scholarly journals Mechanism of Sleeper–Ballast Dynamic Impact and Residual Settlements Accumulation in Zones with Unsupported Sleepers

2021 ◽  
Vol 13 (14) ◽  
pp. 7740
Author(s):  
Mykola Sysyn ◽  
Michal Przybylowicz ◽  
Olga Nabochenko ◽  
Jianxing Liu
Keyword(s):  
Rolling Stock ◽  
Impact Point ◽  
Dynamic Impact ◽  
Quasistatic Loading ◽  
The Impact ◽  
Intensive Development ◽  
Specific Impact ◽  
Good Agreement

Unsupported sleepers or void zones in ballasted tracks are one of the most recent and frequent track failures. The void failures have the property of intensive development that, without timely maintenance measures, can cause the appearance of cost-expensive local instabilities such as subgrade damages. The reason for the intensive void development lies in the mechanics of the sleeper and ballast bed interaction. The particularity of the interaction is a dynamic impact that occurs due to void closure. Additionally, void zones cause inhomogeneous ballast pressure distribution between the void zone and fully supported neighbour zones. The present paper is devoted to studying the mechanism of the sleeper–ballast dynamic impact in the void zone. The results of experimental in situ measurements of rail deflections showed the significant impact accelerations in the zone even for lightweight slow vehicles. A simple three-beam numerical model of track and rolling stock interaction has shown dynamic interaction similar to the experimental measurements. Moreover, the model shows that the sleeper accelerations are more than 3 times higher than the corresponding wheel accelerations and the impact point appears before the wheel enters the impact point. The analysis of ballast loadings shows the specific impact behaviour in combination with the quasistatic part that is different for void and neighbour zones, which are characterised by high ballast pre-stressed conditions. The analysis of void size influence demonstrates that the maximal impact loadings and maximal wheel and sleeper accelerations appear at a certain void depth, after which the values decrease. The ballast quasistatic loading analysis indicates an increase of more than 2 times in the ballast loading in neighbour zones for long voids and almost full quasistatic unloading for short-length voids. However, the used imitation model cannot explain the nature of the dynamic impact. The mechanism of the void impact is clearly explained by the analytic solution using a simple clamped beam. A simplified analytical expression of the void impact velocity shows that it is linearly related to the wheel speed and loading. The comparison to the numerically simulated impact velocities shows a good agreement and the existence of the void depth with the maximal impact. An estimation of the long-term influences for the cases of normal sleeper loading, high ballast pre-stress and quasistatic loading in the neighbour zones and high impact inside the void is performed.

scholarly journals Mechanism of the Sleeper-Ballast Dynamic Impact in Void Zones

2021 ◽  
Author(s):  
Mykola Sysyn ◽  
Michal Przybylowicz ◽  
Olga Nabochenko ◽  
Jianxing Liu
Keyword(s):  
Rolling Stock ◽  
Impact Point ◽  
Dynamic Impact ◽  
Quasistatic Loading ◽  
The Impact ◽  
Intensive Development ◽  
Specific Impact ◽  
Good Agreement

Unsupported sleepers or void zones in ballasted tracks are one of the most recent and frequent track failures. The void failures have the property of intensive development that, without timely maintenance measures, can cause the appearance of cost-expensive local instabilities like subgrade damages. The reason of the intensive void development lies in the mechanics of the sleeper and ballast bed interaction. The particularity of the interaction is a dynamic impact that occur due to void closure. Additionally, void zones cause inhomogeneous ballast pressure distribution between the void zone and fully supported neighbour zones. The present paper is devoted studying the mechanism of the sleeper-ballast dynamic impact in the void zone. The results of experimental in-situ measurements of rail deflections showed the significant impact accelerations in the zone even for light-weight slow vehicles. A simple 3-beam numerical model of track and rolling stock interaction has shown the similar to the experimental measurements dynamic interaction. Moreover, the model shows that the sleeper accelerations are more than 3 times higher than the corresponding wheel accelerations and the impact point appear before the wheel enters the impact point. The analysis of ballast loadings shows the specific impact behaviour in combination with the quasistatic part that is different for void and neighbour zones, which are characterised with high ballast pre-stressed conditions. The analysis of void sizes influence demonstrate that the impact loadings, wheel and sleeper maximal accelerations appear at certain void depth after which the values decrease. The ballast quasistatic loading analysis indicates more than twice increase of the ballast loading in neighbour zones for long voids and almost full quasistatic unloading for short length voids. However, the used imitation model cannot explain the nature of the dynamic impact. The mechanism of the void impact is clearly explained by the analytic solution using a simple clamped beam. A simplified analytical expression of the void impact velocity shows that it is linearly related to the wheel speed and loading. The comparison to the numerically simulated impact velocities shows a good agreement and the existence of the void depth with the maximal impact. An estimation of the long-term influences for the cases of normal sleeper loading, high ballast pre-stress and quasistatic loading in the neighbour zones and high impact inside the void are performed.

