The historic centres revitalization addresses the challenges related to the preservation of fundamental heritage values. At a time, when everyone looks with concern to our cities' future, it is important to reflect o...The historic centres revitalization addresses the challenges related to the preservation of fundamental heritage values. At a time, when everyone looks with concern to our cities' future, it is important to reflect on the received heritage, seeking the most appropriate answers to the planning of the historic centres. These fabrics are reference places in the urban space, due to their role of memorial testimony and of generators of cultural and economic dynamics. However, often times, inherited urban fabrics are affected by the limitations of the heritage policies which, for being too general and based on theoretical and abstract frameworks, have difficulty incorporating the characteristics of each area and neglect the formulation of specific criteria and intervention methods. The purpose of this paper is to provide a comparative reading of the levels of urban renewal allowed by the planning tools. This study chooses two historic centers in Portugal: Oporto and Guimarfies historic centres (World Heritage Sites since 1996 and 2001, respectively, and were the last to get this classification in Portugal). This reflection is a contribution to peer trends and raise the discussion on the role that the different heritage policies have to the revitalization of the historic centres.展开更多
In CNC machining, two essential components decide the accuracy and machining time for a sculptured surface: one is the step-size interval, the other is the tool-path interval. Due to the limitation of the conventional...In CNC machining, two essential components decide the accuracy and machining time for a sculptured surface: one is the step-size interval, the other is the tool-path interval. Due to the limitation of the conventional method for calculating the tool-path interval, it cannot satisfy the machining requirement for high-speed and high-resolution machining. Accordingly, for high-speed and high-resolution machining, the current study proposes a new tool-path interval algorithm, plus a variable step-size algorithm for NURBS. Furthermore, a new type cutter, which can improve the cutting efficiency, is investigated in the paper. The transversal equation of the torus cutter onto the flat plan is given in this paper. The tool-path interval is calculated with the transversal equation and the proposed algorithm. The illustrated example shows that the redundant tool paths can be reduced because an accurate tool-path interval could be calculated.展开更多
Computational fluid dynamics(CFD) has recently emerged as an effective tool for the investigation of the hydraulic parameters and efficiency of tray towers.The computation domain was established for two types of orien...Computational fluid dynamics(CFD) has recently emerged as an effective tool for the investigation of the hydraulic parameters and efficiency of tray towers.The computation domain was established for two types of oriented valves within a tray and meshed into two parts with different grid types and sizes.The volume fraction correlation concerning inter-phase momentum transfer source was fitted based on experimental data,and built in UDF for simulation.The flow pattern of oriented valve tray under different operating conditions was simulated under Eulerian-Eulerian framework with realizable k-ε model.The predicted liquid height from CFD simulation was in good agreement with the results of pressure drop and volume fraction correlations.Meanwhile,the velocity distribution and volume fraction of the two phases were demonstrated and analyzed,which are useful in design and analysis of the column trays.展开更多
The methodology of 5-axis cutter selection to avert collision for free-form surface machining by flat-end cutters is presented. The combination of different cutters is adopt aiming at short machining time and high pre...The methodology of 5-axis cutter selection to avert collision for free-form surface machining by flat-end cutters is presented. The combination of different cutters is adopt aiming at short machining time and high precision. The optimal small cutter is determined based on the geometric information of the points where a cutter most probably collide with the machined surface. Several larger cutters are selected to machine the surface in order to find the interference-free area. The difference of machining time for this area between the optimal small cutter and the large cutters is calculated. The functional relationship between the machining time and the radius of a cutter is established, by which the optimal number of cutters is obtained. The combination of cutters, which possesses the minimum overall machining time, is selected as the optimal cutter sizes. A case study has demonstrated the validity of the proposed methodology and algorithms.展开更多
