Local geometric information and discontinuity features are key aspects of the analysis of the evolution and failure mechanisms of unstable rock blocks in rock tunnels.This study demonstrates the integration of terrest...Local geometric information and discontinuity features are key aspects of the analysis of the evolution and failure mechanisms of unstable rock blocks in rock tunnels.This study demonstrates the integration of terrestrial laser scanning(TLS)with distinct element method for rock mass characterization and stability analysis in tunnels.TLS records detailed geometric information of the surrounding rock mass by scanning and collecting the positions of millions of rock surface points without contact.By conducting a fuzzy K-means method,a discontinuity automatic identification algorithm was developed,and a method for obtaining the geometric parameters of discontinuities was proposed.This method permits the user to visually identify each discontinuity and acquire its spatial distribution features(e.g.occurrences,spac-ings,trace lengths)in great detail.Compared with hand mapping in conventional geotechnical surveys,the geometric information of discontinuities obtained by this approach is more accurate and the iden-tification is more efficient.Then,a discrete fracture network with the same statistical characteristics as the actual discontinuities was generated with the distinct element method,and a representative nu-merical model of the jointed surrounding rock mass was established.By means of numerical simulation,potential unstable rock blocks were assessed,and failure mechanisms were analyzed.This method was applied to detection and assessment of unstable rock blocks in the spillway and sand flushing tunnel of the Hongshiyan hydropower project after a collapse.The results show that the noncontact detection of blocks was more labor-saving with lower safety risks compared with manual surveys,and the stability assessment was more reliable since the numerical model built by this method was more consistent with the distribution characteristics of actual joints.This study can provide a reference for geological survey and unstable rock block hazard mitigation in tunnels subjected to complex geology and active rockfalls.展开更多
Type WYZ 97 eighteen information noninsulate frequency shift automatic blocking system is the most advanced railroad signaling system in China nowadays.The article introduced its principles,technical targets,features ...Type WYZ 97 eighteen information noninsulate frequency shift automatic blocking system is the most advanced railroad signaling system in China nowadays.The article introduced its principles,technical targets,features and the applications.展开更多
With rapid development of the railway traffic, the moving block signaling system （MBS） method has become more and more important for increasing the track capacity by allowing trains to run in a shorter time-headway ...With rapid development of the railway traffic, the moving block signaling system （MBS） method has become more and more important for increasing the track capacity by allowing trains to run in a shorter time-headway while maintaining the required safety margins. In this framework, the tracking target point of the following train is moving forward with its leading train. This paper focuses on the energy saving tracking control of two successive trains in MBS. Nonlinear programming method is used to optimize the energy-saving speed trajectory of the following train. The real-time location of the leading train could be integrated into the optimization process. Due to simplicity, it can be used for online implementation. The feasibility and effectiveness are verified through simulation. The results show that the new method is efficient on energy saving even when disturbances present.展开更多
A 26-year-old male with a history of hypertrophic cardiomyopathy(HCM) and ventricular arrhythmias s/p automatic implantable cardioverter defibrillator(AICD) placement presented for open reduction and internal fixation...A 26-year-old male with a history of hypertrophic cardiomyopathy(HCM) and ventricular arrhythmias s/p automatic implantable cardioverter defibrillator(AICD) placement presented for open reduction and internal fixation of an open third metacarpal fracture and extensor tendon repair. He underwent successful surgery after placement of an ultrasound-guided infraclavicular brachial plexus block with ropivacaine 0.5% as the main anesthetic. This case report discusses the anesthetic management of patients with HCM and AICD, different approaches available for brachial plexus blockade, and potential complications of anesthesia and surgery in this group of patients.展开更多
基金support of the National Natural Science Foundation of China(Grant No.42102316)the Open Project of the Technology Innovation Center for Geological Environment Monitoring of Ministry of Natural Resources of China(Grant No.2022KFK1212005).
文摘Local geometric information and discontinuity features are key aspects of the analysis of the evolution and failure mechanisms of unstable rock blocks in rock tunnels.This study demonstrates the integration of terrestrial laser scanning(TLS)with distinct element method for rock mass characterization and stability analysis in tunnels.TLS records detailed geometric information of the surrounding rock mass by scanning and collecting the positions of millions of rock surface points without contact.By conducting a fuzzy K-means method,a discontinuity automatic identification algorithm was developed,and a method for obtaining the geometric parameters of discontinuities was proposed.This method permits the user to visually identify each discontinuity and acquire its spatial distribution features(e.g.occurrences,spac-ings,trace lengths)in great detail.Compared with hand mapping in conventional geotechnical surveys,the geometric information of discontinuities obtained by this approach is more accurate and the iden-tification is more efficient.Then,a discrete fracture network with the same statistical characteristics as the actual discontinuities was generated with the distinct element method,and a representative nu-merical model of the jointed surrounding rock mass was established.By means of numerical simulation,potential unstable rock blocks were assessed,and failure mechanisms were analyzed.This method was applied to detection and assessment of unstable rock blocks in the spillway and sand flushing tunnel of the Hongshiyan hydropower project after a collapse.The results show that the noncontact detection of blocks was more labor-saving with lower safety risks compared with manual surveys,and the stability assessment was more reliable since the numerical model built by this method was more consistent with the distribution characteristics of actual joints.This study can provide a reference for geological survey and unstable rock block hazard mitigation in tunnels subjected to complex geology and active rockfalls.
文摘Type WYZ 97 eighteen information noninsulate frequency shift automatic blocking system is the most advanced railroad signaling system in China nowadays.The article introduced its principles,technical targets,features and the applications.
文摘With rapid development of the railway traffic, the moving block signaling system （MBS） method has become more and more important for increasing the track capacity by allowing trains to run in a shorter time-headway while maintaining the required safety margins. In this framework, the tracking target point of the following train is moving forward with its leading train. This paper focuses on the energy saving tracking control of two successive trains in MBS. Nonlinear programming method is used to optimize the energy-saving speed trajectory of the following train. The real-time location of the leading train could be integrated into the optimization process. Due to simplicity, it can be used for online implementation. The feasibility and effectiveness are verified through simulation. The results show that the new method is efficient on energy saving even when disturbances present.
文摘A 26-year-old male with a history of hypertrophic cardiomyopathy(HCM) and ventricular arrhythmias s/p automatic implantable cardioverter defibrillator(AICD) placement presented for open reduction and internal fixation of an open third metacarpal fracture and extensor tendon repair. He underwent successful surgery after placement of an ultrasound-guided infraclavicular brachial plexus block with ropivacaine 0.5% as the main anesthetic. This case report discusses the anesthetic management of patients with HCM and AICD, different approaches available for brachial plexus blockade, and potential complications of anesthesia and surgery in this group of patients.
