Vibration fatigue is one of the main failure modes of blade.The vibration fatigue life of blade is scattered caused by manufacture error,material property dispersion and external excitation randomness.A new vibration ...Vibration fatigue is one of the main failure modes of blade.The vibration fatigue life of blade is scattered caused by manufacture error,material property dispersion and external excitation randomness.A new vibration fatigue probabilistic life prediction model(VFPLPM)and a prediction method are proposed in this paper.Firstly,as one-dimensional volumetric method(ODVM)only considers the principle calculation direction,a three-dimensional space vector volumetric method(TSVVM)is proposed to improve fatigue life prediction accuracy for actual threedimensional engineering structure.Secondly,based on the two volumetric methods(ODVM and TSVVM),the material C-P-S-N fatigue curve model(CFCM)and the maximum entropy quantile function model(MEQFM),VFPLPM is established to predict the vibration fatigue probabilistic life of blade.The VFPLPM is combined with maximum stress method(MSM),ODVM and TSVVM to estimate vibration fatigue probabilistic life of blade simulator by finite element simulation,and is verified by vibration fatigue test.The results show that all of the three methods can predict the vibration fatigue probabilistic life of blade simulator well.VFPLPM &TSVVM method has the highest computational accuracy for considering stress gradient effect not only in the principle calculation direction but also in other space vector directions.展开更多
Many Middle Asia countries declaring their independence after the splitting of the Soviet Union, cannot meet the economical and social needs of their citizens by falling much behind of the era in terms of industry des...Many Middle Asia countries declaring their independence after the splitting of the Soviet Union, cannot meet the economical and social needs of their citizens by falling much behind of the era in terms of industry despite the natural wealth they have. In addition to all these, the problems in the ruling class and the chaos environment have resulted in the migration of many people to alternative living spaces. These migrations have affected labor market both positively and negatively besides the social life. The labor demand increased by the entrance of the immigrants into the market has affected the employee wages and also this situation has affected the life standards of the citizens In this study, the migration that took place in the countries established after the splitting of the Soviet Union, forming one of the two poles of the world before the cold war, and the effects of this migration on the labor market have been analyzed considering previous studies on the subject. The studies carried out on this subject have yielded various results according to the area in which it is carried out, the time interval it includes, and the period＇s structure For this reason, the points of views on the subject are compared by making a long literature review展开更多
The use of composite materials in aerospace engineering is ever increasing. Properties such as low weight, high performance, high stiffness and the ability for it to be tailored specifically for different structural u...The use of composite materials in aerospace engineering is ever increasing. Properties such as low weight, high performance, high stiffness and the ability for it to be tailored specifically for different structural uses has increased its importance in recent years. Specific experimental/numerical activities were developed in the last decade at the aerospace department of Polito and are under consideration in recent years regarding the analysis of fatigue behavior of composite/metallic structural samples under cyclic loading condition. A review of the main significant results connected to three case-studies is presented in the paper. The first is related to the definition and analysis of innovative joint for composite high aspect ratio aircraft structures. The modular design oriented to limit component dimensions for transportability requires the presence of a removable joints able to overcome the typical low bearing failure level of composite pin-loaded joint under static and fatigue loading distribution according to airworthiness requirements. The static experiments demonstrate the consistency of the proposed advanced joint configuration that postpones the joint failure to high load level according to the structural requirements. The cyclic loading phase takes as reference point the failure load of the initial configuration and defines a loading cycle with a maximum higher than the failure load of the initial configuration. The fatigue behavior of the advanced joint also demonstrates a substantial consistency with expected duration of 1 e6 cycles as required by the structural design for operating reasons. Specific indication on fatigue limit with respect to critical amplitude is reported. The second is related to the presence of specific damaged situation in thin-walled fiat/stiffened composite plate. Stiffened configurations are frequently used to increase buckling load level. Unexpected events on solid/stiffened composite panels can introduce a certain level of damage, typically delamination, that can cause reduction in buckling design level and reduction in global strength. The presence of cyclic load and fatigue effect can have an important consequence on damage propagation and structural integrity. The damaged area determined by the skin-stiffener de-bonding of a certain dimension is investigated under static compression and cyclic compression. Local buckling of damaged area is determined and pointed out by tests in uniaxial compression. The experimental static behavior points out the presence of a snap-effect during loading and un-loading. Fatigue loading configuration is applied in the range of post-critical local configuration considered as the most effective situation. Preliminary fatigue results are presented and discussed. The third is related to preliminary investigation on the effect of fatigue life reduction of 2024 AI alloy in corrosive （exfoliation） environment. The effect of corrosion is taken into consideration introducing specific concentration factors into the life estimation relationship. Differences between fatigue in prior corroded specimens and fatigue in presence of corrosive environment are emphasized. No crack propagation is considered. Related concentration factors are derived and compared by the few experimental results in order to define some guidelines for design process and to improve aircraft better evaluation of component structural integrity in operative situations. A preliminary approach is presented in the paper in order to correctly identify the contribution of corrosive environment in coupled fatigue loading phase. The results are discussed and future improvements are suggested.展开更多