Nowadays, urban design faces complex demands. It has become a necessity to negotiate between stakeholder objectives, the expectations of citizens and the demands of planning. It is desirable to involve the stakeholder...Nowadays, urban design faces complex demands. It has become a necessity to negotiate between stakeholder objectives, the expectations of citizens and the demands of planning. It is desirable to involve the stakeholders and citizens from an early stage in the planning process to enable their different viewpoints to be successfully expressed and comprehended. Therefore, the basic aim of the study was how the MR (mixed reality) application is designed to encourage and improve communication on urban design among stakeholders and citizens? In this paper, we discuss new approaches to visualize urban building and environment alternatives to different stakeholders and provide them with tools to explore different approaches to urban planning in order to support citizen's participation in urban planning with augmented and mixed reality. The major finding of the study is that learning "how these participatory technologies may help build a community of practice around an urban project". And throughout the different experiences, we can learn to assist towards development of a methodology to use the mixed reality as a simulation tool in the enhancement of collaborative interaction in real-Egyptian project. So, we can determine a number of recommendations to deal with new participatory design tools for urban planning projects.展开更多
In this paper, the authors establish the Amalab-integrated operation management system (A-IOMS) as a new way to carry out software development and monitor business processes. This new system puts the previously cons...In this paper, the authors establish the Amalab-integrated operation management system (A-IOMS) as a new way to carry out software development and monitor business processes. This new system puts the previously constructed the Amalab-project planning navigation system (A-PPNS) to work throughout the entire organization. The A-IOMS has several key elements. Specifically, the authors have constructed: (1) a Hi-reliability estimation system diagnostic tool that pinpoints problems with software development estimates and offers a prescription for resolving them; (2) a QA table map that allows for an immediate, thorough, and consistent quality assurance process; (3) a system for sharing software development schedules throughout the organization; and (4) a technological asset completion reporting system for passing down and cultivating software development technologies and strategically expanding them. The authors verified the effectiveness of the A-IOMS at company A, a systems integration company, and the given outcomes were obtained.展开更多
The lack of care related to maintenance management is directly linked to the absence of plans for maintenance of buildings. Because of that, there is a big incidence of building accidents caused by the negligence of m...The lack of care related to maintenance management is directly linked to the absence of plans for maintenance of buildings. Because of that, there is a big incidence of building accidents caused by the negligence of managers and the lack of investment. The research has shown that, although building inspection is a consolidated building maintenance tool, managers do not prepare their building maintenance plan, nor use building inspection as a tool, leading the buildings to the premature obsolescence. The research calls attention to the building inspection technique that can be used to evaluate building maintenance and conservation. It is also a tool for analysis and investment planning based on actions to solve failures and anomalies that might come out during the building inspection. Those failures and anomalies are classified according to their degree of risk, determining the technical priorities of the investment adjustment in the maintenance plan. The paper presents a risk analysis methodology which classifies inspect elements in a building, determining the priority order of services to be executed on a scale from minimum risk (1) to imminent risk (5). The method shows a tool for building inspection, and it serves as a guideline for building maintenance interventions.展开更多
The main purpose of this paper is to analyze the necessity of a Geographical Observatory of Atmospheric Pollution (GEOAP) in the Greek territory. The analysis performed is mainly focused on the benefits of the futur...The main purpose of this paper is to analyze the necessity of a Geographical Observatory of Atmospheric Pollution (GEOAP) in the Greek territory. The analysis performed is mainly focused on the benefits of the future function of the GEOAP to the environmental planning of the country and it could also provide an environmental management tool for the whole region. Measuring and mapping the pollution data and at the same time performing the geographical analysis of the complexity and the characteristics of natural and human environment can be useful tool in observation, management, and planning of the environmental policy of the country.展开更多
Strategic planning is one of the most important management tools for organizational decision making. The nuclear area represents a segment of energy production used by many countries in America, Europe and Asia. It is...Strategic planning is one of the most important management tools for organizational decision making. The nuclear area represents a segment of energy production used by many countries in America, Europe and Asia. It is known that in the future nuclear energy can be a major exit to the global energy crisis. The aim of this research was to use the BSC (Balanced Scorecard) as a strategic tool for decision making in a teaching and research institution of the nuclear area--IPEN (Nuclear and Energy Research Institute), located in the city of Sao Paulo, which belongs to the CNEN (National Nuclear Energy Commission) in Brazil. The methodology used in this academic doctoral study was a case study, which considered the period of research from December 2012 to December 2015. The main results expected from this case study are: the improvement of information flow, the view, the increased visibility of an organization providing education and especially research in relation to published works, increased interaction among IPEN and the main global research institutes and centers, increasing academic production of technical articles, indicator improvement, improving the monitoring of management actions, among others. Given the expected results one can conclude that this study will be of great value to the IPEN and also for the Brazilian energy sector, as it will allow and contribute to the dissemination and demystification of nuclear power as an energy source of mankind, its peaceful applications and for the management activity of knowledge and innovation production in the nuclear area of IPEN.展开更多
