A modified discrete element method for concave granular materials based on energy-conserving contact model

The development of a general discrete element method for irregularly shaped particles is the core issue of the simulation of the dynamic behavior of granular materials.The general energy-conserving contact theory is used to establish a universal discrete element method suitable for particle contact of arbitrary shape.In this study,three dimentional(3D)modeling and scanning techniques are used to obtain a triangular mesh representation of the true particles containing typical concave particles.The contact volumebased energy-conserving model is used to realize the contact detection between irregularly shaped particles,and the contact force model is refined and modified to describe the contact under real conditions.The inelastic collision processes between the particles and boundaries are simulated to verify the robustness of the modified contact force model and its applicability to the multi-point contact mode.In addition,the packing process and the flow process of a large number of irregular particles are simulated with the modified discrete element method(DEM)to illustrate the applicability of the method of complex problems.

Effect of propofol on immune function, stress response and hemodynamics in patients undergoing colorectal cancer surgery

Objective:To investigate the effects of propofol on immune function, stress response and hemodynamics in patients undergoing colorectal cancer surgery.Methods: 90 patients who were undergoing laparoscopic radical resection of colorectal cancer were randomly divided into propofol group (n=45) and sevoflurane group (n=45). The propofol group was anesthetized with propofol and the control group was given the same dose of sevoflurane. Changes in HR, SBP and DBP were observed before anesthesia, 1 h after induction, and at the end of surgery. The levels of CD19+, NK cells, MDA, SOD, insulin and cortisol were measured before anesthesia, at the end of operation and 24 h after operation.Results: Compared with before anesthesia, the levels of HR, SBP and DBP decreased at 1 h after induction (allP<0.05). At the end of the surgery, HR, SBP, and DBP returned to pre-anesthesia levels in both groups. The levels of HR, SBP and DBP in the propofol group were (74.56±7.55) times/min, (108.34±10.71) mmHg and (76.35±7.65) mmHg were higher than those in the sevoflurane group (allP<0.05). Compared with before anesthesia, CD19+ and NK cell ratio decreased at the end of surgery and 24 h after surgery, while MDA level increased at the end of surgery and 24 h after surgery (P<0.05). At the end of the propofol group, the proportion of CD19+and NK cells were (7.23±0.83)% and (15.17±1.21)% ,which were higher than the sevoflurane group (allP<0.05). At 24 h after surgery, the proportions of CD19+ and NK cells in the propofol group were (9.68±0.96) % and (19.58±1.86)%, which were higher than those in the sevoflurane group (all P<0.05). Compared with before anesthesia, MDA levels increased and SOD levels decreased at the end of surgery (P<0.05). At the end of the propofol group, the MDA level was (6.15±0.62) mmol/L, which was lower than that of the sevoflurane group (P<0.05). And the SOD level was (98.75±9.78) nU/mL, which was higher than the sevoflurane group (P<0.05). Compared with before anesthesia, the levels of insulin and cortisol increased at the end of surgery and 24 h after surgery (P<0.05). At the end of the operation, the propofol group insulin (22.69±2.28) mIU/mL was higher than the sevoflurane group, and the propofol group cortisol were (171.59±17.12) ng/mL, which were lower than sevoflurane group (allP<0.05).Conclusion:The patients undergoing radicalresection of colorectal cancer received propofol intravenous anesthesia preoperativel, which can effectively alleviate oxidative stress, and has little effect on hemodynamic parameters and stress response.

基于能量守恒接触模型的任意形态颗粒和复杂结构通用多边形网格离散元方法

非规则颗粒与复杂结构的接触行为在自然环境与工业生产过程中广泛存在,为对复杂结构中任意形态颗粒的动力过程进行合理仿真,本文基于能量守恒接触理论发展了一种通用的多边形网格离散元方法.在该方法中,将弹性应变能密度用于指定接触能函数的具体形式,从而得到了考虑接触区域复杂形貌的法向接触力模型.同时,针对由多边形网格统一构建的非规则颗粒和复杂结构,建立了一个统一的接触检测施行方案.因此,多边形网格离散元方法针对于颗粒-颗粒和颗粒-结构之间接触行为的模拟在形状构造、接触检测和接触力计算等方面均建立了通用和统一的模型,避免了因不同接触情形下接触计算模型的不同而导致的数值跳跃.为了定性地验证该方法的能量守恒性和鲁棒性,选取了一组考虑到不同形状类型(凸形、凹形和表面粗糙形)的颗粒样本进行了从简单到复杂的系列验证和模拟.相关验证及模拟结果表明,本文发展的通用多边形网格离散元方法及其包含的相关模型是研究复杂结构中非规则颗粒材料动力学行为的一种有效工具.