The aim of this study is to portray and explore the variety of social actors depicted visually along the pages of the intermediate level ELT coursebooks that are published locally （by British and American publishers...The aim of this study is to portray and explore the variety of social actors depicted visually along the pages of the intermediate level ELT coursebooks that are published locally （by British and American publishers） and marketed globally （mostly to the EFL contexts）. For this, a thorough photo-ethnographic exploration of the visuals supported by the inventory of ＂social actor interaction network＂ is employed. In the field of Coursebook Analysis, visuals have attracted limited attention despite marking asocio-semiotically rich discursive field. In fact, the semiotic labor division between the ＂word＂ and the ＂image＂ in representing and reconstructing （simulating） the world, points to a gain on the part of the image as the brain is evolutionarily more experienced in processing visual information than processing verbal information. Therefore, images can appeal more directly to the sensory experience domains of the viewers via visual contact, evoking deeper consciousness. Acting as the prominent mediators of signification practice, visuals catalogue the representations and simulations of social-life viewed l^om a particular subject position associated with a particular set of norms, beliefs, and values. Hence, they position the viewers across dynamic loci of subjectivities in terms of social distance, relations, and interaction. As both reflections and reproductions of reality, images in the coursebooks have the potent to influence learners＇ perspectives of the world presenting them with readymade cognitive schemes. In order to reveal a comprehensive picture of the visually depicted social actors and the identity options made available through them, in this study the author focused on the peopled photos of the 6 popularly traded ELT coursebooks. The author investigated them regarding the relations of social distance, involvement, power and interaction formed between the depicted social actors and their viewers as well as the emergent practices of exclusion, role allocation, genericization, specification, assimilation, individualization, and categorization. The results show that the representational repertoires of the coursebooks contain disproportionately distributed visual depictions of social actors in terms of cultural orientation and gender. The ＂culturally different＂ are repeatedly pictured in assimilative ways as an aggregate of enumerable people, while the social actors of the reference group are usually pictured individually and with their own intended meaning.展开更多
The international movement of workers and the inflow/outflow of immigrants are increasing, the term immigrant communities which country in the world is more familiar. Also, the country that accumulated a history of im...The international movement of workers and the inflow/outflow of immigrants are increasing, the term immigrant communities which country in the world is more familiar. Also, the country that accumulated a history of immigration over decades have been promoted while continuously changing the integration policies for immigrants. The immigration into home country such as the married immigrant women, etc. is constantly increasing in South Korea that had a homogeneous culture. While, it is continued to the overseas movement of young people looking for opportunities in foreign rather than domestic. In South Korea, the multi-cultural families are increasing together with the immigration of foreign workers, the marriage immigrants, etc. in accordance with the globalization of capital and labor, and the multi-cultural society is being formed in accordance with the influx of alien culture and various religious. In this paper, it explored the trends and the future outlook for the multi-cultural workforce in these dimensions. Also, in a multi-cultural society, it suggested the implications and the future assignments for the new changes in the education ＆ training and the employment in order to improve the quality of life and to use as the production entities of multi-cultural workforce.展开更多
A nonlinear dynamical system is proposed as a qualitative mathematical model with the twofold aim to reasonably describe the force behavior in a fatiguing sub-maximal contraction and to be possibly employed in assessi...A nonlinear dynamical system is proposed as a qualitative mathematical model with the twofold aim to reasonably describe the force behavior in a fatiguing sub-maximal contraction and to be possibly employed in assessing muscular activation indexes. The model＇s properties are studied in terms of its equilibria and their stability properties and the existence of the fatigue equilibrium is ensured as the only system＇s attractor in the feasibility range of the parameters. Suitable mathematical indicators -- related to the dynamical properties of resilience and reactivity -- are introduced to characterize the asymptotic and the transient system＇s behavior. The practical impact of the analytical results is elucidated and a connection is established between the introduced mathematical indicators and muscle functionality indexes as rate of force development, task failure time and complete restore time. Experimental validation with handgrip force signal at high load and possible practical applications are also presented.展开更多
This paper uses empirical research conducted in Shanghai to answer these questions： What are the differences between the new generation of migrant workers and the previous generation of migrant workers？ What influen...This paper uses empirical research conducted in Shanghai to answer these questions： What are the differences between the new generation of migrant workers and the previous generation of migrant workers？ What influence do they have on China＇s politics？ Surveys have shown that the new generation of migrant workers put a greater emphasis on personal space and quality of life. They also have a greater awareness of their individual rights. Additionally, they have a stronger desire to assimilate into the city. The ratio of remittances in relation to income among the new generation of migrant workers has decreased signiflcandy while their local spending has increased. Overall, the new migrant workers demonstrate a stronger tendency towards permanent migration. Local citizenship based on the hukou （household registration ） system is facing a crisis of legitimacy. The unrest among the new generation of migrant workers is a mixture of Marx-type labor unrest and Polanyi-type labor unrest, but the unrest is ultimately directed towards the state. The result will be a rise in the politics of citizenship in China.展开更多
