Laminated carbon fiber clothes were infiltrated to prepare carbon fiber reinforced pyrolytic carbon （C/C） using isothermal chemical vapor infiltration （CVI）. The bending fatigue behavior of the infiltrated C/C com...Laminated carbon fiber clothes were infiltrated to prepare carbon fiber reinforced pyrolytic carbon （C/C） using isothermal chemical vapor infiltration （CVI）. The bending fatigue behavior of the infiltrated C/C composites was tested under two different stress levels. The residual strength and modulus of all fatigued samples were tested to investigate the effect of maximum stress level on fatigue behavior of C/C composites. The microstructure and damage mechanism were also investigated. The results showed that the residual strength and modulus of fatigued samples were improved. High stress level is more effective to increase the modulus. And for the increase of flexural strength, high stress level is more effective only in low cycles. The fatigue loading weakens the bonding between the matrix and fiber, and then affects the damage propagation pathway, and increases the energy consumption. So the properties of C/C composites are improved.展开更多
Based on the preferential continuation method proposed by Pawlowski （1995）, we propose a method and procedure for gravity anomaly separation with the preferential upward continuation operator in the case that the va...Based on the preferential continuation method proposed by Pawlowski （1995）, we propose a method and procedure for gravity anomaly separation with the preferential upward continuation operator in the case that the various sources are uncorrelated with one another and the continuation height is enough large. We also present a method for estimating optimum upward-continuation height, based on analyzing the characteristics of the preferential upward continuation operators of a synthesized gravity anomaly varying with different continuation heights. The method is tested on the raw Bouguer gravity data over an iron deposit. The result shows that the method separates the data into regional anomaly and residual anomaly efficiently and clearly.展开更多
The relation between microscopic properties (e.g., layer thickness, easy axis orientation) and the macroscopic magnetic properties such as remanent magnetization of the ferromagnetic multilayer system is investigated ...The relation between microscopic properties (e.g., layer thickness, easy axis orientation) and the macroscopic magnetic properties such as remanent magnetization of the ferromagnetic multilayer system is investigated based on a simple micromagnet approach. We concentrate on a multilayer design with periodic boundary condition, where alternating soft/hard layers build a nanostructured multilayer. For any easy axis direction in the soft and hard layers a simple explicit expression of remanence of the system has been derived analytically. We find that the remanence clearly depends on the thickness of the soft magnetic layer and is nearly independent of the thickness of hard magnetic layer. On the other hand, the remanence increases upon reducing the angle enclosed by the saturation magnetization and the easy axis directions of soft magnetic layer. However, it is unsensitive to the easy axis direction of hard magnetic layer, but there exists a maximum remanence for a certain easy axis direction of hard magnetic layer.展开更多
Logging residue can be defined as any form of wood, which under the highest stage of technological development could be used in manufacturing but is left in the forest during logging. Lumber production from logging re...Logging residue can be defined as any form of wood, which under the highest stage of technological development could be used in manufacturing but is left in the forest during logging. Lumber production from logging residues of a previous logging activity by a timber firm was undertaken with the objective of determining the suitability of utilizing buttressed-stumps as raw material for the timber industry. A horizontal mobile bandsaw machine was used to process the buttressed-stumps into lumber. The machine was characterized by a thin-kerr sawing technology （kerf-width 1.6 mm） compared to the conventional bandsaw machines of kerr-widths ranging from 3.0-4.5 mm. Lumber value and volume yields, fuel consumption rate, frequency of tool replacement and lumber production rate were assessed. Results indicated that there is the potential to increase timber production from logging residues by utilizing buttressed-stumps. Lumber value and volume yields of eight timber species investigated in this study ranged from 5%-31% and 34%-54% respectively. Fuel consumption rate which increased with increasing wood density, ranged from 5-14.5 liters/m3 of lumber produced. Frequency of saw replacement increased with increasing wood density. The number of saws required to produce one cubic meter of lumber, ranged from 1 to 7. Lumber production rate ranged from 0.10-0.38 m3/hour, increasing with decreasing wood density.展开更多
The main focus of this paper is to investigate the influence of hygrothermal aging on tensile strength of epoxy resin matrix composites.Firstly,tests of water absorption and moisture induced tensile strength degradati...The main focus of this paper is to investigate the influence of hygrothermal aging on tensile strength of epoxy resin matrix composites.Firstly,tests of water absorption and moisture induced tensile strength degradation of glass fiber reinforced polymer(GFRP)are conducted.Results show that the moisture absorption behavior of the GFRP follows the Fick’s law,and its tensile strength retention decreases notably in the early hygrothermal aging stage and then gradually approaches a constant.Then,microscale longitudinal and transverse strength prediction models for unidirectional fiber reinforced composites are proposed.They are moisture concentration dependent and reflect the inherent probability of failures of fiber and matrix(or fiber/matrix interface).The moisture diffusing analysis demostrates that the proposed models can predict degradation of tensile strength of epoxy resin matrix composites undergoing different hygrothermal durations.The proposed models are validated by the experiments of hygrothermal residual strength of the GFRP mentioned above.展开更多
