neelsen） sputum smear microscopy for diagnosis of TB （tuberculosis） has low sensitivity, especially in TB/HIV co-infected patients. Sputum concentration by bleach （NaOCI） with sedimentation has been used to increase the sensitivity of sputum smear microscopy in many settings but with varying results. Objective： To determine whether bleach plus centrifugation significantly improves the detection of AFB （acid-fast bacilli） in ZN smear-negative sputum specimens. Methods： Three hundred and seventy sputum specimens were collected from new TB suspects attending a Nairobi referral district hospital and processed for direct microscopy using ZN technique and culture on Lowenstein Jensen Media. All smear-negative specimens were treated with 3.5% bleach and left to stand for 30 min before centrifugation. The bleach treated smears were processed and examined using ZN technique. Results： Of the 370 specimens, 200 （54%） were positive culture. The number of sputum samples that were smear-positive by direct ZN was 138 （37.2%）, with a sensitivity of 66%. After treatment of direct ZN smear-negative specimens with 3.5% bleach and centrifugation, the total number of AFB smear-positive samples increased to 171 with an increase in sensitivity of 66% to 81.1% （15.1%）. Conclusion： In this study, bleach with centrifugation significantly increased the yield of sputum smear microscopy. Further evaluation of these techniques in routine programmes is required especially in settings where the burden of TB/HIV is high.展开更多
The study aimed to investigate the effects of centrifugation of stallion semen on progressive sperm motility over a 72-hour period;and determine if the protein marker,precursor of A-kinase anchor protein 4(pro-AKAP4),...The study aimed to investigate the effects of centrifugation of stallion semen on progressive sperm motility over a 72-hour period;and determine if the protein marker,precursor of A-kinase anchor protein 4(pro-AKAP4),may be maintained at a higher level over time when compared to non-centrifuged samples.Pro-AKAP4 has been studied for its function in stabilizing the structure of spermatozoa and its use as a marker for fertilizing capacity of spermatozoa.Semen collections were obtained from four fertile,commercially used Standardbred stallions collected three times each.Semen samples were diluted to a final concentration of 50 million total cells per milliliter.One extended aliquot of semen from each collection was used for the non-centrifuged treatment,and one extended aliquot of semen was centrifuged at 750×g for 10 min.The supernatant from the centrifuged sample was then removed with a 10 mL plastic transfer pipette,and the spermatozoa cell pellet was suspended in fresh extender to a final concentration of 50 million total cells per milliliter.Both centrifuged and non-centrifuged samples from each collection were stored in Equine Express II stallion semen shipping containers for 72 h and fresh ice packs were added to each container every 24 h.Both progressive sperm motility and levels of pro-AKAP4 were determined at times 0,12,24,48 and 72 h after collection.Differences were found between stallions,times and treatments with the main finding being that pro-AKAP4 concentration in centrifuged samples was maintained at a much higher level over the 72-hour period studied.展开更多
Objective:Sperm preparation techniques and cryopreservation are widely used in assisted reproductive techniques(ART).How to improve the quality of sperm management is a matter of great concern.Phospholipase C-zeta(PLC...Objective:Sperm preparation techniques and cryopreservation are widely used in assisted reproductive techniques(ART).How to improve the quality of sperm management is a matter of great concern.Phospholipase C-zeta(PLCζ)is considered a sperm-specific agent that activates oocyte activation and thus playing a crucial role in male fertility.However,the potential mechanisms by which semen processing and cryopreservation on PLCζcontribute to keyhole have not been addressed.Methods:In this study,semen samples were taken from have not been addressed 10 normozoospermic men.Each semen sample was assigned to the following groups:density gradient centrifugation(DGC)as control,microfluidic sorting,and cryopreservation.Sperm parameters of molity,viability,membrane integrity,and intracellular ROS were evaluated during sperm preparation and cryopreservation.The expression of PLCζin human sperm was determined by immunofluorescence and western blotting.Results:The results showed that molity,viability,and membrane integrity decreased in cryopreservation group.Intracellular ROS were also significantly increased compared to the the control group.There was no significant difference between DGC and microfluidic sorting group.Our investigation revealed that total levels of PLCζwere comparable between DGC and microfluidic sorting,but there were significantly reduced levels of PLCζafter cryopreservation as quantified by both immunofluorescenceand immunoblotting.PLCζimmunofluorescence in sperm revealed different PLCζlocalization patterns around the acrosomal(Ac),equatorial(Eq),post-acrosomal(PA)areas of sperm heads,and their combination.The predominant patterns of PLCζlocalization in DGC were similar to that of microfluidic sorting,with strong,with staining.In contrast,PLCζstaining in freeze-thawed sperm was considerably weaker fluorescence intensity.Conclusion:This study clarified the mechanism of sperm preparation and cryopreservation underlying effect on sperm characteristic,accompanied with PLCζexpresion.We demonstrated that microfluidic sorting provides a highly efficient preparation method for clinical selection of PLCζ-expressing sperm comparable to DGC gene expression.It is suggested that the cryopreservation of sperm has a significant detrimental effect on PLCζ.展开更多