This research is a development in management information system (MIS) planning based on operation analysis and development according to concurrent engineering approach and reestablishment of database management. Acc...This research is a development in management information system (MIS) planning based on operation analysis and development according to concurrent engineering approach and reestablishment of database management. According to our case study industry, such industry currently used traditional network systems such as LAN, and "Bus Network" Network Topology. Client/Server distributed computing has a problem with database management in data redundancy, data inconsistency, and data independency. For Network Topology, Bus Network has problem with multitasking since the network are able to handle only a set of data at a time so the traffic problem will occur when multiple users request for the service. Thus, such condition is inconsistent with concurrent engineering which must be able to access the data simultaneously. As a consequence, this study develops a network system, network system of working system, using LAN and "Star Network" network topology. The file server processing distributed is an application while database is stored in host computer or file server but the data will be processed in users' computer. When the user needs to access the data, file server will send it to the user and the user can further analysis or manage such data in the user computer, so called "Hierarchical Database Model". Hierarchical database structure is easily developed like general organization command structure with different level of responsibility. In details, the data level in the database is divided into three levels including DBI, DB2, and DB3, so development of simultaneously systemic flow and access of various critical data is performed in parallel. Furthermore, this is consistent with access of all three data levels including: Level 1 is overall dataflow of both inside and outside the organization; Level 2 is dataflow of each division in the organization; and Level 3 is dataflow of subunit in each division in the organization. After systemize flow and access of data with concurrent engineering as mentioned, it provided optimal efficiency in the whole production system management reducing loss in the whole system of the organization展开更多
The cutter runout effect has significant influence on the shape of cutter swept surface and the machining surface quality. Hence,it is necessary to integrate the cutter runout effect in cutter swept surface modeling,g...The cutter runout effect has significant influence on the shape of cutter swept surface and the machining surface quality. Hence,it is necessary to integrate the cutter runout effect in cutter swept surface modeling,geometric error prediction and tool path optimization for five-axis flank machining. In this paper,an envelope surface model considering cutter runout effect is first established,and geometric errors induced by runout effect are derived based on the relative motion analysis between the cutter and part in machining. In the model,the cutter runout is defined by four parameters,including inclination angle,location angle,offset value and the length of cutter axis. Then the runout parameters are integrated into the rotation surface of each cutting edge that is used to form the final cutter envelope surface for the five-axis machining process. Thus,the final resulting geometric errors of the machined surface induced by cutter runout can be obtained through computing the deviations from the nominal cutter swept surface. To reduce these errors,an iterative least square method is used to optimize the tool paths for five-axis flank machining. Finally,a validation example is given for a specific ruled surface. Results show the effectiveness and feasibility of the analytical model of geometric errors induced by cutter runout,and also show that the geometric errors can be reduced significantly using the proposed tool path planning method.展开更多
