Dilatancy relation for overconsolidated clay

A distinct feature of overconsolidated (OC) clays is that their dilatancy behavior is dependent on the degree of overconsolidation. Typically, a heavily OC clay shows volume expansion, whereas a lightly OC clay exhibits volume contraction when subjected to shear. Proper characterization of the stress-dilatancy behavior proves to be important for constitutive modeling of OC clays. This paper presents a dilatancy relation in conjunction with a bounding surface or subloading surface model to simulate the behavior of OC clays. At the same stress ratio, the proposed relation can reasonably capture the relatively more dilative response for clay with a higher overconsolidation ratio (OCR). It may recover to the dilatancy relation of a modified Cam-clay (MCC) model when the soil becomes normally consolidated (NC). A demonstrative example is shown by integrating the dilatancy relation into a bounding surface model. With only three extra parameters in addition to those in the MCC model, the new model and the proposed dilatancy relation provide good predictions on the behavior of OC clay compared with experimental data

One-step implementation of multi-qubit conditional phase gating with nitrogen-vacancy centers coupled to a high-Q silica microsphere cavity

The diamond nitrogen-vacancy (NV) center is an excellent candidate for quantum information processing, whereas entangling separate NV centers is still of great experimental challenge. We propose an one-step conditional phase flip with three NV centers coupled to a whispering-gallery mode cavity by virtue of the Raman transition and smart qubit encoding. As decoherence is much suppressed, our scheme could work for more qubits. The experimental feasibility is justified.Comment: 3 pages, 2 figures, Accepted by Appl. Phys. Let

Numerical modeling of pile penetration in silica sands considering the effect of grain breakage

International audienceCurrent numerical platforms rarely consider the effect of grain breakage in the design of sandy soil foundations. This paper presents an enhanced platform for large deformation analyses which considers the effect of grain breakage during pile penetration in silica sand. For this purpose, a model based on critical state theory has been developed within the framework of multisurface plasticity to account in the same constitutive platform the effect of stress dilatancy and particle fragmentation. Furthermore, to implement the underlying constitutive equations into a finite element code, a stress integration scheme has been adopted by extending a cutting plane algorithm to the model with multiple yielding mechanisms. A laboratory model test and a series of centrifuge tests of pile penetration are simulated to verify the performance of the selected constitutive approach in terms of pile resistance and grain breakage distribution, with the parameters of sand calibrated through a set of drained triaxial compression tests from low to very high confining pressure. Some extra features of the enhanced platform are also discussed, such as: i) the effect of sand crushability on pile resistance and ii) the nonlinear relation of pile resistance to sand density. The proposed findings demonstrate the capability of this numerical platform to proper design of pile foundation in sandy soils and highlight the interplay between stress dilatancy and grain breakage mechanisms during pile penetration processes

Advanced numerical modelling of caisson foundations in sand to investigate the failure envelope in the H-M-V space

International audienceThis paper focuses on the identification of the failure envelope of a caisson foundation in sand using an advanced critical state-based sand model (SIMSAND) and the Combined Lagrangian Smoothed Particle Hydrodynamics Method (CLSPH). The parameters of the SIMSAND constitutive model are first calibrated using triaxial tests on Baskarp sand. In order to validate the combined CLSPH-SIMSAND approach, a cone penetration test, model tests and a field test on a reduced scale caisson foundation are simulated. After full numerical validations with different scales from laboratory to in-situ conditions, a numerical parametrical study is then introduced considering different sand properties (density, friction angle, deformability, crushability) and caisson dimensions (soil-structure contact surface area, diameter-depth ratio) and complex combined loading paths to identify the failure envelope in the horizontal force (H), bending moment (M), vertical force (V) space. The influence of the caisson foundation contact surface area, aspect ratio and soil parameters are considered and quantified. Finally, an analytical formula is proposed for the 3D failure envelope in the H-M-V space

Clinical effects of low-molecular-weight heparin combined with ulinastatin in children with acute pancreatitis