In Brayton cycle energy storage systems powered by supercritical carbon dioxide(sCO_(2)),compressors are among themost critical components.Understanding their internal flowloss characteristics is,therefore,essential f...In Brayton cycle energy storage systems powered by supercritical carbon dioxide(sCO_(2)),compressors are among themost critical components.Understanding their internal flowloss characteristics is,therefore,essential for enhancing the performance of such systems.This study examines the main sCO_(2) compressor from Sandia Laboratory,utilizing entropy production theory to elucidate the sources and distribution of energy losses both across the entire machine and within its key flow components.The findings reveal that turbulent viscous dissipation is the predominant contributor to total entropy production.Interestingly,while the relative importance of the entropy produced by various sources as the mass flow rate rises remains essentially unchanged,the total entropy production exhibits a nonmonotonic trend,first decreasing and then increasing with the mass flow rate.High entropy production in the impeller is primarily concentrated in the clearance region and along the rear cover of the impeller tip.In the diffuser,it is most pronounced on the front and rear plates and within the central flow path.Meanwhile,in the volute,the highest entropy production occurs around the diffuser outlet and along the outer region of the volute’s centerline.展开更多
Precast driven piles are extensively used for infrastructure on soft soils,but the buildup of excess pore water pressure associated with pile driving is a challenging issue.The process of soil consolidation could take...Precast driven piles are extensively used for infrastructure on soft soils,but the buildup of excess pore water pressure associated with pile driving is a challenging issue.The process of soil consolidation could take several months.Measures are sought to shorten the drainage path in the ground,and permeable pipe pile is a concept that involves drainage channels at the peak pore pressure locations around the pile circumference.Centrifuge tests were conducted to understand the responses of permeable pipe pile treated ground,experiencing the whole pile driving,soil consolidating,and axially loading process.Results show that the dissipation rate of pore pressures can be improved,especially at a greater depth or at a shorter distance from the pile,since the local hydraulic gradient was higher.Less significant buildup of pore pressures can be anticipated with the use of permeable pipe pile.For this,the bearing capacity of composite foundation with permeable pipe pile can be increased by over 36.9%,compared to the case with normal pipe pile at a specific time period.All these demonstrate the ability of permeable pipe pile in accelerating the consolidation process,mobilizing the bearing capacity of treated ground at an early stage,and minimizing the set-up effect.展开更多
DNA origami technique, a breakthrough in DNA nanotechnology, has been widely used to prepare complex DNA nanostructures with nanoscale addressability. However, the purity and yield are generally the bottleneck to appl...DNA origami technique, a breakthrough in DNA nanotechnology, has been widely used to prepare complex DNA nanostructures with nanoscale addressability. However, the purity and yield are generally the bottleneck to application of DNA nanostructures, and current methods for purifying DNA origami nanostructures in large quantities are time-consuming and laborious. This study aims to develop a scalable, cost-effective and contamination-free method of purifying DNA origami nanostructures. We employ an effective and convenient purification approach to purify planar rectangle DNA origami structures through rate-zonal centrifugation. By subjecting DNA origami samples to high centrifugal force in a density gradient media of glycerol, well-folded nanostructures and by-products are separated successfully, which are confirmed by agarose gel electrophoresis and atomic force microscopy(AFM). This method will aid the production of pure rectangle DNA origami nanostructures in large quantity.展开更多
A significant number of stallions produce low quality ejaculates with high sensibility to chilling. Single Layer Centrifugation (SLC) with Andro-coll-ETM has been presented as an efficient method of selecting good qua...A significant number of stallions produce low quality ejaculates with high sensibility to chilling. Single Layer Centrifugation (SLC) with Andro-coll-ETM has been presented as an efficient method of selecting good quality spermatozoa. In the current study, changes in sperm quality (motility, viability, acrosome integrity and DNA damage) occurring during storage at 5?C for a maximum of 72 h, were investigated. For that, one ejaculate from 12 stallions was split in two aliquots: control and SLC-selected. Both aliquots were chilled and stored at 5?C and spermatozoa were evaluated for motility, viability and acrosome integrity at 24, 48 and 72 h post collection. DNA damage was evaluated at 48 h post collection using the comet assay. In the SLC-selected aliquots, there was a significant improvement in terms of progressive motility (0 h: P = 0.005;24 h: P 0.05). SLC with Androcoll-ETM improved semen quality prolonging sperm longevity of chilled semen (P = 0.012). This positive effect was more evident in ejaculates most sensitive to chilling that had a sharp decrease in motility in the first 24 h of refrigeration and for all ejaculates at 72 h post-chilling. Therefore, this method reveals to be a useful technique for selecting spermatozoa and maintain sperm quality during storage.展开更多
Cavitation is an unavoidable phenomenon in the operation of centrifugal pumps.Prolonged cavitation can cause significant damage to the components of the flow channel,and in severe cases,it may even interfere with the ...Cavitation is an unavoidable phenomenon in the operation of centrifugal pumps.Prolonged cavitation can cause significant damage to the components of the flow channel,and in severe cases,it may even interfere with the normal energy exchange processes within the pump.Therefore,effective monitoring of cavitation in centrifugal pumps is crucial.This article presents a study that approaches the issue from an acoustic perspective,using experimental methods to gather and analyze acoustic data at the inlet and outlet of centrifugal pumps across various flow rates,with hydrophones as the primary measuring instruments.Results show that flow rate significantly affects noise levels in both non-cavitation and mild cavitation stages,with noise increasing as the flow rate rises.As the cavitation margin(NPSHa)decreases,inlet and outlet noise trends diverge:inlet noise drops sharply,while outlet noise initially increases before sharply decreasing.Both exhibit a distinct zone of abrupt change,where NPSHa values offer earlier cavitation detection than traditional methods.The noise at the pump’s inlet and outlet primarily consists of discrete and broadband noise,with most energy concentrated at discrete frequencies—shaft frequency(24 Hz),blade frequency(144 Hz),and their harmonics.As NPSHa decreases,the inlet’s discrete and broadband noise frequencies decline,while they increase at the outlet.Monitoring changes in these spectrum characteristics provides an additional means of predicting cavitation onset.展开更多