Traditional five-axis tool path planning methods mostly focus on differential geometric characteristics between the cutter and the workpiece surface to increase the material removal rate(i.e.,by minimizing path length...Traditional five-axis tool path planning methods mostly focus on differential geometric characteristics between the cutter and the workpiece surface to increase the material removal rate(i.e.,by minimizing path length,improving curvature matching,maximizing local cutting width,etc.) . However,material removal rate is not only related to geometric conditions such as the local cutting width,but also constrained by feeding speed as well as the motion capacity of the five-axis machine. This research integrates machine tool kinematics and cutter-workpiece contact kinematics to present a general kinematical model for five-axis machining process. Major steps of the proposed method include:(1) to establish the forward kinematical relationship between the motion of the machine tool axes and the cutter contact point;(2) to establish a tool path optimization model for high material removal rate based on both differential geometrical property and the contact kinematics between the cutter and workpiece;(3) to convert cutter orientation and cutting direction optimization problem into a concave quadratic planning(QP) model. Tool path will finally be generated from the underlying optimal cutting direction field. Through solving the time-optimal trajectory generation problem and machining experiment,we demonstrate the validity and effectiveness of the proposed method.展开更多
The expanding scale and increasing rate of marine biological invasions have been documented since the early 20th century. Besides their global ecological and economic impacts, non-indigenous species (NIS) also have ...The expanding scale and increasing rate of marine biological invasions have been documented since the early 20th century. Besides their global ecological and economic impacts, non-indigenous species (NIS) also have attracted much attention as opportunities to explore important eco-evolutionary processes such as rapid adaptation, long-distance dispersal and range expansion, and secondary contacts between divergent evolutionary lineages. In this context, genetic tools have been extensively used in the past 20 years. Three important issues appear to have emerged from such studies. First, the study of NIS has revealed unexpected cryptic diversity in what had previously been assumed homogeneous entities. Second, there has been surprisingly little evidence of strong founder events accompanying marine introductions, a pattern possibly driven by large propagule loads. Third, the evolutionary processes leading to successful invasion have been difficult to ascertain due to faint genetic signals. Here we explore the potential of novel tools associated with high-throughput sequencing (HTS) to address these still pressing issues. Dramatic increase in the number of loci accessible via HTS has the potential to radically increase the power of analyses aimed at species delineation, exploring the population genomic consequences of range expansions, and examining evolutionary processes such as admixture, introgression, and adaptation. Nevertheless, the value of this new wealth of genomic data will ultimately depend on the ability to couple it with expanded "traditional" efforts, including exhaustive sampling of marine populations over large geographic scales, integrated taxonomic analyses, and population level exploration of quantitative trait differentiation through common-garden and other laboratory experiments.展开更多
For the geometry characteristics of open free-form surfaces,it is hard to consider global interference during the planning of feasible domains.Therefore,the optimal kinematic orientation of tool axis will no longer be...For the geometry characteristics of open free-form surfaces,it is hard to consider global interference during the planning of feasible domains.Therefore,the optimal kinematic orientation of tool axis will no longer be confined to the boundary of feasible domains.In this paper,according to the principle demanding that the tool should be fitted to a surface as close as possible and relevant processing parameters,a feasible domain of tool orientation for each cutter contact is planned in the local feed coordinates system.Then,these feasible domains of the tool orientation are transformed into the same coordinates system of the machine tool by the inverse kinematics transformation.The linear equations based feasible domain method and Rosen gradient projection algorithm are used to improve the optimization process in precision and efficiency of the algorithm.It constructs the variation of tool orientation optimization model and ensures the smoothness of tool orientation globally.Simulation and analysis of examples show that the proposed method has good kinematics performance and greatly improves the efficiency.展开更多
文摘The historic centres revitalization addresses the challenges related to the preservation of fundamental heritage values. At a time, when everyone looks with concern to our cities' future, it is important to reflect on the received heritage, seeking the most appropriate answers to the planning of the historic centres. These fabrics are reference places in the urban space, due to their role of memorial testimony and of generators of cultural and economic dynamics. However, often times, inherited urban fabrics are affected by the limitations of the heritage policies which, for being too general and based on theoretical and abstract frameworks, have difficulty incorporating the characteristics of each area and neglect the formulation of specific criteria and intervention methods. The purpose of this paper is to provide a comparative reading of the levels of urban renewal allowed by the planning tools. This study chooses two historic centers in Portugal: Oporto and Guimarfies historic centres (World Heritage Sites since 1996 and 2001, respectively, and were the last to get this classification in Portugal). This reflection is a contribution to peer trends and raise the discussion on the role that the different heritage policies have to the revitalization of the historic centres.