scholarly journals Multi-model simulation of CO and HCHO in the Southern Hemisphere: biogenic emissions and model uncertainties

2015 ◽  
Vol 15 (2) ◽  
pp. 2615-2678 ◽  
Author(s):  
G. Zeng ◽  
J. E. Williams ◽  
J. A. Fisher ◽  
L. K. Emmons ◽  
N. B. Jones ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Atmospheric Chemistry ◽  
Model Simulation ◽  
Biogenic Emissions ◽  
Biogenic Emission ◽  
Source Regions ◽  
The Impact ◽  
Good Agreement

Abstract. We investigate the impact of biogenic emissions on carbon monoxide (CO) and formaldehyde (HCHO) in the Southern Hemisphere (SH), with simulations using two different biogenic emission inventories for isoprene and monoterpenes. Results from four atmospheric chemistry models are compared to continous long-term ground-based CO and HCHO column measurements at SH NDACC sites, and to in situ surface CO measurements from across the SH, representing a subset of the NOAA GMD network. Simulated mean model CO using the CLM-MEGANv2.1 inventory is in good agreement with both column and surface observations, whereas simulations adopting LPJ-GUESS emissions markedly underestimate measured column and surface CO at most sites. Differences in biogenic emissions cause large differences in CO in the source regions which propagate to the remote SH. Significant inter-model differences exist in modelled column and surface CO, due mainly to differences in the models' oxidation schemes for volatile organic compounds; secondary production of CO dominates these inter-model differences. While biogenic emissions are a significant factor in modelling SH CO, inter-model differences pose an additional challenge to constrain these emissions. Corresponding comparisons of HCHO columns at two SH mid-latitude sites reveal that all models significantly underestimate the observed values by approximately a factor of 2. There is a much smaller impact on HCHO of the significantly different biogenic emissions in remote regions, compared to the source regions. Decreased biogenic emissions cause decreased CO export to remote regions, which leads to increased OH; this in turn results in increased HCHO production through methane oxidation. In agreement with earlier studies, we corroborate that significant HCHO sources are likely missing in the models in the remote SH.

scholarly journals Long-Term Patterns and Trends of Shortwave Global Irradiance over the Euro-Mediterranean Region

Atmosphere ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1431
Author(s):  
Elissavet Galanaki ◽  
George Emmanouil ◽  
Konstantinos Lagouvardos ◽  
Vassiliki Kotroni
Keyword(s):  
Mediterranean Region ◽  
Spatiotemporal Variability ◽  
Reanalysis Dataset ◽  
Global Irradiance ◽  
Seasonal Basis ◽  
Region 10 ◽  
Annual Scale ◽  
Good Agreement

The spatiotemporal patterns and trends of shortwave global irradiance (SWGI) are a crucial factor affecting not only the climate but also sectors of the economy. In this work, the ERA5-Land reanalysis dataset is employed and evaluated against in situ measurements from a dense network of surface stations operated by the National Observatory of Athens over Greece, revealing a good agreement between the two datasets. Then, the spatiotemporal variability of SWGI is investigated over the Euro-Mediterranean region (10° W–42° E and 30° N–52° N) for a 40-year period (1981–2020). SWGI exhibits a smooth latitudinal variability from north to south of −5.4 W/m2/degree on an annual scale, while it varies significantly on a seasonal basis and is almost four times lower in the winter than in the summer. The SWGI trend during the analyzed period was found to be positive and statistically significant at the 95% confidence level. Spring and summer are the periods where positive and the strongest rates of SWGI trends are evident, while in the winter and autumn, negative or neutral trends were found. The increasing SWGI trend shows a slowdown during the beginning of the 2000s in all seasons, except autumn. The SWGI trend decreases by about −0.06 W/m2/decade every 100 m of elevation increase.