A centrifugal pump with a specific speed ns=67 is considered in this study to investigate the impact of blade cutting(at the outlet edge)on the fluid-induced noise,while keeping all the other geometric parameters unch...A centrifugal pump with a specific speed ns=67 is considered in this study to investigate the impact of blade cutting(at the outlet edge)on the fluid-induced noise,while keeping all the other geometric parameters unchanged.The required unsteady numerical calculations are conducted by applying the RNG k-εturbulence model with the volute dipole being used as the sound source.The results indicate that the internal pressure energy of the centrifugal pump essentially depends on the blade passing frequency and its low-frequency harmonic frequency.Moreover,the pressure pulsation distribution directly affects the noise caused by the centrifugal pump.The sound pressure inside and outside the centrifugal pump and the sound power at the blade passing frequency gradually decrease increasing cutting distance of the impeller blades.When the cutting percentage is 1.21%,that is,the clearance ratio between impeller blade and tongue is 8.57%,the comprehensive performance of the centrifugal pump is the best.展开更多
With the development of urban infrastructure,it is inevitable that shield tunnels will undercross intercity railways.However,the safe operation of intercity railways requires strict subgrade deformation.On the basis o...With the development of urban infrastructure,it is inevitable that shield tunnels will undercross intercity railways.However,the safe operation of intercity railways requires strict subgrade deformation.On the basis of the engineering background of the Lianghu Tunnel in Wuhan,the three-dimensional centrifuge test and numerical back analysis were used to study the development of subgrade surface settlement during shield tunneling.A three-dimensional numerical model with the same size as the prototype was subsequently established to further study the settlement development and torsion behavior of the subgrade during tunnel excavation.The results show that the maximum settlement point of the transverse settlement trough gradually moves to the tunnel axis during tunnel excavation and that the entire subgrade experiences torsional deformation.Moreover,the effect of the intersection angle between the axes of the tunnel and the subgrade on the surface settlement of the subgrade was further studied.The results show that the intersection angle has no effect on the maximum settlement,but the width of the settlement trough increases gradually with increasing angle.Finally,on the basis of the soil arching effect caused by tunnel excavation,the subgrade settlement during tunnel excavation is reduced by reinforcing the soil in different zones of soil arching.The results show that the settlement of the subgrade caused by the shield tunnel can be effectively controlled by adding reinforcement directly to the top of the tunnel,and the maximum settlement of the subgrade surface is reduced from 24.41 mm to 9.47 mm,a reduction of approximately 61.2%.展开更多
Sand-bentonite(SB)cutoff walls are commonly used as barriers in polluted areas.The embedded part of an SB wall in an aquitard is crucial for its performance.In this study,a centrifuge modeling test was carried out to ...Sand-bentonite(SB)cutoff walls are commonly used as barriers in polluted areas.The embedded part of an SB wall in an aquitard is crucial for its performance.In this study,a centrifuge modeling test was carried out to investigate the effect of contact between the key and the aquitard on the migration behavior of contaminants within an SB cutoff wall.The centrifuge was accelerated to 100g(gravitational acceleration)and maintained in-flight for 36 h,equivalent to 41 years of transport time in the prototype.Results showed that the contaminant concentration within the SB wall was higher downstream than in the middle in the thickness direction,and deeper regions exhibited a greater concentration than shallower ones.This concentration distribution indicated that contaminants were transported along the interface between the SB wall and the aquitard,bypassing the base of the SB wall to reach the downstream aquifer rapidly.An improved numerical simulation considering preferential interface migration was performed,which agreed with the centrifuge test results.The simulation results indicated that preferential interface migration,as a defect,significantly accelerated the speed of contaminant migration,reducing the breakthrough time of the SB wall to 1/9 of that without preferential interface migration.展开更多
This study focused on the hydraulic conductivity of sand in centrifuge modeling.A self-designed temperature-controlled falling-head permeameter apparatus was used,and a series of falling-head seepage tests were perfor...This study focused on the hydraulic conductivity of sand in centrifuge modeling.A self-designed temperature-controlled falling-head permeameter apparatus was used,and a series of falling-head seepage tests were performed on sand samples with various porosities at different temperatures and centrifugal accelerations.The objectives were to qualitatively and quantitatively investigate the effects of temperature,porosity,and centrifugal acceleration on the hydraulic conductivity of sand and to study the applicability of the Kozeny-Carman equation for the centrifugal environment.Test results showed that in a similar temperature range and under the same porosity,the hydraulic conductivity of the sand is linearly correlated with centrifugal acceleration.When subjected to the same centrifugal acceleration and in a similar temperature range,the hydraulic conductivity of the sand exhibits an almost linear increase in relation to its porosity function(s^(3)/(1−s)^(2));the functional relationships between the hydraulic conductivity of the sand and temperature,centrifugal acceleration level,and porosity were established using two pathways.When the centrifugal acceleration is less than 50g,the Kozeny-Carman equation is effectively accurate in predicting the hydraulic conductivity of sand;however,when the centrifugal acceleration exceeds 50g,it is important to consider a significant error.展开更多
