Hematodinium is a type of parasitic dinoflagellate that infects marine crustaceans globally.The parasite lives mainly in the hemolymph or hemocoels of affected hosts,and results in mortalities due to malfunction or lo...Hematodinium is a type of parasitic dinoflagellate that infects marine crustaceans globally.The parasite lives mainly in the hemolymph or hemocoels of affected hosts,and results in mortalities due to malfunction or loss of functions of major organs.In recent years,the parasite had developed into an emerging epidemic pathogen not only affecting wild populations of economically valuable marine crustaceans in western countries but also the sustainable yield of aquaculture of major crabs in China.The epidemics of the parasitic diseases expanded recently in the coastal waters of China,and caused frequent outbreaks in aquaculture of major crab species,especially Portunus trituberculatus and Scylla paramamosain.In addition,the pathogen infected two species of co-cultured shrimps and multiple cohabitating wild crabs,implying it is a significant threat to the sustainable culture of commercially valuable marine crustaceans.In particular,the polyculture system that is widely used along the coast of China may facilitate the spread and transmission of the pathogen.Thus,to provide a better understanding of the biological and ecological characteristics of the parasitic dinoflagellate and highlight important directions for future research,we have reviewed the current knowledge on the taxonomy,life cycle,pathogenesis,transmission and epidemiology of Hematodinium spp.Moreover,ecological countermeasures have been proposed for the prevention and control of the emerging infectious disease.展开更多
The parasitic motion has been widely recognized as the major drawback of the parallel mechanism.Therefore a class of 2R1T PMs(parallel mechanism)without parasitic motion has been synthesized.However,these PMs can only...The parasitic motion has been widely recognized as the major drawback of the parallel mechanism.Therefore a class of 2R1T PMs(parallel mechanism)without parasitic motion has been synthesized.However,these PMs can only rotate around two axes in sequential order.It decreases the performance of the balancing adjustment of the end-efector.In this paper,a family of 2R1T PMs without parasitic motion was reconstructed by using a novel method based on the remarkable properties of rotational bifurcation mechanisms,which can rotate in sequential order.Furthermore,some PMs rotating around two continuous axes in an arbitrary order are established by adding single joints.Taking the practicability of these structures into consideration,the workspace of 3-PRPS PM was analyzed as an example.Moreover,this study explores the practical application of the PMs without parasitic motion in developing balance mechanisms in rough-terrain fre-fghting robots.During the climbing process,the tank is adjusted to be parallel to the horizontal plane in real-time.It is proved that this kind of structure realizes continuous rotation around two rotation axes on the premise of no parasitic motion.展开更多
In design of flexure mechanism, diminishing the parasitic-motion is a key point to improve the accuracy. However, most of existing topics concentrate on improving the accuracy of linear-motion flexure mechanisms via c...In design of flexure mechanism, diminishing the parasitic-motion is a key point to improve the accuracy. However, most of existing topics concentrate on improving the accuracy of linear-motion flexure mechanisms via compensating the parasitic error, but few research the multi-dimensional flexure mechanisms. A general design principle and method for high-precision flexure mechanisms based on the parasitic-motion compensation is presented, and the proposed method can compensate the parasitic rotation in company with translation, or the parasitic translation in company with rotation, or both. The crucial step for the method is that the parasitic motion of a flexure mechanism is formulated and evaluated in terms of its compliance. The overall compliance matrix of a general flexure mechanism is formulated by using screw theory firstly, then the criteria for the parasitic motions is introduced by analyzing the characteristics of the resultant compliance matrix as well as with aid of the concept of instantaneous rotation center. Subsequently, a compliance-based compensation approach for reducing parasitic-motion is addressed as the most important part. The design principles and procedure are further discussed to help with improving the accuracy of flexure mechanisms, and case studies are provided to illustrate this method. Finally, an analytical verification is provided to demonstrate that the symmetry design philosophy widely used in flexure design can effectively improve accuracy in terms of the proposed method. The proposed compensation method can be well used to diminish the parasitic-motion of multi-dimensional flexure mechanisms.展开更多
基金This research was financially supported by the NSFC-Shandong Joint program(Grant No.U1906214)the general program(Grant No.41676102)of National Natural Science Foundations of China.