The Use of Laboratory-Measured and Strain-Gauge Backcalculated Asphalt Stiffness for Rutting Performance Prediction

2019 ◽  
Vol 2673 (3) ◽  
pp. 323-333
Author(s):  
Erdem Coleri ◽  
John T. Harvey
Keyword(s):  
Performance Prediction ◽  
Strain Gauge ◽  
Asphalt Concrete ◽  
Laboratory Tests ◽  
Concrete Materials ◽  
Long Term Performance ◽  
Term Performance ◽  
The Impact

Laboratory tests are conducted with asphalt concrete materials to determine the expected in-situ performance. In addition, laboratory test results are commonly used in mechanistic-empirical design methods for material characterization to improve the predictive accuracy of the models. However, the effectiveness of laboratory tests in characterizing the long-term performance of asphalt concrete materials needs to be validated to be able to use the results for pavement design and long-term performance prediction. Inaccurate performance characterization and prediction can directly affect the decision-making process for pavement maintenance, rehabilitation, and reconstruction and result in unexpected early failures in the field. The major objective of this study is to determine the impact of using laboratory-measured asphalt stiffness on the prediction accuracy of mechanistic-empirical models. In addition, the effect of using linear-elastic modeling assumptions (layered elastic theory) and neglecting the nonlinearity of pavement response at high load levels (and/or at high strain levels for weaker structures) on the predicted rutting performance was determined. In this study, the effectiveness of the use of laboratory asphalt stiffness tests for in-situ asphalt stiffness characterization was determined by comparing the rutting performance predicted using laboratory-measured stiffness to rutting predicted using strain-gauge backcalculated stiffness. It was determined that laboratory tests are able to characterize the in-situ stiffness characteristics of the asphalt mix used in this study and the stiffness characterization process suggested in this study can provide reliable rutting performance predictions. Results of this study are only applicable to tested rubberized asphalt concrete mixtures.

Belastung von Patienten und Gesundheitssystem durch Pleuraverweildrainage zur Versorgung chronischer Pleuraergüsse

2019 ◽  
Vol 7 (2) ◽  
pp. 84-85
Author(s):  
Axel Tobias Kempa
Keyword(s):  
Length Of Hospital Stay ◽  
Chest Drain ◽  
Long Term Outcomes ◽  
Talc Pleurodesis ◽  
In Situ Methods ◽  
Hospital Visits ◽  
The Impact

Background: Indwelling pleural catheters (IPC) offer an alternative to talc pleurodesis in recurrent effusion, especially in patients wishing to avoid hospitalization. Two randomized trials have demonstrated reduced time in hospital using IPCs versus talc pleurodesis in malignant pleural effusion (MPE). However, the impact of IPCs on hospital services and patients has not been well studied. Objectives: To analyze long-term outcomes of IPCs and understand the hospital burden in terms of requirement for hospital visits and contacts with healthcare, while the IPC was in situ. Methods: IPC insertions in a tertiary pleural center were analyzed retrospectively. Reviews of patients with IPCs in situ considered «additional» to routine clinical follow-up were defined pre-hoc. Results: A total of 202 cases were analyzed: 89.6% MPE group (n = 181) and 10.4% non-MPE group (n = 21). There were a median 3.0 (interquartile range [IQR] 3) and 2.0 (IQR 2) ipsilateral pleural procedures prior to each IPC insertion in non-MPE and MPE groups, respectively (p = 0.26), and a mean 1.3 (SD 1.7) planned IPC-related outpatient follow-up visits per patient. There were 2 (9.5%) and 14 (7.7%) IPC-related infections in non-MPE and MPE groups, respectively. Four (19.0%) and 44 (24.3%) patients required additional IPC-related reviews in non-MPE and MPE groups, respectively (p = 0.6), and these occurred within 250 days post IPC insertion. Conclusions: Although IPCs decrease initial length of hospital stay compared to talc pleurodesis via chest drain, IPCs are associated with significant hospital-visit burden, in addition to planned visits and regular home IPC drainages. IPC-using services need to be prepared for this additional work to run an IPC service effectively.

scholarly journals Denitrification by large NAT particles: the impact of reduced settling velocities and hints on particle characteristics