Purpose: To explore the clinical effects of low-molecular-weight heparin (LMWH) combined with ulinastatin (UTI) in children with acute pancreatitis.Methods: In total, 560 patients with severe acute pancreatitis treated at Binzhou People’s Hospital, Shandong, China, from April 2012 to June 2014 were enrolled in this study. They were divided into control (280 patients, ulinastatin + conventional treatment) and observational groups (280 patients, LMWH + ulinastatin + conventional treatment). The treatment lasted for 2 weeks. Clinical parameters, laboratory test indices, Acute Physiology and Chronic Health Evaluation (APACHE II) score, and computed tomography score of pancreatic necrosis (CTSPN) were assessed in both groups.Results: On admission, no significant differences were noted in clinical features, laboratory parameters, APACHE II scores, or CTSPN between the two groups (all p > 0.05). After 2 weeks of treatment, serum amylase, urine amylase, prothrombin time, fibrinogen, partial thromboplastin time, and platelet count in the study group were 913 ± 281 U/L, 1893 ± 295 U/L, 16 ± 1.60 s, 3 ± 0.60 g/L, 39.80 ± 5.60 s, and 294 ± 49 × 109/L, respectively, all of which were similar or superior to those in the control group (1738 ± 346 U/L, 2453 ± 473 U/L, 15 ± 1.50 S, 2.50 ± 0.50, 39.80 ± 5.90, and 192 ± 37 × 109/L)). APACHE II scores and CTSPN after 2 weeks of treatment in the observation group were 8.50 ± 1.80 and 2.10 ± 1, respectively, which were superior to those in the control group (9.60 ± 2.40 and 4.30 ± 2.60, respectively; p < 0.05). Moreover, the incidence of complications, mortality rate, and average duration of the hospital stay in the observation group were lower than those in the control group (p > 0.05). The cure rate in the observation group was higher than that in the control group.Conclusions: LMWH combined with UTI enhances the efficacy of conventional treatment and reduces mortality. Thus, it is a potentially effective treatment strategy for severe acute pancreatitis in children.Keywords: Acute pancreatitis, Low-molecular-weight heparin, Multiple organ function syndrome, APACHE II score, Pancreatic necrosi

A New Multistage Medical Segmentation Method Based on Superpixel and Fuzzy Clustering

The medical image segmentation is the key approach of image processing for brain MRI images. However, due to the visual complex appearance of image structures and the imaging characteristic, it is still challenging to automatically segment brain MRI image. A new multi-stage segmentation method based on superpixel and fuzzy clustering (MSFCM) is proposed to achieve the good brain MRI segmentation results. The MSFCM utilizes the superpixels as the clustering objects instead of pixels, and it can increase the clustering granularity and overcome the influence of noise and bias effectively. In the first stage, the MRI image is parsed into several atomic areas, namely, superpixels, and a further parsing step is adopted for the areas with bigger gray variance over setting threshold. Subsequently, designed fuzzy clustering is carried out to the fuzzy membership of each superpixel, and an iterative broadcast method based on the Butterworth function is used to redefine their classifications. Finally, the segmented image is achieved by merging the superpixels which have the same classification label. The simulated brain database from BrainWeb site is used in the experiments, and the experimental results demonstrate that MSFCM method outperforms the traditional FCM algorithm in terms of segmentation accuracy and stability for MRI image

The physical origin of the periodic activity for FRB 20180916B

Fast radio bursts (FRBs) are transient radio signals with millisecond-duration, large dispersion measure (DM) and extremely high brightness temperature. Among them, FRB 20180916B has been found to have a 16-day periodic activity. However, the physical origin of the periodicity is still a mystery. Here, we utilize the comprehensive observational data to diagnose the periodic models. We find that the ultra-long rotation model is the most probable one for the periodic activity. However, this model cannot reproduce the observed rotation measure (RM) variations. We propose a self-consistent model, i.e., a massive binary containing a slowly rotational neutron star and a massive star with large mass loss, which can naturally accommodate the wealth of observational features for FRB 20180916B. In this model, the RM variation is periodic, which can be tested by future observations.Comment: 12 pages, 8 figure

N′-(But-2-enyl­idene)­iso­nicotino­hydrazide

In the title Schiff base compound, C10H11N3O, the pyridine ring is twisted with respect to the mean plane containing the hydrazine chain, making a dihedral angle of 31.40 (9)°. The NH group inter­acts with the N atom of the pyridine ring through N—H⋯N hydrogen bonds to build up a zigzag chain developing parallel to the (01) plane