文摘Hematodinium is a type of parasitic dinoflagellate that infects marine crustaceans globally.The parasite lives mainly in the hemolymph or hemocoels of affected hosts,and results in mortalities due to malfunction or loss of functions of major organs.In recent years,the parasite had developed into an emerging epidemic pathogen not only affecting wild populations of economically valuable marine crustaceans in western countries but also the sustainable yield of aquaculture of major crabs in China.The epidemics of the parasitic diseases expanded recently in the coastal waters of China,and caused frequent outbreaks in aquaculture of major crab species,especially Portunus trituberculatus and Scylla paramamosain.In addition,the pathogen infected two species of co-cultured shrimps and multiple cohabitating wild crabs,implying it is a significant threat to the sustainable culture of commercially valuable marine crustaceans.In particular,the polyculture system that is widely used along the coast of China may facilitate the spread and transmission of the pathogen.Thus,to provide a better understanding of the biological and ecological characteristics of the parasitic dinoflagellate and highlight important directions for future research,we have reviewed the current knowledge on the taxonomy,life cycle,pathogenesis,transmission and epidemiology of Hematodinium spp.Moreover,ecological countermeasures have been proposed for the prevention and control of the emerging infectious disease.
基金Supported by National Natural Science Foundation of China(Grant No.31670719).
文摘The parasitic motion has been widely recognized as the major drawback of the parallel mechanism.Therefore a class of 2R1T PMs(parallel mechanism)without parasitic motion has been synthesized.However,these PMs can only rotate around two axes in sequential order.It decreases the performance of the balancing adjustment of the end-efector.In this paper,a family of 2R1T PMs without parasitic motion was reconstructed by using a novel method based on the remarkable properties of rotational bifurcation mechanisms,which can rotate in sequential order.Furthermore,some PMs rotating around two continuous axes in an arbitrary order are established by adding single joints.Taking the practicability of these structures into consideration,the workspace of 3-PRPS PM was analyzed as an example.Moreover,this study explores the practical application of the PMs without parasitic motion in developing balance mechanisms in rough-terrain fre-fghting robots.During the climbing process,the tank is adjusted to be parallel to the horizontal plane in real-time.It is proved that this kind of structure realizes continuous rotation around two rotation axes on the premise of no parasitic motion.
基金Supported by National Natural Science Foundation of China(Grant No.51305022)the Fundamental Research Funds for the Central Universities,China(Grant No.FRF-TP-13-013A)National Science Foundation for Post-doctoral Scientists of China(Grant No.2012M520163)
文摘In design of flexure mechanism, diminishing the parasitic-motion is a key point to improve the accuracy. However, most of existing topics concentrate on improving the accuracy of linear-motion flexure mechanisms via compensating the parasitic error, but few research the multi-dimensional flexure mechanisms. A general design principle and method for high-precision flexure mechanisms based on the parasitic-motion compensation is presented, and the proposed method can compensate the parasitic rotation in company with translation, or the parasitic translation in company with rotation, or both. The crucial step for the method is that the parasitic motion of a flexure mechanism is formulated and evaluated in terms of its compliance. The overall compliance matrix of a general flexure mechanism is formulated by using screw theory firstly, then the criteria for the parasitic motions is introduced by analyzing the characteristics of the resultant compliance matrix as well as with aid of the concept of instantaneous rotation center. Subsequently, a compliance-based compensation approach for reducing parasitic-motion is addressed as the most important part. The design principles and procedure are further discussed to help with improving the accuracy of flexure mechanisms, and case studies are provided to illustrate this method. Finally, an analytical verification is provided to demonstrate that the symmetry design philosophy widely used in flexure design can effectively improve accuracy in terms of the proposed method. The proposed compensation method can be well used to diminish the parasitic-motion of multi-dimensional flexure mechanisms.