2014 ◽  
Vol 14 (20) ◽  
pp. 11525-11544 ◽  
Author(s):  
W. Woiwode ◽  
J.-U. Grooß ◽  
H. Oelhaf ◽  
S. Molleker ◽  
S. Borrmann ◽  
...  
Keyword(s):  
Stratospheric Ozone ◽  
Spherical Particles ◽  
Lagrangian Model ◽  
The Arctic ◽  
Reference Scenario ◽  
Climate Interactions ◽  
Stratospheric Clouds ◽  
The Impact ◽  
Good Agreement

Abstract. Vertical redistribution of HNO3 through large HNO3-containing particles associated with polar stratospheric clouds (PSCs) plays an important role in the chemistry of the Arctic winter stratosphere. During the RECONCILE (Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions) campaign, apparently very large NAT (nitric acid trihydrate) particles were observed by the airborne in situ probe FSSP-100 (Molleker et al., 2014). Our analysis shows that the FSSP-100 observations associated with the flight on 25 January 2010 cannot easily be explained assuming compact spherical NAT particles due to much too short growing time at temperatures below the existence temperature of NAT (TNAT). State-of-the-art simulations using CLaMS (Chemical Lagrangian Model of the Stratosphere; Grooß et al., 2014) suggest considerably smaller particles. We consider the hypothesis that the simulation reproduces the NAT particle masses in a realistic way, but that real NAT particles may have larger apparent sizes compared to compact spherical particles, e.g. due to non-compact morphology or aspheric shape. Our study focuses on the consequence that such particles would have reduced settling velocities compared to compact spheres, altering the vertical redistribution of HNO3. Utilising CLaMS simulations, we investigate the impact of reduced settling velocities of NAT particles on vertical HNO3 redistribution and compare the results with observations of gas-phase HNO3 by the airborne Fourier transform spectrometer MIPAS-STR associated with two RECONCILE flights. The MIPAS-STR observations confirm conditions consistent with denitrification by NAT particles for the flight on 25 January 2010 and show good agreement with the simulations within the limitations of the comparison. Best agreement is found if settling velocities between 100 and 50% relative to compact spherical particles are considered (slight preference for the 70% scenario). In contrast, relative settling velocities of 30% result in too weak vertical HNO3 redistribution. Sensitivity simulations considering temperature biases of ±1 K and multiplying the simulated nucleation rates by factors of 0.5 and 2.0 affect the comparisons to a similar extent, but result in no effective improvement compared to the reference scenario. Our results show that an accurate knowledge of the settling velocities of NAT particles is important for quantitative simulations of vertical HNO3 redistribution.

scholarly journals Homologous chromosomes in asexual rotifer Adineta vaga suggest automixis

2020 ◽  
Author(s):  
Paul Simion ◽  
Jitendra Narayan ◽  
Antoine Houtain ◽  
Alessandro Derzelle ◽  
Lyam Baudry ◽  
...  
Keyword(s):  
Genome Assembly ◽  
Genome Structure ◽  
Meiotic Pairing ◽  
Chromosome Conformation ◽  
Homologous Chromosomes ◽  
Ancient Asexual ◽  
High Doses ◽  
The Impact

ABSTRACTThe several hundreds of species of bdelloid rotifers are notorious because they represent an ancient clade comprising only asexual lineages1. Moreover, most bdelloid species have the ability to withstand complete desiccation and high doses of ionizing radiation, being able to repair their DNA after massive genome breakage2. To better understand the impact of long-term asexuality and DNA breakage on genome evolution, a telomere-to-tolemere reference genome assembly of a bdelloid species is critical3, 4. Here we present the first, high quality chromosome-scale genome assembly for the bdelloid A. vaga validated using three complementary assembly procedures combined with chromosome conformation capture (Hi-C) data. The different assemblies reveal the same genome architecture and using fluorescent in situ hybridization (FISH), we demonstrate that the A. vaga genome is composed of six pairs of homologous chromosomes, compatible with meiosis. Moreover, the synteny between homoeologous (or ohnologous) chromosomes is also preserved, confirming their paleotetraploidy. The diploid genome structure of A. vaga and the presence of very long homozygous tracts show that recombination between homologous chromosomes occurs in this ancient asexual scandal, either during DSB repair or during meiotic pairing. These homozygosity tracts are mainly observed towards the chromosome ends in the clonal A. vaga suggesting signatures of a parthenogenetic mode of reproduction equivalent to central fusion automixis, in which homologous chromosomes are not segregated during the meiotic division.

scholarly journals Damage mechanisms and embrittlement kinetics in a β-rich Ti 17 alloy after long term aging