文摘In CNC machining, two essential components decide the accuracy and machining time for a sculptured surface: one is the step-size interval, the other is the tool-path interval. Due to the limitation of the conventional method for calculating the tool-path interval, it cannot satisfy the machining requirement for high-speed and high-resolution machining. Accordingly, for high-speed and high-resolution machining, the current study proposes a new tool-path interval algorithm, plus a variable step-size algorithm for NURBS. Furthermore, a new type cutter, which can improve the cutting efficiency, is investigated in the paper. The transversal equation of the torus cutter onto the flat plan is given in this paper. The tool-path interval is calculated with the transversal equation and the proposed algorithm. The illustrated example shows that the redundant tool paths can be reduced because an accurate tool-path interval could be calculated.
文摘Computational fluid dynamics(CFD) has recently emerged as an effective tool for the investigation of the hydraulic parameters and efficiency of tray towers.The computation domain was established for two types of oriented valves within a tray and meshed into two parts with different grid types and sizes.The volume fraction correlation concerning inter-phase momentum transfer source was fitted based on experimental data,and built in UDF for simulation.The flow pattern of oriented valve tray under different operating conditions was simulated under Eulerian-Eulerian framework with realizable k-ε model.The predicted liquid height from CFD simulation was in good agreement with the results of pressure drop and volume fraction correlations.Meanwhile,the velocity distribution and volume fraction of the two phases were demonstrated and analyzed,which are useful in design and analysis of the column trays.
基金Funded by the Doctorate Degree Program Foundation of the Ministry of Education (No. 2000061120)
文摘The methodology of 5-axis cutter selection to avert collision for free-form surface machining by flat-end cutters is presented. The combination of different cutters is adopt aiming at short machining time and high precision. The optimal small cutter is determined based on the geometric information of the points where a cutter most probably collide with the machined surface. Several larger cutters are selected to machine the surface in order to find the interference-free area. The difference of machining time for this area between the optimal small cutter and the large cutters is calculated. The functional relationship between the machining time and the radius of a cutter is established, by which the optimal number of cutters is obtained. The combination of cutters, which possesses the minimum overall machining time, is selected as the optimal cutter sizes. A case study has demonstrated the validity of the proposed methodology and algorithms.
文摘Nowadays, urban design faces complex demands. It has become a necessity to negotiate between stakeholder objectives, the expectations of citizens and the demands of planning. It is desirable to involve the stakeholders and citizens from an early stage in the planning process to enable their different viewpoints to be successfully expressed and comprehended. Therefore, the basic aim of the study was how the MR (mixed reality) application is designed to encourage and improve communication on urban design among stakeholders and citizens? In this paper, we discuss new approaches to visualize urban building and environment alternatives to different stakeholders and provide them with tools to explore different approaches to urban planning in order to support citizen's participation in urban planning with augmented and mixed reality. The major finding of the study is that learning "how these participatory technologies may help build a community of practice around an urban project". And throughout the different experiences, we can learn to assist towards development of a methodology to use the mixed reality as a simulation tool in the enhancement of collaborative interaction in real-Egyptian project. So, we can determine a number of recommendations to deal with new participatory design tools for urban planning projects.
文摘In this paper, the authors establish the Amalab-integrated operation management system (A-IOMS) as a new way to carry out software development and monitor business processes. This new system puts the previously constructed the Amalab-project planning navigation system (A-PPNS) to work throughout the entire organization. The A-IOMS has several key elements. Specifically, the authors have constructed: (1) a Hi-reliability estimation system diagnostic tool that pinpoints problems with software development estimates and offers a prescription for resolving them; (2) a QA table map that allows for an immediate, thorough, and consistent quality assurance process; (3) a system for sharing software development schedules throughout the organization; and (4) a technological asset completion reporting system for passing down and cultivating software development technologies and strategically expanding them. The authors verified the effectiveness of the A-IOMS at company A, a systems integration company, and the given outcomes were obtained.
文摘The lack of care related to maintenance management is directly linked to the absence of plans for maintenance of buildings. Because of that, there is a big incidence of building accidents caused by the negligence of managers and the lack of investment. The research has shown that, although building inspection is a consolidated building maintenance tool, managers do not prepare their building maintenance plan, nor use building inspection as a tool, leading the buildings to the premature obsolescence. The research calls attention to the building inspection technique that can be used to evaluate building maintenance and conservation. It is also a tool for analysis and investment planning based on actions to solve failures and anomalies that might come out during the building inspection. Those failures and anomalies are classified according to their degree of risk, determining the technical priorities of the investment adjustment in the maintenance plan. The paper presents a risk analysis methodology which classifies inspect elements in a building, determining the priority order of services to be executed on a scale from minimum risk (1) to imminent risk (5). The method shows a tool for building inspection, and it serves as a guideline for building maintenance interventions.