The primary goal of this study is to provide an efficient numerical tool to analyze the seismic performance of nailed walls.Modeling such excavation supports involves complexities due partly to the interaction of supp...The primary goal of this study is to provide an efficient numerical tool to analyze the seismic performance of nailed walls.Modeling such excavation supports involves complexities due partly to the interaction of support with soil and partly because of the amplification of seismic waves through an excavation wall.Consequently,innovative modeling is suggested herein,incorporating the calibration of the soil constitutive model in a targeted range of stress and strain,and the detection of a natural period of complex systems,including soil and structure,while benefiting from Rayleigh damping to filter unwanted noises.The numerical model was achieved by simulating a previous centrifuge test of the excavation wall,manifested at the pre-failure state.Notably,the calibration of the soil constitutive model through empirical relations,which replaces the numerical reproduction of an element test,more accurately simulated the soil-nail-wall interaction.Two factors were crucial to a successful result.First,probing the natural period of the complicated geometry of the model by applying white noises.Second,considering Rayleigh damping to withdraw unwanted noises and thus assess their permanent effects on the model.Rayleigh damping was applied instead of filtering the obtained results.展开更多
文摘A new multi-residue method based on solid-phase extraction (SPE) with centrifugation was developed for determination and quantitation of 67 pesticides in water samples. Two SPE cartridges were tested: Chromabond C18 and Oasis HLB. Parameters that influence the extraction efficiency such as the eluent volume, the sample loading volume, the addition of organic solvent to water sample, sorbent drying and elute concentration were optimized. The innovation of this work was the examination of the use of a centrifugation technique in both the drying and elution steps. When combined with centrifugation, the volume of the elution solvent was reduced to 2 mL and the time for sorbent drying decreased also to 10 min under vacuum. Under the optimized conditions, this method showed good recoveries higher than 65% - 68% for the 67 analyzed pesticides using the C18 and HLB cartridges with relative standard deviations lower than 9.7% - 12.3%. Limits of quantification were between 2 and 20 ng.L–1. The simplicity of the described method, use of less of organic solvent, short procedure time, and good recoveries demonstrate the advantages of this environmentally friendly approach for routine analysis of numerous samples.
基金supported by grants from the National Basic Research Program of China (No.2011CB504303)the Ministry of Science and Technology of China (No.2011ZX11307)the Natural Science Foundation of Guangdong Province (No.9151008901000134)
文摘Circulating microRNAs are robustly present in plasma or serum and have become a research focus as biomarkers for tumor diagnosis and prognosis.Centrifugation is a necessary procedure for obtaining highquality blood supernatant.Herein,we investigated one-step and two-step centrifugations,two centrifugal methods routinely used in microRNA study,to explore their effects on plasma microRNA quantification.The microRNAs obtained from one-step and two-step centrifugations were quantified by microarray and TaqMan-based real-time quantitative polymerase chain reaction(Q-PCR).Dynamic light scattering was performed to explore the difference underlying the two centrifugal methods.The results from the microarray containing 1,347 microRNAs showed that the signal detection rate was greatly decreased in the plasma sample prepared by two-step centrifugation.More importantly,the microRNAs missing in this plasma sample could be recovered and detected in the precipitate generated from the second centrifugation.Consistent with the results from microarray,a marked decrease of three representative microRNAs in twostep centrifugal plasma was validated by Q-PCR.According to the size distribution of all nanoparticles in plasma,there were fewer nanoparticles with size>1,000 nm in two-step centrifugal plasma.Our experiments directly demonstrated that different centrifugation methods produced distinct quantities of plasma microRNAs.Thus,exosomes or protein complexes containing microRNAs may be involved in large nanoparticle formation and may be precipitated after two-step centrifugation.Our results remind us that sample processing methods should be first considered in conducting research.
基金jointly funded by the National Natural Science Foundation of China (No.51304181)the Key Research Program of Frontier Sciences of Chinese Academy of Sciences (No.QYZDJ-SSW-JSC021)the Key Research Program of Chinese Academy of Sciences (No.ZDRW-ZS-2018-1)。
文摘This study used specularite, a high-gradient magnetic separation concentrate, as a raw material in reverse flotation.An iron concentrate with a grade of 65.1 wt% and a recovery rate of 75.31% were obtained.A centrifugal concentrator served as the deep purification equipment for the preparation of iron oxide red pigments, and its optimal rotating drum speed, feed concentration, and other conditions were determined.Under optimal conditions, a high-purity iron oxide concentrate with a grade of 69.38 wt% and a recovery rate of 80.89% were obtained and used as a raw material for preparing iron oxide red pigment.Calcining with sulfuric acid produced iron red pigments with different hues.Simultaneously, middlings with a grade of 60.20 wt% and a recovery rate of 17.51% were obtained and could be used in blast furnace ironmaking.High-value utilization of specularite beneficiation products was thus achieved.