Rhizoma Drynariae Improves Endometrial Receptivity in a Mus Model of Dysfunctional Embryo Implantation

Background: Rhizoma drynariae is a traditional Chinese medicine used in orthopedics and traumatology, but its effect on endometrial receptivity remains unknown. Aims and Objectives: To observe effect of Rhizoma drynariae and its main components on endometrial receptivity in a mus model of dysfunctional embryo implantation. Materials and Methods: Mus models were established by the Gn RHa+HMG+HCG method. Normal mus receiving saline were used as controls and the remaining six groups were: model receiving saline, progynova, aspirin, Rhizoma drynariae, osteopractic total flavone, and naringin. Pinopodes in uterine endometrium were examined by scanning electron microscopy. Stem cell factor(SCF) m RNA expressions was determined by real-time RT-PCR, and estrogen receptor α(ERα), progesterone receptor(PR) by immunohistochemistry. Results: In the model group, surface morphology of endometrium was heterogeneous, without obvious pinopodes. In the Rhizoma drynaria and progynova groups, pinopodes were abundant. Compared with the blank group, model group had lower levels of SCF(-47%), ERα(-63%) and PR(-50%)(all P<0.05). In comparison, Rhizoma drynariae group had higher levels of SCF(+73%), ERα(+118%) and PR(+101%)(all P<0.01). The individual main components of Rhizoma drynariae had variable efficacy. Conclusion: Rhizoma drynariae could improve endometrial receptivity of mouse models of dysfunctional embryo implantation as shown by increased numbers of pinopodes and higher levers of SCF, ERα, PR compared with the model group.

Superquadric DEM-SPH coupling method for interaction between non-spherical granular materials and fluids

The research on the coupling method of non-spherical granular materials and fluids aims to predict the particle-fluid interaction in this study.A coupling method based on superquadric elements is developed to describe the interaction between non-spherical solid particles and fluids.The discrete element method(DEM)and the smoothed particle hydrodynamics(SPH)are adopted to simulate granular materials and fluids.The repulsive force model is adopted to calculate the coupling force and then a contact detection method is established for the interaction between the superquadric element and the fluid particle.The contact detection method captures the shape of superquadric element and calculates the distance from the fluid particle to the surface of superquadric element.Simulation cases focusing on the coupling force model,energy transfer,and large-scale calculations have been implemented to verify the validity of the proposed coupling method.The coupling force model accurately represents the water entry process of a spherical solid particle,and reasonably reflects the difference of solid particles with different shapes.In the water entry process of multiple solid particles,the total energy of the water entry process of multiple solid particles tends to be stable.The collapse process of the partially submerged granular column is simulated and analyzed under different parameters.Therefore,this coupling method is suitable to simulate fluid-particle systems containing solid particles with multiple shapes.

The Coiling of Split Dandelion Scape Induced by Cell Hygroscopicity

It is of great significance to study the water absorption and expansion of cells,which are essential for the growth and life regulation of plants,not only for understanding the complex life phenomena of plants,but also for the manufacture of biomimetic materials.The main purpose of this study is to shed light on the mechanism of a novel coiling phenomenon of the split dandelion scape soaked in water and the high concentration mannitol solution.We discovered that the difference between water absorption/dehydration capacities of inner cells and lateral cells of the split dandelion scape generates asymmetric expansion/contraction between inner and lateral layers,resulting two opposite coiled patterns.Analogous to the deformable hypothesis of the thermal expansion model,the water absorption-induced cell expansion model was proposed to explain the coiling process of the split dandelion scape.Both the simulation and experimental results revealed that the coiling of dandelion scape is strongly depended on the response of cells to the stimulation of the solution environment.Showing considerable potential load bearing capacity of plants,the coiling phenomenon can be an inspiration to the designs of soft robots and bionic sensors for humidity control.