文摘The main purpose of this paper is to analyze the necessity of a Geographical Observatory of Atmospheric Pollution (GEOAP) in the Greek territory. The analysis performed is mainly focused on the benefits of the future function of the GEOAP to the environmental planning of the country and it could also provide an environmental management tool for the whole region. Measuring and mapping the pollution data and at the same time performing the geographical analysis of the complexity and the characteristics of natural and human environment can be useful tool in observation, management, and planning of the environmental policy of the country.
文摘Strategic planning is one of the most important management tools for organizational decision making. The nuclear area represents a segment of energy production used by many countries in America, Europe and Asia. It is known that in the future nuclear energy can be a major exit to the global energy crisis. The aim of this research was to use the BSC (Balanced Scorecard) as a strategic tool for decision making in a teaching and research institution of the nuclear area--IPEN (Nuclear and Energy Research Institute), located in the city of Sao Paulo, which belongs to the CNEN (National Nuclear Energy Commission) in Brazil. The methodology used in this academic doctoral study was a case study, which considered the period of research from December 2012 to December 2015. The main results expected from this case study are: the improvement of information flow, the view, the increased visibility of an organization providing education and especially research in relation to published works, increased interaction among IPEN and the main global research institutes and centers, increasing academic production of technical articles, indicator improvement, improving the monitoring of management actions, among others. Given the expected results one can conclude that this study will be of great value to the IPEN and also for the Brazilian energy sector, as it will allow and contribute to the dissemination and demystification of nuclear power as an energy source of mankind, its peaceful applications and for the management activity of knowledge and innovation production in the nuclear area of IPEN.
文摘This research is a development in management information system (MIS) planning based on operation analysis and development according to concurrent engineering approach and reestablishment of database management. According to our case study industry, such industry currently used traditional network systems such as LAN, and "Bus Network" Network Topology. Client/Server distributed computing has a problem with database management in data redundancy, data inconsistency, and data independency. For Network Topology, Bus Network has problem with multitasking since the network are able to handle only a set of data at a time so the traffic problem will occur when multiple users request for the service. Thus, such condition is inconsistent with concurrent engineering which must be able to access the data simultaneously. As a consequence, this study develops a network system, network system of working system, using LAN and "Star Network" network topology. The file server processing distributed is an application while database is stored in host computer or file server but the data will be processed in users' computer. When the user needs to access the data, file server will send it to the user and the user can further analysis or manage such data in the user computer, so called "Hierarchical Database Model". Hierarchical database structure is easily developed like general organization command structure with different level of responsibility. In details, the data level in the database is divided into three levels including DBI, DB2, and DB3, so development of simultaneously systemic flow and access of various critical data is performed in parallel. Furthermore, this is consistent with access of all three data levels including: Level 1 is overall dataflow of both inside and outside the organization; Level 2 is dataflow of each division in the organization; and Level 3 is dataflow of subunit in each division in the organization. After systemize flow and access of data with concurrent engineering as mentioned, it provided optimal efficiency in the whole production system management reducing loss in the whole system of the organization
基金supported by the National Natural Science Foundation of China (Grant No. 51075054)the National Basic Research Program of China ("973" Program) (Grant Nos. 2005CB726100 and 2011CB706800)the Fundamental Research Funds for the Central Universities (Grant No. DUT10ZD205)
文摘The cutter runout effect has significant influence on the shape of cutter swept surface and the machining surface quality. Hence,it is necessary to integrate the cutter runout effect in cutter swept surface modeling,geometric error prediction and tool path optimization for five-axis flank machining. In this paper,an envelope surface model considering cutter runout effect is first established,and geometric errors induced by runout effect are derived based on the relative motion analysis between the cutter and part in machining. In the model,the cutter runout is defined by four parameters,including inclination angle,location angle,offset value and the length of cutter axis. Then the runout parameters are integrated into the rotation surface of each cutting edge that is used to form the final cutter envelope surface for the five-axis machining process. Thus,the final resulting geometric errors of the machined surface induced by cutter runout can be obtained through computing the deviations from the nominal cutter swept surface. To reduce these errors,an iterative least square method is used to optimize the tool paths for five-axis flank machining. Finally,a validation example is given for a specific ruled surface. Results show the effectiveness and feasibility of the analytical model of geometric errors induced by cutter runout,and also show that the geometric errors can be reduced significantly using the proposed tool path planning method.