基金supported by the Aviation Science Foundation of China(No.20150252003)
文摘Vibration fatigue is one of the main failure modes of blade.The vibration fatigue life of blade is scattered caused by manufacture error,material property dispersion and external excitation randomness.A new vibration fatigue probabilistic life prediction model(VFPLPM)and a prediction method are proposed in this paper.Firstly,as one-dimensional volumetric method(ODVM)only considers the principle calculation direction,a three-dimensional space vector volumetric method(TSVVM)is proposed to improve fatigue life prediction accuracy for actual threedimensional engineering structure.Secondly,based on the two volumetric methods(ODVM and TSVVM),the material C-P-S-N fatigue curve model(CFCM)and the maximum entropy quantile function model(MEQFM),VFPLPM is established to predict the vibration fatigue probabilistic life of blade.The VFPLPM is combined with maximum stress method(MSM),ODVM and TSVVM to estimate vibration fatigue probabilistic life of blade simulator by finite element simulation,and is verified by vibration fatigue test.The results show that all of the three methods can predict the vibration fatigue probabilistic life of blade simulator well.VFPLPM &TSVVM method has the highest computational accuracy for considering stress gradient effect not only in the principle calculation direction but also in other space vector directions.
文摘Many Middle Asia countries declaring their independence after the splitting of the Soviet Union, cannot meet the economical and social needs of their citizens by falling much behind of the era in terms of industry despite the natural wealth they have. In addition to all these, the problems in the ruling class and the chaos environment have resulted in the migration of many people to alternative living spaces. These migrations have affected labor market both positively and negatively besides the social life. The labor demand increased by the entrance of the immigrants into the market has affected the employee wages and also this situation has affected the life standards of the citizens In this study, the migration that took place in the countries established after the splitting of the Soviet Union, forming one of the two poles of the world before the cold war, and the effects of this migration on the labor market have been analyzed considering previous studies on the subject. The studies carried out on this subject have yielded various results according to the area in which it is carried out, the time interval it includes, and the period＇s structure For this reason, the points of views on the subject are compared by making a long literature review
文摘The use of composite materials in aerospace engineering is ever increasing. Properties such as low weight, high performance, high stiffness and the ability for it to be tailored specifically for different structural uses has increased its importance in recent years. Specific experimental/numerical activities were developed in the last decade at the aerospace department of Polito and are under consideration in recent years regarding the analysis of fatigue behavior of composite/metallic structural samples under cyclic loading condition. A review of the main significant results connected to three case-studies is presented in the paper. The first is related to the definition and analysis of innovative joint for composite high aspect ratio aircraft structures. The modular design oriented to limit component dimensions for transportability requires the presence of a removable joints able to overcome the typical low bearing failure level of composite pin-loaded joint under static and fatigue loading distribution according to airworthiness requirements. The static experiments demonstrate the consistency of the proposed advanced joint configuration that postpones the joint failure to high load level according to the structural requirements. The cyclic loading phase takes as reference point the failure load of the initial configuration and defines a loading cycle with a maximum higher than the failure load of the initial configuration. The fatigue behavior of the advanced joint also demonstrates a substantial consistency with expected duration of 1 e6 cycles as required by the structural design for operating reasons. Specific indication on fatigue limit with respect to critical amplitude is reported. The second is related to the presence of specific damaged situation in thin-walled fiat/stiffened composite plate. Stiffened configurations are frequently used to increase buckling load level. Unexpected events on solid/stiffened composite panels can introduce a certain level of damage, typically delamination, that can cause reduction in buckling design level and reduction in global strength. The presence of cyclic load and fatigue effect can have an important consequence on damage propagation and structural integrity. The damaged area determined by the skin-stiffener de-bonding of a certain dimension is investigated under static compression and cyclic compression. Local buckling of damaged area is determined and pointed out by tests in uniaxial compression. The experimental static behavior points out the presence of a snap-effect during loading and un-loading. Fatigue loading configuration is applied in the range of post-critical local configuration considered as the most effective situation. Preliminary fatigue results are presented and discussed. The third is related to preliminary investigation on the effect of fatigue life reduction of 2024 AI alloy in corrosive （exfoliation） environment. The effect of corrosion is taken into consideration introducing specific concentration factors into the life estimation relationship. Differences between fatigue in prior corroded specimens and fatigue in presence of corrosive environment are emphasized. No crack propagation is considered. Related concentration factors are derived and compared by the few experimental results in order to define some guidelines for design process and to improve aircraft better evaluation of component structural integrity in operative situations. A preliminary approach is presented in the paper in order to correctly identify the contribution of corrosive environment in coupled fatigue loading phase. The results are discussed and future improvements are suggested.