2020 ◽  
Vol 321 ◽  
pp. 06008
Author(s):  
Layla SASAKI ◽  
Gilbert HENAFF ◽  
Mandana ARZAGHI ◽  
Patrick VILLECHAISE ◽  
Samuel HEMERY ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Detrimental Effect ◽  
Damage Tolerance ◽  
Tensile Tests ◽  
Mechanical Resistance ◽  
Damage Mechanisms ◽  
Structural Parts ◽  
The Impact

The Ti 17 (Ti-5Al-2Sn-2Zr-4Mo-4Cr) alloy is used in the first stages of engine compressors, at temperatures up to 450°C. However, its use in structural parts such as engine pylons is more prospective and raises the question of damage tolerance. As the engine pylon environment involves prolonged exposures to high temperatures, the impact of aging on mechanical properties has also to be taken in account. In this work, the consequences of a long-term aging (up to 10 000 h at 450°C) on the mechanical resistance of a Ti 17 alloy are examined at different scales, from macroscopic fatigue crack growth tests to in-situ tensile tests performed on micro samples in a SEM. The detrimental effect of aging on the mechanical properties of the Ti 17 alloy was then discussed in the light of damage mechanisms analysis and embrittlement kinetics.

scholarly journals Plastic Deformation of Thin Plates Subjected to Quasi-Static and Dynamic Loadings

2004 ◽  
Vol 1 (1) ◽  
pp. 59 ◽  
Author(s):  
A. A.N. Aljawi
Keyword(s):  
Plastic Deformation ◽  
Finite Element ◽  
Thin Plates ◽  
Circular Plates ◽  
Dynamic Impact ◽  
Deformation And Failure ◽  
Simply Supported ◽  
Dynamic Loadings ◽  
The Impact ◽  
Good Agreement

Deformation and failure of thin plates of mild steel were studied under quasi-static and dynamic impact loadings. Particular emphasis was placed on responses of simply supported circular plates subjected to centric orthogonal loadings. The latter comprised loadings due to relatively massive rigid cylindrical strikers with a hemispherical-end as well as a flat-end. The projectile motions featured variable and low impact velocities. Generally, good agreement was found between experimental results and those predicted by finite-element techniques for displacement-time curves and for force histories of the striker. It was concluded that the ABAQUS-based study (both the implicit and the explicit versions) revealed beneficial insights into the impact mechanics of plates by rigid projectiles. 

scholarly journals The impact of surgery on long-term survival of patients with primary intestinal non-Hodgkin lymphomas based on SEER database

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Cuifen Zhang ◽  
Xiaohong Zhang ◽  
Zeyu Liu ◽  
Jiahao Tao ◽  
Lizhu Lin ◽  
...  
Keyword(s):  
Multivariate Regression Analysis ◽  
Confounding Factors ◽  
Seer Database ◽  
Cancer Specific Survival ◽  
Term Survival ◽  
Non Hodgkin Lymphoma ◽  
Before And After ◽  
The Impact ◽  
Specific Impact

AbstractEvidence regarding the need for surgery for primary intestinal non-Hodgkin lymphoma (PINHL) patients with chemotherapy is limited and controversial. We aimed to investigate the specific impact of surgery on survival of PINHL patients. Data from PINHL patients (aged > 18 years) with chemotherapy between 1983 and 2015 were extracted from the Surveillance, Epidemiology, and End Results (SEER) database. We concerned about overall survival (OS) and improved cancer-specific survival (CSS). Propensity score matching (PSM) analysis was also used to explore the reliability of the results to further control for confounding factors. Finally, we screened 3537 patients. Multivariate regression analysis showed that patients with surgery and chemotherapy had better OS (hazard ratio [HR] 0.83; 95% confidence interval [CI] 0.75–0.93; p = 0.0009) and CSS (HR 0.87; 95% CI 0.77–0.99; p = 0.0404) compared with the non-operation group after adjusting for confounding factors. After PSM analysis, compared with non-surgery, surgery remained associated with improved OS (HR 0.77; 95% CI 0.68–0.87; p < 0.0001) and improved CSS (HR 0.82; 95% CI 0.72–0.95; p = 0.008) adjusted for baseline differences. In the large cohort of PINHL patients with chemotherapy older than 18 years, surgery was associated with significantly improved OS and CSS before and after PSM analysis.

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