A SOFC （solid oxide fuel cell） cycle running on natural gas was integrated with a ST （steam turbine） cycle. The fuel is desulfurized and pre-reformed before entering the SOFC. A burner was used to combust the rema...A SOFC （solid oxide fuel cell） cycle running on natural gas was integrated with a ST （steam turbine） cycle. The fuel is desulfurized and pre-reformed before entering the SOFC. A burner was used to combust the remaining fuel after the SOFC stacks. The off-gases from the burner were used to produce steam in a HRSG （heat recovery steam generator）. The bottoming steam cycle was modeled with two configurations： （1） a simple single pressure level and （2） a dual pressure level with both a reheat and a pre-heater. The SOFC stacks in the present SOFC-ST hybrid cycles were not pressurized. The dual pressure configuration steam cycle combined with SOFC cycle （SOFC-ST） was new and has not been studied previously. In each of the configuration, a hybrid recuperator was used to recovery the remaining energy of the off-gases after the HRSG. Thus, four different plants system setups were compared to each other to reveal the most superior concept with respect to plant efficiency and power. It was found that in order to increase the plant efficiency considerably, it was enough to use a single pressure with a hybrid recuperator instead of a dual pressure Rankine cycle.展开更多
The design concept of high excess pressure cockpit has been proposed as a solution to solve the ergonomics problems caused by cockpit environment.To address the contradiction among mass,economy,maneuverability and env...The design concept of high excess pressure cockpit has been proposed as a solution to solve the ergonomics problems caused by cockpit environment.To address the contradiction among mass,economy,maneuverability and environment ergonomics,considering the composite advantages of high strength and lightweight,the feasibility analysis concept of high excess pressure cockpit based on material substitution is proposed in the paper.Based on the strain energy analysis on finite element model,the iteration design method of equal stiffness and lightening effect analysis on material substitution are presented,The weight reduction effect after material substitution can be evaluated intuitively by using equal stiffness curve.The calculation result of cockpit indicates that the lightening effect can reach 35.09%.Because of the complexity of cockpit design,bi-level optimization method is proposed and performed by means of the First-Order Radio algorithm.The research shows that the method can achieve good result.The feasibility of high excess pressure cockpit is studied from the aspect of the relationship between excess pressure and mass,and the research demonstrates that,due to the utilization of T300/4211 in place of 6061 alloy,the excess pressure of cockpit increases from 35 to 45 kPa,a 28.57%increase,while the cockpit mass is decreased by 12.56%.Thus,the contradiction among mass,economy and environment ergonomics can be coordinated,which can provide a reference for the design of high excess pressure cockpit.展开更多
基金Projects(50832004,51105132)supported by the National Natural Science Foundation of ChinaProject(B08040)supported by Program of Introducing Talents of Discipline to Universities,China
文摘Laminated carbon fiber clothes were infiltrated to prepare carbon fiber reinforced pyrolytic carbon （C/C） using isothermal chemical vapor infiltration （CVI）. The bending fatigue behavior of the infiltrated C/C composites was tested under two different stress levels. The residual strength and modulus of all fatigued samples were tested to investigate the effect of maximum stress level on fatigue behavior of C/C composites. The microstructure and damage mechanism were also investigated. The results showed that the residual strength and modulus of fatigued samples were improved. High stress level is more effective to increase the modulus. And for the increase of flexural strength, high stress level is more effective only in low cycles. The fatigue loading weakens the bonding between the matrix and fiber, and then affects the damage propagation pathway, and increases the energy consumption. So the properties of C/C composites are improved.
基金supported jointly by projects of the 863 Program (Grant Nos.2006AA06Z111,2006AA06A201-3,and 20060109A1002-0201-03)
文摘Based on the preferential continuation method proposed by Pawlowski （1995）, we propose a method and procedure for gravity anomaly separation with the preferential upward continuation operator in the case that the various sources are uncorrelated with one another and the continuation height is enough large. We also present a method for estimating optimum upward-continuation height, based on analyzing the characteristics of the preferential upward continuation operators of a synthesized gravity anomaly varying with different continuation heights. The method is tested on the raw Bouguer gravity data over an iron deposit. The result shows that the method separates the data into regional anomaly and residual anomaly efficiently and clearly.
文摘The relation between microscopic properties (e.g., layer thickness, easy axis orientation) and the macroscopic magnetic properties such as remanent magnetization of the ferromagnetic multilayer system is investigated based on a simple micromagnet approach. We concentrate on a multilayer design with periodic boundary condition, where alternating soft/hard layers build a nanostructured multilayer. For any easy axis direction in the soft and hard layers a simple explicit expression of remanence of the system has been derived analytically. We find that the remanence clearly depends on the thickness of the soft magnetic layer and is nearly independent of the thickness of hard magnetic layer. On the other hand, the remanence increases upon reducing the angle enclosed by the saturation magnetization and the easy axis directions of soft magnetic layer. However, it is unsensitive to the easy axis direction of hard magnetic layer, but there exists a maximum remanence for a certain easy axis direction of hard magnetic layer.