文摘The aim of this study is to portray and explore the variety of social actors depicted visually along the pages of the intermediate level ELT coursebooks that are published locally （by British and American publishers） and marketed globally （mostly to the EFL contexts）. For this, a thorough photo-ethnographic exploration of the visuals supported by the inventory of ＂social actor interaction network＂ is employed. In the field of Coursebook Analysis, visuals have attracted limited attention despite marking asocio-semiotically rich discursive field. In fact, the semiotic labor division between the ＂word＂ and the ＂image＂ in representing and reconstructing （simulating） the world, points to a gain on the part of the image as the brain is evolutionarily more experienced in processing visual information than processing verbal information. Therefore, images can appeal more directly to the sensory experience domains of the viewers via visual contact, evoking deeper consciousness. Acting as the prominent mediators of signification practice, visuals catalogue the representations and simulations of social-life viewed l^om a particular subject position associated with a particular set of norms, beliefs, and values. Hence, they position the viewers across dynamic loci of subjectivities in terms of social distance, relations, and interaction. As both reflections and reproductions of reality, images in the coursebooks have the potent to influence learners＇ perspectives of the world presenting them with readymade cognitive schemes. In order to reveal a comprehensive picture of the visually depicted social actors and the identity options made available through them, in this study the author focused on the peopled photos of the 6 popularly traded ELT coursebooks. The author investigated them regarding the relations of social distance, involvement, power and interaction formed between the depicted social actors and their viewers as well as the emergent practices of exclusion, role allocation, genericization, specification, assimilation, individualization, and categorization. The results show that the representational repertoires of the coursebooks contain disproportionately distributed visual depictions of social actors in terms of cultural orientation and gender. The ＂culturally different＂ are repeatedly pictured in assimilative ways as an aggregate of enumerable people, while the social actors of the reference group are usually pictured individually and with their own intended meaning.
文摘The international movement of workers and the inflow/outflow of immigrants are increasing, the term immigrant communities which country in the world is more familiar. Also, the country that accumulated a history of immigration over decades have been promoted while continuously changing the integration policies for immigrants. The immigration into home country such as the married immigrant women, etc. is constantly increasing in South Korea that had a homogeneous culture. While, it is continued to the overseas movement of young people looking for opportunities in foreign rather than domestic. In South Korea, the multi-cultural families are increasing together with the immigration of foreign workers, the marriage immigrants, etc. in accordance with the globalization of capital and labor, and the multi-cultural society is being formed in accordance with the influx of alien culture and various religious. In this paper, it explored the trends and the future outlook for the multi-cultural workforce in these dimensions. Also, in a multi-cultural society, it suggested the implications and the future assignments for the new changes in the education ＆ training and the employment in order to improve the quality of life and to use as the production entities of multi-cultural workforce.
文摘A nonlinear dynamical system is proposed as a qualitative mathematical model with the twofold aim to reasonably describe the force behavior in a fatiguing sub-maximal contraction and to be possibly employed in assessing muscular activation indexes. The model＇s properties are studied in terms of its equilibria and their stability properties and the existence of the fatigue equilibrium is ensured as the only system＇s attractor in the feasibility range of the parameters. Suitable mathematical indicators -- related to the dynamical properties of resilience and reactivity -- are introduced to characterize the asymptotic and the transient system＇s behavior. The practical impact of the analytical results is elucidated and a connection is established between the introduced mathematical indicators and muscle functionality indexes as rate of force development, task failure time and complete restore time. Experimental validation with handgrip force signal at high load and possible practical applications are also presented.
文摘This paper uses empirical research conducted in Shanghai to answer these questions： What are the differences between the new generation of migrant workers and the previous generation of migrant workers？ What influence do they have on China＇s politics？ Surveys have shown that the new generation of migrant workers put a greater emphasis on personal space and quality of life. They also have a greater awareness of their individual rights. Additionally, they have a stronger desire to assimilate into the city. The ratio of remittances in relation to income among the new generation of migrant workers has decreased signiflcandy while their local spending has increased. Overall, the new migrant workers demonstrate a stronger tendency towards permanent migration. Local citizenship based on the hukou （household registration ） system is facing a crisis of legitimacy. The unrest among the new generation of migrant workers is a mixture of Marx-type labor unrest and Polanyi-type labor unrest, but the unrest is ultimately directed towards the state. The result will be a rise in the politics of citizenship in China.