文摘A total of 18 ejaculates were collected, once per week, from six fertile stallions for three consecutive weeks in October and November, to compare motility over time between extenders using four semen processing treatments. Four total aliquots of semen were used. Two aliquots of each semen collection were extended in either INRA96 or an experimental proprietary milk-based extender Walworth （WW） extender, and each was designed for multi-day storage of fresh chilled semen. Each aliquot was divided again, and either centrifuged at 600 μg for 10 min without cushion, or not centrifuged and extended to a final concentration of 25 × 10^6 spermatozoa/mL. The treatments evaluated were INRA96 without centrifugation （INRA-NC） or with centrifugation （INRA-C）, and Walworth extender without centrifugation （WW-NC） or with centrifugation （WW-C）. Total and progressive motility were measured using Sperm Vision~ CASA at 0, 24, 48 and 72 h post-collection. Samples were stored at 4 ℃. No differences were found between extenders in progressive （P = 0.13） or total motility （P = 0.14） over the four different time points without centrifugation. However, ejaculates processed in INRA-C group had the greater total and progressive motility （P 〈 0.05） over the four time points than ejaculates in the WW-C group. It was found that centrifugation and re-suspension of stallion semen in INRA96 improved the longevity of fresh chilled semen. However, when not using centrifugation, the Walworth extender proved to be as effective for maintaining spermatozoa motility across all time points as 1NRA96 , and may be an alternative for use in the equine breeding industry.
文摘We investigated whether an ordinary centrifuge can achieve the standard centrifugal effect required according to specifications for infectious disease screening using the Abbott i2000.Samples were collected and centrifuged following a standard operating procedure(SOP).They were then divided into three groups according to the results of the initial screening tests:a negative group,weak-positive group,and positive group.Twenty negative samples and all weak-positive and positive samples were re-analyzed.Two tubes for each re-analyzed sample were centrifuged simultaneously,one for 10 min at 10000x g,per recommendations,and one for 10 min at 2750^g.No significant difference was found between the groups using different centrifugal forces.There was a strong correlation in the quantitative values between the two conditions of centrifugation.Consistency analysis showed a Cronbach's alpha>0.8 for detection of Treponema pallidum,human immunodeficiency virus(HIV),hepatitis C virus(HCV),and hepatitis B surface antigen in the three groups(negative group,weak-positive group,and positive group)under different centrifugation conditions.Strong consistency was found under different centrifugal conditions,regardless of the initial testing results.In conclusion,we conducted centrifugation steps in duplicate,according to infectious disease screening protocols.Our study showed that all samples should be centrifuged using a recommended relative centrifugal force after a proper clotting time,as in the standard operating procedure of our laboratory.In this way,we were able to obtain the same results using an ordinary centrifuge as those obtained using a high-speed centrifuge,such as the Abbott i2000.
文摘In the present paper we have observed the effect of discontinuous gradient two-step Percoll centrifugation on depleting mature T lymphocytes from normal bone marrow. The pre-/post-Percoll percentage of CD34+, and Leu4+ cells in MNC was counted by using APAAP technique. As the two-step Percoll centrifugation is simple,and time saving, and decreases the incidence of contamination of cultured cells as well,This technique may be of value in serum-free culture of hematopoietic cells and immunological studies.
基金supported by a grant from Regione Abruzzo (P.O. FSE Abruzzo 2007 – 2013, Action 4, Type 4.1)the Provincial Breeders Federation of Trento, especially Dr. Claudio Valorz, for their support
文摘Background： Density gradient centrifugation was reported as a technique of semen preparation in assisted reproductive techniques in humans and animals. This technique was found to be efficient in improving semen quality after harmful techniques such as cryopreservation. Recently a modified technique, single layer centrifugation,was proposed as a technique providing a large amount of high quality spermatozoa, and this treatment was performed before conservation. Single layer centrifugation has been studied prevalently in stallions and in boars,but limited data were available for bulls. Occasionally bulls are known to experience a transient reduction in semen quality, thus techniques that allow improvement in semen quality could be applied in this context. The aim of this study was the evaluation of single layer and double layer centrifugation by the use of iodixanol, compared with conventional centrifugation and non-centrifuged semen, on the sperm characteristics during the cryopreservation process in bulls with normal and poor semen quality.Results： Single layer centrifugation and double layer centrifugation both significantly increased the percentage of normal spermatozoa and decreased the percentage of non-sperm cells in poor quality samples, while both were ineffective in those of normal quality. Sperm characteristics in poor quality samples increased after single layer centrifugation and double layer centrifugation, reaching values similar to those recorded in normal samples, and this trend is maintained after equilibration and after cryopreservation. On the other hand, SLC and DLC resulted in a consistent reduction in the spermatozoa recovered, and this resulted in a reduction of the absolute amount of spermatozoa cryopreserved in the normal samples, without a clear improvement in sperm characteristics in this type of sample.Conclusions： These data suggested that both SLC and DLC could be performed in practice, but their application should be limited to the cases in which the quality of the spermatozoa recovered is more important than the total amount of spermatozoa.
文摘Background： Direct ZN （Ziehl-Neelsen） sputum smear microscopy for diagnosis of TB （tuberculosis） has low sensitivity, especially in TB/HIV co-infected patients. Sputum concentration by bleach （NaOCI） with sedimentation has been used to increase the sensitivity of sputum smear microscopy in many settings but with varying results. Objective： To determine whether bleach plus centrifugation significantly improves the detection of AFB （acid-fast bacilli） in ZN smear-negative sputum specimens. Methods： Three hundred and seventy sputum specimens were collected from new TB suspects attending a Nairobi referral district hospital and processed for direct microscopy using ZN technique and culture on Lowenstein Jensen Media. All smear-negative specimens were treated with 3.5% bleach and left to stand for 30 min before centrifugation. The bleach treated smears were processed and examined using ZN technique. Results： Of the 370 specimens, 200 （54%） were positive culture. The number of sputum samples that were smear-positive by direct ZN was 138 （37.2%）, with a sensitivity of 66%. After treatment of direct ZN smear-negative specimens with 3.5% bleach and centrifugation, the total number of AFB smear-positive samples increased to 171 with an increase in sensitivity of 66% to 81.1% （15.1%）. Conclusion： In this study, bleach with centrifugation significantly increased the yield of sputum smear microscopy. Further evaluation of these techniques in routine programmes is required especially in settings where the burden of TB/HIV is high.