基金supported by the National Basic Research Program of China ("973" Program) (Grant No. 2011CB706800)the National Natural Science Foundation of China (Grant No. 50835004)the National Funds for Distinguished Young Scientists of China (Grant No. 51025518)
文摘Traditional five-axis tool path planning methods mostly focus on differential geometric characteristics between the cutter and the workpiece surface to increase the material removal rate(i.e.,by minimizing path length,improving curvature matching,maximizing local cutting width,etc.) . However,material removal rate is not only related to geometric conditions such as the local cutting width,but also constrained by feeding speed as well as the motion capacity of the five-axis machine. This research integrates machine tool kinematics and cutter-workpiece contact kinematics to present a general kinematical model for five-axis machining process. Major steps of the proposed method include:(1) to establish the forward kinematical relationship between the motion of the machine tool axes and the cutter contact point;(2) to establish a tool path optimization model for high material removal rate based on both differential geometrical property and the contact kinematics between the cutter and workpiece;(3) to convert cutter orientation and cutting direction optimization problem into a concave quadratic planning(QP) model. Tool path will finally be generated from the underlying optimal cutting direction field. Through solving the time-optimal trajectory generation problem and machining experiment,we demonstrate the validity and effectiveness of the proposed method.
文摘The expanding scale and increasing rate of marine biological invasions have been documented since the early 20th century. Besides their global ecological and economic impacts, non-indigenous species (NIS) also have attracted much attention as opportunities to explore important eco-evolutionary processes such as rapid adaptation, long-distance dispersal and range expansion, and secondary contacts between divergent evolutionary lineages. In this context, genetic tools have been extensively used in the past 20 years. Three important issues appear to have emerged from such studies. First, the study of NIS has revealed unexpected cryptic diversity in what had previously been assumed homogeneous entities. Second, there has been surprisingly little evidence of strong founder events accompanying marine introductions, a pattern possibly driven by large propagule loads. Third, the evolutionary processes leading to successful invasion have been difficult to ascertain due to faint genetic signals. Here we explore the potential of novel tools associated with high-throughput sequencing (HTS) to address these still pressing issues. Dramatic increase in the number of loci accessible via HTS has the potential to radically increase the power of analyses aimed at species delineation, exploring the population genomic consequences of range expansions, and examining evolutionary processes such as admixture, introgression, and adaptation. Nevertheless, the value of this new wealth of genomic data will ultimately depend on the ability to couple it with expanded "traditional" efforts, including exhaustive sampling of marine populations over large geographic scales, integrated taxonomic analyses, and population level exploration of quantitative trait differentiation through common-garden and other laboratory experiments.
基金supported by the National Key Basic Research Project of China under Grant No.2011CB302400the National Natural Science Foundation of China under Grant Nos.50975274 and 50975495
文摘For the geometry characteristics of open free-form surfaces,it is hard to consider global interference during the planning of feasible domains.Therefore,the optimal kinematic orientation of tool axis will no longer be confined to the boundary of feasible domains.In this paper,according to the principle demanding that the tool should be fitted to a surface as close as possible and relevant processing parameters,a feasible domain of tool orientation for each cutter contact is planned in the local feed coordinates system.Then,these feasible domains of the tool orientation are transformed into the same coordinates system of the machine tool by the inverse kinematics transformation.The linear equations based feasible domain method and Rosen gradient projection algorithm are used to improve the optimization process in precision and efficiency of the algorithm.It constructs the variation of tool orientation optimization model and ensures the smoothness of tool orientation globally.Simulation and analysis of examples show that the proposed method has good kinematics performance and greatly improves the efficiency.