Quality Investigations on Ground Improvement in Highway Engineering Practice

The constructions of highway often pass through naturally-deposited liquefiable grounds. Anti-earthquake design is essential for highway engineering practice in east China. Gravel column and dynamic compaction are often adopted for the improvements of such problematical grounds. The stability and settlement of the treated grounds depend much on the construction quality. How to investigate the quality of ground improvement is an important issue in highway engineering practice. In this study, the method of Spectral-Analysis-of-Surface-Waves (SASW) is applied to evaluate the construction quality on ground improvements by vibration gravel piles and dynamic compaction technique. The case studies show that the SASW method is a powerful way for investigating the improvement quality in highway engineering practice. The shear wave velocity measured in SASW has a relative good relationship with the N value measured in standard penetration tests

Effectiveness of Dynamic Compaction on Liquefied Foundation in Highway Practice

In this paper, the in-situ dynamic compaction tests with different values of single-drop-compaction energy are performed on a liquefiable ground encountered in highway engineering practice. Excess pore pressure, total surface settlement and lateral deformation under dynamic compaction impact are measured and analyzed at different conditions, such as single drop-compaction-energy, drop numbers, depth of soil layer etc. The standard penetration test (SPT) is used for investigating the compaction effectiveness. The investigation results indicate dynamic compaction technique is an effective way for improving liquefiable ground in highway engineering practice. Relatively small single-drop-compaction energy and relatively more drop numbers should be adopted for improving natural sedimentary liquefiable ground with dynamic compaction. The in-situ dynamic compaction tests show that the effective effect range by dynamic compaction impact depends on the single-drop-compaction energy. It is also found that the measured maximum lateral deformation has a good linear relationship with the total vertical surface settlement

PSR J1926-0652: A Pulsar with Interesting Emission Properties Discovered at FAST

We describe PSR J1926-0652, a pulsar recently discovered with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Using sensitive single-pulse detections from FAST and long-term timing observations from the Parkes 64-m radio telescope, we probed phenomena on both long and short time scales. The FAST observations covered a wide frequency range from 270 to 800 MHz, enabling individual pulses to be studied in detail. The pulsar exhibits at least four profile components, short-term nulling lasting from 4 to 450 pulses, complex subpulse drifting behaviours and intermittency on scales of tens of minutes. While the average band spacing P3 is relatively constant across different bursts and components, significant variations in the separation of adjacent bands are seen, especially near the beginning and end of a burst. Band shapes and slopes are quite variable, especially for the trailing components and for the shorter bursts. We show that for each burst the last detectable pulse prior to emission ceasing has different properties compared to other pulses. These complexities pose challenges for the classic carousel-type models.Comment: 13pages with 12 figure

Development and validation of risk prediction model for identifying 30-day frailty in older inpatients with undernutrition: A multicenter cohort study

ObjectiveTo develop and externally validate a frailty prediction model integrating physical factors, psychological variables and routine laboratory test parameters to predict the 30-day frailty risk in older adults with undernutrition.MethodsBased on an ongoing survey of geriatrics syndrome in elder adults across China (SGSE), this prognostic study identified the putative prognostic indicators for predicting the 30-day frailty risk of older adults with undernutrition. Using multivariable logistic regression analysis with backward elimination, the predictive model was subjected to internal (bootstrap) and external validation, and its calibration was evaluated by the calibration slope and its C statistic discriminative ability. The model derivation and model validation cohorts were collected between October 2018 and February 2019 from a prospective, large-scale cohort study of hospitalized older adults in tertiary hospitals in China. The modeling derivation cohort data (n = 2,194) were based on the SGSE data comprising southwest Sichuan Province, northern Beijing municipality, northwest Qinghai Province, northeast Heilongjiang Province, and eastern Zhejiang Province, with SGSE data from Hubei Province used to externally validate the model (validation cohort, n = 648).ResultsThe incidence of frailty in the older undernutrition derivation cohort was 13.54% and 13.43% in the validation cohort. The final model developed to estimate the individual predicted risk of 30-day frailty was presented as a regression formula: predicted risk of 30-day frailty = [1/(1+e-riskscore )], where riskscore = -0.106 + 0.034 × age + 0.796 × sex -0.361 × vision dysfunction + 0.373 × hearing dysfunction + 0.408 × urination dysfunction - 0.012 × ADL + 0.064 × depression - 0.139 × nutritional status - 0.007 × hemoglobin - 0.034 × serum albumin - 0.012 × (male: ADL). Area under the curve (AUC) of 0.71 in the derivation cohort, and discrimination of the model were similar in both cohorts, with a C statistic of nearly 0.7, with excellent calibration of observed and predicted risks.ConclusionA new prediction model that quantifies the absolute risk of frailty of older patients suffering from undernutrition was developed and externally validated. Based on physical, psychological, and biological variables, the model provides an important assessment tool to provide different healthcare needs at different times for undernutrition frailty patients.Clinical trial registrationChinese Clinical Trial Registry [ChiCTR1800017682]

Conception de robot orientée commande

It is well -known that parallel robots have a lot of applications in industry for their high stiffness , high payload , can reach higher acceleration and speed . However , because of their complex structure , their control may be troublesome. When high accuracy is needed, the detailed robot model is necessary . However , even detailed models still suffer from the problem of inaccuracy in reality because of robot assembly and manufacturing errors . Sensor - based control approaches have been proven to be more efficient than model-based controllers in terms of accuracy since they overcome the complex robot models and inconsistency errors. Nevertheless, when applying the visual servoing, there are always some problems in the control process , such as the controller singularities . Thus , this thesis proposes proposes a control based design metodology which takes into account the accuracy performance of the controller in the design process to get the geometric parameters of the robot. This thesis applied the control-based design methodology to the optimal design of three types of parallel robots: Five-bar mechanisms , DELTA robots , Gough -Stewart platforms . Three types of controllers are selected in the design process : leg -direction -based visual servoing, line-baesd visual servoing and image moment visual servoing . Design optimization problems are formulated to find the geometric parameters of the robot . Co-simulations are performed to check the accuracy performance of the robots obtained from the optimization. Experiments are performed with two DELTA robot prototypes in order to validate the controller accuracy.Il est bien connu que les robots parallèles ont de nombreuses applications dans l ’industrie. Cependant, en raison de leur structure complexe, leur contrôle peut être difficile. Lorsqu'une précision élevée est nécessaire , un modèle complet du robot détaillé est nécessaire . Les approches de contrôle référencées capteurs se sont avérées plus efficaces , en termes de précision que les contrôleurs basés modèles puisqu'elles s’affranchissent des modèles de robots complexes et des erreurs de modélisation associées. Néanmoins, lors de l'application de d’un asservissement visuel , il y a toujours des problèmes dans le processus de contrôle , tels que les singularités du contrôleur . Cette thèse propose une méthodologie de conception orientée commande qui prend en compte les performances de précision du contrôleur dans le processus de conception du robot pour obtenir les paramètres géométriques optimaux de ce dernier Trois contrôleurs ont été sélectionnés dans le processus de conception du robot : les commandes basées sur l’observation des directions des jambes, les commandes basées sur l’observation des lignes et les commandes basées sur des moments dans l'image .Pour vérifier les performances en terme de précision des robots optimisés, nous avons effectué des co-simulations des robots optimisés avec les contrôleurs correspondants . En terme d’expérimentation, deux prototypes de robots DELTA ont été conçus et expérimentés afin de valider la précision du contrôleu

Sensor-based design of a Delta parallel robot

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