文摘The study aimed to investigate the effects of centrifugation of stallion semen on progressive sperm motility over a 72-hour period;and determine if the protein marker,precursor of A-kinase anchor protein 4(pro-AKAP4),may be maintained at a higher level over time when compared to non-centrifuged samples.Pro-AKAP4 has been studied for its function in stabilizing the structure of spermatozoa and its use as a marker for fertilizing capacity of spermatozoa.Semen collections were obtained from four fertile,commercially used Standardbred stallions collected three times each.Semen samples were diluted to a final concentration of 50 million total cells per milliliter.One extended aliquot of semen from each collection was used for the non-centrifuged treatment,and one extended aliquot of semen was centrifuged at 750×g for 10 min.The supernatant from the centrifuged sample was then removed with a 10 mL plastic transfer pipette,and the spermatozoa cell pellet was suspended in fresh extender to a final concentration of 50 million total cells per milliliter.Both centrifuged and non-centrifuged samples from each collection were stored in Equine Express II stallion semen shipping containers for 72 h and fresh ice packs were added to each container every 24 h.Both progressive sperm motility and levels of pro-AKAP4 were determined at times 0,12,24,48 and 72 h after collection.Differences were found between stallions,times and treatments with the main finding being that pro-AKAP4 concentration in centrifuged samples was maintained at a much higher level over the 72-hour period studied.
基金Grant sponsor:the Science and Technology Projects of Quanzhou,grant number:2019N085Sgrant sponsor:Startup Fund for Scientific Research,Fujian Medical University,grant number:2018QH1100
文摘Objective:Sperm preparation techniques and cryopreservation are widely used in assisted reproductive techniques(ART).How to improve the quality of sperm management is a matter of great concern.Phospholipase C-zeta(PLCζ)is considered a sperm-specific agent that activates oocyte activation and thus playing a crucial role in male fertility.However,the potential mechanisms by which semen processing and cryopreservation on PLCζcontribute to keyhole have not been addressed.Methods:In this study,semen samples were taken from have not been addressed 10 normozoospermic men.Each semen sample was assigned to the following groups:density gradient centrifugation(DGC)as control,microfluidic sorting,and cryopreservation.Sperm parameters of molity,viability,membrane integrity,and intracellular ROS were evaluated during sperm preparation and cryopreservation.The expression of PLCζin human sperm was determined by immunofluorescence and western blotting.Results:The results showed that molity,viability,and membrane integrity decreased in cryopreservation group.Intracellular ROS were also significantly increased compared to the the control group.There was no significant difference between DGC and microfluidic sorting group.Our investigation revealed that total levels of PLCζwere comparable between DGC and microfluidic sorting,but there were significantly reduced levels of PLCζafter cryopreservation as quantified by both immunofluorescenceand immunoblotting.PLCζimmunofluorescence in sperm revealed different PLCζlocalization patterns around the acrosomal(Ac),equatorial(Eq),post-acrosomal(PA)areas of sperm heads,and their combination.The predominant patterns of PLCζlocalization in DGC were similar to that of microfluidic sorting,with strong,with staining.In contrast,PLCζstaining in freeze-thawed sperm was considerably weaker fluorescence intensity.Conclusion:This study clarified the mechanism of sperm preparation and cryopreservation underlying effect on sperm characteristic,accompanied with PLCζexpresion.We demonstrated that microfluidic sorting provides a highly efficient preparation method for clinical selection of PLCζ-expressing sperm comparable to DGC gene expression.It is suggested that the cryopreservation of sperm has a significant detrimental effect on PLCζ.
基金supported by theDouble First-Class Key ProgramofGansu ProvincialDepartment of Education(grant number GCJ2022-38)Science and Technology Program of Gansu Province(grant number 22ZD6GA038)Key Research and Development Program of Gansu Province—Industrial Project(grant number 25YFGA021).
文摘In Brayton cycle energy storage systems powered by supercritical carbon dioxide(sCO_(2)),compressors are among themost critical components.Understanding their internal flowloss characteristics is,therefore,essential for enhancing the performance of such systems.This study examines the main sCO_(2) compressor from Sandia Laboratory,utilizing entropy production theory to elucidate the sources and distribution of energy losses both across the entire machine and within its key flow components.The findings reveal that turbulent viscous dissipation is the predominant contributor to total entropy production.Interestingly,while the relative importance of the entropy produced by various sources as the mass flow rate rises remains essentially unchanged,the total entropy production exhibits a nonmonotonic trend,first decreasing and then increasing with the mass flow rate.High entropy production in the impeller is primarily concentrated in the clearance region and along the rear cover of the impeller tip.In the diffuser,it is most pronounced on the front and rear plates and within the central flow path.Meanwhile,in the volute,the highest entropy production occurs around the diffuser outlet and along the outer region of the volute’s centerline.
