Stress evolution and support mechanism of a bolt anchored in a rock mass with a weak interlayer

By applying experimental method, the bolt stress and supporting mechanism is studied during the deformation process of a rock mass containing a weak interlayer. The force measuring bolt is installed manually and instrumented five pairs of symmetrical strain gauges. The experimental results show that the fully grouted bolt suffers tensile, compressive, bending and shear stress at the same time. The bolt stress evolution is closely related to the deformation stages of the rock mass which are very gradually varying stage, gradually varying stage at the pre-peak and suddenly varying stage at the post peak stage.The axial compressive stress in the bolt is mainly induced by the moment. Thus, in most cases the axial compressive stress is distributed on one side of the bolt. For axial stresses, induced by the axial force and the bending moment at the post-peak stage, three types of changing are observed, viz. increasingincreasing type, decreasing-increasing type and increasing-decreasing type. The stress characteristics of the bolt section in the weak interlayer are significantly different from those in the hard rock. The failure models of the anchored bolt are tensile failure and shear failure, respectively. The bolt not only provides constraints on the free surface of the rock mass, but also resists the axial and lateral loading by the bending moment. This study provides valuable guidelines for bolting support design and its safety assessment.

Support and Positioning Mechanism of a Detection Robot inside a Spherical Tank

Large pressure equipment needs to be tested regularly to ensure safe operation;wall-climbing robots can carry the necessary tools to inspect spherical tanks,such as cameras and non-destructive testing equipment.However,a wall-climbing robot inside a spherical tank cannot be accurately positioned owing to the particularity of the spherical tank structure.This paper proposes a passive support and positioning mechanism fixed in a spherical tank to improve the adsorption capacity and positioning accuracy of the inspection robot.The main body of the mechanism was designed as a truss composed of carbon fiber telescopic rods and can work in spherical tanks with diameters of 4.6-15.7 m.The structural strength,stiffness,and stability of the mechanism are analyzed via force and deformation simulations.By constructing a mathematical model of the support and positioning mechanism,the influence of structural deformation on the supporting capacity is analyzed and calculated.The robot positioning method based on the support and positioning mechanism can effectively locate the robot inside a spherical tank.Experiments verified the support performance and robot positioning accuracy of the mechanism.This research proposes an auxiliary support and positioning mechanism for a detection robot inside a spherical tank,which can effectively improve the positioning accuracy of the robot and meet the robotic inspection requirements.

Extra-corporeal membrane oxygenation in aortic surgery and dissection: A systematic review

BACKGROUND Very little is known about the role of extracorporeal membrane oxygenation(ECMO)for the management of patients undergoing major aortic surgery with particular reference to aortic dissection.AIM To review the available literature to determine if there was any evidence.METHODS A systematic literature search through PubMed and EMBASE was undertaken according to specific key words.RESULTS The search resulted in 29 publications relevant to the subject:1 brief communication,1 surgical technique report,1 invited commentary,1 retrospective case review,1 observational study,4 retrospective reviews,13 case reports and 7 conference abstracts.A total of 194 patients were included in these publications of whom 77 survived.CONCLUSION Although there is no compelling evidence for or against the use of ECMO in major aortic surgery or dissection,it is enough to justify its use in this patient population despite current adverse attitude.

Symptomatic and optimal supportive care of critical COVID-19:A case report and literature review

BACKGROUND Coronavirus disease 2019(COVID-19)severity is classified as asymptomatic,mild,moderate,severe,and critical.Mild cases account for a large percentage of cases in the epidemic and typically exhibit a favorable prognosis.However,a 49%-67%mortality is noted in critical cases.No COVID-19-specific drug has been reported to date,and symptomatic and optimal supportive care,including oxygenation,anti-coinfection treatments,and ventilation,represent the mainstay of treatment for this disease,especially in critical patients.CASE SUMMARY In the above-mentioned context,we share our experience with the treatment of one critical COVID-19 case and review the relevant literature.CONCLUSION Timely tracheal intubation,reasonable mechanical ventilation support,appropriate anti-infection treatment,and early anticoagulation and immunity support are key factors in the successful treatment of this case.

The role of temporary mechanical circulatory support in de novo heart failure syndromes with cardiogenic shock:A contemporary review

Cardiogenic shock(CS)is a complex clinical syndrome with a high mortality rate.It can occur to due to multiple etiologies of cardiovascular disease and is phenotypically heterogeneous.Acute myocardial infarction-related CS(AMI-CS)has historically been the most prevalent cause,and thus,research and guidance have focused primarily on this.Recent data suggest that the burden of non-ischemic CS is increasing in the population of patents requiring intensive care admission.There is,however,a paucity of data and guidelines to inform the management of these patients who fall into two broad groups:those with existing heart failure and CS and those with no known history of heart failure who present with"de novo"CS.The use of temporary mechanical circulatory support(MCS)has expanded across all etiologies,despite its high cost,resource intensity,complication rates,and lack of high-quality outcome data.Herein,we discuss the currently available evidence on the role of MCS in the management of patients with de novo CS to include fulminant myocarditis,right ventricular(RV)failure,Takotsubo syndrome,post-partum cardiomyopathy,and CS due to valve lesions and other cardiomyopathies.

Pharmacological strategies in extracorporeal membrane oxygenation weaning failure: a call to action

Extracorporeal membrane oxygenation has emerged as a viable alternative for stabilizing and improving critically ill patients in acute cardiovascular diseases.However,the weaning stage has been associated with a high morbidity and mortality rate.This makes searching for strategies that reduce failure in this final process necessary.Implementing a new approach must be tried and included in our protocols,seeking the patient’s well-being at all times.In this article,the authors discuss their point of view regarding potential pharmacological alternatives and the mechanism of action involved,which could decrease the mortality associated with this therapeutic.

To Be or Not to Be?The“Publish or Perish”Syndrome for English Teacher Educators in China

The philosophy of“publish or perish”has already been adopted as a yardstick by the vast majority of Chinese higher education institutions in their attempts to benchmark Western research universities in recent years,which has led to increasing pressure on university teachers to produce research publications.This paper addresses this endemic issue in China’s teaching universities with particular reference to its impact on English teacher educators.It points out that this trend is a result of unrealistically benchmarking research universities in well-resourced Western countries and overlooking the nature of teaching universities,the nature of English teacher educators’professional commitments,and the practical constraints on China’s teaching institutions.It has given rise to a variety of problems which,unless addressed properly,may demoralize English teacher educators and impair the quality of both teaching and research.The paper argues that a fair perception of and attitude towards research and realistic expectations of English teacher educators’research outcomes are essential.Practical implications at macro-,meso-and micro-levels are provided with the aim of improving the status quo.

Integrated management of cardiac failure:the cardiac failure clinic

The prevalence of the risk factors and the risk of cardiac failure are both increasing in China.This might be the consequence of the changes of the life conditions(emigration to the urban areas,changes in the diet and life style,lack of physical exercise,etc.).The wide range of clinical presentations of cardiac failure(acute or chronic)and of therapeutic approaches(medical or surgical)makes necessary the integration within the same structure of the various experts involved in the diagnosis and the treatment of cardiac diseases.Technologic and human resources required to offer all the options represent a multifaceted commitment which should be focused optimally in dedicated centers.In these centers,collaboration should replace competition between the medical and the surgical cardiac specialists.Development of team work should permit to optimize the cost efficacy of the treatments.Most of all,such a structure will facilitate the translation of innovative therapies between the research centers and clinical facilities.