文摘Logging residue can be defined as any form of wood, which under the highest stage of technological development could be used in manufacturing but is left in the forest during logging. Lumber production from logging residues of a previous logging activity by a timber firm was undertaken with the objective of determining the suitability of utilizing buttressed-stumps as raw material for the timber industry. A horizontal mobile bandsaw machine was used to process the buttressed-stumps into lumber. The machine was characterized by a thin-kerr sawing technology （kerf-width 1.6 mm） compared to the conventional bandsaw machines of kerr-widths ranging from 3.0-4.5 mm. Lumber value and volume yields, fuel consumption rate, frequency of tool replacement and lumber production rate were assessed. Results indicated that there is the potential to increase timber production from logging residues by utilizing buttressed-stumps. Lumber value and volume yields of eight timber species investigated in this study ranged from 5%-31% and 34%-54% respectively. Fuel consumption rate which increased with increasing wood density, ranged from 5-14.5 liters/m3 of lumber produced. Frequency of saw replacement increased with increasing wood density. The number of saws required to produce one cubic meter of lumber, ranged from 1 to 7. Lumber production rate ranged from 0.10-0.38 m3/hour, increasing with decreasing wood density.
基金the National Natural Science Foundation of China(No.11872205)the State Key Laboratory Open Fund(No.MCMS-E-0221Y02)the Priority Academic Program Development of Jiangsu Higher Education Institutions。
文摘The main focus of this paper is to investigate the influence of hygrothermal aging on tensile strength of epoxy resin matrix composites.Firstly,tests of water absorption and moisture induced tensile strength degradation of glass fiber reinforced polymer(GFRP)are conducted.Results show that the moisture absorption behavior of the GFRP follows the Fick’s law,and its tensile strength retention decreases notably in the early hygrothermal aging stage and then gradually approaches a constant.Then,microscale longitudinal and transverse strength prediction models for unidirectional fiber reinforced composites are proposed.They are moisture concentration dependent and reflect the inherent probability of failures of fiber and matrix(or fiber/matrix interface).The moisture diffusing analysis demostrates that the proposed models can predict degradation of tensile strength of epoxy resin matrix composites undergoing different hygrothermal durations.The proposed models are validated by the experiments of hygrothermal residual strength of the GFRP mentioned above.
文摘A SOFC （solid oxide fuel cell） cycle running on natural gas was integrated with a ST （steam turbine） cycle. The fuel is desulfurized and pre-reformed before entering the SOFC. A burner was used to combust the remaining fuel after the SOFC stacks. The off-gases from the burner were used to produce steam in a HRSG （heat recovery steam generator）. The bottoming steam cycle was modeled with two configurations： （1） a simple single pressure level and （2） a dual pressure level with both a reheat and a pre-heater. The SOFC stacks in the present SOFC-ST hybrid cycles were not pressurized. The dual pressure configuration steam cycle combined with SOFC cycle （SOFC-ST） was new and has not been studied previously. In each of the configuration, a hybrid recuperator was used to recovery the remaining energy of the off-gases after the HRSG. Thus, four different plants system setups were compared to each other to reveal the most superior concept with respect to plant efficiency and power. It was found that in order to increase the plant efficiency considerably, it was enough to use a single pressure with a hybrid recuperator instead of a dual pressure Rankine cycle.
文摘The design concept of high excess pressure cockpit has been proposed as a solution to solve the ergonomics problems caused by cockpit environment.To address the contradiction among mass,economy,maneuverability and environment ergonomics,considering the composite advantages of high strength and lightweight,the feasibility analysis concept of high excess pressure cockpit based on material substitution is proposed in the paper.Based on the strain energy analysis on finite element model,the iteration design method of equal stiffness and lightening effect analysis on material substitution are presented,The weight reduction effect after material substitution can be evaluated intuitively by using equal stiffness curve.The calculation result of cockpit indicates that the lightening effect can reach 35.09%.Because of the complexity of cockpit design,bi-level optimization method is proposed and performed by means of the First-Order Radio algorithm.The research shows that the method can achieve good result.The feasibility of high excess pressure cockpit is studied from the aspect of the relationship between excess pressure and mass,and the research demonstrates that,due to the utilization of T300/4211 in place of 6061 alloy,the excess pressure of cockpit increases from 35 to 45 kPa,a 28.57%increase,while the cockpit mass is decreased by 12.56%.Thus,the contradiction among mass,economy and environment ergonomics can be coordinated,which can provide a reference for the design of high excess pressure cockpit.