基金supported by the National Natural Science Foundation of China(Grant Nos.52168046 and 52178321)the Natural Science Foundation of Guangxi Province,China(Grant No.2021AC18019).
文摘Precast driven piles are extensively used for infrastructure on soft soils,but the buildup of excess pore water pressure associated with pile driving is a challenging issue.The process of soil consolidation could take several months.Measures are sought to shorten the drainage path in the ground,and permeable pipe pile is a concept that involves drainage channels at the peak pore pressure locations around the pile circumference.Centrifuge tests were conducted to understand the responses of permeable pipe pile treated ground,experiencing the whole pile driving,soil consolidating,and axially loading process.Results show that the dissipation rate of pore pressures can be improved,especially at a greater depth or at a shorter distance from the pile,since the local hydraulic gradient was higher.Less significant buildup of pore pressures can be anticipated with the use of permeable pipe pile.For this,the bearing capacity of composite foundation with permeable pipe pile can be increased by over 36.9%,compared to the case with normal pipe pile at a specific time period.All these demonstrate the ability of permeable pipe pile in accelerating the consolidation process,mobilizing the bearing capacity of treated ground at an early stage,and minimizing the set-up effect.
基金Supported by Shanghai Natural Science Foundation(Nos.15ZR1448400 and 15ZR1448700)National Natural Science Foundation of China(No.31300825)
文摘DNA origami technique, a breakthrough in DNA nanotechnology, has been widely used to prepare complex DNA nanostructures with nanoscale addressability. However, the purity and yield are generally the bottleneck to application of DNA nanostructures, and current methods for purifying DNA origami nanostructures in large quantities are time-consuming and laborious. This study aims to develop a scalable, cost-effective and contamination-free method of purifying DNA origami nanostructures. We employ an effective and convenient purification approach to purify planar rectangle DNA origami structures through rate-zonal centrifugation. By subjecting DNA origami samples to high centrifugal force in a density gradient media of glycerol, well-folded nanostructures and by-products are separated successfully, which are confirmed by agarose gel electrophoresis and atomic force microscopy(AFM). This method will aid the production of pure rectangle DNA origami nanostructures in large quantity.
基金partially financed by Projects PTDC/CVT/108456/2008(FCT)and COMPETE:FCOMP-01-0124-FEDER-009565(FEDER),“Development of methods to increase the fertilizing ability of chilled and frozen stallion semen:a multidisciplinary ap-proach”.
文摘A significant number of stallions produce low quality ejaculates with high sensibility to chilling. Single Layer Centrifugation (SLC) with Andro-coll-ETM has been presented as an efficient method of selecting good quality spermatozoa. In the current study, changes in sperm quality (motility, viability, acrosome integrity and DNA damage) occurring during storage at 5?C for a maximum of 72 h, were investigated. For that, one ejaculate from 12 stallions was split in two aliquots: control and SLC-selected. Both aliquots were chilled and stored at 5?C and spermatozoa were evaluated for motility, viability and acrosome integrity at 24, 48 and 72 h post collection. DNA damage was evaluated at 48 h post collection using the comet assay. In the SLC-selected aliquots, there was a significant improvement in terms of progressive motility (0 h: P = 0.005;24 h: P 0.05). SLC with Androcoll-ETM improved semen quality prolonging sperm longevity of chilled semen (P = 0.012). This positive effect was more evident in ejaculates most sensitive to chilling that had a sharp decrease in motility in the first 24 h of refrigeration and for all ejaculates at 72 h post-chilling. Therefore, this method reveals to be a useful technique for selecting spermatozoa and maintain sperm quality during storage.
基金supported by the National Natural Science Foundation of China(Research Project No.52169018).
文摘Cavitation is an unavoidable phenomenon in the operation of centrifugal pumps.Prolonged cavitation can cause significant damage to the components of the flow channel,and in severe cases,it may even interfere with the normal energy exchange processes within the pump.Therefore,effective monitoring of cavitation in centrifugal pumps is crucial.This article presents a study that approaches the issue from an acoustic perspective,using experimental methods to gather and analyze acoustic data at the inlet and outlet of centrifugal pumps across various flow rates,with hydrophones as the primary measuring instruments.Results show that flow rate significantly affects noise levels in both non-cavitation and mild cavitation stages,with noise increasing as the flow rate rises.As the cavitation margin(NPSHa)decreases,inlet and outlet noise trends diverge:inlet noise drops sharply,while outlet noise initially increases before sharply decreasing.Both exhibit a distinct zone of abrupt change,where NPSHa values offer earlier cavitation detection than traditional methods.The noise at the pump’s inlet and outlet primarily consists of discrete and broadband noise,with most energy concentrated at discrete frequencies—shaft frequency(24 Hz),blade frequency(144 Hz),and their harmonics.As NPSHa decreases,the inlet’s discrete and broadband noise frequencies decline,while they increase at the outlet.Monitoring changes in these spectrum characteristics provides an additional means of predicting cavitation onset.
文摘A centrifugal pump with a specific speed ns=67 is considered in this study to investigate the impact of blade cutting(at the outlet edge)on the fluid-induced noise,while keeping all the other geometric parameters unchanged.The required unsteady numerical calculations are conducted by applying the RNG k-εturbulence model with the volute dipole being used as the sound source.The results indicate that the internal pressure energy of the centrifugal pump essentially depends on the blade passing frequency and its low-frequency harmonic frequency.Moreover,the pressure pulsation distribution directly affects the noise caused by the centrifugal pump.The sound pressure inside and outside the centrifugal pump and the sound power at the blade passing frequency gradually decrease increasing cutting distance of the impeller blades.When the cutting percentage is 1.21%,that is,the clearance ratio between impeller blade and tongue is 8.57%,the comprehensive performance of the centrifugal pump is the best.
