Key Technology of Embedded System Implementation for Software-based CNC System

The software-based computer numerical control（CNC） system includes three types of tasks： periodic real-time tasks, aperiodic real-time tasks, and non-real-time tasks. The tasks are characterized by concurrency, hybridization, and correlation, which make system implementation difficult. The conventional scheduling algorithm can not meet the demands of system implementation in the software-based CNC system completely. The uncertainty factors when running real-time tasks affect control performance by degrading manufacturing accuracy as a result of system resource and processor use restrictions. To address the technical difficulty of embedded system implementation, a novel fuzzy feedback scheduling algorithm based on output jitter of key real-time tasks for a software-based CNC system is proposed. Time characteristics, such as sampling jitter, input-output jitter, and non-schedulability are discussed, followed by quantification through simulations of the impact of time characteristics on manufacturing accuracy. On the basis of this research, the scheduler architecture is designed, and then the algorithm table is calculated. When the system resource changes, the key periodic real-time tasks meet their deadlines by means of dynamically adjusting the task period. The simulated results show that the machining precision rises by an order of magnitude for the proposed scheduler in resource-constrained software-based CNC systems. Moreover, unlike conventional feedback scheduling methods, the algorithm in this paper does not rely on the availability of task execution times and is easy to implement while incurring only a small overhead.

Advances in Technologies of Piezoelectric Pumping with Valves

Piezoelectric pump faces unprecedented challenges when higher expectation and requirements need to be met in their applications mainly to medical treatment,hygiene and public health,and preventive healthcare.Specifically,the piezoelectric pump with valve has the disadvantages of complex structure,high duty cycle of valves,and valve movement lagged behind piezoelectric ceramics oscillation.In an attempt to inhibit its shortcomings,some researchers presented novel concepts for structural design of piezoelectric pump with valve,which could become a new research focus.Among them,the investigation into various soft valves,represented by soft structure valves made of rigid materials and soft material valves made of flexible materials,has been fruitful in recent years.The integrated design of both material and structure can tackle the problems encountered in the study of piezoelectric pump with valve,thus simplifying the pump structure,reducing the duty-cycle of valves,and improving the lagging of valve motion.In addition,new inventions of pump structure have sprung up,such as the pumps containing a single-chamber with double-drive,single-chamber with single-drive in series and single-chamber with single-drive in parallel,as well as the mixed-chamber in series and parallel.After surveying the recent progresses made by dominant academia in the development of piezoelectric pump encompassing valve,with a particular emphasis on structure design of both valve and pump body,we also summarize and identify the future research directions.

The Stylistic Analysis of The Terror of Death

The Terror of Death is one of Keats most famous poems. It describes the fear of the writer facing death. The essay argues that the linguistic analysis of the poem The Terror of Death on the phonological and syntactic dimension effectively contributes to the critical interpretation. The diction and rhetoric device adopted by the writer also highlight the theme of the sonnet.

Advances in Valveless Piezoelectric Pump with Cone-shaped Tubes

This paper reviews the development of valve- less piezoelectric pump with cone-shaped tube chrono- logically, which have widely potential application in biomedicine and micro-electro-mechanical systems because of its novel principles and deduces the research direction in the future. Firstly, the history of valveless piezoelectric pumps with cone-shaped tubes is reviewed and these pumps are classified into the following types： single pump with solid structure or plane structure, and combined pump with parallel structure or series structure. Furthermore, the function of each type of cone-shaped tubes and pump structures are analyzed, and new direc- tions of potential expansion of valveless piezoelectric pumps with cone-shaped tubes are summarized and deduced. The historical argument, which is provided by the literatures, that for a valveless piezoelectric pump with cone-shaped tubes, cone angle determines the flow resistance and the flow resistance determines the flow direction. The argument is discussed in the reviewed pumps one by one, and proved to be convincing. Finally, it is deduced that bionics is pivotal in the development of valveless piezoelectric pump with cone-shaped tubes fromthe perspective of evolution of biological structure. This paper summarizes the current valveless piezoelectric pumps with cone-shaped tubes and points out the future development, which may provide guidance for the research of piezoelectric actuators.

电视辅助胸腔镜在胸部肿瘤外科中的应用(英文)

Objective:The purpose of this study was to summarize and discuss the application of video-assisted thoracoscopic surgery(VATS) in the treatment of 58 chest cancers.Methods:The clinical data of 58 patients with thoracic tumor were analyzed retrospectively in treatment with VATS from July 2005 to June 2007.The surgery treatments included pulmonary wedge resection,enucleation of esophageal leiomyoma,bronchogenic cyst excision,mediastinal cyst excision,etc.Results:All patients were treated with VATS.Three patients of those with lung cancer underwent open-chest lobectomy resection.All patients had no death and few complications,and all discharged.Conclusion:VATS has advantages of less trauma,suffering light,quick recovery and small postoperative complications and has a great advantage in the treatment of chest benign tumors.But in the treatment of chest malignant tumors we should strictly control indications.