基金funding support from the National Natural Science Foundation of China(Grant Nos.52208355and 52378308)Shenzhen University's 2035 Program for Excellent Research(Grant No.00000219).
文摘With the development of urban infrastructure,it is inevitable that shield tunnels will undercross intercity railways.However,the safe operation of intercity railways requires strict subgrade deformation.On the basis of the engineering background of the Lianghu Tunnel in Wuhan,the three-dimensional centrifuge test and numerical back analysis were used to study the development of subgrade surface settlement during shield tunneling.A three-dimensional numerical model with the same size as the prototype was subsequently established to further study the settlement development and torsion behavior of the subgrade during tunnel excavation.The results show that the maximum settlement point of the transverse settlement trough gradually moves to the tunnel axis during tunnel excavation and that the entire subgrade experiences torsional deformation.Moreover,the effect of the intersection angle between the axes of the tunnel and the subgrade on the surface settlement of the subgrade was further studied.The results show that the intersection angle has no effect on the maximum settlement,but the width of the settlement trough increases gradually with increasing angle.Finally,on the basis of the soil arching effect caused by tunnel excavation,the subgrade settlement during tunnel excavation is reduced by reinforcing the soil in different zones of soil arching.The results show that the settlement of the subgrade caused by the shield tunnel can be effectively controlled by adding reinforcement directly to the top of the tunnel,and the maximum settlement of the subgrade surface is reduced from 24.41 mm to 9.47 mm,a reduction of approximately 61.2%.
基金supported by the National Key Research and Development Program of China(No.2018YFC1802304)the National Natural Science Foundation of China(Nos.51988101 and 42077241)the Natural Science Foundation of Zhejiang Province(No.LCZ19E080002),China.
文摘Sand-bentonite(SB)cutoff walls are commonly used as barriers in polluted areas.The embedded part of an SB wall in an aquitard is crucial for its performance.In this study,a centrifuge modeling test was carried out to investigate the effect of contact between the key and the aquitard on the migration behavior of contaminants within an SB cutoff wall.The centrifuge was accelerated to 100g(gravitational acceleration)and maintained in-flight for 36 h,equivalent to 41 years of transport time in the prototype.Results showed that the contaminant concentration within the SB wall was higher downstream than in the middle in the thickness direction,and deeper regions exhibited a greater concentration than shallower ones.This concentration distribution indicated that contaminants were transported along the interface between the SB wall and the aquitard,bypassing the base of the SB wall to reach the downstream aquifer rapidly.An improved numerical simulation considering preferential interface migration was performed,which agreed with the centrifuge test results.The simulation results indicated that preferential interface migration,as a defect,significantly accelerated the speed of contaminant migration,reducing the breakthrough time of the SB wall to 1/9 of that without preferential interface migration.
基金supported by the Basic Science Center Program for Multiphase Media Evolution in Hypergravity of the National Natural Science Foundation of China(No.51988101)。
文摘This study focused on the hydraulic conductivity of sand in centrifuge modeling.A self-designed temperature-controlled falling-head permeameter apparatus was used,and a series of falling-head seepage tests were performed on sand samples with various porosities at different temperatures and centrifugal accelerations.The objectives were to qualitatively and quantitatively investigate the effects of temperature,porosity,and centrifugal acceleration on the hydraulic conductivity of sand and to study the applicability of the Kozeny-Carman equation for the centrifugal environment.Test results showed that in a similar temperature range and under the same porosity,the hydraulic conductivity of the sand is linearly correlated with centrifugal acceleration.When subjected to the same centrifugal acceleration and in a similar temperature range,the hydraulic conductivity of the sand exhibits an almost linear increase in relation to its porosity function(s^(3)/(1−s)^(2));the functional relationships between the hydraulic conductivity of the sand and temperature,centrifugal acceleration level,and porosity were established using two pathways.When the centrifugal acceleration is less than 50g,the Kozeny-Carman equation is effectively accurate in predicting the hydraulic conductivity of sand;however,when the centrifugal acceleration exceeds 50g,it is important to consider a significant error.
基金supported by the International Institute of Earthquake Engineering and Seismology(IIEES) as technical project No.760
文摘The primary goal of this study is to provide an efficient numerical tool to analyze the seismic performance of nailed walls.Modeling such excavation supports involves complexities due partly to the interaction of support with soil and partly because of the amplification of seismic waves through an excavation wall.Consequently,innovative modeling is suggested herein,incorporating the calibration of the soil constitutive model in a targeted range of stress and strain,and the detection of a natural period of complex systems,including soil and structure,while benefiting from Rayleigh damping to filter unwanted noises.The numerical model was achieved by simulating a previous centrifuge test of the excavation wall,manifested at the pre-failure state.Notably,the calibration of the soil constitutive model through empirical relations,which replaces the numerical reproduction of an element test,more accurately simulated the soil-nail-wall interaction.Two factors were crucial to a successful result.First,probing the natural period of the complicated geometry of the model by applying white noises.Second,considering Rayleigh damping to withdraw unwanted noises and thus assess their permanent effects on the model.Rayleigh damping was applied instead of filtering the obtained results.
